Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List the Northern Leopard Frog in the Western United States as Threatened

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R2-ES-2009-0030; 92210-1111-FY08-B2]

Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List the Northern Leopard Frog in the Western United States as Threatened

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Notice of 12-month petition finding.

SUMMARY:

We, the U.S. Fish and Wildlife Service, announce a 12-month finding on a petition to list the northern leopard frog (

Lithobates

(=

Rana

)

pipiens

) under the Endangered Species Act of 1973, as amended (Act). After review of the best scientific and commercial information, we find that listing the northern leopard frog is not warranted at this time. However, we ask the public to submit to us any new information that becomes available concerning threats to the northern leopard frog or its habitat at any time.

DATES:

The finding announced in this document was made on October 5, 2011.

ADDRESSES:

This finding is available on the Internet at

http://www.regulations.gov

at Docket Number FWS-R2-ES-2009-0030. Supporting documentation we used in preparing this finding is available for public inspection, by appointment, during normal business hours at the U.S. Fish and Wildlife Service, Arizona Ecological Services Office, 2321 West Royal Palm Road, Suite 103, Phoenix, AZ 85021. Please submit any new information, materials, comments, or questions concerning this finding to the above street address.

FOR FURTHER INFORMATION CONTACT:

Steven L. Spangle, Field Supervisor, Arizona Ecological Services Office (see

ADDRESSES

); by telephone at (602) 242-0210; or by facsimile at (602) 242-2513. If you use a telecommunications device for the deaf (TDD), please call the Federal Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Background

Section 4(b)(3)(B) of the Act (16 U.S.C. 1531

et seq.

), requires that, for any petition to revise the Federal Lists of Endangered and Threatened Wildlife and Plants that contains substantial scientific or commercial information that listing the species may be warranted, we make a finding within 12 months of the date of receipt of the petition. In our finding, we are required to determine if the petitioned action is: (a) Not warranted, (b) warranted, or (c) warranted, but the immediate proposal of a regulation implementing the petitioned action is precluded by other pending proposals to determine whether species are endangered or threatened, and expeditious progress is being made to add or remove qualified species from the Federal Lists of Endangered and Threatened Wildlife and Plants. Section 4(b)(3)(C) of the Act requires that we treat a petition for which the requested action is found to be warranted but precluded as though resubmitted on the date of such finding, that is, requiring a subsequent finding to be made within 12 months. We must publish these 12-month findings in the

Federal Register

.

Previous Federal Actions

On June 5, 2006, we received a petition from the Center for Native Ecosystems, Biodiversity Conservation Alliance, Defenders of Black Hills, Forest Guardians, Center for Biological Diversity, The Ark Initiative, Native Ecosystems Council, Rocky Mountain Clean Air Action, and Mr. Jeremy Nichols requesting that the northern leopard frog (

Lithobates

(=

Rana

)

pipiens

) occurring in the western United States (Arizona, California, Colorado, Idaho, Iowa, Minnesota, Missouri, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oregon, South Dakota, Texas, Utah, Washington, and Wyoming) be listed as a threatened distinct population segment (DPS) under the Act. The petition contained detailed information on the natural history, biology, current status, and distribution of the western population of the northern leopard frog. It also contained information on what the petitioners reported as potential threats to the western population of the northern leopard frog such as habitat loss and degradation, predation and competition by nonnative species, disease, water pollution, climate change, and other factors. We acknowledged the receipt of the petition in a letter to the petitioners dated August 7, 2006. That letter explained that we would not be able to address their petition at that time. The reason for this delay was that responding to court orders and settlement agreements for other listing actions required nearly all of our listing funding.

In reviewing the petition, there were two issues for which the Service requested clarification from the petitioners. We were petitioned to list the population west of the Mississippi River and the Great Lakes region in the United States and south of the international boundary between the United States and Canada. However, although Wisconsin is located west of the Great Lakes region, the petition map did not show Wisconsin as a part of the petition, and the status of the species is not mentioned in that State. Therefore, we requested that the petitioners clarify whether they intended to include or exclude Wisconsin from the petitioned DPS. We also sought clarification as to whether the petitioners were requesting that we review only the western U.S. population of the northern leopard frog as a DPS or if they were also requesting us to consider listing the entire species or a significant portion of the range of the species. The petitioners responded to our clarification request in a letter dated February 8, 2008, requesting we review whether Wisconsin should be included in the western U.S. population of the northern leopard frog. In addition, the petitioners clarified that, if we find that listing the western U.S. population of northern leopard frogs as a DPS is not warranted, we review whether listing the entire species is warranted because of threats in a significant portion of its range.

On July 1, 2009, we published our 90-day finding (74 FR 31389) that the petition presented substantial scientific information indicating that listing the western population of the northern leopard frog may be warranted, and we initiated a status review to determine if listing the species as a DPS or throughout all or a significant portion of its range is warranted. Our July 1, 2009, 90-day finding opened a 60-day period to send us information for our status review. On October 28, 2009, we reopened this information solicitation period for our status review for an additional 30 days, ending November 27, 2009 (74 FR 55525). This notice constitutes our 12-month finding on the February 8, 2008, petition to list the northern leopard frog.

Species Information

Below we provide information relevant to understanding the analysis of information pertaining to the five factors. See Rorabaugh (2005) for a more complete description of the distribution and life history of the northern leopard frog.

Taxonomy

The northern leopard frog is in the family Ranidae (Lannoo 2005, p. 371), the true frogs, and is one of about 28 species within the genus

Lithobates

(formerly

Rana

(Frost

et al.

2006, p. 10;

Frost

et al.

2008, pp. 7-8)) that occur in North America (Lannoo 2005, p. 371). For more than a century, nomenclatural and taxonomic confusion has surrounded members of the

Lithobates

(=

Rana

) complex (Moore 1944, p. 349; Pace 1974, pp. 11-16; Merrell 1977, pp. 1-2; Hillis

et al.

1983, p. 132 among others), and there is a wealth of literature from the late 1800s to present day that has attempted to accurately describe the different species and geographic variation within the complex. Until recently, all North American ranid frogs (frogs in the family Ranidae) were included within the single genus

Rana.

However, Frost

et al.

(2006, p. 10) placed most of these species into the genus

Lithobates.

This change is recognized by the Committee on Standard English and Scientific Names, which is the official names list of the American Society of Ichthyologists and Herpetologists, the Herpetologists' League, and the Society for the Study of Amphibians and Reptiles (Frost

et al.

2008, pp. 7-8). Accordingly, the Service also recognizes and accepts Frost

et al.'

s (2008)

Lithobates

classification.

Physical Description

The northern leopard frog is a slim, smooth-skinned green, brown, or sometimes yellow-green frog with webbed hind feet. The frog is covered with large, oval dark spots, each of which is surrounded by a lighter halo or border (Stebbins 2003, pp. 234-235). The snout (nose) is pointed and the tympanum (eardrum) is round and approximately equal in diameter to the eye (Baxter and Stone 1980, p. 41). Northern leopard frogs have a white stripe on the upper jaw and the dorsolateral folds (paired, glandular ridges that run along each side of the back from behind the eyes to the rear) are light cream to yellow and are continuous (not broken posteriorly). The belly is white to cream-colored, and the posterior thigh has a light background color with dark spots. There are two different color morphs (variants) of the northern leopard frog that most often occur in western Minnesota, eastern North Dakota, and South Dakota (Rorabaugh 2005, p. 570; McKinnel1

et al.

2005, p. 7). These color morphs do occur in other locations (for example, see Ammon 2002, p. 11), but they are most prevalent in Minnesota, North Dakota, and South Dakota, as described above. The burnsi morph lacks dorsal spots and the kandiyohi morph has mottled pigment patches (speckles) between the dorsal spots. Adult body lengths (snout-vent) range from 2 to 4.5 inches (in) (5 to 11 centimeters (cm)) (Stebbins 2003, p. 234). Females average slightly larger than males (Leonard

et al.

1993, p. 138; Werner

et al.

2004, p. 97). Subadult, or recently metamorphosed frogs (see Biology section below), range in length from 1 to 2 in (2 to 5 cm) (Merrell 1977, pp. 10-11). During the breeding season, males have enlarged or swollen thumbs (innermost digit) on forefeet, and vocal sacs are not apparent except when the frog is calling (Baxter and Stone 1980, p. 41; Hammerson 1999, p. 145). The typical breeding call is a prolonged “snore” followed by a series of stuttering croaks or chuckles that tend to accelerate towards the end (Hammerson 1999, p. 145). These vocalizations may be interspersed with chuckling sounds (Stebbins 2003, p. 235).

Northern leopard frogs deposit their egg masses underwater in clusters, which they attach to vegetation. Eggs are laid in a single orange- to grapefruit-sized globular clump, and may be laid individually or communally in groups (Nussbaum

et al.

1983, p. 182). Each egg mass may contain 645 to 7,648 individual eggs (Rorabaugh 2005, p. 572). The eggs hatch into tadpoles. Tadpoles (the larval stage in the lifecycle of the frog) are dark green to brown above with metallic flecking, and a cream to white translucent underside (Werner

et al.

2004, p. 97). Tadpoles metamorphose into young frogs. For a detailed description of northern leopard frog tadpoles, see Scott and Jennings (1985, pp. 4-16).

Distribution

The northern leopard frog historically ranged from Newfoundland and southern Quebec, south through the northeast portions of the United States to West Virginia, west across the Canadian provinces and northern and central portions of the United States to British Columbia, Oregon, Washington, and northern California, and south to Arizona, New Mexico, and extreme western Texas (Rorabaugh 2005, p. 570).

Current range maps tend to show an extensive and connected distribution for the northern leopard frog; however, its actual distribution is sparse and fragmented in Washington, Oregon, Idaho, California, Nevada, Arizona, New Mexico, Utah, Colorado, western Montana, and western Wyoming in the western United States (Rorabaugh 2005, pp. 570-571), throughout New England (New Hampshire Fish and Game Department 2005, pp. A208-A209), and in British Columbia, Northern Territories, Alberta, Saskatchewan, and parts of Manitoba in Canada (Committee on the Status of Endangered Wildlife in Canada 2009, p. iii).

Habitat

The northern leopard frog is an amphibian (a cold-blooded vertebrate that spends some time on land, but must breed and develop into an adult in water) and as such is ectothermic (incapable of generating their own body heat) (Wells 2007, p. 2). They have highly permeable skin, which allows for rapid passage of water and gases so that they can use their external environment to regulate body temperature and moisture loss (Wells 2007, pp. 2-3). As part of its complex life history, the northern leopard frog requires a mosaic of habitats, which includes aquatic overwintering and breeding habitats, and upland post-breeding habitats, as well as habitat linkages, to meet the requirements of all of its life stages (Pope

et al.

2000, p. 2505; Smith 2003, pp. 6-15; Rorabaugh 2005, pp. 571-575). Although aquatic breeding habitat is required for long-term population survival, upland foraging, dispersal, and overwintering habitats are critical if individual leopard frogs are to survive to reproductive maturity. For example, researchers noted an area near Chicago that had low northern leopard frog abundance, but extensive potential aquatic breeding habitat. It was not until habitat surrounding the ponds was restored from scrub forest to grasslands that leopard frog numbers increased dramatically (K.S. Mierzwa, pers. comm. in Pope

et al.

2000, p. 2506). These complex habitat requirements make northern leopard frogs particularly vulnerable to the impacts of habitat loss and fragmentation. Reduction or removal of these habitats or loss of connectivity between habitat components could reduce the capacity of the landscape to support the species (Pope

et al.

2000, p. 2505; Green 2005, p. 31).

Northern leopard frogs breed in a variety of aquatic habitats that include slow-moving or still water along streams and rivers, wetlands, permanent or temporary pools, beaver ponds, and human-constructed habitats such as earthen stock tanks and borrow pits (Rorabaugh 2005, p. 572). Successful breeding areas typically do not contain predaceous fish or other predators (Merrell 1968, p. 275; Hine

et al.

1981, p. 12; Orr

et al.

1998, p. 92; Smith 2003, pp. 19-21). Emergent vegetation, such as sedges and rushes, are important features of breeding and tadpole habitats (Gilbert

et al.

1994, p. 468; Smith 2003, pp. 8-9), and tadpoles are most often found in backwaters and still pools (Rorabaugh 2005, p. 572).

Sub-adult northern leopard frogs typically move from breeding areas to

feeding sites along the borders of larger, more permanent bodies of water, as smaller frogs are closely tied to water (Merrell 1970, p. 49). Recently metamorphosed frogs will move up and down drainages and across land in an effort to disperse from breeding areas (Seburn

et al.

1997, p. 69) and may disperse more than 0.5 mile (mi) (800 meters (m)) from their place of metamorphosis (Dole 1971, p. 223). Dole (1971, p. 226) found that dispersal in Michigan occurred on warm, rainy nights and that frogs dispersed overland; however, warm rains are not common in all parts of the species' range and other dispersal routes may be important as well. Streams are an important corridor for dispersing juvenile frogs (Seburn

et al.

1997, pp. 68-69), and vegetated drainage ditches may also facilitate connectivity between seasonal habitats (Pope

et al.

2000, p. 2505). In some areas of the western United States, subadults may remain in the breeding habitat within which they metamorphosed (Smith 2003, p. 10).

In addition to the breeding habitats, adult northern leopard frogs require stream, pond, lake, or river habitats for overwintering and upland habitats adjacent to these areas for summer feeding. In summer, adults and juveniles commonly feed in open or semi-open wet meadows and fields with shorter vegetation, usually near the margins of water bodies, and seek escape cover underwater. Post-breeding summer habitats do not include barren ground, open sandy areas, heavily wooded areas, cultivated fields, heavily grazed pastures, or mowed lawns (Rorabaugh 2005, p. 573). Buffer zones around wetland breeding sites should be maintained for movement to surrounding upland foraging habitat. Rittenhouse and Semlitsch (2007, p. 154) collected data from 13 published radio telemetry and tagging studies looking at frog and salamander use of terrestrial habitat surrounding wetlands. They found that, on average, a buffer width of 1,877 ft (572 m) around the breeding site is needed to encompass the non-breeding habitat used by 90 percent of the frogs in a given population (Rittenhouse and Semlitsch 2007, pp. 155-157).

During winter, northern leopard frogs are thought to hibernate underwater in ponds, in lakes, or on the bottom of deeper streams or waters that do not freeze to the bottom and that are well-oxygenated (Nussbaum 1983, p. 181; Stewart

et al.

2004, p. 72). Northern leopard frogs are intolerant of freezing and of waters that have severely reduced or complete loss of dissolved oxygen. If these conditions occur during hibernation, death of northern leopard frogs is likely (Rorabaugh 2005, p. 574).

Based upon their research in Wisconsin, Hine

et al.

(1981) described the ideal “breeding pond” as having the following features:

(1) The pond or wetland site should be located within approximately 1.0 mile (mi) (1.6 kilometers (km)) of suitable overwintering habitat (larger bodies of water) so that adults can find the breeding habitat when they emerge in the spring and juvenile frogs are able to find overwintering sites in the fall.

(2) In the spring, the water depth should be approximately 5 ft (1.5 m) or more so that there is balance of open water and vegetation cover.

(3) Emergent vegetation (such as sedge, bulrush, and cattail) should occur along at least two-thirds of the pond or wetland to provide escape cover and places to attach egg masses.

(4) The slope should be gradual to promote habitat for emergent vegetation.

(5) Natural terrestrial habitats should be maintained peripheral to wetlands summer habitat for adults post-breeding, for juvenile growth, and for dispersal or movement corridors.

(6) Water should be relatively permanent throughout the year, but should dry every decade or so in order to eliminate any predaceous fish that become established.

Water quality and temperature are important determinants of northern leopard frog habitat. Because northern leopard frogs have permeable skin, which may transfer external contaminants to its internal organs, good (

i.e.,

non-polluted) water quality is important at breeding locations. Chemical contamination of habitats can result in malformations, population declines, decreased growth rates, reduced activity, and other impacts to northern leopard frogs (Diana and Beasley 1998, pp. 267-276). Temperature plays an important role in both the springtime migratory and breeding behaviors of northern leopard frogs (Merrell 1970, pp. 50-51; Merrell 1977, pp. 5-6, 9). When ambient air temperature is greater than or equal to 50 degrees Fahrenheit (°F) (10 degrees Celsius (°C)), northern leopard frogs move from their overwintering sites to their breeding sites (Merrell 1970, p. 50). The calling sites and areas where egg masses are deposited are not random and appear to be chosen based upon temperature as these activities tend to be located in the warmest portions of breeding ponds (Merrell 1977, p. 6).

Biology

As soon as males leave overwintering sites, they travel to breeding ponds and call in shallow water (Smith 2003, p. 13). Breeding typically occurs during a short period in the spring beginning in early April (Pace 1974, p. 92; Corn and Livo 1989, p. 4); at higher elevations and more northern latitudes, the onset of breeding is late April to early May (Corn and Livo 1989, p. 5; Gilbert

et al.

