Polar Bear: Characteristics, Habitat, Reproduction, Feeding

The polar bear or white bear ( Ursus maritimus ) is a highly specialized placental mammal for living on Arctic sea ice. They belong to the Ursidae family, so they are related to brown bears. From these they separated approximately between 110,000 and 130,000 years ago.

Its habitat is within the Arctic Circle, encompassing the Arctic Ocean, the seas, and the land masses that surround it. Mainly due to climate change, the white bear has lost its natural niche. This has resulted in a notable decrease in the population, making it an endangered species.

The Ursus maritimus spends much of his time on the ice, so your body has developed various adaptations to survive in icy environments. Their fur is very thick and they have a layer of fat under their skin that provides warmth and insulation against low ambient temperatures.

They are carnivorous animals, feeding mainly on the fat of seals. It provides you with an important source of nutrients, which you will metabolize during the summer, when your opportunity for food decreases. In this way it will obtain the necessary energy to carry out its vital functions.

Evolution

The fossil record of the polar bear is difficult to locate, because when it dies, the vast majority of its remains can disappear in the ocean or under large blocks of ice.

The family Ursidae, to which the white bear belongs, separated from the rest of the carnivores more than 38 million years ago. The origin of the family Ursidae dates to around 4.2 million years.

Evidence is available to show that white bears branched out from a brown bear population group. This happened on the Siberian coasts, during the ice age in the Pleistocene. The oldest fossil record was found in the Svalbard archipelago in Norway.

The evidence indicates that the white bear was derived from the brown species, some of the latter are much more genetically related to polar bears than to those of the same species.

The mitochondrial and nuclear genome of brown bears native to the Alexander Archipelago of Alaska, shows a close relationship with white bears. This confirms the ancient relationship between these two species.

Recent research

The estimate of the time in which the divergence occurred between brown bears and white bears differs considerably. There are hypotheses that propose a separation between 250 and 200 thousand years. However, some recent studies show that this happened much more recently.

In 2004, in Svalbard, Norway, a jaw bone was found from a specimen belonging to the Ursidae family. This animal existed between 130,000 and 110,000 years.

This finding helped to elucidate the period in which the separation between brown bears ( Ursus arctos ) and polar bears ( Ursus maritimus ) occurred.

Using sequencing technology, the complete mitochondrial genomes of this bone structure were generated. The genetic maps were compared with that of today’s polar bear in Alaska and grizzly bears that inhabit the Admiralty Islands in southeast Alaska.

The results showed that the fossil DNA samples shared similarities with both species of bears. This primitive specimen was found to possess morphological and behavioral characteristics typical of white bears, but genetic characteristics typical of brown bears.

Danger of extinction

The Ursus maritimus  has been categorized by the International Union for Conservation of Nature as a specimen vulnerable due to the decrease in its population in its natural habitat.

According to figures from some international organizations, over the last 45 years its population has decreased by around 30%.

Not only have they decreased in quantity, but their body condition is being negatively impacted. In 1980, on average, a female weighed around 290 kilograms, while in 2004 her weight was 230 kilograms.

The World Wildlife Fund maintains that the white bear is an important indicator of environmental levels in Arctic ecology. In this way, the fact that this species is vulnerable to extinction is a serious sign that indicates the existence of problems in said ecosystem .

Causes

Climate change

Climate change results in the loss of the natural habitat of this animal. In Hudson Bay, due to the increase in temperature, the ice break is occurring 21 days earlier, compared to the date of this event 30 years ago.

Global warming is causing sea ice to melt, making it difficult to hunt the animals that make up their diet. When the summer period arrives, the bear has already consumed its fat reserve, thus creating high levels of malnutrition in the arctic species.

The decrease in ice cover forces the bear to swim greater distances in search of food, further depleting its nutritional reserves. Occasionally the drowning of the animal could occur during the long journey.

The poor feeding translates into a low reproductive rate in adult females and a higher death of puppies and youngsters.

