Reappearing and Disappearing Wolverines
I live in California and in 2008, I was excited to read about a recent sighting of a wolverine on timber lands in Tahoe, California. This was reported as the first sighting in California in 80 years! It was quickly revealed through DNA testing of scat and hair samples that the wolverine was not a descendant of the California subpopulation, long since extinct, but rather appeared to be a migrant from the Northern Rockies. Who knew how he got there? A similar story recently ran about a new arrival showing up in Colorado, the first sighting since 1919. In this case the individual had been tracked for the entirety of his 500-mile journey from Wyoming. These stories of wolverine travel made me wonder whether animals were surviving and moving around the landscape more easily than our theories would suggest.
But things may not be looking so good for the wolverine after all. A new study in the Journal of Population Ecology reports that with declining snow pack since 1970, wolverines across Canada are declining in numbers. Where snowpack has declined the most, so have the wolverines.
At this point, you might be wondering why I am so excited about wolverines at all. Well, the fact is wolverines are cool. They’re big, tough, mean weasels that legend has battling grizzlies for meals, ripping their way out of the most secure traps, and living in and migrating through the deepest of snows. Interestingly, the authors of this study suggest that a lack of snow due to warming temperatures over the last four decades may be decreasing the abundance of food. This is because wolverines, and many other carnivores, survive in part by feeding on ungulates that perish in harsh winters, like caribou, elk or deer.
If the winter is mild, more caribou survive, which means less food for wolverines, and other carrion scavengers like bears and eagles. A 2005 study showed how the re-introduction of wolves in Yellowstone buffers the impacts of climate warming on carrion scavengers. Scavengers steal from wolf kills. In areas without wolves, fewer things kill ungulates—mainly cold weather and deep snowpack. So with less cold and less snow, there is less food for scavengers.
Across the board, declining snow pack is emerging as one of clearest, earliest ways that climate warming is impacting humans, other animals and ecosystems in the United States and elsewhere. Other examples include drier forests and increased wildfires (see Washington: Warming and Wildfires), decrease of cold water flow to trout streams (see Montana: Trout and Drought), and a decrease in agricultural and urban water supplies in areas feed by mountain runoff, such as California.