(Map may reflect historical as well as recent sightings)
The North American Wolverine (Gulo gulo luscus) became a federal candidate species December 14, 2010. On February 1, 2013, the U.S. Fish and Wildlife Service announced a proposal to list the wolverine as a threatened species under the Endangered Species Act.
Historic Status and Current Trends
In the 19th century, wolverines were found throughout the Cascade Mountains, Rocky Mountains, Central Great Plains, Great Lakes, Upper Midwest, and the northeast United States. Currently, the U.S. population is estimated at 250 to 300 individuals, mostly concentrated in Northern Rocky Mountain Range, with some occurring in the Pacific Cascade Region.
By 1936, the wolverine was thought to have been extirpated from Oregon. Based on records from ODFW, at least one report of a wolverine was documented for each decade from the 1960s to the 1990s, including locations in Linn, Harney, Wheeler, and Grant counties, respectively. More recently, a two-year monitoring project by wolverine expert Audrey Magoun has verified presence of at least three individual wolverines in the Eagle Cap Wilderness of northeastern Oregon (Wallowa, Baker and Union counties), an area with no prior documentation of wolverine presence. Two of the three wolverines detected during the first field season were confirmed to be males and the third was tentatively identified as a male, and therefore, no evidence of reproduction was available In December 2012, wolverine tracks were found in the Sled Springs area NW of Enterprise. This is in the same area where they are finding new wolf activity. Efforts are planned to help determine whether wolverines are using the area or if the animal was just passing through. Additionally, a two-year wolverine survey effort by ODFW is underway (September to May, 2012 to 2014) in the northern Cascade Mountain Range of Oregon (Willamette and Deschutes National Forests). Efforts are being concentrated within the Mt. Jefferson, Mt. Washington, and Three Sisters wilderness areas.
Description and Life History
The wolverine is the largest terrestrial member of the weasel family. With its broad head, small eyes, and short, rounded ears, the wolverine resembles a bear with a long, bushy tail. Wolverines have a light face mask and dark, glossy fur that ranges in color from black to cinnamon-brown with light stripes running down both sides of its thick body. Adult males weigh 26 to 40 pounds and adult females weigh 17 to 26 pounds. Short legs and wide feet allow wolverines to travel across deep snow. Curved, semi-retractile claws are used for digging and climbing. Poor eyesight is compensated for by a keen sense of smell which enables the wolverine to find food even when buried deep in the snow. Their diet includes small mammals, birds, insects, and some berries, as well as the carrion of large ungulates.
Relatively little is known about wolverines due to their elusive nature and the remoteness of their habitat. Wolverines of both sexes are territorial. Male territories are larger and may overlap with female territories, but there is no overlap of territories within the sexes. It is thought some males may roam opportunistically as opposed to defending a static territory.
Wolverines are polygamous and mate once per year. Females become reproductively mature at about three years and often give birth each year. Typically, a litter consists of one to two kits though, when food is too scarce, the mother may resorb the embryos. Females will use one natal den in which to give birth and wean the young, and also maintain several alternative den sites in case the natal den is disturbed. Infanticide by male wolverines is a common cause of juvenile mortality. The wolverine is a particularly low-reproducing species with a life expectancy of 10 to 12 years.
Wolverine habitat consists entirely of alpine, arctic, and sub-arctic regions. Snow cover during the spring is essential for females who use deep snow banks for denning throughout the pregnancy and weaning periods. Habitat areas for wolverines are usually isolated and described as “patchy,” often separated by large areas of unsuitable habitat. Almost all wolverine habitat in the contiguous U.S. is federally owned and managed. Suitable wolverine habitat in Oregon is considered to be the high-elevation forests of the Cascade Range, and of the Blue Mountains, Wallowa Mountains, and Ochoco Mountains. There is potential for wolverines from the Rocky Mountain population to enter Oregon from Idaho, Wyoming, or Montana.
Reasons for Decline
The greatest cause of decline of the North American wolverine is habitat loss. In the early 20th century, wolverines were nearly extirpated from the contiguous U.S. Unfortunately, climate warming over the next century is likely to significantly reduce wolverine habitat, to the point where persistence of wolverines in the contiguous U.S., without intervention, is in doubt. Endangered Species Act protection and actions by federal and state agencies in partnership with private landowners and nongovernmental organizations can help protect the wolverine from extinction by increasing its ability to persist in the face of climate change.
