If wolverines have a strategy, it’s this: Go hard, and high, and steep, and never back down, not even from the biggest grizzly, and least of all from a mountain. Climb everything: trees, cliffs, avalanche chutes, summits. Eat everybody: alive, dead, long-dead, moose, mouse, fox, frog, its still warm heart or frozen bones.
Doug Chadwick, The Wolverine Way
The wolverine is one of the rarest mammals in the North America, estimated to number between 250-300 animals in the continental US in the western Montana, central and northern Idaho, northwestern Wyoming, north-central Washington and northeastern Oregon. The life history characteristics of wolverine make it vulnerable to population impacts, including an extremely low birthrate (averaging only 1 kit per female every other year), very low density populations (0.3 – 6.2 wolverine/1000km2) and an estimated effective population size of 35 for Idaho, Montana and Wyoming.
In February 2013, the U.S. Fish and Wildlife Service proposed to list the species as ‘Threatened’ under the Endangered Species Act (ESA). The USFWS publication provides extensive information on the ecology and known current status of the species and identifies some specific threats to wolverine persistence with the potential impacts of climate-related changes to snowpack and availability of denning of significant concern. This recommendation is currently under review and will go before a special panel in 2014 to determine status of the species under the ESA.
Wolverines occupy large home ranges, with males covering as much as 500 mi2 and female home ranges typically 200-300mi2. Wolverines remain active throughout the winter, traveling extensively across their home ranges in search of carrion that is their primary winter food source. In late February, pregnant female wolverines choose areas with deep snow such as north-facing slopes to dig tunnels down to jumbled talus boulders and fallen logs, creating insulated and safe havens for their 1-3 young. They maintain these snow-based dens through approximately mid-May; this dependence upon snow for denning and reproduction is one of the reasons that the USFWS proposes to list the wolverine under the Endangered Species Act. The loss of wolverine habitat from climate change has been predicted based on the modeled loss of spring (mid-May) snow due to temperature and precipitation changes. The snowpack likely also serves other important functions including preservation of carcasses or cached meat.
The rugged and remote habitats of the wolverine were naturally inhospitable to people and these areas were historically largely undisturbed by humans in the winter months. In many areas, wolverine habitats are no longer inaccessible to humans for winter activities. The growing popularity of winter backcountry recreation combined with advanced snowmobile technology and availability of other mechanized access options such as tracked vehicles (cat-skiing) and helicopters has resulted in winter recreation expanding across previously undisturbed and unreachable public lands.
The potential effects of winter recreation on wolverine reproduction, behavior, habitat use and populations are unknown but there is concern regarding the effects of winter recreation on wolverine, particularly in areas favored by females for reproductive denning. Currently, there is little scientific foundation for management of winter recreation for wolverine persistence and accounts of wolverine responses to human disturbance are primarily anecdotal and conflicting. Given the potentially vulnerable status of the species and the potential decision to list it under the ESA, there is increasing need and interest in developing a scientifically robust understanding of wolverine responses that can provide insights into approaches to management that ensure both winter recreation and wolverine populations may be sustained.
The goal of the Wolverine – Winter Recreation Study is to identify and evaluate wolverine responses to winter recreation. We have developed a research effort that is uniquely collaborative across federal and state agencies, non-government organizations, winter recreationists and local businesses. This collaborative approach to the research is critical not only to the success of data collection efforts but also to build opportunities for collaborative and creative problem solving when research-based management actions are considered.
1) To increase the science-based understanding of the effects of winter recreation on wolverine populations through examining wolverine behaviors, habitat use and reproductive efforts within landscapes supporting a diversity of winter recreation activities;
2) To provide science-based information to guide public land management for the sustainability of both winter recreation and wolverine.
Project Approach: Data are collected on wolverines by live-trapping and fitting Global Positioning System (GPS) collars on animals. Simultaneously, winter recreationists are asked to carry small GPS units that provide the path they have taken. The participation of winter recreationists is voluntary and anonymous, and the overwhelming majority of recreationists approached have participated.
Project Progress: Developing a sound, empirical understanding of the relationship between the wolverine and winter recreation requires considerable effort. The project is currently in its 5th field season and we are beginning to acquire valuable results. Still, the low number of wolverines found in any one area challenges the project, forcing a study design that requires either multiple study areas run simultaneously or moving to new study areas every few years to meet sample size requirements. To date, we have completed 2-3 years of work in 3 different study areas across the Boise, Payette and Sawtooth National Forests in central Idaho. Over the course of the effort, we have instrumented 18 different individual wolverines over the 4 years and collected over 4000 GPS tracks from volunteer recreationists.
In this 5th winter field season, we have initiated work in the western Yellowstone region in 2 new study areas: the Teton Mountains of Idaho and Wyoming and the Centennial and Henry Mountains of Idaho and Montana. To date, we have captured 2 wolverines in our western Yellowstone study areas and we continue to maintain traps as we also seek volunteer recreationists to carry GPS units in these areas. As in other study areas, the recreation community in our new sites have been cooperative and willing to help – thank you! In addition, we are undertaking a 4th year of trapping and monitoring wolverines on the Payette and Boise National Forests while monitoring winter recreation in these longer term study areas. We currently have 4 wolverines collared on the Payette, of which 3 are animals we have known from previous years. As in the western Yellowstone, our efforts are on-going on the Payette and Boise National Forests. Check back for updates on the research.
Please download the reports and progress updates for additional information on the project.
Project Partnerships: The project is a partnership with the Payette, Boise, Sawtooth, Caribou-Targhee and Bridger-Teton National Forests, Idaho Fish and Game, Wyoming Game and Fish Department, Grand Targhee National Park, the Idaho Snowmobile Association and a number of additional partners including ski resort and heliskiing interests. The project is led by the Forest Service’s Rocky Mountain Research Station (Dr. John Squires) and Round River Conservation Studies (Dr. Kimberly Heinemeyer). The project uses the resources of all partners to combine an objective, science-based investigation with extensive community involvement and an information and education campaign.