1994, p. 467). Most northern leopard frogs are sexually mature at age 2, although the age of sexual maturity may vary from age 1 to age 3 in any given population depending upon environmental conditions (Leclair and Castanet 1987, p. 368; Gilbert

et al.

1994, pp. 468-469). Male frogs attract females by calling from specific locations within a breeding pond when temperatures are close to 68 °F (20 °C) or more, with several males typically calling together to form a chorus (Merrell 1977, p. 7). Eggs are typically laid within breeding habitats, 2 to 3 days following the onset of chorusing (Corn and Livo 1989, p. 5). Eggs are laid in non-acidic, shallow (4 to 26 in (10 to 65 cm)), still water that is exposed to sunlight, and are usually attached to emergent vegetation just below the water surface (Merrell 1977, p. 6; Gilbert

et al.

1994, pp. 467-468; Pope

et al.

2000, p. 2505). Egg masses may include several hundred to several thousand eggs (Corn and Livo 1989, pp. 6-7) and are deposited in a tight, oval mass (Rorabaugh 2005, p. 572). Time to hatching is correlated with temperature and ranges from 2 days at 81 °F (27 °C) to 17 days at approximately 53 °F (12 °C) (Nussbaum

et al.

1983, p. 182).

Tadpoles are the ephemeral, feeding, non-reproductive, completely aquatic larvae in the life cycle of the frog (McDiarmid and Altig 1999, p. 2). The length of time required for metamorphosis (the development of the aquatic tadpole to a frog) is variable, and depending upon temperature, may take 3 to 6 months from time of egg-laying (Merrell 1977, p. 10; Hinshaw 1999, p. 105). Northern leopard frog tadpoles are predominantly generalist herbivores (plant eaters), typically eating attached and free-floating algae (Hoff

et al.

1999, p. 215); however they may feed on dead animals (Hendricks 1973, p. 100). Adult and subadult frogs are generalist insectivores (insect eaters) that feed on a variety of terrestrial invertebrates such as insect adults, larvae, spiders, and leeches (Merrell 1977, p. 15; Collier

et al.

1998, p. 41; Smith 2003, p. 12; Rorabaugh 2005, p. 575). In addition, adult northern leopard frogs have also been known to prey upon small

northern leopard frogs, birds, and snakes (Merrell 1977, p. 15).

Status

Northern leopard frogs, like many amphibian populations, are dynamic, and their individual numbers may naturally fluctuate in size within populations. However, across the range of the northern leopard frog, information suggests that there is an ongoing loss of populations throughout the species' range. The loss of populations across the landscape is what results in species' declines (Green 2005, p. 29). Population declines of northern leopard frogs are well-documented in the western United States and western Canada, but are also documented rangewide (through the Midwestern and Eastern United States), as described below.

The most recent complete summary of distributional and abundance patterns of the northern leopard frog is from Rorabaugh (2005, pp. 570-571), which documents a substantial contraction of the species' range, especially in the western two-thirds of the United States, where widespread extirpations have occurred. Other authors have also compiled summary data indicating population declines (

e.g.,

Smith and Keinath 2007, p. 14). Since the 1960s, the northern leopard frog has experienced significant declines and losses throughout its range (Gibbs

et al.

1971, p. 1028), particularly in the western United States and western Canada, and tends to become less abundant the farther west one proceeds (Corn and Fogelman 1984, p. 150; Hayes and Jennings 1986, p. 491; Clarkson and Rorabaugh 1989, p. 534; Corn

et al.

1989, pp. 26-29; Koch and Peterson 1995, pp. 84-87; Corn

et al.

1997, pp. 37-38; Weller and Green 1997, p. 323; Casper 1998, p. 199; Hammerson 1999, pp. 146-147; Leonard

et al.

1999, p. 51; Dixon 2000, p. 77; Smith 2003, pp. 4-6; Jennings and Fuller 2004, pp. 125-127; Werner

et al.

2004, pp. 97-98; Committee on the Status of Endangered Wildlife in Canada 2009, p. v; Germaine and Hays 2009, p. 537; Johnson

et al.

2011, p. 557).

Based upon this and other information, the northern leopard frog appears to be declining, is considered rare, or is locally extirpated from many historical locations in Arizona, California, Colorado, Idaho, Iowa, Minnesota, Missouri, Montana, Nebraska, Nevada, New Mexico, Oregon, Texas, Utah, Washington, Wisconsin, and Wyoming (Hayes and Jennings 1986, p. 491; Stebbins and Cohen 1995, p. 220; Johnson and Batie 1996; Bowers

et al.

1998, p. 372; Casper 1998, p. 199; Lannoo 1998, p. xvi; Mossman

et al.

1998, p. 198; Smith 2003, pp. 4-6; Smith and Keinath 2004, pp. 57-60; McCleod 2005, pp. 292-294; Rorabaugh 2005, p. 571; Johnson

et al.

2011, p. 561). The species is nearly extirpated from almost 100 percent of its historical range in Texas, California, Oregon, and Washington (Stebbins and Cohen 1995, p. 220; McAllister

et al.

1999, p. 15; Stebbins 2003, p. 235; Germaine and Hays 2009, p. 537).

Table 1 lists current NatureServe ranks for States and provinces in which the northern leopard frog is known to occur. NatureServe conservation status assessment procedures have different criteria, evidence requirements, purposes, and taxonomic coverage than the Federal Lists of Endangered and Threatened Wildlife and Plants, and therefore, these rankings may not coincide with legal listing processes (NatureServe 2008, p. 1). However, for a species as widespread as the northern leopard frog, the NatureServe rankings aid in summarizing the relative risks facing the northern leopard frog throughout its range and are provided here for this reason.

NatureServe lists Maryland and New Jersey as States where the northern leopard frog occurs. However, the Maryland Department of Natural Resources lists the northern leopard frog as an introduced species that occurs in one county (Maryland Department of Natural Resources 2011, p. 2), and the frog does not occur in New Jersey (Gessner and Stiles 2001, pp. 1-9; New Jersey Division of Fish and Wildlife 2006, pp. 1-2).

Table 1—NatureServe and State, Province, and Territory Ranks for Northern Leopard Frogs in States and Provinces It Is Known To Occur

[NatureServe 2011, p. 1]

State, province, territory or sovereign nation

Natural heritage program rank *

State, province, territory rank

Arizona

S2 (Imperiled)

Species of Greatest Conservation Need.

California

S2 (Imperiled)

Species of Greatest Conservation Need.

Colorado

S3 (Vulnerable)

Species of Greatest Conservation Need, Species of Special Concern.

Connecticut

S2 (Imperiled)

Special Concern Species.

Idaho

S3 (Vulnerable)

Species of Greatest Conservation Need.

Illinois

S5 (Secure)

Non-game Indicator Species.

Indiana

S2 (Imperiled)

Species of Greatest Conservation Need.

Iowa

S5 (Secure)

No ranking or status.

Kentucky

S3 (Vulnerable)

Species of Greatest Conservation Need.

Maine

S3 (Vulnerable)

Species of Greatest Conservation Need (Priority 3).

Maryland

S4 (Apparently Secure), introduced spp

No ranking or status (considered an introduced species).

Massachusetts

S3/S4 (Vulnerable/Apparently Secure)

Species of Special Concern, Species of Greatest Conservation Need.

Michigan

S5 (Secure)

Species of Greatest Conservation Need.

Minnesota

S4 (Apparently Secure)

No ranking or status.

Missouri

S2 (Imperiled)

Species of Conservation Concern.

Montana

S1/S3 (Critically Imperiled/Vulnerable)

Species of Concern, Species of Greatest Conservation Need.

Navajo Nation (NE Arizona, NW New Mexico, SE Utah)

S2 (Imperiled)

Endangered.

Nebraska

S5 (Secure)

At-Risk Species (Tier II).

Nevada

S2/S3 (Imperiled/Vulnerable)

Species of Conservation Priority.

New Hampshire

S3 (Vulnerable)

Species of Concern.

New Jersey

SNR (Unranked), species not present

Species not present.

New Mexico

S1 (Critically Imperiled)

Species of Greatest Conservation Need.

New York

S5 (Secure)

No ranking or status.

North Dakota

SNR (Unranked)

No ranking or status.

Ohio

SNR (Unranked)

No ranking or status.

Oregon

S1/S2 (Critically Imperiled/Imperiled)

Sensitive Critical, List 2 Species (threatened with extinction or presumed extinct).

Pennsylvania

S2/S3 (Imperiled/Vulnerable)

Priority Conservation Species (Tier 5).

Rhode Island

S2 (Imperiled)

Species of Greatest Conservation Need.

South Dakota

S5 (Secure)

No ranking or status.

Texas

S1 (Critically Imperiled)

No ranking or status (likely extirpated).

Utah

S3/S4 (Vulnerable/Apparently Secure)

Species of Concern (Tier III).

Vermont

S4 (Vulnerable)

No ranking or status.

Washington

S1 (Critically Imperiled)

Endangered.

West Virginia

S2 (Imperiled)

Species in Greatest Need of Conservation.

Wisconsin

S4 (Vulnerable)

No ranking or status.

Wyoming

S3 (Vulnerable)

Species of Greatest Conservation Need.

Alberta

S2/S3 (Imperiled/Vulnerable)

Threatened.

British Columbia

S1 (Critically Imperiled)

Endangered.

Labrador and Newfoundland

S3/S4 (Vulnerable/Apparently Secure)

No ranking or status.

Manitoba

S4 (Vulnerable)

No ranking or status.

New Brunswick

S5 (Secure)

No ranking or status.

Northwest Territories

SNR (Unranked)

No ranking or status.

Nova Scotia

S5 (Secure)

No ranking or status.

Ontario

S5 (Secure)

Not at risk.

Prince Edward Island

S4/S5 (Apparently Secure/Secure)

No ranking or status.

Quebec

S5 (Secure)

No ranking or status.

Saskatchewan

S3 (Vulnerable)

Interim Species at Risk.

* S1 = Critically Imperiled: At very high risk of extinction due to extreme rarity (often 5 or fewer populations), very steep declines, or other factors.

S2 = Imperiled: At high risk of extinction due to restricted range, few populations (often 20 or fewer), steep declines, or other factors.

S3 = Vulnerable: At moderate risk of extinction due to a restricted range, relatively few populations (often 80 or fewer), recent and widespread declines, or other factors. Such species are often rare or found locally in a restricted range.

S4 = Apparently Secure: Uncommon but not rare; some cause for long-term concern due to declines or other factors. Such species are likely to be quite rare in parts of their range, especially at the periphery.

S5 = Secure: Common; widespread and abundant. Such species are potentially rare in parts of their range, especially at the periphery.

SNR = Unranked. State or Province conservation status not yet assessed.

The International Union for the Conservation of Nature's “Red List Categories and Criteria” were developed for classifying species at high risk of global extinction (IUCN 2003, p. 1), and as such have different criteria, evidence requirements, purposes, and taxonomic coverage than the Federal Lists of Endangered and Threatened Wildlife and Plants. However, just as with the NatureServe data, because we are reviewing the entire range of the northern leopard frog, the International Union for the Conservation of Nature assessment is useful in summarizing the current status of the northern leopard frog throughout its range.

The International Union for the Conservation of Nature currently lists the northern leopard frog as a species of `least concern' in view of its wide distribution, tolerance to degree of habitat modification, and presumed large population (Hammerson

et al.

2004, p. 2). The International Union for the Conservation of Nature states that the population trend is decreasing (Hammerson

et al.

2004, p. 3), but the authors believe that the northern leopard frog is not declining fast enough to qualify for listing in a more threatened category (Hammerson

et al.

2004, p. 2). The International Union for the Conservation of Nature reviewed Hammerson

et al.

(2004, pp. 1-6) in 2011, and no updates were made to the 2004 review. Since 2004, Rorabaugh (2005, pp. 570-577) completed a status review for the northern leopard frog in the United States (Rorabaugh 2005, pp. 570-577), and the Committee on the Status of Endangered Wildlife in Canada published the Assessment and Update Status Report for the Northern Leopard Frog in Canada (Committee on the Status of Endangered Wildlife in Canada 2009, pp. 1-76). The Rorabaugh (2005, pp. 570-577) status review found that for a variety of reasons the northern leopard frog is declining throughout its range, but particularly in the western United States. The Committee on the Status of Endangered Wildlife in Canada (2009, pp. iii) assessment notes that there are continued declines for the northern leopard frog throughout the western provinces and evidence of declines in eastern Canada. The current International Union for the Conservation of Nature review does not cite either of these documents or provide any current threats assessment. The International Union for the Conservation of Nature analysis for the northern leopard frog also includes leopard frogs in Panama, which likely belong to the

Lithobates

complex, but do not belong to the same species as the northern leopard frog. Therefore, we do not consider the International Union for the Conservation of Nature review for the northern leopard frog a current assessment of the species' status in North America.

Western States

Until the late 1970s, northern leopard frogs were widespread and abundant in much of northern Arizona (Apache, Coconino, Greenlee, Mohave, Navajo, and Yavapai Counties) in springs, streams, rivers, stock tanks, and lakes throughout northern Arizona (Arizona Game and Fish Department 2009, p. 1).

Currently, there is one northern leopard frog population located near Seligman, Arizona; a metapopulation (several breeding locations in close proximity to one another) located south of Flagstaff, Arizona; and three refugial sites developed by the State and Service (and other partners) to assist in stocking northern leopard frogs to other locations in Arizona, north of the Colorado River. All of these locations are located in Coconino County. Outside of these locations, fairly rigorous visual encounter surveys conducted within the species' historical range, including Grand Canyon National Park and the Kaibab National Forest, have not located northern leopard frogs (Kaibab National Forest 2007, p. 1; Kaibab National Forest 2008, p. 1; Drost

et al.

2008, p. 7). The species is listed as a Species of Greatest Conservation Need in the Arizona State Wildlife Action Plan (Arizona Game and Fish Department 2006, Appendix M, p. 153) and has a NatureServe rank of S2 (Imperiled) (NatureServe 2011, p. 1). In Arizona, there is no open season for northern leopard frog, and collecting is illegal except as authorized by State permit, effective January 1, 1993 (Commission Order 41). The northern leopard frog has also significantly declined on the Navajo Nation (which is situated in southeastern Utah, northeastern Arizona, and northwestern New Mexico) in the last century. Most remote desert populations of northern leopard frogs were lost between the 1920s and 1970s, and mountain populations were lost in the late 1980s. The Navajo Nation has listed the northern leopard frog as a “Group 2—Endangered Species” on the Navajo Endangered Species List, which means its prospects of survival or recruitment on the Navajo Nation are in jeopardy (Navajo Nation Department of Fish and Wildlife 2009, p. 3).

The northern leopard frog is a State of California species of special concern and is listed as a Species of Special Concern (native populations only) (California Department of Fish and Game, Natural Diversity Database, 2009) and as a Species of Greatest Conservation Need in California Department of Fish and Game's State Wildlife Action Plan (California Department of Fish and Game 2007); however, the northern leopard frog is not listed under the California Endangered Species Act. The northern leopard frog may be taken under the authority of a sport fishing license, subject to restrictions (California Code of Regulations, Title 14, Section 5.05). The frog is ranked S2 (Imperiled) by NatureServe (NatureServe 2011, p. 1). Northern leopard frogs are likely native to the region east of the Sierra Nevada-Cascade crest in the following areas of California: upper Pit River basin (Shasta, Lassen, and Modoc counties), Surprise Valley (Modoc County), lower Klamath Lake basin (Siskiyou County), Lake Tahoe region (El Dorado County), Carson River drainage (Alpine County) and Owens River Valley (Mono and Inyo counties) (Jennings and Fuller 2004, p. 122). The northern leopard frog was introduced to at least 15 other sites in California, but most of these introductions have not resulted in naturalized populations that continue to exist today (Jennings and Hayes 1994, p. 80; Jennings and Fuller 2004, p. 119). There is a small, introduced population in Merced County, near the Merced National Wildlife Refuge (NWR) that persisted as recently as 2007 (Jennings and Fuller 2004, pp. 119, 127; Woolington 2009, pers. comm.). Since the 1970s, northern leopard frogs have disappeared from most (approximately 95 percent) of their historic range in California, (Jennings and Fuller 2004, p. 119; Rorabaugh 2005, p. 571) and may be completely extirpated from these areas of the State as we are not aware of any recent confirmed sightings. Jennings and Hayes (1994, p. 82) knew of only two extant, native northern leopard frog populations as of the 1990s: one adult was observed at Tule Lake National NWR (Siskiyou County) in 1990, and 8 to 10 juveniles were found near Pine Creek in Round Valley near Bishop (Inyo County) in 1994. Northern leopard frogs are no longer found on Tule Lake NWR (Adams 2011, pers. comm.), and no northern leopard frogs have been observed during amphibian surveys conducted on the Klamath Falls NWR Complex, including Tule Lake NWR (Austin 2009, pers. comm.). Recent surveys conducted by the California Department of Fish and Game did not locate any northern leopard frogs in the Owens River Area (Becker 2011, pers. comm.). In addition, surveys found that sites previously considered to be northern leopard frog habitat now contain nonnative aquatic species, and the habitat has been extensively modified such that there are likely few areas of suitable habitat left in the Owens Valley (Becker 2011, pers. comm.). Northern leopard frogs have not been found in the Lake Tahoe basin for over 20 years, and the species is presumed to be extirpated from the area (Jennings and Fuller 2004, p. 125). Jennings and Fuller (2004, p. 126) also report that a formerly isolated native northern leopard frog population on Hat Creek, Shasta County, is now apparently extirpated as well. Modoc NWR in northeastern California reported no known occurrences of northern leopard frogs on the refuge in recent times, and no northern leopard frogs were reported during numerous hours of amphibian survey time in 2004, 2005, and 2010 (Bachman 2011, pers. comm.).

