Chapter 9: Polar Bear

 

 

 

Polar bear mother and half-grown cubs come ashore in summer to search for food. Coastal tundra of northern Canada. From: Bernard Stonehouse, Animals of the Arctic the ecology of the Far North (1971:18 ) Photo: Breumer.

 

 

Dough Lindstrand’s Alaskan Sketchbook (1981:88): The Polar Bear in Alaska, by Jack Lentfer, Alaska Department of Fish and Game, Wildlife Notebook Series:

 

“Adaptations by the polar bear to life on sea ice include a white coat with water repellent guard hairs and dense under fur, short furred snout, short ears, specialized teeth for a carnivorous rather than an omnivorous diet and hair nearly completely covering the bottom of the feet. An extremely large adult male may weigh 1,400 pounds (635 kg). Most mature males weigh between 600 and 1200 pounds (272 and 544 kg). Mature females weigh 400 to 700 pounds (181 to 317 kg).

 

Pregnant females seek out denning areas in late October and November. Most denning occurs on land but there is also a certain amount on heavy sea ice. A denning female commonly forms a depression in the snow under a bank or on a slope where snow will drift. She enlarges the denning chamber as snow drifts over her. Young are born in the den in December. A litter of two is the most common, one is quite common and three is rare. The female and cubs break out of the den in late March or early April when cubs weigh about 15 pounds. They make short trips to and from the open den for several days as the cubs become acclimated to outside temperatures. They then start travelling on the drifting sea ice. Young most commonly remain with the mother until they are about 28 months old.

 

Polar bears are most abundant near the southern edge of the ice but do occur throughout most of the polar basin. They make extensive north-south movements related to the seasonal position of the southern edge of the ice. In winter, bears off Alaska commonly occur as far south as the Bering Strait and occasionally reach St. Lawrence Island and even St. Matthew Island in the Bering Sea. In the summer north of Alaska, the edge of the ice pack and bears occur between 71 degrees and 72 degrees north latitude. Pregnant females concentrate for winter denning on large offshore Russian islands, northern Canadian islands and certain of the Spitsbergen Islands. There is a limited amount of denning along the north Alaska coast. Mark and recapture studies indicate that there are several populations of polar bears in the polar basin which have little or no interchange with each other.

 

The main food of polar bears adjacent to Alaska is the ice-inhabiting ringed seal. Bears capture seals by waiting for them at breathing holes and at the edge of leads or cracks in the ice. They also stalk seals resting on top of the ice and catch young seals be breaking into pupping chambers in the snow on top of the ice in the spring. Bears feed to a lesser extent on bearded seals and carrion, including whale, walrus and seal carcasses along the coast. In other areas they feed on harp and bladdernose  seals. They occasionally eat small mammals, bird eggs and vegetation when other food is not available. A keen sense of smell, extremely sharp claws, patience, strength, speed and the camouflaging white coat aid in procuring food.” – Jack Lentfer.

 

 

Grzimeks Enzyclopädie, volume 3 (1988) Munich, By Fred Kurt, Bernhard Grzimek and Victor Zhiwotschenko:

 

 

Polar bear

 

"The polar bears will usually leave already in December the floes of the drift ice and walk from there to the mainland or to one of the smaller islands, off the arctic coast. This journey is very cumbersome for them. There they will go to the place, where they will stay during the winter. There they then dig through snow and ice and often also through the frozen ground a cave. This cave is up to 5 meters long, and at its end there is a kettle (hole). It is two meters wide and two meters long.

 

But during this time, when the polar night covers the arctic and when the polar bears are resting under fresh snow and eternal ice, a new bear generation is born. The polar bear mothers, weighing 300 kg, give birth now to cubs, which are only as large as a rat.

 

The powerful body of the mother warms up her cave. Near the end of November and the beginning of December, the tiny cubs are born. Then the mother keeps her tiny cubs warm in her thick fur-cover: She then puts them beneath her upper arms.

