Tool use by sea otters

The sea otter, Enhydra lutris, is a member of the Mustelidae that is fully aquatic. Sea otters are the smallest of the marine mammals, but they are also the most dexterous. Although sea otter tool use is most associated with their use of stones as anvils and hammers, they have been observed using a wide array of other objects as tools, including empty shells, driftwood, and discarded cans or bottles. Sea otters also use kelp or seaweed as an anchor to buoy themselves or to immobilize prey such as crabs. Some sea otters will even improvise techniques, such as ripping off the claws of crabs and using them to pry open the crab's own shell.

Sea otters have demonstrated the capacity for social learning, with knowledge passed down both vertically from mom to pup and horizontally within groups. The frequency of tool use varies greatly between geographic regions and individual otters and depends heavily on maternal transmission. Regardless of the frequency, the use of tools is present in the behavioral repertoire of sea otters and is performed when most appropriate to the situation. This flexibility in whether or not sea otters use tools and in the types of tools they use further emphasizes the importance of learning.

Sea otters are one of only three species, along with humans and bottlenose dolphins, among which individual-level specialization in tool use is documented. Genomic analyses of sea otters and bottlenose dolphins indicate that the RELN gene, which encodes the reelin protein and modulates synaptic plasticity and long-term potentiation, has been under positive selection among both species. The authors suggest that the maternally and socially transmitted variation in foraging behavior and tool use displayed by both sea otters and bottlenose dolphins might be linked to genetic adaptations for increased memory and learning abilities.