The northern leopard frog was historically quite common throughout Colorado, but over the last 30 to 40 years, populations have declined and even been locally extirpated from portions of eastern and north-central Colorado, including Rocky Mountain and Mesa Verde National Parks (Corn and Fogleman 1984, p. 148; Corn

et al.

1989, p. 15; Stebbins and Cohen 1995, p. 220; Corn

et al.

1997, pp. 37-38; Hammerson 1999, pp. 146-147; Mesa Verde National Park 2009, p. 1; Johnson

et al.

2011, p. 561). The Colorado Division of Wildlife has designated the northern leopard frog a Species of Greatest Conservation Need as well as a Species of Special Concern due to low population status and a declining population trend (Colorado Division of Wildlife 2006, pp. 2, 28, 305). These are not statutory categories; however, the northern leopard frog is classified as “nongame” wildlife and their harassment, taking, or possession is prohibited without a permit (Colorado Division of Wildlife 2009, p. 3). NatureServe ranks the northern leopard frog as S3 (Vulnerable) in Colorado (NatureServe 2011, p. 1). Intensive surveys conducted from 2007 through 2009 in the Front Range of Colorado indicate that northern leopard frogs there have become rare and documented losses are widespread (Johnson and McKenzie 2009, p. 9; Keeley 2009, pp. 5-6; Johnson

et al.

2011, p. 562). Historically, northern leopard frogs were found at high densities in this region (Johnson

et al.

2011, p. 562). Along the Western Slope (the area west of the continental divide in Colorado), data suggest that northern leopard frog populations remain viable, especially in the northern region (Johnson and McKenzie 2009, p. 10). This supports information from Arapaho and Browns Park NWRs, both located in northwestern Colorado, that continue to support northern leopard frogs (Johnson 2009, pers. comm.; Smart 2009, pers. comm.). Northern leopard frogs were the most common amphibian in southwest Colorado until the late 1960s, but now they are rare (San Miguel 2009, pers. comm.). Despite conducting amphibian surveys for 15 years with an emphasis on locating northern leopard frogs, none have been detected within Mesa Verde National Park, Colorado. Historically,

this species was found abundantly along the Mancos River in the park and adjacent lands (San Miguel 2009, pers. comm.). However, the overall status of the northern leopard frog in western Colorado is not currently known (Johnson

et al.

2011, p. 563).

The Idaho Department of Fish and Game designated the northern leopard frog a Type 2 Species of Greatest Conservation Need (Idaho Department of Fish and Game 2005, Appendix B p. 6). A Type 2 species of greatest conservation need is defined as a rangewide or globally imperiled species that is experiencing significant declines throughout its range with a high likelihood of being listed in the foreseeable future due to its rarity (Idaho Department of Fish and Game 2005, Appendix B, p. 4). Reduced distribution and a declining population trend are noted in the Idaho Comprehensive Wildlife Conservation Strategy as reasons for the designation (Idaho Department of Fish and Game 2005, Species Account, p. 1). The northern leopard frog is also a protected nongame species, which means take or possession of the species is prohibited without a permit (Idaho Administrative Code 13.01.06-300.02). NatureServe ranks the northern leopard frog in Idaho as S3 (Vulnerable) (NatureServe 2011, p. 1). Both the Targhee National Forest and Kootenai NWR have records of northern leopard frogs from the 1970s (Service 1972, p. 11; Stebbins and Cohen 1995, p. 220). However, surveys in 1992 at 98 sites on the Targhee National Forest did not locate northern leopard frogs (Stebbins and Cohen 1995, p. 220), and Kootenai NWR has no records of frogs for the last 30 years (Rose 2009, pers. comm.). Deer Flat NWR amphibian surveys have only detected American bullfrogs (

Lithobates catesbeiana

). Northern leopard frogs are known to be present on Bear Lake, Grays Lake, and Minidoka NWRs, and presumed to be present on Camas NWR and Oxford Slough Wetland Protection Area (WPA) (Fisher and Mitchell 2009, p. 1).

Localized declines of northern leopard frogs are documented in Iowa (Lannoo

et al.

1994, pp. 317-318; Hemesath 1998, p. 216). Lannoo

et al.

1994 (p. 311) states, “From descriptions of the turn-of-the-century commercial “frogging” industry in Dickinson County (Iowa), we estimate that the number of leopard frogs has declined by at least two, and probably three orders of magnitude.” However, the northern leopard frog is ranked as Secure (S5) in Iowa by NatureServe (2011, p. 1) and is not considered a Species of Greatest Conservation Need (Iowa Department of Natural Resources 2006, p. 42). Currently, there is a continuous open season for northern leopard frogs in inland and boundary waters in Iowa, and up to 48 frogs can be collected per day (Iowa Department of Natural Resources 2011, p. 1). In 1991, the Iowa Department of Natural Resources initiated an annual anuran (frog and toad) survey. The survey is conducted by volunteers, and until 2007, volunteers were not required to distinguish between species of leopard frogs on the report forms (Iowa Department of Natural Resources 2009, p. 1). Survey data from 2007 and 2008 (when the species were separated) and older data from counties where it was thought only the northern leopard frog occurred were reviewed by the State. The analyses of this information suggest a possible downward trend in northern leopard frog presence, but the trend was not statistically significant (Iowa Department of Natural Resources 2009, p. 1).

Northern leopard frog populations began declining in Minnesota in the late 1960s or early 1970s (Rittschof 1975, p. 103; Minnesota Department of Natural Resources 2011a, pp. 1-2). The declines of northern leopard frog populations from the past are thought to have been substantial, but information is not detailed enough to know if the population is now stable or if it is still declining in Minnesota (Moriarty 1998, p. 168). However, because the species is still considered to be fairly common, it is not considered a Species of Greatest Conservation Need in Minnesota's Comprehensive Wildlife Strategy (Minnesota Department of Natural Resources 2006, Appendix B p. 9). The Minnesota Department of Natural Resources' northern leopard frog fact page does indicate that the northern leopard frog is still declining (Minnesota Department of Natural Resources 2011a, p. 2). The species is ranked S4 (Apparently Secure) by NatureServe (NatureServe 2011, p. 1). In Minnesota, from May 16 to March 31, licensed anglers and children under age 16 may take, use, buy, and sell an unlimited number of northern leopard frogs up to 6 inches long for bait (Minnesota Department of Natural Resources 2011b, p. 70). A Minnesota Department of Natural Resources commercial license is required to take northern leopard frogs for purposes other than bait.

Missouri is located on the periphery of the range for northern leopard frogs and the frog is currently only known to occur in two counties (Atchison and Mercer) that border Iowa (Missouri Department of Conservation 2009, p. 1). The northern leopard frog is listed as a Species of Conservation Concern by the Missouri Department of Conservation and NatureServe ranks it as Imperiled (S2) (Missouri Department of Conservation 2009, p. 1; NatureServe 2011, p. 1). This ranking is based upon the low number of known occurrences in Missouri and not based upon declining population trends (Missouri Department of Conservation 2009, p. 1). The Missouri Department of Conservation noted that it is likely that more populations are present in northern Missouri, but further surveys need to be completed to affirm this assumption (Missouri Department of Conservation 2009, p. 1). In Missouri, northern leopard frogs have regulatory protection from commercial take and non-resident collection. Missouri residents are allowed to possess up to five northern leopard frogs for education use (Wildlife Code Missouri 3CSR10-9.110); however, these five individuals cannot be sold, traded, shipped over State lines, or taken from public lands (Missouri Department of Conservation 2009, p. 2). Northern leopard frogs also cannot be used as live bait in Missouri (Wildlife Code Missouri 3CSR10-6.605).

Montana Fish, Wildlife, and Parks classified the northern leopard frog as a Species of Concern in Montana and it is considered a Species of Greatest Conservation Need in their Wildlife Conservation Strategy (Montana Fish, Wildlife, and Parks 2009, p. 1). Northern leopard frogs are protected from commercial collection in Montana (Montana Code Annotated 2009 87-5-116). Historically, northern leopard frogs occurred across the eastern plains of Montana and in the mountain valleys on both sides of the Continental Divide (Montana Fish, Wildlife, and Parks 2009, p. 1). However, since the 1990s, most previously known northern leopard frog populations on the west side of the Continental Divide in Montana are considered extirpated, and there has been a clear range contraction of northern leopard frogs (Werner 2003, p. 26; Montana Fish, Wildlife, and Parks 2009, p. 1). Currently, only two populations exist in western Montana. Surveys in the mid-1990s of historically occupied sites in central Montana, east of the Continental Divide, found only 19 percent of the sites to be occupied by northern leopard frogs (Montana Fish, Wildlife, and Parks 2009, p. 1). NatureServe provides a split rank for the State that reflects the difference in status between western (S1 Critically Imperiled) and eastern (S3 Vulnerable) Montana (NatureServe 2011, p. 1). Habitat restoration and survey efforts are being planned Statewide to provide

a current assessment of northern leopard frog distribution (Montana Fish, Wildlife, and Parks, 2009, p. 2).

The northern leopard frog occurs commonly in the State of Nebraska (McLeod 2005, p. 292) and has a NatureServe rank of S5 (Secure) (NatureServe 2011, p. 1). However, surveys conducted in 1997 and 1998 indicated a significant decline in northern leopard frog occurrences at the State level (McLeod 2005, p. 292). It is difficult to ascertain if this information represents a real decline or is representative of normal stochastic events, but data indicated significant differences from location data collected in the 1970s (McLeod 2005, p. 292). The Nebraska Game and Parks Commission identified the northern leopard frog as a Tier II At-Risk Species during development of the Nebraska Natural Legacy Project (2005, p. 319). Tier II species are typically those that are not at-risk from a global or national perspective, but are rare or imperiled within Nebraska. As of 2011, northern leopard frogs can no longer be commercially harvested or sold for bait in Nebraska; however, anglers can still collect them as bait for personal use (Nebraska Game and Parks Commission 2011, p. 5).

In Nevada, northern leopard frogs are currently ranked S2/S3 (Imperiled/Vulnerable) by NatureServe (NatureServe 2011, p. 1) and are on the Nevada Natural Heritage Program's Animal and Plant Watch List, which means they could be declining in Nevada or across much of their range, or may be less common than currently thought and could become at-risk in the future. The northern leopard frog is identified as a Species of Conservation Priority in the Nevada Wildlife Action Plan (Wildlife Action Plan Team 2006, p. 61). In addition, the northern leopard frog is a protected amphibian by Nevada statute (NAC 503.075) and cannot be collected for commercial, recreational, or educational purposes without a permit (Nevada Department of Wildlife 2009, p. 5). The Nevada Department of Wildlife notes that there is little historical or current information available to accurately assess the distribution and status of the northern leopard frog in Nevada (Nevada Department of Wildlife 2009, p. 1). However, recent surveys suggest that northern leopard frogs may no longer be abundant in Nevada and that there have been numerous local extirpations, for example, along the Truckee and Carson rivers in western Nevada and in springs of southern and eastern Nevada (Panik and Barrett 1993, p. 203; Hitchcock 2001, pp. 9, 109-110). While historical records and anecdotal evidence indicated that northern leopard frogs were once widely distributed in the State, the current species distribution is much smaller than the historical distribution (Hitchcock 2001, pp. 9, 38, 48). In addition, suitable northern leopard frog habitat is patchily distributed in the State due to the aridity and isolated nature of many wetland systems, which results in a discontinuous and limited distribution (Nevada Department of Wildlife 2009, p. 1). Recent Nevada Department of Wildlife records document northern leopard frog populations in Ruby Valley (including Ruby Lakes NWR) and Lower Mary's River in Elko and White Pine Counties; Spring Valley and Lake Valley in White Pine County; Lake Valley and Pahranagat Valley (including Pahranagat NWR) in Lincoln County; Carson River near Carson City; the lower Truckee River and Truckee meadows in Washoe County; and a small number of additional sites in western and northeastern Nevada (Hitchcock 2001, pp. 96-102; Service 2009, pp. 1-2; Nevada Department of Wildlife 2009, p. 2). Efforts to restore northern leopard frog habitat and re-establish the species have occurred along the lower Truckee River in western Nevada and on Pahranagat NWR (Horton 2010, pers. comm.; Rogers 2010, p. 7).

Historically, the northern leopard frog was documented from a large area in the northern and western part of New Mexico and along the entire length of the Rio Grande River valley, except southern Elephant Butte and northern Caballo Reservoirs (New Mexico Department of Game and Fish 2009, p. 1). Declines in northern leopard frogs have been reported from the Lower Rio Grande (below Caballo Reservoir), in the Jemez Mountains, and in the Chuska Mountains (Christman 2009, p. 5; New Mexico Department of Game and Fish 2009, p. 2). The species is believed to be extirpated from the Rio Grande Valley, south of Albuquerque (New Mexico Department of Game and Fish 2009, p. 3). Recent survey efforts indicate that northern leopard frogs are persisting in northern New Mexico, but most occupied sites contained small numbers of frogs with very few robust populations (Christman 2009, p. 13). The northern leopard frog is not listed as endangered or threatened in New Mexico under the Wildlife Conservation Act, but was designated a Species of Greatest Conservation Need by the New Mexico Department of Game and Fish, and NatureServe ranks it as S1 (Critically Imperiled) in New Mexico (New Mexico Department of Game and Fish 2006, p. 540; NatureServe 2011, p. 1). The northern leopard frog is protected from commercial take (Section 17-1-14 NMSA); however, take by New Mexico State residents for pets or other uses are uncontrolled (New Mexico Department of Game and Fish 2009, p. 2).

Historically, the northern leopard frog ranged Statewide in North Dakota and is still quite common today (North Dakota Game and Fish Department 2009, p. 1). Northern leopard frogs are widely distributed throughout the State and locally abundant in some locations (Newman 2009, p. 1; Scherr 2009, pers. comm.) but surveys conducted by Bowers

et al.

(1998, p. 372) found that the range of the northern leopard frog was less extensive in the prairie potholes region of North Dakota than previously described. Because of its distribution and local abundance, the northern leopard frog has no special status in the State, and there are no conservation programs that specifically target the northern leopard frog (North Dakota Game and Fish Department 2009, p. 1). Commercial frog licenses are available for unlimited collection of northern leopard frogs (North Dakota Administrative Code 30-03-04). NatureServe does not have a current ranking for North Dakota as it is currently under review (NatureServe 2011, p. 1).

The Oregon Department of Fish and Wildlife ranks the northern leopard frog as a “Sensitive Critical” species, meaning that it is imperiled with extirpation from a specific geographic area of the State due to small population sizes, habitat loss or degradation, or immediate threats (Oregon Biodiversity Information Center 2010, p. 7, 13). The sensitive species list is primarily a non-regulatory tool designed to provide a voluntary, proactive approach to conservation (Oregon Department of Fish and Wildlife 2008, p. 1). The Oregon Biodiversity Information Center lists the northern leopard frog as a “List 2 Species” meaning that it is threatened with extirpation or presumed to be extirpated from the State of Oregon (Oregon Biodiversity Information Center 2010, pp. 4, 13) and it is ranked S1/S2 (Critically Imperiled/Imperiled) by NatureServe (NatureServe 2011, p. 1). The Oregon Biodiversity Information Center (2010, p. 13), lists the following counties as containing historical locations for the northern leopard frog: Hood River, Wasco, Sherman, Gilliam, Morrow, Umatilla, Jefferson, Crook, Grant, Baker, Malheur, Klamath, and Jackson Counties. Rorabaugh (2005, p. 571) reported that northern leopard frogs are extirpated from most historical

localities in Oregon. The six records we have from the Oregon Natural Heritage Information Center are observations from 1975, 1980, 1990, 1995, 1996, and 2003. We have found no records, current or historical, to indicate the presence of northern leopard frogs on either the Hart Mountain National Antelope Refuge (southern Oregon) or Sheldon NWR (northern Nevada) (Harper Collins 2009, pers. comm.). Frog surveys were conducted at Sheldon NWR in summer 2009, but they detected only nonnative American bullfrogs.

The status of the northern leopard frog in South Dakota is thought to be stable and NatureServe lists the frog as secure (S5) (South Dakota Department of Game, Fish, and Parks 2009, p. 1; NatureServe 2011, p. 1). The northern leopard has no specific protection in South Dakota and can be collected for commercial and non-commercial bait (South Dakota Laws and Regulations for Commercial Bait Dealers 2009, p. 1; South Dakota Department of Game, Fish, and Parks 2011, p. 23). The species' range includes almost the entire State based upon historical and current distribution maps (Fischer

et al.

