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Endangered and Threatened Wildlife and Plants; 90-day Finding for a Petition To List as Endangered or Threatened Wolverine in the Contiguous United States

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Fish and Wildlife Service, Interior.


Notice of 90-day petition finding.


We, the U.S. Fish and Wildlife Service (Service), announce a 90-day finding for a petition to list the wolverine (Gulo gulo luscus) in the contiguous United States as threatened or endangered under the Endangered Species Act of 1973, as amended. We find the petition and additional information available in our files did not present substantial scientific or commercial information indicating that listing the wolverine in the contiguous United States may be warranted. We will not be initiating a further status review in response to this petition. We ask the public to submit to us any new information that becomes available concerning the status of or threats to this species. This information will help us monitor and encourage the conservation of this species.


The finding announced in this document was made on October 15, 2003. You may submit new information concerning this species for our consideration at any time.


Data, information, comments, or questions concerning this petition should be submitted to the Montana Ecological Services Field Office, U.S. Fish and Wildlife Service, 100 North Park Avenue, Suite 320, Helena, Montana 59601. The petition, finding, and supporting information are available for public inspection, by appointment, during normal business hours, at the above address. Submit new information, materials, comments, or questions concerning this species to the Service at the above address.

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Lori Nordstrom, at the address given in the ADDRESSES section (telephone (406) 449-5225; facsimile (406) 449-5339; electronic mail

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Section 4(b)(3)(A) of the Endangered Species Act of 1973, as amended (Act) (16 U.S.C. 1531 et seq.), requires that we make a finding on whether a petition to list, delist, or reclassify a species presents substantial scientific or commercial information to indicate that the petitioned action may be warranted. We are to base this finding on all information available to us at the time we make the finding. To the maximum extent practicable, we must make this finding within 90 days of receiving the petition and publish a notice of the finding promptly in the Federal Register. Our standard for substantial information with regard to a 90-day petition finding is “that amount of information that would lead a reasonable person to believe that the measure proposed in the petition may be warranted” (50 CFR 424.14(b)). If the finding is that substantial information was presented, we are required to promptly begin a review of the status of the species, if one has not already been initiated, under our internal candidate assessment process.

On July 14, 2000, we received a 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. The petition requests that we list the wolverine within the contiguous United States as a threatened or endangered species and designate critical habitat for the species.

On April 19, 1995, we published a notice of our finding that a previous petition submitted by the Predator Project (now named the Predator Conservation Alliance) and Biodiversity Legal Foundation to list the wolverine in the contiguous United States did not provide substantial information indicating that listing the wolverine in the contiguous United States may be warranted (60 FR 19567).

Since 1995, little new information on wolverine biology, distribution, habitat requirements, or possible threats has been published. The species is still considered one of the least understood medium carnivores. The only new research completed for the contiguous United States is that on wolverine ecology in Idaho (Copeland 1996; Magoun and Copeland 1998; Edelman and Copeland 1999), and a genetic study (Cegelski 2002). Banci (1994) is a compilation of existing wolverine information plus suggestions for research or management considerations. Additional research on wolverine ecology, current and historic Start Printed Page 60113distribution, population demographics, and habitat requirements is underway that should provide better information with which to understand the wolverine (Inman et al. 2002; J. Squires, Rocky Mountain Research Station, pers. comm. 2003; U.S. Forest Service, in litt. 2002).

The wolverine has a holarctic distribution. The currently accepted taxonomy classifies wolverines worldwide as a single species, Gulo gulo. Old and New World wolverines are divided into separate subspecies. Wolverines in the contiguous United States are a part of the New World subspecies, G. g. luscus (Kurten and Rausch 1959; Pasitschniak-Arts and Lariviere 1995). We follow this currently accepted taxonomic treatment, although in the past we recognized other taxonomic classifications for wolverine (September 18, 1985; 50 FR 37958).

The wolverine is the largest terrestrial member of the family Mustelidae, with adult males weighing 12 to 18 kilograms (kg) (26 to 40 pounds (lb)) and adult females weighing 8 to 12 kg (17 to 26 lb) (Banci 1994). It resembles a small bear with a bushy tail. It has a round, broad head; short, rounded ears; and small eyes. There are five toes on each foot, with curved and semiretractile claws used for digging and climbing (Banci 1994).

