美国科学60秒 SSS 2013-08-02

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　　Wolves and grizzlies¹ sound like unlikely allies. But the resurgence² of Yellowstone Park's canine³ 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 elk⁴, reducing their number. And with fewer elk snacking on berries, more fruit remained available for bears.

　　Comparisons of grizzly⁵ 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.

　　Fruit can make up fully⁶ half of a grizzly’s diet as it prepares for hibernation⁷. 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 willow⁸ trees， which proves even a single species can have a berry strong ecosystem⁹ effect.

　　Thanks for the minute for Scientific American 60-second Science. I'm Sophie Bushwick.

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