Species Profile: The Polar Bear

The Polar Bear is the largest land carnivore on Earth, only the Kodiak bear can rival it in size.

Polar Bear Sow In Alaska

Polar Bear Sow Near Kaktovik, Barter Island, Alaska. (Author: Alan Wilson – www.naturespicsonline.com. cc by-s.a. 3.0)

The polar bear is a carnivorous bear that’s also classified as a marine mammal because of its native dwelling place exclusively within the Arctic Circle, and surrounding land masses.

This is a large bear. In fact, it’s rivaled in size only by the Kodiak bear with some individuals weighing over 1500 pounds (700 kg).

Although polar bears share a common ancestor with brown bears, it has developed a number of distinct features to enable it live and thrive in the extremely cold Arctic environment. They sit right at the top of the food chain in that terrain feeding primarily off seals that they hunt from the edge of sea ice.

Polar bear fur is thicker than any other bear species to provide warmth: it covers even their feet. Though the fur appears white, it’s actually transparent. They have a thick layer of fat just beneath the fur to provide warmth, insulation, and buoyancy in the icy waters around them. Their narrow skull and long necks likely provides a more streamlined shape while in water.

These bears are excellent swimmers too with their large, flat, and oar-like front feet. Since they spend their entire life on sea ice, and moving across snow, ice and open waters, that explains their scientific name Ursus Maritimus or “maritime bear.”

There are 19 subpopulations of polar with three now in decline due to habitat loss caused by climate change. Also, polar bears were hunted on a large-scale for centuries until an international intervention took effect to protect this species. They remain an important spiritual, material, and cultural component of the lives of circumpolar peoples and their culture.

The IUCN classifies the polar bear as a Vulnerable Species.

Though Polar bears have black skin to absorb heat, their fur appears white to blend in with their environment.

1) Scientific Name

Ursus Maritimus

2) Scientific Classification:

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

3) Life Expectancy

The majority of these bears rarely live beyond 25 years but the oldest one in the wild died at age 32. However, a female captive recorded the longest lifespan ever of 43 years old.

4) Average/Maximum Length

As mentioned before, this is a large bear, actually the largest on Earth. Only the Kodiak bear comes close.

Males of the species are much larger than the females: as a matter of fact they can be double the size of the females sometimes. In addition, size varies largely depending on the locality of the bear population.

Adult males measure 2.4 to 3 meters (7 ft. 10 in to 9 ft. 10 in) in total length.

5) Average/Maximum Weight

In general, adult males or boars, weighs anywhere from 350 to 700 kg (772 to 1,543 lbs.). Whereas females (sows) are roughly half that size. But when pregnant, many sows easily weigh up to 500 kg (1,102 lbs.)

 The largest individual polar bear documented was a 1,002 kg (2,209 lbs.) boar shot at Kotzebue Sound, Northwestern Alaska in 1960.

6) Maximum Swimming/Running Speed

The polar bear is so unique because it moves very well on land and in water too!

They are excellent swimmers and they have adapted features for this trait. In fact, they often swim for days at a stretch non-stop.

For example, it’s on record that a female bear swam continuously for 9 days in the ice-cold Bering Sea for 400 miles (687 km) to reach ice that was far from land. Afterwards, she still swam another 1,100 miles (1,800 km). Unfortunately, she lost her young cub during this swim.

Polar bears can swim at up to 6 mph (10 km/h).

When walking, they maintain an average speed of about 3.5 mph (5.6 km/h), but they will easily reach 25 mph (40 km/h) when sprinting.

7) Interaction With/Danger To Humans

Generally, adult polar bears live solitary lives and they are not territorial unlike their cousins the brown bears.

These bears have a reputation for extreme aggression though they are cautious in confrontations, and will sometimes flee rather than fight or attack.

A polar bear that’s fed will rarely attack a human. The exception is, of course, a hungry polar bear. Owing to the general lack of frequent human interactions, a hungry polar bear is very unpredictable and will see a human as prey. Consequently, unlike brown bears that will maul a person and depart, polar bears will kill and sometimes eat the body!

 A Japanese wildlife photographer named Michio Hoshino, was pursued by a hungry male polar bear in northern Alaska but luckily he made it to his truck just in time. The bear was able to tear off one door of Michio’s truck before he drove off – Wikipedia

8) Reproduction Details 

Polar Bear Cubs

Polar Bear Cubs At Alaska (Courtesy: U.S. Fish and Wildlife Service, P.D.)

Polar bears court and mate on the sea ice in April and May. This is one of the few times when adults of both sexes congregate for the best seal hunting.

Males will follow the tracks of breeding females sometimes for over 60 miles (100 km) and then fight with other males fiercely for mating rights.

Polar bears are generally polygamous and the cubs in a litter may be from different fathers.

Fertilized eggs do not implant immediately but they remain in a suspended state till August or September. Within those months, the female will consume large amounts of food to build up her fat reserve. As soon as the ice floes break up in the fall, hunting must end.

Pregnant females then dig their maternity dens and enter into a hibernation-like state. Though they won’t sleep continuously like other hibernating bears, their heart rate slows down to 27 beats per minute from the normal 46. Also, their body temperature does not decrease at this time.

