# Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List a Distinct Population Segment of the Fisher in Its United States Northern Rocky Mountain Range as Endangered or Threatened With Critical Habitat

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2011-16349

## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** June 30, 2011
- **Citation:** 76 FR 38504

## Text

DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R6-ES-2010-0017; MO 92210-0-0008]
Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List a Distinct Population Segment of the Fisher in Its United States Northern Rocky Mountain Range as Endangered or Threatened With Critical Habitat

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Notice of 12-month petition finding.

SUMMARY:

We, the U.S. Fish and Wildlife Service (Service), announce a 12-month finding on a petition to list a distinct population segment (DPS) of the fisher (
Martes pennanti
) in its U.S. Northern Rocky Mountain range, including portions of Montana, Idaho, and Wyoming, as endangered or threatened and designate critical habitat under the Endangered Species Act of 1973, as amended (Act). After review of all available scientific and commercial information, we find that listing the fisher in the U.S. Northern Rocky Mountains as threatened or endangered is not warranted at this time.

DATES:

The finding announced in this document was made on June 30, 2011.

ADDRESSES:

This finding is available on the Internet at
http://www.regulations.gov
at Docket Number FWS-R6-ES-2010-0017. Supporting documentation we used in preparing this finding is available for public inspection, by appointment, during normal business hours at the U.S. Fish and Wildlife Service, Montana Field Office, 585 Shepard Way, Helena, MT 59601; telephone (406) 449-5225. We ask the public to submit any new information that becomes available concerning the status of, or threats to, the fisher, in addition to new information, materials, comments, or questions concerning this finding, to the above address. No information will be accepted by facsimile. The petition finding, related
Federal Register
notices, and other pertinent information, may be obtained online at
http://www.fws.gov/mountain-prairie/species/mammals/fisher/
.

FOR FURTHER INFORMATION CONTACT:

Mark Wilson, Field Supervisor, Montana Ecological Services Field Office (see
ADDRESSES
); or by telephone at (406) 449-5225. If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at (800) 877-8339.

SUPPLEMENTARY INFORMATION:

Background

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

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

Previous Federal Actions

U.S. Northern Rocky Mountains

On March 6, 2009, we received a petition dated February 24, 2009, from the Defenders of Wildlife, Center for Biological Diversity, Friends of the Bitterroot, and Friends of the Clearwater (petitioners) requesting that the fisher in the Northern Rocky Mountains of the United States (USNRMs) be considered a DPS and listed as endangered or threatened, and critical habitat be designated under the Act (Defenders of Wildlife
et al.
2009, entire). In an April 9, 2009, letter to the petitioners, we responded that we had reviewed the information presented in the petition and determined that issuing an emergency regulation temporarily listing the species under section 4(b)(7) of the Act was not warranted (Guertin 2009, entire). We informed the petitioners that due to staffing and funding constraints in Fiscal Year 2009, we would not be able to further address the petition at that time, but would complete the action when resources allowed. We published a 90-day finding on April 16, 2010, stating that the petition presented substantial information that listing a DPS of fisher in the USNRMs may be warranted, and initiated a status review of the species (75 FR 19925). The notice of a 90-day finding and commencement of a 12-month status review for the USNRMs DPS was published in the annual Candidate Notice of Review on November 10, 2010 (75 FR 69222).

Fishers in the USNRMs were previously petitioned for listing with a U.S. Pacific States' population in 1994 (see below).

U.S. Pacific States

On June 5, 1990, we received a petition dated May 29, 1990, from Mr. Eric Beckwitt, Forest Issues Task Force, Sierra Biodiversity Project, and others requesting that the Pacific fisher (
Martes pennanti pacifica
) be listed as an endangered species in California, Oregon, and Washington under the Act. On January 11, 1991, we published a 90-day finding (56 FR 1159) indicating that the fisher in the Pacific States is a distinct population that is geographically isolated from populations in the Rocky Mountains and British Columbia and represents a listable entity under the Act. The finding also indicated that the petition had not presented substantial information indicating that a listing may be warranted because of a lack of information on fisher habitat needs, population size and trends, and demographic parameters (56 FR 1159).

On December 29, 1994, we received a petition dated December 22, 1994, from the Biodiversity Legal Foundation requesting that two fisher populations in the western United States, including the States of Washington, Oregon, California, Idaho, Montana, and Wyoming, be listed as threatened under the Act. Based on our review, we found that the petition did not present substantial information indicating that listing the two western United States fisher populations as a DPS was warranted (61 FR 8016, March 1, 1996). The best available scientific evidence at that time indicated that the range of the fisher was contiguous across Canada with some areas having abundant populations, and through southward peninsular extensions, was contiguous with the U.S. Rocky Mountain and Pacific populations (61 FR 8016). No evidence was presented in the petition to support physical, physiological, ecological, or behavioral separations (61 FR 8016).

On December 5, 2000, we received a petition dated November 28, 2000, from 12 organizations, with the lead organizations identified as the Center for Biological Diversity and the Sierra Nevada Forest Protection Campaign, requesting that the West Coast DPS of

the fisher, including portions of California, Oregon, and Washington, be listed as endangered and critical habitat be designated under the Act. A court order was issued on April 4, 2003, by the U.S. District Court, Northern District of California, that required the Service to submit for publication in the
Federal Register
a 90-day finding on the 2000 petition (
Center for Biological Diversity, et al.
v.
Norton et al., No. C 01—2950 SC
). On July 10, 2003, we published a 90-day petition finding that the petition provided substantial information that listing may be warranted and initiated a 12-month status review (68 FR 41169).

On April 8, 2004, we published a warranted 12-month finding for listing of the fisher's West Coast DPS (69 FR 18770). A listing action was precluded by higher priorities and the West Coast DPS was added to our candidate species list. On April 8, 2010, the Center for Biological Diversity, Sierra Forest Legacy, Environmental Protection Information Center, and Klamath-Siskiyou Wildlands Center filed a complaint in the United States District Court for the Northern District of California seeking an order for the Service to withdraw the 2004 warranted-but-precluded finding and proceed with a proposed rule to list the species under the Act (
Center for Biological Diversity, et al.
v.
Salazar, et al., No. CV 10—1501
). A resolution of the complaint is pending.

The West Coast fisher was included in the Service's candidate notices of review in 2005, 2006, 2007, 2008, 2009, and 2010 (70 FR 24870, May 11, 2005; 71 FR 53756, September 12, 2006; 72 FR 69034, December 6, 2007; 73 FR 75176, December 10, 2008; 74 FR 57804, November 9, 2009; 75 FR 69222, November 10, 2010).

Species Information

This “Species Information” section concentrates on general biology and fisher studies conducted in the USNRMs area. Additional information regarding fisher biology in the western portion of its range can be found in the Service's 12-month finding on a petition to list the West Coast DPS of the fisher (69 FR 18770).

Description

The fisher is a forest-dwelling, medium-sized mammal, light brown to dark blackish-brown in color, with the face, neck, and shoulders sometimes being slightly gray (Powell 1981, p. 1). The chest and underside often have irregular white patches. The fisher has a long body with short legs and a long bushy tail. Males range in length from 90 to 120 centimeters (cm) (35 to 47 inches (in.)), and females range from 75 to 95 cm (29 to 37 in.) in length. At 3.5 to 5.5 kilograms (kg) (7.7 to 12.1 pounds (lbs)), male fishers weigh about twice as much as females (2.0 to 2.5 kg (4.4 to 5.5 lbs)) (Powell
et al.
2003, p. 638). Heavier males have been reported across the range, including individuals within the USNRMs (Sauder 2010 unpublished data; Schwartz 2010 unpublished data); an exceptional specimen from Maine weighed 9 kg (20.1 lbs) (Blanchard 1964, pp. 487-488). Fishers may show variation in typical body weight regionally, corresponding with latitudinal gradients. For example, fishers in the more southern latitudes of the U.S. Pacific States may weigh less than fishers in the eastern United States and Canada (Seglund 1995, p. 21; Dark 1997, p. 61; Aubry and Lewis 2003, p. 87; Lofroth
et al.
2010, p. 10).

Taxonomy

The “Fisher of Pennant,” or
Mustela pennantii,
was formally described by Erxleben in 1777, based on accounts of the same specimen from either the eastern United States or eastern Canada, by Buffon in 1765 and the naturalist Thomas Pennant in 1771 (Rhoads 1898 as cited in Goldman 1935, p. 177; Powell 1981, p. 1). Taxonomic stability was not attained until 80 years after Buffon's original description, when taxonomists transferred the fisher to the genus
Martes
and changed the spelling of the species to
pennanti
(Hagmeier 1959, p. 185; Powell 1981, p. 1; Powell 1993, pp. 11-12).

The fisher is classified in the order Carnivora, family Mustelidae, a family that also includes weasels, mink, martens, and otters (Anderson 1994, p. 14). It is the largest member of the genus
Martes,
classified as subgenus
Pekania,
and occurs only in North America (Anderson 1994, pp. 22-23). Its geographic range overlaps extensively with that of the American marten (
Martes americana
—subgenus
Martes
), the only other
Martes
species in North America (Gibilisco 1994, p. 59). Characteristic of the subgenus
Pekania
is large body size compared with other
Martes
and the presence of an external median rootlet on the upper carnassial (fourth) premolar (Anderson 1994, p. 21).

Goldman (1935, p. 177) recognized three subspecies of fisher based on differences in skull dimensions, although he stated they were difficult to distinguish: (1)
Martes pennanti pennanti
in the east and central regions; (2)
M. p. columbiana
in the central and northwestern regions that include the USNRMs; and (3)
M. p. pacifica
in the western coast States of the United States. A subsequent analysis questioned whether there is a sufficient basis to support recognition of different subspecies based on numerous factors, including the small number of samples available for examination (Hagmeier 1959, p. 193). Regional variation in characteristics used by Goldman to discriminate subspecies appears to be clinal (varying along a geographic gradient), and the use of clinal variations is “exceedingly difficult to categorize subspecies” (Hagmeier 1959, pp. 192-193). Although subspecies taxonomy as described by Goldman (1935, p. 177) is often used in literature to describe or reference fisher populations in different regions of its range, and recent consideration of genetic variation indicates patterns of population subdivision similar to the earlier described subspecies (Kyle
et al.
2001, p. 2345; Drew
et al.
2003, p. 59), it is not clear whether Goldman's designations of subspecies are taxonomically valid. Therefore, for the purposes of this finding, we are evaluating the fisher in the USNRMs as a DPS of a full species (
i.e., M. pennanti
).

Biology

Fishers are opportunistic predators, primarily of snowshoe hares (
Lepus

americanus
), squirrels (
Tamiasciurus,

Sciurus,

Glaucomys,
and
Tamias
spp.), mice (
Microtus, Clethrionomys,
and
Peromyscus
spp.), and birds (numerous spp.) (reviewed in Powell 1993, pp. 18, 102). Carrion and plant material (
e.g.,
berries) also are consumed (Powell 1993, p. 18). The fisher is one of the few predators that successfully kills porcupines (
Erethizon

dorsatum
), and porcupine remains have been found more often in the gastrointestinal tract and scat of fisher than in any other predator (Powell 1993, p. 135). There is only one study reporting the food habits of an established fisher population in the USNRMs, and that study confirms that snowshoe hares, voles (
Microtus
and
Clethrionomys
spp.), and red squirrels (
Tamiasciurus hudsonicus
) are similarly important prey in north-central Idaho as they are in other parts of the range (Jones 1991, p. 87). Fishers from Minnesota relocated to the Cabinet Mountains of Montana subsisted primarily on snowshoe hare and deer (
Odocoileus
spp.) carrion (Roy 1991, p. 29). As dietary generalists, fishers across their range tend to forage in areas where prey is both abundant and vulnerable to capture (Powell 1993, p. 100). Fishers in north-central Idaho exhibit seasonal shifts in habitat use to forests with younger successional structure plausibly linked to a concurrent

seasonal shift in habitat use by their prey species (Jones and Garton 1994, p. 383).

Fishers are estimated to live up to 10 years (Arthur
et al.
1992, p. 404; Powell
et al.
2003, p. 644). Both sexes reach maturity their first year but may not be effective breeders until 2 years of age (Powell
et al.
2003, p. 638). Fishers are solitary except during the breeding season, which is generally from late February to the middle of May (Wright and Coulter 1967, p. 77; Frost
et al.
1997, p. 607). The breeding period in north-western Montana and north-central Idaho is approximately late February through April based on observations of significant changes of fisher movement patterns and examination of the reproductive tracts of harvested specimens (Weckwerth and Wright 1968, p. 980; Jones 1991, pp. 78-79; Roy 1991, pp. 38-39). Uterine implantation of embryos occurs 10 months after copulation; active gestation is estimated to be between 30 and 60 days; and birth occurs nearly 1 year after copulation (Wright and Coulter 1967, pp. 74, 76; Frost
et al.
1997, p. 609; Powell
et al.
2003, p. 639).

