October 13, 2026 — Fear changes behavior. For a ribbed mussel clinging to a New England salt marsh, the presence of a blue crab nearby can mean eating less and holding tighter to the marsh platform, bracing for danger. The crab doesn’t even have to attack.
That response — what scientists call a “fear effect” — is at the heart of research by University of Rhode Island graduate student Maja Nielsen. A master’s student in URI’s Biological and Environmental Sciences program working with Assistant Professor of Watershed Ecology Shelby Rinehart, Nielsen is studying whether fishing-driven shifts change how ribbed mussels respond to the threat of predation.
Predators shape prey populations in two ways, she explains: by eating them or by scaring them. “There’s some evidence that the fear effect may be even more important in determining ecosystem functions than the consumptive effect,” she said, “because predators can scare a lot more prey than they can eat.”
Blue crabs are not intentionally bullying mussels. Rather, ribbed mussels detect subtle shifts in the chemical compounds crabs release after feeding, triggering a fear response that changes their behavior.