Sea Otters Use Tools to Break Open Larger Prey, Sparing Their Teeth, Study Finds

The adorable otter is North America’s smallest marine mammal, as well as the largest species of the weasel family, which also includes skunks, badgers and wolverines.

With roughly 3,000 southern sea otters left in California, they are listed as threatened under the United States Endangered Species Act and play a crucial role in the restoration of the state’s damaged kelp forests, a press release from UT Austin said.

A new study by a team of researchers from Monterey Bay Aquarium; University of California, Santa Cruz (UC Santa Cruz); The University of Texas at Austin (UT Austin); and elsewhere has found that otters who use tools like rocks and shells to break open the thick outer layers of mollusks are able to eat bigger prey, giving them higher rates of energy consumption while reducing wear on their teeth.

According to Chris Law — a UT Austin postdoctoral researcher who was the study’s lead author while a UC Santa Cruz graduate student — sea otters prefer to eat abalone and sea urchins, which are relatively easy to break apart, but those delicacies are declining, reported The Guardian.

The researchers said that, due to the absence of their preferred foods, sea otters often look for clams, mussels, marine snails and crabs. However, the snails’ hard shells can be damaging to their teeth.

“There’s fishing and habitat destruction, so their favorite prey are gone and they have to switch to alternative preys,” Law said, as The Guardian reported. “What we found is that [using tools] actually allows them to switch to those prey.”

The research team enlisted volunteers to track 196 southern sea otters off the California coast to gain a better understanding of how they use tools in a habitat that is changing quickly, the press release said. The team monitored tool use and linked it to the otters’ dental health and dietary patterns.

They found that using the tools meant less tooth injuries.

“Sea otters vary in how often they use tools,” Law said in the press release. “The females are likely using tools to overcome their smaller body size and weaker biting ability in order to meet their calorie demands. Raising pups takes a lot of energy, and the females need to be efficient in their foraging. The study shows that tool use is an important behavior for survival.”

The study, “Tool use increases mechanical foraging success and tooth health in southern sea otters (Enhydra lutris nereis),” was published in the journal Science.

While using tools widened the availability of different types of prey for both female and male otters, the researchers found that female otters had less damage to their teeth. It is more likely for female otters to use tools, research has shown, and the new study found that those who did had access to larger or harder prey than those who did not. The researchers found that females were able to eat prey that were as much as 35 percent harder in comparison with males who used tools.

Females of other species, such as chimpanzees, bonobos and dolphins, have also been known to utilize tools more often than males. Females of these species tend to raise their offspring and are the ones who pass down their tool-using behavior.

“This behavior really allows them to eat other prey items and in an environment where that’s depleted. It really just showcases how it’s important for their overall survival. If there are no urchins and abalone for them to eat and they are faced with other prey types they can’t open, they can’t survive,” Law said, as reported by The Guardian.