When sea otters lose their favorite food, they can use tools to acquire new ones

In parts of the ocean where sea otters face strong competition for their favorite food, some otters get by with the help of tools — like rocks and even glass bottles — that allow them to crack open tougher prey that they otherwise wouldn’t have been able to eat.

That’s according to a new study of sea otters in Monterey Bay, California, which examined individual otters’ tool use to see how it affects their health and diet.

The results, published in the journal Science, reveal how these special skills can increase their chances of survival in an uncertain world.

Sea otters are large marine mammals that spend their days foraging in kelp forests. They dive to the bottom to grab tasty morsels, sometimes even stones, which they want to use as tools. They bring these to the surface and float on their backs, using their bellies as tables as they prepare to open and eat their snacks.

“Their preferred prey is usually sea urchins and abalone,” says Chris Law, a biologist at the University of Texas and the University of Washington, who notes that sea urchins and abalone are relatively easy for otters to break apart.

But in places where many otters coexist in Monterey Bay, “unfortunately, all of these prey items have declined or declined. This means otters need to eat alternative foods,” says Law. “Many of these alternative foods are prey animals with super-hard shells that can only be broken through by external force.”

Snails, for example, are plentiful in the bay, but they are low in calories and “basically like a rock that you have to break into to eat the inside,” Law says.

Although sea otters are known for using tools, not all people actually wield them. Some otters forego this altogether and simply specialize in eating soft prey. Some otters use tools occasionally, while others use them most of the time when foraging.

“We were interested in this variant of tool use,” Law says, so he and some colleagues analyzed data from 196 otters in California.

These tagged otters are closely monitored by volunteer “otter spotters.” This means researchers know what they eat, how big and hard the prey is, and whether the otter used a tool to eat it.

It turns out that frequent tool users were able to eat harder and larger prey, says a report in the journal Science. This was particularly important for female otters because they are smaller than males and cannot bite as hard.

“Normally they wouldn’t be able to penetrate tougher prey,” Law says. “But they use tools more frequently than men, giving them access to these novel food sources.”

In addition, the use of tools protected the otters’ teeth. The researchers were able to perform dental exams on their otters and found that tool users suffered less tooth damage from grinding on hard shells.

“Without their teeth, they obviously can’t eat. Then they die. What we suspect is that this behavior really allowed them to continue living even though they didn’t have their preferred prey,” says Law.

He explains that some otters learn to specialize in eating hard, low-calorie snails by using tools very frequently to “basically become really, really, really good at processing lots and lots and lots of snails every day.” “, instead of looking for high-calorie snails. High-calorie foods that require no tools to open but are in short supply.

“This is such an important paper,” says Rob Shumaker, president and CEO of the Indianapolis Zoo and one of the authors of a book titled Behavior of animal tools.

He says scientists have spent decades documenting tool use in dozens of species; The use of tools by sea otters, for example, has been known since the 1960s. But now studies like this show that this area of ​​research is beginning to change.

“It’s no longer about describing the actual tool use or tool production,” says Shumaker. “It describes the impact it has on this animal’s life.”