What does a bear do in the Alaska woods? Disperse seeds

  • By Dan Joling
  • Monday, February 19, 2018 5:23pm
  • News

ANCHORAGE — 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 distributers 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. The 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.

It’s an intricate system starting with salmon attracting bears, Levi said.

Laura Gough, an ecologist at Towson University who has conducted research for more than 20 years on how plants interact with other organisms in Alaska’s tundra, said a lot of ecology research focuses on uncovering those relationships and how whole systems change if they’re disrupted.

“When you think about that, if the species is an important food source, then if that plant should diminish in abundance, there could be a whole suite of changes to that ecosystem,” she said.

When she read the study, she said, she thought of the dodo bird stories she tells to students in biology classes. The extinct birds spread seeds of certain plants.

“When dodos went extinct, those plants basically went extinct as well,” she said. “So, this link between animals that eat plant seeds and disperses them — that can maintain both populations.”

The Oregon State study concludes that if bears are removed, the seeds they move would simply fall to the ground. A decline in bear density, even if only brown bears, likely leads to a reduction in seed dispersal with consequences for plants.

More in News

Jasmine Chavez, a crew member aboard the Quantum of the Seas cruise ship, waves to her family during a cell phone conversation after disembarking from the ship at Marine Park on May 10. (Mark Sabbatini / Juneau Empire file photo)
Ships in port for the week of July 20

Here’s what to expect this week.

Police and other emergency officials treat Steven Kissack after he was shot on Front Street on Monday, July 15, 2024. (Mark Sabbatini / Juneau Empire file photo)
Names of officers involved in death of Steven Kissack released, along with more details of standoff

JPD states Kissack threatened to kill officers; one officer who fired gun cleared in 2016 shooting.

U.S. Rep. Mary Peltola, D-Alaska, speaks on Jan. 4, 2024, at a town hall meeting on the possible Albertsons-Kroger grocery merger. The meeting was held at the Teamsters Local 959 headquarters in Anchorage. Peltola said on Tuesday she has not decided whether to support her party’s likely candidate, Vice President Kamala Harris. (Yereth Rosen/Alaska Beacon)
Rep. Mary Peltola withholds support for Kamala Harris, is ‘keeping an open mind’

Congresswoman says she’s considering Harris presidency’s affect on Alaska as an oil-dependent state.

People arrive for a service at Resurrection Lutheran Church on Sunday. (Mark Sabbatini / Juneau Empire)
Lawsuit: Resurrection Lutheran Church leaders have been ousted, clarity in ‘ministerial work’ needed

Pastor Karen Perkins, two others targeted in long-brewing feud at church known for helping homeless.

(Michael Penn / Juneau Empire file photo)
Police calls for Sunday, July 21, 2024

This report contains public information from law enforcement and public safety agencies.

(Michael Penn / Juneau Empire file photo)
Police calls for Saturday, July 20, 2024

This report contains public information from law enforcement and public safety agencies.

(Michael Penn / Juneau Empire file photo)
Police calls for Friday, July 19, 2024

This report contains public information from law enforcement and public safety agencies.

Michele Stuart Morgan (right), a Juneau Board of Education candidate, signs a qualifying petition for Jeff Redmond (center), who is also seeking one of three school board seats in the Oct. 1 municipal election, just before Monday’s filing deadline at City Hall. At left, Deputy Municipal Clerk Diane Cathcart processes last-minute paperwork filed by candidates. (Mark Sabbatini / Juneau Empire)
Here’s the candidates certified for the Oct. 1 municipal election ballot as the filing deadline passes

Two running for mayor, seven for two Assembly seats, six for three school board seats.

A U.S. Coast Guard Air Station Sitka helicopter hovers over Sitka Sound during routine hoist training on April 25, 2023. (Lt. Cmdr. Wryan Webb/U.S. Coast Guard)
Coast Guard calls off search for trio who went missing flying from Juneau to Yakutat

Haines pilot Samuel Wright, Yakutat residents Hans Munich and Tanya Hutchins were on plane.

Most Read