In addition to this, pregnant females cannot build shelters for their young. If they do, the ice is so thin that it could easily collapse.

Contamination

Polar bear body tissues have high concentrations of polluting chemicals, such as polychlorinated biphenyl and chlorinated pesticides. The waters and the environment are contaminated by these toxic compounds, attaching themselves to the fats of the animals that live there.

These substances are scientifically associated with some birth defects, miscarriages of pregnant females, underweight puppies, and serious immune deficiencies.

The oil spill is another factor affecting this group of arctic animals. This not only pollutes the waters, but also directly affects Ursus maritimus.

If the fur of this animal is impregnated with this oily liquid, the insulating function of the hair would be practically reduced. This could lead to the death of the polar bear from hypothermia.

To try to remove oil from the body, Ursus maritimus licks its hair, ingesting portions of this chemical. One of the consequences of this would be serious damage to the kidney, creating fatal kidney failure.

Furthermore, the alteration of the natural environment could cause mothers to abandon their offspring prematurely and even permanently. This would cause the almost immediate death of the young.

The hunt

Traditionally, the Eskimos hunted white bears for their fur and for their meat. The European settlers also did it for sport or to avoid their incursion into the populations.

Currently, man indiscriminately hunts the polar bear. Despite the fact that this activity is prohibited, their skins, legs and nails are traded on the market. Even openly in some countries the service of tanning bear skins is offered.

Conservation measures

In 1973, the governments of Canada, Norway, Denmark (Greenland), the United States, and the Soviet Union (now the Russian Federation) signed an international agreement on the conservation of white bears. This document has been the basis of innumerable actions in favor of the defense of this valuable animal.

Worldwide, several environmental organizations have joined awareness campaigns aimed at reducing the human impact on Ursus maritimus populations . Currently Greenpeace is leading some of these activities.

This environmental group tries to get government authorities to consider the Arctic a world heritage site. Some scientists have proposed taking aerial tours by feeding polar bears. However, they also maintain that they are palliative options to the problem.

The solution is the creation of a true ecological conscience that takes actions in favor of the eradication of serious environmental problems.

General characteristics

Nose

The nose is sharp, which helps the animal to smell its prey up to almost 70 centimeters under the snow. White bears have a highly developed sense of smell, they can distinguish the smell from 1.6 kilometers away.

Snout

Polar bears have long snouts, an adaptive characteristic that allows them to hunt seals. As its snout is long, it can catch them in the water without the slightest resistance. Also the length of the structure allows cold air to heat up before reaching the lungs.

Eyes

The eyes are black and very small, compared to the size of its body. This may reduce the risk of being blind from snow. They have a nictitating membrane that surrounds the eye, so sunlight does not directly impact the eyeball. Although his vision is limited, he is able to identify colors.

Teeth

In its mouth there are a total of 42 teeth. Canines are sharp, powerful, and large. They use them to tear the soft parts of the meat. The incisors are small and deciduous.

Ears

The ears are short and rounded. This is probably an adaptation that allows the bear to swim for hours and even days. If your ears were long, it could allow water to enter the ear, damaging the ear canal.

Adipose tissue

White bears have up to 10 centimeters of fat, I feel this almost half of their total body weight. Apart from serving as protection against the inclement cold, it is a store of energy.

During the months of higher temperatures, the nutrition of these animals depends on this fat. This is because the seal hunt becomes almost impossible.

Size

Males weigh between 350 and 700 kilograms, measuring up to 3 meters. The females are smaller, presenting a remarkable sexual dimorphism. These weigh about 150 or 250 kilograms, with a maximum length of 2.4 meters.

Skin

Polar bears are protected from the intense Arctic cold by their fur, fur, and a layer of up to 10 centimeters of fat.

Polar bear skin is dense and black in color. On the outside it is covered with hairs that appear to be white, but are transparent. This is divided into two types: external protection and other insulators.

