Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List the North American Wolverine as Endangered or Threatened, 12929-12941 [E8-4197]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 73, Number 48 (Tuesday, March 11, 2008)]
[Proposed Rules]
[Pages 12929-12941]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-4197]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[FWS-R6-2008-0029; 1111 FY07 MO-B2]


Endangered and Threatened Wildlife and Plants; 12-Month Finding 
on a Petition To List the North American Wolverine as Endangered or 
Threatened

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
12-month finding on a petition to list as an endangered or threatened 
species under the Endangered Species Act of 1973, as amended (Act), the 
population of the North American wolverine (Gulo gulo luscus) that 
occurs in the contiguous United States. After a review of the best 
available scientific and commercial information, we have determined 
that the population of North American wolverine occurring in the 
contiguous United States does not constitute a listable entity under 
the Act. Therefore, we find that the petition to list the North 
American wolverine (Gulo gulo luscus) that occurs in the contiguous 
United States is not warranted for listing. The Service will continue 
to seek new information on the taxonomy, biology, ecology, and status 
of the North American wolverine and we will continue to support 
cooperative conservation of wolverines in the contiguous United States.

DATES: This finding was made on March 11, 2008.

ADDRESSES: This finding is available on the Internet at https://
www.regulations.gov. Supporting documentation we used to prepare 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. Please submit any new information, materials, comments, or 
questions concerning this finding to the above street address.

FOR FURTHER INFORMATION CONTACT: Mark Wilson, Field Supervisor, U.S. 
Fish and Wildlife Service, Montana Field Office (see ADDRESSES). 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 containing substantial scientific and commercial 
information that listing may be warranted, we make a finding within 12 
months of the date of receipt of the petition on whether the petitioned 
action is: (a) Not warranted, (b) warranted, or (c) warranted, but that 
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 Lists of Endangered and 
Threatened Wildlife and Plants. Section 4(b)(3)(C) of the Act requires 
that we treat a petition for which the requested action is found to be 
warranted but precluded as though resubmitted on the date of such 
finding, that is, requiring a subsequent finding to be made within 12 
months. We must publish these 12-month findings in the Federal 
Register.

Previous Federal Actions

    We received a petition dated August 3, 1994, from the Predator 
Project (now named the Predator Conservation Alliance) and Biodiversity 
Legal Foundation to list the North American wolverine in the contiguous 
United States as a threatened or endangered species under the Act and 
to designate critical habitat concurrent with listing. On April 19, 
1995, we published a finding (60 FR 19567) that the petition did not 
provide substantial scientific or commercial information indicating 
that listing the North American wolverine in the contiguous United 
States may be warranted. We did not make a determination as to whether 
the contiguous United States population of the North American wolverine 
constituted a distinct population segment or other listable entity.
    On July 14, 2000, we received another petition dated July 11, 2000, 
submitted by the Biodiversity Legal Foundation, Predator Conservation 
Alliance, Defenders of Wildlife, Northwest Ecosystem Alliance, Friends 
of the Clearwater, and Superior Wilderness Action Network, to list the 
North American wolverine within the contiguous United States as a 
threatened or endangered species under the Act and to designate 
critical habitat for the species concurrent with the listing.
    On October 21, 2003, we published a 90-day finding that the 
petition to list the North American wolverine in the contiguous United 
States did not present substantial scientific and commercial 
information indicating that listing as threatened or endangered may be 
warranted (68 FR 60112). We did not determine whether the contiguous 
United States population of the North American wolverine constituted a 
distinct population segment (or other listable entity), because 
sufficient information was not available at the time.
    On September 29, 2006, as a result of a complaint filed by 
Defenders of Wildlife and others alleging we used the wrong standards 
to assess the wolverine petition, the U.S. District Court, Montana 
District, ruled that our 90-day

[[Page 12930]]

petition finding was in error and ordered us to make a 12-month finding 
for the wolverine (Defenders of Wildlife et al. v. Norton and Hogan 
(9:05cv99 DWM; D. MT)). On April 6, 2007, the Court approved an 
unopposed motion to extend the deadline for this 12-month finding to 
February 28, 2008, so that we would be able to use information 
published in the September 2007 edition of the Journal of Wildlife 
Management containing a special section on North American wolverine 
biology. On June 5, 2007, we published a notice initiating a status 
review for the wolverine (72 FR 31048).