Wolverines are opportunistic feeders, consuming 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; Wilson 1982; Hash 1987; Banci 1994). Wolverines have an excellent sense of smell, enabling them to find food beneath deep snow (Hornocker and Hash 1981).

Breeding generally occurs from late spring to early fall. Females undergo delayed implantation until the following winter to spring, when active gestation lasts from 30 to 40 days (Rausch and Pearson 1972). Litters are born between February and April, containing one to five kits, with two to three kits being the most common number (Hash 1987). Reproductive dens in Idaho were located in snow-covered boulder talus in subalpine cirque basins (Copeland 1996; Magoun and Copeland 1998).

Wolverines have large spatial requirements; the availability and distribution of food is likely the primary factor in determining wolverine movements and home range (Hornocker and Hash 1981; Banci 1994). Wolverines can travel long distances over rough terrain and deep snow, with adult males generally covering greater distances than females (Hornocker and Hash 1981; Banci 1994). Home ranges of wolverines are generally extremely large, but vary greatly depending on availability of food, gender, age, and differences in habitat. Home ranges of adult wolverines range from less than 100 square kilometers (km2) to over 900 km2 (38.5 square miles (mi2) to 348 mi2) (Banci 1994). Copeland (1996) found that annual home ranges of resident adult females in central Idaho averaged 384 km2 (148 mi2), while the annual home ranges of resident adult males averaged 1,522 km2 (588 mi2).

In North America, wolverines occur within a wide variety of habitats, primarily boreal forests, tundra, and western mountains throughout Alaska and Canada, with the southern portion of the wolverine range extending into the contiguous United States (Wilson 1982; Hash 1987; Banci 1994; Pasitschniak-Arts and Lariviere 1995). The specific range of the wolverine in the contiguous United States is not well understood, preventing us from accurately delineating the historic or current range using the information available to us at this time. The petitioners state that wolverine were trapped to near or complete extinction throughout its former range in the western states in the early 20th century. However, information from state and Federal wildife experts suggest the species has reoccupied its western range in recent years .

The current range in the contiguous United States is believed to include Idaho, Montana, Oregon, Washington, Wyoming, and possibly California (Banci 1994). Wolverines have recently been documented in Idaho (Copeland 1996), Montana (Inman et al. 2002; B. Giddings, Montana Department of Fish, Wildlife and Parks, pers. comm. 2003; J. Squires, pers. comm. 2003), Washington (Washington Department of Fish and Wildlife, in litt. 1998) and Wyoming (Inman et al. 2002). However, we do not know the extent of the historic range. Wolverines reportedly occurred in a number of other States historically, including Colorado, Maine, Michigan, Minnesota, New Hampshire, New York, North Dakota, Utah, and Wisconsin, suggesting a much wider range historically (Wilson 1982; Hash 1987; Pasitschniak-Arts and Lariviere 1995). The petitioners generally stated that wolverines have been extirpated from States in the Great Lakes, High Plains, and Northeast. But, as we found in 1995, the petition provides no information to confirm the reliability of these historic reports. Furthermore, without a better understanding of the habitat requirements of the wolverine, we cannot ascertain whether habitats in many States were capable of supporting wolverines historically, which would help us determine their historic range.

The wolverine naturally occurs in low densities (Hornocker and Hash 1981; Hash 1987; Banci 1994). Petitioners state that (1) wolverine range and numbers have decreased dramatically since Pre-Columbian times due to human activities and developments, and (2) wolverines currently number fewer than 1,000 animals across the lower 48 states.

However, Hornaker and Hash (1981) asserted stable populations on their study area in Montana, with high dispersal patterns maintaining the stability, rebounding from near extinction in Montana from 1920-1940 (Newby and Wright 1955).