 

The cubs grow rapidly: In March they weigh already several kilograms. Now the mother will soon dig two holes through the roof of their underground dwelling. Then she takes her children outside for a short time. And soon they have to leave their winter-den. The way to the sea, the most important hunt ground of the polar bears, is sometimes very far. On the Russian Wrangel Islands and in the Canadian High Arctic 8-22 kilometers lie between the caves, where the cubs were born, and the coast. In the area of the Hudson's Bay they may have to walk 70 kilometers." (1988:481, 482)

 

Table, P. 498: Polar bear (Ursus maritimus): 320-410 kg, males occasionally up to 1000 kg.

 

 

Grzimeks Tierleben  volume XII (1972) Zürich: 

 

The polar bear by B. Grzimek and A. Pedersen in co-operation with W. Heptner and S. Uspenski

 

"Body weight: 320-410 kg (in the Siberian Arctic in rare cases up to 1000 kg, when very fat. The toes up to their half length are connected with a swimming skin. The soles of its feet are covered with hair, only the soles and toe-balls are not covered by hair. 

 

The hair-cover of the polar bear has the special characteristic that water runs off from it very fast. Thus the polar bear is excellently adapted to its habitat, to the seas of the northern hemisphere of the earth, which is covered with drift ice; only temporarily one finds it on land.

 

Until recently scientists thought that he is the most untiring wanderer of all arctic land mammals, who all the time moves with the ice-drift in an east-west direction around the North Pole, while looking for areas, where there are many seals. But according to new research, there are many populations of polar bears, which stay within their home range. According to Uspenski, one most often finds the polar bears, where there is open water; because there it is easy for him to hunt the seals. That is why the bears do prefer in winter, to stay near the southern rim of the drifting ice-fields. That is, near a strip of ice-free water, which in high latitudes forms in the Arctic a ring-like system. In summer, when the ice-fields become smaller, the bears are more evenly distributed.

 

On our maps they have usually drawn the Arctic far too large. Actually, the area of the Arctic Ocean is smaller than Europe. Hence, the polar bear does not have such a large home-range at all. Its actual homeland is the small hilly arctic islands, which lie within the area, in which it hunts. Here the pregnant she-bears gather in autumn. There they dig their cave into the snow and give birth to their cubs. In some areas of the Far North, all polar bears do have a kind of winter-sleep (hibernation), just like the brown bear, usually in a den in the snow. It always lies within a snow-drift near the coast, on the side, which is protected from the wind. In other areas, also on the Siberian Wrangel Island, only expecting mothers will sleep in a den. When the bear has dug itself into the snow-drift, the falling and drifting snow will cover his den completely. So all traces will disappear, which could betray his place of residence. 

 

Such a den consists of a long tunnel, two to three meters long, sometimes also five or six meters long. This depends on the amount of snow, which has collected there during the winter. At the end of this tunnel there is a large cave of oval form. It may be two and a half meters long, one and a half meters wide, and one and a half meters high. If a female bear stays there over the winter with half-grown cubs, her den will be that much larger. Even when it is very cold outside, the temperature in the cave will stay near the freezing-point, from the heat, which the bear produces. At the beginning of March most polar bears will again be outside in the open. But some of them wait until April, before they leave their winter-den.

 

Soviet zoologists have studied the polar bears, which live on Wrangel Island. In winter this island has about hundred fifty caves. In winter the animals will come there to the same holes in the ground and cracks in the rock. Generally one can say: The further north the area lies, and the colder the weather is, and the more difficult it is, to find enough to eat during the winter months, the more bears, independent of their sex, will build a cave. On the other hand, all pregnant females in all parts of the Arctic, wherever they may live in winter, will sleep in their dens. The males and the non-pregnant females will stay in their snow-caves only so long, until it gets a little warmer. Then they will continue their migrations, regardless of the time of the year, to look for prey.