Species Biology

    The currently accepted taxonomy classifies wolverines worldwide as 
a single species, Gulo gulo. The wolverine has a holarctic 
distribution. Old and New World wolverines are divided into separate 
Old World and New World subspecies. Wolverines of Eurasia (Old World) 
comprise the subspecies G. g. gulo. Wolverines in the contiguous United 
States are a part of the New World or North American (United States and 
Canada) subspecies, G. g. luscus (Kurten and Rausch 1959, p. 19; 
Pasitschniak-Arts and Lariviere 1995, p. 1). The two subspecies differ 
in minor aspects of skull morphology (Kurten and Rausch 1959, p. 19), 
but significant differences in ecology, behavior, demography, or 
natural history do not appear to exist. Most authors, when discussing 
these aspects of wolverine biology, refer to New and Old World 
wolverines interchangeably (e.g., Pasitschniak-Arts and Lariviere 1995, 
entire). We consider the Old and New World subspecies to be similar and 
reliable enough to refer to information on Old World wolverines (G. g. 
gulo) as a surrogate for the North American wolverine in this finding 
when such information is not available specifically for the North 
American subspecies.
    The wolverine is the largest terrestrial member of the family 
Mustelidae. Adult males weigh 12 to 18 kilograms (kg) (26 to 40 pounds 
(lb)), and adult females weigh 8 to 12 kg (17 to 26 lb) (Banci 1994, p. 
99). The wolverine resembles a small bear with a bushy tail. It has a 
broad, rounded head; short, rounded ears; and small eyes. Each foot has 
five toes with curved, semi-retractile claws used for digging and 
climbing (Banci 1994, p. 99).
    Wolverines are opportunistic feeders and consume a variety of foods 
depending on availability. They primarily scavenge carrion, but also 
prey on small animals and birds, and eat fruits, berries, and insects 
(Hornocker and Hash 1981, p. 1290; Hash 1987, p. 579; Banci 1994, pp. 
111-113). Wolverines have an excellent sense of smell that enables them 
to find food beneath deep snow (Hornocker and Hash 1981, p. 1297). 
Wolverines consume large ungulate carrion when available. The most 
important food items in wolverine diets are large ungulate species, 
followed by small animals such as beaver, marmots, ground squirrels, 
rabbits, hares, porcupine, voles, ground nesting birds, and insects 
(Banci 1994, p. 112; Pasitschniak-Arts and Lariviere 1995, pp. 498-
499). The large ungulates in wolverine diets are assumed to be the 
result of scavenging, although wolverines are able to occasionally kill 
large ungulates in deep snow conditions when ungulate mobility is 
impaired (Pasitschniak-Arts and Lariviere 1995, pp. 498-499). Large 
ungulates comprise a larger proportion of the diet in winter than in 
snow-free seasons (Banci 1994, Table 5). The availability of large 
ungulate herds is of paramount importance for wolverines and the 
availability of large mammals underlies the wolverine's distribution, 
survival, and reproductive success (Banci 1994, p. 111).
    Wolverines have delayed onset of reproduction in females and small 
litter sizes. Studies of wolverine carcasses from trapper harvest have 
provided some useful data on reproductive parameters (Rausch and 
Pearson 1972, pp. 253-267; Liskop et al. 1981, pp. 472-476; Banci and 
Harestad 1988, pp. 266-268). These carcass studies indicate that a 
large number of female wolverines (40 percent) are apparently capable 
of giving birth at 2 years old, become pregnant most years, and produce 
average litter sizes of approximately 3.4 kits. However, carcass 
studies are subject to overestimating frequency of reproduction and the 
number of kits per litter, and underestimating the age at first 
reproduction because embryos are often resorbed by females that are 
energetically unable to complete pregnancy (Persson et al. 2006, p. 75; 
Inman et al. 2007c, p. 70). These aborted pregnancies result in corpora 
lutea (uterine scarring) in the female reproductive tract, leading to 
the erroneous conclusion that a female had reproduced at an early age 
and that litter sizes are relatively large.
    Field studies using radio telemetry are better able to determine 
the actual age at first reproduction and the actual number of kits 
successfully raised to weaning. Based on these studies, average age at 
first reproduction is likely more than 3 years (Inman et al. 2007c, p. 
70). Pregnant females commonly resorb or spontaneously abort litters 
when food availability is so low as to prevent successful completion of 
pregnancy or lactation to the time of weaning (Magoun 1985, pp. 30-31; 
Copeland 1996, p. 43; Persson et al. 2006, p. 77; Inman et al. 2007c, 
p. 70). Supplemental feeding of females increases reproductive 
potential (Persson 2005, p. 1456) and success at raising kits to the 
time of weaning, and indicates that food availability is likely to be a 
limiting factor for wolverine populations. In one study of known-aged 
females, none reproduced at age 2; 3 of 10 first reproduced at age 3; 
and 2 did not reproduce until age 4. The average age at first 
reproduction for this study was 3.4 years (rather than 2 years for the 
carcass studies above) (Persson et al. 2006, pp. 76-77). From these 
studies, we conclude that, by age three, nearly all female wolverines 
become pregnant every year, but energetic constraints resulting from 
low food availability result in loss of pregnancy about every other 
year. It is likely that, in many places in the range of wolverines in 
the lower 48 States, it takes 2 years of foraging for a female to store 
enough energy to successfully reproduce (Persson 2005, p. 1456; Inman 
et al. 2007c, Table 3).
    Breeding generally occurs from late spring to early fall (Magoun 
and Valkenburg 1983, p. 175; Mead et al. 1991, pp. 808-811). Females 
undergo delayed implantation until the following winter to spring, when 
active gestation lasts from 30 to 40 days (Rausch and Pearson 1972, pp. 
254-257). Litters are born between February and April and contain 1 to 
5 kits, with an average in North America of between 1 and 2 kits 
(rather than 3.4 kits, as indicated by carcass studies) (Magoun 1985, 
pp. 28-31; Copeland 1996, p. 36; Krebs and Lewis 1999, p. 698; Copeland 
and Yates 2006, pp. 32-36; Inman et al. 2007c, p. 68).
    Several aspects related to reproductive denning are significant to 
wolverine reproductive success (Banci 1994, p. 110; Magoun and Copeland 
1998, p. 1319; Inman et al. 2007c, p. 71). Female wolverines use two 
kinds of dens for reproduction. Females use natal (birthing) dens to 
give birth and raise kits early postpartum, and in some cases females 
may raise kits to weaning in the natal den. However, in most situations 
prior to weaning, females may move kits to one or multiple alternative 
den sites, which are referred to as maternal dens. The female then 
raises her kits to weaning in the maternal den. The movement of kits 
from natal to maternal dens may be a response by the female to den 
disturbance, better food

[[Page 12931]]

availability in the new location, predation risk, or deteriorating den 
conditions in the natal den (Magoun and Copeland 1998, pp. 1316-1319).
    Female wolverines use natal dens that are excavated in snow. 
Persistent, stable snow greater than 1.5 meters (m) (5 feet (ft)) deep 
appears to be a requirement for natal denning, presumably because it 
provides security for offspring and buffers cold winter temperatures 
(Pulliainen 1968, p. 342; Copeland 1996, pp. 92-97; Magoun and Copeland 
1998, pp. 1317-1318; Banci 1994, pp. 109-110; Inman et al. 2007c, pp. 
71-72). Female wolverines go to great lengths to find secure den sites, 
suggesting that predation is a concern (Banci 1994, p. 107). Natal dens 
consist of tunnels that contain well-used runways and bed sites, and 
that may naturally incorporate shrubs, rocks, and downed logs as part 
of their structure (Magoun and Copeland 1998, pp. 1315-1316; Inman et 
al. 2007c, pp. 71-72). In Idaho, natal den sites occur above 2,500 m 
(8,200 ft) on rocky sites, such as north-facing boulder talus or 
subalpine cirques in forest openings (Magoun and Copeland 1994, pp. 
1315-1316). In Montana, natal dens occur above 2,400 m (7,874 ft) and 
are located on north aspects in avalanche debris, typically in alpine 
habitats near timberline (Inman et al. 2007c, pp. 71-72).
    Dens (natal and maternal) are typically used from early February 
through late April or early May (Myrberget 1968, p. 115; Magoun and 
Copeland 1998, pp. 1314-1317; Inman et al. 2007b, pp. 55-59). 
Occupation of natal dens is variable, ranging from approximately 9 to 
65 days depending on whether or not the female wolverine perceives the 
need to move her kits (Magoun and Copeland 1998, pp. 1316-1317). 
Females may use multiple secondary (maternal) dens (Pulliainen 1968, p. 
343; Myrberget 1968, p. 115), or use of maternal dens may be minimal 
(Inman et al. 2007c, p. 69). Timing of den abandonment is related to 
accumulation of water in dens (snow melt), the maturation of offspring, 
disturbance, and geographic location (Myrberget 1968, p. 115; Magoun 
1985, p. 73). Post-weaning dens are called rendezvous sites. These dens 
may be used through early July. Females leave their kits at rendezvous 
sites while foraging, and return periodically to provide food for the 
kits. These sites are characterized by natural (unexcavated) cavities 
formed by large boulders, downed logs (avalanche debris), and snow 
(Inman et al. 2007c, pp. 55-56).

