Surprising Way Wolves Help Bears Fatten Up in Yellowstone

grizzly bear posing in the wilderness — Grizzly bears live throughout the northern and western portions of North America. The omnivorous creatures eat both berries, fish and large mammals where they are available.

(Image credit: Yellowstone National Park)

The reintroduction of wolves into Yellowstone National Park has an unexpected upside: It's helping to fatten up the bears, new research suggests.

The wolves have kept the park's population of elks (prey for wolves) in check, which in turn limits how many berry-producing shrubs the elks consume. As a result, the bears have more tasty berries to eat, finds a study published today (July 29) in the Journal of Animal Ecology.

The study points "to the need for an ecologically effective number of wolves," said co-author Robert Beschta, a researcher at Oregon State University, in a statement. "As we learn more about the cascading effects they have on ecosystems, the issue may be more than having just enough individual wolves so they can survive as a species. In some situations, we may wish to consider the numbers necessary to help control overbrowsing, allow tree and shrub recovery, and restore ecosystem health."

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"Wild fruit is typically an important part of grizzly bear diet, especially in late summer when they are trying to gain weight as rapidly as possible before winter hibernation," said study co-author William Ripple, a forest ecosystems researcher at Oregon State University, in a statement. "Berries are one part of a diverse food source that aids bear survival and reproduction, and at certain times of the year can be more than half their diet in many places in North America."

Tia is the editor-in-chief (premium) and was formerly managing editor and senior writer for Live Science. Her work has appeared in Scientific American, Wired.com, Science News and other outlets. She holds a master's degree in bioengineering from the University of Washington, a graduate certificate in science writing from UC Santa Cruz and a bachelor's degree in mechanical engineering from the University of Texas at Austin. Tia was part of a team at the Milwaukee Journal Sentinel that published the Empty Cradles series on preterm births, which won multiple awards, including the 2012 Casey Medal for Meritorious Journalism.