Litter sizes for fishers range from one to six, with a mean of two to three kits (Powell
et al.
2003, pp. 639-640). Potential litter sizes in the USNRMs are between two to three per female, based on the frequency of embryos recovered from harvested females (Weckwerth and Wright 1968, p. 980; Jones 1991, p. 84). Newborn kits are entirely dependent and may nurse for 10 weeks or more after birth (Powell 1993, p. 67). Kits develop their own home ranges by 1 year of age (Powell
et al.
2003, p. 640). Populations of fisher fluctuate in size, and reproductive rates may vary widely from year to year in response to the availability of prey (Powell and Zielinski 1994, p. 43).

An animal's home range is the area traversed by the individual in its normal activities of food gathering, mating, and caring for young (Burt 1943, p. 351). Only general comparisons of fishers' home range sizes can be made, because studies across the range have been conducted by different methods. Generally, fishers have large home ranges, male home ranges are larger than females, and fisher home ranges in British Columbia and the USNRMs are larger than those in other areas in the range of the taxon (reviewed in Powell and Zielinski 1994, p. 58; reviewed in Lofroth
et al.
2010, pp. 67-70). Fisher home ranges vary in size across North America and range from 16 to 122 square kilometers (km
2
) (4.7 to 36 square miles (mi
2
)) for males, and from 4 to 53 km
2
(1.2 to 15.5 mi
2
) for females (reviewed by Powell and Zielinski 1994, p. 58; Lewis and Stinson 1998, pp. 7-8; Zielinski
et al.
2004, p. 652). In north-central Idaho, the movements of a small number of radio-collared fishers indicated that males range from approximately 30 to 120 km
2
(8.7 to 35 mi
2
) year round, and females range from 6 to 75 km
2
(1.7 to 22 mi
2
), with a slight reduction in summer (Jones 1991, pp. 82-83). Fishers in Idaho have home ranges larger than any other home ranges reported within the range of the taxon (Idaho Office of Species Conservation (IOSC) 2010, p. 4).

The abundance or availability of vulnerable prey may play a role in home range selection (Powell 1993, p. 173; Powell and Zielinski 1994, p. 57). Fishers exhibit territoriality, with little overlap between members of the same sex; in contrast, overlap between opposite sexes is extensive, and size and overlap are possibly related to the density of prey (Powell and Zielinski 1994, p. 59). Male fishers may extend or temporarily abandon their territories to take long excursions during the breeding season from the end of February to April presumably to increase their opportunities to mate (Arthur 1989a, p. 677; Jones 1991, pp. 77-78). However, males who maintained their home ranges during the breeding season were more likely to successfully mate than were nonresident males encroaching on an established range (Aubry
et al.
2004, p. 215).

It is not known how fishers maintain territories; it is possible that scent marking plays an important role (Leonard 1986, p. 36; Powell 1993, p. 170). Direct aggression between individuals in the wild has not been observed, although signs of fishers fighting and the capture of male fishers with scarred pelts have been reported (Douglas and Strickland 1987, p. 516). Combative behavior has been observed between older littermates and between adult females in captivity (Powell and Zielinski 1994, p. 59).

There is little information available regarding the long-distance movements of fishers, although long-distance movements have been documented for dispersing juveniles and recently relocated individuals before they establish a home range. Fishers relocated to novel areas in Montana's Cabinet Mountains and British Columbia moved up to 163 km (100 mi) from release sites, crossing large rivers and making 700-m (2,296-ft) elevation changes (Roy 1991, p. 42; Weir and Harestad 1997, pp. 257, 259).

Juveniles dispersing from natal areas are capable of moving long distances and navigating various landscape features such as highways, rivers, and rural communities to establish their own home range (York 1996, p. 47; Weir and Corbould 2008, p. 44). In Maine and British Columbia, juveniles dispersed from 0.7 km (0.4 mi) to 107 km (66.4 mi) from natal areas (York 1996, p. 55; Weir and Corbould 2008, p. 44). Dispersal characteristics may be influenced by factors such as sex, availability of unoccupied areas, turnover rates of adults, and habitat suitability (Arthur
et al.
1993, p. 872; York 1996, pp. 48-49; Aubry
et al.
2004, pp. 205-207; Weir and Corbould 2008, pp. 47-48). Long-distance dispersal by vulnerable, less experienced individuals is made at a high cost and is not always successful. Fifty-five percent of transient fishers in a British Columbia study died before establishing home ranges, and only one in six juveniles successfully established a home range (Weir and Corbould 2008, p. 44). One dispersing juvenile female traveled an unusually long distance of 135 km (84 mi) over rivers and through suboptimal habitats before succumbing to starvation (Weir and Corbould 2008, p. 44). Individuals traveling longer distances are subject to greater mortality risk (Weir and Corbould 2008, p. 44), and very few establish the stability of a home range, which improves the chance of successful recruitment (Aubry
et al.
2004, p. 215).

Habitat

The occurrence of fishers at regional scales is consistently associated with low- to mid-elevation environments of mesic (moderately moist), coniferous and mixed conifer and hardwood forests with abundant physical structure near the ground (reviewed by Hagmeier 1956, entire; Arthur
et al.
1989a, pp. 683-684; Banci 1989, p. v; Aubry and Houston 1992 p. 75; Jones and Garton 1994, pp. 377-378; Powell 1994, p. 354; Powell
et al.
2003, p. 641; Weir and Harestad 2003, p. 74). Fishers avoid areas with little or no cover (Powell and Zielinski 1994, p. 39; Buskirk and Powell 1994, p. 286); an abundance of coarse woody debris, boulders, shrub cover, or subterranean lava tubes sometimes provide suitable overhead cover in non-forested or otherwise open areas (Buskirk and Powell, 1994, p. 293; Powell
et al.
2003, p. 641). In the understory, the physical complexity of coarse woody debris such as downed trees and branches provides a diversity of foraging and resting locations (Buskirk and Powell 1994, p. 295).

Forest succession is a dynamic continuum that begins with an event such as wildfire, windthrow (areas of downed trees due to high winds) or

timber harvest that removes or alters major components of an environment. Over time the affected environment experiences a series of changes or seral stages in vegetation species and structure. In the absence of disturbance and over many decades to hundreds of years depending on the forest type, mature or late-seral structure and species composition may result. Late-seral forests (also known as old-growth) are generally characterized by more diversity of structure and function than younger developmental stages. Specific characteristics of late-seral forests vary by region, forest type, and local conditions. Fishers are associated more commonly with mature forest cover and late-seral forests with greater physical complexity than other habitats (reviewed by Powell and Zielinski 1994, p. 52). Other forest successional stages may suffice if adequate cover and structure is provided. For example, extensive, mid-mature, second growth forests are used by fishers in the Northeast and Midwest United States (Coulter 1966, pp. 59-60; Arthur
et al.
1989b, pp. 680-683; Powell 1993, p. 92).

To what extent late successional forests are required to support fisher may be dependent on scale (Powell
et al.
2003, p. 641). Home ranges may be established based on attributes at a landscape scale, foraging at a site scale, and resting and denning use based on the element or structural scale (Powell 1993, p. 89; Buskirk and Powell 1994, p. 284; Weir and Corbould 2008, p. 103). Within areas of low and mid-elevation forests, the most consistent predictor of fisher occurrence at larger spatial scales is moderate to high levels of contiguous canopy cover rather than any particular forest plant community (Buck 1982, p. 30; Arthur
et al.
1989b, pp. 681-682; Powell 1993, p. 88; Jones and Garton 1994, p. 41; Weir and Corbould 2010, p. 408). In north-central Idaho, mature to old-growth mesic forests of grand and subalpine fir in close proximity to riparian areas are used extensively (Jones 1991, pp. 90, 113; Jones and Garton 1994, p. 381); fishers in this study avoided forests with less than 40 percent crown cover and drier upland sites composed of
Abies grandis
(grand fir),
Abies lasiocarpa
(subalpine fir),
Pseudotsuga menziesii
(Douglas fir), and
Pinus ponderosa
(ponderosa pine) (Jones 1991, p. 90). A preliminary analysis of habitat associations in the USNRMs indicates that in summer, fishers select areas with larger diameter trees and landscapes with a higher proportion of large trees, and avoid dry areas typically populated by ponderosa pine (Schwartz 2010, unpublished data). Winter detections of fisher are more likely in drainages with a high amount of canopy cover, and winter avoidance of dry areas is similar to summer (Schwartz 2010, unpublished data). Fishers in Idaho include forested environments of differing configurations in their home range including roadless areas, industrial forest, and national forests managed for multiple uses (Albrecht and Heusser 2009, p. 19; IOSC 2010, p. 4).

The physical structure of the forest and prey associated with forest structures are thought to be critical features that explain fisher habitat use, rather than specific forest types (Buskirk and Powell 1994, p. 286), and the composition of individual fisher home ranges is usually a mosaic of different forested environments and successional stages (reviewed by Lofroth
et al.
2010, p. 94). Further, fishers are opportunistic predators with a relatively general diet, and the vulnerability of prey may be more important to the use of an area for foraging than the abundance of a particular prey species (Powell and Zielinski 1994, p. 54). In north-central Idaho, fishers expand their use of young forest stages in winter, likely in response to a seasonal shift in habitat use by their prey or an increase in prey vulnerability in these areas (Jones and Garton 1994, p. 383). Individuals translocated to the Cabinet Mountains of Montana from Minnesota and Wisconsin exhibit winter habitat use similar to that reported for fishers in north-central Idaho (Roy 1991, p. 60). Fishers in north-central Idaho and Montana also select forest riparian areas and draws or valley bottoms that have a strong association with spruce, which tend to have dense cover, high densities of snowshoe hare, and a diversity of other prey types (Powell 1994, p. 354; Jones 1991, pp. 90-93; Heinemeyer 1993, p. 90).

Fishers are more selective of habitat for resting than they are about foraging or traveling habitat (Arthur
et al.
1989b, p. 686; Powell and Zielinski 1994, p. 54; Powell 1994, p. 353). Across the range, fishers select resting sites with characteristics of late successional forests—higher canopy closure, large-diameter trees, coarse downed wood, and singular features of large snags, tree cavities, or deformed trees (Powell and Zielinski 1994, p. 54; Lofroth
et al.
2010, pp. 101-103). Rest sites may be selected for their insulating or thermoregulatory qualities and their effectiveness at providing protection from predators (Weir
et al.
2004, pp. 193-194). Resting locations for fishers in north-central Idaho are predominately in mature forest types (Jones and Garton 1994, p. 383). When fishers use younger forest types, they will select large-diameter trees or snags, if present, that are remnants of a previously existing older forest stage (Jones 1991, p. 92). Because of this selectivity for mature forest type or structure, resting and denning sites may be more limiting to fisher distribution than foraging habitats, and should receive particular consideration in managing habitat for fishers (Powell and Zielinski 1994, pp. 56-57).

Cavities and branches in trees, snags, stumps, rock piles, and downed timber are used as resting sites, and cavities in large-diameter live or dead trees are selected more often for natal and maternal dens (Powell and Zielinski 1994, pp. 47, 56). Fishers do not appear to excavate their own natal or maternal dens; therefore, other factors (
i.e.,
heartwood decay of trees, excavation by woodpeckers, broken branches, frost or fire scars) are important in creating cavities and narrow entrance holes (Lofroth
et al.
2010, p. 112). The tree species may vary from region to region based on local influences. In regions where both hardwood and conifers occur, hardwoods are selected more often, although they may be a minor component of the area (Lofroth
et al.
2010, p. 115). Den trees tend to be older and larger in diameter than other available trees in the vicinity (reviewed by Lofroth
et al.
2010, pp. 115, 117). Little is known of natal or maternal den use or selection in the USNRMs. A habitat study conducted in north-central Idaho found no kits or evidence of denning (Jones 1991, p. 83). A female introduced into Montana's Cabinet Mountains used a downed hollow log for a natal den only months after release, and it is likely that this suboptimal site was selected only because of the female's unfamiliarity with the area (Roy 1991, p. 56).