Habitat and Home Range

    In North America, wolverines occur within a wide variety of arctic, 
sub-arctic and alpine habitats, primarily boreal forests, tundra, and 
western mountains throughout Alaska and Canada; however, the southern 
portion of their range extends into the contiguous United States, 
including Washington, Idaho, Montana, and Wyoming (Wilson 1982, p. 644; 
Hash 1987, p. 576; Banci 1994, p. 102, Pasitschniak-Arts and Lariviere 
1995, p. 499; Aubry et al. 2007, p. 2152). In the contiguous United 
States, wolverines are restricted to high-elevation habitats in the 
Rocky Mountains and North Cascades containing the arctic and sub-arctic 
conditions they require.
    Home ranges of wolverines are large, but vary greatly depending on 
availability of food, gender, age, and differences in habitat. The 
availability and distribution of food is likely the primary factor in 
determining wolverine movements and home range size (Hornocker and Hash 
1981, p. 1298; Banci 1994, pp. 117-118). Wolverines travel long 
distances over rough terrain and deep snow, and adult males generally 
cover greater distances than females (Hornocker and Hash 1981, p. 1298; 
Banci 1994, pp. 117-118). Home ranges of adult wolverines are 
approximately 100 square kilometers (km\2\) to over 900 km\2\ (38.5 
square miles (mi\2\) to 348 mi\2\) (Banci 1994, p. 117). Average home 
ranges of resident adult females in central Idaho are 384 km\2\ (148 
mi\2\), and average home ranges of resident adult males are 1,522 km\2\ 
(588 mi\2\) (Copeland 1996, p. 50). Wolverines in Glacier National Park 
have average male home ranges of 496 km\2\ (193 mi\2\) and female home 
ranges of 141 km\2\ (55 mi\2\) (Copeland and Yates 2006, p. 25). 
Wolverines in the Greater Yellowstone Area have average adult male home 
ranges of 797 km\2\ (311 mi\2\) and average adult female home ranges of 
329 km\2\ (128 mi\2\) (Inman et al. 2007a, p. 4). Home ranges for 
carnivores of similar body size are smaller than wolverine home ranges 
at their southern range terminus. Canada lynx in the United States 
Rocky Mountains average 122 km\2\ (47 mi\2\) (Aubry et al. 2000, pp. 
383-384), and coyote home ranges extend from 2.5 to 15 km\2\ (1 to 5.8 
mi\2\) (Chronert 2007, p. 2).
    Wolverine home ranges at the southern terminus of the current range 
are large for mammals of the size of wolverines, and may indicate that 
wolverines have high energetic requirements and at the same time occupy 
relatively unproductive niches (Inman et al. 2007a, p. 11). In 
addition, wolverines naturally occur in low densities that average 
about one wolverine per 150 km\2\ (58 mi\2\) (Hornocker and Hash 1981, 
pp. 1292-1295; Hash 1987, p. 578; Copeland 1996, pp. 31-32; Copeland 
and Yates 2006, p. 27; Inman et al. 2007a, p. 10; Squires et al. 2007, 
p. 2218).

Wolverine Status in Canada and Alaska

    The bulk of the range of North American wolverines is found in 
Canada and Alaska. Wolverines inhabit alpine tundra, boreal forest, and 
arctic habitats in western Canada and Alaska (Slough 2007, p. 78). 
Wolverines in Canada have been divided into two populations for 
management by the Canadian government: an eastern population in 
Labrador and Quebec; and a western population that extends from Ontario 
to the Pacific coast, and north to the Arctic Ocean. The eastern 
population is currently listed as endangered under the Species At Risk 
Act in Canada, and the western population is designated as a species of 
special concern (COSEWIC 2003, p. 8).
    The current status of wolverines in eastern Canada is uncertain. 
Wolverines have not been confirmed to occur in Quebec since 1978 
(Fortin et al. 2005, p. 4). Historical evidence of wolverine presence 
in eastern Canada is also suspect because no evidence exists to show 
that wolverine pelts attributed to Quebec or Labrador actually came 
from that region; possibly animals were trapped elsewhere and the pelts 
were shipped through the eastern provinces (COSEWIC 2003, p. 20). 
Wolverines in eastern Canada may currently exist in an extremely low-
density population, or may be extirpated. Wolverines in eastern Canada, 
both historically and currently, could represent migrants from western 
populations that never became resident animals (COSEWIC 2003, pp. 20-
21). The government of Canada has completed a recovery plan for the 
eastern population with the goal of establishing a self-sustaining 
population through reintroduction and protection (Fortin et al. 2005, 
p. 16).
    Wolverines in western Canada and Alaska inhabit a variety of 
habitats from sea level to high elevations in mountains (Slough 2007, 
pp. 77-78). In Canada, they occur in Ontario, Manitoba, Saskatchewan, 
Alberta, British Columbia, Yukon, Northwest Territories, and Nunavut 
(Slough 2007, pp. 77-78). Since European colonization, a generally 
recognized range contraction has taken place in boreal Ontario and the 
aspen parklands of Manitoba, Saskatchewan, and Alberta (COSEWIC 2003, 
pp. 20-21; Slough 2007, p. 77). This range contraction

[[Page 12932]]

occurred concurrently with a reduction in wolverine records for the 
Great Lakes region in the lower 48 States (Aubry et al. 2007, pp. 2155-
2156). Causes of these changes are uncertain, but may be related to 
increased harvest, habitat modification, or climate change (COSEWIC 
2003, pp. 20-21; Aubry et al. 2007, pp. 2155-2156; Slough 2007, pp. 77-
78). Analysis supports climate change as a contributing factor to 
declines in wolverine populations in southern Ontario, because snow 
conditions necessary to support wolverines do not currently exist in 
the Great Lakes region of the lower 48 States, and are marginal in 
southern Ontario (Aubry et al. 2007, p. 2154). Wolverines occurred 
historically on Vancouver Island and have been given status as a 
separate subspecies by some (Hall 1981, p. 109). The Vancouver Island 
population is now regarded as possibly extirpated; no sightings have 
occurred since 1992 (COSEWIC 2003, p. 18).
    Wolverines in western Canada and Alaska appear to persist where 
habitat and climate conditions are favorable (COSEWIC 2003, pp. 13-21; 
Aubry et al. 2007, pp. 2152-2155; Slough 2007, p. 79). Throughout this 
area, wolverines are managed by regulated harvest at the Province and 
State level. Population estimates for Canada and Alaska are approximate 
because no wolverine surveys have taken place at the State or national 
scale. However, the population in western Canada includes an estimated 
15,089 to 18,967 individuals, based on population densities and 
occupied area (COSEWIC 2003, p. 22). The number of wolverines in Alaska 
is unknown, but they appear to exist at naturally low densities in 
suitable habitats throughout Alaska (Alaska Department of Fish and Game 
2004, pp. 1-359). We have no information to indicate that wolverine 
populations have been reduced in numbers or geographic range in Alaska.