Recent surveys in the west indicate that wolverines appear to be distributed in the montane regions of Idaho, Montana, Washington and Wyoming (Copeland 1996; Washington Department of Wildlife 1998; Inman et al. 2002; Giddings pers. comm. 2003; Squires pers. comm. 2003). So, despite scant population and abundance information, there are reports and surveys to suggest that wolverine may not be likely to become threatened in the foreseeable future in the lower 48 states. Wolverines are difficult and expensive to study and are rarely observed, so a lack of sightings does not necessarily mean that wolverines are not present (Banci 1994). There have been few, if any, surveys of wolverines in the contiguous United States that were designed to estimate population size at even a local scale. As a result, it is scientifically unsound to make an estimate of wolverine population size using currently available information, particularly for the entire contiguous United States.

Despite the limitations of available wolverine data, the petitioners provided their own estimation of the size of the wolverine population for the contiguous United States. They arrived at their estimate apparently by creating their own measure of local wolverine densities and extrapolating across what they determined to be the current range of wolverine. Given the lack of data on wolverine population densities even at a local level, using such preliminary information to estimate population size is inappropriate.

Based on what we know about wolverines (i.e., they are found in low densities and have large home ranges), we expect wolverine population sizes to appear low when compared to other species with different population dynamics. Start Printed Page 60114

At this time, this lack of information prevents us from determining whether wolverines in the contiguous United States constitute a “distinct population segment” (DPS), which would make them eligible to be listed under the Act. Our Distinct Vertebrate Population Policy published in 1996 (61 FR 4722) specifies that we are to use two elements to assess whether a population segment under consideration for listing may be recognized as a DPS—(1) The population segment's discreteness from the remainder of the taxon to which it belongs; and (2) the significance of the population segment to the taxon to which it belongs. A taxon is the taxonomic group of animals to which the population belongs—in this case the subspecies G. g. luscus.

Under section 4(a) of the Act, we may list a species, subspecies, or DPS of vertebrate on the basis of any of five factors—(A) Destruction, modification, or curtailment of habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) inadequacy of existing regulatory mechanisms; and (E) other man-made or natural factors affecting its continued existence. The petition asserts that wolverines are subject to threats primarily under Factors A, B, and D. The Service used information provided by the petitioners and available in its files to address these factors as follows.

Under Factor A, the petition asserts wolverines have been impacted by the loss of roadless areas due to logging practices. However, Banci (1994) stated that “the impacts of logging and associated activities on wolverines and wolverine habitat can only be surmised.” Wolverines are generally associated with remote areas and require large expanses of land as refugia from human activities, especially during denning. Hornocker and Hash (1981) mentioned that wilderness or remote areas, with limited human activity, appear to be necessary for viable wolverine populations; however, they found no difference in wolverine densities between the wilderness and non-wilderness areas of the study, nor were there differences in their movement, habitat use, or behavior. The non-wilderness portion of the study area was mainly used by humans for logging and recreation (Hornocker and Hash 1981). Copeland (1996) also found wolverines in areas that were currently being logged.

The petitioners cite human disturbance of denning habitat, particularly snowmobile activity, as a threat to wolverines. New research indicates wolverines are sensitive to disturbance when they are denning. In two instances female wolverines moved their kits and abandoned their dens upon encountering researchers; the kits survived the move (Copeland 1996; Magoun and Copeland 1998). Copeland (1996) concluded that protection of natal denning habitat is important to the persistence of wolverine in Idaho. The petitioners provide general information that snowmobile activity is increasing and could expand into regions where wolverines occur, but there is a lack of information to determine the degree to which snowmobile activity may be increasing within wolverine denning habitat or what impact it may be having on wolverine populations.

The petitioners cite landscape fragmentation due to transportation corridors and associated developments as a threat to wolverines. The Service agrees that development is increasing throughout the contiguous United States; however, the level to which landscape fragmentation may be affecting wolverines and their ability to meet their habitat requirements is unknown because little is known about wolverine range and movement. Genetic differentiation among wolverine populations in Idaho, Montana, and Wyoming has been documented, suggesting some level of isolation among these populations possibly as a result of human-caused habitat fragmentation (Cegelski 2002). However, given the lack of understanding of wolverine habitat regarding factors affecting dispersal, all knowledge of possible causes of the genetic differences among these populations is speculative at this time.

Based on the foregoing discussion, we find that the petition does not present substantial information to indicate that habitat impacts threaten the continued existence of the wolverine in the contiguous United States.