In conjunction with the proposed listing, a Draft Recovery Outline for Wolverine is under development. This document will facilitate the eventual creation of the Service’s Wolverine Recovery Plan, a detailed conservation plan that will guide recovery efforts. The state of Oregon, which listed the wolverine as threatened in 1989, has made it illegal to kill or otherwise harm wolverines. Until the Recovery Plan is completed and implemented, the U.S. Fish and Wildlife Service encourages voluntary cooperative conservation efforts and provides technical assistance on designing and implementing conservation actions.
References and Links
Aubry, K.L., K.S. McKelvey, and J.P. Copeland. 2007. Distribution and broadscale habitat associations of the wolverine in the contiguous United States. Journal of Wildlife Management 71:2147–2158.
Banci, V. 1994. Wolverine. Pp. 99–127 in L. F. Ruggiero, K. B. Aubry, S. W. Buskirk, L. J. Lyon, and W. J. Zielinski, editors. The scientific basis for conserving forest carnivores: American marten, fisher, lynx, and wolverine in the western United States. USDA Forest Service Rocky Mountain Forest and Range Experiment Station, General Tech. Report RM-254, Fort Collins, Colorado, USA.
Cegelski, C.C., L.P. Waits, N.J. Anderson, O. Flagstad, C. Strobeck, and C.J. Kyle. 2006. Genetic diversity and population structure of wolverine (Gulo gulo) populations at the southern edge of their current distribution in North America with implications for genetic viability. Conservation Genetics 7:197-211.
Copeland, J.P. 1996. Biology of the wolverine in central Idaho. Thesis, University of Idaho, Moscow, USA.
Copeland, J.P., J.M. Peek, C.R. Groves, W.E. Melquist, K.S. McKelvey, G.W. McDaniel, C.D. Long, and C.E. Harris. 2007. Seasonal habitat association of the wolverine in Central Idaho. Journal of Wildlife Management 71:2201–2212.
Frankham, R. 1995. Inbreeding and extinction: a threshold effect. Conservation Biology 9: 792-799.
Hatler, D.F. 1989. A wolverine management strategy for British Columbia. Wildlife Bulletin B60, British Columbia Ministry of Environment, Victoria, Canada.
Hedmark, E., Persson, J., Segerstro¨m, P., Landa, A. & Ellegren, H. 2007: Paternity and mating system in wolverines Gulo gulo. - Wildl. Biol. 13 (Suppl. 2): 13-30.
Hornocker, M.G., and H.S. Hash. 1981. Ecology of the wolverine in northwestern Montana. Canadian Journal of Zoology 59:1286–1301.
Inman, R.M. 2010. Subject: Re: Email from Robert Inman, Wildlife Conservation Society wolverine scientist. Ennis, Montana (July 23, 2010).
Krebs, J., E. Lofroth, J. Copeland, V. Banci, D. Cooley, H. Golden, A. Magoun, R. Mulders, and B. Shults. 2004. Synthesis of survival rates and causes of mortality in North American wolverines. Journal of Wildlife Management 68(3): 493-502.
Lofroth, E.C., and P.K Ott. 2007. Assessment of the sustainability of wolverine harvest in British Columbia, Canada. Journal of Wildlife Management 71(7):2193-2199.
Magoun, A. J. 1985. Population characteristics, ecology, and management of wolverines in northwestern Alaska. Doctoral Dissertation. University of Alaska, Fairbanks Alaska. 209 pp.
Magoun, A.J., and J.P. Copeland. 1998. Characteristics of wolverine reproductive den sites. Journal of Wildlife Management 62:1313–1320.
Persson, J., A. Landa,R. Andersen, and P. Segerström. 2006. Reproductive characteristics of emale wolverines (Gulo Gulo[authors used capitol G for specific e.]) in Scandinavia. Journal of Mammalogy 87:75–79.
Squires, J.R., J.. Copeland, T.J. Ulizio, M.K. Schwartz, and L.F. Ruggiero. 2007. Sources and patterns of wolverine mortality in western Montana. Journal of Wildlife Management 71:2213-2220.