"This year, for example, there was virtually minimal kelp," she says. "The barrens were barren -- just urchins.”

McHugh attributes this increase to elevated recruitment during years in which sea urchin larvae settled out of the plankton in high densities and survived the tumultuous early years of adolescence. Urchins have become so numerous that they have since spawned several citizen science projects aimed at curtailing their numbers.

Some Heroes Wear Furry Capes

Traditionally, California’s iconic sea otter has stepped in to keep urchin populations in check. Otters feed on sea urchins, which in turn keeps them from overgrazing on kelp. Without otters, the implication is that we would cease to have kelp forests at all.

So what happens when otters forget just what is on the menu?

In the same way that you can eat many things but might prefer to eat pizza, otters are known to be generalists in their diets. But individuals have specific preferences which are passed from mother to pup.

James Watanabe is a lecturer at Hopkins Marine Station, and he was the first to suggest that otters may have developed a “cultural memory loss.”

“From the big pulse of recruitment in the ’70’s, up until now, when the urchins started showing up again, there were three generations of otters with some sea urchins present," he says, "but not enough for any otter to focus on as the main part of the diet."

'It’s not that the sea otters aren’t doing their job. They’re doing it very well, there’s just much more to the story than otters and urchins.' Joe Tomoleoni, USGS

“It’s possible that the behavior died out if everyone who remembered how to do it has died.” adds Aimee Dunlap, who studies animal cognition at the University of Missouri. “When they reintroduced the California Condor," she recalls, "they had to haul out carcasses, because they’d had a gap in the parents teaching the young how to be a Condor.”

A Historical Precedent?

Watanabe points to the example of Kelletia, a large predatory snail that moved north into kelp forests during the 1977-1978 El Niño, as a historical example of a time when otters exhibited similar behaviors.

“It’s a big, meaty snail, and it has a big shell, and it got to the point where you could put your hand down anywhere in the kelp beds and one would be within a meter of your hand. But the otters weren’t going for them.”

Eventually, he began to notice changes beneath the waves. “Within a period of about six months, the abundance dropped and there were a bunch of busted shells all over the place. It’s the damage that only an otter could typically do.”

Can We Really Blame the Otters?

But Joe Tomoleoni, an otter biologist with the U.S. Geological Survey, bristles at the idea of blaming the urchin boom solely on otters, arguing that it ignores the inherent complexity of kelp forests.