Wolverine Status in the Contiguous United States

    The delineation of the historical and present distribution of 
wolverine is inherently difficult for several reasons. Wolverines tend 
to live in remote and inhospitable places away from human populations. 
Wolverines naturally occur at low densities and are rarely and 
unpredictably encountered where they do occur. Wolverines often move 
long distances in short periods of time when dispersing from natal 
ranges (Aubry et al. 2007, p. 2147), making it difficult to distinguish 
with confidence between occurrence records that represent established 
populations and those that represent short-term occupancy without the 
potential for establishment of home ranges and reproduction. These 
natural attributes of wolverines make it difficult to determine their 
present range, or trends in range expansion or contraction that may 
have occurred in the past. Therefore, we must be cautious when trying 
to determine where past wolverine populations occurred, and where 
application of conservation actions may be possible in the future.
    Aubry et al. (2007, entire) represents the best available science 
on the wolverine's geographic range in the contiguous United States. 
This study (2007, pp. 2147-2148) used verifiable and documented records 
from museum collections, literature sources, and State and Federal 
institutions to trace changes in geographic distribution of wolverines 
in the historic record. Aubry et al.'s (2007) focus on verifiable and 
documented records corrected past overly broad approaches to wolverine 
range mapping (Nowak 1973, p. 22; Hall 1981, p. 1009; Wilson 1982, p. 
644; Hash 1987, p. 576) that used a more inclusive but potentially 
misleading approach when dealing with extralimital records (i.e., 
records from outside of established, reproducing populations). Aubry et 
al. (2007, p. 2155) concluded that these records represent individuals 
dispersing from natal ranges that often end up in habitats that cannot 
support wolverines, and their use in determining the potential range of 
wolverine can overestimate the area that can actually be used by 
wolverines for home ranges and breeding.
    Aubry et al. (2007, pp. 2147-2148) divided records into 
``historical'' (recorded prior to 1961), ``recent'' (recorded between 
1961 and 1994), and ``current'' (recorded after 1994). Historical 
records occurred before systematic surveys and encompass the time 
during which wolverine numbers and distribution were hypothesized to be 
at their lowest, in the first half of the 1900s (Wright and Thompson 
1935; Grinnell et al. 1937; Allen 1942; Newby and Wright 1955, all as 
cited in Aubry et al. 2007, p. 2148). The recent time interval covers a 
hypothesized population expansion and rebound from an earlier low 
(Aubry et al. 2007, pp. 2148-2149). Current records are considered by 
Aubry et al. (2007, p. 2148) to be a reliable depiction of where 
populations occur now.

Wolverine Distribution in the Contiguous United States

    Using data from Aubrey et al. 2007, we assessed the historical, 
recent, and current distribution data for each of six geographical 
regions to determine the likelihood of the presence of historical 
populations (rather than extralimital dispersers). Table 1 illustrates 
wolverine numbers in the six geographic areas assessed by Aubry et al. 
(2007, Table 1). More detail on wolverine distribution over time is 
included in the text that follows.

[[Page 12933]]



                                     Table 1.--Verifiable and Documented Records of Wolverine Occurrence in the Contiguous United States by Region and State
                                                                          [Reproduced from Aubrey et al. 2007, p. 2151]
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                                                                          Historical records                                                 Recent records               Current
                                     ----------------------------------------------------------------------------------------------------------------------------------   records    Most recent
          Region and State                                                                                                                                             -------------  verifiable
                                         1800s      1901-1910    1911-1920    1921-1930    1931-1940    1941-1950    1951-1960    1961-1970    1971-1980    1981-1994    1995-2005      record
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Pacific Coast Mountains:
    Washington......................           17            3            7            0            0            1            1           10            3            4            7         2003
    Oregon..........................            0            0            1            1            0            0            0            2            2            2            0         1992
    California......................           11            7            9           30            0            0            1            0            0            0            0         1922
Rocky Mountains:
    Idaho...........................            6            5            5            2            0            3            4            5            5       \a\ 31       \b\ 16         2005
    Montana.........................            6            1            1            0            4            9           39           14      \c\ 121      \d\ 149      \e\ 187         2005
    Wyoming.........................           10            6            1            1            0            0            0            1            0            0       \f\ 12         2005
    Utah............................            8            0            1            1            0            0            0            0            0            0            0         1921
    Nevada..........................            0            0            0            0            0            0            0            0            1            0            0         1972
    Colorado........................           22            7            5            0            0            0            0            0            0            0            0         1919
    New Mexico......................            1            0            0            0            0            0            0            0            0            0            0         1860
Central Great Plains:
    North Dakota....................           35            0            1            0            0            0            0            0            0            0            0         None
    South Dakota....................            0            0            0            0            0            0            0            1            0            0            0         1962
    Nebraska........................            1            0            0            0            0            0            0            0            0            0            0         1887
Great Lakes:
    Minnesota.......................            6            0            1            2            1            0            0            1            0            0            0         1899
    Wisconsin.......................           12            1            0            1            0            0            0            0            0            0            0    \g\ 1800s
    Michigan........................           11            0            0            1            0            0            0            0            0            0            0         1868
Upper Midwest:
    Iowa............................            0            0            0            0            0            0            1            0            0            0            0         1960
    Indiana.........................            2            0            0            0            0            0            0            0            0            0            0         None
    Ohio............................            0            0            0            0            0            1            0            0            0            0            0         1943
Northeast:
    Pennsylvania....................            4            0            0            0            0            0            0            0            0            0            0         None
    New York........................            3            0            0            0            0            0            0            0            0            0            0         1811
    New Hampshire...................            0            0            2            0            0            0            0            0            0            0            0         None
    Vermont.........................            3            0            0            0            0            0            0            0            0            0            0         None
    Maine...........................            1            0            0            0            0            0            0            0            0            0            0        None
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Includes 16 initial capture locations obtained from 1992 to 1994 during a radiotelemetry study.
\b\ Includes 3 initial capture locations obtained in 1995 during a radiotelemetry study and 4 initial capture locations obtained from 2003 to 2005 during a radiotelemetry study.
\c\ Includes 94 harvest records from 1974 to 1980 compiled by the MT Department of Fish, Wildlife, and Parks and 24 wolverines that were radiocollared by Hornocker and Hash (1981) in
  northwestern MT from 1972 to 1977.
\d\ Includes 146 harvest records from 1981 to 1994 compiled by the MT Department of Fish, Wildlife, and Parks.
\e\ Includes 115 harvest records from 1995 to 2004 compiled by the MT Department of Fish, Wildlife, and Parks and 49 initial capture locations obtained from 2002 to 2005 during radiotelemetry
  studies.
\f\ Includes 9 initial capture locations obtained from 1998 to 2005 during telemetry studies.
\g\ Jackson (1954) found 2 wolverine specimens in a cave in southwestern WI in 1920 that he estimated had been in the deposit for > 50 years.


