# Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for the Northern Mexican Gartersnake and Narrow-Headed Gartersnake

> Briefs, arguments, decisions, and more.

URL: https://www.frixlaw.com/law-library/documents/fr%3A2013-16520

## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** July 10, 2013
- **Citation:** 78 FR 41550

## Text

DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R2-ES-2013-0022; 4500030113]
RIN 1018-AZ35
Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for the Northern Mexican Gartersnake and Narrow-Headed Gartersnake

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Proposed rule.

SUMMARY:

We, the U.S. Fish and Wildlife Service, propose to designate critical habitat for the northern Mexican gartersnake (
Thamnophis eques megalops
) and narrow-headed gartersnake (
Thamnophis rufipunctatus
) in Arizona and New Mexico, under the Endangered Species Act of 1973, as amended (Act). If we finalize this rule as proposed, it would extend the Act's protections to these species' habitats. The effect of this regulation is to conserve northern Mexican and narrow-headed gartersnake habitat under the Act.

DATES:

We will accept comments received or postmarked on or before September 9, 2013. Comments submitted electronically using the Federal eRulemaking Portal (see
ADDRESSES
section, below) must be received by 11:59 p.m. Eastern Time on the closing date. We must receive requests for public hearings, in writing, at the address shown in the
FOR FURTHER INFORMATION CONTACT
section by August 26, 2013.

ADDRESSES:

You may submit comments by one of the following methods:

(1)
Electronically:
Go to the Federal eRulemaking Portal:
http://www.regulations.gov.
Search for Docket No. FWS-R2-ES-2013-0022, which is the docket number for this rulemaking. You may submit a comment by clicking on “Comment Now!”

(2)
By hard copy:
Submit by U.S. mail or hand-delivery to: Public Comments Processing, Attn: FWS-R2-ES-2013-0022; Division of Policy and Directives Management; U.S. Fish and Wildlife Service; 4401 N. Fairfax Drive, MS 2042-PDM; Arlington, VA 22203.

We request that you send comments only by the methods described above. We will post all comments on
http://www.regulations.gov.
This generally means that we will post any personal information you provide us (see the Information Requested section below for more information).

The coordinates or plot points or both from which the critical habitat maps are generated are included in the administrative record for this rulemaking and are available at
http://www.fws.gov/southwest/es/arizona, http://www.regulations.gov
at Docket No. FWS-R2-ES-2013-0022, and at the Arizona Ecological Services Field Office (see
FOR FURTHER INFORMATION CONTACT
). Any additional tools or supporting information that we may develop for this rulemaking will also be available at the Fish and Wildlife Service Web site and Field Office set out above, and may also be included in the preamble of this proposal and/or at
http://www.regulations.gov.

FOR FURTHER INFORMATION CONTACT:

Steve Spangle, Field Supervisor, U.S. Fish and Wildlife Service, Arizona Ecological Services Field Office, 2321 West Royal Palm Road, Suite 103, Phoenix, AZ 85021; telephone: 602-242-0210; facsimile: 602-242-2513. If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Executive Summary

Why we need to publish a rule.
Under the Act, once a species is determined to be an endangered or threatened species throughout all or a significant portion of its range, we are required to promptly publish a proposal in the
Federal Register
and make a determination on our proposal within 1 year. Additionally, critical habitat shall be designated, to the maximum extent prudent and determinable, for any species determined to be an endangered or threatened species under the Act. Designations and revisions of critical habitat can only be completed by issuing a rule. Elsewhere in today's
Federal Register
, we propose to list the northern Mexican and narrow-headed gartersnakes as threatened species under the Act.

This rule consists of:
A proposed rule for designation of critical habitat for northern Mexican and narrow-headed gartersnakes. These gartersnakes are proposed for listing under the Act. This rule proposes designation of critical habitat necessary for the conservation of the species.

The basis for our action.
Under the Act, when a species is proposed for listing, to the maximum extent prudent and determinable, we must designate critical habitat for the species. These species are proposed for listing as threatened. Therefore, we propose to designate critical habitat for the northern Mexican gartersnake in Greenlee, Graham, Apache, La Paz, Mohave, Yavapai, Navajo, Gila, Coconino, Cochise, Santa Cruz, Pima, and Pinal Counties in Arizona, as well as in Grant and Catron Counties in New Mexico, and critical habitat for the narrow-headed gartersnake in Greenlee, Graham, Apache, Yavapai, Navajo, Gila, and Coconino Counties in Arizona, as well as in Grant, Hidalgo, Sierra, and Catron Counties in New Mexico.

We will seek peer review.
We are seeking comments from knowledgeable individuals with scientific expertise to review our analysis of the best available science and application of that science and to provide any additional scientific information to improve this proposed rule. Because we will consider all comments and information received during the comment period, our final determinations may differ from this proposal.

Information Requested

We intend that any final action resulting from this proposed rule will be based on the best scientific and commercial data available and be as accurate and as effective as possible. Therefore, we request comments or information from other concerned governmental agencies, Native American tribes, the scientific community, industry, or any other interested parties concerning this proposed rule. We particularly seek comments concerning:

(1) The reasons why we should or should not designate habitat as “critical habitat” under section 4 of the Act (16 U.S.C. 1531
et seq.
), including whether there are threats to the species from human activity, the degree of which can be expected to increase due to the designation, and whether that increase in threats outweighs the benefit of designation such that the designation of critical habitat is not prudent.

(2) Specific information on:

(a) The amount and distribution of northern Mexican or narrow-headed gartersnakes and their habitat;

(b) What may constitute “physical or biological features essential to the conservation of the species,” within the geographical range currently occupied by the species;

(c) Where these features are currently found;

(d) Whether any of these features may require special management considerations or protection;

(e) What areas, that were occupied at the time of listing (or are currently occupied) and that contain features

essential to the conservation of the species, should be included in the designation and why; and

(f) What areas not occupied at the time of listing are essential for the conservation of the species and why.

(3) Land use designations and current or planned activities in the areas occupied by the species or proposed to be designated as critical habitat, and possible impacts of these activities on this species and proposed critical habitat.

(4) Any foreseeable economic, national security, or other relevant impacts that may result from designating any area that may be included in the final designation. We are particularly interested in any impacts on small entities, and the benefits of including or excluding areas from the proposed designation that are subject to these impacts.

(5) Whether our approach to designating critical habitat could be improved or modified in any way to provide for greater public participation and understanding, or to assist us in accommodating public concerns and comments.

(6) The likelihood of adverse social reactions to the designation of critical habitat and how the consequences of such reactions, if likely to occur, would relate to the conservation and regulatory benefits of the proposed critical habitat designation.

(7) If considered for exclusion from critical habitat designation under section 4(b)(2) of the Act, documentation that describes how lands are managed for wildlife and habitat and how that management specifically benefits either or both the northern Mexican or narrow-headed gartersnake or their prey bases.

Please include sufficient information with your submission (such as scientific journal articles or other publications) to allow us to verify any scientific or commercial information you include.

Please note that submissions merely stating support for or opposition to the action under consideration without providing supporting information, although noted, will not be considered in making a determination, as section 4(b)(1)(A) of the Act directs that determinations as to whether any species is an endangered or threatened species must be made “solely on the basis of the best scientific and commercial data available.”

You may submit your comments and materials concerning this proposed rule by one of the methods listed in the
ADDRESSES
section. We request that you send comments only by the methods described in the
ADDRESSES
section.

If you submit information via
http://www.regulations.gov,
your entire submission—including any personal identifying information—will be posted on the Web site. If your submission is made via a hardcopy that includes personal identifying information, you may request at the top of your document that we withhold this information from public review. However, we cannot guarantee that we will be able to do so. We will post all hardcopy submissions on
http://www.regulations.gov.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on
http://www.regulations.gov,
or by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, Arizona Ecological Services Field Office (see
FOR FURTHER INFORMATION CONTACT
).

Previous Federal Actions

All previous Federal actions are described in the proposal to list the northern Mexican and narrow-headed gartersnakes as threatened species under the Act published elsewhere in today's
Federal Register
.

Background

Critical habitat is defined in section 3 of the Act as:

(1) The specific areas within the geographical area occupied by the species, at the time it is listed in accordance with the Act, on which are found those physical or biological features

(a) Essential to the conservation of the species and

(b) Which may require special management considerations or protection; and

(2) Specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.

Conservation, as defined under section 3 of the Act, means to use and the use of all methods and procedures that are necessary to bring an endangered or threatened species to the point at which the measures provided pursuant to the Act are no longer necessary. Such methods and procedures include, but are not limited to, all activities associated with scientific resources management such as research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping, and transplantation, and, in the extraordinary case where population pressures within a given ecosystem cannot be otherwise relieved, may include regulated taking.

Critical habitat receives protection under section 7 of the Act through the requirement that Federal agencies ensure, in consultation with the Service, that any action they authorize, fund, or carry out is not likely to result in the destruction or adverse modification of critical habitat. The designation of critical habitat does not affect land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation area. Such designation does not allow the government or public to access private lands. Such designation does not require implementation of restoration, recovery, or enhancement measures by non-Federal landowners. Where a landowner requests Federal agency funding or authorization for an action that may affect a listed species or critical habitat, the consultation requirements of section 7(a)(2) of the Act would apply, but even in the event of a destruction or adverse modification finding, the obligation of the Federal action agency and the landowner is not to restore or recover the species, but to implement reasonable and prudent alternatives to avoid destruction or adverse modification of critical habitat.

Under the first prong of the Act's definition of critical habitat, areas within the geographic area occupied by the species at the time it was listed are included in a critical habitat designation if they contain physical or biological features (1) which are essential to the conservation of the species and (2) which may require special management considerations or protection. For these areas, critical habitat designations identify, to the extent known using the best scientific and commercial data available, those physical or biological features that are essential to the conservation of the species (such as space, food, cover, and protected habitat). In identifying those physical and biological features within an area, we focus on the principal biological or physical constituent elements (primary constituent elements such as roost sites, nesting grounds, seasonal wetlands, water quality, tide, soil type, etc.) that are essential to the conservation of the species. Primary constituent elements are the elements of physical or biological features that, when laid out in the appropriate quantity and spatial arrangement to provide for a species' life-history processes, are essential to the conservation of the species.

Under the second prong of the Act's definition of critical habitat, we can designate critical habitat in areas outside the geographic area occupied by

the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species. For example, an area currently occupied by the species, but that was not occupied at the time of listing, may be essential to the conservation of the species and may be included in the critical habitat designation. We designate critical habitat in areas outside the geographic area occupied by a species only when a designation limited to its range would be inadequate to ensure the conservation of the species.

Section 4 of the Act requires that we designate critical habitat on the basis of the best scientific data available. Further, our Policy on Information Standards Under the Endangered Species Act (published in the
Federal Register
on July 1, 1994 (59 FR 34271)), the Information Quality Act (section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 106-554; H.R. 5658)), and our associated Information Quality Guidelines, provide criteria, establish procedures, and provide guidance to ensure that our decisions are based on the best scientific data available. They require our biologists, to the extent consistent with the Act and with the use of the best scientific data available, to use primary and original sources of information as the basis for recommendations to designate critical habitat.

When we are determining which areas should be designated as critical habitat, our primary source of information is generally the information developed during the listing process for the species. Additional information sources may include the recovery plan for the species, articles in peer-reviewed journals, conservation plans developed by States and counties, scientific status surveys and studies, biological assessments, other unpublished materials, or experts' opinions or personal knowledge.

Habitat is dynamic, and species may move from one area to another over time. We recognize that critical habitat designated at a particular point in time may not include all of the habitat areas that we may later determine are necessary for the recovery of the species. For these reasons, a critical habitat designation does not signal that habitat outside the designated area is unimportant or may not be needed for recovery of the species. Areas that are important to the conservation of the species, both inside and outside the critical habitat designation, will be subject to: (1) Conservation actions implemented under section 7(a)(1) of the Act, (2) regulatory protections afforded by the requirement in section 7(a)(2) of the Act for Federal agencies to ensure their actions are not likely to jeopardize the continued existence of any endangered or threatened species, and (3) the prohibitions of section 9 of the Act if actions occurring in these areas may affect the species. Federally funded or permitted projects affecting listed species outside their designated critical habitat areas may still result in jeopardy findings in some cases. These protections and conservation tools will continue to contribute to recovery of this species. Similarly, critical habitat designations made on the basis of the best available information at the time of designation will not control the direction and substance of future recovery plans, habitat conservation plans (HCPs), or other species conservation planning efforts if new information available at the time of these planning efforts calls for a different outcome.