Snow conditions and ambient temperatures may affect fisher activity and habitat use. Fishers in eastern parts of the taxon's range may be less active during winter and avoid areas where deep, soft snow inhibits movement (Leonard 1980, pp. 108-109; Raine 1981, p. 74). Historical and current fisher distributions in California and Washington are consistent with forested areas that receive low or lower relative snowfall (Krohn
et al.
1997, p. 226; Aubry and Houston 1992, p. 75). Fishers in Ontario, Canada, moved from low-snow areas to high-snow areas during population increases, indicating a possible density-dependent migration to less suitable habitats factored by snow conditions (Carr
et al.
2007, p. 633). These distribution and activity patterns

suggest that the presence of fisher and their populations may be limited by deep snowfall. However, the reaction to snow conditions appears to be variable across the range, with fishers in some locations not affected by snow conditions or increasing their activity with fresh snowfall (Jones 1991, p. 94; Roy 1991, p. 53; Weir and Corbould 2007, p. 1512). Thus, fishers' reaction to snow may be dependent on a myriad of factors, including, but not limited to, local freeze-thaw cycles, the rapidity of crust formation, snow interception by the forest canopy, and prey availability (Krohn
et al.
1997, p. 226; Mote
et al.
2005, p. 44; Weir and Corbould 2007, p. 1512).

Historical Distribution Across the Range of the Species

Fishers occur only in North America, appearing in the fossil record approximately 30,000 years ago in the eastern United States throughout the Appalachian Mountains, south to Georgia, Alabama, and Arkansas, and west to Ohio and Missouri (Anderson 1994, p. 18). No fossil evidence of a fisher range expansion to the north or west exists until the middle Holocene (4,000 to 8,000 years ago) in southern Wisconsin, and only within the past 4,000 years is there evidence that fishers inhabited northwestern North America (Graham and Graham 1994, pp. 46, 58). Although there is limited fossil evidence available from central Canada, fishers' expansion westward and northward likely coincided with glacier retreat and the subsequent development of the boreal spruce forests (Graham and Graham 1994, p. 58). Fossil remains of early fisher in the northwest have been found in British Columbia, Washington, and Oregon, and no fossil remains have been discovered in the USNRMs region (Graham and Graham 1994, pp. 50-55).

Our present understanding of the historical (before European settlement) distribution of fishers is based on the accounts of natural historians of the early 20th century and general assumptions of what constitutes fisher habitat. The presumed fisher range prior to European settlement of North America (c. 1600) was throughout the boreal forests across North America in Canada from approximately 60° north latitude, extending south into the United States in the Great Lakes area and along the Appalachian, Rocky, and Pacific Coast Mountains (Figure 1) (Hagmeier 1956, entire; Hall 1981, pp. 985-987; Powell 1981, pp. 1-2; Douglas and Strickland 1987, p. 513; Gibilisco 1994, p. 60).

The distribution of fishers has been described by numerous authors, and the distribution boundaries vary depending on the evidence used for occurrences. The presumed presence of fishers has been drawn along the lines of forest distribution, and the species has been consistently described as an associate of boreal forest in Canada, mixed deciduous-evergreen forests in eastern North America, and coniferous forest ecosystems in the west (Lofroth
et al.
2010, p. 39). Subsequently, range maps of historical distribution typically portray large areas of continuous occurrence, although it is likely that the suitability of habitat to support fishers within the portrayed range varied over time and spatial scales, subject to climatic variation, large-scale disturbances, and other ecological factors (Giblisco 1994, p. 70; Graham and Graham 1994, pp. 57-58). Fishers do not occur in all forested habitats today, and evidence would indicate they did not occupy all forest types in the past (Graham and Graham 1994, p. 58). Based on the contemporaneous assemblages of fossilized remains, it is likely that habitat selection by fishers has historically been influenced by the availability of specific types of prey (Graham and Graham 1994, p. 58).

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Post-European Settlement Distribution Across the Range of the Species

In the late 1800s and early 1900s, fishers experienced reductions in range, decreases in population numbers, and local extirpations attributed to overtrapping, predator control, or habitat destruction in the United States, including the USNRMs, and to a lesser extent in Canada (Weckwerth and Wright 1968, p. 977; Brander and Books 1973, p. 53; Douglas and Strickland 1987, p. 512; Powell and Zielinski 1994, p. 39). Since the 1950s, fishers have

recovered in some of the central (Minnesota, Wisconsin, Michigan) and eastern (Northeastern States and West Virginia) portions of their historical range in the United States as a result of trapping closures and regulations, habitat regrowth, and reintroductions (Brander and Books 1973, pp. 53-54; Powell 1993, p. 80; Gibilisco 1994, p. 61; Lewis and Stinson 1998, p. 3; Proulx
et al.
2004, pp. 55-57; Kontos and Bologna 2008, entire). Fishers have not returned to the areas south of the Great Lakes to the southern Appalachian States (Proulx
et al.
2004, p. 57). The historical, early European settlement, and contemporary distribution of fishers in the USNRMs is discussed in detail in the following sections.

Current Distribution Outside of the U.S. Northern Rocky Mountains

Presently, fishers are found in all Canadian provinces and territories except Newfoundland and Prince Edward Island (Proulx
et al.
2004, p. 55) (Figure 1). The fisher range in Quebec, Ontario, and eastern Manitoba is contiguous with currently occupied areas in New England, northern Atlantic States, Minnesota, Wisconsin, and the Upper Peninsula of Michigan in the United States (Proulx
et al.
2004, pp. 55-57). In Saskatchewan and Alberta, fishers are found primarily north of 52 degrees and 54 degrees north latitude, respectively, and form no known breeding population with the United States (Proulx
et al.
2004, p. 58). In Alberta, trapping data indicate that a rare fisher may occur to the south of high-density population areas to approximately 32 km (20 mi) north of the United States border along the Continental Divide near Waterton Lakes National Park, (Corrigan 2010, pers. comm.; Hale 2010, pers. comm.)—an area contiguous with the USNRMs. However, there is no indication that there is a population of fisher in southern Alberta or whether the source of the occasional rare fisher detected there is the distant fisher population of central Alberta, central British Columbia, or the USNRMs. Fishers occupy low- to mid-elevation forested areas throughout British Columbia, but are rare or absent from the coast and from the southern region for at least 200 km (125 mi) to the border with the United States (Weir
et al.
2003, p. 25; Weir and Lara Almuedo 2010, p. 36).

After reviewing known distribution records for fishers in 1956, Hagmeier (p. 156) noted that there were no known records from southeastern British Columbia, which includes the Rocky Mountains in the eastern Kootenay Region contiguous with northern Idaho and northwest Montana. A reintroduction of fishers to the Kootenay Region of southeast British Columbia, an area just north of the USNRMs, was attempted in the 1990s (Fontana
et al.
1999, entire), but “the observed survival rate of translocated adults and the few cases of confirmed reproduction in the area were not likely sufficient for the population to expand and become self-sustaining” (Weir
et al.
2003, p. 25). The South Thompson Similkameen area of south-central British Columbia, bordering north-central Washington, produced 88 legally harvested fishers between 1928 and 2007, and 13 since 1985 (Lofroth
et al.
2010, p. 48). Because the northern boundary of the South Thompson Similkameen is considered the southern extent of the fisher population distribution in the province (Weir and Lara Almuedo 2010, p. 36), the significance of the trapping data to fisher distribution is not clear without more specific location information. Harvest data could indicate that individuals were captured at the periphery of larger, established populations, that there is a low-density population in south-central British Columbia, or that individuals represent transient or extralimital (outside an established population area) records.

In the western United States outside of the USNRMs, fishers occur in a few disjunct and relatively small areas of their former range in the Cascade Mountains of southwest Oregon, the Klamath and Coastal Ranges of southwest Oregon and northwest California, and the Southern Sierra Nevada Mountains in east-central California (Proulx
et al.
2004; Lofroth
et al.
2010, pp. 47-49). A reintroduction program is underway on the Olympic Peninsula of Washington State, and the program's objective of establishing a self-sustainable population of fisher has yet to be achieved (Lewis
et al.
2009, p. 3).

Historical Distribution and Early European Settlement Distribution in the U.S. Northern Rocky Mountains

Presumed historical distribution of fishers in the USNRMs is depicted as continuous with eastern British Columbia and southwestern Alberta in Canada, bounded on the east by the forested areas of the front range of the Rocky Mountains at approximately 113 degrees west longitude in Montana, the south at approximately 44 degrees north latitude, and the west in Idaho at approximately 116.5 degrees west longitude, extending to the northwest, north of the Palouse Prairie in Idaho to include the forested Pend Oreille River area of northeastern Washington (Hagmeier 1956, entire; Hall 1981, pp. 985-987; Gibilisco 1994, p. 64) (Figure 1). The described historical distribution also includes individually isolated areas in the present-day Greater Yellowstone Ecosystem (northwest Wyoming, southern Montana and east-central Idaho), and north-central Utah (Gibilisco 1994, p. 64). The representation of historical fisher distribution in the USNRMs by the sources above should be viewed cautiously, because it is based on limited information and records collected in the late 1800s to mid-1900s (Hagmeier 1956, pp. 154, 156, 161, 163; Hall 1981, p. 985) after European settlement had influence in the area. In addition, as stated previously, fishers have been consistently described as associates of coniferous forest ecosystems in the west, and the presumed historical presence of fishers was drawn along the lines of forest distribution, with little physical evidence of whether fishers occupied those habitats.

Montana

No reliable records are available for Montana, and historical and early settlement distribution in the western forested areas of the State was assumed based on the reports of the presence of fishers in northwest Wyoming and central Idaho (Hagmeier 1956, p. 156). Vinkey (2003, pp. 44-69) investigated fisher records in the Rocky Mountains, concentrating on Montana, to determine the fisher distribution post-settlement and prior to their apparent disappearance in the 1920s (Newby and McDougal 1964, p. 487; Weckworth and Wright 1968, p. 977). The first reference to fisher in Montana was a shipping record of pelts from Fort Benton in 1875 (Vinkey 2003, p. 49). Although shipping records are not definitive of the product origin, it is likely some of the fisher pelts were of Montana origin because of Montana's prominence in the fur trade and Fort Benton's location at the upper reaches of the Missouri River (Vinkey 2003, p. 49).

Reports of fishers in Montana's Glacier National Park in the early 1900s were dismissed as “unreliable” and “unauthentic” by Newby (cited in Hagmeier 1956, p. 156); nevertheless, these records have been cited by other authors, in addition to reports from early trappers, to support a distribution of fishers in Montana as far south as Wyoming (Hoffman
et al.
1969, p. 596; Vinkey 2003, p. 50). Hoffman
et al.
(1969, p. 596) interpreted the lack of reliable records as an indication of the fisher's extirpation in Montana and adjacent areas before any specimens

could be preserved. Thus, in Montana, the presumed occurrence of fishers before translocations occurred in 1959 is based on trapper accounts alone (Weckworth and Wright 1968, p. 977; Hoffman
et al.
1969, p. 596).

Idaho

The historical presence of fisher in Idaho was based on an 1890 specimen from Alturas Lake (originally Sawtooth Lake) in the Sawtooth Mountains of Blaine County in central Idaho (Goldman 1935, p. 177; Hagmeier 1956, p. 154; Drew
et al.
2003, p. 62; Schwartz 2007, p. 922), and other 20th century reports of fishers in the “mountainous parts of the state,” including the Selkirk (north), Bitterroot (northeast), and Salmon River (central) ranges (Hagmeier 1956, p. 154). Only two fisher specimens document the presence of fishers in the USNRMs prior to their presumed extirpation in the 1920s (Williams 1963, p. 9). Both specimens originated in Idaho. The above-mentioned 1890 specimen from Alturas Lake, Blaine County, in central Idaho is housed in the collection of the National Museum of Natural History in Washington, DC, and this specimen has been pivotal for supporting historical distribution and post-settlement representation, and for suggesting that an indigenous population has survived since the 1920s in the USNRMs (Hagmeier 1956, p. 154; Hall 1981, p. 985; Drew
et al.
2003, pp. 59, 62; Vinkey
et al.
2006, p. 269). An 1896 Harvard Museum specimen collected in Idaho County in north-central Idaho west of the Bitterroot Divide, which separates Idaho and Montana, further supports the extent of fisher distribution in the late 1800s, and supports a close ecological connection between north-central Idaho and west-central Montana (Vinkey
et al.
2006, p. 269; Schwartz 2007, pp. 923-924).

