The latest of only two field studies of wolverines in the lower-48 (see Hornocker and Hash 1981 for the other one), this is a landmark study. Pasted below are some important excerpts from this paper. Also, visit the website of the author's non-profit Wolverine Foundation for an excellent complilation of information on wolverine status, needs, research... everything you ever wanted to know about Gulo!
(unless nobody knows it, which is very possible with Gulo): http://www.wolverinefoundation.org
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Here is a selection of excerpts from Idaho Department of Fish and Game Researcher Jeff Copeland's Masters Thesis on wolverines in the Sawtooth Mountains of central Idaho. Jeff's study was the fifth of only five field studies of wolverine in all of North America (the only other field study done in the continental U.S.was by Maurice Hornocker and Howard Hash in Montana in 1981). I changed the order of the excerpts and re-organized them a bit, but they are all direct quotes in case folks want to cite them directly. If you are in a hurry, I marked (!) the excerpts that appear to be the most useful, including all of Jeff's "Management Recommendations" that appear at the end.

The study is 138 pages. You can order a photocopy from Idaho Dept. of Fish and Game. Call, write, or email Chuck Harris at the Boise Office (208-334-2920, charris@idfg.state.id.us); they request a donation to the non-game program to cover copying and mailing fees.

Introduction

19 wolverines were captured

1,050 relocations

Management Status

"The State of Idaho lists the wolverine as a Species of Special Concern. The Forest Service and Bureau of Land Management list the wolverine as a Sensitive Species." (p.1)

"Canada harvests about 800 wolverines each year yet still considers it one of its rarest mammals. Wolverine presence in the western United States is well-documented however only Montana manages for a limited harvest." (p.2)

Reproduction

"The reproductive rate for 4 adult females was less than 1 kit/female/year." (p.iv) (0.89 kits/female/year, p.35)

Range sizes and movements

Avg. annual home ranges: 384 km2 for females (SD = 117), 1,582 km2 for males (SD = 488)

"Prior to my study, the upper limit of reported wolverine home range size was under 1,000 km2." (pp.49-68)

"Four male wolverines dispersed at sexual maturity, with 2 emigrating distances greater than 185 km." (p.iv)
Hornocker and Hash (1981) reported a density of 1 [wolverine]/65 km2 in northwest Montana." (p.4)

"Wolverines are capable of traveling over 30 km/day." (p.12)

"Dividing the home range area of the resident adult females by the potential number of residents provides a density estimate of 1 wolverine/90-113 km2. A more conservative estimate may be based on the 1,980 km2 total home range area of the resident male. This produces a density range of 1 wolverine/198-248 km2." (p.32)

Hornocker and Hash (1981) and Quick (1953) reported population density estimates of 1 wolverine/65 km2 in northwest Montana and 1 wolverine/207 km2 in British Columbia, respectively, based on capture and snowtracking data." (p.32)

"Hornocker and Hash (1981) recommended a regional management approach based on movements of their study wolverines outside their study area, although they did not provide movement distances. Magoun (1985) reported a 300 km movement of an unknown age female. Idaho wolverines also traveled extended distances (Table 3.3) with 3 individuals traveling over 200 km in apparent dispersal attempts." (p. 87)

"Dispersal carries a high risk of starvation or predation and data on the fate of dispersing individuals are scarce." (p. 91)

Habitat Requirements

"Females used secluded high elevation cirque basins for natal den sites." (p.iv)

"Females commonly left dependent kits at rendezvous sites comprised of large boulder talus or riparian areas associated with mature overstory and dense timber deadfall." (p. iv)

"Distinct seasonal shifts in elevational use were recorded, with higher elevational talus/rock cover types preferred during summer months, and montane coniferous forest cover types preferred during winter." (p.iv).

! "Central Idaho wolverines appeared highly selective in choice of natal denning and kit rearing habitat... Even with adequate food, wolverines may not be resident without suitable denning habitat." (p.72)

"The denning habitat used by 2 marked females and 1 unmarked female in Idaho was specific to subalpine talus habitats. The availability of talus communities throughout Idaho may define limitations for wolverine reproductive potential." (p.93)

"Natal sites were located in isolated talus slopes that were less than 100 m wide and surrounded by trees, as opposed to the more expansive and exposed talus slopes generally characterizing glacial cirques." (p.94)

