WOLVERINE REESTABLISHMENT AND CONSERVATION EFFORTS IN THE SIERRA NEVADA
Wolverines are the largest terrestrial member of the weasel family (Mustelidae) and are found in northern latitudes around the world. They reside in remote wilderness regions, persist at very low population densities, and are seldom seen by human visitors. However, wolverines play an important role as scavengers, often feeding on the carcass remains left by larger predators such as wolves, grizzly bears and mountain lions.
The Sierra Nevada mountains and the central Rocky Mountains once supported populations of wolverines, the southern most portion of their range. The high elevations of the Sierra Nevada mountains provided habitat features similar to those supporting wolverines at more northern latitudes. However, the wolverine population in the Sierra Nevada began to decline in the early 20th century, likely due to indiscriminate poisoning of predators, fur trapping, and reduction of predators upon which they depended for carrion. By the 1930s the wolverine population was thought to be down to 15 pairs in the state. Extensive effort to monitor for furbearers (fisher, red fox, martens) over the last two decades failed to detect any wolverines. IWS also conducted a winter wolverine survey in the Sequoia/Kings Canyon national parks, and failed to detect any wolverines. The last confirmed sighting of a wolverine or a wolverine carcass prior to 2008 was 50 years earlier.
In 2008 a wolverine was detected on a trail camera set to monitor American marten. Scat was collected from this individual and DNA extracted for analysis. It was found to be a male that was most closely related to wolverines from Idaho. Researchers believe this individual immigrated from Idaho (or that general area) and established in the area near Truckee, California. It has continued to be detected by cameras in 2009 and 2010, but no other individuals have been observed.
Since 2005, IWS biologists have worked on a proposal to reestablish or augment wolverines in the Sierra Nevada. If sanctioned by state authorities, wolverines will be translocated to California to help restore and conserve the state’s population. The project will be done in collaboration with the Department of Fish and Game, Federal land agencies, and a host of private organizations and land owners.
Wolverines for translocation will be obtained from healthy wild populations in Canada and/or Alaska. After being captured in specially-designed traps, they will undergo veterinary diagnostics to determine that they are free of disease and parasites that are foreign to California carnivores. They will then be transported to a holding facility prior to being released into the wild. The wolverines will be “soft released” into their new environment, first being held on-site in a pen until they have acclimated to the area. All released animals will be equipped with GPS satellite radio collars to allow their movements to be monitored, and supplemental food will be provided to increase survival over their first year.
Depending on the success of the first release efforts, a second release will take place two years later. Modeling suggests that augmenting the population with a second release will significantly increase the probability that the population will remain viable.