Prudency Determination

Section 4(a)(3) of the Act, as amended, and implementing regulations (50 CFR 424.12), require that, to the maximum extent prudent and determinable, the Secretary shall designate critical habitat at the time the species is determined to be an endangered or threatened species. Our regulations (50 CFR 424.12(a)(1)) state that the designation of critical habitat is not prudent when one or both of the following situations exist:

(1) The species is threatened by taking or other human activity, and identification of critical habitat can be expected to increase the degree of threat to the species, or

(2) Such designation of critical habitat would not be beneficial to the species.

There is currently no imminent threat of take attributed to collection or vandalism for either of these species, and identification and mapping of critical habitat is not expected to initiate any such threat. In the absence of finding that the designation of critical habitat would increase threats to a species, if there are any benefits to a critical habitat designation, then a prudent finding is warranted. Here, the potential benefits of designation include: (1) Triggering consultation under section 7 of the Act, in new areas for actions in which there may be a Federal nexus where it would not otherwise occur because, for example, it is or has become unoccupied or the occupancy is in question; (2) focusing conservation activities on the most essential features and areas; (3) providing educational benefits to State or county governments or private entities; and (4) preventing people from causing inadvertent harm to the species. Therefore, because we have determined that the designation of critical habitat would not likely increase the degree of threat to the species and may provide some measure of benefit, we find that designation of critical habitat is prudent for the northern Mexican and narrow-headed gartersnakes.

Critical Habitat Determinability

Having determined that designation is prudent, under section 4(a)(3) of the Act, we must find whether critical habitat for the northern Mexican and narrow-headed gartersnakes is determinable. Our regulations at 50 CFR 424.12(a)(2) state that critical habitat is not determinable when one or both of the following situations exist:

(i) Information sufficient to perform required analyses of the impacts of the designation is lacking, or

(ii) The biological needs of the species are not sufficiently well known to permit identification of an area as critical habitat. When critical habitat is not determinable, the Act allows the Service an additional year to publish a critical habitat designation (16 U.S.C. 1533(b)(6)(C)(ii)).

We reviewed the best available scientific and commercial information pertaining to the biological needs of the species and habitat characteristics where the species are located. Based on this information, we conclude that sufficient information is known regarding the species' needs and habitats to determine critical habitat for the northern Mexican and narrow-headed gartersnakes.

Physical or Biological Features

In accordance with section 3(5)(A)(i) and 4(b)(1)(A) of the Act and regulations at 50 CFR 424.12, in determining which areas within the geographic area occupied by the species at the time of listing to designate as critical habitat, we consider the physical or biological features that are essential to the conservation of the species and which may require special management considerations or protection. These include, but are not limited to:

(1) Space for individual and population growth and for normal behavior;

(2) Food, water, air, light, minerals, or other nutritional or physiological requirements;

(3) Cover or shelter;

(4) Sites for breeding, reproduction, or rearing (or development) of offspring; and

(5) Habitats that are protected from disturbance or are representative of the historical, geographic, and ecological distributions of a species.

We derived the specific physical or biological features (PBFs) required for the northern Mexican and narrow-headed gartersnakes from the best available scientific and commercial information available, including research of these species' habitat, ecology, and life history as described below. Additional insight is provided by Rosen and Schwalbe (1988, pp. 14-48), Degenhardt
et al.
(1996, pp. 317-319, 326-328), Rossman
et al.
(1996, pp. 55-116, 171-177, 241-248), and Ernst and Ernst (2003, pp. 391-393, 416-419). We have determined that the following physical or biological features are essential for northern Mexican and narrow-headed gartersnakes:

Space and Physical Habitat Requirements for Individual and Population Growth and for Normal Behavior

Both the northern Mexican and narrow-headed gartersnakes depend on the presence of water, primarily for the maintenance of their primary aquatic prey bases, not because their own physiology requires an aquatic environment. The northern Mexican gartersnake is a riparian obligate and occurs chiefly in streams, rivers, cienegas, stock tanks, and spring sources that are often found within large-river riparian woodlands and forests and streamside gallery forests (defined as well-developed broadleaf deciduous riparian forests with limited, if any, herbaceous ground cover or dense grass) (Hendrickson and Minckley 1984, p. 131; Rosen and Schwalbe 1988, pp. 14-16; Arizona Game and Fish Department 2001, p. 2). Northern Mexican gartersnakes occur at elevations from 130 to 8,497 feet (ft) (40 to 2,590 meters (m)) (Rossman
et al.
1996, p. 172), and in a wide range of biotic communities, including Sonoran Desertscrub at the lower elevations, through Semidesert Grassland, Interior Chaparral, and Madrean Evergreen Woodland and into the lower reaches of Petran Montane Conifer Forest as elevation increases (Brennan and Holycross 2006, p. 122). Narrow-headed gartersnakes are widely considered to be one of the most aquatic gartersnake species (Rossman et al. 1996, p. 246), and are strongly associated with clear, rocky streams, using predominantly pool and riffle habitat that includes cobbles and boulders (Rosen and Schwalbe 1988, pp. 33-34; Degenhardt
et al.
1996, p. 327; Rossman
et al.
1996, p. 246). Narrow-headed gartersnakes occur at elevations from approximately 2,300-8,200 ft (700 m-2,500 m), inhabiting Petran Montane Conifer Forest, Great Basin Conifer Woodland, Interior Chaparral, and the Arizona Upland subdivision of Sonoran Desertscrub communities (Rosen and Schwalbe 1988, p. 33; Brennan and Holycross 2006, p. 122; Burger 2008).

Northern Mexican gartersnakes employ a variety of strategies when foraging for prey. Rosen and Schwalbe (1988, p. 21) observed: (1) Aquatic and terrestrial ambush; (2) aquatic foraging in riffles, vegetation mats, and in open water (such as pool habitat, stock tanks, etc.); and (3) opportunistic capitalization on transitory concentrations of prey. These observations suggest that areas with slow riffles, pools, and backwater habitat are important for prey acquisition, because the prey of northern Mexican gartersnakes are largely aquatic and the snakes themselves need to remain somewhat stabilized to allow for striking behaviors. Narrow-headed gartersnakes often forage underwater, using concealment and ambush behaviors within and between boulder and cobble complexes along the bottom of streams (Rosen and Schwalbe 1988; p. 39). Hibbitts and Fitzgerald (2005, p. 364) described their hunting technique in greater detail, which included anchoring their body with their tail around rocks on the bottom of streams and orienting themselves in position with the current, with their head and neck exposed to the force of the water and the body unanchored on the substrate to allow for forward directed strikes. Narrow-headed gartersnakes are believed to be mainly visual hunters (Hibbitts and Fitzgerald 2005, p. 364) and heavily dependent on visual cues when foraging, based on comparative analyses among other species of gartersnakes (de Queiroz 2003, p. 381). However, foraging activity that occurs during the monsoon season, which is characterized by turbid water conditions, suggests they also use chemosensory abilities to direct strikes. This information suggests that the presence of rock structure along the bottom of streams is important to narrow-headed gartersnakes in compensating for the inertia of flow and for providing opportunities for camouflage-based ambush. However, Fitzgerald (1986; Table 4) also found narrow-headed gartersnakes foraging in stream and river reaches characterized as having sandy substrates. These observations suggest a more opportunistic nature of foraging behavior that may be based more on the presence of prey than the type of substrate.

Both northern Mexican and narrow-headed gartersnakes are largely dependent on native fish as a primary source of food, but have been observed using nonnative, soft-rayed fish species as prey on occasion; for narrow-headed gartersnakes, fish are the principle prey item (Rosen and Schwalbe 1988, pp. 18, 38-39; Degenhardt
et al.
1996, p. 328; Rossman
et al.
1996, p. 247; Nowak 2006, p. 22). Therefore, habitat-based attributes that are important for the survival of fish prey species are equally important for the survival of northern Mexican and narrow-headed gartersnakes. Many species of native and nonnative soft-rayed fish require unregulated flows (or flooding) for: (1) Removing excess sediment from some portions of the stream; (2) removing predatory nonnative, spiny-rayed fish species from a given area; and (3) increasing prey species diversity. Flows fluctuate seasonally, with snowmelt causing spring pulses and occasional floods, and late-summer or monsoonal rains producing floods of varying intensity and duration. These high flows likely rejuvenate spawning and foraging habitat for native and nonnative, soft-rayed fish (Propst
et al.
1986, p. 3), break-up embedded bottom materials (Mueller 1984, p. 355), stimulate spawning, and enhance recruitment of native species by eliminating or reducing populations of harmful nonnative species (Stefferud and Rinne 1996a, p. 80), such as spiny-rayed fish. Flooding also allows for the scouring of sand and gravel in riffle areas, which reduces the degree of embeddedness of cobble and boulder substrates (Britt 1982, p. 45). Typically, sediment is carried along the bed of a stream and deposited at the downstream, undersurface side of cobbles and boulders. Over time, this can result in the filling of cavities under cobbles and boulders (Rinne 2001, p. 69). Flooding removes the extra sediment, and the cavities created under cobbles by the scouring action of the flood waters provide enhanced opportunities for spawning of native fish, as well as foraging opportunities, particularly for narrow-headed gartersnakes.

In addition to aquatic habitat, northern Mexican and narrow-headed gartersnakes rely on terrestrial habitat for thermoregulation, gestation, shelter, protection from predators, immigration, emigration, and brumation (cold-season dormancy). The northern Mexican gartersnake also uses terrestrial habitat for foraging opportunities when primary prey items, such as leopard frogs and

native fish, are uncommon or absent from aquatic habitats. Rosen (1991, pp. 308-309) found that northern Mexican gartersnakes spent approximately 60 percent of their time moving, 13 percent of their time basking on vegetation, 18 percent of their time basking on the ground, and 9 percent of their time under surface cover. Foraging may occur spontaneously and opportunistically during any of these behaviors. In studying the Mexican gartersnake, Drummond and Marcías-García (1983, pp. 24, 35) found individuals wandering hundreds of meters away from water, perhaps in response to a decline or disappearance of the prey base. Observation records for northern Mexican gartersnakes from semi-remote livestock tanks and spring sources suggest the species moves across the local landscape as part of its foraging ecology. Rosen and Schwalbe (1988, p. 47) suggested that vegetation such as knotgrass, deergrass, sacaton, cattails, tules, and spikerush were important to the northern Mexican gartersnake, as well as the presence of rock piles. Boyarski (2011, p. 3) found that four of five telemetered northern Mexican gartersnakes over-wintered along a hillside “immediately south” of hatchery ponds where they spent the majority of their time during the surface-active season, but the distance of those specific over-wintering sites was not disclosed. However, Rosen and Schwalbe (1988, p. 27) report observing northern Mexican gartersnakes at a distance of 330 ft (100 m) away from permanent water.

Important terrestrial habitat components for the narrow-headed gartersnake include cobbles, boulders, and bankside shrub vegetation for basking and foraging (Fleharty 1967, pp. 215-216; Rosen and Schwalbe 1988, p. 48; Ernst and Ernst 2003, p. 418). In the Black River and Oak Creek in Arizona, the majority of narrow-headed gartersnakes captured were observed under rocks or shoreline debris, which may indicate these habitat components are ecologically important (Brennan and Rosen 2009, pp. 7, 11). In order of preference, Jennings and Christman (2011, pp. 14, 20) found that narrow-headed gartersnakes used rocks, logs or stumps, and debris jams as cover. Narrow-headed gartersnake detections appear to correlate with the presence of large willows growing along the streambank, which are used for basking (Fernandez and Rosen 1996, p. 70). Holycross
et al.
(2006, p. 51) found that willows overhanging the stream channel are particularly important for adult narrow-headed gartersnakes. The greater need of narrow-headed gartersnakes to thermoregulate at higher elevations makes optimal basking sites, such as shrubs and snags, essential (Rosen and Schwalbe 1988, p. 34). Pregnant female narrow-headed gartersnakes are rarely encountered near streams, apparently moving away from water during gestation, in favor of the higher thermal environs of rock piles (Rosen and Schwalbe 1988, pp. 33-34, 48). Telemetry data presented in Nowak (2006, pp. 17-18) suggest that terrestrial habitat is important to narrow-headed gartersnakes; home ranges were often set up perpendicular to the stream channel, while others were parallel to the channel. This orientation of home ranges likely indicates the species uses both active and inactive channels, depending on the activity. Such channels are typically found within 600 ft (182.9 m) of active stream channels. For example, it is ecologically disadvantageous for an individual gartersnake to brumate within the bankfull boundary of an active stream because of the risk of flooding, and subsequent drowning, during the cold-season dormancy period. This hypothesis is supported by the findings of Nowak (2006, pp. 19-21), which found telemetered narrow-headed gartersnakes using crevices in rock walls or large rock outcrops as over-wintering sites, some as far as 650 ft (200 m) away from the stream channel. Additionally, micro-sites chosen as cover for gartersnakes may be artificial or natural; Nowak (2006, p. 19) reported observing narrow-headed gartersnakes commonly using such items such as rock foundations and retaining walls, chimneys, and old water pipes under house foundations, vegetation thickets, burrows, boulders, and downed logs. The largest home range documented by Jennings and Christman (2011, p. 18) for narrow-headed gartersnakes was 239,077 square feet (22,211 square meters), but home range sizes in this study were considered to be underestimated by the authors.

