| Revision as of 15:51, 25 February 2002 view source64.180.177.xxx (talk)mNo edit summary← Previous edit | Revision as of 06:05, 11 July 2002 view source Daniel W. Koon (talk | contribs)1 edit *corrects myth --- see http://it.stlawu.edu/~koon/polar.html and the author's own published work cited therein --- about the optical properties of the hairNext edit → | ||
| Line 8: | Line 8: | ||
| ) | ) | ||
| The polar bear is instantly recognisable by its white coat. Unlike other arctic mammals it never sheds this coat for a darker colour in summer. Their hair is unpigmented and hollow, |
The polar bear is instantly recognisable by its white coat. Unlike other arctic mammals it never sheds this coat for a darker colour in summer. Their hair is unpigmented and hollow, like white hair in humans. | ||
| An interesting feature of the coat is that it appears black when photographed with ultraviolet light. A number of people have suggested that this is because the hairs channel the light to the black skin of the bear to help it stay warm during the cold, sunless winters. Measurements show, however, that the hairs strongly absorb violet and ultraviolet rays. This is why polar bear's pelt often appears yellow. | |||
| Bears are wonderfully insulated; they overheat at temperatures above 50 degrees F. | |||
| It is the most completely carnivorous member of the ] family and feeds mainly on ]s. Polar bears are superb swimmers and can often be seen in open water miles from land. They also hunt very efficiently on land due to their prodigious speed; they are more than capable of outrunning a man. | It is the most completely carnivorous member of the ] family and feeds mainly on ]s. Polar bears are superb swimmers and can often be seen in open water miles from land. They also hunt very efficiently on land due to their prodigious speed; they are more than capable of outrunning a man. | ||
Revision as of 06:05, 11 July 2002
The polar bear (Thalarctos maritimus or Ursus maritimus) is a large mammal of the order Carnivora, family Ursidae. It is a circumpolar species found in and around the Arctic Ocean.
Polar bear Ursus maritimus
(Public domain picture from U.S. Fish and Wildlife Service full size image)
The polar bear is instantly recognisable by its white coat. Unlike other arctic mammals it never sheds this coat for a darker colour in summer. Their hair is unpigmented and hollow, like white hair in humans.
An interesting feature of the coat is that it appears black when photographed with ultraviolet light. A number of people have suggested that this is because the hairs channel the light to the black skin of the bear to help it stay warm during the cold, sunless winters. Measurements show, however, that the hairs strongly absorb violet and ultraviolet rays. This is why polar bear's pelt often appears yellow.
Bears are wonderfully insulated; they overheat at temperatures above 50 degrees F.
It is the most completely carnivorous member of the bear family and feeds mainly on seals. Polar bears are superb swimmers and can often be seen in open water miles from land. They also hunt very efficiently on land due to their prodigious speed; they are more than capable of outrunning a man.
Polar bears are currently threatened, not mainly by hunting, but by habitat loss caused by global warming; for example, the area of ice covering Hudson Bay in Northern Canada in winter is shrinking, limiting their access to seal prey.