[[Page 12934]]

    Northeast and Upper Midwest. The low number of records and the 
scattered nature of their distribution suggest that wolverines were 
likely to have been occasional transients to the area and not present 
as a reproducing population after 1800.
    Great Lakes. The low number of verifiable records in this area of 
relatively high human population density (compared with, for example, 
the Rocky Mountains) suggests that wolverines did not exist in this 
area as a viable population after 1900. Widely scattered records 
generally before 1900, with an occasional record after that year, 
suggest that if a reproducing population existed in the Great Lakes, it 
predated 1900, and that post-1900 records represent dispersal from a 
receding Canadian population. Wolverine distribution in Ontario, Canada 
appears to have receded north from the Great Lakes region beginning in 
the 1800s, and currently wolverines occupy only the northern portion of 
the province, a distance of over 650 km (404 mi) from the U.S. border 
(COSEWIC 2003, p. 9). The pattern of declining numbers of records for 
the Great Lakes region illustrated in Aubry et al. (2007, p. 2152) is 
consistent with what would be expected if those records were of 
dispersing individuals from a Canadian population that receded 
progressively farther north into Canada after 1900.
    Central Great Plains. The lack of verifiable and mappable records 
from the Great Plains States leaves little evidence on which to 
determine if reproducing populations of wolverines ever inhabited this 
area. Thirty-five of 36 records from North Dakota are from the journals 
of a single fur trader, and it is not clear that the records represent 
actual collection localities or localities where trades or shipments 
occurred (Aubry et al. 2007, entire). The habitat relationships of 
wolverines include the Hudsonian life zone, subarctic, and tundra with 
persistent spring snow, all features that the Central Great Plains lack 
and lacked throughout the historic period (Aubry et al. 2007, pp. 2151-
2152). Therefore, it is unlikely that these records represent 
established wolverine individuals or populations, or that this area 
contained wolverine habitat.
    Rocky Mountains. Five Rocky Mountains States (Idaho, Montana, 
Wyoming, Colorado, and Utah) as a region contain numerous wolverine 
records over all time intervals. Mappable records appear to coalesce 
around several areas that may have been population centers, such as 
central Colorado, the Greater Yellowstone Area, and northern Idaho/
northwestern Montana. The large number of verifiable and mappable 
records for this region, along with the suggestion of population 
centers or strongholds, suggests that wolverines existed in reproducing 
populations throughout much of the Rocky Mountains during the 
historical interval. During the recent interval, the lack of records 
for Colorado and Utah suggest that the southern Rocky Mountain 
population of wolverines was extirpated by the middle 1900s, concurrent 
with widespread systematic predator control by government agencies and 
livestock interests. The northern Rocky Mountain population (north of 
Wyoming) was reduced to historic lows during the early 1900s, and then 
increased dramatically in the second half of the 1900s as predator 
control efforts subsided and trapping regulations became more 
restrictive (Aubry et al. 2007, p. 2151). This increase may indicate 
that the population rebounded from historic lows in this period, but we 
cannot rule out that the apparent rebound is an artifact of improved 
monitoring of wolverine trapping by government agencies. Wolverine 
records from 1995 to 2005 show that wolverine populations currently 
exist in the northern Rocky Mountains. Ongoing legal trapping in 
Montana removes an average of 10.5 individuals from this population 
each year (Montana Department of Fish, Wildlife, and Parks 2007, p. 2). 
During all time periods, populations of wolverines in British Columbia 
and Alberta may have been a source of surplus wolverines during 
population lows (COSEWIC 2003, pp. 18-19).
    Pacific Coast. Historically, records from Washington, Oregon, and 
California clearly coalesced around two population centers in the North 
Cascades and the Sierra Nevada. Records from these areas are separated 
by a lack of historic records in southern Oregon and northern 
California, indicating that the distribution of wolverines in this area 
is best represented by two disjunct populations rather than a 
continuous peninsular extension from Canada. This conclusion is 
supported by genetic data indicating that the Sierra Nevada and North 
Cascades wolverines were separated for at least 2,000 years prior to 
extirpation of the Sierra Nevada population (Schwartz et al. 2007, p. 
2174). One Sierra Nevada record exists from after 1930, indicating that 
this population was extirpated in the first half of the 1900s 
concurrent with widespread systematic predator control programs. 
Records from the North Cascades continue into present times in 
relatively small numbers, indicating a population persists in this 
area. Records from British Columbia, Canada indicate that the North 
Cascades population may be connected with, and possibly dependent on, 
the larger Canadian population for viability over the long term.

Summary of Wolverine Distribution Patterns in the Contiguous United 
States

    Historical wolverine records were found across the northern tier of 
the lower 48 States with peninsular extensions south into the southern 
Rockies and the Sierra Nevada (Aubry et al. 2007, p. 2152).
    Currently, wolverines appear to be distributed in two regions in 
the lower 48 States: the North Cascades in Washington (and possibly 
Oregon), and the northern Rocky Mountains in Idaho, Montana, and 
Wyoming. Wolverines were extirpated in historical times from the Sierra 
Nevada and the southern Rocky Mountains. We conclude that the current 
range of the species in the contiguous United States includes the North 
Cascades Mountains and the northern Rocky Mountains.
    We also conclude that wolverines likely either did not exist as 
established populations or were extirpated prior to settlement and the 
compilation of historical records in the Great Lakes region. The widely 
scattered records from this region are consistent with dispersing 
individuals from a Canadian population that receded north early in the 
1800s. We cannot rule out the possibility that wolverines existed as 
established populations prior to the onset of trapping in this area, 
but we have no evidence that they did.
    No evidence in the historical records suggests that wolverines were 
ever present as established populations in the Great Plains, Midwest, 
or Northeast.