Therefore, based on the information above, we identify the presence of aquatic habitats to support individual and population growth, and support normal behavior, and the presence of terrestrial habitats in appropriate proximity to occupied aquatic habitats to support individual and population growth, and support normal behavior, to be physical or biological features for these species.

Biotic Community Requirements for Individual and Population Growth

The success of northern Mexican and narrow-headed gartersnake populations appears to be uniquely tied to the presence of adequate native prey populations, and, in some cases, nonnative prey species consisting of larval and juvenile bullfrogs, as well as soft-rayed, nonnative fish species (Rosen and Schwalbe 1988, pp. 18, 20, 44; Holycross
et al.
2006, p. 23). Generally, the diet of the northern Mexican gartersnake consists predominantly of amphibians and fishes, but other invertebrates and vertebrate species may also be used opportunistically (Gregory
et al.
1980, pp. 87, 90-92; Rosen and Schwalbe 1988, pp. 18, 20; Holm and Lowe 1995, pp. 30-31; Degenhardt
et al.
1996, p. 318; Rossman
et al.
1996, p. 176; Manjarrez 1998). Marcías-García and Drummond (1988, pp. 129-134) found that adult northern Mexican gartersnakes in Hidalgo, Mexico, primarily fed on aquatic vertebrates, whereas juveniles often fed on invertebrates, such as earthworms and leeches. Narrow-headed gartersnakes specialize on fish (primarily native fish and, secondarily, nonnative, soft-rayed species, such as trout) as their principle prey item (Rosen and Schwalbe 1988, pp. 38-39; Nowak 2006, pp. 22-23; Degenhardt
et al.
1996, p. 328; Rossman
et al.
1996, p. 247). Detailed information on the diet of northern Mexican and narrow-headed gartersnakes is presented in the proposed rule to list both species as threatened under the Act, which is published elsewhere in today's
Federal Register
.

Both the northern Mexican and narrow-headed gartersnakes have been documented as highly vulnerable to effects from nonnative species as a result of their competition with gartersnakes for prey and effects from direct predation on the gartersnakes themselves (Rosen and Schwalbe 1988, pp. 28-31, 32, 44-45). We conducted a broad review of all available scientific and commercial data, and have determined that nonnative species, such as bullfrogs, crayfish, and spiny-rayed fish, in the families Centrarchidae and Ictaluridae, continue to be the most significant threat to northern Mexican and narrow-headed gartersnakes throughout their respective ranges. Our analysis of the roles that the declines in the anuran prey base, declines in the native fish prey base, bullfrog predation, crayfish interactions, and effects from nonnative, spiny-rayed fish play with regard to the observed declines of the northern Mexican and narrow-headed gartersnakes is presented in detail in the proposed rule to list both species as threatened under the Act, which is

published elsewhere in today's
Federal Register
.

Primary Constituent Elements for Northern Mexican and Narrow-Headed Gartersnakes

Under the Act and its implementing regulations, we are required to identify the physical or biological features essential to the conservation of northern Mexican and narrow-headed gartersnakes in areas occupied at the time of listing, focusing on the features' primary constituent elements (PCEs). We consider primary constituent elements to be the elements of physical or biological features that provide for a species' life-history processes and are essential to the conservation of the species.

Northern Mexican Gartersnake's PCEs

Based on our current knowledge of the physical or biological features and habitat characteristics required to sustain the species' life-history processes, we determine that the primary constituent elements specific to northern Mexican gartersnakes are:

(1) Aquatic or riparian habitat that includes:

a. Perennial or spatially intermittent streams of low to moderate gradient that possess appropriate amounts of in-channel pools, off-channel pools, or backwater habitat, and that possess a natural, unregulated flow regime that allows for periodic flooding or, if flows are modified or regulated, a flow regime that allows for adequate river functions, such as flows capable of processing sediment loads; or

b. Lentic wetlands such as livestock tanks, springs, and cienegas; and

c. Shoreline habitat with adequate organic and inorganic structural complexity to allow for thermoregulation, gestation, shelter, protection from predators, and foraging opportunities (e.g., boulders, rocks, organic debris such as downed trees or logs, debris jams, small mammal burrows, or leaf litter); and

d. Aquatic habitat with characteristics that support a native amphibian prey base, such as salinities less than 5 parts per thousand, pH greater than or equal to 5.6, and pollutants absent or minimally present at levels that do not affect survival of any age class of the northern Mexican gartersnake or the maintenance of prey populations.

(2) Adequate terrestrial space (600 ft (182.9 m) lateral extent to either side of bankfull stage) adjacent to designated stream systems with sufficient structural characteristics to support life-history functions such as gestation, immigration, emigration, and brumation (extended inactivity).

(3) A prey base consisting of viable populations of native amphibian and native fish species.

(4) An absence of nonnative fish species of the families Centrarchidae and Ictaluridae, bullfrogs (
Lithobates catesbeianus
), and/or crayfish (
Orconectes virilis, Procambarus clarki,
etc.), or occurrence of these nonnative species at low enough levels such that recruitment of northern Mexican gartersnakes and maintenance of viable native fish or soft-rayed, nonnative fish populations (prey) is still occurring.

Narrow-Headed Gartersnake's PCEs

Based on our current knowledge of the physical or biological features and habitat characteristics required to sustain the species' life-history processes, we determine that the primary constituent elements specific to narrow-headed gartersnakes are:

(1) Stream habitat, which includes:

a. Perennial or spatially intermittent streams with sand, cobble, and boulder substrate and low or moderate amounts of fine sediment and substrate embeddedness, and that possess appropriate amounts of pool, riffle, and run habitat to sustain native fish populations;

b. A natural, unregulated flow regime that allows for periodic flooding or, if flows are modified or regulated, a flow regime that allows for adequate river functions, such as flows capable of processing sediment loads;

c. Shoreline habitat with adequate organic and inorganic structural complexity (e.g., boulders, cobble bars, vegetation, and organic debris such as downed trees or logs, debris jams), with appropriate amounts of shrub- and sapling-sized plants to allow for thermoregulation, gestation, shelter, protection from predators, and foraging opportunities; and

d. Aquatic habitat with no pollutants or, if pollutants are present, levels that do not affect survival of any age class of the narrow-headed gartersnake or the maintenance of prey populations.

(2) Adequate terrestrial space (600 ft (182.9 m) lateral extent to either side of bankfull stage) adjacent to designated stream systems with sufficient structural characteristics to support life-history functions such as gestation, immigration, emigration, and brumation.

(3) A prey base consisting of viable populations of native fish species or soft-rayed, nonnative fish species.

(4) An absence of nonnative fish species of the families Centrarchidae and Ictaluridae, bullfrogs (
Lithobates catesbeianus
), and/or crayfish (
Orconectes virilis, Procambarus clarki,
etc.), or occurrence of these nonnative species at low enough levels such that recruitment of narrow-headed gartersnakes and maintenance of viable native fish or soft-rayed, nonnative fish populations (prey) is still occurring.

Special Management Considerations or Protection

When designating critical habitat, we assess whether the specific areas within the geographic area occupied by the species at the time of listing contain features which are essential to the conservation of the species and which may require special management considerations or protection.

All areas proposed for designation as critical habitat will require some level of management to address the current and future threats to northern Mexican and narrow-headed gartersnakes and to maintain or restore the PCEs. Special management within proposed critical habitat will be needed to ensure these areas provide adequate water quantity, quality, and permanence or near permanence; cover (particularly in the presence of harmful nonnative species); an adequate prey base; and absence of or low numbers of harmful nonnative species that can affect population persistence. Activities that may be considered adverse to the conservation benefits of proposed critical habitat include those which: (1) Completely dewater or reduce the amount of water to unsuitable levels in proposed critical habitat; (2) result in a significant reduction of protective cover within proposed critical habitat when harmful nonnative species are present; (3) remove or significantly alter structural terrestrial features of proposed critical habitat that alter natural behaviors such as thermoregulation, brumation, gestation, and foraging; (4) appreciably diminish the prey base; and (5) directly promote increases in harmful nonnative species populations or result in the introduction of harmful nonnative species.

Common examples of these activities may include, but are not limited to, various types of development, channelization, diversions, road construction, erosion control, bank stabilization, wastewater discharge, enhancement or expansion of human recreation opportunities, fish community renovations, and stocking of nonnative, spiny-rayed fish species or promotion of policies that directly or indirectly introduce harmful nonnative species as bait.

The activities listed above are just a subset of examples that have the

potential to affect critical habitat and PCEs if they are conducted within designated units; however, some of these activities, when conducted appropriately, may be compatible with maintenance of adequate PCEs.

Criteria Used To Identify Critical Habitat

As required by section 4(b)(2) of the Act, we use the best scientific data available to designate critical habitat. We review available information pertaining to the habitat requirements of the species. In accordance with the Act and its implementing regulation at 50 CFR 424.12(e), we consider whether designating additional areas—outside those currently occupied as well as those occupied at the time of listing—are necessary to ensure the conservation of the species. We are not currently proposing to designate any areas outside the geographic area considered occupied by the northern Mexican or narrow-headed gartersnake because occupied areas are distributed in several subbasins and currently provide a distribution and configuration of habitat areas sufficient for the conservation of these species.

To identify areas proposed for critical habitat for the northern Mexican and narrow-headed gartersnakes, we used a variety of sources which included riparian species survey reports, museum records, heritage data from State wildlife agencies, peer-reviewed literature, agency reports, interviews with species experts, and regional Geographic Information System (GIS) coverages. Some information sources were used heavily in determining the current and historical distributions of northern Mexican and narrow-headed gartersnakes such as Fitzgerald (1986, entire), Rosen and Schwalbe (1988, entire), Rosen
et al.
(2001, entire), and Holycross
et al.
(2006, entire), as they comprise the majority of rangewide survey information for these species. Hellekson (2012a, pers. comm.) was an important source of information pertaining to narrow-headed gartersnake status in New Mexico. In addition to reviewing gartersnake-specific survey reports, we also focused on survey reports for fish and amphibians as they captured important data on the existing community ecology that affects the status of these gartersnakes within their range.

Critical habitat for both gartersnake species is being proposed in areas considered currently occupied. Survey information for both species is significantly lacking in many streams, and both species of gartersnake are cryptic, secretive, difficult to detect, quick to escape underwater, and capable of persisting in low or very low population densities that make positive detections nearly impossible in structurally complex habitat. Therefore, we considered factors such as the date of the last known records of either species in an area, as well as records of one or more native prey species. We used all records for each species that were dated 1980 or later because the 1980s marked the first systematic survey efforts for these species across their ranges (see Rosen and Schwalbe (1988, entire) and Fitzgerald (1986, entire)) and previous records were often dated several decades prior and may not as accurately represented the likelihood for occupation in current times. Additionally, in evaluating whether a site should be considered currently occupied by these gartersnake species, a record of a native prey species suggests that a source of prey may still be available to gartersnakes in areas invaded by harmful nonnative species. This provides evidence that either gartersnake may still likely occur in a given area if other sensitive, native, aquatic or riparian species are also present, despite limited or negative survey data. Specifically, for both species, we considered a stream or geographic area as occupied if it is within the historical range of the species, contains suitable habitat, and meets both of the following: (1) Has a last known record for either species dated 1980 or later, and (2) has at least one native prey species also present.

