Polar Bears

Ursus maritimus

Weight:

350 to 800kg (5 to 9.5 lbs)

Size:

2 to 3 m
Mammals
Carnivore
,
Omnivore
,
Piscivore
Polar región

Interesting facts

They are the only bears classified as marine mammals. Most of a polar bear's diet comes from the sea, although they don't hunt directly in the water! 

Conservation

Vulnerable

The polar bear has the typical shape of other bear species. However, they have some physical features that show how they have adapted to aquatic and arctic environments: white fur, small ears to reduce the risk of freezing, and webbed front paws to make them stronger swimmers.

Environment and behavior

Although they are solitary creatures, the male and female can be seen together during mating season or a female can be found with her cubs.  They are also found in groups when food is abundant (large colonies of seals, whale carcasses, etc.).  Polar bears spend much of their time on the ice, but are also found in areas without snow.  Mating occurs from April to June. The first mating triggers ovulation in the female.  She will then have to mate with another male to be fertilized.  Males may be aggressive towards each other when trying to court a female.  Each male may mate with one or more females. After fertilization, there is a delayed implantation period of about 5 months (April to August), in which the female must gain up to an additional 150 kg (330 lbs) to enter the embryonic development phase (September to November).  Some time before giving birth, the female creates a den. Two cubs (occasionally 1 or 3) are born between December and January.  The mother provides extremely rich milk thanks to her 4 nipples.  At birth, cubs are approximately 30 cm (1 ft) long and weigh 600 g (21 oz).  After 4 months in the den (December to March), they begin to explore the area around it.  A few weeks after their first outing, the mother goes hunting to regain weight, followed by her young.  By that point, she will have lost 40% to 50% of her total body weight. This is also when polar bears start to shed their fur.  The cubs will stay with their mother for 2 to 3 years.  They are weaned in March, just before a new mating period for the female.  Polar bears have one of the slowest reproduction rates of all mammals. The females generally have only five litters during their lifetime.

 

Predators

Polar bears have no natural predators, other than mankind…

Threats

Illegal hunting, the exploitation of Arctic resources and the fact that the polar bear is at the top of the food chain and accumulates toxins (heavy metals, PCB, etc.) in its tissues, are all exerting pressure on its populations. However, global warming, which extends the ice-free period and at the same time restricts access to seals, seems to pose the biggest threat.  This results in nutritional stress and an inability to store enough fat to survive the ice-free period.  The consequences of this decrease in fat reserves are: poorer physical condition, a lower reproductive rate, reduced cub survival rate, and moving closer to areas occupied by man and thereby running the risk of being killed.  Within the next 100 years, if polar bears don't adopt feeding behavior similar to that of brown bears, they may well disappear.

Habitat

Durant l’hiver, l’ours vit sur la banquise (eau de mer gelée). L’été, il vit près des côtes ou sur les îles de l’océan Arctique.