Animal Spotlight: Polar Bears

Taxonomy:hailer4hr

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Mammalia
  • Order: Carnivora
  • Family: Ursidae
  • Genus: Ursus
  • Species: Maritimus

 

  • Average Shoulder Height: 3.5 to 5 ft (1 to 1.5 meters)
  • Average Male Weight: 775 to 1,200 (351 to 544 kg)
  • Average Female Weight: 330 to 650 (50 to 295 kg)
  • Lifespan: 20 – 30 years
  • Status: Vulnerable
  • Estimate Population: 20,000 – 25,000

Polar bears are solitary, nomadic, Arctic carnivores that live within the Arctic Circle which includes the countries: Canada, Russia, United States (Alaska), Greenland, and Norway. Around 60% of Polar bears can be found in northern Canada. They are found at low densities throughout the circumpolar Arctic and are more abundant in shallower, ice-covered waters nearby the continental shelf where currents or upwellings increases biological productivity. In the summer open water season, Polar bears may be found on land in higher densities. cater_cute_polar_bear-k2v-458111

Physical Characteristics/Adaptations:

Many of the polar bear’s physical adaptations help maintain body heat and survive in the icy habitat.

Polar Bears’ silhouettes are distinctly different than the other bears’. Compared to other bear species, they have more elongated muzzles and smaller ears. Their long necks enables their head to remain above the water when swimming and their bodies are long and tapered for swimming. Forepaws act as large paddles with the hind paws as rudders and can sustain a speed of 6 miles per hour. The bears’ flattened paws have webbing between their toes to help when walking on ice and swimming.

The footpads of a polar bear’s paws help provide traction on slippery ice. Covered with small, soft bumps called papillae, the paws can grip the ice and keep the bear from slipping. Tufts of fur between their toes and footpads along with its claws are additional adaptations to help walk on the Arctic ice.

From a distance it may seem that the polar bear’s fur is white. But the white is merely a result from light being refracted through the transparent hair strands. This adaptation aids the bears to stay camouflaged with the snow and ice surrounding them. In fact, their skin is actually black, evident only on their noses.

Polar bear bodies are also designed to conserve heat. Their small and round tails with their short tails help conserve heat. On land, the polar bear’s thick fur coat prevents heat loss. In fact, adult males can overheat when they run. Their thick layer of fat also keeps polar bears warm, acting as insulation to trap heat, particularly when they are swimming as wet fur is a poor insulator. The fat also increases the bears’ buoyancy when they swim.

Hunting and Diet:

polar-bear-3Polar Bears are the most carnivorous out of all the bear species, eating almost exclusively meat. Their primary food source is seals, eating mainly Ringed Seals but will also hunt Bearded Seals, Harp Seals, and Hooded Seals. Other possible food sources are fish, birds, reindeer, rodents, bird eggs, berries, and other vegetation if food is scarce. It is unlikely for polar bears to gain enough nutritions from a strictly terrestrial diet. They will also feed on carcasses of beluga whales, grey whales, walruses, narwhals, and bowhead whales if available.

When food supply is plentiful, polar bears eat more fat for its high caloric value and digest it more efficiently than protein. This helps them maintain a thick layer of fat for insulation and energy, needing 4.4 lbs or 2 kg of fat each day. That amount of fat equates to about 121 lbs or 55 kg of seal and provides about eight days’ worth of energy. Any meat left behind are scavenged by other animals.

Polar bears spend over 50% of their time hunting for food, but less than 2% of their hunts are actually successful.

Underwater, polar bears are able to keep their eyes open and hold their breath for up to two minutes, allowing them to catch their prey.

On land, polar bears used two main techniques. Still-hunting is when the animal will spend its time waiting next to a seal breathing hole until ambushing one when it emerged. Then polar bear will bite or grab the seal and quickly pull it onto land to kill and feed. The second consists of stalking and then chasing their prey.