 

The cubs, usually two, rarely one and seldom three, are usually born in the middle of the winter, mostly in the first half of December. They are helpless, deaf and blind. During the whole winter the mother does not eat any food. She lives then only from her own body reserves. On Wrangel Island the bear mother leaves with her children her winter den during the first days of March. During the first days she still remains near her cave. And at night they will sleep in their snow-cave. When there is even the smallest sign of danger the whole family hides itself again in the cave.

 

At first, when the polar bear mother has left her den, she will catch mainly newborn seals. Also her cubs will feed on them. Often she interrupts her walking-tour and lays down in the protection of an ice block. Here the cubs creep between her front and hind legs, they suckle and find there a warm bed, in their mother’s fur. Into the water the polar bear mother will go with her cubs goes only after their first winter, and then only if this is necessary. She also avoids it to come on land, to come ashore, and even close to it, because the dangers for her cubs is there greater than on the ice; the mother-bear would find it difficult, to protect her cubs against the wolves.

 

Under the care of the bear mother the cubs grow up fast, so that she can move around then again normally. She stays far away from the coast. And only rarely will she spend the first summer on an island or at the coast of the mainland. With the polar bear populations, which remain permanently within their home range this is different. At the beginning of the next winter she digs again a snow-cave for herself and her cubs. Her cubs are then about as large as a shepherd dog. And during this winter they lose their milk-teeth and get their permanent teeth. When this winter-sleep has ended, they will be able to survive already on their own. But their mother must still guide them, so that they will develop normally. They take part now actively, when their mother hunts. They follow her, when she sneaks up to her prey, the one cub behind the other one. They imitate now all of her movements. She still suckles them, when they are one and three-quarter years old.

 

Near the end of their second year of life the family dissolves. But there are cases, where the mother will also stay with them together during the second winter in her cave. But soon after this each adult polar bear will go its own way.

 

Apart from the mating times and the years of the 'family life', the life of the polar bear is quite monotonous. Their favourite prey is young seals, in the spring above all newborn ringed seals.

The polar bear keeps his head down low and walks quietly; he looks over the snow surface, especially near the mouth of glaciers and near icebergs and at similar places, where there may be the caves of seals. He either crawls very slowly on his belly toward the sleeping seal and kills it with one stroke of his paw. Or he very carefully slips into the water, backwards, with his hind legs first. Then he swims toward his prey. The last part he swims under water. When he has reached his prey, he jumps out of the water onto the ice, and cuts off its way back to the sea. He may also wait patiently at the breathing hole of the seals. When the seal comes up to inhale fresh air, he knocks its head against the rim of the ice-hole.

 

In spring the polar bear is mainly interested in young seals, and later on also in adult seals on drifting ice, when they change their hair-coat. In winter he will nearly only eat the fat, which he tears off in large strips, and the intestines, which are his favourite food.

 

In the middle of summer, when most of the seals of changed their hair-coat, many polar bears will begin to eat anything they can get, because they find then so little to eat. Only rarely they will try to attack larger mammals like the musk-ox and the reindeer. In years, when there are many lemmings, he will also hunt these small rodents, by turning over stones and even large rocks. Then he kills the lemmings, which try to run away in all directions, with quick strokes of his paws. Salmon and other fishes he will try to catch in shallow water. With a quick stroke of his paw he throws them onto the bank. He will also feed on the bodies of large marine mammals (like stranded whales). And in summer he likes to eat blueberries, crowberries and other plants.

 

The polar bear does not hunt its prey in the water, but he swims well. He is able to swim long distances from one ice-floe to the next one or from the coast to the edge of the ice. When he dives, he is able to stay about two minutes under water; but he seldom dives down deeper than one or two meters.

