Biology Reference
In-Depth Information
In addition, sea otters have completely webbed, flipper like feet that are perfect for swimming,
though extremely awkward on land. Moreover, in another curious evolutionary twist, the hind feet are
“backwards”; that is, the big toe on the hind foot is on the outside of the foot, rather than on the side to-
ward the body. This peculiar adaptation may make it easier for the otter to swim on its back, a position
in which it spends much of its time.
Besides sleeping on its back, the sea otter will often emerge from a dive with both a shellfish and a
small, flat rock. Rolling onto its back, with the rock on its stomach, the sea otter next holds the shellfish
in both front paws and pounds it against the rock to break the shell and expose the meat within. Cer-
tainly this is a fascinating use of a tool by this animal!
One popular myth, at least as far as Alaskan sea otters are concerned, is that oil spills such as the
infamous
Exxon Valdez
disaster wiped out sea otters along much of the Alaska coast. It's true that sea
otters are more likely to die from oil spills than are seals; the latter have blubber to insulate them, while
sea otters, once their protective fur is matted by oil, succumb to the cold. However, as destructive as
oil spills are, they don't reach into many bays and setbacks in the shoreline, where substantial numbers
of sea otters avoid the oil and survive. Oil spills such as that from the
Exxon Valdez
certainly do great
harm to the local population of sea otters, but don't eliminate them.
Male sea otters often congregate in large rafts or pods, some containing more than five hundred ot-
ters. Females also form pods, though substantially smaller ones.
Like most of their weasel family brethren, sea otters have delayed implantation. Unlike their relat-
ives, however, baby sea otters are fairly large (about three pounds) at birth, with eyes wide open and a
furred body. This makes perfect sense; blind, nearly naked young would have little chance of surviving
in the frigid ocean.
In virtually all cases, the mother sea otter bears only a single pup. Although relatively few sea otter
births have actually been observed because they happen so quickly, pups apparently may be born either
on land or in the water. The pup sleeps cradled on its mother's stomach, while she floats easily and
contentedly—a sight that has certainly helped endear the sea otter to countless people.
Despite their incursions against commercially valuable species such as crabs, abalone, and sea
urchins, it's gratifying to know that sea otters are no longer in danger of extinction. They are unique
and fascinating—an extreme example of evolutionary adaptation in a family that has specialized in it.
Just as the last piece of an intricate jigsaw puzzle, snapping into place with a faint but satisfying
click, makes the image on the puzzle's face entire, the sea otter's mastery of the marine environment
completes the picture of the weasel family's extraordinary diversity. Stemming from a common ancest-
or some 38 million years ago, family members evolved to utilize virtually every major type of habitat:
trees, the land surface, the subterranean, freshwater, and the sea. Only the air—the exclusive domain of
the bats among mammals—is denied to this amazing family!
