Oh, otters. The adorable weasel-puppies of the water. They famously hold paws while they’re sleeping so they don’t drift apart, which is about as cute as you can get. But these little marine mammals are also quite crafty. They’re often observed cracking open a tasty meal of mussels, crab or clams with the help of rocks. And a new paper out today in Scientific Reports says otters’ handy use of rocks can leave an archeological record.

There are a few ways otters get to the meat of their pre