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Jan. 09, 2013

The Sea Otter's Toolkit

by Kara Rogers

Click to enlarge images
The sea otter is one of few species of mammals, on land or in the sea, that uses tools -- an ability that at one time was thought to be possessed only by humans.
 
Among the items in the sea otter's tool kit are rocks, driftwood, empty clam shells, and even glass bottles, all of which may be used to crack open the shells of prey such as clams and abalone (marine snails). While it seems fairly unsophisticated to us, the act of prying open a clam shell with something other than one's teeth or hands (or paws, as the case may be) requires relatively advanced cognitive ability. The task involves forethought, problem solving, and learning, skills made possible by complex structures and integrated neural networks in the brain. To extract a clam or snail from its shell, for instance, a sea otter must identify the type of object that will help it to pry open the shell.
 
Sea otters seem to be specially equipped in other ways for tool use as well. For example, the dexterity of their forefeet enables them to manipulate tools with decent precision and to pick snails out of kelp beds and dig clams from beneath the mud on the bottom of the sea floor. They also have loose flaps of skin under their forelegs that serve as pouches to hold both prey and tools as they forage underwater. They then carry the objects with them to the ocean's surface, where they eat (rolled over on their backs, in their characteristic belly-up fashion).
 
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In addition to rocks and other hard objects for opening shells, sea otters have been known to employ other kinds of tools, including kelp fronds. An observation described in the 1980s indicated that sea otters may wrap crabs in kelp fronds to immobilize them, holding them captive until the sea otters get around to eating them. Sea otters also use kelp fronds as security blankets -- in a snug kelp wrap, a sea otter is safe from drifting off in currents as it rests.
 
It is thought that all sea otters -- there are two subspecies, the California, or southern, sea otter (Enhydra lutris nereis) and the northern sea otter (Enhydra lutris kenyoni) -- can learn to use tools. Pups appear to learn to use objects by watching their mothers, and adults presumably can learn new foraging and tool-use techniques as they need them or are introduced to them.
About Kara Rogers

Kara is a freelance science writer and senior editor of biomedical sciences at Encyclopaedia Britannica, Inc. She is the author of Out of Nature: Why Drugs From Plants Matter to the Future of Humanity (University of Arizona Press, 2012).

The views expressed are those of the author and are not necessarily those of Science Friday.

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