The shape, size, and scope of proposed critical habitat can be evaluated in terms of its length (number of stream miles), width (lateral extent, in feet), or area (number of acres). With respect to length (in proposed designations based on flowing streams), the proposed areas were designed to provide sufficient aquatic and terrestrial habitat for normal behaviors of northern Mexican and narrow-headed gartersnakes of all age classes. In addition, with respect to width, we evaluated the lateral extent (terrestrial space) necessary to support the PCEs for northern Mexican and narrow-headed gartersnakes. The resulting designations take into account the naturally dynamic nature of riverine systems, floodplains, and riparian habitat (including adjacent upland areas) that are an integral part of these gartersnakes' ecology. For example, riparian areas are seasonally flooded habitats (i.e., wetlands) that are major contributors to a variety of functions vital to the gartersnakes' fish prey base within the associated stream channel (Brinson
et al.
1981, pp. 2-61, 2-69, 2-72, 2-75, 2-84 through 2-85; Federal Interagency Stream Restoration Working Group 1998, p. 2-61). Riparian areas filter runoff, absorb and gradually release floodwaters, recharge groundwater, maintain streamflow, protect stream banks from erosion, and provide shade and cover for fish and other aquatic species; all of these functions contribute to the physical quality of gartersnake habitat.

Healthy riparian and adjacent upland areas help ensure water courses maintain the habitat important for aquatic species (e.g., see USFS 1979, pp. 18, 109, 158, 264, 285, 345; Middle Rio Grande Biological Interagency Team 1993, pp. 64, 89, 94; Castelle
et al.
1994, pp. 279-281) that are prey for northern Mexican and narrow-headed gartersnakes, as well as for the snakes themselves. Habitat quality within the mainstem river channels in the historical range of the northern Mexican and narrow-headed gartersnakes is intrinsically related to the character of the floodplain and the associated tributaries, side channels, and backwater habitats that contribute to important habitat features that provide gartersnakes opportunities for foraging and basking in these reaches. We have determined that a relatively intact riparian area, along with periodic flooding in a generally natural pattern, is important for maintaining the PCEs necessary for long-term conservation of the northern Mexican and narrow-headed gartersnakes, as well as their primary prey species.

The lateral extent (width) of riparian corridors fluctuates considerably between a stream's headwaters and its mouth. The appropriate width of riparian terrestrial habitat to protect stream function has been the subject of several studies and varies depending on the specific function (Castelle
et al.
1994, pp. 879-881). Most Federal and State agencies generally consider a zone 75 to 150 ft (23 to 46 m) wide on each side of a stream to be adequate (Natural Resource Conservation Service 1998, pp. 2-3; Moring
et al.
1993, p. 204; Lynch
et al.
1985, p. 164), although widths as wide as 500 ft (152 m) have been recommended for achieving flood attenuation benefits (U.S. Army Corps 1999, pp. 5-29). In most instances, however, adequate riparian space is primarily intended to reduce detrimental impacts to the stream from sources outside the river channel, such as pollutants, in adjacent areas. Consequently, while a riparian corridor 75 to 150 ft (23 to 46 m) in width may protect water quality and provide some level of riparian habitat protection, a wider area would provide full

protection of riparian habitat because the stream itself can move within the floodplain in response to high flow events, and also provide terrestrial space required by northern Mexican and narrow-headed gartersnakes to engage in normal behaviors such as foraging, basking, gestation, brumation, establishing home ranges, dispersal, and so forth. Using telemetry data (Nowak 2006, pp. 19-21), the farthest distance a narrow-headed gartersnake has been detected from water is 650 ft (200 m), while Rosen and Schwalbe (1988, p. 27) report observing a northern Mexican gartersnake at a distance of 330 ft (100 m) away from permanent water. Based on the literature, we expect the majority of terrestrial activity for both species occurs within 600 ft (182.9 m) of permanent water in lotic habitat.

We believe a 600-ft (182.9-m) lateral extent to either side of bankfull stage will sufficiently protect the majority of important terrestrial habitat; provide brumation, gestation, and dispersal opportunities; and reduce the impacts of high flow events, thereby providing adequate protection to proposed critical habitat areas. We believe this width is necessary to accommodate stream properties such as meandering and high flows, and ensure these designations contain ample terrestrial space such that features essential to the conservation of these gartersnakes and their prey species can occur naturally. Bankfull stage is defined as the upper level of the range of channel-forming flows, which transport the bulk of available sediment over time. Bankfull stage is generally considered to be that level of stream discharge reached just before flows spill out onto the adjacent floodplain. The discharge that occurs at bankfull stage, in combination with the range of flows that occur over a length of time, govern the shape and size of the river channel (its geomorphology) (Rosgen 1996, pp. 2-2 to 2-4; Leopold 1997, pp. 62- 63, 66). The use of bankfull stage and 600 ft (182.9 m) on either side recognizes the naturally dynamic nature of riverine systems, recognizes that floodplains are an integral part of the stream ecosystem, and contains sufficient terrestrial space and associated features essential to the conservation of the northern Mexican and narrow-headed gartersnakes. Bankfull stage is not an ephemeral feature, meaning it does not disappear. Bankfull stage can always be determined and delineated for any stream we have designated as critical habitat. We acknowledge that the bankfull stage of any given stream may change depending on the magnitude of a flood event, but it is a definable and standard measurement for stream systems. Unlike trees, cliff faces, and other immovable habitat elements, stream systems provide habitat that is in constant change. Following high flow events, stream channels can move from one side of a canyon to the opposite side, for example.

Designating critical habitat based on the location of the stream on a specific date is problematic for maintaining important habitat elements. For example, the area within such a designation could transition from providing aquatic habitat and prey to become a dry channel in a short period of time as a result of a high flow event and the subsequent shift in the location of the channel.

We determined the 600-ft (182.9-m) lateral extent for several reasons. Although we considered using either the 100-year or 500-year floodplain, as defined by the Federal Emergency Management Agency, we found that the information was not readily available from the Federal Emergency Management Agency or from the U.S. Army Corps of Engineers for remote areas we are proposing for designation. Therefore, we selected the 600-ft (182.9-m) lateral extent, rather than some other delineation, for four biological reasons: (1) The biological integrity and natural dynamics of the river system and associated riparian habitat are maintained within this area (
i.e.,
the floodplain and its riparian vegetation provide space for natural flooding patterns and latitude for necessary natural channel adjustments to maintain appropriate channel morphology and geometry, store water for slow release to maintain base flows, provide protected side channels and other protected areas, and allow the river to meander within its main channel in response to large flow events); (2) conservation of the adjacent riparian area also helps to provide important nutrient recharge to benefit the food web and protection from sediment and pollutants; (3) vegetated lateral zones are widely recognized as providing a variety of aquatic habitat functions and values (
e.g.,
aquatic habitat for prey such as fish and other aquatic organisms and detritus for aquatic food webs) and help improve or maintain local water quality (see U.S. Army Corps of Engineers' Final Notice of Issuance and Modification of Nationwide Permits, March 9, 2000, 65 FR 12818); and (4) a 600-ft (182.9-m) buffer contributes to the functioning of a river or stream system and provides adequate terrestrial space for normal northern Mexican and narrow-headed gartersnake behaviors, thereby supporting the PCEs needed for suitable northern Mexican and narrow-headed gartersnake habitat as described by the best available scientific and commercial information.

When determining proposed critical habitat boundaries, we made every effort to avoid including large developed areas such as lands covered by buildings, pavement, and other structures because such lands lack physical or biological features for the northern Mexican and narrow-headed gartersnakes. While reptiles, including gartersnakes, may use artificial materials for cover, areas that have been significantly altered by construction-related development are not generally suitable for gartersnakes or their prey species. The scale of the maps we prepared under the parameters for publication within the Code of Federal Regulations may not reflect the exclusion of such developed lands. Any such lands inadvertently left inside critical habitat boundaries shown on the maps of this proposed rule have been excluded by text in the proposed rule and are not proposed for designation as critical habitat. Therefore, if critical habitat is finalized as proposed, a Federal action involving these lands would not trigger section 7 consultation with respect to critical habitat and the requirement of no adverse modification, unless the specific action would affect the physical or biological features in the adjacent critical habitat.

We are proposing for designation of critical habitat lands that we have determined are occupied at the time of listing and contain sufficient elements of physical or biological features to support life-history processes essential for the conservation of the species.

Units are proposed for designation based on sufficient elements of physical or biological features being present to support the northern Mexican and narrow-headed gartersnakes' life-history processes. Some units contain all of the identified elements of physical or biological features and support multiple life-history processes. Some segments contain only some elements of the physical or biological features necessary to support the northern Mexican and narrow-headed gartersnakes' particular use of that habitat.

The critical habitat designation is defined by the maps, as modified by any accompanying regulatory text, presented at the end of this document in the Proposed Regulation Promulgation section. We include more detailed information on the proposed boundaries of the critical habitat designation in the preamble of this document. We will make the coordinates or plot points or both on which each map is based

available to the public on
http://www.regulations.gov
at Docket No. FWS-R2-ES-2013-0022, on our Internet site at
http://www.fws.gov/southwest/es/arizona,
and at the field office responsible for the designation (see
FOR FURTHER INFORMATION CONTACT
above).

Proposed Critical Habitat Designation

We are proposing 14 units as critical habitat for the northern Mexican gartersnake and 6 units as critical habitat for the narrow-headed gartersnake. The critical habitat areas we describe below constitute our current best assessment of areas that meet the definition of critical habitat for the northern Mexican and narrow-headed gartersnakes. The 14 units we propose as critical habitat for the northern Mexican gartersnake include lands in the following areas: (1) Gila River Mainstem; (2) Mule Creek; (3) Bill Williams River; (4) Agua Fria River Subbasin; (5) Upper Salt River Subbasin; (6) Tonto Creek; (7) Verde River Subbasin; (8) Upper Santa Cruz River Subbasin; (9) Redrock Canyon; (10) Buenos Aires National Wildlife Refuge; (11) Cienega Creek Subbasin; (12) San Pedro River Subbasin; (13) Babocomari River Subbasin; and (14) the San Bernardino National Wildlife Refuge (SBNWR). The six units we propose as critical habitat for the narrow-headed gartersnake are: (1) Upper Gila River Subbasin; (2) Middle Gila River Subbasin; (3) San Francisco River Subbasin; (4) Salt River Subbasin; (5) Tonto Creek Subbasin; and (6) Verde River Subbasin. All units for both species are considered occupied. It is important to recognize that while all units for both species are considered occupied, the majority of populations in these proposed critical habitat units are currently considered likely not viable into the future. We have concluded that 83 percent of the northern Mexican gartersnake's populations in the United States and 76 percent of the narrow-headed gartersnake's populations occur at low densities and are likely not viable. Please see Appendix A (available at
http://www.regulations.gov
under Docket No. FWS-R2-ES-2013-0022) for detailed information on occupancy status.

Table 3
a
—Land Ownership for Proposed Critical Habitat Units for the Northern Mexican Gartersnake

[Area estimates reflect all land within critical habitat unit boundaries. County-owned lands are considered as private lands]

Unit
Subunit
Land ownership by type
Federal
State
Tribal
Private
Size of unit

Upper Gila River

10,845 ac (4,389 ha)
467 ac (189 ha)

9,822 ac (3,975 ha)
21,135 ac (8,553 ha).

Unit Total

10,845 ac (4,389 ha)
467 ac (189 ha)

9,822 ac (3,975 ha)
21,135 ac (8,553 ha).

Mule Creek

1,327 ac (537 ha)

1,253 ac (507 ha)
2,579 ac (1044 ha).

Unit Total

1,327 ac (537 ha)

1,253 ac (507 ha)
2,579 ac (1044 ha).

Bill Williams River

3,820 ac (1,546 ha)
516 ac (209 ha)

1,076 ac (435 ha)
5,412 ac (2,190 ha).

Unit Total

3,820 ac (1,546 ha)
516 ac (209 ha)

1,076 ac (435 ha)
5,412 ac (2,190 ha).

Agua Fria River Subbasin
Agua Fria River Mainstem
3,313 ac (1,341 ha)
918 ac (372 ha)

2,758 ac (1,116 ha)
6,989 ac (2,828 ha).

