New UW Research Shows Grizzly Diet Shift Hits Elk Herds

New UW research has discovered a change in the diets of grizzly bears which is helping to clarify losses in some migratory elk herds in the greater Yellowstone area.

The University says UW Ph.D. graduate Arthur Middleton teamed up with multiple researchers and has provided evidence that the late trout population in the Yellowstone Lake and other areas around it have lost a plethora of elk calves and that the grizzly are killing them.

Middleton says, “This synthesis suggests that, even in a core wilderness area like Yellowstone, a fisherman’s blunder in the aquatic system many years ago can have far-reaching effects by forcing an omnivorous predator to seek new foods in the terrestrial landscape.” He added “These surprisingly broad ecological consequences underscore the importance of identifying new methods to suppress lake trout and the value of preventing such invasions elsewhere.”

The release goes onto say that over the last few decades, the Yellowstone lake has seen a significant drop in Elk Calves, but that some of the losses of these elks can't all be pointed at the grizzly bears. Other factors in the losses of elks are due to the whirling disease, according to the release.

The release says recent studies done by researchers at Washington State University have shown that cutthroat trout is an important seasonal food source for as many as 70 percent of Yellowstone's grizzly bears.

Middleton says "we don't know for sure if the grizzly bears are eating the elk calves in the Yellowstone area, but our research has shown a change in the grizzly bear's diet from eating fish to elk calves." UW says Middleton worked under Matt Kauffman, head of Wyoming Cooperative Fish and Wildlife and assistant professor in the Department of Zoology and Physiology. Middleton is now a post-doctoral fellow at the Yale School of Forestry and Environmental Studies.

For more information on this story, you can contact Arthur Middleton at (307) 460-0880 or arthur.middleton@yale.edu