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Sea otters' stone tools provide new clues for archeologists

Animal archeology could reveal where sea otters lived in past, how tool use evolved



Emily Chung · CBC News · Posted: Mar 14, 2019 10:00 AM ET | Last Updated: 3 hours ago

After visiting several sites where sea otters were floating on their backs, carrying rocks on their chests and using them to crack food open, Tinker and his team took their visitors to Bennett Slough Culverts in Moss Landing, Calif., where otters pull off and eat mussels encrusted on a series of drainage pipes. The otters can't collect stones from the bottom there because it's muddy. But humans had piled rocks along the side of the road that the otters were pounding the mussels on.

Rock study

Tinker, a biologist, said the archeologists "immediately did something we'd never done — climbed down, scrambled over the rocks, right down into the water, basically, and started studying the rocks that the otters were pounding their mussels on."

Uomini recalls that initially, they didn't see anything unusual about the rocks. Then they started noticing broken mussel shells piled up in certain places.

"At first we thought, 'Hey, that's funny. Somebody must have come here, and had a picnic and eaten loads of mussels,'" said Uomini, who mostly studies stone tools made by ancient human relatives 500,000 to a million years ago..

Then it occurred to her that since the mussels were raw, that "somebody" was probably otters, not humans.

"And then we realized these piles of mussels were everywhere, and that there were damaged rocks near them."

Natalie Uomini sets up her camera to observe otters at Elkhorn Slough, close to Bennett Slough Landing in Moss Landing, Calif. (Michael Haslam)
Tinker said he was dumbfounded: "Within their first hour of being out there, they had already found something that we'd missed for decades."

That highlights the power of researchers from very different disciplines working together on problem "and bringing different ways of looking at nature together," he added.