Little Ash Creek
877 ac (355 ha)

80 ac (32 ha)
957 ac (387 ha).

Unit Total

4,010 ac (1,696 ha)
918 ac (372 ha)

2,838 ac (1,148 ha)
7,946 ac (3,215 ha).

Upper Salt River Subbasin
Black River
2,632 ac (1,065 ha)

13,760 ac (5,569 ha)

16,392 ac (6,634 ha).

Big Bonito Creek

5,826 ac (2,358 ha)

5,826 ac (2,358 ha).

Unit Total

2,632 ac (1,065 ha)

19,586 ac (7,927 ha)

22,218 ac (8,991 ha).

Tonto Creek

7,766 ac (3,143 ha)

1,170 ac (474 ha)
8,936 ac (3,616 ha).

Unit Total

7,766 ac (3,143 ha)

1,170 ac (474 ha)
8,936 ac (3,616 ha).

Verde River Subbasin
Upper Verde River
13,903 ac (5,626 ha)
1,209 ac (489 ha)
192 ac (78 ha)
5,223 ac (2,114 ha)
20,526 ac (8,307 ha).

Oak Creek
1,873 ac (758 ha)
274 ac (111 ha)

3,386 ac (1,370 ha)
5,533 ac (2,239 ha).

Spring Creek
2,572 ac (1,041 ha)
188 ac (76 ha)

371 ac (150 ha)
3,131 ac (1,267 ha).

Unit Total

18,348 ac (7,425 ha)
1,671 ac (676 ha)
192 ac (78 ha)
8,980 ac (3,634 ha)
29,191 ac (11,813 ha).

Upper Santa Cruz River Subbasin

77,387 ac (31,318 ha)
3,969 ac (1,606 ha)

32,538 ac (13,168 ha)
113,895 ac (46,092 ha).

Unit Total

77,387 ac (31,318 ha)
3,969 ac (1,606 ha)

32,538 ac (13,168 ha)
113,895 ac (46,092 ha).

Redrock Canyon

1,423 ac (576 ha)

549 ac (222 ha)
1,972 ac (798 ha).

Unit Total

1,423 ac (576 ha)

549 ac (222 ha)
1,972 ac (798 ha).

Buenos Aires National Wildlife Refuge

117,313 ac (47,475 ha)

117,313 ac (47,475 ha).

Unit Total

117,313 ac (47,475 ha)

117,313 ac (47,475 ha).

Cienega Creek Subbasin
Cienega Creek
24 ac (10 ha)
1,078 ac (436 ha)

11 ac (4 ha)
1,113 ac (450 ha).

Las Cienegas National Conservation Area
39,913 ac (16,152 ha)
5,105 ac (2,066 ha)

1 ac (<1 ha)
45,020 ac (18,219 ha).

Cienega Creek Natural Preserve

4,260 ac (1,724 ha)
4,260 ac (1,724 ha).

Unit Total

39,937 ac (16,162 ha)
6,183 ac (2,502 ha)

4,272 ac (1,728 ha)
50,393 ac (20,393 ha).

San Pedro River Subbasin
San Pedro River
6,973 ac (2,822 ha)
1,163 ac (470 ha)
76 ac (31 ha)
14,456 ac (5,850 ha)
22,669 ac (9,174 ha).

Bear Canyon Creek
639 ac (259 ha)

383 ac (155 ha)
1,022 ac (414 ha).

Unit Total

7,612 ac (3,081 ha)
1,163 ac (470 ha)
76 ac (31 ha)
14,839 ac (6,005 ha)
23,690 ac (9,587 ha).

Babocomari River Subbasin
Babocomari River/Cienega
625 ac (253 ha)
56 ac (23 ha)

2,773 ac (1,122 ha)
3,454 ac (1,398 ha).

Post Canyon
431 ac (175 ha)

363 ac (147 ha)
795 ac (322 ha).

O'Donnell Canyon
124 ac (50 ha)

274 ac (111 ha)
398 ac (161 ha).

Turkey Creek
888 ac (359 ha)
2 ac (1 ha)

788 ac (319 ha)
1,678 ac (679 ha).

Appleton-Whittell Research Ranch
5,283 ac (2,138 ha)

2,515 ac (1,018 ha)
7,798 ac (3,156 ha).

Canelo Hills Cienega Preserve

213 ac (86 ha)
213 ac (86 ha).

Unit Total

7,351 ac (2,975 ha)
58 ac (24 ha)

6,926 ac (2,803 ha)
14,334 ac (5,801 ha).

San Bernardino National Wildlife Refuge

2,387 ac (966 ha)

2,387 ac (966 ha).

Total

302,338 ac (122,352 ha)
14,966 ac (6,057 ha)
19,855 ac (8,035 ha)
84,263 ac (34,100 ha)
421,423 ac (170,544 ha).

Note:
Numbers may not sum due to rounding.

Table 3
b
—Land Ownership for Proposed Critical Habitat Units for Narrow-Headed Gartersnakes

[Area estimates reflect all land within critical habitat unit boundaries. County-owned lands are considered as private lands]

Unit
Subunit
Land ownership by type
Federal
State
Tribal
Private
Size of unit

Upper Gila River Subbasin
Gila River
10,845 ac (4,389 ha)
467 ac (189 ha)

9,822 ac (3,975 ha)
21,135 ac (8,553 ha).

East Fork Gila River
2,929 ac (1,185 ha)

649 ac (263 ha)
3,579 ac (1,148 ha).

West Fork Gila River
4,793 ac (1,940 ha)

376 ac (152 ha)
5,169 ac (2,092 ha).

Middle Fork Gila River
4,875 ac (1,973 ha)

89 ac (36 ha)
4,964 ac (2,009 ha).

Black Canyon
3,465 ac (1,402 ha)

38 ac (15 ha)
3,503 ac (1,418 ha).

Diamond Creek
2,995 ac (1,212 ha)

550 ac (223 ha)
3,545 ac (1,435 ha).

Gilita Creek
1,704 ac (690 ha)

1,704 ac (690 ha).

Iron Creek
1,731 ac (701 ha)

1,731 ac (701 ha).

Little Creek
2,223 ac (900 ha)

13 ac (5 ha)
2,236 ac (905 ha).

Turkey Creek
2,338 ac (946 ha)

2,338 ac (946 ha).

Unit Total

37,898 ac (15,338 ha)
467 ac (189 ha)

11,537 ac (4,669 ha)
49,903 ac (20,195 ha).

Middle Gila River Subbasin
Gila River
422 ac (171 ha)

11 ac (4 ha)
432 ac (175 ha).

Eagle Creek
2,016 ac (816 ha)
54 ac (22 ha)
2,258 ac (1,035 ha)
3,754 ac (1,519 ha)
8,382 ac (3,392 ha).

Unit Total

2,438 ac (987 ha)
54 ac (22 ha)
2,258 ac (1,035 ha)
3,765 ac (1,523 ha)
8,814 ac (3,567 ha).

San Francisco River Subbasin
San Francisco River
15,661 ac (6,338 ha)
216 ac (88 ha)

7,300 ac (2,954 ha)
23,178 ac (9,380 ha).

Blue River
6,484 ac (2,624 ha)

948 ac (383 ha)
7,432 ac (3,007 ha).

Campbell Blue Creek
2,888 ac 1,169 ha)

120 ac (49 ha)
3,008 ac (1,217 ha).

Dry Blue Creek
1,320 ac (534 ha)

1,320 ac (534 ha).

South Fork Negrito Creek
1,383 ac (560 ha)

100 ac (40 ha)
1,483 ac (600 ha).

Saliz Creek
852 ac (345 ha)

247 ac (100 ha)
1,099 ac (445 ha).

Tularosa River
1,875 ac (759 ha)

2,852 ac (1,154 ha)
4,728 ac (1,913 ha).

Whitewater Creek
2,282 ac (923 ha)

547 ac (221 ha)
2,289 ac (1,145 ha).

Unit Total

32,745 ac (13,252 ha)
216 ac (88 ha)

12,114 ac (4,901 ha)
45,075 ac (18,241 ha).

Upper Salt River Subbasin
Salt River
5,342 ac (2,162 ha)

7,502 ac (3,036 ha)
33 ac (13 ha)
12,877 ac (5,211 ha).

White River

2,588 ac (1,047 ha)

2,588 ac (1,047 ha).

Canyon Creek
1,182 ac (478 ha)

6,160 ac (2,493 ha)
3 ac (1 ha)
7,346 ac (2,973 ha).

Carrizo Creek
158 ac (64 ha)

8,875 ac (3,592 ha)

9,033 ac (1,229 ha).

Cibecue Creek

6,669 ac (2,699 ha)

6,669 ac (2,699 ha).

Diamond Creek

3,117 ac (1,261 ha)

3,117 ac (1,261 ha).

Black River
2,632 ac (1,065 ha)

13,752 ac (5,565 ha)

16,384 ac (6,630 ha).

Unit Total

9,314 ac (3,769 ha)

48,663 ac (19,693 ha)
36 ac (14 ha)
58,014 ac (23,478 ha).

Tonto Creek Subbasin
Haigler Creek
2,831 ac (1,146 ha)

206 ac (83 ha)
3,037 ac (1229 ha).

Houston Creek
1,747 ac (707 ha)

299 ac (121 ha)
2,046 ac (828 ha).

Tonto Creek
7,017 ac (2,840 ha)

696 ac (282 ha)
7,712 ac (3,121 ha).

Unit Total

11,595 ac (4,693 ha)

1,201 ac (486 ha)
12,795 ac (5,178 ha).

Verde River Subbasin
Verde River
12,098 ac (4,896 ha)
1,209 ac (489 ha)
192 ac (78 ha)
5,223 ac (2114 ha)
18,721 ac (7576 ha).

Oak Creek
3,340 ac (1,352 ha)
328 ac (133 ha)

3,701 ac (1,498 ha)
7,369 ac (2,982 ha).

West Fork Oak Creek
2,137 ac (865 ha)

2,137 ac (865 ha).

East Verde River
6,682 ac (2,704 ha)

678 ac (274 ha)
7,360 ac (2,978 ha).

Unit Total

24,257 ac (9,817 ha)
1,537 ac (622 ha)
192 ac (78 ha)
9,602 ac (3,886 ha)
35,586 ac (14,401 ha).

Total

118,247 ac (47,853 ha)
2,275 ac (921 ha)
51,415 ac (20,807 ha)
38,253 ac (15,480 ha)
210,189 ac (85,060 ha).

Note:
Numbers may not sum due to rounding.

The following are brief descriptions of all units and our reasoning as to why they meet the definition of critical habitat for the northern Mexican gartersnake or the narrow-headed gartersnake.

Northern Mexican Gartersnake

Upper Gila River Unit

The Upper Gila River Unit is generally located in southwestern New Mexico in the Gila Wilderness of the Gila National Forest in Hidalgo and Grant Counties, New Mexico, and eastern Arizona in Graham County. This unit consists of a total of 21,135 acres (8,553 ha) along 148 stream mi (239 km) of proposed critical habitat along the Gila River mainstem. Land ownership or land management within this unit consists of lands managed by the U.S. Forest Service, New Mexico Department of Game and Fish, State Trust lands, and private ownership. The identified area described in the Upper Gila River Unit has records since 1980 for northern Mexican gartersnakes, and is within the geographical area currently occupied by the species. We are proposing the area in this unit because it is occupied by the species and because it contains essential physical or biological features that may require special management considerations or protection. The following narrative describes the area proposed as critical habitat in the Upper Gila River Unit.

We are proposing to designate 21,135 acres (8,553 ha) of critical habitat along 148.2 stream mi (238.6 km) of the upper Gila River, from its confluence with the San Francisco River in Graham County, Arizona, upstream to its confluence with East Fork Gila River and Black Canyon in Catron County, New Mexico. The Upper Gila River Unit is primarily privately owned, with additional parcels managed by the Gila National Forest, the New Mexico Department of Game and Fish, and the Arizona and New Mexico State Land Departments. Several reaches of the Gila River in New Mexico have been adversely affected by channelization and diversions, which have reduced or eliminated baseflow. As a whole, however, this unit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics) and 2 (terrestrial habitat characteristics), but PCEs 3 (prey base) and 4 (absence or low level of harmful nonnative species) are deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of harmful nonnative species and improving the status of ranid frog populations. Lands within The Nature Conservancy's Gila Riparian Preserve in this unit are being considered for exclusion from the final rule for critical habitat under section 4(b)(2) of the Act (see
Application of Section 4(b)(2) of the Act
below).