Wyoming and Utah

The first reported fisher capture in Wyoming is often cited as occurring in the 1920s from the Beartooth Plateau east of Yellowstone National Park near the Montana State line (Thomas 1954, p. 28; Hagmeier 1956, p. 163). The pelt of a poached fisher was confiscated in Yellowstone National Park in the 1890s, but it is not clear where the animal was captured originally (Skinner 1927, p. 194; Buskirk 1999, p. 169). Fishers have been seldom described in Wyoming (Buskirk 1999, p. 169), and by the 1950s fishers were considered “extinct or nearly so” in the Yellowstone area (Thomas 1954, p. 3; Hagmeier 1956, p. 163). As early as the 1920s the fisher was considered rare or absent from Yellowstone National Park (Skinner 1927, p. 180). The inclusion of Utah in the historical range of the fisher was based solely on photographs of tracks taken in 1938 (Hagmeier 1956, p. 161).

Location of Restocking Efforts in the U.S. Northern Rocky Mountains

By 1930, fishers were thought to be extirpated from the USNRMs in Montana and Idaho as they were in other parts of the United States (Williams 1963, p. 9; Newby and McDougal 1964, p. 487; Weckworth and Wright 1968, p. 977). Montana Department of Fish and Game (now Montana Fish, Wildlife and Parks (MTFWP)) initiated a restocking program for fisher in 1959 with 36 individuals from central British Columbia transplanted to the Purcell, Swan, and Pintler Ranges in northwestern and west-central Montana (Weckworth and Wright 1968, p. 979). Idaho Fish and Game (IDFG) followed with a reintroduction program for fishers in 1962. Forty-two fishers from central British Columbia were transplanted to areas considered to have been formerly occupied before presumed extirpation in north-central Idaho, including the Bitterroot divide area (Williams 1963, p. 9; reviewed by Vinkey 2003, p. 55). Minnesota and Wisconsin were the sources for 110 fishers transplanted to the Cabinet Mountains of northwest Montana between 1989 and 1991 (Roy 1991, p. 18; Heinemeyer 1993, p. ii). After an absence of authenticated records for over 20 years in the USNRMs, areas near release sites yielded fisher captures in Montana in the years following the first reintroduction efforts in 1959 (Newby and McDougal 1964, p. 487; Weckworth and Wright 1968, p. 979). No post-release studies were conducted in Idaho until the mid-1980s, but marten trappers in the State reported inadvertent captures of fishers by the late 1970s (Jones 1991, p. 1).

Contemporary Distribution in the U.S. Northern Rocky Mountains

The use of unreliable records to support distribution and population extent has led to overestimation of other species' ranges (Aubry and Lewis 2003, p. 86; McKelvey
et al.
2008, p. 550). Mindful of that, we have used the most reliable and verified data in this analysis of the fisher in the USNRMs. We base the contemporary (1960 to present) record of fisher distribution in the USNRMs on verifiable or documented records of physical evidence such as legal harvest or incidentally captured specimens, animals captured for scientific study, genetic analysis of biological samples, and photographs identified by a knowledgeable expert. Eyewitness accounts of a fisher itself, or its sign, by the general public or untrained observer also may be found in agency databases (IOSC 2010, p. 5-6); however, a correct identification of fisher or its sign can be difficult by an untrained observer and these unverified records or anecdotal reports should be viewed cautiously (Aubry and Lewis 2003, p. 81; Vinkey 2003, p. 59; McKelvey
et al.
2008, p. 551). Other animals that are similar in appearance and share similar habitats, such as the American marten, mink (
Mustela vison
), or domestic cat (
Felis catus
), may be mistaken for fishers (Aubry and Lewis 2003, p. 82; Lofroth
et al.
2010, p.11; Kays 2011, p. 1). Animal signs, such as tracks, can be significantly altered by environmental conditions, and fisher tracks can be confused with those of the more common American marten (Vinkey 2003, p. 59; Giddings 2010, pers. comm.).

Montana and Idaho

A legal trapping season for fisher was reopened in Montana in 1983 after a series of fisher transplantations and evidence that fishers were reproducing in the State (Weckwerth and Wright 1968, entire; MTFWP 2010, p. 3). The majority of verified fisher records in the State through 2009 result from the harvest program (Vinkey 2003, p. 51; MTFWP 2010, p. 2, Attachment 3). In addition, Montana agency files include 48 incidental harvest records between 1968 and 1979 (Vinkey 2003, p. 51). Prior to 2002, Idaho records included verified fisher presence by targeted live-trapped and incidental captures, or otherwise-obtained physical specimens, photographs, and individuals observed directly by qualified experts (IOSC 2010, p. 7). From 2004 to the present, multiple State and Federal agencies in Montana and Idaho have partnered to collect biological data and samples by live-trapping and hair-snares for genetic testing (Albrecht and Heusser 2010, p. 23; Albrecht 2010, unpublished data; IOSC 2010, pp. 4-6; MTFWP 2010, p. 2); many surveys are conducted using a standardized protocol specific to fisher (Schwartz
et al.
2007, entire). Fisher detections (species identification) and genetic analyses to identify individual fishers have been provided to us as they become available (Albrecht 2010, unpublished data); the results of some targeted fisher surveys are pending (IOSC 2010, p. 10). Harvest specimens and targeted studies provide confident identification of fishers, but may not represent the full extent of fisher

distribution due to biases of trapper effort, site accessibility, nonrandom site selection to increase the efficacy of detection, or a lack of either survey or trapping exposure (Vinkey 2003, p. 59; Schwartz
et al.
2007, p. 6; Albrecht and Heusser 2009, p. 19).

In western Montana from 1968 to the late 1980s, fishers were known to occur in the Bitterroot Mountains bordering north-central Idaho, and west of the Continental Divide in the Whitefish Range, Flathead, and Swan Mountain Ranges (Vinkey 2003, p. 53). Trapping or targeted sampling has not been robust in these areas west of the Continental Divide since the early 1990s, but there are verified fisher detections over the past two decades (Vinkey 2003, p. 53; MTFWP 2010, Attachment 2) (Figure 2). Fisher presence has been consistent in the Bitterroot Mountains to the present, and in the Cabinet Mountains in northwest Montana since the late 1980s introduction (Vinkey 2003, p. 53; MTFWP 2010, Attachment 2).

Fishers in Idaho are found in the Selkirk Mountains in the north, the Clearwater and Salmon River Mountains in central Idaho, and the Bitterroot Range, including the Selway-Bitterroot Wilderness, in the north-central portion of the State.

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Wyoming and Utah

The contemporary distribution of fisher in Wyoming is unknown. Rare reports of fisher tracks and harvested specimens are available up until the 1950s (Thomas 1954, p. 31; Hagemeier 1956, p. 163; Buskirk 1999, p. 169). A photograph of an animal near Yellowstone National Park described as a fisher was featured in a popular publication in 1995 (Gehman, p. 2), but to date there has been no professional or expert verification that the photographed animal is indeed a fisher. Carnivore detection surveys were conducted in the Gallatin National Forest in the northern Greater Yellowstone Ecosystem between 1997 and 2000, using camera stations, hair-snares, and snow track transects; the surveyors reported fisher tracks in snow in the Gallatin and Madison Ranges of southern Montana (Gehman and Robinson 2000, p. 7). These records are considered unverified, because the use of sighting and track measurements alone are dependent on the observer's level of skill, snow and weather conditions, and “notoriously unreliable” (Vinkey 2003, p. 59).

The Wyoming Fish and Game Department (2010, p. IV-2-26) and Gibilisco (1994, pp. 63-64) report only two verified records, both prior to 1970, in or near Yellowstone National Park. One specimen was described from Ucross, Wyoming, in 1965 (Hall 1981, p. 985) over 217 km (135 mi) east of the Beartooth Plateau and Yellowstone National Park, but most of that distance is open grassland or sagebrush, which is unsuitable for fisher. Proulx
et al.
(2004, p. 59) could not confirm the presence of fisher in Wyoming in their status review of
Martes
distribution. Schwartz
et al.
(2007, p. 1) acknowledge that Wyoming may contain fisher, but there is no evidence to confirm that presence. Recently, fishers are described as “accidental” or “rare” in Wyoming with assumed breeding or records of breeding in the northwest part of the State (Orabona
et al.
2009, p. 152; Wyoming Fish and Game Department 2010, p. IV-2-26). However, the statement of fisher breeding in Wyoming is unsubstantiated and apparently made in error, (Oakleaf 2010, pers. comm.). The fisher is considered extirpated in Utah (Biotics Database 2005, pp. 1-2).

Summary of Contemporary Distribution of Fisher in the U.S. Northern Rocky Mountains

Based on the available verified specimen data, contemporary fisher distribution in western Montana and Idaho (Figure 2) covers an area similar to that depicted in the historical distribution synthesized by Gibilisco in 1994 (p. 64) (Figure 1). The contemporary distribution of fishers includes forested areas of western Montana and north-central to northern Idaho, and the boundary is further described in the “Distinct Vertebrate Population Segment” section of the finding. Based on a lack of verified records or documentation, we cannot conclude that the fisher is present, or if a breeding population was ever present, in Wyoming, including the Greater Yellowstone Ecosystem, which includes parts of south-central Montana, northwest Wyoming, and south-east Idaho.

Distribution Based on Genetic Characteristics

Recent genetic analyses revealed the presence of a remnant native population of fishers in the USNRMs that escaped the extirpation presumed to have occurred early in the 20th century (Vinkey
et al.
2006 p. 269; Schwartz 2007, p. 924). Fishers in the USNRMs today reflect a genetic legacy of this remnant native population, with unique genetic identity found nowhere else in the range of the fisher and genetic contributions from fishers introduced from British Columbia and the Midwest United States. We discuss the genetic differences due to this the native legacy and its significance to the fisher taxon in the “Significance” section of the DPS analysis later in this document.

Individuals with native genes are concentrated in the Bitterroot Mountains of west-central Montana and north-central Idaho, the St. Joe and Clearwater Regions, and the Lochsa River corridor in Idaho (Vinkey 2003, p. 76; Vinkey
et al.
2006, p. 267; Albrecht 2010, unpublished data). Individuals in these areas appear to form one population based on the frequency of gene types (Schwartz 2007, p. 924). The unique genetic type also has been identified in the only two existing USNRMs fisher specimens from the 1890s (Schwartz 2007, p. 922). The presence of this unique variation would indicate that fishers in the USNRMs were isolated from populations outside the region by distance, small population number, or both, for some time before the influences that led to the presumed extirpation in the early 20th century (Vinkey 2003, p. 82). Today, a genetic identity more commonly found in British Columbia populations also is present in the Bitterroot Divide area, and fishers in this region are likely a mix of native and individuals translocated from British Columbia (Vinkey 2003, p. 76; Vinkey
et al.
2006, p. 268; Schwartz 2007, p. 924).

Fishers in northwestern Montana and extreme northern Idaho represent the geographically distant source populations from Minnesota and Wisconsin that were introduced into the Cabinet Mountains of Montana in the late 1980s (Drew
et al.
2003, p. 59; Vinkey
et al.
2006, pp. 268-269; Albrecht 2010, unpublished data). British Columbia types also are found in this region, reflecting offspring of a 1959 introduction from Canada, a remnant native population, or possibly natural immigration from Canada (Vinkey
et al.
2006, p. 270; Schwartz 2007, p. 924).

An assessment of the degree of hybridization between native and introduced individuals is difficult based on the assessment techniques. Analysis of genetic identity is conducted on mitochondrial DNA, which only reflects the genetic contribution of the mother (Forbes and Alledorf 1991, p. 1346; Vinkey 2003, p. 82). Males could make a greater contribution to distant populations based on their larger home range sizes and expanded wanderings during the breeding period (Arthur 1989a, p. 677; Jones 1991, pp. 7-78), but based on mitochondrial DNA analysis alone, this contribution would not be detected.

Population Status

Estimates of fisher abundance and vital rates are difficult to obtain and often based on harvest records, trapper questionnaires, and tracking information (Douglas and Strickland 1987, p. 522), and recent information is limited. Habitat modeling and behavioral or other natural history characteristics (
e.g.,
home range sizes) also are used to estimate population sizes over a geographic area (Lofroth 2004, pp. 19-20; Lofroth
et al.
2010, p. 50). Fisher densities over areas of suitable habitat have been reported, but there are no total or comprehensive population sizes for the fisher in the eastern United States or Canada. In the western range, fisher populations have been estimated using habitat models and home range sizes. Late winter populations in British Columbia range from 1,403 to 3,715 individuals (Lofroth 2004, p. 20). In the Southern Sierra Nevada Mountains, the fisher population is estimated between 160 to 598 individuals depending on the methods used, and an estimated 4,616 fishers inhabit the Southwest Oregon/Northern California area (reviewed by Lofroth
et al.
2010, p. 50).