The protective hairs are rough, hollow and transparent. In addition to this, they are resistant to water, so it does not adhere to the fur.

The polar bear’s hair is not pigmented, adopting the tone of the light that illuminates it. In this way, at dusk or dawn, it may appear yellowish-orange. The shedding of the coat begins during the spring, ending at the end of the summer.

The males, on their front legs, have hairs much longer than on the rest of the body. This ornamental feature could have the same function as the lion’s mane; make yourself more attractive to the females of the species.

Extremities

Its limbs are very robust, with large legs, which makes it easier for Ursus maritimus to distribute its body load when walking on ice. It also helps you propel yourself while swimming.

There are papillae – also called dermal bumps – that cover the pads of the polar bear’s paws. These prevent the animal from slipping while holding firmly on the snow. Polar bears have partially webbed feet, allowing them to swim with ease.

The legs have soft pads, made up of small papillae called dermal bumps. Its function is to hold the animal firmly, preventing it from slipping.

Their claws are sturdy, short and not retractable. When walking they do so with their claws exposed, giving them a firm grip on the ice. They can also hold their prey with these, giving it a great advantage over other predators.

Good swimmers

Despite having a very heavy and corpulent body, the polar bear is an excellent swimmer. To achieve this, it uses its forelimbs, which are flat, similar to an oar. These are used as propellant structures during his swim.

In addition, the thick layer of adipose tissue allows it to float in the cold arctic waters. When swimming, this animal can reach a speed of 10 km per hour, while its average walking speed is 5.6 km / h.

The adaptations of their body allow them to survive, since they can move between the great masses of ice or reach the land. For this they can swim long hours, even for whole days.

This ability is also essential for their feeding, because it allows them to dive underwater to get closer to the seals and capture them.

A great environmental role

The white bear, within the food pyramid, is a predator located at the apex. Within the Arctic ecosystem, they are a keystone species. The researchers take their behavior as environmental signals from that region.

The relationship between seals and these animals is very close, so much so that the bear migrates from regions where it cannot hunt them or where the seal population has decreased.

It could even be said that Ursus maritimus could have influenced some specializations that differentiate Arctic seals from those that inhabit Antarctica .

The vast majority of the young of the Arctic species are born with a white skin, probably associated with the need to camouflage themselves from their predator. On the other hand, young Antarctic hatchlings have darker skin at birth.

When hunting and consuming their prey, polar bears sting and tear them. The remains provide food for a diversity of wild species, with whom they share their ecological niche.

Taxonomy

Animal Kingdom.

Subkingdom Bilateria.

Chordate Phylum.

Vertebrate Subfilum.

Tetrapoda superclass.

Mammal class.

Subclass Theria.

Infraclass Eutheria.

Order Carnivora.

Suborder Caniformia.

Family Ursidae.

Genus Ursus

Species Ursus maritimus

Habitat and distribution

The polar bear is distributed in the waters belonging to the continental shelf and the inter-island areas of the Arctic Circle, to the south of James Bay, located in Canada. Towards the extreme south, it is on the limits of the sub-arctic and humid continental climatic regions.

These regions, known as the “arctic life ring”, are biologically highly productive compared to the deep waters of the Arctic.

Scientific studies have organized the habitat of Ursus maritimus into 19 populations, distributed in four different regions of the Arctic. This in turn is found in Greenland, the Russian Federation, Canada, the United States and Norway.

Arctic ecoregions

The habitat of the white bear can be divided into four regions. They differ in geography, ice levels, status, and vulnerability to climate change.

Seasonal ice

It is found in Baffin Bay, South Hudson Bay, Davis Strait, Foxe Basin, and West Hudson Bay.

Every summer in these regions, the ice melts almost completely, which means that the bears have to wait until the fall, when they freeze again, to be able to hunt.

In these areas of seasonal ice, polar bears are threatened. This is because they are limited to hunting their prey, having to use their fat stores for nourishment.

