sea otters demonstrate at least three distinct methods of tool use. two pertain to the use of stones and one pertains to the use of kelp as an anchor. stones can be used as anvils, in which they are rested on the chest of an otter lying on the ocean surface. hard prey items can be pounded against the anvil to create cracks and facilitate access to flesh. stones can also be used as hammers, primarily to extract shellfish from their substrates. other important aspects of otter tool-use behaviors include the use of tool composites and tool reuse. tool composite is the term given to the combination of two rocks as an anvil and a hammer, separately, but used on the same prey item at once. tool reuse is demonstrated by the use of the same stone in a variety of feeding opportunities over one large feeding period.