Biology Reference
In-Depth Information
Idaho-Montana border, where the last of their kind were exterminated over fifty years ago. By reintro-
ducing twenty-five to thirty grizzlies over the next five years, biologists hope eventually to see as many
as three hundred of the big bears inhabiting the area. With 5,700 square miles of designated wilderness
on public land in this region, it's the only remaining area in the lower forty-eight states capable of sup-
porting such a restoration. As with so many other endangered species, the fate of the grizzly rests on
the maintenance of adequate habitat.
Brown (grizzly) bear
THE POLAR BEAR
The extraordinarily barren, frigid world of the polar bear
(Thalarctos maritimus)
is nothing like that of
black or brown bears. It follows, then, that the polar bear is a vastly different bear from its North Amer-
ican relatives— indeed, from all other bears. Living in such a harsh environment requires the polar bear
to have numerous adaptations, some of which are truly amazing!
The polar bear's species name,
maritimus,
correctly designates it as the seagoing bear, a creature at
home not only along the ocean but in it, so its adaptations begin with this central fact of its existence.
Polar bears float easily and are powerful, almost tireless swimmers. Individuals have been sighted by
ships, miles from shore and swimming with apparent ease, in water so frigid that most creatures, in-
cluding humans, would perish in it within minutes. It even appears that these remarkable seafarers can
sleep while at sea!
The reason for this amazing endurance resides in the bear's underfur. This coat is so dense that it
traps a great deal of air, which lends its owner the buoyancy needed to swim long distances with such
ease. Perhaps even more important, it serves to keep water away from the bear's skin, thus effectively
insulating it from the icy ocean. Added to buoyancy and insulation, the polar bear's huge front paws,