Divergent polar ice

In these areas, ice forms all along the coast and then melts, especially during the summer.

As the ice retreats, this group of animals have two different behaviors: they stay on the ground waiting for winter to arrive and the cold mass returns, or they swim long distances to reach other areas that have ice.

In these populations, bears face several dangerous situations: long distances that they could swim, prolonged fasts and the presence of humans on the coast, who could hunt them to sell their fur.

The regions that make up this area are the Barents Sea, South Beaufort Sea, Chukchi Sea, Laptev Sea and Kara Sea.

Convergent polar ice

The convergent sea ice of the Arctic basin is formed locally and transported naturally from other regions of the Arctic. In this way it accumulates on the coast, giving polar bears easy access to the seals that are in the marine waters.

Bears have few threats in these areas, as food is plentiful. However, specialists predict that if global warming continues, in a not too distant time, populations could be significantly reduced.

The North Beaufort Sea Regions, East Greenland and the Queen Elizabeth Islands belong to this Arctic ecoregion.

Archipelago ice

Greenland and the islands in the Canadian High Arctic lie to the north, which means that sea ice exists throughout the year, even during the summer. This is favorable for these animals, as the prey that make up their diet are abundant.

The areas with these characteristics are the Gulf of Boothia, the Norwegian Bay, the Kane Basin, the Lancaster Strait, the M’Clintock Canal, and the Viscount Melville Strait.

Reproduction

Females mature sexually between four and five years, males begin to reproduce at six. Males are aggressive towards other males, fighting over a female.

Polar bears are polygynous, being able to mate repeatedly over the course of a week. This reproductive process induces ovulation in the female.

After copulation, the fertilized egg remains “resting” until August or September when it is activated and its development continues. During pregnancy, the female eats in large quantities, storing fat for later use.

At the beginning of winter, the pregnant female digs a cave in the ice. There you enter to enter a state of inactivity, where your heart rate decreases from 46 to 27 beats per minute. This is not a hibernation period, as your body temperature does not drop.

The gestation period lasts about 195 to 265 days. Between the months of November and February, the cubs are born. They remain together in the cave until mid-April, when the female opens the entrance. By that time, the puppy already weighs about 15 kilograms.

Feeding

Polar bears are carnivorous, predatory, and opportunistic animals. In their diet there is a favorite animal: seals. However, they can eat specimens such as reindeer, musk ox, eggs, birds, rodents, and crabs.

Also, depending on habitat variations, they may eat some berries, seaweed, Lyme grass, and plant roots.

When the white bear goes hunting a land species like the ptarmigan, they try to get as close as possible before attacking. Hoofed prey are generally cubs, young, old, or injured. As predators, they may consume dead fish and the carcasses of whales or other marine mammals.

Despite the fact that it can feed on a diversity of land animals , the metabolism of Ursus maritimus requires large amounts of fat, which is obtained mainly from marine mammals.

In the spring, white bears hunt white-beaked dolphins when they become trapped in Arctic ice. The remains are stored to be ingested later during the summer.

The white bear stalks the seals, ambushing them. If the prey is aquatic, these animals jump into the water, since they are excellent swimmers. They are even capable of killing beluga whales.

Behavior

Polar bears are not territorial. Although their appearance may be fierce, they are generally cautious, trying to avoid confrontation. However, during the mating season the males of this species tend to become aggressive, fighting with other males in order to mate with the female.

In general, they lead a lonely life. However they could play with each other or sleep cuddled. Puppies are very playful.

Young people tend to have some “friendly” fighting behaviors, considered as practices for future confrontations in the reproductive season.

To communicate they use various vocalizations and sounds. Females send warning signals to their young by wailing. Young people have wake-up calls that may vary in pitch and intensity.

When white bears are nervous, they snort, while growls, hisses and roars are used in situations where aggressive expression is required.

Polar bears are active throughout the year. The exception to this are pregnant females, who enter a state of lethargy, where their internal temperature does not decrease.

References

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