Sea otter archaeology exists, and it’s awesome
Sea otter archaeology exists, and it’s awesome

                      
                      
          There’s nothing especially remarkable about archaeologists studying stone tools and shell middens—unless they weren’t made by humans. A new study suggests that sea otters create a distinct archaeological record, and it might eventually have a lot to tell us about their evolutionary history.
Sea otters are ingenious—and adorable—tool users. They often pick up small rocks and use them to crack open snails, clams, or mussels; underwater, otters also use rocks to pry abalone loose from the seafloor. Closer to shore, otters whack mussels against protruding boulders until they damage the bivalves’ hinges enough to pry them open. That percussive food preparation leaves behind a unique signature: distinctive marks on the boulder and a pile of broken mussel shells, most cracked in a particular way, piled at the bottom.
“Sea otters have created a distinct, recognizable archaeological record,” wrote Michael Haslam and his colleagues, who claim that by doing a little mustelid marine archaeology, ecologists could track past habitats of sea otter populations and maybe even the evolution and spread of otter tool use.
Sea otter stone tools
Haslam and his colleagues spent a decade, off and on, watching a community of sea otters near Moss Landing, California, and learning their technique. It’s similar to the way other archaeologists watch modern hunter-gatherers in order to better understand flint-knapping and how to interpret the shape of flakes and cores they find elsewhere. They noticed that the otters tended to crack open mussels, which they gathered near shore, on the large boulders that stuck out above the water’s surface. Other prey, like clams, usually came from deeper water, where the otters were more likely to carry smaller stones with them to use as hammers.
Here’s how it worked: an otter would dive to the bottom and emerge, triumphant, with a clump of mussels. Holding a mussel between its forepaws, the otter would bang it against the rock until the hinges had cracked enough that the shell could be pried open with tooth and claw. That sounds like a pretty simple process, but it turned out the otters were surprisingly methodical. They usually aimed for ridges or points on the rock, not flat surfaces—which makes sense, since ridges and points would focus the force of impact at a single point instead of spreading it out. They also seemed to prefer the upper parts of the boulders on the side facing the water.

          
                      
                  