1999, p. 12; Naugle

et al.

2005, p. 285). Smith

et al.

(2005, p. 9) found northern leopard frogs to be common in the Black Hills, and a Statewide herpetology (amphibian and reptile) survey report indicates that the distribution of the northern leopard frog in the State is stable (Backlund 2004, p. 8). However, there is no historical or recent abundance data to compare current survey data that would indicate population trend (Backlund 2004, p. 9). Information received from Lacreek and Waubay NWRs and the Huron Wetland Management District indicate northern leopard frogs are prevalent (Flannders-Wanner 2009, pers. comm.; Hubers 2009, pers. comm.; Koerner 2009, pers. comm.). Anuran auditory surveys (1997-1998) found northern leopard frogs to be one of the most widespread and wetland-abundant species in eastern South Dakota (Naugle

et al.

2005, p. 290).

The northern leopard frog's historic range in Texas was in the Rio Grande Valley, El Paso County (a relatively small portion of the State). However, extensive efforts to locate the frog have been unsuccessful (Dixon 2000, pp. 42, 77). The northern leopard frog is ranked S1 (Critically Imperiled) by NatureServe (NatureServe 2011, p. 1), but is not listed as a species of conservation concern in the Texas Comprehensive Wildlife Conservation Strategy (Texas Parks and Wildlife Department 2005, pp. 748-751). The Texas Parks and Wildlife Department webpage (Texas Parks and Wildlife Department 2011a, p. 11) lists the species as occurring in Texas, but the most current field guide for amphibians and reptiles of Texas indicates the species is likely extirpated (Dixon 2000, p. 77). The Texas Parks and Wildlife Department requires that anyone who captures a wild animal, including frogs, be licensed or permitted (Texas Parks and Wildlife Department 2011b, p. 1).

The Utah Division of Wildlife Resources considers northern leopard frog populations in Utah to be secure (Utah Division of Wildlife Resources 2009, p. 1). NatureServe ranks the northern leopard frog as S3/S4 (Vulnerable/Apparently Secure) (NatureServe 2011, p. 1). In Utah, the northern leopard frog is classified as “controlled” for collection, importation, and possession, and may only be collected with a certificate of registration (Administrative Rule R657-53: Amphibian and Reptile Collection, Importation, Transportation, and Possession). Historically the northern leopard frog is considered to be a wide-ranging species in Utah and is verified to have occurred in all but Davis and Wayne Counties (Utah Division of Wildlife Resources 2009, p. 2). Utah's Wildlife Action Plan lists the northern leopard frog as a Tier III Species of Concern (Sutter

et al.

2005, p. 5-6). Tier III species are of conservation concern because they are linked to at-risk habitats, they have suffered significant population declines, or there is little information regarding the species. The northern leopard frog was listed as a species of concern due to lack of information, water development, and disease. In 2006, the Utah Division of Wildlife Resources began compiling survey information and conducting surveys to determine the current distribution of northern leopard frogs in Utah. Recent surveys have documented northern leopard frogs at 97 new sites (not historical sites), for a total of 683 known sites in Utah (Utah Division of Wildlife Resources 2009, p. 2). Of these sites, 75 percent (512) are extant, and 25 percent (171) are considered historical, as the observations occurred prior to 1989 (Utah Division of Wildlife Resources 2009, p. 2). We do not have information regarding how many of these sites are breeding sites versus other observations (such as dispersing frogs).

The northern leopard frog was listed in 2000 as an endangered species under the Endangered, Threatened, and Sensitive Species Classification (Washington Administrative Code, Title 232, Chapter 12, Section 014) in Washington State after surveys of 17 known historic locations confirmed occupancy at only two sites (Leonard

et al.

1999, p. 52; Germaine and Hays 2009, p. 537). “Endangered” in this context means any wildlife species native to the State of Washington that is threatened with extinction throughout all or a significant portion of its range within the State. The northern leopard frog is ranked S1 (Critically Imperiled) in Washington State by NatureServe (NatureServe 2011, p. 1). Historically, the northern leopard frog occurred in six major watersheds in eastern Washington (Germaine and Hays 2009, p. 537). However, extensive surveys conducted at Gloyd Seeps and Potholes Reservoir in 2002-2005 indicate that the Gloyd Seeps population is likely no longer a functional breeding population and the Potholes Reservoir population is in sharp decline (Germaine and Hays 2009, p. 542). Although inclement weather prevented Washington Department of Fish and Wildlife from completing surveys in 2009, no observations of northern leopard frogs were made during what limited field time was available (Washington Department of Fish and Wildlife 2009, p. 32).

The northern leopard frog is not currently listed in Wisconsin, but over the past several decades, declines have been documented (Hine

et al.

1981, pp. 2-3; Mossman

et al.

1998, pp. 191-192, 198; Wisconsin Department of Natural Resources 2009, p. 1). In 1981, the Wisconsin Frog and Toad Survey began to monitor several species, including the northern leopard frog. The occurrence of a species is determined by whether or not the species is heard calling, and the abundance is ranked by the relative number of individuals heard calling at a site (Kitchell and Hay 2007, p. 1). Survey results from 1984 to 2007 indicate an overall decrease in the estimated population trend for northern leopard frogs (Kitchell and Hay 2007, p. 7). NatureServe ranks the northern leopard frog as S4 (Secure) (NatureServe 2011, p. 1). In Wisconsin, northern leopard frogs may be collected and possessed in unlimited numbers if the collector or possessor has a valid Class A Captive Wild Animal Farm License or a Commercial Bait License (Wisconsin Department of Natural Resources 2011, p. 13).

The northern leopard frog is considered to be widely distributed in Wyoming (Wyoming Game and Fish Department 2009, p. 1). The Wyoming Game and Fish Department identified the species as a Species of Greatest Conservation Need due to potential habitat degradation and loss, disease, absence of data, and contaminants (Wyoming Game and Fish Department

2005, p. 13). NatureServe ranks it as S3 (Vulnerable) (NatureServe 2011, p. 1). Population declines have been documented from the Laramie Plains, Targhee National Forest, and Grand Teton National Park (Baxter and Stone 1980, p. 44; Lewis

et al.

1985, p. 167; Koch and Peterson 1995, p. 85). No population trend data are available for northern leopard frogs in Wyoming. Anecdotal reports and local survey information indicate that the frog may be common throughout eastern and southwestern Wyoming (Wyoming Game and Fish Department 2009, p. 1); however, others reports indicate that the present abundance of northern leopard frogs in Wyoming is unknown and the population trend is declining (Smith and Keinath 2007, p. 14). The Wyoming Game and Fish Department manages commercial, scientific, and education activities through their collection permitting system (Wyoming Game and Fish Department 2009, p. 3).

Eastern States

The northern leopard frog still occurs throughout the eastern States it is historically known from (Connecticut, Illinois, Indiana, Kentucky, Maine, Massachusetts, Michigan, New Hampshire, New York, Ohio, Pennsylvania, Rhode Island, Vermont, and West Virginia) (Rorabaugh 2005, pp. 571-572). However, the frog currently has a very disjunct distribution throughout the northeast (New Hampshire Fish and Game Department 2005, pp. A208-A209); some populations are thought to be both locally and regionally declining (Smith and Keinath 2007, p. 14; Spriggs 2009, p. 29), and, in some cases, local extirpations have occurred (Rorabaugh 2005, p. 571; Spriggs 2009, p. 26). For example, habitat loss from urban development has resulted in local extirpations in Connecticut, Massachusetts, and Rhode Island (Klemens 2000, p. 41; Rorabaugh 2005, p. 571). Northern leopard frog declines also occurred in the Midwest in Michigan, Minnesota, and northeastern Illinois in the late 1960s or early 1970s (Rittschof, 1975, p. 103; Moriarty 1998, p. 168; Mierzwa 1998, p. 117), and although some populations have recovered, others have not (Mierzwa 1998, p. 117; Moriarty 1998, p. 168).

In 1999, the Northeast Endangered Species and Wildlife Diversity Technical Committee published a list of regional species of conservation concern, which included the northern leopard frog. The northern leopard frog was added to the list based upon declining populations or high risk of disappearing from the Northeast, lack of data with suspicion of risk of disappearing from the region, and special circumstances (such as vulnerability to collecting pressures) (Therres 1999, p. 97).

Northeast Partners in Amphibian and Reptile Conservation, using information from State wildlife action plans and other sources, developed the Northeast Amphibian and Reptile Species of Regional Responsibility and Conservation Concern (Northeast Partners in Amphibian and Reptile Conservation 2010, pp. 2-3). Based upon their analysis, the Northeast Partners in Amphibian and Reptile Conservation ranked the northern leopard frog as a species of High Concern and Regional Responsibility that should be considered a target for habitat and landscape-based conservation initiatives (such as land protection), may be an appropriate indicator for long-term monitoring to detect changes in distribution due to climate change, and should be among the highest priority species for Northeast Partners in Amphibian and Reptile Conservation to target conservation efforts (

e.g.,

create a regional species working group) (Northeast Partners in Amphibian and Reptile Conservation 2010, pp. 3-5). The ranking is based upon the number of northeastern States that comprise a species' U.S. distribution and the number of States that listed the species in their Wildlife Action Plans. Based upon their analysis, the northeastern States make up less than 50 percent of the northern leopard frog's U.S. distribution (occurs in 9 of 14 northeastern States), and it is listed as a Species of Greatest Conservation Concern in 6 of the 9 States it inhabits (Northeast Partners in Amphibian and Reptile Conservation 2010, p. 5).

In Connecticut, the northern leopard frog is locally common along sections of the Connecticut River and its tributaries (the Farmington, Scantic, and Coginchaug Rivers) (Klemens 2000, p. 40). Historical records of northern leopard frog distribution indicate that the frog was once widespread; current information indicates that the northern leopard frog no longer is found in some of these areas (Klemens 2000, p. 41). The northern leopard frog is considered a “Special Concern” species under Connecticut's State Endangered Species Act (Connecticut Department of Environmental Protection 2005, Appendix 1-b p. 18), and the NatureServe rank is S2 (Imperiled) (NatureServe 2011, p. 1). There is no open season for taking northern leopard frogs in Connecticut (Title 26 Fisheries and Game, Department of Environmental Protection Sec. 26-66-13).

Northern leopard frogs experienced a die-off in the 1960s or early 1970s in northeastern Illinois, but have since recovered in localized areas where extensive wetland habitat still occurs (Mierzwa 1998, p. 117). The northern leopard frog is less common in areas where significant wetland loss has occurred (Mierzwa 1998, p. 117). Statewide, the northern leopard frog is considered to be abundant with a stable and secure population trend in Illinois (S5 (Secure) ranking from NatureServe) (Smith and Keinath 2007, p. 14; NatureServe 2011, p. 1). However, most amphibian sampling efforts in Illinois have been largely opportunistic, and data are likely insufficient to accurately determine changes in distribution and abundance of species such as the northern leopard frog (Illinois Department of Natural Resources 2005, p. 102). The Illinois Comprehensive Wildlife Conservation Plan and Strategy identified the northern leopard frog as a non-game indicator species for improving wetland habitat (Illinois Department of Natural Resources 2005, p. 172). It is unlawful to take, possess, buy, sell, offer to buy or sell or barter any reptile, amphibian, or their eggs or parts taken from the wild in Illinois for commercial purposes unless otherwise authorized by statute (17 Illinois Adm. Code Section 880-10). If a person possesses a valid fishing license, they may take up to eight northern leopard frogs per day (17 Illinois Adm. Code Section 880-20, 880-30).

The northern leopard frog's range in Indiana includes northern and eastern Indiana. Minton (1998, pp. 217-220) noted significant declines in the northern leopard frogs populations based on observations he made from 1948 to 1993 throughout Indiana. The species is listed as a Species of Greatest Conservation Need in the Indiana Comprehensive Wildlife Strategy, listed as a Species of Special Concern by the Indiana Department of Natural Resources, and is ranked as Imperiled (S2) by NatureServe (Indiana Department of Natural Resources 2006, p. 30; NatureServe 2011, p. 1). In Indiana, an individual with a valid hunting or fishing license may collect up to four northern leopard frogs for non-commercial purposes (Indiana Department of Natural Resources 2011, p. 11).

The northern leopard frog is known historically from 22 counties in northern Kentucky (Kentucky Department of Fish and Wildlife Resources 2010, Amphibian Species Accounts, Northern leopard frog).

However, the species is considered to be decreasing in Kentucky, and populations have declined throughout the frog's historical State range. Kentucky Department of Fish and Wildlife Resources' recent survey records (1984-2004) show northern leopard frogs persisting in 10 counties, and no longer present in 12 counties (Kentucky Department of Fish and Wildlife Resources 2010, Amphibian Species Accounts, Northern leopard frog). The species is considered to be a Species of Greatest Conservation Need and ranked by NatureServe as Vulnerable (S3) (Kentucky Department of Fish and Wildlife Resources 2010, Appendix 1-1 p. 6; NatureServe 2011, p. 1). The northern leopard frog may be collected for personal bait use in Kentucky (301 Kentucky Administrative Regulations 1:130).

The northern leopard frog is a Species of Special Concern in Maine (Maine Department of Inland Fisheries and Wildlife 2005, p. 28) and is listed as a Priority 3 Species of Greatest Conservation Need in the Comprehensive Wildlife Conservation Strategy (Maine Department of Inland Fisheries and Wildlife 2005, p. 90). The Maine Department of Inland Fisheries and Wildlife chose this ranking due to the low to moderate potential for the northern leopard frog to become extirpated in the State, but concerns remain regarding restricted distribution, status, or extreme habitat specialization. Currently, the present abundance and population trend for the northern leopard frog in Maine are unknown (Smith and Keinath 2007, p. 14), and NatureServe ranks the species as S3 (Vulnerable) (NatureServe 2011, p. 1). A wildlife or fish possession permit is required from the Commissioner to take, possess, or hold in captivity northern leopard frogs (Maine Department of Inland Fisheries and Wildlife 2009, p. 1).

The northern leopard frog occurs Statewide in Massachusetts, except in Barnstable, Dukes, and Nantucket Counties (Massachusetts Division of Fisheries and Wildlife 2006, p. 406). Due to the widespread release of captive northern leopard frogs, their historical distribution and native status in Massachusetts is uncertain (Cardoza and Mirick (2002) in Massachusetts Division of Fisheries and Wildlife 2006, p. 406). As part of the Massachusetts Audubon Herp Atlas Project (1992 through 1998), the northern leopard frog was reported to be well-distributed and confirmed from approximately 13 percent of the quadrants (Massachusetts Division of Fisheries and Wildlife 2006, p. 406). Though the northern leopard frog is not listed in Massachusetts (Massachusetts Division of Fisheries and Wildlife 2006, p. 107), because its status in the State is unclear, it is a species of regional conservation concern, a Species of Special Concern, and a Species of Greatest Conservation Need in the Massachusetts Comprehensive Wildlife Conservation Strategy (Massachusetts Division of Fisheries and Wildlife 2006, pp. 137, 274, 292, 343, 348). There is a closed season on the hunting, fishing, taking and possession of northern leopard frogs in Massachusetts (Massachusetts Division of Fisheries and Wildlife 2002, p. 1). NatureServe ranks the northern leopard frog in Massachusetts as S3/S4 (Vulnerable/Apparently Secure) (NatureServe 2011, p. 1).

The Michigan Department of Natural Resources describes the northern leopard frog's distribution in Michigan as unknown, but considered patchy, and notes that it appears to be declining based upon the lack of reports compared to historical records from the current Frog and Toad Surveys (Eagle

et al.

2005, Species of Greatest Conservation Need, p. 152; Smith and Keinath 2007, p. 14). The northern leopard frog is a Species of Greatest Conservation Need in Michigan's Wildlife Action Plan (Eagle

et al.

2005, p. 20 in Aquatic Threats by Species of Greatest Conservation Need), but is ranked by NatureServe as S5 (Secure) (NatureServe 2011, p. 1). In Michigan, an all-species fishing license is required to take northern leopard frogs for personal bait use (Michigan Department of Natural Resources 2011, p. 9).

The northern leopard frog is a Species of Concern in New Hampshire and ranked as S3 (Vulnerable) by NatureServe (2011, p. 1). Possession of northern leopard frogs in New Hampshire is prohibited without a permit (New Hampshire Fish and Game Department 2011, p. 1). Distribution records from 1992 to 2004 were verified for Coos, Merrimack, Rockingham, and Sullivan Counties; reports from a number of other towns have not been verified with a voucher photograph or specimen (New Hampshire Fish and Game Department 2005, p. A-209). Throughout the area that the ranges of northern leopard frogs and pickerel frogs (

Lithobates palustrus

) overlap, it is important to verify distribution records via a photograph or a specimen as northern leopard frogs are commonly confused with pickerel frogs. New Hampshire is the only State we found that appears to require this information for distribution records. Based upon this information, it is likely that the current distribution of northern leopard frogs in New Hampshire is unknown.