Under Factor B, the petitioners cite trapping as a threat to wolverines in the contiguous United States. Over much of the wolverine distribution, trapping has been a primary factor in wolverine mortality (Banci 1994). Trapping is believed to have played a role in an apparent historic decline of wolverine in North America in the late 19th and early 20th centuries (Hash 1987). Today, within the contiguous United States, the only State where wolverine trapping is legal is Montana. Although this trapping season may be detrimental to local wolverine populations, it is not known whether trapping in Montana alone threatens the continued existence of the wolverine population in the contiguous United States. The petitioners also suggest incidental trapping and poisoning of wolverines as a threat, but provide no supporting information for this assertion.

Under Factor C, the petitioners mention predation by other large predators (e.g., wolves) as a source of wolverine mortality. However, this is a natural event and is not considered a threat to the persistence of wolverines in the contiguous United States. There is no information on diseases that may impact wolverine populations.

Under Factor D, the petition cites a lack of Federal protection as a threat to wolverines because a major part of the wolverine's range falls upon lands managed by the U.S. Forest Service (USFS). The USFS has designated wolverines as a “sensitive species” in Regions 1, 2, 4, and 6, and “proposed sensitive” in Region 5. The Bureau of Land Management has determined wolverine to be “sensetive.” Conservation efforts are planned for various Federal lands and the upcoming USFS report will help improve the scant information currently available.

It is not possible at this time to determine whether management actions threaten the continued existence of wolverines in the contiguous United States. The USFS is leading a cooperative effort with other Federal agencies, States, and Tribes to conduct research and studies for the development of a scientifically-based strategy for conserving wolverines (USFS, in litt. 2002). Initial work is focused on summarizing historic observation data in an effort to delineate historic and current range and habitat relationships. Ongoing research and surveys will examine wolverine ecology, population demographics, distribution, and habitat use with an emphasis on broad-scale movements and population connectivity.

Finally, under Factor E, the petitioners generally cite the wolverine's low reproductive rate, sensitivity during denning, and need for large areas of unfragmented range and habitat as factors making the wolverine vulnerable to extinction. These natural life history characteristics distinguish the wolverine from other medium-sized carnivores. However, reports and surveys of wolverine from Idaho, Montana, Wyoming, and Washington suggest some stability. It is important to collect more information on wolverine occurrence, distribution, and habitat requirements in addition to developing management measures to conserve the species.

In summary, we find that there is insufficient information in the petition or in our files on wolverine habitat requirements or range to determine Start Printed Page 60115whether destruction or modification of wolverine habitat and range is occurring to the extent that it affects the status of the wolverine. We also found insufficient evidence to indicate that the wolverine trapping season in Montana or incidental trapping or poisoning poses a threat to the wolverine population in the contiguous United States. The paucity of data on wolverine life history and habitat requirements leads us to conclude that there is insufficient evidence to determine if land and wildlife managers are failing to conserve wolverines. There also is insufficient data to determine whether human disturbance is negatively impacting wolverine populations on a scale that impacts the status of the species.

We anticipate that ongoing studies of wolverines and, in particular, a scientific assessment of wolverines in the contiguous United States being led by the USFS that should be available in 2004, will improve our understanding of this species in the contiguous United States.

We have reviewed the petition, information submitted by the petitioners, other pertinent literature, and information available in Service files. We find the petition does not present substantial information to indicate that petitioned action may be warranted. This finding is based on insufficient information to—(1) Determine whether the wolverine in the contiguous United States constitutes a DPS under the Act, (2) understand possible threats to the wolverine, or (3) determine whether or not the species is declining in the contiguous United States.

References Cited: A complete list of all references cited herein is available upon request from the Montana Field Office (see ADDRESSES).

Author: The primary authors of this document are Katrina Dixon and Lori Nordstrom, Montana Field Office, Helena, Montana.

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Authority: The authority for this action is the Endangered Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).

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Dated: October 15, 2003.

Marshall P. Jones, Jr.,

Director, Fish and Wildlife Service.

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[FR Doc. 03-26453 Filed 10-20-03; 8:45 am]