In Alaska, bear poop sweetens the ecosystem

ANCHORAGE, Alaska — Does a bear leave scat in the woods?

The answer is obvious but the effects on an ecosystem may not be.

A study by Oregon State University researchers concludes that brown and black bears, and not birds, as commonly thought, are primary distributors of small fruit seeds in southeast Alaska, spreading the seeds through their excrement.

“Bears are essentially like farmers,” said Taal Levi, an Oregon State assistant professor. “By planting seeds everywhere, they promote a vegetation community that feeds them.”

Seed dispersal is a key component in the understanding of any ecosystem, Levi said.

The study is the first instance of a temperate plant being primarily dispersed by mammals through their gut, Levi said.

The finding suggests repercussions for plant life when bears are removed.

Brown bears, or grizzlies, flourish in size and numbers in the Tongass National Forest, America’s largest, because they gorge on spawning salmon. As they wait for fish to enter streams, they eat berries.

Levi and graduate student Laurie Harrer, the study’s primary author, set up motion-triggered video cameras to detect what was eating berries.

They collected bear DNA from saliva left on plants after berries disappeared. They recorded birds picking off a few berries at a time but bears gulping them by the hundreds.

When brown bears shift to eating fish, black bears move into berry patches.

Both bears, through their scat, disperse fruit seeds by the thousands, profoundly affecting what grows in the forest, according to the researchers.

Rodents that find bear scat further disperse seeds, burying them in caches a few millimeters deep, Levi said. If rodents lose track of caches, there’s a chance for new plant growth.