"Rendezvous sites.--... Five of the sites [identified] were talus and 5 were coniferous riparian... Riparian sites occurred within lower slope spruce/fir riparian areas... All were characterized by a mesic, dense shrub and regenerating conifer understory associated with multiple layered timber downfall." (p.98)

"Montane coniferous forest types constituted 66.0% of available habitat and accounted for 70.2% of wolverine relocations. There was an inverse relationship between seasonal use of Douglas-fir and lodgepole pine, with Douglas-fir preferred in summer and lodgepole pine favored in winter... Wolverines were located in openings, defined as any break in the canopy resulting in an observable change in the understory composition, on 34% of relocations and were located in burned areas 34 times. Three wolverines were located in logging areas, 1 in a clearcut and 2 near active sales." (p.120).

"Hornocker and Hash (1981) found that 70% of wolverine use in medium to scattered timber... Preference for higher elevation habitats during summer may be related to the availability of prey species or human avoidance while lower elevational forest types commonly associated with wild ungulates likely provide the highest carrion availability." (p.124)

"Montana wolverines were reluctant to cross openings such as clearcuts or burned areas (Hornocker and Hash 1981). Idaho wolverines commonly crossed natural openings and areas with sparse overstory such as burned areas, meadows, or open mountain-tops." (p.125)

Mortality and Trapping Impacts

"Hornocker and Hash (1981) described a wolverine population in northwest Montana as demographically stable although socially dynamic due to periodic population turnover caused by trapping mortality." (p.3)

"Young wolverines may remain close to their natal den for at least 2 years, and appear to be more vulnerable to trapping than older age individuals." (p.34)

"Seven radio-marked wolverines (6 females, one male) died during the study period; 3 from predation, 3 of unknown cause, and 1 research related." (p.44)

"Hornocker and Hash (1981) found no evidence of exclusive home range use and suggested that trapping harvest may have created behavioral instability in the population, allowing inadequate time for establishment of site tenure." (p.75)

Effects of Human Disturbance

! "Females in arctic Alaska remained at a single den until late April or early May and did not appear disturbed by the presence of human observers (Magoun 1985)... Finnoscandian studies [studies from Finland or other Scandinavian countries?] report den abandonment as a common response to human disturbance... Myrberet (1968) mentions 4 instances of den abandonment due to human disturbance and suggests that secondary dens may be less suitable. My data is consistent with this. My first direct contact with denning females did not occur until late April and resulted in immediate den abandonment." (p.93)

! "When viewed in conjunction with potential displacement and disturbance of denning females by winter recreational activities of humans, denning habitat may be a limited and critical component of wolverine habitat." (p.93)

[Great anecdote of a mother wolverine who discovered the researchers' snowshoe tracks near her den, followed them to within 20 m of the researchers, immediately returned to her den and took off in the opposite direction with a kit in her mouth, and returned 30 minutes later to repeat this with her second kit. (pp.96-7)]

Foraging Needs

"Ungulates, both wild and domestic, were the most common food item, representing 45.8% of all occurrences." (p.100)

Management Recommendations

! "Protection of natal denning habitat from human disturbance is critical for the persistence of the wolverine in Idaho. The clear association between wolverine presence and refugia may be strongly linked to a lack of available natal denning habitat outside protected areas... Technological advances in over-snow vehicles and increased interest in winter recreation has likely displaced wolverines from potential denning habitat and will continue to threaten what may be a limited resource." (p.129)

! "Subalpine cirque areas important for natal denning may be made unavailable by winter recreational activities. Conversely, high road densities, timber sales, or housing developments on the fringes of subalpine habitats may reduce potential for winter foraging and kit rearing and increase the probability of human-caused wolverine mortality." (p.130)

! "A close relationship exists between wolverine and ungulate presence. Ungulate carrion is a primary food item, and activities that decrease large mammal populations may negatively affect carrion availability. Excessive hunter harvesting and loss of ungulate wintering areas as well as displacement of ungulate populations due to excessive timber harvest and urbanization may adversely impact wolverines. Ungulate wounding from hunting and livestock losses on public grazing allotments most likely provides a consistent carrion source. Management practices that reduce the presence and opportunity for carrion availability may impact wolverine foraging success." (p.130)

! "Refugia may be most important in providing availability and protection of reproductive denning habitat. Life history requirements of the wolverine are tied to the presence and stability of ecosystems lacking broad scale human influence... Habitat alteration may isolate subpopulations increasing their susceptibility to extinction processes." (p.130)

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