The Upper Gila River Unit is proposed as critical habitat for the northern Mexican gartersnake because it is occupied at the time of listing and contains sufficient physical or biological features to support life-history functions essential for the conservation of the species. Some reaches of the Gila River have been adversely affected by channelization and water diversions. There remains the potential for the construction of Hooker Dam in the reach of the Gila River above Mogollon Creek and below Turkey Creek as part of the Central Arizona Project, which would adversely affect both the physical habitat for northern Mexican gartersnakes as well as their prey base, but this project remains in deferment status. The physical or biological features in this unit may require special management consideration due to competition with, and predation by, harmful nonnative species that are present in this unit; water diversions; channelization; potential for high-intensity wildfires; and human development of areas adjacent to proposed critical habitat.

Mule Creek Unit

The Mule Creek Unit is generally located in southwestern New Mexico in the vicinity of Mule Creek, New Mexico (Grant and Catron Counties). This unit consists of a total of 2,579 acres (1,044 ha) along 19 stream mi (30 km) of proposed critical habitat along Mule Creek. Land ownership or land management within this unit consists of lands managed by the U.S. Forest Service and private ownership. The identified area described in the Mule Creek Unit has records for northern Mexican gartersnakes since 1980, and is considered as being within the geographical area currently occupied by the species. We are proposing this area under section 3(5)(A)(i) of the Act because it is occupied by the species and because it contains essential physical or biological features that may require special management considerations or protection. The following narrative describes the area proposed as critical habitat in the Mule Creek Unit.

We are proposing to designate 2,579 acres (1,044 ha) of critical habitat along 18.7 stream mi (30.1 km) of Mule Creek, from its confluence with the San Francisco River, upstream to its origin northwest of North Sawmill Canyon in Grant and Catron Counties, New Mexico. The Mule Creek Subunit is managed by the Gila National Forest, with additional parcels under private ownership. Mule Creek supports native fish and supports an adequate amount of suitable aquatic and terrestrial habitat with the appropriate characteristics to support the northern Mexican gartersnake. However, the habitat quality is somewhat compromised by the presence of bullfrogs, which are known to have a negative association

with northern Mexican gartersnakes. This subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and 3 (prey base), but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the physical or biological features, including management to remove or reduce bullfrogs.

The Mule Creek Unit is proposed as critical habitat for the northern Mexican gartersnake because it is occupied at the time of listing and contains sufficient physical or biological features to support life-history functions essential for the conservation of the species. The physical or biological features in this unit may require special management consideration due to competition with, and predation by, harmful nonnative species that are present in this unit; potential for high-intensity wildfires; and human development of areas adjacent to proposed critical habitat.

Bill Williams River Unit

The Bill Williams River Unit is generally located in western Arizona, northeast of Parker, Arizona, in La Paz and Mohave Counties. This unit consists of a total of 5,412 acres (2,190 ha) along 36 stream mi (58 km) of proposed critical habitat along the Bill Williams River, Arizona. We are proposing to designate the reach of the Bill Williams River running from its confluence with Lake Havasu, upstream to Alamo Lake Dam. The Bill Williams River Unit occurs on lands primarily managed by the U.S. Bureau of Land Management. Remaining land management and ownership includes the Bill Williams National Wildlife Refuge, U.S. Department of Defense lands, Arizona State Land Department, and private land owners. All identified areas described in this unit have records for northern Mexican gartersnakes since 1980, and all identified areas are considered as being within the geographical area currently occupied by the species. We are proposing this unit under section 3(5)(A)(i) of the Act because it is occupied by the species and because it contains essential physical or biological features that may require special management considerations or protection. This unit contains adequate populations of lowland leopard frogs, but native fish appear to be absent. Crayfish and several species of nonnative, spiny-rayed fish maintain robust populations in this reach. Within this unit, PCEs 1 (aquatic habitat characteristics) and 2 (terrestrial habitat characteristics) are present, but PCEs 3 (prey base) and 4 (absence or low level of harmful nonnative species) are deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of crayfish and nonnative, spiny-rayed fish, as well as the prevention of a bullfrog invasion.

The Bill Williams River Unit is proposed as critical habitat for the northern Mexican gartersnake because it is occupied at the time of listing and contains sufficient physical or biological features to support life-history functions essential for the conservation of the species. The physical or biological features in this unit may require special management consideration due to competition with, and predation by, harmful nonnative species that are present in this unit and flood-control projects.

Agua Fria River Subbasin Unit

The Agua Fria River Subbasin Unit is generally located in central Arizona, paralleling Interstate 17, just north of the Phoenix metropolitan area, in Yavapai County, Arizona. This unit consists of a total of 7,946 acres (3,215 ha) along 56 stream mi (91 km) of proposed critical habitat along the Agua Fria River and Little Ash Creek. Land ownership or land management within this unit consists of lands managed by the U.S. Bureau of Land Management, U.S. Forest Service, State Trust lands, and private ownership. All identified areas described in the Agua Fria River Subbasin Unit have records since 1980 for northern Mexican gartersnakes, and all are considered as being within the geographical area currently occupied by the species. We are proposing the areas in this unit under section 3(5)(A)(i) of the Act because they are essential for the conservation of the northern Mexican gartersnake. The following narratives describe all of the subunits proposed as critical habitat in the Agua Fria River Subbasin Unit.

Agua Fria River Mainstem Subunit. We are proposing to designate 6,989 acres (2,828 ha) of critical habitat along 49.1 stream mi (80.0 km) of the Agua Fria River mainstem, from its confluence with Squaw Creek east of Black Canyon City, upstream to its confluence with the unnamed drainage south of Highway 169 in Dewey, Arizona (Yavapai County). Also included in this subunit are 88 acres (36 ha) of the Arizona Game and Fish Department's Horseshoe Ranch property, which is located along the Agua Fria River at its confluence with Indian Creek. The Agua Fria River Mainstem Subunit is primarily privately owned or managed by the U.S. Bureau of Land Management, with additional parcels managed by the Arizona State Land Department. The Agua Fria River contains nonnative, soft-rayed fish and lowland leopard frogs as prey, and contains an adequate amount of suitable aquatic and terrestrial habitat with the appropriate characteristics to support the northern Mexican gartersnake. However, the dominance of crayfish, bullfrogs, and nonnative, spiny-rayed fish in some reaches negatively affects the proposed subunit's suitability for northern Mexican gartersnakes. This subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and 3 (prey base), but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the physical or biological features, including management to remove or reduce crayfish, bullfrogs, and nonnative, spiny-rayed fish. Lands within the Arizona Game and Fish Department's Horseshoe Ranch property are being considered for exclusion from the final rule for critical habitat under section 4(b)(2) of the Act (see
Application of Section 4(b)(2) of the Act
below).

Little Ash Creek Subunit. We are proposing to designate 957 acres (387 ha) of critical habitat along 6.7 stream mi (10.7 km) of Little Ash Creek, from the confluence of Ash Creek, upstream to its confluence with an unnamed drainage east of the bridge over Dugas Road in Yavapai County, Arizona. The Little Ash Creek Subunit is primarily managed by the Prescott National Forest and U.S. Bureau of Land Management with additional parcels under Arizona State Land Department and private ownership. According to GIS analysis, Little Ash Creek supports populations of lowland leopard frogs and two species of native fish, and contains adequate amount of suitable aquatic and terrestrial habitat with the appropriate characteristics to support the northern Mexican gartersnake, but the dominance of crayfish, bullfrogs, and nonnative, spiny-rayed fish in some reaches negatively affects the suitability for northern Mexican gartersnakes. This subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and 3 (prey base), but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the

physical or biological features, including management against crayfish, bullfrogs, and nonnative, spiny-rayed fish.

The Agua Fria Subbasin Unit is proposed as critical habitat for the northern Mexican gartersnake because it is occupied at the time of listing and contains sufficient physical or biological features to support life-history functions essential for the conservation of the species. The physical or biological features in this unit may require special management consideration due primarily to competition with, and predation by, harmful nonnative species that are present in this unit and to a lesser extent human development of areas adjacent to proposed critical habitat.

Upper Salt River Subbasin Unit

The Upper Salt River Subbasin Unit is generally located along the Mogollon Rim in east-central Arizona, and includes portions of Gila, Graham, Apache, Navajo, and Greenlee Counties. The Upper Salt River Subbasin Unit largely includes remote, rural areas, generally under the ownership and management of tribal governments, specifically the White Mountain Apache and San Carlos Apache Tribes. This unit consists of a total of 22,218 acres (8,991 ha) along 156 stream mi (251 km) of proposed critical habitat along the Black River and Big Bonito Creek. Land ownership or land management within this unit consists of tribal lands and those managed by the U.S. Forest Service. All identified areas described in the Salt River Subbasin Unit have records since 1980 for northern Mexican gartersnakes, and all identified areas are considered as being within the geographical area currently occupied by the species. We are proposing the areas in this unit under section 3(5)(A)(i) of the Act because they are occupied by the species and because they contain sufficient amounts of the essential physical or biological features that may require special management considerations or protection. The following narratives describe all of the subunits proposed as critical habitat in the Upper Salt River Subbasin Unit.

Black River Subunit. We are proposing to designate 16,392 acres (6,634 ha) of critical habitat along 114.4 stream mi (184.0 km) of the Black River from its confluence with the Salt and White rivers, upstream to the confluence with the East and West Forks of the Black River. The Black River Drainage Subunit occurs in Apache, Gila, Graham, Greenlee, and Navajo Counties, Arizona. The Black River drainage is primarily owned by the White Mountain Apache and San Carlos Apache Tribes, with additional parcels managed by the Apache-Sitgreaves National Forest. Water in the Black River is diverted for use at the Morenci Mine, which may affect baseflow. This subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and PCE 3 (prey base), but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of crayfish and possibly nonnative, spiny-rayed fish, as well as to maintain adequate base flows in the Black River. Lands owned by the White Mountain Apache and San Carlos Apache Tribes are being considered for exclusion from the final rule for critical habitat under section 4(b)(2) of the Act (see
Application of Section 4(b)(2) of the Act
below).

Big Bonito Creek Subunit. We are proposing to designate 5,826 acres (2,358 ha) of critical habitat along 41.5 stream mi (66.8 km) of Big Bonito Creek, from its confluence with the Black River east of the mouth of Sawmill Canyon, upstream to its origin southwest of Mount Baldy in the White Mountains, in Apache and Navajo Counties, Arizona. Big Bonito Creek is solely owned by the White Mountain Apache Tribe. This subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics) and 2 (terrestrial habitat characteristics), but PCEs 3 (prey base) and 4 (absence or low level of harmful nonnative species) are deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of crayfish and nonnative, spiny-rayed fish, as well as management to support a native prey base for northern Mexican gartersnakes. This subunit is being considered for exclusion from the final rule for critical habitat under section 4(b)(2) of the Act (see
Application of Section 4(b)(2) of the Act
below).

The Upper Salt River Subbasin Unit is proposed as critical habitat for the northern Mexican gartersnake because it is occupied at the time of listing and largely contains sufficient physical or biological features to support life-history functions essential for the conservation of the species. However, the 2011 Wallow Fire adversely affected a large proportion of the Black River drainage, and subsequent ash and sediment flows have likely resulted in a depressed fish community, which could stress resident northern Mexican gartersnake populations in the short to medium term. The physical or biological features in this unit may require special management consideration due to competition with, and predation by, harmful nonnative species that are present in this unit; water diversions; potential for high-intensity wildfires; and human development of areas adjacent to proposed critical habitat.