As previously noted, fishers in the USNRMs have increased in number and distribution since their perceived

extirpation in the 1920s. However, little is known of the population numbers, trends, or vital rates of fishers in the USNRMs today. Preliminary work is ongoing to determine the geographic range of the species, identify populations with native and introduced genes, and determine the abundance of individuals in populations using DNA analyses (Schwartz
et al.
2007, pp. 1-2). An evaluation of the translocation effort in the Cabinet Mountains of northwest Montana between 2001 and 2003 yielded only 4 live-trapped individuals and 28 track detections over 25 survey weeks, indicating that the population there is likely small and limited in distribution (Vinkey 2003, p. 33) (Figure 2). Based on genetic similarities, fishers in the Selkirk Mountains of northern Idaho, just south of the Canadian border, are likely associated with the fishers from Minnesota and Wisconsin introduced to Montana's Cabinet Mountains to the east (Cushman
et al.
2008, p. 180). Efforts to detect fisher in the Selkirk Mountains between 2003 and 2005 using hair-snares for genetic analysis produced 26 samples identified as fisher, although the number of unique individuals is likely much smaller than the number of samples (Cushman
et al.
2008, p. 180).

A review of historical records and carnivore research in Montana indicates that the fisher is one of the lowest-density carnivores in the State (Vinkey 2003, p. 61). What is known of fisher populations today in Montana is primarily derived from harvest data and winter furbearer track surveys (MTFWP 2010, p. 2, Attachment 8, pp. 2-3). A Montana habitat model based on 30 years of fisher presence data (the majority being harvest data) conservatively estimates that there is high habitat suitability capable of supporting 216 individuals concentrated in the Bitterroot Mountains along the Idaho border, the Swan and Flathead River drainages, and the Whitefish and Cabinet Mountains just south of the Canada border (MTFWP 2010, Attachment 8, pp. 2-3; Montana Natural Heritage Program (MTNHP) 2010a, entire; 2010b, entire).

Most of the recent USNRMs fisher survey effort has targeted the Coeur d'Alene, St. Joe, Clearwater, and Lochsa areas of northern and north-central Idaho. In 2006 and 2007, 10 individual fishers were identified in an area of approximately 8,951 km
2
(3,456 mi
2
) of potentially suitable habitat in the St. Joe and Coeur d'Alene areas, north and south of Interstate 90 in northern Idaho (Albrecht and Heusser 2009, pp. 6, 8, 15). The St. Joe and Coeur d'Alene projects were not intended to elucidate fisher presence in the entire area of potentially suitable habitat, but simply to detect the presence of fisher; therefore, traps were placed in areas highly likely to support fisher (Albrecht and Heusser 2009, p. 19). Thirty-four fisher were identified in a 1,295-km
2
(500-mi
2
) (one fisher per 38 km
2
(14.7 mi
2
)) area of the Lochsa River corridor of north-central Idaho during a targeted live-trap study between 2002 and 2004 (Schwartz 2010, unpublished data). Thirty individual fishers were captured in the Clearwater area north of the Lochsa River in north-central Idaho between 2007 and 2010 (Sauder 2010, unpublished data). Based on genetic data, it appears that individuals in these areas of north-central Idaho and fishers in west-central Montana represent a single population (Schwartz 2007, p. 924) (Figure 2). We have no additional information on the Lochsa River or Clearwater surveys to determine if these reports are indicative of comprehensive population numbers. No habitat suitability or capacity model is available for Idaho.

Evaluation of Listable Entities

Under section 3(16) of the Act, we may consider for listing any species, including subspecies, of fish, wildlife, or plants, or any DPS of vertebrate fish or wildlife that interbreeds when mature (16 U.S.C. 1532(16)). Such entities are considered eligible for listing under the Act (and, therefore, are referred to as listable entities), should we determine that they meet the definition of an endangered or threatened species. In this case, the petitioners have requested that the fisher in the USNRMs be considered as a DPS of a full species for listing as endangered or threatened under the Act. We concluded in our 90-day finding on the petition that there is support for a DPS of fisher in the USNRMs (75 FR 19925), and we analyze this possibility further in the following section after reviewing the best available information.

Distinct Vertebrate Population Segment

Under the Service's DPS policy (61 FR 4722, February 7, 1996), three elements are considered in the decision concerning the establishment and classification of a possible DPS. These are applied similarly for additions to, or removal from, the Federal List of Endangered and Threatened Wildlife. These elements include:

(1) The discreteness of a population in relation to the remainder of the species to which it belongs;

(2) The significance of the population segment to the species to which it belongs; and

(3) The population segment's conservation status in relation to the Act's standards for listing, delisting, or reclassification (
i.e.,
is the population segment endangered or threatened).

In evaluating the distribution of fisher and the geographic extent of a possible DPS in the USNRMs, we examined information cited in the petition (Defenders
et al.
2009, pp. 11-24), published range maps, published works that included historical occurrences, unpublished studies related to fisher distribution, and other data submitted to us subsequent to the request for information published in the 90-day finding for fisher (75 FR 19925). Fisher distribution in the USNRMs and extended area was discussed in detail in the preceding “Distribution” section.

Discreteness

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

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

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

Western Montana and north-central to northern Idaho broadly encompass the area under consideration for a fisher DPS in the USNRMs. The population area includes the contemporary (1960s reintroductions to present) distribution of fisher in the USNRMs and is best circumscribed by geological features and the distribution of habitat known to support fisher. The distribution of fishers in the USNRMs is bounded by the southern Bitterroot Range north of Lemhi Pass in Montana, east and then north along the Continental Divide including forested areas east of the Divide to the Rocky Mountain Front, north along the eastern boundary of Glacier National Park, west along the Boundary Mountains and northern Whitefish Range in northern Montana, west to the southern Selkirk and southern Purcell Mountains to the Idaho boundary with Washington, south along the forested areas of northern Idaho bounded on the west by the Palouse and Camas Prairie regions, south along the Western Mountains and North Payette River to the Boise Mountains, northeast along the Salmon River to the southern

Bitterroot Range north of Lemhi Pass in Idaho (Figure 2). The northern geographic extent of the fisher distribution roughly coincides with the border of the United States and Canada at 49 degrees north latitude. The fisher distribution in the USNRMs is the southern extent of the taxon's known range in the Rocky Mountains.

Fishers in the USNRMs are physically or geographically separate from other fisher populations. The range of the fisher in the West Coast Range of Washington, Oregon, and California is separated from the USNRMs by distance, natural physical barriers, including the nonforested high desert areas of the Great Basin in Nevada and eastern Oregon and the Okanogan Valley in eastern Washington, major highways, urban and rural open-canopied areas, and agricultural development (69 FR 18770; Lofroth
et al.
2010, p. 47). Occupied areas in the USNRMs are 150 to 200 km (93 to 124 mi) from the closest edge of the West Coast fisher DPS abutting the unoccupied Okanogan Valley of Washington (69 FR 18770, Lofroth
et al.
2010, p. 33). Occupied areas in the USNRMs are approximately 418 km (300 mi) from the closest occupied area of the West Coast DPS in the southern Cascade Mountains of southwest Oregon or the Olympic Peninsula in Washington (National Park Service (NPS) 2009, entire; Lofroth
et al.
2010, p. 47). There is no evidence to indicate that fisher in the USNRMs were recently, or historically, connected to other fisher population centers in the United States (Gibilisco 1994, p. 64; Proulx
et al.
2004, p. 57). Maps of historical and recent fisher distributions show no connection in the contiguous United States between occurrences in the USNRMs and the fisher populations in the Midwest and Great Lakes area, which occur approximately 1,126 km (700 mi) away, across mostly nonforested areas of unsuitable habitat (Hagmeier 1956, p. 151; Douglas and Strickland 1987, p. 313; Gibilisco 1994, p. 64; Proulx
et al.
2004, p. 57).

There is no indication that a population of fisher exists in a large geographic area of southern Alberta or southern British Columbia in Canada to the north of the USNRMs (see “Distribution” section). Individual fishers have been identified near the international boundary and observed using areas in both Canada and the USNRMs (Fontana
et al.
1999, p. 19; Albrecht 2010, unpublished data; Giddings, 2010 pers. comm.). We believe that the detections in extreme southern Canada represent wandering individuals, or individuals in the USNRMs whose home ranges include suitable habitat patches coincidental to the border, because the closest concentration of fishers in Canada is over 200 km (125 mi) north of the USNRMs through patchy habitat of low suitability (Weir 2003, p. 14; Weir and Lara Almuedo 2010, p. 36). The lack of suitable habitat in southeastern British Columbia likely contributed to the failure to reestablish a fisher population there in the early 1990s (Fontana
et al.
1999, p. 1; Weir
et al.
2003, pp. 24-25).

We have no direct confirmation that fishers are moving between the USNRMs and larger population centers in Canada; however, it is likely there is some interaction between transient individuals from the larger population areas. Reports of transient or juvenile fishers moving linear distances up to 135 km (84 mi) are known from other parts of the fisher's range (Weir and Corbould 2008, p. 48), although shorter distances of up to 107 km (66 mi) are more common (York 1996, p. 55). It is unlikely that transient individuals provide a functional connection between Canada population centers and the USNRMs. Individuals traveling longer distances are subject to a greater risk of mortality, and very few establish the stability of a home range (Weir and Corbould 2008, p. 44) required for successful long-term recruitment. Because the intervening areas appear unable to support resident fishers, and we believe that the only fishers using these areas are transient individuals attempting to move between population centers, we have concluded that the USNRMs fisher population is markedly separate from those to the north.

Summary for Discreteness

We conclude that the fisher in the USNRMs is markedly separated from other populations of the same taxon as a result of physical factors, and thus meets the definition of a discrete population according to the Service's DPS policy. Because the entity meets the first criterion for discreteness (marked physical separation), an evaluation with respect to the second criterion (international boundaries) is not needed.

Significance

If a population segment is considered discrete under one or more of the conditions described in the Service's DPS policy, its biological and ecological significance will be considered in light of Congressional guidance that the authority to list DPSs be used “sparingly” (see Senate Report 151, 96th Congress, 1st Session) while encouraging the conservation of genetic diversity. In making this determination, we consider available scientific evidence of the discrete population segment's importance to the taxon to which it belongs. Since precise circumstances are likely to vary considerably from case to case, the DPS policy does not describe all the classes of information that might be used in determining the biological and ecological importance of a discrete population. However, the DPS policy describes four possible classes of information that provide evidence of a population segment's biological and ecological importance to the taxon to which it belongs. As specified in the DPS policy (61 FR 4722), this consideration of the population segment's significance may include, but is not limited to, the following:

(1) Persistence of the discrete population segment in an ecological setting unusual or unique to the taxon;

(2) Evidence that loss of the discrete population segment would result in a significant gap in the range of a taxon;

(3) Evidence that the discrete population segment represents the only surviving natural occurrence of a taxon that may be more abundant elsewhere as an introduced population outside its historical range; or

(4) Evidence that the discrete population segment differs markedly from other populations of the species in its genetic characteristics.

A population segment needs to satisfy only one of these conditions to be considered significant. Furthermore, other information may be used as appropriate to provide evidence for significance. Below we address conditions 1, 2, and 4. Condition 3 does not apply to fishers in the USNRMs because North American fishers are distributed widely within their historical range in Canada and the eastern United States.

Unusual or Unique Ecological Setting

The fisher is a forest-dependent species, and marked separation from fishers in other geographic locations may be indicated by variations in forest types or ecological conditions influencing forest characteristics. Fishers in the western portion of the range (West Coast, western Canada, and the USNRMs) generally inhabit landscapes dominated by conifer forests, whereas fishers live in more dense, lowland forests with higher proportions of deciduous trees in the Northeast and upper Midwest United States and Canada (Allen 1983, pp. 2-3; Arthur
et al.
1989b, p. 687; Powell 1993, p. 89; Buskirk and Powell 1994, p. 285; Jones and Garton 1994 p. 377;

Ricketts
et al.
1999, pp. 156, 160, 170). Fishers of the West Coast population (Washington, Oregon, and California) inhabit forest environments unusual in comparison to the rest of the taxon, and are unique from other parts of the range based on the unusual forest environment (69 FR 18777). Not only are the forests of the West Coast fishers lacking the broadleaf forest component common in the eastern range, but the coastal climate of wet winters and cool, dry summers produces distinctive forests of sclerophyllic (leathery-leafed) evergreen trees and shrubs found nowhere else in the range (Smith
et al.
2001 pp. 17-18; 69 FR 18777).