Polar bears are also known to break into underground seal dens to hunt for seal pups. They are able to identify the dens by smell and other markers.

Threats:threats_section_image_c_www-jsgrove-com_wwf

Polar Bears were the first vertebrate species to be listed in 2008 by the U.S. Endangered Species Act as threatened by extinction. Threatened by changes due to climate change, oil exploration, and pollution while being over-hunted, polar bears were losing their habitat and their prey.

Rising ocean temperatures are causing the sea ice to disappear for longer periods during the late summer before returning. The increased time leaves polar bears insufficient time to hunt and causing malnutrition. More cubs are not able to survive to adulthood. Furthermore, the lack of ice forces polar bears to swim longer distances from the shore to reach the ice. Many bears die swimming and those that do survive struggle to find food. The lack of food increases chances of cannibalism.

Oil extraction increases the potential human-animal conflict. Contact with oil spills reduces the insulating effect of the bear’s fur. Ingesting the oil through grooming or eating contaminated prey can cause liver and kidney damage from toxicity. Furthermore, oil spills are not effectively cleaned or controlled, destroying the Arctic ecosystem and habitat.

Toxic pollution levels are increasing in the Arctic food chain. Since polar bears are the top predators, the bears are exposed to the pollution from consuming the seals. The toxic affects a wide range of biological functions. In some areas, the mother bears’ milk contains high concentrations of these chemicals. The milk can actually poison the cubs, lowering their survival rates.

Overhunting is also an issue for the polar bears. The International Agreement on the Conservation of Polar Bears allows the local people to use traditional methods and exercise their traditions to sustainably harvest the mammals. Quotas are set each year to be between 600 and 800 bears, about 3-4% of the estimated total population.

Sport hunting is only allowed in Canada and must be guided by local Inuit hunters. The numbers from these hunts are included within the annual quota and the decision is left to the communities whether or not they want to allow sport hunts. It can be a major source of income since there is a greater profit from sport hunting than selling the hide.

Conservation:pbilogostkpos1003

The Polar Bear Specialist Group and other world conservation organizations work with each of the countries to monitor and protect the polar bears.

This includes:

  • Assessment of subpopulation size and protection of future status
  • Monitoring harvest and other removals
  • Understanding movement and distribution patterns due to ongoing habitat changes
  • Documenting human-bear conflicts
  • Documenting trends in habitat use and availability
  • Documenting trends in pollution and disease

In order to:

  • Protect essential habitats
  • Manage sustainable harvest
  • Develop management strategies to minimize impacts of human activities
  • Ensure the active involvement of the local public living in polar bear areas in developing and achieving the goals of the action plan

Fun Facts:

  • Their scientific name suits their lifestyle well. Ursus maritimus means “sea bear” after being observed swimming in the Arctic waters.
  • There are 19 distinct subpopulation units within the species. Though limited, demographic and genetic exchange does occur. Changes due to climate change may alter the interaction among subpopulations in the future.
  • The fur is generally off-white, but does appear more yellow during the summer due to oxidation and at times can appear brown or gray
  • Polar bears can run up to 40 km/hr
  • They have blue tongues like the giraffe
  • Polar Bears play a significant role in the Arctic tribes’ cultures. The Sami people call the bears as God’s dog and the Inuit call polar bears “Nanuk”.
  • Russians call them the beliy medved (white bear) and in Norway and Denmark, the polar bear is called isbjorn (ice bear).
  • Polar bears have three eyelids used to protect the eyes from the elements

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    © rccarl

References + For More Reading

ICUN: Ursus Maritimus

Polar Bears

Marine Bio: Polar Bears

WWF: Polar Bears

US Fish and Wildlife Services: ECOS

NWF: Polar Bears

Polar Bears International

Polar Bear Facts

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One thought on “Animal Spotlight: Polar Bears

  1. Pingback: Animal Spotlight: Pink Fairy Armadillo – Animal Almanac

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