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Emily Grason on invasive snails in the American Naturalist

Wednesday, January 25, 2017 - 09:00

Recognizing the signs of a predator can mean the difference between living to see another day and becoming another critter’s midday snack.

All prey animals, whether a swift-footed deer or a slow-moving snail, use cues from their environment to sense the presence of a threat. It’s what keeps them alive — or at least gives them a shot at getting away.

invasive snail feeding on an oyster


An Atlantic oyster drill snail feeding on a juvenile Pacific oyster. The drill is one of four species of invasive marine snails in Washington state.Emily Grason/University of Washington

But the specific cues that trigger prey defenses vary depending on the species of prey and their history in the ecosystem, a new University of Washington study finds. The research, published online Jan. 12 in the journal American Naturalist, analyzed the behavior of seven species of marine snails found in Washington waters — three native and four invasive — and discovered that native and invasive snails use different cues to assess risk.

The invasive snails were introduced unintentionally at least a century ago as hitchhikers on imported oysters. In experiments with these invasives, a UW researcher found that they fled quickly (as snails can do) and hid when they smelled chemicals released from crushed snails of the same species — meant to mimic a predator eating their close kin. This is surprising because these so-called “alarm cues” don’t provide the snails with much of a clue as to what or where the danger might be. Panicking with only vague information to go on could even be counter-productive, causing snails to miss their lunch unnecessarily, or actually make them more vulnerable to a predator.

By contrast, the three species of native snails didn’t react when they encountered the same situation. Instead, they went about their business until they had multiple sources of information, including from a predator and other prey, before fleeing or hiding.

In other words, the fear reactions in native snails were more finely tuned, while the invasive snails jumped ship at the first whiff of a threat.

“It’s pretty rare for a distinction between native and invasive species to be as consistent as it is here — which suggests it might hold true in other species and locations,” said author Emily Grason, an invasion ecologist at UW-based Washington Sea Grant who recently completed her doctorate in biology at the UW.


Grason dedicates this research to the memory of the late UW ecologist Robert Paine, who published his seminal work on “keystone species” in the same journal 50 years ago.

Read the full article on UW Today

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