In addition to differences of forest type between the USNRMs and eastern North America and the U.S. West Coast, fishers in the USNRMs occupy forest areas that differ due to influences of climate and precipitation patterns from fisher population areas in western Canada. Forested areas of western Montana and central-to-northern Idaho are temperate, coniferous forests influenced by dramatic elevation gradients that produce several types of vegetation zones (Ricketts
et al.
1999, pp. 213-214, 250-251; Bailey 2009, p. 89, plate 1). Topographic relief produces localized climate effects which add to the vegetation variability within this region (Ricketts
et al.
1999, pp. 213-214). Locally variable in predominant tree species or assemblages of species, this temperate zone encompasses the USNRMs extending north along the Continental Divide into southwestern Alberta and southeast British Columbia (Ricketts
et al.
1999, pp. 213-214).

The northern areas of the USNRMs are heavily influenced by maritime moisture patterns, and in addition to the predominating
Pseudotsuga monziesii,
Pacific tree species such as
Thuja plicata
(western red cedar),
Tsuga heterophylla
(western hemlock) and
Abies grandis
are present (McGrath
et al.
2002, entire; U.S. Forest Service (USFS) 2009, p. 1). Severe winters with heavy snowfall are usual and summers are usually dry; precipitation is highly variable within the zone averaging between 510 to 1,020 mm (20 to 40 in.) per year primarily falling as snow in fall, winter, and spring (USFS 2009, p. 1). In the southern part of the USNRMs, maritime conditions decrease along latitudinal and altitudinal clines in the mountains of central Idaho and the Bitterroot Range in west-central and southwest Montana (McGrath
et al.
2002, entire).
A. grandis,

P. monziesii,
and western spruce/fir forests,
Larix
spp. (larch),
Pinus ponderosa
and
Pinus contorta
(lodgepole pine) characterize the mountain forests of the Idaho Batholith (Ricketts
et al.
1999, p. 250; McGrath
et al.
2002, entire). Hardwood trees, selected for fisher denning in other parts of the range, are not significant parts of the landscape in the USNRMs (reviewed by Powell 1993, pp. 55-56; Heinemeyer and Jones 1994, p. iii; reviewed by Lofroth
et al.
2010, pp. 101, 108-109). The absence of hardwoods may be a limiting factor to fishers in the region (Heinemeyer and Jones 1994, p. iii), or an indication of successful adaptation to resources not used elsewhere. Both of these points are speculative as there is little information available describing natal den selection or successful reproduction in the USNRMs.

Fishers in British Columbia and Alberta are associated most commonly with the Sub-boreal Spruce and Boreal White and Black Spruce Biogeoclimatic Zones in the central to northern areas of the provinces (Weir and Lara Almuedo 2010, p. 36; Meidinger
et al.
1991, p. 211; Delong
et al.
1991, p. 239). The Sub-boreal Spruce Zone is a heavily forested montane region with uplands dominated by
Picea engelmannii x glauca
(hybrid white spruce) and
Abies lasiocarpa;

Pinus contorta
is common on drier sites (Meidinger
et al.
1991, p. 210). The climate of the Sub-boreal Spruce Zone is continental and characterized by severe, snowy winters and relatively warm, moist, and short summers (Meidinger
et al.
1991, p. 210). Mean annual precipitation ranges from 415 to 1,650 mm (16 to 65 in.) with less than half of that falling as snow in winter (Meidinger
et al.
1991, p. 210). The Boreal White (
Picea glauca
) and Black (
Picea mariana
) Spruce Zone is a relatively dry zone with very long, very cold winters with short summer growing seasons, and annual precipitation averages between 330 and 570 mm (13 and 22 in.), with 35 to 55 percent falling as snow (DeLong
et al.
1991, p. 238).
P. glauca,

P. mariana,

P. contorta,
and
A. lasiocarpa
are major tree species in these zones (DeLong
et al.
1991, p. 238). Both the Sub-boreal Spruce and Boreal White and Black Spruce Zones have a representative deciduous tree component of
Populus

tremuloides
(trembling aspen),
Betula papyrifera
(paper birch), and
Populus balsamifera
spp.
Trichocarpa
(black cottonwood) (DeLong
et al.
1991, p. 238; Meidinger
et al.
1991, p. 212; Weir and Corbould 2008, p. 5), all of which are tree hardwood types selected by fisher for reproductive dens (Weir and Lara Almuedo 2010, p. 37).

Topographic relief in the USNRMs produces localized variations in vegetation and seasonal snowfall not widely seen in the western Canada population. It is hypothesized that fisher distribution on the landscape is limited by deep snow (Krohn
et al.
1995, p. 103; Krohn
et al.
1997, p. 226). If this is correct, then the precipitation in the USNRMs, the majority of which falls as snow and is heavily influenced by topography, could lead to geographic partitioning and an overall less optimal habitat within the region. There are observations of fishers using areas with deep, fluffy snow in the USNRMs, which also could indicate an adaptation to local conditions, but the relationship between using or avoiding certain snow conditions has not been evaluated statistically. Fishers in Idaho have some of the largest home ranges recorded for the species (reviewed by Powell and Zielinski 1994, p. 58; IOSC 2010, p. 4; reviewed by Lofroth
et al.
2010, p. 68), possibly indicating suboptimal forest resources often found in peripheral populations (Wolf
et al.
1996, p. 1147). The limited availability of hardwood tree types used for denning in other areas of the range also may indicate a local adaptation to different den structures in the USNRMs and the selection of less optimal structures based on necessity.

More information is needed to elucidate important ecological relationships for fishers in the USNRMs. Therefore, we do not conclude that the fisher in the USNRMs is significant to the taxon as a whole based on ecological differences alone, but the observed differences indicate that fishers in the region are subject to suboptimal habitats and pressures typically seen in important peripheral populations. Strong selective pressures in peripheral populations may induce adaptations that may be important to the taxon in the future.

Significant Gap in the Range of the Taxon

The loss of the fisher in the USNRMs would result in a significant gap in the range of the taxon and contribute to the extensive range retraction and fragmentation that has occurred since European settlement of North America (Gibilisico 1994, p. 60). The USNRMs represent one of only three historical peninsular reaches of the range in the United States connecting with Canada and the southernmost extension of the taxon's distribution in the Rocky Mountains (Gibilisco 1994, p. 60; Proulx
et al.
2004, p. 57). Range retraction in the eastern United States south of the Great Lakes has isolated populations in New England and northern Atlantic States from Minnesota and Wisconsin, although the eastern United States populations retain connectivity to

Canada (Gibilisico 1994, p. 60; Proulx
et al.
2004, p. 57).

Fisher populations in the western United States are isolated from each other and the closest Eastern population in the Great Lakes area, and have lost a connection or have a severely diminished capacity to connect with larger population areas in Canada (Gibilisco 1994, p. 64; Zielinski
et al.
1995, p. 107; Aubry and Lewis 2003, pp. 86, 88; Weir 2003, pp. 19, 24, 25; Weir and Lara Almuedo 2010, p. 36). Extirpation of the USNRMs population would significantly impact representation of the species by shifting the southern boundary of the western range of the taxon over 965 km (600 mi) to the north. Only three individually isolated fisher populations in Oregon and California, two being native populations (Aubry and Lewis 2003, p. 88; Lofroth
et al.
2010, p. 47), would be left in the entire southwest range of the taxon at a distance of over 800 km (500 mi) from populations in Canada (Weir and Almuedo 2010, p. 36). The recent fisher introduction to Washington's Olympic peninsula is not considered here because its establishment as a self-sustaining entity has not been demonstrated.

The retention of a fisher population in the USNRMs is significant to the taxon because of its situation at the periphery of the range. Populations at geographic margins, defined as peripheral populations, may be of high conservation significance and important to long-term survival and evolution of species (Lesica and Allendorf 1995, p. 756; Fraser 2000, p. 49). Populations at the periphery tend not to be given conservation priority because of their existence in lower quality habitats, and these populations are presumed to be least likely to survive a reduction in range (Wolf
et al.
1996, p. 1147). This presumption is based on an existing theory that the cause of a species' range contraction is erosion that commences at the periphery where population numbers are low and progresses to the center where optimal habitats support higher population numbers (Lomolino and Channell 1995, pp. 336, 338). Upon closer examination, population persistence is not biased toward larger, less isolated or more central regions of a species historical range. Of 245 vertebrate species experiencing geographic range contraction, 98 percent retained some species presence in peripheral populations, 68 percent retained greater periphery than core, and 37 percent of species retained no core but remained in peripheral populations (Channell and Lomolino 2000, p. 85). Peripheral populations are likely to be in suboptimal habitats and subject to severe pressures that result in genetic divergence, as seen in USNRMs fisher populations, either from genetic drift or adaptation to local environments (Fraser 2000, p. 50). Because of their exposure to strong selective pressures, peripheral populations may contain adaptations that may be important to the taxon in the future. Lomolino and Channell (1998, p. 482) hypothesize that because peripheral populations should be adapted to a greater variety of environmental conditions, then they may be better suited to deal with anthropogenic (human-caused) disturbances than populations in the central part of a species' range.

We conclude that the loss of the USNRMs fisher population would result in a significant gap in the range of the taxon by shifting the southern boundary of the western range over 965 km (600 mi) to the north, leaving only three individually isolated populations in the entire southwestern range of the taxon. Thus, the USNRMs population meets the definition of significant in our DPS policy.

Marked Genetic Differences

Fishers in the USNRMs represent a native lineage that escaped extirpation early in the 20th century (Weckwerth and Wright 1968, p. 977; Schwartz 2007, p. 924). Close to half of the USNRMs fishers sampled have a unique mitochondrial haplotype [a group of alleles (DNA sequences) of different genes on a single chromosome that are closely enough linked to be inherited usually as a unit]—Haplotype 12—found nowhere else in the range of the taxon (Drew
et al.
2003, p. 57; Vinkey 2003, p. 82; Vinkey
et al.
2006, p. 269). Mitochondrial DNA is associated with the energy-producing structures within cells called mitochondria, and is inherited through the maternal line. Individuals with Haplotype 12 are significantly divergent from all other haplotypes in having an additional variation (Haplotype B) within a genetic structure associated with the mitochondria called Cytochrome b, while all of the other 11 mitochondrial haplotypes have the Haplotype A of the Cytochrome b region (Vinkey 2003, p. 79; Vinkey
et al.
2006, p. 268; Schwartz 2007, p. 923). Unique genetic haplotypes common to the native lineage are expected, considering the peripheral location of the population and a history of severe population reduction and isolation (Lesica and Allendorf 1995, p. 754, Vinkey 2003, p. 82). Locally adapted populations evolve traits that provide an advantage and higher level of fitness under the local environmental conditions or habitat than genotypes evolved elsewhere (Kawecki and Ebert, 2004, p. 1225), and the unique genetic characteristics may have factored into sustaining a rare population in the USNRMs. The forces that shape adaptation are often strongest in the periphery of the range, and populations situated here may be better suited to deal and adapt to changes in their environments (Lomolino and Channell 1998, p. 482). It is the intent of the DPS policy and the Act to preserve important elements of biological and genetic diversity. The loss of the native fisher lineage in the USNRMs would result in the loss of a unique and irreplaceable genetic identity and the local adaptation and evolutionary potential that goes with it. Thus, we conclude that the USNRMs fisher differs markedly from other members of the taxon in genetic characteristics, and this difference is significant to the conservation of the species.

Summary for Significance

We conclude that the fisher population in the USNRMs is significant because its loss would result in a significant gap in the range of the taxon, and its genetic characteristics differ markedly from those of other fisher populations.

Determination of Distinct Population Segment

Based on the best scientific and commercial information available, we find that the fisher in the USNRMs is both discrete and significant to the taxon to which it belongs. Fishers in the USNRMs are markedly separated from other populations of the same taxon as a result of physical factors, further supported by quantitative differences in genetic identity. The loss of the fisher in the USNRMs would result in a significant gap in the range of the taxon and the loss of markedly different genetic characteristics relative to the rest of the taxon. Because the fisher in the USNRMs is both discrete and significant, it qualifies as a DPS under the Act.

Distinct Population Segment Five-Factor Analysis

Since the fisher in the USNRMs qualifies as a DPS, we will now evaluate its status with regard to its potential for listing as endangered or threatened under the five factors enumerated in section 4(a) of the Act.

Section 4 of the Act (16 U.S.C. 1533) and implementing regulations (50 CFR part 424) set forth procedures for adding species to, removing species from, or

reclassifying species on the Federal Lists of Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of the Act, a species may be determined to be endangered or threatened based on any of the following five factors:

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

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

(C) Disease or predation;

(D) The inadequacy of existing regulatory mechanisms; or

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

In making this finding, information pertaining to the USNRMs fisher DPS in relation to the five factors provided in section 4(a)(1) of the Act is discussed below. In making our 12-month finding on the petition we considered and evaluated the best available scientific and commercial information.