The northern leopard frog is not identified as species of greatest conservation need or a species of concern in the Comprehensive Wildlife Conservation Strategy for New York (New York Department of Environmental Conservation 2005, p. 73), and NatureServe (2011, p. 1) ranks the northern leopard frog as S5 (Secure). Persons holding a freshwater fishing license or combined hunting and fishing license (including those entitled to fish without a license) may take northern leopard frogs for personal bait use (except in New York City, Suffolk County, and Nassau County), and frogs may be imported, bought, and sold at any time (New York Department of Environmental Conservation 2010, pp. 10-11, 16). The northern leopard frog distribution map for New York shows it having a very wide distribution throughout the State (New York Department of Environmental Conservation 2011, p. 1), but local herpetologists have reported declines throughout New York (O'Donnell 2011, pers. comm.). It is likely that the current abundance and population trends for northern leopard frogs in New York are unknown (Smith and Keinath 2007, p. 14).

The northern leopard frog is broadly distributed throughout Ohio and is considered to be secure by the Ohio Department of Natural Resources, Division of Wildlife (2005, pp. 125, 138, 143) and other sources (Smith and Keinath 2007, p. 14). Currently, NatureServe does not have a ranking for Ohio (NatureServe 2011, p. 1). In Ohio, a permit is required to possess northern leopard frogs (Ohio Revised Code 1531.02). Walker (1946, p. 88) described the northern leopard frog as being one of the most abundant frogs in Ohio. It is still considered to be locally abundant, but it does appear to be declining where wetlands have been drained. The range appears to be contracting in the southeastern counties where extensive field efforts have yielded few recent records (Ohio Frog and Toad Calling Survey 2011, p. 1).

The current distribution, abundance, and population trend for northern leopard frogs in Pennsylvania is unknown (Smith and Keinath 2007, p. 14; Gipe 2011, pers. comm.). The Comprehensive Wildlife Conservation Strategy states that there has been a reduction in the northern leopard frog's range, and although it was previously common in Pennsylvania and the northeast, it is suspected that it has significantly declined in recent years (Pennsylvania Game Commission and

Pennsylvania Fish and Boat Commission 2005, p. 10-41). The northern leopard frog is considered a Priority Conservation Tier 5 Species, and the need for a long-term monitoring program is identified (Pennsylvania Game Commission and Pennsylvania Fish and Boat Commission 2005, p. 10-41). This conservation priority tier represents species that are fairly secure in Pennsylvania, but for which the Pennsylvania Biological Survey recommends some level of management attention. NatureServe (2011, p. 1) ranks the northern leopard frog in Pennsylvania as S2/S3 (Imperiled/Vulnerable). The collection of one northern leopard frog per day from Pennsylvania waters requires a fishing license, but a license is not required to take a frog from land (Pennsylvania Fish and Boat Commission 2011, pp. 1-2).

The northern leopard frog is a Species of Greatest Conservation Need and ranked by NatureServe as S2 (Imperiled) in Rhode Island (Rhode Island Department of Environmental Management, Division of Fish and Wildlife 2005, p. 24; NatureServe 2011, p. 1). Rhode Island currently has one small population of northern leopard frogs on an island; several other populations have been extirpated in recent years (O'Donnell 2011, pers. comm.). The removal from the wild, for any purposes, of northern leopard frogs is prohibited in Rhode Island, except by special permit (Rhode Island Department of Environmental Management, Division of Fish and Wildlife 2011, p. 38).

The Vermont Fish and Wildlife Department considers the northern leopard frog to be secure in Vermont (Kart

et al.

2005, p. 1 Secure Species Summary; NatureServe 2011, p. 1). The species is distributed along the western edge of Vermont and then scattered populations are documented throughout the rest of the State (Kart

et al.

2005, Distribution Map). Collection of northern leopard frogs for scientific research, education purposes, or for the purpose of using them as the subjects of art or photography is authorized through issuance of a scientific collection permit; other collections or take are authorized by Commissioner Letter with a valid hunting license (Vermont Fish and Wildlife Regulations Title 10, Chapter 1, Section 25).

The West Virginia Natural Heritage Program and NatureServe list a State rank of S2 (Imperiled) for the northern leopard frog (West Virginia Natural Heritage Program 2007, p. 11; NatureServe 2011, p. 1). The species is also listed as a Species in Greatest Need of Conservation (West Virginia Division of Natural Resources 2005, pp. 4F-Habitats-20, 5F-49, 5F-56). Statewide surveys were conducted between March 2008 and April 2009 to determine the status and distribution of northern leopard frogs in West Virginia (Spriggs 2009, p. 17). Surveys of 70 sites found only four occupied sites and only one of the sites constituted a breeding population (only single adult or juvenile frogs were located at the three other locations) (Spriggs 2009, pp. 38-39). In 2010, surveyors searched for northern leopard frogs at the known breeding population at Greenbottom Wildlife Management Area, West Virginia (including one day with four experienced surveyors), and found only one dead northern leopard frog (O'Donnell 2011, pers. comm.). Based upon Statewide survey data collected, Spriggs (2009, p. 29) recommended that the northern leopard frog NatureServe rank be changed to S1 (Critically Imperiled).

Canada

Historically, the northern leopard frog ranged across Canada from British Columbia to Nova Scotia. Canada represents approximately half of the current range of the northern leopard frog based on an estimation of land area in the United States and Canada. Within Canada, the northern leopard frog's range includes small to large portions of the area within the Northwest Territories, British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, and Newfoundland. The distribution of northern leopard frogs in western Canada is more closely tied to major river drainages than is the species' distribution in eastern Canada (Seburn and Seburn 1998, p. 9).

The northern leopard frog is uncommon in the Northwest Territories and is historically known from nine sites (Fournier 1997, p. 104). These historical locations encompass a small area between the northern borders of Alberta and Saskatchewan and the southern border of Great Slave Lake (Weller and Green 1997, p. 323). Since 1980, a few frogs have been reported from three sites (Seburn and Seburn 1998, p. 6). The northern leopard frog is considered rare within this restricted range, and a lack of data precludes any determination of a population trend (Fournier 1997, p. 104). The northern leopard frog is not ranked in the Northwest Territories by NatureServe (NatureServe 2011, p. 1).

In British Columbia, the northern leopard frog historically occurred in the Kootenay and Columbia River valleys and in the Rocky Mountains east of Fernie (Seburn and Seburn 1998, p. 6). Currently, there is one native northern leopard frog population remaining at the Creston Valley Wildlife Management Area (estimated population less than 60 adults), plus one introduced population that has likely been extirpated (Committee on the Status of Endangered Wildlife in Canada 2009, pp. 42-43). The British Columbia (or Rocky Mountain) population is listed as Endangered under the Species at Risk Act (Statues of Canada 2002, c.29), which provides protection similar to that of the Endangered Species Act in the United States. The northern leopard frog is also on the provincial Red List and is listed as Endangered under British Columbia's Wildlife Act (Revised Statutes of British Columbia 1996, c. 488). The northern leopard frog is ranked as critically imperiled (S1) (NatureServe 2011, p. 1) in British Columbia.

Historically, northern leopard frogs were widely distributed and locally abundant in central and southern Alberta, and in the extreme northeastern region of the province (Alberta Northern Leopard Frog Recovery Team 2005, p. 3). Beginning in 1979, the northern leopard frog disappeared suddenly from much of its range in Alberta (Roberts 1992, p. 14; Seburn and Seburn 1998, p. 10). All previously known populations in central Alberta are no longer present, and to the south, populations have disappeared or are restricted to small, fragmented habitats with limited opportunity for dispersal (Roberts 1992, p. 14). In 1990-1991 and 2000-2001, province-wide surveys were conducted to determine the distribution of northern leopard frogs in Alberta. In the first survey, 24 sites were found to be occupied; the more recent survey found that of 269 historical sites surveyed, only 54 supported northern leopard frogs (Alberta Northern Leopard Frog Recovery Team 2005, p. 4). Currently, the northern leopard frog is thought to occur in about 20 percent of historically occupied areas in Alberta (Wilson

et al.

2008, p. 864), and the NatureServe ranking is S2/S3 (imperiled/vulnerable) (NatureServe 2011, p. 1). The species is listed as Threatened under Alberta's Wildlife Act (Revised Statutes of Alberta 2000, Chapter W-10), and a recovery plan was prepared in 2005 (Alberta Northern Leopard Frog Recovery Team 2005).

Historically, northern leopard frogs were considered to be widespread and abundant in Saskatchewan (Seburn 1992, p. 18). However, the northern leopard frog experienced significant declines in the 1970s and is now absent

throughout most of its historical range (Didiuk 1997, p. 112; Weller and Green 1997, p. 323). Currently, the number of northern leopard frog populations in Saskatchewan is unknown, and there is no data to evaluate the population trends (Didiuk 1997, p. 112). Anecdotal information indicates that populations may be recovering (Seburn 1992, pp. 17-18), but declines and die-offs have also been reported and the overall population status is unknown (Committee on the Status of Endangered Wildlife in Canada 2009, p. 29). The current range of the northern leopard frog within Saskatchewan is thought to be discontinuous, and the majority of occurrences are in the very southern portion of the province (Saskatchewan Conservation Data Center 2006, p. 1). The northern leopard frog is currently on Saskatchewan's Interim Species at Risk List (Wildlife Act 1998, Chapter W-13.12), and is protected in provincial and national parks (Committee on the Status of Endangered Wildlife in Canada 2009, p. vi). The NatureServe rank for the northern leopard frog in Saskatchewan is S3 (Vulnerable) (NatureServe 2011, p. 1).

In Manitoba, northern leopard frogs suffered a significant die-off from 1975-1976, and within a year were absent from previously known population cores (Koonz 1992, p. 19; Committee on the Status of Endangered Wildlife in Canada 2009, p. 29). Since this time, populations have increased in some areas and remained extremely low in others (Koonz 1992, p. 20). Northern leopard frogs are not monitored in Manitoba and the current number and distribution of extant populations is not known (Committee on the Status of Endangered Wildlife in Canada 2009, p. 29). The current NatureServe rank for the northern leopard frog in Manitoba is S4 (secure) (NatureServe 2011, p. 1).

The northern leopard frog is thought to be common, widespread, and secure throughout southern and central Ontario, with sparse distribution in the north (Weller and Green 1997, p. 323; NatureServe 2011, p. 1). The species is currently listed as “Not at Risk” under the Ontario Endangered Species Act of 2007 (Statutes of Ontario 2007, Chapter 6) and under the Canadian Species at Risk Act (Ontario Nature 2011, p. 2). However, as with many parts of Canada, northern leopard frog populations have declined precipitously, particularly in northern and southwestern Ontario (Hecnar 1997, p. 9; Seburn and Seburn 1998, p. 10; Committee on the Status of Endangered Wildlife in Canada 2009, p. 29; Desroches

et al.

2010, pp. 308-309). Although the widespread declines of the 1970s did not occur in Ontario as they did in the provinces to the west, relatively recent mass mortality events resulting from ranavirus have been documented in Ontario (Greer

et al.

2005, p. 11; Committee on the Status of Endangered Wildlife in Canada 2009, p. 29). A 4-year study in the eastern and central regions of the province found declines of 23 percent (1992-1993) and 5 percent (1993-1994) in abundance of northern leopard frogs (Hecnar 1997, pp. 9, 11; Committee on the Status of Endangered Wildlife in Canada 2009, p. 29). Regional declines of northern leopard frogs have also been documented in southern Ontario, including the southern Great Lakes Region (Committee on the Status of Endangered Wildlife in Canada 2009, pp. 29-30). Hecnar (1997, p. 11) notes, “Anecdotal reports suggest that

R. pipiens

is the most abundant frog in the Essex Plain. During this study (1992-1993),

R. pipiens

declined in occurrence across all regions of southwestern Ontario.”

The northern leopard frog is widely distributed throughout the southern region of Quebec, with sparse populations in the central region of the province (Weller and Green 1997, p. 323). Weller and Green (1997, p. 323) note that there is no evidence of historic or recent declines in Quebec, but Gilbert

et al.

(1994, p. 468) found lower densities of northern leopard frog egg masses than reported in Wisconsin and anecdotal declines of northern leopard frogs in the Richelieu River system of Quebec. Bonin (1992, p. 24) states that trends in northern leopard frog populations in Quebec are not known based upon data collected for the Amphibian and Reptile Atlas. In addition, Desroches

et al.

(2010, pp. 308-309) found that the northern leopard frog was uncommon on the Quebec side of James Bay.

In New Brunswick, the northern leopard frog is distributed throughout the province and populations are thought to be secure (S5 NatureServe rank) (McAlpine 1997, p. 123; Weller and Green 1997, p. 323; NatureServe 2011, p. 1). The northern leopard frog occurs throughout mainland Nova Scotia and Cape Breton Island and is considered to be secure (S5 NatureServe rank) with no evidence of declines (Weller and Green 1997, p. 323; NatureServe 2011, p. 1). On Prince Edward Island, the northern leopard frog status is apparently secure (S4) or secure (S5) (NatureServe 2011, p. 1).

In Newfoundland, the northern leopard frog was introduced to the western side of the island on several occasions, but is no longer present (Buckle 1971, p. 74; Maunder 1997, p. 94). The species is at the edge of its range in Labrador, but occurs in a few, discrete locations that are apparently secure (Committee on the Status of Endangered Wildlife in Canada 2009, p. 30; NatureServe 2011, p. 1).

Summary

In summary, the northern leopard frog appears to be absent or declining throughout a large portion of its historical and current range in the western United States and western Canada (Rorabaugh 2005, pp. 570-571). The species generally tends to be more abundant and more secure in the eastern portion of its range, but there are indications that local, and possibly regional, declines may also be occurring in the eastern United States (such as in Connecticut, Indiana, Kentucky, Maine, Massachusetts, Michigan, New Hampshire, Rhode Island, and West Virginia) as well. Historically, regional declines in the western United States and Canada occurred in the 1960s through 1970s, and since this time the northern leopard frog has either not recovered in many of these areas (such as in Alberta, Arizona, British Columbia, Colorado, Idaho, western Montana, Nevada, New Mexico, Oregon, Texas, Washington, and western Wyoming) or the status of that recovery is unknown due to a lack of information regarding changes in the number of sites occupied across the species' range over time (such as in Manitoba, Minnesota, Saskatchewan, and Utah). Occupancy trend data are also lacking throughout much of the western and eastern portions of the northern leopard frog's range where the northern leopard frog's status appears to be stable or where it is unknown (such as in Iowa, Illinois, Nebraska, New York, North Dakota, Ontario, Pennsylvania, South Dakota, and Wisconsin), and as such, the overall range status is likely unknown. However, despite the lack of occupancy trend data, information indicates that in the eastern United States and eastern Canada, the northern leopard frog is still widespread and relatively common.

Distinct Vertebrate Population Segment

We consider a species for listing under the Act if available information indicates such an action might be warranted. “Species” is defined by the Act as including any subspecies of fish or wildlife or plants, and any distinct population segment (DPS) of any species of vertebrate fish or wildlife that interbreeds when mature (16 U.S.C. 1532(16)). We, along with the National Marine Fisheries Service (now the National Oceanic and Atmospheric Administration—Fisheries), developed

the Policy Regarding the Recognition of Distinct Vertebrate Population Segments (61 FR 4722; February 7, 1996), to help us in determining what constitutes a DPS. The policy identifies three elements that are to be considered regarding the status of a possible DPS. These elements include: (1) The discreteness of the population segment in relation to the remainder of the species to which it belongs; (2) the significance of the population segment to the species to which it belongs; and (3) the population segment's conservation status in relation to the Act's standards for listing (

i.e.,

is the population segment, when treated as if it were a species, is endangered or threatened?) (61 FR 4722; February 7, 1996). The first two elements are used to determine if a population segment constitutes a valid DPS. If it does, then the third element is used to consider whether such DPS warrants listing. In this section, we will consider the first two criteria (discreteness and significance) to determine if the western northern leopard frog is a valid DPS (

i.e.,

a valid listable entity). Our policy further recognizes it may be appropriate to assign different classifications (

i.e.,

threatened or endangered) to different DPSes of the same vertebrate taxon (61 FR 4722; February 7, 1996).

Discreteness

Under the DPS policy, a population segment of a vertebrate species may be considered discrete if it satisfies either one of the following two conditions:

(1) It is markedly separated from other populations of the same taxon as a consequence of physical, physiological, ecological, or behavioral factors. Quantitative measures of genetic or morphological discontinuity (separation based on genetic or morphological characters) may provide evidence of this separation.

(2) It is delimited by international governmental boundaries within which differences in control of exploitation, management of habitat, conservation status, or regulatory mechanisms exist that are significant in light of section 4(a)(1)(D) of the Act.

Marked Separation

In our evaluation of discreteness under the DPS policy, we primarily used the results of two recent genetic studies (Hoffman and Blouin 2004a, pp. 145-159; O'Donnell

et al.

