Radio Script
1999

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Salmon Hold Ecosystem Together
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STORY: Native Americans of the Pacific Northwest and Alaska have long understood the unique role salmon play in the ecosystem, and they've adjusted their lives to the salmon's annual return.

Animals also have learned to live in sync with salmon. Each summer, bears gather from miles around to feast on the abundance of easy protein. Salmon carcasses in turn attract thousands of eagles and seagulls.

But now scientists are discovering some interesting new ways that salmon affect the lives of other species. Merav Ben-David is an ecologist at the University of Alaska Fairbanks. Her studies in Southeast Alaska found that the annual salmon run determines such things as the mating of mink and how many marten survive to adulthood.

BEN-DAVID: "And what I found was that salmon are a very important resources to all these carnivores. They determine breeding for mink. They determine reproductive success for marten and they definitely affect the use of the resource for bears."

Mink in most parts of their range breed in the springtime. But mink in Southeast Alaska breed later, usually in concert with the arrival of salmon, according to Merav Ben-David.

BEN-DAVID: "When you have a super abundance of salmon you can raise your young successfully no matter what else is happening. It's not as if female mink says 'Oh, I'll breed when I see the first salmon come into the stream.' Through evolution, the females that bred later and corresponded their breeding with salmon availability were more successful and left more genes to the next generation."

More complicated is salmon's influence on marten. A relative of the mink, marten live in spruce forests and hunt primarily small rodents like mice and voles. But in times of scarce prey, Merav Ben-David says marten will turn to salmon in order to feed their young.

BEN-DAVID: "The salmon coming into the system are an easily available alternative food. Females in years when they don't have voles can switch to eat salmon. They prefer voles. But when the voles are missing from the system, the marten switch to salmon and are able to maintain successful reproduction."

And while Merav Ben-David began her research thinking, as many people do, that all bears love salmon, she discovered that some bears--especially females with young cubs--shied away from gatherings of other bears at salmon streams. She believes that sows may be trying to protect the cubs from being killed by larger males.

As an ecologist, Merav Ben-David likes to figure out how living things are connected to each other. In Southeast Alaska, she found that the return of salmon is a kind of glue that holds the ecosystem together.

OUTRO: For Arctic Science Journeys, this is Doug Schneider, reporting from Fairbanks, Alaska.