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Environment | Flora and Fauna

How Rebounding Wolves Are Helping Feed Grizzly Bears

BOISE, Idaho — A new study released Monday draws a direct relation between the reintroduction of the gray wolf and the amount of berries consumed by grizzly bears.

The result of this study found that with wolves in Yellowstone National Park keeping elk populations in check, bears are starting to consume more berries.

The study, which appears in the Journal of Animal Ecology, looked at elk populations in the Yellowstone National Park region of Wyoming over the past 50 years. The research team lead by Bill Ripple at Oregon State University looked at the amount of berries found in bear scat.

“Wild fruit is typically an important part of the grizzly bear diet,” Ripple said. “Especially in the late summer when they are trying to gain weight as rapidly as possible before winter hibernation.”

Researchers found that before wolves were reintroduced to Yellowstone, elk populations grew and ate a significant amount of wild berries. Those berries are also part of a grizzly bear diet. Before wolf numbers started coming back in 1995, there were less berries found in the grizzly bear diet. After wolves were reintroduced, wolves started preying on elk — and less elk means more berries for the grizzly bears.

Grizzly Bear Timeline

  • 1975 – Grizzly bears listed as threatened
  • 1982 – Recovery plan issued and implemented
  • 1993 – Recovery plan revised (bear populations rebound)
  • 2007 – Yellowstone grizzly ears delisted
  • 2009 – Delisting reversed in federal court
  • 2013 – New delisting plan published for comment

The exciting part of this study, said Chris Haney, the chief scientist with Defenders of Wildlife, is the fact that this is a first-of-its-kind study.

“I was actually surprised,” he said. “This is good news for the Yellowstone grizzly bear.”

Haney also said: “If you think about nature, bears are not a species that would come to mind and say they are really vulnerable to losing this one kind of food. They are just very catholic in their food preferences,” he said. What he means is bears are omnivores that eat fruits and berries, bugs and meat. They are well prepared to adapt to a reduction in one of those food groups.

Haney said he is impressed that this research found a strong relationship between the elk population and the amount of fruit found in bear scat.

“It’s a good thing because when you have more than half of a puzzle explained by one variable, yeah thats big news. Any time that we can find one variable,” Haney said.“That explains more than half of the noise in the chaos that we see in natural systems, yes, thats really worth paying attention to.”

A study like this could eventually play a role in the U.S. Fish and Wildlife Service proposal to delist the Yellowstone grizzly bear. A push to delist the bear was overturned in federal court after environmental groups claimed the federal wildlife agency failed to take into account the role plants and trees have on the grizzly bear diet.

There are approximately 700 bears around the Yellowstone region, according to recent estimates.