Brown bears help feed small mammals with seeds in scat

By Dana Kobilinsky

A brown bear sow catches a fish with her cubs nearby in Alaska. Salmon abundance helps support the bears, but fruit is an important carbohydrate source. The seeds in brown bear scat feed small rodents, according to new research. ©Berkely Bedell

In Alaska, small mammals such as mice and voles eat and disperse seeds that they get from bear scat, according to new research.

Previous research on black bears (Ursus americanus) has shown small mammals utilizing and dispersing seeds found in scats, but researchers hadn’t yet looked at salmon-subsidized brown bears (Ursus arctos) in Alaska and the benefits of dense populations on seed dispersal and to small mammals.

In the study published in Ecosphere, researchers collected bear scats in coastal Alaska to determine what fruits were being consumed and to determine the nutritional characteristics of the associated seeds.

“We determined that brown bears were eating 12 different fruits from in the study area,” said lead author of the study Yasaman Shakeri, a wildlife researcher with the Alaska Department of Fish and Game who worked on the project as part of her master’s thesis at Oregon State University. “A single brown bear scat can have hundreds of thousands of seeds, particularly devils club and blueberry.”

Shakeri and her colleagues also placed trail cameras near bear scats in the upper Chlikat Valley. They recorded what species visited the scats and found that northwestern deer mice (Peromyscus keeni) and northern red-backed voles (Myodes rutilus) were the most frequent visitors. “We expected to see small mammals visiting the bear scats, but we didn’t expect to see such high visitation rates,” Shakeri said.

Shakeri said these results are important because the availability of salmon allows for high brown bear densities on the landscape. These bears also depend on fruit as an important carbohydrate that helps them gain weight prior to hibernation. The seeds left in bear scats are then secondarily dispersed by deer mice, which can result in some of those seeds surviving and becoming future fruiting plants.

“It’s important to understand how high brown bear densities alter the ecosystem,” she said. “Coastal brown bears once roamed most of the West Coast in the contiguous United States and the extirpation of these bears may have affected the plant composition and seed dispersal on the landscape.”

Check out this video of a northern red-backed vole feeding on seed-filled bear scat.

Dana KobilinskyDana Kobilinsky is a science writer at The Wildlife Society. Contact her at dkobilinsky@wildlife.org with any questions or comments about her article. You can follow her on Twitter at @DanaKobi.

Read more of Dana's articles here.


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