2011, pp. 1-11) to evaluate whether any populations of the northern leopard frog should be considered markedly separate. We based our determination on these two studies because they provided comprehensive data on the genetic variation across the range of the species. The petition to list a “western DPS” of the northern leopard frog was mainly based on the genetic information and conclusions from the study by Hoffman and Blouin (2004a). There has since been an additional genetic study conducted on the species by O'Donnell

et al.

(2011) that we also used in this 12-month finding. We found no other relevant information regarding the other factors to consider in evaluating population discreteness, such as physical, physiological, ecological, or behavioral factors, or morphological characters. We therefore focused our analysis on these two genetic studies in determining whether the best available information supports that there are discrete populations of the northern leopard frog that would be considered markedly separate under our DPS policy.

Hoffman and Blouin (2004a) reported two different lineages (lines of descent from a common ancestor) of mitochondrial DNA (mtDNA) haplotypes in northern leopard frogs. Analyzing mtDNA data is one way to measure the genetic variation within a species. When mtDNA lineages are geographically localized and separated by geographic barriers, this information can be used to identify evolutionarily separate units when it is used in combination with patterns displayed by other genetic markers (Avise 2004, p. 301). A haplotype refers to a set of closely linked genetic markers present on one chromosome that tend to be inherited together. The more similar these genetic markers, or haplotypes, are in a given sample of frogs, the more closely related those frogs are likely to be (with the opposite also being the case). This study (Hoffman and Blouin 2004a, p. 152) showed haplotypes of mtDNA genetic markers grouping into a “western” lineage, occurring mostly west of the Mississippi River and Great Lakes region in the United States and Canada, and an “eastern” lineage, occurring to the east of this area.

The initial study by Hoffman and Blouin (2004a, pp. 146, 150) found that on a broad scale the eastern and western haploypes have diverged for approximately 2 million years, indicating that the western and eastern lineages have likely been separate to some degree for a long time period, with secondary contact following Pleistocene glaciation events that occurred in North America (Hoffman and Blouin 2004a, p. 152). The overall differences were measured at approximately 4 percent sequence divergence, and this amount of mtDNA divergence is considered to be relatively high and is comparable to the differences found between some other recognized ranid frog species (Jaeger

et al.

2001, p. 344; Hoffman and Blouin 2004a, p. 152). Hoffman and Blouin (2004a, p. 152) note that mtDNA divergence alone is not enough evidence to split eastern and western lineages into separate species and that more taxonomic work (such as research regarding nuclear genetic markers, morphology, and behavior) is needed before such a taxonomic revision would be justified. The results of this study indicated important genetic differences broadly between northern leopard frogs in the eastern and western portions of North America. However, additional data were needed to determine if the “western” lineage represented a separate population of the species.

Although a preliminary administrative report, the recent O'Donnell

et al.

(2011) study report by the U.S. Geological Survey was peer-reviewed and presents the findings of a robust analysis of the genetic variation of the northern leopard frog across its range in North America. The study replicated the earlier mtDNA analysis but had larger sample sizes (20-24 individuals per sample compared with 12 individuals per sample at most sample localities) and had more sample locations in the area of contact between the eastern and western lineages. In addition, it also included nuclear gene sequencing as well. Nuclear genetic sequences provided an additional way to measure genetic variation in populations of the northern leopard frog. Because of its maternal (mother to daughter) pattern of inheritance, mtDNA is inherited only as a single genetic unit and has some limits in value for evaluating recent and localized relationships within a species. However, DNA sequences from multiple nuclear genes provided more information from additional genetic makers. This is an important distinction because identification of geographic subdivisions, like judging population distinction in the case of this analysis of the northern leopard frog, depends on the related geographic patterns of different genetic markers (Avise 2004, p. 303).

The study by O'Donnell

et al.

(2011) was specifically designed to look at the genetic relationships of the species and to supplement the results of Hoffman and Blouin (2004) by increasing the number of samples in the area of probable overlap of the two lineages in the upper Midwest of the United States. The analysis for one mtDNA gene produced similar results to that of the earlier study—with strong divergence between east and west lineages and a narrow area of overlap (O'Donnell

et al.

2011, pp. 2-3). However, the study also analyzed DNA from four nuclear genes. These nuclear genetic data still indicated deeply divergent eastern and western lineages of the northern leopard frog. However, and most importantly for our DPS analysis, the results of the nuclear data showed a broad zone of introgression between the two areas (in other words, a mixing of haplotypes) (O'Donnell

et al.

2011, p. 10). We considered this large zone of introgression as the primary reason that a potential western population of the northern leopard frog is not considered markedly separate from other populations of the species.

So to determine whether these two lineages should be considered markedly separate populations and be considered discreet under our DPS policy, we looked at the relative amount of overlap in the distribution of northern leopard frogs that contain haplotypes from the eastern and western lineages. Hoffman and Blouin (2004a, pp. 147, 152, 155) found that the distributions of eastern and western haplotypes meet roughly at the Mississippi River and Great Lakes region, initially indicating that these geographic features may serve as physical barriers separating the eastern and western lineages. However, the additional nuclear genetic data from O'Donnell

et al.

(2011, p. 10) discussed above indicate the eastern and western lineages are not separated along these geographic features. Hoffman and Blouin (2004a, pp. 147, 152) also found some areas of co-occurrence of haplotypes of both lineages in Ontario, Canada, and indicated that this is likely the result of more recent (during the current interglacial period in North America) secondary contact between eastern and western lineages that were formerly separated. In addition, O'Donnell

et al.

(2011) reveal that the haplotype mixing evident in the nuclear analyses is more likely associated with introgression and that more research is needed to clearly explain the pattern of haplotype mixing. The full extent of current contact (and presumably gene flow from interbreeding) between northern leopard frogs with eastern and western haplotypes could not be evaluated in detail as a part of earlier study because there were only a few sample sites from the likely areas of contact in Wisconsin, Michigan, and western Ontario and limitations due to small sample sizes. Further, there are multiple factors that may be responsible for the co-occurrence of frogs with eastern and western haplotypes, for example, it is possible that the mixing of haplotypes between the east and west in the overlap zone may be attributable in part to the anthropogenic movement of individuals associated with the trade in northern leopard frogs that has taken place in this area since at least the 1950s (Gibbs

et al.

1971, p. 1027; Collins and Wilbur 1979, p. 17).

Hoffman and Blouin (2004a, pp. 150-151) also found one individual frog (from a sample of 10) from Arizona with an eastern haplotype. They suggested this haplotype is likely not from a native frog, but from a released pet or laboratory animal. It is reasonable to believe it was a released eastern frog, or a descendant of one, because there is commercial trade in leopard frogs and tadpoles transported to pet stores, laboratories, and schools throughout the United States and Canada for recreational and scientific uses (Fisher and Garner 2007, p. 3). Their supposition is also supported by specific genetic research regarding this Arizona population of northern leopard frogs, which found haplotypes of mtDNA consistent with frogs from extreme eastern North America (from New York, New England, and adjacent areas of Quebec and Ontario) widespread in the Stoneman Lake area of northern Arizona (Theimer

et al.

2011, p. 32).

The relatively small sample sizes (about 12 individuals were used for most sample localities) were a disadvantage of the Hoffman and Blouin (2004a, Appendix pp. 1-8) study in evaluating genetic variation across a narrow part of the range. While these sample sizes were useful for looking at broad patterns of geographic variation (which was the object of the study), they were less useful in answering our question of separation, because of their limited power for detecting haplotypes that may occur at low frequencies and there were few sample sites in the area of suspected overlap. The small differences in the amount of genetic variation at specific locations are important because even haplotypes at low frequencies can help us understand the relationships between the eastern and western lineages of northern leopard frogs and inform our determination of whether the western lineage is a markedly separate population. The O'Donnell

et al.

(2011, pp. 2-9) study utilized larger sample sizes and provides a level of detail more appropriate and helpful to evaluate similarities and differences in western and eastern lineages.

The results of O'Donnell

et al.

(2011, pp. 2-9) indicated that neither the Mississippi River nor the Great Lakes are acting as a physical barrier between western and eastern lineages of northern leopard frogs. The existence of western haplotypes in northern leopard frog populations located east of the Mississippi River and of eastern haplotypes in northern leopard frog populations located both north and south of the Great Lakes does not support a marked separation between eastern and western northern leopard frogs. Although the nuclear genetic sequences continue to show east-west trends in different haplotypes (supporting the mtDNA data of east-west differences), these nuclear data also indicate that western haplotypes (from frogs in the west) occur in frogs much farther to the east than the mtDNA data indicated. Western haplotypes of some of the nuclear genes were found extending east of the Mississippi River to the eastern end of the Great Lakes in New York (O'Donnell

et al.

2011, pp. 6-8), and eastern haplotypes of some of the nuclear genes were found as far west as Nebraska (O'Donnell

et al.

2011, p. 9). This area of overlap of haplotypes spans roughly 1,900 km (1,200 mi) from east to west across North America.

This broad co-occurrence of haplotypes of nuclear genes, as well as the more gradual geographic trends in haplotype distributions (O'Donnell

et al.

2011, pp. 4-9), indicates there is not a marked separation between eastern and western lineages of the northern leopard frogs. The overlap in genetic markers across the midwestern United States leads us to conclude that there is no physical barrier or other processes keeping northern leopard frogs in the western part of the range discrete from the frogs in the eastern part of the range. Ongoing genetic analyses (such as microsatellite allele frequency analyses) will likely provide additional information regarding geographic patterns of genetic variation in northern leopard frogs (O'Donnell

et al.

2011, p. 10), but these data are not currently available. Therefore, based upon the genetic information presented above (Hoffman and Blouin 2004a, pp. 145-159; O'Donnell

et al.

2011, pp. 1-10), there does not appear to be marked separation between possible eastern and western populations of northern leopard frogs. We do recognize that this lack of a marked separation between the eastern and western populations may be a result of a variety of factors, including the anthropogenic movement of individuals for the trade in northern leopard frogs, but at this time, we do not have data supporting this claim. Because the potential eastern and western populations are not markedly separate, they are not considered discrete under

the DPS policy. Based upon the best available information, we conclude that the potential western U.S. population of northern leopard frog is not genetically discrete, in other words not markedly separate, from other northern leopard frogs.

International Border

In order to determine that the populations of northern leopard frog in the western United States are a DPS, we must have found that the western United States populations were discrete from populations in the eastern United States and that the western United States populations were discrete from population in Canada. The DPS policy allows us to use international borders to delineate the boundaries of a DPS if there are differences in control of exploitation, conservation status, or regulatory mechanisms between the countries. However, because we do not have a discrete east-west boundary of the potential DPS, we did not conduct further analysis regarding the northern boundary of the potential DPS between Canada and the United States.

Evaluation of Discreteness

The information discussed in the preceding section provides information on the geographic patterns that we evaluated to determine that the genetic information does not indicate that northern leopard frogs from the western United States are markedly separate from other populations of the northern leopard frog.

We note that our application of the DPS policy does not require absolute reproductive isolation as a prerequisite to recognizing the discreteness of a population segment. The presence of a small degree of sharing of genetic markers would not necessarily preclude us from concluding that there is discontinuity between populations and that they were markedly separated. However, in this case of the northern leopard frog, we do not have the information to make such an evaluation of whether or not the two populations are actually reproductively isolated. Although the genetic patterns indicate discontinuity in eastern and western mtDNA and nuclear haplotypes, the available genetic data do indicate there is more than a small degree of sharing of genetic markers. Rather than a small degree of shared markers, we found a broad extent of introgression that has western haplotypes of some nuclear genes occurring in samples of northern leopard frogs as far as New York. Therefore, because of the large area of overlap in haplotypes indicating no apparent barrier between the two lineages, we conclude at this time based on the best available scientific data that there is not marked separation between the western and eastern U.S. populations. This does not mean that the western and eastern populations of northern leopard frogs, as has been suspected for many years, are not unique and do not have significant conservation value. It simply means that, per our policy, the best available data at this time do not support a marked separation between the two populations, based on genetics and other information available to us.

In conclusion, based on our review of the best available information and pursuant to our DPS policy, we find that the western U.S. populations of northern leopard frog are not discrete from other populations of northern leopard frogs.

Significance

Under our DPS Policy, once we have determined that a population segment is not discrete, we do not need to consider whether that population segment is significant.

Conclusion

On the basis of the best available information, we determined that the western U.S. population of the northern leopard frog is not discrete in relation to the other populations of northern leopard frog. Therefore, we find that the western U.S. populations of northern leopard frog do not represent a valid DPS.

Having determined that the western U.S. populations of northern leopard frog are not a valid DPS, we proceed below with an analysis of threats for the northern leopard frog throughout its range.

Summary of Information Pertaining to Five Factors

Section 4 of the Act (16 U.S.C. 1533) and implementing regulations (50 CFR part 424) set forth procedures for adding species to, removing species from, or reclassifying species on the Federal Lists of Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of the Act, a species may be determined to be endangered or threatened based on any of the following five factors:

(A) The present or threatened destruction, modification, or curtailment of its habitat or range;

(B) Overutilization for commercial, recreational, scientific, or educational purposes;

(C) Disease or predation;

(D) The inadequacy of existing regulatory mechanisms; or

(E) Other natural or manmade factors affecting its continued existence.

In making this finding, information pertaining to the northern leopard frog in relation to the five factors provided in section 4(a)(1) of the Act is discussed below.

In considering what factors might constitute threats to a species we must look beyond the exposure of the species to a particular factor to evaluate whether the species may respond to that factor in a way that causes actual impacts to the species. If there is exposure to a factor and the species responds negatively, the factor may be a threat and, during the status review, we attempt to determine how significant a threat it is. The threat is significant if it drives, or contributes to, the risk of extinction of the species such that the species warrants listing as endangered or threatened as those terms are defined in the Act. However, the identification of factors that could impact a species negatively may not be sufficient to compel a finding that the species warrants listing. The information must include evidence sufficient to suggest that these factors are operative threats that act on the species to the point that the species may meet the definition of endangered or threatened under the Act.

Due to the wide geographic range of the northern leopard frog, and the diversity of habitat types which it occupies throughout its range, there are a wide variety and relatively large number of factors that have the potential to impact the species. However, these factors may result in impacts at the individual, population, or species scale, and may have a variety of effects from minor habitat degradation to complete habitat loss and mortality. As such, it is important to consider the magnitude and extent of impacts when assessing the factors affecting a species, and we attempt to provide this context throughout our discussions below.

Factor A. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range

A number of hypotheses, including habitat loss, have been proposed for global amphibian declines (Blaustein

et al.

1994, p. 61; Collins and Storfer 2003, pp. 90-94; Stuart

et al.

2004, p. 1783; Green 2005, p. 28). In our review of the best scientific and commercial data available, impacts that are potentially affecting northern leopard frogs and their habitats throughout their range include habitat destruction, habitat fragmentation, and habitat degradation resulting from development, modification, and loss of wetland habitat. Because the northern leopard

frog, an amphibian, depends upon breeding ponds, upland foraging areas, overwintering aquatic habitats, and connectivity between these habitats across the landscape, it is very susceptible to the destruction (defined as complete loss of all or part of the frog's necessary habitat), fragmentation (isolation of all or part of the frog's necessary habitat without its alteration or destruction), and degradation (the deleterious alteration of all or part of the frog's necessary habitat) of its habitat (Green 2005, p. 28).

The destruction and degradation of northern leopard frog habitat has been widespread and has affected, and continues to affect, the species to some extent throughout its range (Maxell 2000, p. 15; Hitchcock 2001, pp. 64-66; Rorabaugh 2005, p. 576; Clarkson and Rorabaugh 1989, p. 535; Smith 2003, pp. 26-31). Habitat destruction and degradation is reported to be the primary threat to all ranid and lithobatid frogs in the United States (Bradford 2005, p. 923) and a principal cause of decline of northern leopard frogs in the western United States and Canada (Smith 2003, p. 4; Alberta Northern Leopard Frog Recovery Team 2005, p. 6; Rorabaugh 2005, p. 571; Committee on the Status of Endangered Wildlife in Canada 2009, p. 32). Factors with the potential to impact northern leopard frog habitat include wetland loss, agricultural development, livestock grazing, urban development, oil and gas development, forest management, roads, groundwater withdrawal, and air pollution. Below we present information about these factors and discuss the magnitude and extent of the impacts from these factors on the northern leopard frog.

Wetland Loss

As a species with aquatic and semi-aquatic life-history phases, freshwater wetland habitat is an extremely important component of northern leopard frog habitat. In order to discuss the different actions that result in destruction or modification of northern leopard frog habitat, it is important to understand what is known about the current overall status of wetlands throughout the range of the northern leopard frog.