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

We are required by the Act to assess threats information that may occur within the foreseeable future. We define foreseeable future as a timeframe in which impacts can be reasonably expected to occur. Where future projections are not available, it is assumed that current trends will continue unless information exists to the contrary. Our evaluation of the fisher in the USNRMs follows.

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

Under Factor A, we will discuss a variety of impacts to fisher habitat including: (1) Timber Harvest and Forest Management, (2) Development and Roads, (3) Climate Change, and (4) Fire and Disease. Climate change is discussed under Factor A, because the primary impact of climate change on fishers is expected to be through changes to the availability and distribution of fisher habitat. Many of these impact categories overlap or act together to affect fisher habitat.

Timber Harvest and Forest Management

Industrial timber harvest in the inland Northwest United States (Interior Columbia River Basin), including Idaho and western Montana, did not occur until the early 20th century (Hessburg and Agee 2003, pp. 40-41). Prior to 1900, logging in Idaho and Montana supplied timbers only to local concerns such as mining and railroad development, and did not become important to national markets until after other forested areas (
e.g.,
Great Lakes region) had been depleted (Hessburg and Agee 2003, p. 40). Early industrial logging used selective practices, taking only large, high-grade or salvage logs (Hessburg and Agee 2003, pp. 41-42). By 1940, many inland northwest areas containing dry forest types, typically of ponderosa pine, were intensively logged by this method; moist or mesic forest types favored by fishers in the Flathead Valley and Whitefish Mountains in Montana and the Coeur d'Alene area of northern Idaho were also affected (Lesica 1996, p. 34; Hessburg and Agee 2003, pp. 41-42). The balance of forested areas in Idaho and Montana showed little or no logging activity up to 1940 (Hessburg and Agee 2003, p. 42).

Historical fisher population numbers are not known, but reports of their presence declined in the 1920s to a point that the fisher was presumed extirpated in the USNRMs (Williams 1963, p. 8; Weckwerth and Wright 1968, p. 977; Brander and Books 1973, p. 52). Fishers in the USNRMs avoid dry forest types (Schwartz 2010, unpublished data), and because local subsistence logging and early industrial logging were of limited geographic scale and selected for dry forest types, it is unlikely that this contributed directly to the fishers' apparent demise across the USNRMs area. Other factors or combination of factors, discussed in subsequent sections, may have had more influence on past fisher population reductions.

From the 1930s, timber harvest continued (Hessburg and Agee 2003, p. 41) while native fishers maintained an undetected refugium likely, in the Selway-Bitterroot Mountains straddling the border of Montana and Idaho (Vinkey
et al.
2006, p. 269). Timber harvest was increasing in the USNRMs as fisher reintroductions (later realized to be population augmentations) were occurring in the late 1950s and early 1960s. Clearcutting practices, which removed all overhead cover in the harvest area, increased on private and public lands, and large areas of private timberland were converted to plantation forestry which emphasized clearcutting and even-aged forest regeneration management practices (Hessburg and Agee 2003, p. 41). With plantation or rotational forestry, the large tree components and coarse woody debris are suppressed or not allowed to accumulate to the point that they supply denning or cold weather resting sites (Weir 2003, p. 16). From 1938 to present day, low-elevation timberlands have been depleted of large, older trees considered late-seral or old-growth type, and the mid-elevation habitats retain only small amounts (DellaSala
et al.
1996, p. 213; Lesica 1996, p. 37). The majority of presettlement upland old-growth forest was in the drier forest types of ponderosa pine/Douglas fir/western larch, which are subject to frequent low-intensity underburns that reduce ladder fuels (forest fire fuels that provide fire connectivity from understory to midlevel or canopy fuels) and more shade-tolerant vegetation in the understory (Green
et al.
1992, p. 2). However, fishers are known to avoid these forest types and they represent only minor components of areas used by fishers (Jones and Garton 1994, pp. 377-378; Schwartz 2010, unpublished data).

In general, timber harvest and management over the last century has resulted in the loss of old forest and large- and medium-diameter trees that historically were widely distributed in forest structures other than old growth forest (Hessburg and Agee 2003, p. 45); still, the amount of land covered by forest in the USNRMs is similar to historical times (Hessburg
et al.
2000, p. 60). Timber harvest, together with fire exclusion, has produced younger, homogenously structured forest patches, especially in dry forest types, with more canopy layers and more understory vegetation than historically due to fire suppression (Hessburg and Agee 2003, pp. 45-46). Fragmentation of managed landscapes has increased due to more numerous and smaller patches of various forest types, while roadless and wilderness areas have retained a simpler less fragmented structure (Hessburg
et al.
2000, p. 78). From a landscape perspective, the departure from historical old-growth structure is most

pronounced in the northern areas of the USNRMs, with a concurrent shift to increasing old-forest multistory stages in the southern areas (Wisdom
et al.
2001, p. 184).

As a result of timber harvest and management practices, forest structures and quantities of large trees across the USNRMs have been affected. It is unclear how this has impacted fisher populations. There is no information regarding fisher population numbers within the region before European settlement, and no region-wide population numbers or trends are available today to allow a comparison of the impacts of changes to the landscape over time on fisher populations. Fishers were so rare as to be considered extirpated before large-scale harvesting occurred. Fifty years after the introduction of 78 animals to 9 areas in Idaho and Montana between 1959 and 1962 (reviewed by Vinkey 2003, p. 55), concurrent with decades of post-introduction timber harvest, fishers, half of which are of native lineage, persist on the landscape in a wider distribution than they did before augmentations (Vinkey 2003, p. 82; IOSC 2010, pp. 7, 10; MTFWP 2010, Attachment 4). Although there is little information elucidating the density of fisher populations in the USNRMs, the contemporary distribution of fishers appears to be similar to the historically depicted distribution in Idaho and Montana (Gibilisco 1994, p. 64) (Figure 1).

We are not concluding that a cause and effect relationship exists between increased timber harvest or treatment and increasing fisher distribution. The existing state of the USNRMs landscape is conducive to supporting fisher, but it is unknown if the system has the capacity to support, in the long term, a self-sustaining population or subpopulations in a metapopulation dynamic. Fisher home ranges in Idaho and Montana are larger than most other areas in the taxon's range (reviewed by Powell and Zielinski 1994, p. 58; reviewed by Lofroth
et al.
2010, p. 68; IOSC 2010, p. 4), and this large size could be the result of fragmentation or low-quality habitat (Powell and Zielinski 1994, p. 60), either naturally occurring or human-produced. Timber harvest and management have significant potential to alter the suitability of a landscape for fishers; conversely, management of forests using mechanical means or fire can assist in creating conditions that foster larger trees, create snags, increase woody debris, or open densely stocked areas to provide habitat for fisher prey species. Fishers in the USNRMs evolved in forest types where fire frequency and intensity was mixed, and windthrow was common, resulting in a complex and intricate landscape mosaic of young, mixed-age, and late-seral components (Jones 1991, p. 111; Arno
et al.
2000, pp. 225-227). Thus, the result of silviculture treatments or harvest may resemble the natural disturbances and the succession that follows (Powell and Zielinski 1994, p. 64).

Current and Future Timber Harvest and Management

Commercial timber harvest, management for timber production, and the use of forestry techniques to protect, restore, and enhance forest ecosystems are ongoing activities in the USNRMs and are expected to continue. Fourteen national forests comprise approximately 65 percent of the land area and 72 percent of the forest types known to be used by fishers in the USNRMs (U.S. Department of Agriculture (USDA) 2009, entire). Timber harvest or manipulation for either timber production or other resource objectives is stated in each forest's Land and Resource Management Plan, which provide direction for a 10- to 15-year period. National forests are subject to a multi-use mandate and maintenance “in perpetuity of a high level of annual or regular periodic output of the various renewable resources,” including timber (PL 104-333), and other legislative mandates for forest health or fuels reduction (
e.g.,
Healthy Forests Restoration Act (Pub. L. 108-148)), which may require manipulation of forested areas. Planning directives specify lands for timber production for long-term sustained yields; however, silviculture (forest removed or treated) acres on all forests in the USNRMs has generally declined over the past 15 years, including a significant reduction in clearcutting (USDA 2010a, entire; USDA 2010b, entire). The USFS actions are regulated and relevant authorities are discussed in the “Factor D” section below.

State-owned forestry lands comprise approximately 6 percent of the forest types preferred by fishers in the USNRMs area. Timber harvest is an activity expected to continue on State trust or endowment lands in both States of Idaho and Montana, because of the responsibility to maximize long-term financial returns to public schools and other trust beneficiaries (Idaho Board of Land Commissioners 2007, p. 3; Montana Code Annotated 2009a, entire). Forest resources are evaluated for management of a sustainable harvest on 5- to 10-year review schedules (Idaho Board of Land Commissioners 2007, p. 18; Montana Department of Natural Resources and Conservation (MTDNRC) 2010, p. 3). Private lands, including commercial timber operations with the primary objective of maximizing fiber production, comprise approximately 22 percent of the fisher forest types. The extent of timber harvest operations are driven by market forces and difficult to predict (Morgan
et al.
2005, p. 2), but it is reasonable to conclude that management to maximize wood production (
e.g.,
pre-thinning of stands), harvest, road construction and maintenance, and other activities will continue into the future.

We expect the current timber management and silviculture activity to continue on national forest lands guided by management plans. The effects of present and future forest management and timber harvest on the capacity of the USNRMs to support fishers may be influenced by many factors, including the location, scale, and juxtaposition of treatments to previous disturbances; the suitability of an area to provide fisher habitat under natural conditions; and the habitat needs of fishers. The habitat ecology of fishers in the USNRMs is not well understood. Forest patches with high densities of large trees, canopy covers exceeding 40 percent, and riparian areas appear to be important; however, information is lacking regarding fishers' requirements for patch size and connectivity (Jones and Garton 1994, pp. 380, 385-386). Although some information is available from other regions, habitat requirements for successful denning and rearing of young in the USNRMs are not known. Fishers have been described as using “old-growth” forest types disproportionally to their occurrence (Thomas
et al.
1988, p. 255); however, there also has been a lack of clarity in the use of the term “old-growth” in forest ecology literature, and description of forest characteristics at any particular successional stage vary by geographic region, forest type, and local conditions (Green
et al.
1992 errata 2008, p. 2). Therefore, without specific parameters, basing a loss of fisher habitat on trends of “old-growth” or even “larger trees” may be misleading.

Late seral or mature forest elements such as snags and overhead cover are important habitat features for fishers throughout their range. These mature forest conditions may take many decades to hundreds of years to develop, and national forest management direction is revised over short time periods relative to forest succession. National forest lands that support fishers today reflect natural processes and silviculture actions

spanning numerous planning periods as well as actions taken before comprehensive national forest management was mandated in 1976 (16 U.S.C 1601-1614). Given the history of forest management and planning, we do not expect significant changes in the availability of mature forest habitats through future forest planning cycles.

The species continues to occupy its presumed historical range despite habitat alterations that have occurred within that range, although fisher densities may be different. Fishers in the USNRMs have been observed to use roadless areas of forests, national forest lands managed for multiple purposes, and State forests and industrial forests managed primarily for commercial timber production (J. Sauder, IDFG, unpublished data cited in IOSC 2010, p. 4), although it is unclear how fishers are using these environments, or the relative importance of each to supporting individuals or fisher populations. We expect that fishers' use of lands managed for timber production or multiple uses will occur in the future under conditions fostered by the continuance of current management. Therefore, we conclude that the best available scientific and commercial information does not indicate that current or future forest management practices and timber harvest threaten the fisher now, or in the foreseeable future.

Development and Roads

The USNRMs region encompasses large tracts of public lands with little or no development, wilderness areas, and numerous municipalities of varying size, low-density rural development, rail lines, road networks and other human developments. Most of the development and infrastructure, including national forest roads, have been on the landscape for decades (Baker
et al.
1993, p. 2; Havlick 2002, p. 11). Higher density development and road networks are situated in broad, open, lower-elevation intermountain valleys or lower montane areas, and most human activity and dwellings adjacent to public lands occur in dry woodlands or dry forest (Hessburg and Agee 2003, p. 47). Development in most cases is not far from public lands—primarily national forest. Mesic forest types and riparian corridors preferred by fishers are generally found at low to mid-elevations, and these highly productive habitats often coincide with areas that receive above average levels of human use (Carroll
et al.
2001, p. 962). Where development and roads coexist with these areas, habitat could be lost directly by replacement with infrastructure or removal of cover, and fishers could be impacted by increased susceptibility to direct mortality from vehicle collisions, and increased exposure to disease from pets and animals such as raccoons associated with human development (Ruediger 1994, p. 3; Carroll
et al.
2001, p. 969; Brown
et al.
2008, p. 23). We have no information that disease is a problem for fishers in the USNRMs, and reports of fisher mortality due to vehicle collision are few (Vinkey 2003, p. 32; Giddings 2010, pers. comm.) (see Factor C discussion below).