Tonto Creek Unit

The Tonto Creek Unit is generally located southeast of Payson, Arizona, and northeast of the Phoenix metropolitan area, in Gila County. We are proposing to designate 8,936 acres (3,616 ha) of critical habitat along 65.1 stream mi (104.7 km) of Tonto Creek, from its confluence with Roosevelt Lake upstream to its origin northeast of Tonto Spring, south of Rim Road, in Gila County, Arizona. Tonto Creek occurs predominately on lands managed by the Tonto National Forest. The remaining landownership is private. Therefore, we are proposing this unit under section 3(5)(A)(i) of the Act because it is occupied by the species and because it contains sufficient amounts of the essential physical or biological features that may require special management considerations or protection. Some reaches along Tonto Creek experience seasonal drying as a result of regional groundwater pumping, while others are affected by diversions or existing or planned flood control projects. Development along private reaches of Tonto Creek may also affect terrestrial characteristics of northern Mexican gartersnake habitat. Mercury has been detected in fish samples within Tonto Creek, and further research is necessary to determine if mercury is bioaccumulating in the resident food chain. In general, this unit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and 3 (prey base), but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of crayfish, bullfrogs, and nonnative, spiny-rayed fish, as well as improve base flows.

The Tonto Creek Unit is proposed as critical habitat for the northern Mexican gartersnake because it is occupied at the time of listing and contains sufficient physical or biological features to support life-history functions essential for the conservation of the species. The physical or biological features in this

unit may require special management consideration due to competition with, and predation by, harmful nonnative species that are present in this unit; water diversions; flood-control projects; and development of areas adjacent to or within proposed critical habitat.

Verde River Subbasin Unit

The Verde River Subbasin Unit is generally located southwest of Paulden, Arizona, and northwest of Payson, Arizona, in Coconino, Gila, and Yavapai Counties. This unit consists of a total of 29,191 acres (11,813 ha) along approximately 201 stream mi (323 km) of proposed critical habitat along the Verde River, Oak Creek, and Spring Creek. Lands within this unit consist of federally managed lands, State Trust lands and other State-managed lands, tribal lands, and privately owned lands. All identified areas described in the Verde River Subbasin Unit have records for northern Mexican gartersnakes, and all identified areas are considered as being currently within the geographical area occupied by the species. Therefore, we are proposing the areas in this unit under section 3(5)(A)(i) of the Act because they are occupied by the species and because they contain essential physical or biological features that may require special management considerations or protection. The following narratives describe all of the subunits proposed as critical habitat in the Verde River Subbasin Unit.

Upper Verde River Subunit. We are proposing to designate 20,526 acres (8,307 ha) of critical habitat along 139.8 stream mi (224.9 km) of the Verde River, from its confluence with Horseshoe Reservoir, upstream to its confluence with Sullivan Lake, in Gila and Yavapai Counties, Arizona. The Verde River occurs predominantly on lands managed by the U.S. Forest Service on the Prescott, Tonto, and Coconino National Forests. Remaining land management and ownership includes the Arizona Game and Fish Department, Arizona State Parks, Arizona State Trust, Yavapai Apache Tribe, and private land owners. Proposed groundwater pumping of the Big Chino Aquifer may adversely affect future baseflow in the Verde River, and therefore PCE 1. Development along the Verde River has eliminated habitat along portions of the Verde River through the Verde Valley. In general, this subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and 3 (prey base), but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of crayfish, bullfrogs, and nonnative, spiny-rayed fish, as well as ensuring adequate flow is retained in the Verde River. Lands along the Verde River included in the Arizona Game and Fish Departments' Upper Verde Wildlife Area, The Nature Conservancy's Verde Springs Preserve and Verde Valley property, lands owned by the Yavapai Apache Tribe, and lands owned by the Salt River Project and managed under their Horseshoe-Bartlett and Roosevelt HCPs are being considered for exclusion from the final rule for critical habitat under section 4(b)(2) of the Act (see
Application of Section 4(b)(2) of the Act
below).

Oak Creek Subunit. We are proposing to designate 5,533 acres (2,239 ha) of critical habitat along 38.5 stream mi (62.0 km) of Oak Creek, from its confluence with the Verde River south of Cornville, upstream to Midgely Bridge at the confluence with Wilson Canyon, in Coconino County, Arizona. Also included in this subunit are 149 acres (60 ha) of the Arizona Game and Fish Department's Bubbling Ponds and Page Springs State Fish Hatcheries, which are adjacent to each other, and occur along Oak Creek, upstream of its confluence with Spring Creek. The Oak Creek subunit occurs predominately on privately owned lands or lands managed by the Coconino National Forest. Remaining lands are managed by Arizona Game and Fish Department and Arizona State Parks. This reach of lower Oak Creek is largely dominated by crayfish, bullfrogs, and nonnative, spiny-rayed fish. This subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics) and 2 (terrestrial habitat characteristics), but PCEs 3 (prey base) and 4 (absence or low level of harmful nonnative species) are deficient. Special management may be required to maintain or develop the physical or biological features, including managing for native prey species and eliminating or reducing crayfish, bullfrog, and nonnative, spiny-rayed fish populations. Lands along lower Oak Creek included within the Arizona Game and Fish Department's Bubbling Ponds and Page Springs State Fish Hatcheries are being considered for exclusion from the final rule for critical habitat under section 4(b)(2) of the Act (see
Application of Section 4(b)(2) of the Act
below).

Spring Creek Subunit. We are proposing to designate 3,131 acres (1,267 ha) of critical habitat along 22.5 stream mi (36.2 km) of Spring Creek, from its confluence with the Oak Creek upstream to its origin southwest of Buck Ridge, in Yavapai County, Arizona. Spring Creek occurs predominately on lands managed by U.S. Forest Service on the Tonto and Coconino National Forests. Remaining lands are Arizona State Trust and privately owned lands. Spring Creek contains populations of lowland leopard frogs and several species of native fish which serve as the prey base for northern Mexican gartersnakes. However, crayfish have been observed as abundant in this subunit. This subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and 3 (prey base), but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of crayfish.

The Verde River Subbasin Unit is proposed as critical habitat for the northern Mexican gartersnake because it is occupied at the time of listing and contains sufficient physical or biological features to support life-history functions essential for the conservation of the species. The physical or biological features in this unit may require special management consideration due to competition with, and predation by, harmful nonnative species that are present in this unit; water diversions; existing and proposed groundwater pumping potentially resulting in drying of habitat; potential for high-intensity wildfires; and human development of areas adjacent to proposed critical habitat.

Upper Santa Cruz River Subbasin Unit

The Upper Santa Cruz River Subbasin Unit is generally located in southeastern Arizona, east of Nogales, southeast of Patagonia, and southwest of Sierra Vista, in the San Rafael Valley, in Santa Cruz and Cochise Counties, Arizona. This unit consists of springs, seeps, streams, stock tanks, and terrestrial space (overland areas) in between these features within a total of 113,895 acres (46,092 ha) of proposed critical habitat in the San Rafael Valley, including portions of Parker and Scotia canyons of the Huachuca Mountains, Arizona. For the streams within this unit, we are proposing the reach of Parker Canyon that includes 5.8 stream mi (9.3 km) from Duquesne Road south of Loop Road, upstream to and including Parker Canyon Lake. The reach of Scotia Canyon we are proposing as critical habitat includes 3.7 stream mi (5.9 km) from its confluence with an unnamed drainage at the junction with Bodie

Canyon, upstream to its origin west of the Coronado National Forest-Fort Huachuca Boundary. The upper Santa Cruz River occurs within the San Rafael Valley, flowing south into Mexico. We are proposing 13.8 stream mi (22.2 km) of the upper Santa Cruz River, from the International Border, upstream to its headwaters at the top of Sheep Ridge Canyon. The Upper Santa Cruz River Subbasin Unit occurs on lands primarily managed by the Coronado National Forest, with remaining land management under the Arizona State Parks Department. This unit also contains private lands. All identified areas described in this unit have records for northern Mexican gartersnakes, and all identified areas are considered as being currently within the geographical area occupied by the species. Therefore, we are proposing this unit under section 3(5)(A)(i) of the Act because it is occupied by the species and because it contains sufficient amounts of the essential physical or biological features that may require special management considerations or protection.

This unit contains adequate populations of Chiricahua and lowland leopard frogs, as well as native fish species in various locations and densities, with the former being actively recovered in Scotia Canyon. Bullfrogs and nonnative, spiny-rayed fish are also known to occur at various densities within this unit, and Parker Canyon Lake is managed as a warm-water sport fishery. Crayfish are also likely to occur in various locations and densities within this unit. Within this unit, PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics) and 3 (prey base) are generally met, but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the physical or biological features, including continuing to promote the recovery or expansion of native leopard frogs and fish, and eliminating or reducing harmful nonnative species. The San Rafael Ranch is being considered for exclusion from the final rule for critical habitat under section 4(b)(2) of the Act (see
Application of Section 4(b)(2) of the Act
section below).

The Upper Santa Cruz River Subbasin Unit is proposed as critical habitat for the northern Mexican gartersnake because it is occupied at the time of listing and contains sufficient physical or biological features to support life-history functions essential for the conservation of the species. The physical or biological features in this unit may require special management consideration due to competition with, and predation by, harmful nonnative species that are present in this unit and potential effects from future high-intensity wildfires.

Redrock Canyon Unit

We are proposing to designate 1,971 acres (798 ha) of critical habitat along 14.0 stream mi (22.5 km) of Redrock Canyon, from its confluence with Sonoita Creek, upstream to its origin north of Meadow Valley in the Canelo Hills, in Santa Cruz County. Redrock Canyon occurs predominately on lands managed by the Coronado National Forest with remaining land in private ownership. The area proposed along Redrock Canyon is within the area considered occupied by the northern Mexican gartersnake. Therefore, we are proposing the areas in this unit under section 3(5)(A)(i) of the Act because they are occupied by the species and because they contain sufficient amounts of the essential physical or biological features that may require special management considerations or protection.

Redrock Canyon supports four species of native fish, and Chiricahua leopard frogs and Sonora tiger salamanders have been reported. This subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and 3 (prey base), but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of bullfrogs and the prevention of potential invasions from nonnative, spiny-rayed fish. Lands within The Nature Conservancy's Patagonia-Sonoita Creek Preserve in this unit are being considered for exclusion from the final rule for critical habitat under section 4(b)(2) of the Act (see
Application of Section 4(b)(2) of the Act
below).

The Redrock Canyon Unit is proposed as critical habitat for the northern Mexican gartersnake because it is occupied at the time of listing and contains sufficient physical or biological features to support life-history functions essential for the conservation of the species. The physical or biological features in this unit may require special management consideration due to competition with, and predation by, harmful nonnative species that are present in this unit.

Buenos Aires National Wildlife Refuge Unit

The Buenos Aires National Wildlife Refuge Unit is generally located in southern Arizona, northwest of Nogales and south of Three Points, in Pima County, Arizona. This unit consists of a total of 117,335 acres (47,484 ha) of proposed critical habitat, including springs, seeps, streams, stock tanks, and terrestrial space in between these features within the Buenos Aires National Wildlife Refuge. The Buenos Aires National Wildlife Refuge Unit occurs on lands solely managed by the U.S. Fish and Wildlife Service. This unit is considered as being currently within the geographical area occupied by the species. Therefore, we are proposing this unit under section 3(5)(A)(i) of the Act because it is occupied by the species and because it contains sufficient amounts of the essential physical or biological features that may require special management considerations or protection.

This unit has been a focal point for the recovery of Chiricahua leopard frogs, providing prey for the northern Mexican gartersnake in a core area of stock tanks in the central region of the Refuge. Chiricahua leopard frogs also likely disperse from this area into other areas within the Refuge. Bullfrogs and crayfish remain a concern in Arivaca Cienega and Arivaca Creek. While not part of this unit, Arivaca Lake is operated as a warm-water sport fishery, and nonnative, spiny-rayed fish may be washed down and persist below the lake dam after overflow events. Within this unit, PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and 3 (prey base) are generally present, but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of crayfish, bullfrogs, and nonnative, spiny-rayed fish, as well as the prevention of a bullfrog invasion in Chiricahua leopard frog recovery core areas.

The Buenos Aires National Wildlife Refuge Unit is proposed as critical habitat for the northern Mexican gartersnake because it is occupied at the time of listing and contains sufficient physical or biological features to support life-history functions essential for the conservation of the species. The physical or biological features in this unit may require special management consideration due to competition with, and predation by, harmful nonnative species that are present in this unit.

