Hungry Otters Are Creating a Unique Archaeological Record
Hungry Otters Are Creating a Unique Archaeological Record
By bashing mussel shells onto stones, otters leave behind traces of their activity
By Brigit Katz
smithsonian.com
March 15, 2019 4:23PM
Otters are cute as a button, and clever too; they’re the only marine mammals known to habitually use stone tools. And as is the case with humans of millennia past, otters’ stone tool usage creates a unique archaeological record, a new study has found.
As Discovery’s Lacy Schley reports, otters are resourceful hunters that rely on a variety of methods to access hard-shelled prey like mussels and clams: they might pry the sea creatures open with their teeth, whack them against their chest or a rock placed on their chest, or bang them against a stationary rock. The rocks function like anvils, the international team of researchers behind the study explain in Scientific Reports, and the otters’ rock-smashing behavior is considered tool use because it “involve[s] the controlled use of a detached object.”
For their investigation, the researchers spent ten years observing otters as they chowed down on mussels at the Bennett Slough Culverts, a tidal estuary in California. The team found that the animals used “stationary anvil stones” for around 20 percent of the mussels they ate, and repeatedly returned to the same rocks to crack their snacks open. This in turn left distinctive wear patterns on the rocks’ points and ridges, where the otters tended to strike. The patterns clearly indicated that the stones were being hit from within the water.
The researchers also studied piles of shell fragments, or “middens,” that formed around the rocks. These too had distinct damage marks: the two sides of the shells were typically attached, with a diagonal fracture running down the right side. It is possible, the study authors say, that these patterns stem from otters being predominantly right-pawed. “Right before they hit the rock, they slightly twist the shell so that their right hand is the one that's really smashing it on the rock,” wildlife biologist and study co-author Tim Tinker tells the CBC’s Emily Chung.
Read more: https://www.smithsonianmag.com/smart-news/hungry-otters-are-creating-unique-archaeological-record-180971719/#HVpqWIKG6Sj3CFTX.99
