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. sea otters are known for their ability to use stones as anvils or hammers to facilitate access to hard-to-reach prey items. there are three recognized subspecies of otters, all of which exhibit tool use behavior in some capacity. tool use behavior is more associated with geographic location than sub-species. most behavioral research has been conducted on "enhydra lutris nereis", the californian otter, and some has been conducted on "enhydra lutris kenyoni", the alaska sea otter. sea otters frequently use rocks as anvils to crack open prey, and they are also observed to rip open prey with their forepaws. while lying on their backs, otters will rip apart coral algae to find food among the debris. the frequency of tool use varies greatly between geographic regions and individual otters. 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.