How Sea Otters Saved a Salt Marsh

Vital salt marsh habitat in California was saved by a resurgence of the area's extremely cute top predator, researchers say. In a study published in the journal Nature, marine ecologist Brent Hughes and other researchers say sea otters dramatically slowed erosion in Elkhorn Slough in Monterey Bay, the nation's second-largest estuary. After the otters were almost hunted to extinction for their furs, the area's ecosystem was thrown off balance because there were no otters to eat the shore crabs that ate pickleweed, the estuary's dominant plant, the CBC reports. The crabs sped up erosion by eating the plant's roots and burrowing into creek banks—but things turned around when otters returned and started chowing down.

"They're really good at eating crab," Hughes tells NPR. "It's just easy pickings for them. They can actually grab about 10 of these at a time. They just eat 'em like popcorn, shell and all." Otters began returning to the area around 40 years ago and the population now stands at around 100, the highest concentration in California. "The hotel is full. The no vacancy light's on," Hughes says. "You can't stick one more otter in there if you tried." The researchers analyzed erosion rates going back to the 1930s, the AP reports. They also fenced off sections of creek in a way that allowed crabs in but kept otters out, and found that those sections eroded a lot faster than sections that were identical apart from the otter fences.

The researchers say the otters stopped creek banks from being like "Swiss cheese," preventing around 10 inches of salt marsh erosion per year. A hunting ban helped sea otter numbers recover, as did a program at the Monterey Bay Aquarium—the inspiration for the aquarium in Finding Dory—that raised and released orphaned otters. Lekelia Jenkins, a marine sustainability scientist who wasn't involved with the study, tells NPR that it could become a "classic in the literature." She notes that marshes play an important role in preventing flooding, meaning sea otters go from "just a cute thing we like to have around to something that can protect our livelihoods and our properties." (More sea otter stories.)