Polar bear cubs are born from November through February weighing less than 0.9 kg (2.0 lbs.) Litters can be as large as four cubs though just one or two is the norm. The mother and her cub(s) will remain in the den while the babies nurse till about mid-April by which time the cubs are already 10 to 15 kg (22 to 33 lbs.)

Cubs remain with their mother till about two and a half years by which time she will either abandon them or chase them away.

Young bears mature sexually at four to five years (female), and six years (male).

Adult male polar bears will occasionally hunt and eat polar bear cubs.

9) Diet/Hunting Pattern Of The Polar Bear

These bears are well adapted for their carnivorous diet as their 42 large and sharp teeth show. Their preferred prey are ringed and bearded seals. They use their long, slender muzzle and neck to search in the deep holes that seals hide in, while their powerful hindquarters allow them to drag massive prey.

The seals must come out of the holes at some point: whether to breathe or to rest on the ice surface and that’s when the bears have the best chance of catching them. One of their strategies is to lie patiently in wait by these holes. As soon as they hear the seals exhaling, they reach in with their sharp claws and drag the seals out. This technique is called still-hunting.

They’ll also consume smaller-sized walrus, carcasses of beluga and bowhead whales, and birds’ eggs. In the direst of circumstances a polar bear will even eat Styrofoam objects, plastic items, car batteries, ethylene glycol, hydraulic fluid, and motor oil.

They often engage in fights with brown bears over carcasses, though the brown bears usually win. Wolves such as the Arctic wolf (Canis Lupus Arctos) may kill and eat polar bear cubs.

 In one very unlikely situation, a wolverine reportedly killed an adult polar bear in a zoo by suffocating it with a bite to the throat.

10) Alternative Names

  • Nanook (Inuit)
  • Bélyj Medvédj, or the white bear (Russian)
  • Ours blanc, or white bear (Quebec)
  • Isbjørn, or ice bear (Norwegian-administered Svalbard archipelago)

11) Population And Conservation Status

A Starving Polar Bear

A Polar Bear In Svalbard Starving Due To Rapidly Melting Ice (Author:   Andreas Weith cc by-s.a. 4.0)

Their worldwide range covers parts of five nations: Denmark (Greenland), Norway (Svalbard), Russia, the USA (Alaska), and Canada.

In addition, these five countries are the signatories to the International Agreement on the Conservation of Polar Bears. This agreement outlines issues on combined research and conservation efforts for the well-being of these bears.

For now, there are 19 generally recognized subpopulations of polar bears. 13 of these are in the North American subpopulations that ranges from the Beaufort Sea to Hudson Bay and then east to the Baffin Bay in western Greenland.

However, as of 2014 out of these 19 subpopulations, three are declining, six are still stable, one is increasing in numbers, and nine have insufficient data.

The polar bear population is under serious threat from climate change (global warming) specifically the continuous melting of ice in the Arctic region. They also suffer from the effects of pollution, recreational hunting, and oil and gas exploration.

The IUCN lists this bear as Vulnerable and estimates a worldwide population of between 20,000 and 25,000 individuals. This is the working estimate biologists adhere to.

12) Ancestry And History

The English explorer and naval officer Constantine John Phipps was the first person to describe the polar bear as a distinct and separate species in 1774. It was also he that chose the scientific name Ursus Maritimus, which is Latin for ‘maritime bear.’

At some point, biologists placed it in its own genus, but evidence of fertile polar-grizzly hybrids and facts supporting the recent evolutionary divergence of both species, nullifies the argument for a separate genus.

The oldest polar bear fossil discovered so far is a 130,000 to 110,000-year-old jaw bone. It was found on Prince Charles Foreland in the Artic region in 2004. Apparently, polar bears changed their molar teeth from that of the brown bear about 10,000 and 20,000 years ago and they may have diverged from a population of brown bears in the Pleistocene Epoch.

 Polar bears frequently mate with brown bears especially during the warmer months and they produce fertile grizzly–polar bear hybrids.

13) Distribution And Habitat

The polar bear lives only in the Arctic especially at the edges of ice floes where currents and wind interact. This is the best spot to find seals. These bears will travel for travel thousands of miles yearly to find food. They are distributed throughout the Arctic region in Alaska, Canada, Russia, Greenland and Norway.

The polar bear lives in a marine environment and spends many months at a time in icy seas. Also, its preferred habitat is the annual sea ice that covers the waters over the continental shelf and the Arctic archipelagos. This region is referred to as the “Arctic ring of life”, and it has high biological productivity in comparison to the much deeper waters of the high Arctic.

References:

1. https://en.wikipedia.org/wiki/Polar_bear

2. https://www.defenders.org/polar-bear/basic-facts

Photo Credits:

1. https://en.wikipedia.org/wiki/Polar_bear#/media/File:Polar_Bear_-_Alaska_(cropped).jpg

2. https://en.wikipedia.org/wiki/Polar_bear#/media/File:Ursus_maritimus_us_fish.jpg

3. https://en.wikipedia.org/wiki/Polar_bear#/media/File:Endangered_arctic_-_starving_polar_bear.jpg