It has been estimated that 53 percent of the Nation's former wetland area was lost from the 1780s to the 1980s (Dahl 1990, p. 5). In terms of States where the northern leopard frog occurs, Minnesota (42 percent loss), Maine (20 percent loss), Michigan (50 percent loss), and Wisconsin (46 percent loss) have the most remaining wetland area compared to historical times (Dahl 1990, p. 5). New Hampshire (9 percent loss) was the only State in the range of the northern leopard frog that lost less than 20 percent of its original wetland acreage (Dahl 1990, p. 5). California (91 percent loss), Connecticut (74 percent loss), Illinois (85 percent loss), Indiana (87 percent loss), Iowa (89 percent loss), Kentucky (81 percent loss), Missouri (87 percent loss), and Ohio (90 percent loss) lost over 70 percent of their original wetland acreage (Dahl 1990, pp. 5-6). The remaining States within the range of the northern leopard frog had estimated wetland losses ranging from 20 percent to 60 percent (Dahl 1990, p. 6).

Dahl (1990, p. 10) noted that wetland area in the lower 48 States had declined to the point that “environmental, and even socio-economic benefits (ground water supply, water quality, shoreline erosion, floodwater storage, trapping of sediments, and climatic change) are now seriously threatened.” The destruction and degradation of wetland and riparian habitat is thought to represent the most widespread impact to northern leopard frog populations in Arizona (Arizona Game and Fish Department 2009, p. 1), Colorado (Colorado Division of Wildlife 2009, p. 2), Idaho (Idaho Department of Fish and Game 2005), Montana (Montana Fish Wildlife and Parks 2009, p. 2), Nevada (Nevada Department of Wildlife 2009, p. 4), New Mexico (New Mexico Department of Game and Fish 2009, p. 3), North Dakota (North Dakota Game and Fish Department 2009, p. 2), Utah (Utah Department of Wildlife Resources 2009, pp. 2-3), Wisconsin (Wisconsin Department of Natural Resources 2009, p. 1), Connecticut (Klemens 2000, p. 1), Indiana (Indiana Department of Natural Resources 2006, p. 113), Kentucky (Kentucky Department of Fish and Wildlife Resources 2010, p. 27), Maine (Maine Department of Natural Resources 2005, p. 90), Massachusetts (Massachusetts Department of Fish and Wildlife 2006, pp. 276, 292, 328), Michigan (Eagle

et al.

2005, Threats p. 20), New Hampshire (New Hampshire Fish and Game Department, p. A-210), New York (New York Department of Environmental Conservation 2005, pp. 57-58), and Rhode Island (Rhode Island Department of Environmental Management, Division of Fish and Wildlife 2005, p. 22).

While the total wetland losses in the United States are significant, the information regarding status and trend of wetlands only looks at total losses and gains of wetland area; there is no comprehensive data assessing trends in the quality or function of lost wetlands (Dahl 2006, p. 74). Therefore, we do not know how much of the lost wetland habitat would have naturally functioned as northern leopard frog habitat. In short, while the extent of wetland losses is broad and widespread throughout the range of the species, we are unable to assess the magnitude or severity of impact of these losses at the species scale. There have most likely been losses of northern leopard frog habitat concurrent with these wetland losses, but large areas of wetland remain intact in many States, particularly in the eastern portion of its range in the United States. Further, the data above address total change in wetland area without reference to the causes of the losses; thus it is difficult to relate past losses to future losses in this context. Ongoing impacts to northern leopard frog habitats will be discussed more specifically in the following sections.

Since the late 1980s, creation of new wetland area has occurred, although the rate of replacement area is much slower than the historical loss rate (Dahl 1990, p. 5). Data collected from 1998 to 2004 indicate that for the first time since uniform monitoring began, wetland creation actions resulted in a larger net gain of wetlands than net loss of wetlands during this time period (Dahl 2006, p. 15). However, the location and types of wetlands that represent this gain in wetland acres has not necessarily resulted in the creation of northern leopard frog habitat. In terms of location, a majority of the wetland areas gained were created in the southeast, particularly in Florida, which is outside the range of the northern leopard frog (Dahl 2006, p. 62). Further, review of created ponds from 1986 to 1997 indicates that only 2 percent of these ponds were reclassified as vegetated wetlands; most created ponds are designed and maintained to function as open water basins—deep waters with little vegetated shoreline and steep slopes—that are not conducive to northern leopard frog breeding, foraging, or dispersal (Hine

et al.

1981, p. 12; Leja 1998, p. 351; Semlitsch 2000, p. 624). All of the created ponds that Dahl (2006, pp. 76-78) noted were manmade farm ponds, freshwater fishing ponds, detention ponds, and aquaculture ponds. Deepwater lakes and reservoirs also increased in area over this time period (typically associated with urban development) (Dahl 2006, p. 78). Many of these ponds or open water bodies are not an equivalent replacement for vegetated wetlands (Dahl 2006, p. 76), and although they count towards the total of wetland area in the conterminous United States, they do not necessarily indicate a gain in northern

leopard frog habitat, particularly if water quality, vegetation, and native species are not objectives for the created wetland.

In Canada, wetland loss has also occurred throughout the range of the northern leopard frog. Wetland habitat quality is considered to be a limiting factor for the one remaining northern leopard frog population in British Columbia (Committee on the Status of Endangered Species in Canada 2009, p. 16). It is estimated that approximately 60 percent of basins and 80 percent of wetland margins in the 1980s in southern Alberta were degraded and that local extirpations of northern leopard frogs likely occurred as a result (Alberta Northern Leopard Frog Recovery Team 2005, p. 6). By 1990, approximately 20 percent of prairie wetlands that likely functioned as northern leopard frog habitat in Manitoba were lost (Committee on the Status of Endangered Species in Canada 2009, p. 17). Similar patterns of significant wetland loss have occurred in southern Ontario and southern Quebec. Historically, 69 percent of southwestern Ontario consisted of wetlands; however, it is estimated that as much as 90 percent of southwestern Ontario wetlands no longer exist (Committee on the Status of Endangered Species in Canada 2009, p. 17). Again, similar to the situation in the United States, we do not have information assessing how much of this lost habitat may have functioned as northern leopard frog habitat or if any mitigation (such as created wetlands) has resulted in replacement habitat. While it is likely there have been losses of northern leopard frog habitat concurrent with these wetland losses, large areas of wetland remain intact, particularly in the eastern portion of Canada.

Across the range of the species, it is clear that significant total wetland area has been lost since colonial times. It is logically certain that some of these areas represented historic habitat for northern leopard frogs; however, it is not possible to assess the extent of loss of actual northern leopard frog habitats based on a generalized review of loss of wetlands. Further, while wetland losses have occurred, large areas of wetland remain, particularly in the eastern portion of the United States and Canada.

Agricultural Development

Agricultural development has occurred across the range of the northern leopard frog, but particularly in the Midwestern States of the United States (Leja 1998, p. 349). The U.S. Department of Agriculture, Natural Resource Conservation Service (USDA NRCS) has a broad land cover and use map that shows by State the amount of land in cropland, pastureland, rangeland, forest land, developed land, Federal lands, and other lands. Data from this map shows that greater than 80 percent of the total land area (outside Federal lands) in Iowa, Nebraska, North Dakota, and South Dakota is used for agricultural purposes, such as cropland, pastureland, and rangeland (USDA NRCS 2001). In addition, many other western and Midwestern States also have significant amounts of land identified as agricultural within the range of the northern leopard frog (USDA NRCS 2001). While agricultural development continues to be a large land-use practice in South Dakota (57 percent cropland), North Dakota (35 percent cropland), and Ohio (45 percent cropland) (USDA NRCS 2001), the northern leopard frog appears to be relatively stable in these States (Hossack

et al.

2005, p. 428; Rorabaugh 2005, p. 571), despite this level of usage.

Agricultural development may fragment, destroy, or degrade northern leopard frog habitat directly due to conversion of native habitats to cropland and de-watering of adjacent habitats, or indirectly through the introduction of contaminants and invasive species into habitats (Wang

et al.

1997, p. 10; Leonard

et al.

1999, p. 58; Leja 1998, pp. 345-353; Knutson

et al.

2004, p. 675; Rorabaugh 2005, p. 576). Most of the historic wetland loss discussed above is thought to be due to conversion to agriculture (Leja 1998, p. 349). Agricultural development can result in modification of river valley habitat, including draining of wetlands, channelization and damming of rivers, and development of irrigation systems (Wang

et al.

1997, p. 11; Findlay and Houlahan 1997, p. 1001), all of which may modify breeding, overwintering, and dispersal habitat for northern leopard frogs (Scott and Jennings 1985, p. 19; Lannoo

et al.

1994, pp. 317-318; Leja 1998, pp. 345-353; Knutson

et al.

2000, p. 139; Ammon 2002, p. 2; Idaho Department of Fish and Game 2005, Northern leopard frog species account; Colorado Division of Wildlife 2009, p. 1; Rogers 2010, p. 8). For example, in Idaho, Camas NWR is losing wetlands to groundwater depletion by nearby agriculture, and Grays Lake NWR and Minidoka NWR cannot control water levels because of senior water rights assigned to other agencies, and their use for agriculture (Fisher and Mitchell 2009, pers. comm.). In Canada, the past conversion of large areas of grassland to agriculture has also likely resulted in the loss of northern leopard frog habitat, particularly foraging and overwintering habitats near breeding sites (Didiuk 1997, p. 113; Hecnar 1997, p. 13). In southern Alberta, drainage of wetlands for agricultural use in the 1980s was extensive and is thought to have contributed to local extirpations of northern leopard frogs (Alberta Northern Leopard Frog Recovery Team 2005, p. 6). The land being used for agriculture in the prairies has lately increased by 62 million acres (25 million hectares), and there is pressure to alter remaining wetland areas (Committee on the Status of Endangered Wildlife in Canada 2009, p. 32).

Geographically isolated (or depressional) wetlands surrounded by upland watersheds (such as the prairie potholes region) make up a large proportion of the wetland resource in arid and semi-arid regions of the northern leopard frog's range (Skagen

et al.

2008, p. 594). However, although the “wet” (surface water) portion of the wetland is vitally important for northern leopard frog breeding, the upland terrestrial habitat adjacent to the wetland is also a critical component of their habitat needs (Semlitsch 2000, p. 620; Pope

et al.

2000, p. 2506; Gibbons 2003, p. 630; Semlitsch and Bodie 2003, p. 1223). Although agricultural development may result in the maintenance or creation of actual “wet” wetland habitat (Leja 1998, p. 350), crops and pastures—areas that provide poor or no habitat for northern leopard frog—typically occur on the immediate edge of the water (Guerry and Hunter 2002, p. 752; Committee on the Status of Endangered Species in Canada 2009, p. 32). Research indicates that land use practices around the wetland may be as important as the size of the wetland itself (Findlay and Houlahan 1997, p. 1007). Amphibian species richness increases with wetland area, and herpetofauna abundance, including the northern leopard frog, show a strong positive correlation with the proportion of forest cover on lands within 1.2 mi (2 km) of wetlands (Findlay and Houlahan 1997, pp. 1006-1007). Northern leopard frogs breeding in active agricultural lands may end up crossing roads and tilled agricultural fields which would increase the likelihood of mortality, and northern leopard frogs that breed in active agricultural lands require larger home ranges than do frogs that breed in intact wetlands and grasslands (Pember

et al.

2002, p. 4.9)

Habitat fragmentation caused by agriculture has also likely limited northern leopard frog dispersal, as frogs may have difficulty moving through active croplands (Didiuk 1997, p. 113;

Saskatchewan Conservation Data Centre 2006, p. 2). Agricultural development also tends to result in disturbed ground, which can impact the distance and the quality of habitat between habitat patches (Didiuk 1997, p. 113; Pember

et al.

2002, p. 4.9; Alberta Northern Leopard Frog Recovery Team 2005, p. 6; Mazerolle and Desrochers 2005, p. 455; Committee on the Status of Endangered Wildlife in Canada 2009, p. 32). Barren land, agricultural lands, and recently cut forests increase the resistance of the landscape to northern leopard frog movement (Mazerolle and Desrochers 2005, p. 462). Vegetation on undisturbed sites likely reduces evaporative water loss in dispersing or moving frogs through protection from the wind and sun (reduced dehydration), while surfaces with no vegetative cover likely endanger individual frogs and constitute barriers to frog movement (Mazerolle and Desrochers 2005, p. 462). In addition, agriculturally induced habitat fragmentation can increase the role of genetic drift, which may hamper adaptive responses to local environments (Johansson

et al.

2007, p. 2699). Research regarding the European common frog (

Rana temporia

) found that populations in fragmented agricultural habitats were smaller and had lower genetic diversity compared to populations in a more continuous landscape. More genetic diversity leads to healthier populations. Breeding pond isolation, resulting from fragmented landscapes, has also been shown to negatively affect population persistence and recolonization of ranid and lithobatid frogs to suitable habitats (Witte

et al.

2008, p. 381).

Agriculture is also the primary source of water pollution throughout the western range of the northern leopard frog and occurs primarily through sedimentation, nutrient pollution, pesticide pollution, and mineral pollution (Ribaudo 2000, pp. 5-11). On many NWRs, pesticide and herbicide use are regulated by Service Pesticide Use Plans, but these plans may not adequately account for toxicity to northern leopard frogs, and thus pesticide and herbicide use may result in impacts to individuals or populations of the species (Dickerson and Ramirez 1993, pp. 1-2; Fisher and Mitchell 2009, pers. comm.). Overwintering northern leopard frogs in permanent waters are likely to be in close contact with sediments on the pond bottom that may contain agricultural chemicals resulting from run-off (Didiuk 2007, p. 113). This close contact with chemicals may make the northern leopard frog more susceptible to potential adverse chemical effects in these areas.

Leopard frogs that inhabit agricultural wetlands and landscapes are also vulnerable to pesticide exposure (King

et al.

2008, p. 13) (see Pesticides under

Factor E

for further discussion). In addition, “hotspots” of amphibian malformations, including northern leopard frog malformations, tend to occur in altered wetlands (Lannoo 2008, p. 200) (see Malformations under

Factor E

for further discussion).

As described above, agricultural development has been shown to result in adverse effects to northern leopard frogs in some portions of its range. The above review of the best available information indicates that large areas of historical habitat have likely been lost due to agricultural development and that current habitats may continue to be subject to ongoing impacts of agricultural development. The most significant impacts associated with agricultural development are likely the loss of historical habitats due to conversion to agricultural lands. Ongoing impacts to areas currently associated with agriculture likely negatively impact local populations through reduced breeding success and individual survival. However, even States with a significant land base in agriculture (such as South Dakota, North Dakota, and Ohio) appear to be maintaining stable populations of northern leopard frogs. Therefore, though research indicates that agricultural development can have a negative impact on local populations of northern leopard frogs, the best available information does not indicate the ongoing impacts are significant at the species level. Based upon the best available information, agricultural development does not constitute a significant threat to the northern leopard frog at the species level now, nor do we have indication that it will in the future.

Livestock Grazing

Approximately 70 percent of the land surface in the western United States (including Montana, Wyoming, Colorado, New Mexico, Arizona, Utah, Nevada, California, Idaho, Oregon, and Washington) is or has been grazed by livestock (Fleischner 1994, p. 630; Krausman

et al.

2009, p. 15). Historical and ongoing livestock grazing are specifically identified as being responsible for the loss and degradation of northern leopard frog habitats, and for negatively affecting northern leopard frog populations at sites in Arizona (Clarkson and Rorabaugh 1989, p. 535; Sredl 1998, pp. 573-574), California (California Department of Fish and Game 2007), Idaho (Idaho Department of Fish and Game 2005, Appendix F), Montana (Maxell 2000, p. 15), Nevada (Hitchcock 2001, p. 66), North Dakota (Euliss, Jr. and Mushet 2004, p. 82), South Dakota (Smith 2003, p. 27), and Wyoming (BLM 2009, p. 3). For example, most of the habitat in the Pit River-Modoc Plateau area and the Owens Valley of California, where the northern leopard frog occurred historically, has been severely altered and fragmented largely because of livestock grazing practices. The essential habitats bordering riparian zones are either no longer present or so fragmented that the habitat can no longer support northern leopard frog populations (Jennings and Hayes 1994, p. 82). Although management may be changing in some areas, many wetland habitats are likely still recovering from historical grazing impacts (Krausman

et al.

2009, p. 16). This is particularly true because the western United States has a relatively arid climate, which can result in longer habitat recovery intervals, and perennial waters tend to be rarer and more disjunct from other waters than in the eastern United States.

Livestock select riparian habitats for water, shade, and cooler temperatures. They tend to spend a disproportionate amount of their time in riparian zones, and they can adversely affect these systems in a number of important ways (Fleischner 1994, pp. 633-635; Belsky

et al.

1999, pp. 420-424; Jones 2000, pp. 159-161). Because of this disproportionate use of mesic and riparian habitats by livestock, northern leopard frog populations are vulnerable to the effects of poorly managed livestock grazing (Maxell 2000, pp. 15-16; Smith 2003, p. 30). Specifically, trampling by livestock may result in the death of individual frogs (Bartlet 1998, p. 96; Maxell 2000, p. 15; Smith 2003, p. 30), and the compaction of soils around aquatic habitats, thereby decreasing infiltration of water into the soil, increasing soil erosion, and contributing to stream channel down cutting (Kauffman and Kreuger 1984, pp. 432-434; Belsky

et al.

