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Interesting Facts about Polar Bears

Polar bears are found exclusively in the Arctic regions, and are the apex predators of the region, and an integral part of the ecosystem.
The polar bear (Ursus maritimus) is native to the arctic circle and is closely related to the brown bear. These mammals are born on land, but spend most of their time in water. Over the years, polar bears have evolved and adapted to the extreme conditions of the arctic region.

Classification

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Ursidae
Genus: Ursus
Species: U. maritimus

Range and Habitat

Polar bears inhabit the Arctic Circle till Newfoundland in the south. While they spend a considerable portion of the year in water, the natural habitat of a polar bear is snow and ice sheers over water. Countries where these bears are found are, USA, Russia, Norway, Denmark, and Canada.
Compared to their closest relatives, the brown bears, polar bears are larger in size, and regarded as one of the largest carnivores on land.
Size and Weight
The adult male polar bears can measure up to 2.4 to 3 m (8-10 ft) in length, weighing between 350 to 700 kg (770 to 1,500 lb). Adult females grow up to 1.8 to 2.4 m (6 to 8 ft) in length and weigh around 150 to 250 kg (330 to 550 lb).
Given the temperature conditions they live in, it is essential that polar bears stay warm. The insulation is provided by the adipose tissue (blubber) under their fur that is 4 inches thick. The thick fur also serves as an insulating material for these bears having a layer base of underfur and an external layer made of guard hair.
Blubber and Fur
The guard hair are in fact transparent. Each hair shaft is free from any kind of pigments having a hollow inner core. When visible light falls on these hair, they reflect and scatter it, giving an appearance of the color white.
The skin of a polar bear is black in color which is underlain by a layer of fat. However, more than the thick fat layer, the layer of fur protects the bear from suffering heat loss.
Polar bears possess excellent swimming skills. Their paws have adapted to roam even on thin ice sheets. The paw pads are laid with dermal bumps called papillae which prevent the bears from slipping on ice.
Specialized Paws
Polar bears have mastered the skill of balancing their weight on thin ice sheets by spreading their legs wide apart so as to distribute their weight evenly. In order to distribute their weight while stepping on thin ice cover, the padded paws play a major role helping the bear stay put.

Hunting Prowess

As most other animals, the claws of polar bears are used for hunting their prey. The thick and curved nature of the claws helps in holding and gripping the prey. Polar bears have a well-developed sense of smell and vision aiding them in locating their prey from a distance of nearly a mile.
The 42 teeth that these bears possess have also been adapted to support their carnivorous diet. They are sharp to break down the meat of their prey.

Diet

The diet of a polar bear consists mostly of bearded and ringed seals. Seals, that are found aplenty in the Arctic region, fall prey to a polar bear when they surface to breathe. Polar bears use their sense of smell to track down a seal's breathing hole and wait for the seal to surface in order to breathe.
A polar bear has to wait patiently for days for a seal to rise from its breathing hole; sometimes even stalking a seal if it chooses to rest on the ice cover. A polar bear usually crushes open the skull of a seal by biting it before feeding on it. Sometimes, adult polar bears feed on the blubber of a seal while their young ones consume its meat.
Beluga whales, although rare, are a part of the diet of polar bears. They are also reported to consume reindeer, muskox, shellfish, and crabs.
The mating season of polar bears is between April and May after which the egg does not get implanted or stays in a suspended state until August or September.
Reproduction
This process is called delayed implantation. In the fall, the pregnant polar bear creates a maternity den for herself in the snow, going into a dormant state.
The cubs, usually two, are born any time between November and February. Cubs are born blind, are 12 to 14 inches in length, and weigh around one pound.
The mother stays in the den with her cubs until April, during which she fasts the entire time. After about 8 months of fasting she emerges out of her den and 12 to 15 days later, takes the cubs along for seal-hunting.
Usually in lower arctic regions, the cubs are weaned after a couple of years, whereas in the higher arctic regions weaning takes place mostly after three years.
Research states that the population of polar bears is around 20,000 to 25,000. Owing to climate change, the IUCN has listed the polar bear as a threatened species in the United States.

 Yogesh Ambekar

Credits
Hans-Jurgen Mager, Bao Menglong, NOAA