Habitat Relationships and Wolverine Distribution in the Contiguous 
United States

    Aubry et al. (2007, pp. 2152-2156) compared several broad-scale 
habitat types to historic, recent, and current wolverine records to 
investigate correlations in habitat use and determine what habitat 
types might best predict wolverine occurrence. Spring snow cover (April 
15 to May 14) is the best overall predictor of wolverine occurrence. 
Snow cover during the denning period is essential for successful 
wolverine reproduction rangewide (Hatler 1989, p. iv; Magoun and 
Copeland 1998, p. 1317; Inman et al. 2007c, pp. 71-72; Persson 2007, p. 
1). Wolverine dens tend to be in areas of high structural diversity 
such as logs

[[Page 12935]]

and boulders with deep snow (Magoun and Copeland 1998, p. 1317; Inman 
et al. 2007c, pp. 71-72; Persson 2007, entire). Reproductive females 
dig deep snow tunnels to reach the protective structure of logs and 
boulders where they produce offspring. This behavior presumably 
protects the vulnerable kits from predation by large carnivores, 
including other wolverines (Pulliainen 1968, p. 342; Zyryanov 1989, pp. 
3-12), but may also have physiological benefits for kits by buffering 
them from extreme cold, wind, and desiccation (Pullianen 1968, p. 342; 
Bj[auml]rvall et al. 1978, p. 23).
    All of the areas in the lower 48 States for which good evidence of 
persistent wolverine populations exists (i.e., Cascades, Sierra Nevada, 
northern and southern Rockies) contain large and well-distributed areas 
with deep snow cover that persists through the wolverine denning period 
(Brock et al. 2007, pp. 36-53; Aubry et al. 2007, p. 2154). The Great 
Plains, Great Lakes, Midwest, and Northeast lack the spring snow 
conditions thought to be required by wolverines for successful 
reproduction (Aubry et al. 2007, p. 2154). This finding supports the 
exclusion of the Great Plains, Great Lakes, Midwest, and Northeast from 
the current range of wolverines. Whether wolverines once existed as 
established populations in any of these regions is unknown, but the 
consistent lack of deep spring snow in these regions appears to 
currently preclude the wolverine's presence as a reproducing 
population.
    Large areas of habitat with characteristics suitable for wolverines 
still occur in the southern Rocky Mountains and Sierra Nevada where 
wolverines have been extirpated (Aubry et al. 2007, p. 2154; Brock et 
al. 2007, p. 26). The occurrence data suggest that wolverine 
extirpations in these areas were coincidental with systematic predator 
eradication efforts in the early 1900s, which have been discontinued 
for many years. Wolverines failed to recolonize these areas since the 
cessation of eradication programs, by the mid-20th century, of 
widespread predator control efforts. This may be the result of the long 
dispersal distance between these areas and extant populations.
    We conclude that areas of wolverine historical occurrence can be 
placed in one of three categories: (1) Areas where wolverines are 
extant as reproducing and potentially self-sustaining populations 
(North Cascades, northern Rocky Mountains); (2) areas where wolverines 
historically existed as reproducing and potentially self-sustaining 
populations prior to human-induced extirpation, and where 
reestablishment of populations is possible given current habitat 
conditions and management (the Sierra Nevada mountains in California 
and southern Rocky Mountains in Colorado); and (3) areas where 
historical presence of wolverines in reproducing and potentially self-
sustaining populations is doubtful, and where the current habitat 
conditions preclude the establishment of populations in the foreseeable 
future (Great Plains, Midwest, Great Lakes, and Northeast). Further, on 
the basis of the historic and current records and distribution of 
suitable habitat, we consider the current range of wolverines to 
include suitable habitat in the North Cascades of Washington and 
Oregon, and northern Rocky Mountains of Idaho, Wyoming, and Montana.

Wolverine Population Estimate for the Contiguous United States

    Current population level and trends remain unknown because no 
systematic population census exists over the entire current range of 
the wolverine in the lower 48 States. However, we can estimate the 
potential carrying capacity of a population in a given region by using 
available data on population density, extent of habitat, and wolverine 
distribution. Using the projections of wolverine habitat found in Brock 
et al. (2007, pp. 36-53), Montana, Idaho, and Wyoming could potentially 
support between 499 and 655 individual wolverines (Inman 2007a, 
entire). This range is almost certainly an overestimate of actual 
wolverine numbers because it assumes that all suitable habitat is 
currently occupied, which is not the case (Murphy et al. 2007, p. 2). 
Therefore, we consider the lower range estimate of about 500 wolverines 
from Inman (2007a, entire) to be a reasonable estimate of the current 
wolverine population in the northern Rocky Mountains. The three 
northern Rocky Mountain States provide the bulk of currently occupied 
habitat in the contiguous United States, with the only additional known 
occupied area being the North Cascades mountain range in Washington 
State. The size of the North Cascades population is unknown, but is 
likely to be much smaller than the northern Rocky Mountain population 
due to the small size of the occupied area (Aubry et al. 2007, Fig. 4) 
and is unlikely to increase the estimated population significantly.

Distinct Vertebrate Population Segment (DPS)

    Under section 4(a)(1) of the Act, we must determine whether any 
species is an endangered species or a threatened species because of any 
of the five threat factors identified in the Act. Section 3(16) of the 
Act defines ``species'' to include ``any subspecies of fish or wildlife 
or plants, and any distinct population segment of any species of 
vertebrate fish or wildlife which interbreeds when mature'' (16 U.S.C. 
1532 (16)). To interpret and implement the distinct population segment 
portion of the definition of a species under the Act and Congressional 
guidance, the Service and the National Marine Fisheries Service (now 
the National Oceanic and Atmospheric Administration-Fisheries) 
published, on February 7, 1996, an interagency Policy Regarding the 
Recognition of Distinct Vertebrate Population Segments under the Act 
(DPS Policy; 61 FR 4722). The policy allows for more refined 
application of the Act that better reflects the conservation needs of 
the taxon being considered, and avoids the inclusion of entities that 
may not warrant protection under the Act.
    Under our DPS Policy, three elements are considered in a decision 
regarding the status of a possible DPS as endangered or threatened 
under the Act. These are applied similarly for additions to the Lists 
of Endangered and Threatened Wildlife and Plants, reclassification, and 
removal from the Lists. They are: (1) Discreteness of the population 
segment in relation to the remainder of the taxon; (2) the significance 
of the population segment to the taxon to which it belongs; and (3) the 
population segment's conservation status in relation to the Act's 
standards for listing (i.e., whether the population segment is, when 
treated as if it were a species, endangered or threatened). 
Discreteness refers to the isolation of a population from other members 
of the species, and we evaluate this based on specific criteria. If a 
population segment is considered discrete, we must consider whether the 
discrete segment is ``significant'' to the taxon to which it belongs by 
using the best available scientific information. If we determine that a 
population segment is discrete and significant, we then evaluate it for 
endangered or threatened status based on the Act's standards. The DPS 
evaluation in this finding concerns the segment of the wolverine 
species occurring within the contiguous United States, including the 
northern Rocky Mountains and the North Cascades.

[[Page 12936]]

Analysis for Discreteness

    Under our DPS Policy, a population segment of a vertebrate species 
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); or (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 (see 
``International Border Issues'' section below for a discussion of the 
standard set by section 4(a)(1)(D)). Below is our discussion of the 
wolverine population within the contiguous 48 United States relative to 
the discreteness criterion of the DPS policy.

