科学美国人60秒:Wolves Unwittingly Help Yogi and Booboo

Wolves and bears sound like unlikely allies. But the resurgence of Yellowstone Park's canine population has helped the bears. In a berry interesting way.

In the 1990s, people reintroduced wolves to Yellowstone Park, where they had been absent for most of the century. As their population grew, they began hunting elk, reducing their number. And with fewer elk snacking on berries, more fruit remained available for bears.

Comparisons of grizzly scat collected in the years before and after the wolves’ return showed an increase in the bears’ berry consumption, particularly during the months of July and August. The study is in the Journal of Animal Ecology. [William J. Ripple et al., Trophic cascades from wolves to grizzly bears in Yellowstone]

Fruit can make up fully half of a grizzly’s diet as it prepares for hibernation. But bears and berries aren’t the only ones to benefit from wolves. The canine comeback also boosted the growth of popular elk foods such as aspen and willow trees. Which proves even a single species can have a beary strong ecosystem effect.

—Sophie Bushwick