1999, pp. 419-431). These impacts could hinder or prevent movements of northern leopard frogs by reducing and eliminating riparian vegetation that provides cover.

Impacts to water quality through increased sedimentation (Belsky

et al.

1999, pp. 420-424; Alberta Northern Leopard Frog Recovery Team 2005, p. 7) may reduce the depth of breeding ponds or overwintering habitats, increase water temperatures, and create favorable environments for diseases and parasites

known to contribute to mortality in northern leopard frogs (Maxell 2000, pp. 15-16; Johnson and Lunde 2005, pp. 133-136; Ouellet

et al.

2005, p. 1435). Increased watershed erosion caused by livestock grazing can accelerate sedimentation of deep pools used by frogs (Gunderson 1968, p. 510). The indirect effects of grazing on northern leopard frog habitat may also include increases in sedimentation generated by grazing. Sediment can alter primary productivity and fill interstitial spaces in drainage materials with fine particulates that impede water flow, reduce oxygen levels, and restrict waste removal (Chapman 1988, pp. 5-10).

Disturbance from livestock wading and defecating in northern leopard frog habitat has been found to have negative effects on the reproductive success of northern leopard frogs and to result in negative impacts to habitat (Knutson

et al.

2004, p. 677). The significant input of urine and manure and the turbidity caused by livestock disturbance was found to lead to poor water quality (such as increased nitrates) and low oxygen concentrations, which can result in reduced development and survival of egg masses and tadpoles (Marco

et al.

1999, p. 2837; Rouse

et al.

1999, pp. 800-802; Ortiz

et al.

2004, pp. 235-236; Alberta Northern Leopard Frog Recovery Team 2005, p. 7; Earl and Whiteman 2009, p. 1336). In addition, Knutson

et al.

(2004 p. 675) found that the grazed ponds had little or no aquatic or emergent vegetation, and that this was a result of livestock wading in the pond.

In contrast, there is information from some portions of the range of the species that indicates leopard frog species can persist, and even benefit from, well-managed livestock grazing (Hitchcock 2001, p. 62; Service 2007, pp. 32-34; Alberta Northern Leopard Frog Recovery Plan 2005, p. 7; Arizona Game and Fish Department 2009, pp. 2-3; New Mexico Department of Fish and Game 2009, p. 3). Limited grazing around riparian areas can create open foraging areas for leopard frogs, and livestock management can result in the creation of stock tanks (ponds or impoundments that function as waterholes) that can provide breeding and dispersal habitat for northern leopard frogs, particularly in arid western landscapes (Sredl

et al.

1997, pp. 46, 49; Theimer

et al.

2011, p. 11).

Historically, livestock grazing has likely resulted in degraded habitats and local declines and extirpations of northern leopard frogs in some portions of their range. However, the information reviewed above suggests that livestock grazing has only resulted in substantive impacts in the western portions of the United States and Canada, with very little to no information suggesting how livestock grazing has or is adversely impacting northern leopard frog populations in the eastern United States or eastern Canada. Further, declines and extirpations associated with livestock grazing are likely historical impacts in most areas, with ongoing impacts manifesting primarily through effects associated with degraded habitats. Finally, there is no evidence that livestock grazing use is spreading to areas that are not already subject to those uses. Therefore, the best available scientific information indicates that livestock grazing does not constitute a significant threat to the northern leopard frog at the species level now, nor do we have indication that it will in the future.

Urban Development

Urbanization refers to the development of areas for human uses. Areas subject to urbanization tend to be correlated to areas with increased human population growth. This development is resulting in impacts to northern leopard frog habitat across its range (Hitchcock 2001, pp. 64-66; Smith and Keinath 2007, p. 29; Connecticut Department of Environmental Protection 2005, pp. 2-16-2-18; Maine Department of Inland Fisheries and Wildlife 2005, Chapter 5 p. 109; New Hampshire Fish and Game Department 2005, p. A210-212; Wisconsin Department of Natural Resources 2009, p. 1). The 2010 Census reported that the human population in the United States has increased almost 10 percent since 2000. The only State within the range of the northern leopard frog that did not have an increase in population is Michigan (Mackun and Wilson 2011, pp. 1-2). Nevada, Arizona, Utah, Texas, and Idaho were the fastest growing States, and New Hampshire and South Dakota were the fastest growing States in the northeast and Midwest, respectively. Pennsylvania ranks fifth in the nation in the amount of open space it loses to development every day and it has lost over half of its wetlands to development (Pennsylvania Game Commission and Pennsylvania Fish and Boat Commission 2005, pp. 10-34). In Canada, Ontario and Quebec are the largest provinces in terms of numbers of people; larger numbers of people typically contribute more to increases in urban development and modification of northern leopard frog habitats. Projected human population growth is also expected to result in increased needs for water (surface diversions and groundwater pumping) to support this growth (Deacon

et al.

2007, p. 688). This could decrease water availability for northern leopard frogs and thereby impact the amount and extent of habitat for northern leopard frogs. Reexamination of historic northern leopard frogs sites in northeastern Ohio (Orr

et al.

1998, p. 92) found that two sites had been destroyed by development and three had been eliminated by high-intensity agriculture. A study in Iowa and Wisconsin found a negative association with urban land use and relative abundance of northern leopard frogs (Knutson

et al.

1999, p. 1441; Knutson

et al.

2000, p. 140). From 1998 to 2004, 140,400 ac (56,800 ha) or 61 percent of wetland losses in the United States occurred due to urban and rural development (Dahl 2006, p. 47). These wetland losses are considered to be irreversible as they are the result of permanent construction (such as houses and roads) that alters wetland hydrology (Dahl 2006, pp. 47, 63). Urban development often results in conversion of natural habitats to homes, roads, and industrial uses, which can result in direct mortality from traffic (Mazerolle 2004, p. 47; Bouchard

et al.

2009, p. 23), chemical contamination of wetlands (Fahrig

et al.

1995, p. 177), and modification of existing wetland habitats to benefit sport fish rather than native amphibians (Knutson

et al.

1999, p. 1444).

Based upon the above information, urban development has likely resulted in the historical and continued loss of northern leopard frogs and their habitat throughout their range. While the magnitude of these impacts is conceivably high in localized areas, urbanization is not ubiquitous throughout the range of the northern leopard frog. General information about human population growth and associated urbanization cannot be extrapolated to support high magnitude threats throughout all portions of the range of the northern leopard frog. Further, despite urbanization trends, the northern leopard frog is apparently still considered to be widespread and common in the eastern United States and eastern Canada. Therefore, the best available scientific information indicates that urbanization does not constitute a significant threat to the northern leopard frog at the species level now, nor do we have indication that it will in the future.

Oil and Gas Development

Natural gas drilling is currently occurring in at least 25 States that have populations of northern leopard frogs. In 2007, there were 449,000 natural gas

wells in 32 States, which was a 30 percent increase from 2000; it is estimated that 32,000 new natural gas wells per year could be drilled by 2012 (Lustgarten 2008, p. 2). Examples of the increase in magnitude of drilling in the United States can be observed by the increase in approved permits in Wyoming and Pennsylvania. The first natural gas well in Sublette County, Wyoming, was drilled in 1939, and by 2008, 700 gas wells were producing natural gas on the Pinedale Anticline (a major gas field in Sublette County). In 2008, the Bureau of Land Management approved 4,400 more natural gas wells in Sublette County (Lustgarten 2008, p. 3). In Susquehanna County, Pennsylvania, there was a 27-fold increase in natural gas well permits from 2007 to 2009. Natural gas mining is also occurring in Canada, the world's third-largest producer and exporter of natural gas (Natural Resources Canada 2011, p. 1). However, we have minimal specific information assessing the overlap of occupied northern leopard frog habitats with planned oil and gas development operations for most of the range of the species.

The Powder River Basin in Wyoming and Montana and the San Juan Basin in Colorado and New Mexico, areas within the range of the northern leopard frog, currently have the highest coalbed methane (a natural gas) productions in the United States (Environmental Protection Agency 2004, p. 1-1). Possible impacts to northern leopard frogs associated with coalbed methane development may include discharge of contaminated water into breeding ponds, loss of spring flows related to groundwater withdrawals, discharge of extremely cold water into breeding habitats, discharge of water containing nonnative predatory fish in these same areas, and road-related mortality associated with increased use of roads or new roads to support the coalbed methane development (Allan 2002, pp. 5-8; Gore 2002, pp. 1-14; Noss and Wuethner 2002, pp. 1-20). Mining and oil and gas development may also lead to contamination of habitats (Spengler 2002, pp. 7-26; Smith 2003, pp. 26, 31). Domestic and stock tank waters have dried or become contaminated with gas in Wyoming's Powder Basin (Powder River Basin Resource Council 2009, p. 1). Although some States that have populations of the northern leopard frog are implementing wetland and riparian protections in connection with oil and gas drilling (Colorado Division of Wildlife 2009, p. 5), it is unclear if all States are implementing such measures and whether or not these measures have resulted in decreased impacts to northern leopard frogs.

Another area where there is information about oil and gas development activities in northern leopard frog habitats is the Marcellus Shale. The Marcellus Shale is a black shale formation extending underground from Ohio and West Virginia northeast into Pennsylvania and southern New York that contains natural gas reserves. Although there are areas where the Marcellus Shale is exposed at the surface, it is as deep as 7,000 ft (2,134 m) or more below the ground surface along the Pennsylvania border. Natural gas drilling operations have proliferated in Pennsylvania over the past years, and at least 1,415 new wells were drilled in 2010 (Goldberg 2011, p. 2). The drilling is expected to expand into Ohio and West Virginia. New York is currently conducting a comprehensive review of the potential environmental impacts associated with natural gas development and Ohio's State government approved drilling in Ohio's State parks on June 15, 2011.

Hydraulic fracturing is a method used to extract natural gas from the earth. Environmental concerns with hydraulic fracturing include water use and management, and the composition of the fluids used (Environmental Protection Agency 2011, p. 1). Hydraulic fracturing consists of pumping chemicals (such as benzene) and high volumes of water and sand down the well under high pressure to create fractures in the gas-bearing rock (New York Department of Environmental Conservation 2011, p. 1). The propping material holds the fractures open allowing more gas to flow into the well. The hydraulic fracturing of the Marcellus Shale will require large volumes of water to fracture the rocks and produce natural gas. In 2008, oil and gas wells disgorged approximately 9 million gallons of wastewater a day in Pennsylvania, and water use is expected to increase to at least 19 million gallons per day (Sapien 2009, p. 2).

The wastewater is a product of the hydraulic fracturing which pumps about 1 million gallons of water mixed with sand and chemicals into each well to withdraw the natural gas. When it comes back out, the water contains toxins and dissolved solids. Wastewater contains enough dissolved solids that the water can be five times as salty as sea water. Recent research found methane contamination of drinking water in Pennsylvania and New York from natural gas extraction on the Marcellus Shale (Osborn

et al.

2011, p. 2). In addition, water contamination has been documented near drilling areas in Sublette County, Wyoming, and Santa Fe, New Mexico; chemical spills of hydraulic fracturing chemicals have occurred in Colorado (Lustgarten 2008, pp. 2-9).

The rate, timing, and location of water withdrawals could result in negative impacts to streams, downstream riverine and riparian resources, wetlands, and aquifer supplies where hydraulic fracturing to mine natural gas occurs (New York Department of Environmental Conservation 2009, p. 6-4). The draft environmental impact statement for natural gas drilling in New York states, “Water for hydraulic fracturing may be obtained by withdrawing it from surface water bodies away from the well site or through wells drilled into groundwater aquifers” (New York Department of Environmental Conservation 2009, p. 6-4). The existence and sustainability of wetland habitats directly depend on the presence of water at or near the surface of the soil. The functioning of a wetland is driven by the inflow and outflow of surface water and groundwater. As a result, withdrawal of surface water or groundwater for high volume hydraulic fracturing could impact wetland resources and northern leopard frog habitat. These potential impacts depend on the amount of water within the wetland, the amount of water withdrawn from the catchment area of the wetland, and the dynamics of water flowing into and out of the wetland. Even small changes in the hydrology of the wetland can have significant impacts on the wetland plant community and on the wildlife, such as the northern leopard frog, that depend on the wetland. As discussed in the Biology section, wintering northern leopard frogs are intolerant of freezing, and withdrawals that reduce water depths in overwintering habitat could lead to high levels of winter kill if water levels are reduced so much that these areas freeze.

In summary, some northern leopard frog populations could be impacted by oil and gas development activities through changes to water quantity or quality (due to chemical pollution or increased salinity) and through insufficient water flow to maintain wetland and stream habitat. Natural gas drilling and hydraulic fracturing may occur across the range of the northern leopard frog; however, the impacts are expected to be localized population and habitat losses rather than regional or species-level effects. Pennsylvania, Ohio, West Virginia, Kentucky, Wyoming, Colorado, Montana, and New Mexico all have oil and gas development occurring within their

boundaries; however, we have little to no information about oil and gas development activities in northern leopard frog habitats throughout the rest of the range of the species, notably the Midwestern United States and Canada. Therefore, the best available scientific information indicates that oil and gas development does not constitute a significant threat to the northern leopard frog at the species level now, nor do we have indication that it will in the future.

Roads

Roads have been shown to pose barriers to northern leopard frog dispersal, to contribute to nonpoint source pollution, and to result in direct mortality of northern leopard frogs (Smith 2003, pp. 27, 38; Maxell 2000, p. 25; Fahrig

et al.

1995, pp. 177-182). The movements of adult northern leopard frogs to breeding habitats during spring rains and the extensive dispersal of juveniles from breeding ponds in late summer make this species vulnerable to highway traffic (Orr

et al.

1998, p. 93; Langen

et al.

2009, p. 111), and there are many reports of large amounts of leopard frog road mortality (see references in Carr and Fahrig 2001, p. 1075; Glista

et al.

2008, pp. 81-82; Langen

et al.

2009, p. 111). Road building is often tied to other activities such as urban, agricultural, and oil and gas development, so roads may impact leopard frogs directly and indirectly.

Bouchard

et al.

(2009, pp. 5-6) found that the northern leopard frog's inability to avoid roads and their slow movement make them particularly vulnerable to road mortality and that roads could thus result in negative effects to local population abundance. Other studies did not find any decreasing trends in abundance for amphibian roadside populations (Mazerolle 2004, p. 51). Traffic density within 0.9 mi (1.5 km) of occupied northern leopard frog habitat may have negatively affected local frog abundance, but it was unclear if results were due to the observed road mortality, pollution (

e.g.,

vehicle emissions, road runoff), or increased urbanization (Carr and Fahrig 2001, p. 1074). Other studies have also documented smaller amphibian populations in the vicinity of major roads and within landscapes with high road densities than populations where roads are distant and few (Langen

et al.

2009, p. 104). “Hotspots” for northern leopard frog road mortality tend to occur along causeways (road segments with water on either side) with wetland sites within 328 ft (100 m) of the road (Langen

et al.

2009, p. 110).

In summary, although research indicates that roadside populations of northern leopard frogs may be adversely impacted by roads and evidence shows that individual frogs are certainly impacted through road mortality, the information assessed indicates these impacts are localized and result in effects to local frog abundance, not population level impacts. While roads occur throughout the range of the northern leopard frog, the best available information does not suggest that roads constitute a significant threat to the northern leopard frog at the species level now, nor do we have indication that they will in the future.

Forest Management

The northern leopard frog is associated with forested as well as grassland or open areas (Blomquist and Hunter 2009, p. 150). Based upon broad land cover and use, forest management occurs in forested areas throughout the range of the northern leopard frog (USDA NRCS 2001). Timber harvest activities may impact northern leopard frog populations in several ways. Clearcuts (areas where all trees are removed) at breeding sites can result in enhanced tadpole development through increased water temperatures and food production (Semlitsch

et al.

2009, p. 859). However, clearcuts can also result in negative effects to juvenile and adult northern leopard frog movement due to higher surface temperatures (from canopy removal), and loss of soil-litter moisture in upland habitats surrounding breeding ponds, which affects the species' ability to move through these areas into post-breeding habitat (Maxell 2000, pp. 12-14; Smith 2003, p. 29; Semlitsch

et al.

2009, p. 860). Research on timber management and northern leopard frog seasonal habitat requirements found that northern leopard frogs in the late spring and summer used open, wet areas; frogs used unharvested forest for longer movements (Blomquist and Hunter 2009, p. 153). Forest management may affect local populations of northern leopard frogs by fragmenting habitats and reducing landscape connectivity.

Forest management has the potential to impact northern leopard frog breeding, dispersal, and foraging habitats in forested areas throughout its range. However, the information we reviewed does not indicate that forest management, clearcutting in particular, is occurring at a level or extent that would result in impacts at the species level. Therefore, the best available information indicates forest management is not a significant threat to the northern leopard frog at the species level now, nor do we have indication that it will in the future.

Groundwater Withdrawal

Throughout the range of the northern leopard frog, particularly in the western Uni

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