Markedly Separated From Other Populations of the Taxon

    The population of the North American wolverine addressed in the 
petition, and that we have evaluated for consideration as a DPS, 
incorporates wolverine populations south of the international border 
with Canada, inclusive of the States of Idaho, Montana, Washington, and 
Wyoming (hereafter referred to as the U.S. population). The U.S. 
population is connected to wolverine populations in Canada and is 
likely dependent on them to some degree for maintaining genetic 
diversity. Therefore, the U.S. population of the North American 
wolverine does not meet the markedly separated criterion of the DPS 
Policy.

International Border Issues

    A population segment of a vertebrate species may also be considered 
discrete if 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. Section 
4(a)(1)(D) of the Act is the factor concerning the adequacy of existing 
regulatory mechanisms in the Act's ``5-factor'' analysis for 
determining whether a species is threatened or endangered. In assessing 
a population for discreteness based on delimitation by international 
governmental boundaries, we focus specifically on whether the factors 
named above are significantly different between the two countries 
because of the inadequacy of existing regulatory mechanisms. In order 
to demonstrate that a population is discrete based on international 
governmental boundaries, it is not enough that there are differences in 
control of exploitation, management of habitat, conservation status, or 
regulatory mechanisms across the international boundary; the 
differences must be significant and relate to inadequate regulatory 
mechanisms.. Following is our assessment of the U.S. population and 
wolverines in the rest of North America in terms of differences in 
control of exploitation, management of habitat, conservation status, 
and regulatory mechanisms.

Differences in Management of Habitat

    Wolverine habitat in North America occurs in arctic, sub-arctic, 
and alpine habitats, and typically in areas remote from human presence 
and development. In the contiguous United States, wolverines are 
restricted to high-elevation habitats in the Rocky Mountains and North 
Cascades containing the arctic and sub-arctic conditions that they 
require (Wilson 1982, p. 644; Hash 1987, p. 576; Banci 1994, p. 102, 
Pasitschniak-Arts and Lariviere 1995, p. 499; Aubry et al. 2007, p. 
2152). Wolverine habitat is generally characterized by the absence of 
human presence and development (Hornocker and Hash 1981, p. 1299; Banci 
1994, p 114; Landa et al. 1998, p. 448; Rowland et al. 2003 p. 101; 
Copeland 1996, pp. 124-127; Krebs et al. 2007, pp. 2187-2190). In both 
the contiguous United States and Canada, little habitat management 
occurs in areas frequented by wolverines. Therefore, we find that there 
are no significant differences in management of habitat for wolverines 
that relate to the status of the species between the contiguous United 
States and Canada.

Differences in Conservation Status

Biological Status

    Throughout its current range in Canada and Alaska, wolverines exist 
in well-distributed, interconnected, large populations. Conversely, 
wolverines in the contiguous United States appear to exist in small, 
fragmented, and semi-isolated populations that put them at greater risk 
of being lost due to catastrophic or stochastic events than those 
populations to the north in Canada and Alaska. These risks result from 
three main factors: (1) Small total population size, (2) effective 
population size below that needed to maintain genetic diversity and 
demographic stability, and (3) the fragmented nature of wolverine 
habitat in the contiguous United States that results in smaller, 
isolated, ``sky island'' patches separated by unsuitable habitats. 
These three factors are explained in more detail below; in addition, we 
summarize how they relate to section 4(a)(1)(D) of the Act.

Small Total Population Size

    The total population sizes for wolverines in Canada and Alaska, and 
the contiguous United States, differ by more than an order of 
magnitude. As explained in the ``Wolverine Population Estimate for the 
Contiguous United States'' section above, the contiguous U.S. 
population likely numbers approximately 500 adult individuals (Inman 
2007a, entire). This total population is divided into smaller sub-
populations inhabiting semi-isolated habitat fragments in major 
mountain ranges (Aubry et al. 2007, Figs. 2b, 4). The population in 
western Canada is much larger--estimated at 15,089 to 18,967 
individuals (COSEWIC 2003, p. 22). Wolverine population size in Alaska 
is unknown; however, the average annual harvest consistently exceeds 
500 individuals, and the population does not appear to be in decline 
based on trapper reports and the assessments of State wildlife managers 
(ADF&G 2004, entire). If the population is truly not declining, it is 
likely to number over 8,000 individuals, calculated using demographic 
data in Lofroth and Ott (2007, pp. 2196-2198), and assuming sustainable 
annual harvest of 6 percent (if 500 represents 6 percent of the 
population, total population equals 8,333). Wolverine populations 
number 2,089 to 3,567 in British Columbia and 1,500 to 2,000 in Alberta 
(COSEWIC 2003, p. 22), the two provinces immediately adjacent to the 
contiguous U.S. population. Small populations, such as the contiguous 
U.S. population, face higher extinction risk than large ones such as 
the Canada and Alaska population (Pimm et al. 1988, p. 762).

Effective Population Size

    Population ecologists use the concept of a population's 
``effective'' size as a measure of the proportion of the actual 
population that contributes to future generations (for a review of 
effective population size, see Schwartz et al. 1998, entire). Effective 
population size may be less than actual population size if the 
population has any of the following characteristics: (1) Unequal sex 
ratio, (2) individuals have a disproportionate probability of 
contributing offspring to the next generation, (3) population size

[[Page 12937]]

