in central california, sea otters feed mostly on sea urchins, abalones, and rock crabs. rocks are used to knock abalones from the structure on which they are growing. rocks can also be used to crack crab carapaces. scientists have studied areas of california where up to 80% of abalone shells display crack patterns that are suggestive of breakage against rocks performed by otters. in areas near the aleutian islands, less tool use is recorded and sea otters consume much more fish. the diet in these areas also includes sea urchins, which otters can break with their forepaws, mollusks, and crustaceans.