When sea otters hammer mussel shells against rocks to help open them, they're leaving behind their own archaeological record that can't be compared to any other creature, according to a new study.
원문출처 : https://www.cnn.com/2019/03/14/world/sea-otter-stone-anvil-evidence-scn/index.html
원문출처 : https://www.cnn.com/2019/03/14/world/sea-otter-stone-anvil-evidence-scn/index.html