Yellowstone Wolverine Study Completed
A final report was just released from a study of wolverines in the eastern portion of the Greater Yellowstone area (not to be confused with a complementary study of wolverines in the western GYA by Wildlife Conservation Society that is still ongoing). The eastern GYA study documented the movements of seven wolverines from 2005 - 2009. Some of its key findings include: (1) wolverines are even rarer than expected in Greater Yellowstone, with many areas of suitable habitat vacant; and (2) Yellowstone’s wolverines have a low reproduction rate, large home ranges, and similar survival rates compared to wolverines elsewhere in the western U.S. The researchers also pioneered a helicopter-based survey method that reliably mapped wolverine distribution across their >10,000 sq. mi. survey area. The portion of the Absaroka Range north and east of Gardiner, Montana and the Thoroughfare region south and east of Yellowstone were the most important areas for wolverines in this study (yet wolverines use other areas of the GYA according to studies by Wildlife Conservation Society and Wild Things Unlimited, for example).
This eastern GYA study drives home just how hard it is to study this rare and elusive alpine carnivore. The researchers logged a total of 5,248 trap nights, which is equivalent in effort to putting out a single trap every day, all year long, for more than fourteen years! This amazing amount of effort yielded just seven captures of four unique individual wolverines. Again, if put in terms of a single trap open and maintained yearlong, this is equivalent to trapping one wolverine every two years, and one unique wolverine every 3 ½ years! Regardless of one’s opinions on Montana’s legal trapping season for wolverines, the loss of one of these precious research animals to a Montana trapper was clearly unfortunate.
One take-home message from this study is that the current vacancy of large portions of suitable wolverine habitat in Greater Yellowstone deserves more study. Even with this “partial” occupancy, the GYA remains an important refuge for wolverines because of its large contiguous expanse of wolverine habitat, which may become still more important due to the projected decline and fragmentation of these areas due to global warming.
Link to the Northern Rockies Conservation Cooperative webpage where you can download a pdf copy of the final report.
Link to the Yellowstone Park Foundation, the principal funder of this study.