The secondary effects of human activity and infrastructure, and roads or road use, in causing fisher avoidance or inhibiting movement on the landscape are unclear. It is reported that fishers in California more often used areas with a greater than average density of low-use roads (Dark 1997, p. 50), and, in Maine, fishers seldom traveled in the vicinity of roads or powerline corridors (Coulter 1966, p. 61). Conversely, Arthur
et al.
(1989b, p. 687) found that fishers in Maine were fairly tolerant of human activity, including low-density housing, farms, roads, and gravel pits, if forest canopy cover was maintained in the vicinity. Roads in forested areas of the USNRMs are often constructed along riparian corridors or forested valley bottoms, which are habitats fishers prefer. Targeted surveys for fishers are often conducted near roads because of the ease of access and likelihood of detecting fisher in a preferred habitat. Fishers do not avoid areas adjacent to a minor State highway that traverses National Forest land in Idaho (Schwartz
et al.
2007, p. 6), and other targeted survey efforts for fishers in northern Idaho have successfully detected fishers in the vicinity of roads (Schwartz
et al.
2007, p. 6; Albrecht and Heusser 2009, p. 8). This would imply that fishers are not displaced from suitable habitat by the presence of roads or road use. Roads and landscape features such as rivers have been implicated in increasing mortality risk to dispersing fishers, but fishers have dispersed across, and did not appear to be affected by roads, lakes or rivers in other parts of the range (York 1996, p. 46; Fontana
et al.
1999, pp. 17; Weir and Corbould 2008, p. 44).

Roads constructed on public lands to provide access for resource use and extraction have been implicated in increasing access for trappers that target fishers or that may accidentally trap them (Hodgman
et al.
1994, p. 598). The closure of roads to provide grizzly bear (
Ursus arctos
) habitat security is a possible reason for the reduction in fishers harvested in Montana's Flathead and Swan Valley (Giddings 2010, pers. comm.). Recent changes in the USFS' travel management direction (70 FR 68264, November 9, 2005), require that national forest roads are managed in a manner compatible with wildlife resources. Accordingly, implementation of seasonal or permanent road closures to benefit the threatened grizzly bear has likely provided benefits to fishers in many parts of the USNRMs.

Rapid housing growth has occurred in close proximity to public lands in the Rocky Mountain region since the 1990s, with much of it situated in areas already considered wildland-urban interface and impacted by development (Alig
et al.
2010, p. 9). Additional residential development adjacent to public lands is expected to increase by 10 to 42 percent in some areas of the USNRMs by 2030 (Stein
et al.
2007, p. 8). The sale of private nonindustrial lands (
i.e.,
family-owned forests) currently managed for timber is a likely source for additional residential development (Alig
et al.
2010, pp. 6-7), although it is uncertain if a significant quantity of these lands is mesic forest or dry forest type less suitable for fishers.

There is a trend of large, industrially managed or corporate forest properties being divested for real estate development across the United States that is expected to continue into the future. Although large areas of industrial forest are predicted to be lost nationwide through 2050, most of this loss is due to urbanization in the southern United States (Alig
et al.
2010, pp. 14-15). We know that fishers utilize industrial forests in the USNRMs (IOSC 2010, p. 4). The availability of industrial forest lands for other uses will likely improve conditions for fishers in Montana, where over 1,253 km
2
(484 mi
2
) of low-elevation commercial forest, originally intended to be sold for development purposes was instead purchased for conservation and sustainable forestry by State, Federal, and conservation organizations (MTFWP 2010, Appendix 13, entire; The Nature Conservancy 2010, entire).

Dwellings, roads, and other infrastructure have been on the landscape for decades, and areas currently developed will see an increase in the density of development over the next 20 years. It is unknown if fisher habitats that are currently or potentially suitable will be affected directly by future development. The proximity and availability of public lands may moderate a loss of habitat if it occurs, but the impact to fishers is uncertain because of a lack of understanding of how fishers use the lands at the interface of public and private ownerships. Increased road traffic and

human presence and recreational demands on public lands may increase the risk to fisher of vehicle collisions and displacement from suitable habitats near areas of high human use. Reports of fishers' responses to human activity and the presence of roads are mixed and, therefore, difficult to conclude with certainty. Habitat loss and increased direct mortality resulting from increasing human development are a concern but, based on the available information, do not rise to a level of threat to the USNRMs fisher now, or in the foreseeable future.

Climate Change

We know of no element of the fisher's ecology or physiology that would be directly affected by changes in climate. Predicted climate changes could impact forested environments upon which fishers depend; therefore, we address climate change under Factor A.

Climate is influenced primarily by long-term patterns in air temperature and precipitation. The Intergovernmental Panel on Climate Change (IPCC) concluded that climate warming is unequivocal, and evident from observed increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level (IPCC 2007a, pp. 30-31). Continued greenhouse gas emissions at or above current rates are expected to cause further warming (IPCC 2007a, p. 30). Eleven of the 12 years from 1995 through 2006 rank among the 12 warmest years in the instrumental record of global average near-surface temperature since 1850 (Independent Scientific Advisory Board (ISAB) 2007, p. 7; IPCC 2007a, p. 30). During the last century, mean annual air temperature increased by approximately 0.6 °C (1.1 °F) (IPCC 2007a, p. 30). Warming appears to be accelerating in recent decades, as the linear warming trend over the 50 years from 1956 to 2005 (average 0.13 °C or 0.24 °F per decade) is nearly twice that for the 100 years from 1906 to 2005 (IPCC 2007a, p. 30). Climate change scenarios estimate that the mean air temperature could increase by over 3 °C (5.4 °F) by 2100 (IPCC 2007a, pp. 45-46). The IPCC also projects that there will likely be regional increases in the frequency of hot extremes, heat waves, and heavy precipitation, as well as greater warming in high northern latitudes (IPCC 2007a, p. 46). We recognize that there are scientific differences of opinion on many aspects of climate change, including the role of natural variability in climate. In our analysis, we rely primarily on synthesis documents that present the consensus of a large number of experts on climate change from around the world, as well as the scientific papers used in those reports, to represent the best available scientific information. Where possible, we used empirical data or projections specific to the western United States, which includes the Northern Rocky Mountain region, and have focused on observations or expected effects on forested ecosystems.

Specific regional projections for the Interior Columbia Basin and the USNRMs are warmer temperatures, with more precipitation falling as rain than snow, diminished snowpack and altered stream flow timing, increase in peak flow of rivers, and increasing water temperatures through the 21st century (to 2099) (Hansen
et al.
2001, p. 769; ISAB 2007, pp. iii, 15-16). The consequences of these projections are unclear and could result in positive, negative, or neutral impacts to fisher habitat and populations. Fisher habitat could expand due to warming temperatures extending the growing season and increased atmospheric carbon dioxide escalating vegetation growth and extending forest area (Millar
et al.
2006, pp. 48-49). It is hypothesized that climate change will produce greater tree species richness over much of the coterminous United States because of the current relatively greater species richness in warmer climates (Hansen
et al.
2001, p. 774). The potential habitats of dominant rainforest conifers (
e.g.,
western hemlock and red cedar that fishers use in the USNRMs) are expected to decrease west of the Cascades but expand into mountain ranges of the interior West (ISAB 2007, p. 26). If the hypothesis that fishers are limited by deep winter snow is correct (Raine 1981, p. 74; Krohn
et al.
1997, p. 226), decreased winter snowfall could increase the habitat available to fishers.

Changes in temperature and rainfall patterns are expected to shift the distribution of ecosystems northward (IPCC 2007b, p. 230) and up mountain slopes (McDonald and Brown 1992, pp. 411-412; IPCC 2007b, p. 232). Predicted climate shifts over the next century could result in the loss of alpine and subalpine spruce-fir forests, for example, forcing competition for prey between fishers and predators that are now occupying higher elevation niches (
e.g.,
lynx) (Koehler 1990, p. 848; Ruediger
et al.
2000, p. 3), or novel predator-prey interactions could evolve (ISAB 2007, pp. 26, 28). Increasing temperatures without additional moisture could stress vegetation, alter riparian systems, increase fire risk, and increase the susceptibility of forest vegetation to disease (Westerling
et al.
2006, p. 943; ISAB 2007, pp. 19, 25). Riparian areas are used extensively by fishers in the USNRMs (Jones 1991, pp. 90-93). Changing water regimes or decreased flow could decrease the productivity of riparian species and affect vegetation structure necessary for prey and security cover. The potential effects of climate change on the health of riparian systems could be exacerbated by the demands from increasing human population, development, and land use (Hansen
et al.
2002, p. 159).

Projected changes of climate could result in a wide range of potential outcomes for fishers and their habitat. The effects to fishers in either the short or long term in a focused geographic area cannot be reasonably discerned without a specific aspect of the species' ecology or physiology linked to a confidently projected climate change variable (
e.g.,
water temperature tolerance of fish, or early snowmelt reducing wolverine denning). Increasing temperatures and drought could affect fire frequency and intensity and the susceptibility of forest vegetation to disease, but climate change itself does not represent a threat to fishers now or in the foreseeable future.

Fire and Disease

Fire disturbance was an integral force in shaping the Northern Rocky Mountains forest ecosystem well before European settlement of the region (Lesica 1996, p. 33). Lower, drier elevations were prone to frequent, low-intensity burns, while cool high-elevation forests were subject to intense stand-replacing events at intervals up to 300 years (reviewed by Hessburg and Agee 2003, p. 27). The grand fir/hemlock/cedar forests known to support fisher today in Idaho have a history of highly variable mixed-intensity fire regimes. Fire severity and return intervals varied widely ranging from low-intensity fires with 16-year return intervals, to high-severity fires with 500-year return intervals (reviewed by Hessburg and Agee 2003, p. 27). Pre-European settlement forests would likely have been in a shifting mosaic of different successional stages, with 4 to 46 percent of the landscape of trees older than 200 years old (reviewed by Lesica 1996, p. 37). A fire history from 1650 to 1900 reveals that local fires or no fires occurred in most years. Occurring less often were extensive regional fire events in warm, dry summers that were preceded by warm springs: Eleven of these events occurred in the 20th century (Morgan
et al.
2008, p. 723). One of the largest regional fires

of the 20th century occurred in 1910, consuming over 11,675 km
2
(4507 mi
2
) in northern Idaho and scattered locations in northwest Montana (Morgan
et al.
2008, p. 721). Regional fires in the early 1900s consumed more mesic forest than regional fires in later years (Morgan
et al.
2008, p. 725). It has been suggested that the 1910 and 1934 fire events, in combination with overharvest by the fur industry, contributed to the fisher population decline (Jones 1991, p. 1).

Active fire suppression by humans in the mid-20th century has been implicated in the accumulation of forest vegetation believed to contribute to more fire-prone conditions today (Hessburg and Agee 2003, pp. 44, 46). However, a remarkable period between 1935 and 1987 was the longest period of low fire activity of the previous 250 years, and the lack of large fire activity was more a factor of cooler, wet climate conditions than fire suppression action (Morgan
et al.
2008, p. 726). An abrupt change occurred in the 1980s from a fire regime of infrequent large fires of short duration, to more frequent longer burning fires (Westerling
et al.
2006, p. 942). The shift was associated with unusually warm springs, longer summer dry seasons associated with reduced winter precipitation, and early spring snowmelt (Westerling
et al.
2006, p. 943), a climate pattern seen with historical regional fire regimes.

Since the 1980s, the Northern Rocky Mountains have seen the largest absolute increase in large wildfire activity in the forest types least affected by previous fire exclusion: Mesic mid-elevation and high-elevation forest types (Westerling
et al.
2006, p. 943). Climate model projections indicate decreased snowpack, earlier snowmelt, and increasing temperatures contributing to longer fire seasons (Westerling
et al.
2006, p. 943). Moisture patterns are more difficult to predict than temperature (Global Climate Change Impacts 2009, p. 135; Dai 2011, p. 16). Because many climate models predict higher precipitation levels associated with climate warming, the interaction between precipitation and temperature increase can be quite complex. If temperatures increase without compensating moisture patterns or amounts, the predicted warmer springs and summers could produce conditions favorable to the occurrence of large fires in the future, regardless of past trends (Westerling
et al.
2006, p. 943). If this occurs, increased fire frequency and intensity in forests cou

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2011-16349. Public record. Not legal advice.