fluctuates over time, and (4) generations overlap such that individuals 
may reproduce in more than one generation. Effective population size is 
important because it determines rates of loss of genetic variation, 
fixation of deleterious alleles, and the rate of inbreeding. 
Populations with small effective population sizes show reductions in 
population growth rates and increases in extinction probabilities 
(Leberg 1990, p. 194; Jimenez et al. 1994, pp. 272-273; Newman and 
Pilson 1997, p. 360; Saccheri et al. 1998, p. 492; Reed and Bryant 
2000, p. 11; Schwartz and Mills 2005, p. 419; Hogg et al. 2006, pp. 
1495, 1498; Allendorf and Luikart 2007, pp. 338-342). Franklin (1980, 
as cited in Allendorf and Luikart 2007, p. 359) proposed an empirically 
based rule suggesting that the short-term effective population size 
should not be less than 50, and the long-term effective population size 
should not be less than 500 (for appropriate use of this rule and its 
limitations, see Allendorf and Luikart 2007, pp. 359-360). There are 
two main ways to estimate the effective population size of populations: 
demographic and genetic. Demographically-based methods incorporate life 
history parameters, such as unequal sex ratios, fluctuations in 
population size over time, and variance in reproductive success, into 
abundance and demographic models of a species. Genetically-based 
methods use multi-locus genetic data to estimate an effective 
population size (Tallmon et al. 2004, p. 979; Waples 2006, pp. 171-178; 
Tallmon et al. 2007, entire).
    Effective population for wolverines in the Rocky Mountains averaged 
39 (Schwartz 2007, entire). This effective population size is 
exceptionally low (Schwartz 2007, entire), and is below what is 
required for short-term maintenance of genetic diversity.
    The concern with the low effective population size is highlighted 
by recent research determining that at least 400 breeding pairs would 
be necessary to sustain the long-term genetic viability of the 
contiguous U.S. wolverine population (Cegelski et al. 2006, p. 197). 
However, the entire population is estimated to consist of only 500 
individuals (Inman 2007a, entire), with a substantial number of them 
being nonbreeding subadults. Furthermore, the contiguous U.S. 
population appears to be split into at least five smaller 
subpopulations (North Cascades, Crazybelts, Idaho, Greater Yellowstone 
Area, and northern Montana) which are semi-isolated from each other, 
meaning that genetic exchange does not occur frequently enough to 
prevent genetic drift and loss of genetic diversity (Cegelski et al. 
2006, p. 206).
    Genetic studies have highlighted the essential role that genetic 
exchange plays in maintaining genetic diversity in small wolverine 
populations. Genetic drift has occurred in the remaining populations in 
the contiguous United States where wolverines contain four of nine 
haplotypes found in Canadian populations (Kyle and Strobeck 2001, p. 
343; Cegelski et al. 2003, pp. 2914-2915; Cegelski et al. 2006, p. 208; 
Schwartz et al. 2007, p. 2176). The reduced number of haplotypes 
indicates not only that genetic drift is occurring, but also that there 
is some level of genetic separation; if these populations were freely 
interbreeding, they would share more haplotypes (Cegelski et al. 2006, 
p. 205). The reduction of haplotypes is likely a result of the 
fragmented nature of wolverine habitat in the United States and is 
consistent with an emerging pattern of reduced genetic variation at the 
southern edge of the range documented in a suite of boreal forest 
carnivores (Schwartz et al. 2007, p. 2177). As stated previously, the 
low effective population size and accompanying reduction in genetic 
diversity is a concern because populations with low genetic diversity 
are more vulnerable to extinction.
    No effective population size estimate exists for populations in 
Canada or Alaska. However, none of the Canadian or Alaskan populations 
tested show signs of genetic drift or inbreeding (Kyle and Strobeck 
2001, p. 343; Cegelski et al. 2006, p. 209), and all Canadian and 
Alaskan populations contain higher genetic variation than the U.S. 
northern Rocky Mountain populations (Kyle and Strobeck 2001, p. 341). 
In addition, because of the large and contiguous nature of the 
populations (based on habitat contiguity and genetic similarity, see 
``Habitat Availability and Connectivity'' below) (Kyle and Strobeck 
2002, p. 1146; Cegelski et al. 2006, p. 209), and the relatively high 
genetic diversity in Canada and Alaska, we conclude that the effective 
population size is large enough to not be a cause for conservation 
concern. This information indicates that the populations in Alaska and 
Canada are less vulnerable to extinction pressures associated with a 
low effective population size.
    The small effective population size in the contiguous U.S. 
wolverine population has led to inbreeding and consequent loss of 
genetic diversity (Cegelski et al. 2006, p. 208). Over time, if the 
current effective population size remains stable, the population will 
be at risk of extinction due to inbreeding depression or stochastic 
demographic effects (Frankham 1995, p. 795). The small effective 
population size in the contiguous United States contrasts with the 
situation in Canada and Alaska where wolverines are relatively abundant 
and exist in habitats with a high level of connectivity (COSEWIC 2003, 
p. 8; Slough 2007, p. 78). Due to the lack of inbreeding reported for 
these populations, it is likely that effective population sizes are 
much larger than in the contiguous United States. Although these 
differences in biological conservation status between the United States 
and Canadian wolverine populations exist, they are not significant in 
light of section 4(a)(1)(D).

Habitat Availability and Connectivity

    Wolverine habitat in the contiguous United States consists of 
small, isolated ``islands'' of high-elevation, alpine habitats 
containing sufficient depth of snow during the denning period, 
separated from each other by low valleys of unsuitable habitats 
(Copeland 2007, Map 1). The large distances between suitable wolverine 
habitats result in wolverines existing in an archipelago of semi-
isolated, suitable habitats near mountain tops, surrounded by a sea of 
unsuitable habitats. Wolverines occupy habitat in a high-elevation band 
from 2,100 m to 2,600 m (6,888 ft to 8,528 ft) in the mountains of the 
lower 48 States. The intervening valleys in this area range from 975 m 
to 1,500 m (3,198 ft to 4,920 ft), and are unsuitable for long-term 
wolverine habitat because they do not have the snow conditions or other 
habitat features required by wolverines (Aubry et al. 2007, pp. 2151-
2153).
    The low population densities and reduced genetic diversity of 
wolverines in the contiguous United States means that, to avoid further 
inbreeding or local extirpation due to demographic stochasticity, 
regular exchange of individual wolverines between islands of habitat 
must occur. Intermountain valleys are increasingly the sites of human 
residential and commercial developments and transportation corridors, 
and represent semi-permeable barriers to wolverines. Although crossings 
of valleys, primarily by males (e.g., Packila et al. 2007, Fig. 2, 3), 
have been documented, these crossings are not common, and movements 
within valleys occur less frequently than movements in suitable 
wolverine habitats (Packila et al. 2007, p. 110).
    Wolverine populations in the Canadian Rockies also exist on habitat 
islands, but the islands are much larger (Copeland 2007, p. 24) and 
host larger populations so that exchange of

[[Page 12938]]

individuals is likely to be less critical for short-term maintenance of 
genetic diversity and demographic stability. Farther north into Canada 
and Alaska, the climate becomes progressively colder and persistent 
spring snow and Hudsonian/arctic/sub-arctic habitat associations occur 
progressively lower on mountain slopes, until near the Arctic Circle 
where these conditions are found at sea level. Wolverines track these 
latitudinal and elevation gradients by inhabiting progressively lower 
elevations in northern Canada and Alaska until valley bottom habitats 
become suitable habitat and wolverines exist over large expanses of 
contiguous habitat in well-connected populations (COSEWIC 2003, pp. 7-
8). In the far north of Canada, wolverine habitat extends into low-
elevation valleys and the vast expanses of low-elevation boreal forest 
and tundra. Although these differences in biological conservation 
status between the United States and Canadian wolverine populations 
exist, they are not significant in light of section 4(a)(1)(D).
    In the contiguous United States, wolverines must cross unsuitable 
habitats to achieve connectivity among subpopulations, which is 
required to avert further genetic drift and continued loss of genetic 
diversity (Cegelski et al. 2006, p. 208; Copeland 2007, entire; Brock 
et al. 2007, pp. 36-53). The highly fragmented nature of the habitat in 
the contiguous United States contributes to the low effective 
population size for wolverines in this area by dividing the population 
among semi-isolated subpopulations, making the continued persistence of 
the population pre