- Polar bear (Ursus Maritima) -

Class: Mammalia

Order: Carnivora

Family: Ursidae

Genus: Ursus

A) Habitat and dangers for its species.

This great polar bear is the largest terrestrial carnivore of the world and it's the only fully adapted to the polar climate of the Arctic Sea.
It lives in all the polar regions of Canada, Alaska, Greenland, Svalbard Islands (Norway) and Russia but its population is decreasing; today, only 20-25,000 individuals, living in 19 sub-populations, should exist.

They like better to live at the margin of the polar ice pack, where the ice meets the sea, to find easily the seals that are its main food. During the summer, the ice melts totally near the coasts of the islands and of the continent, the seals migrate southwards toward the coasts and the polar bears must follow them. So, they must spend the whole summer on the land, waiting the freezing of the sea to come back on the ice pack. Here, they are sometimes obliged to live near the towns looking for food in rubbish discharges, as it happens near the Canadian town of Churchill, along the Hudson Bay.

Their life is more and more threatened by pollution of industrial origin that weakens their immune system and reproductive ability and that also comes from oil extraction in polar regions.
The most dangerous factor, maybe, is the global warming that is quickly reducing the Arctic pack surface, in summer and in winter.
Today, the polar bear is protected from hunting, after having been systematically killed until the 1970's but, now, its whole environment needs protection too and this is the hardest challenge to face.

B) Physical features.

The polar bear keeps its white fur for the whole year to better camouflage on the ice; this fur is white because not pigmented, transparent and hollow, while the skin is dark to better absorb the scarce solar light, when necessary.

It has two kinds of fur: an inferior dense layer of under-fur and an outer one (guard hairs), 5-15 cm (2.0-5.9 in) long.

The male weights up to 350-680 Kg (770-1500 lb) and, when standing up, it can reach 3.0 m of height. The female, instead, weights only 150-250 Kg (330-550 lb) and, at their birth, polar bears are immature and weight only 1 Kg.

Respect to the more southern brown bear, the polar bear has a more slender body and head, much larger paws to better swim and walk on ice and distribute its weight on a wider surface when it walks on thin ice. Moreover, its ears and tail are smaller and rounder to disperse less heat from

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