Cienega Creek Subbasin Unit

The Cienega Creek Subbasin Unit is generally located in southern Arizona, east of the Santa Rita Mountains, north

of the Canelo Hills, and west of the Whetstone Mountains, in Pima and Santa Cruz Counties. This unit consists of springs, seeps, streams, stock tanks, and terrestrial space in between these features within a total of 50,393 acres (20,393 ha) of proposed critical habitat in the Las Cienegas National Conservation Area and Cienega Creek Natural Preserve. Also included in this unit is 7.1 stream mi (11.4 km) of Cienega Creek that occur outside of these specific ownership areas. The Cienega Creek Subbasin Unit occurs on lands primarily managed by the U.S. Bureau of Land Management and the Arizona State Land Department, with remaining lands under private ownership. All identified areas are considered as being within the geographical area currently occupied by the species. We are proposing the areas in this unit under section 3(5)(A)(i) of the Act because they are occupied by the species and because they contain essential physical or biological features that may require special management considerations or protection. The following narratives describe all of the subunits proposed as critical habitat in the Cienega Creek Subbasin Unit.

Cienega Creek Subunit. We are proposing to designate 1,113 acres (450 ha) of critical habitat along 7.1 stream mi (11.4 km) of Cienega Creek, from the northern boundary of the Las Cienegas National Conservation Area to the southern boundary of Cienega Creek Natural Preserve in Pima County, Arizona. The Cienega Creek Subunit occurs on lands managed by the Arizona State Land Department in addition to a small amount of private land. Native fish and both Chiricahua and lowland leopard frog populations provide prey for northern Mexican gartersnakes, and recent, ongoing bullfrog eradication in the area reduces the threat of bullfrogs within this subunit. This subunit contains sufficient physical or biological features, including all PCEs. However, special management may be required to maintain or develop the physical or biological features, including preventing the invasion or reinvasion of bullfrogs.

Las Cienegas National Conservation Area Subunit. We are proposing to designate critical habitat for a total of 45,020 acres (18,219 ha) of springs, seeps, streams, stock tanks, and terrestrial space in between these features within the Las Cienegas National Conservation Area in Pima County, including portions of Cienega Creek and Empire Gulch that occur within the Las Cienegas National Conservation Area. The Las Cienegas National Conservation Area is managed by the U.S. Bureau of Land Management, although it includes some Arizona State Trust Lands. Native fish and both Chiricahua and lowland leopard frog populations provide prey for northern Mexican gartersnakes, and recent, ongoing bullfrog eradication in the area reduces the threat of bullfrogs within this subunit. This subunit contains sufficient physical or biological features, including all PCEs. However, special management may be required to maintain or develop the physical or biological features, including preventing the invasion or reinvasion of bullfrogs.

Cienega Creek Natural Preserve Subunit. We are proposing to designate critical habitat for a total of 4,260 acres (1,724 ha) of springs, seeps, streams, stock tanks, and terrestrial space in between these features within the Cienega Creek Natural Preserve in Pima County, Arizona, including the reach of Cienega Creek that occurs within the Cienega Creek Natural Preserve. The Cienega Creek Natural Preserve is owned and managed by Pima County. Native fish and lowland leopard frog populations provide prey for northern Mexican gartersnakes, and recent, ongoing bullfrog eradication in the area reduces the threat of bullfrogs within this subunit. This subunit contains sufficient physical or biological features, including all PCEs. However, special management may be required to maintain or develop the physical or biological features, including preventing the invasion or reinvasion of bullfrogs. This subunit is being considered for exclusion from the final rule for critical habitat under section 4(b)(2) of the Act (see
Application of Section 4(b)(2) of the Act
below).

The Cienega Creek Subbasin Unit is proposed as critical habitat for the northern Mexican gartersnake because it is occupied at the time of listing and contains sufficient physical or biological features to support life-history functions essential for the conservation of the species. The physical or biological features in this unit may require special management consideration due to ongoing and regional threat of bullfrogs.

San Pedro River Subbasin Unit

The San Pedro River Subbasin Unit is generally located in southeastern Arizona, east of Sierra Vista, Tucson, and Florence and west Douglas, Wilcox, and Safford, in Cochise, Pima, and Pinal Counties. This unit consists of a total of 23,690 acres (9,587 ha) along 165 stream mi (266 km) of proposed critical habitat along the San Pedro River and Bear Creek. Land ownership or land management within this unit consists of lands managed by the U.S. Bureau of Land Management, Coronado National Forest, Arizona State Land Department, San Carlos Apache Tribe, and privately owned lands. All identified areas described in the San Pedro River Subbasin Unit have records for northern Mexican gartersnakes, and all identified areas are considered as being currently within the geographical area occupied by the species. Therefore, we are proposing the areas in this unit under section 3(5)(A)(i) of the Act because they are occupied by the species and because they contain sufficient amounts of the essential physical or biological features that may require special management considerations or protection. The following narratives describe all of the subunits proposed as critical habitat in the San Pedro River Subbasin Unit.

San Pedro River Subunit. We are proposing to designate 22,669 acres (9,174 ha) of critical habitat along 158.4 stream mi (254.9 km) of the San Pedro River from its confluence with the Gila River at Winkelman, upstream to the International Border, in Cochise, Pima, and Pinal Counties, Arizona. The San Pedro River Subunit occurs predominately on privately owned lands, with remaining lands managed by the U.S. Bureau of Land Management. Native fish and lowland leopard frogs occur throughout the San Pedro River and provide a prey base for northern Mexican gartersnakes, with prey population densities increasing in the downstream direction. Crayfish, bullfrogs, and nonnative, spiny-rayed fish occur predominately upstream of the Interstate 10 crossing. In general, this subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and 3 (prey base), but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of harmful nonnative species. Lands in this subunit that are owned or under conservation easement with The Nature Conservancy as conservation preserves, lands owned by the Salt River Project and managed under their Horseshoe-Bartlett and Roosevelt HCPs, as well as lands owned by the San Carlos Apache Tribe, are being considered for exclusion from the final rule for critical habitat under section 4(b)(2) of the Act (see
Application of Section 4(b)(2) of the Act
below).

Bear Canyon Creek Subunit. We are proposing to designate 1,022 acres (414 ha) of critical habitat along 7.1 stream mi (11.3 km) of Bear Canyon Creek, from the International Border, upstream

to its origin south of Granite Peak in the Huachuca Mountains, in Cochise County, Arizona. The Bear Canyon Creek Subunit occurs predominately on lands managed by the Coronado National Forest with remaining land in private ownership. Native fish comprise the fishery of Bear Canyon Creek, and GIS analysis suggests that native leopard frogs may also occur in limited density. Crayfish are also present. This subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and 3 (prey base), but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of crayfish and the establishment of secure leopard frog populations.

The San Pedro River Subbasin Unit is proposed as critical habitat for the northern Mexican gartersnake because it is occupied at the time of listing and contains sufficient physical or biological features to support life-history functions essential for the conservation of the species. The physical or biological features in this unit may require special management consideration due to competition with, and predation by, harmful nonnative species that are present in this unit.

Babocomari River Subbasin Unit

The Babocomari River Subbasin Unit is generally located in southeastern Arizona, east of Santa Rita Mountains, north of the Canelo Hills and Huachuca Mountains, south of the Whetstone Mountains, and west of the San Pedro River, in Santa Cruz and Cochise Counties. This unit consists of springs, seeps, streams, stock tanks, and terrestrial space in between these features within a total of 14,334 acres (5,801 ha) of proposed critical habitat in the Canelo Hills Cienega Preserve and Appleton-Whittell Research Ranch as well as along a total of 45 stream mi (72 km) of portions of the Babocomari River, Post Canyon, O'Donnell Canyon, and Turkey Creek. Land ownership or management within this unit consists of lands managed by the U.S. Bureau of Land Management, Coronado National Forest, Arizona State Land Department, and privately owned lands. All identified areas described in the Babocomari River Subbasin Unit have records for northern Mexican gartersnakes, and all identified areas are considered as being currently within the geographical area occupied by the species. Therefore, we are proposing the areas in this unit under section 3(5)(A)(i) of the Act because they are occupied by the species and because they contain sufficient amounts of the essential physical or biological features that may require special management considerations or protection. The following narratives describe all of the subunits proposed as critical habitat in the Babocomari River Subbasin Unit.

Babocomari River/Cienega Subunit. We are proposing to designate 3,454 acres (1,398 ha) of critical habitat along approximately 24.4 stream mi (39.2 km) of the Babocomari River from its confluence with the San Pedro River northwest of Fairbank, upstream to its confluence with an unnamed drainage south of the railroad and southeast of Elgin, in Cochise and Santa Cruz Counties, Arizona. The Babocomari River Subunit occurs predominately on privately owned lands, with remaining lands managed by the U.S. Bureau of Land Management. Crayfish, bullfrogs, and nonnative, spiny-rayed fish all occur within this subunit at various densities, reducing the likelihood of maintaining a suitable native prey base for northern Mexican gartersnakes. This subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics) and 2 (terrestrial habitat characteristics), but PCEs 3 (prey base) and 4 (absence or low level of harmful nonnative species) are deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of harmful nonnative species and reestablishment of native prey species.

Post Canyon Subunit. We are proposing to designate 795 acres (322 ha) of critical habitat along approximately 5.7 stream mi (9.1 km) of Post Canyon, from the western boundary of the Appleton-Whittell Research Ranch, upstream to Post Well at the top of Post Canyon, in Santa Cruz County, Arizona. The Post Canyon Subunit occurs largely on privately owned lands as well as those managed by the Coronado National Forest.

Lowland leopard frogs and, perhaps, Chiricahua leopard frogs provide prey for northern Mexican gartersnakes in Post Canyon. Native fish may also occur due to a connection with nearby habitat that native fish are known to occupy. Crayfish occur in Post Canyon, and nonnative, spiny-rayed fish, as well as bullfrogs, are known from the vicinity and may be present. This subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and 3 (prey base), but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of crayfish and the prevention of potential bullfrog and nonnative, spiny-rayed fish invasions. Lands owned by the Appleton-Whittell Research Ranch within this subunit are being considered for exclusion from the final rule for critical habitat under section 4(b)(2) of the Act (see
Application of Section 4(b)(2) of the Act
below).

O'Donnell Canyon Subunit. We are proposing to designate 398 acres (161 ha) of critical habitat along approximately 2.5 stream mi (4.0 km) of O'Donnell Canyon, between the southern boundary of the Appleton-Whittell Research Ranch upstream to the northern boundary of the Canelo Hills Cienega Preserve, and then from the southern boundary of the Canelo Hills Cienega Preserve upstream to its confluence with Pauline and Middle canyons, in Santa Cruz County, Arizona. The O'Donnell Canyon Subunit occurs predominantly on privately owned lands and those managed by the Coronado National Forest. The area proposed along O'Donnell Canyon is within the area considered occupied by the northern Mexican gartersnake.

Populations of native fish and Chiricahua leopard frogs provide a prey base for northern Mexican gartersnakes in O'Donnell Canyon, but crayfish and nonnative, spiny-rayed fish may be present. Bullfrogs inhabit the region and present a threat of invasion. This subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and 3 (prey base), but PCE 4 (absence or low level of harmful nonnative species) is deficient. Special management may be required to maintain or develop the physical or biological features, including the elimination or reduction of crayfish and nonnative, spiny-rayed fish, as well as the prevention of potential bullfrog invasions. Lands owned by the Appleton-Whittell Research Ranch and the Canelo Hills Cienega Preserve within this subunit are being considered for exclusion from the final rule for critical habitat under section 4(b)(2) of the Act (see
Application of Section 4(b)(2) of the Act
below).

Turkey Creek Subunit. We are proposing to designate 1,678 acres (679 ha) of critical habitat along approximately 12.0 stream mi (19.4 km) of Turkey Creek, from its confluence with the Babocomari River, upstream to the northern boundary of the Appleton-Whittell Research Ranch, and then from

the southwestern boundary of the Appleton-Whittell Research Ranch to its origin at an unnamed pond east of State Highway 83 and south of Forest Road 201, in Santa Cruz and Cochise Counties. The Turkey Creek Subunit occurs predominantly on privately owned lands and those managed by the Coronado National Forest.

Turkey Creek historically supported two species of native fish, which could still remain and supplement possible resident amphibian prey sources. One bullfrog was detected in 2004 within Turkey Creek, but no crayfish or nonnative, spiny-rayed fish species are thought to currently occur there. This subunit contains sufficient physical or biological features, including PCEs 1 (aquatic habitat characteristics), 2 (terrestrial habitat characteristics), and 4 (absence or low level of harmful n

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2013-16520. Public record. Not legal advice.