For moose, hunger is fiercer than wolves

As winter sets in and the need for food grows, Wyoming moose (Alces americanus) are more likely to hold their ground when wolves (Canis lupus) approach.

In a study published in Ecology, researchers from the University of Wyoming found the relationships between wolves and big-game species like moose can be complex, making it difficult to reach conclusions about how fear of wolves impacts the ecosystem.

“These moose were seeking food wherever they could find it, even if that meant foraging in areas where traveling wolves would expect to find moose,” said lead author Brenden Oates, a TWS member now with the Idaho Department of Fish and Game, who conducted the research as a UW graduate student.

Oates and his team tracked the movements of dozens of GPS-collared moose and wolves in Grand Teton National Park and the Bridger-Teton National Forest over a five-year period. They detected 120 unique encounters — moments when moose and wolves were within about 1,600 yards of each other — involving 25 individual moose and six wolf packs.

In early winter, they found, moose movements increased following encounters with wolves, but only when the wolves were within about 550 yards. Even then, the moose didn’t avoid the streams and marshy areas they prefer. Late in the winter, when the moose were presumed to be hungrier, they showed no change in movement around wolves.

“These results tell us that moose prioritized foraging to avoid starvation in lieu of avoiding encounters with wolves,” Oates said.

The findings support the “starvation-predation hypothesis,” researchers concluded, which predicts that when food is scarce, prey will forage in risky places, even when the risk of predation is high. Yet the moose seem to respond differently than elk (Cervus canadensis). While moose, which are larger and more likely to hold their ground, previous research found that elk — wolves’ primary prey in the region — will increase their movement rates and alter habitat use during winter when wolves come within 1,000 meters.

“The bottom line is that researchers are finding more exceptions than rules for how risk effects operate at an ecosystem scale,” Oates said.

Header Image: A moose grazes in Wyoming. ©Mark Gunn