 

Usually the polar bear disregards human beings. These bears regard human beings neither as prey nor as opponents; they only want to be left alone, so that they can catch seals and other animals." Grzimeks Tierleben volume XII (1972:128 136)

 

 

Ringed seal resting on the rocky shore. The fawn rings characteristic of the species can be seen on the flanks. This is the commonest and most widespread Arctic sea. The polar bear hunts mainly the ringed seal. From: Bernard Stonehouse, Animals of the Arctic the ecology of the Far North (1971:67 ) Photo: Nat. Film Board of Canada.

 

 

On 30. 12. 2003 the Second Channel of German Television at 20:15 o'clock showed the documentary film Ice-cold paradise, by Adam Ravelch. On Southampton Island in the north of the Hudson Bay:

 

"Southhampton Iceland in the north of the Hudson Bay is enclosed 9 months in the year by the ice. 

 

A female polar bear with two cubs. After 4 months of winter-sleep the mother is very hungry. For 3 years the polar bear babies will remain under the care of their mother. They will open their eyes, when they are 14 days old. They do depend completely on their mother.

A polar bear above the breathing-hole of a young seal.

A polar bear at the carcass of a whale.

A mother polar bear with her two cubs at the carcass of the whale. 

A male polar bear at the carcass of the whale.

A mother polar bear with her 2 cubs and a male polar bear at the carcass of the whale.

 

How one is able to sneak up close toward a seal: The sun must be in the back. One must move against the wind, and one must walk quietly.

 

In the summer, when the ice has melted way, the walruses come ashore.

 

A polar bear in summer. It is able to swim several days in a row in the open sea, hundreds of miles away from the shore. He must know, where there are islands, where they are located, on which the walruses in summer rest themselves. Such an island is like a needle in a hay-stack.

 

A polar bear on such a small island. The walrus is not its usual prey. Usually the polar bear lives on seals.

In summer the polar bear also lives on berries, shell-fish and sea-seaweed.

 

Caribou on Southampton Island in summer." by Adam Ravelch, Second Channel of German Television 2003, end

 

 

On 29. 01. 2004 the television station Phoenix showed at 20:15 o'clock the documentary film Closer to the Ice Cap. With the ice-breaker through the Arctic. By Brenda Goldblatt and Jeff van Reemen:

 

Map of the polar ice.  The first encircling of the northern ice cap. They start in Spitsbergen.

 

The Arctic Ocean is nearly completely covered with pack-ice. Only in the summer, in July and August, the several meters thick ice breaks up at some places and swims around then as drift ice. It is up to 6 meters thick.

 

Near Spitsbergen in summer.

The Greenland Sea at -10°C, a polar bear at the ship.

During the arctic summer the sun shines up there for 24 hours.

The polar Ice Cap has a circumference of 24,000 km.

 

If there were no Ice Cap, these plants and animals would have to survive then without this ice. Then there would be no food-chain like today: from the algae to the invertebrates, to the vertebrate animals, the fish, seals, walruses, whales and polar bears.

 

A polar bear at the west coast of Greenland in summer. The ice is the dwelling and the nursery of the seals. The polar bear lives on the ice, because it lives there on the seals.

A polar bear on the pack-ice in summer, at the west coast of Greenland.

 

If the ice shrinks, the whole food chain is reversed. The Greenland ice-sheet is on the average 8 km thick.

 

A female polar bear with 2 cubs on the pack-ice, off the coast of West Greenland in summer.

 

The white fur of the polar bear is not white, but colourless. It allows the rays of the sun to go through this hair into the skin beneath it.

 

The polar bear children will remains during the first 2-3 years with their mother. Their mother teaches them how to hunt, and how they will be able to survive up there or also not. The natural selection is great. Every second young polar bear will not be able to survive in this environment.

 

Baffin Iceland, Nunavek, Canadian territory in autonomy.

Devonian Island, Nunavek. Musk-oxen

Victoria Island, Nunavek. 

 

Herschel Island, Canada. The willow shrubs up there are only 5-10 cm tall.

Bering Strait

Taimyr Peninsula

October Revolution Island, polar bear on Severnaya Semlya.

In the Arctic, in August it is already late autumn.

 

End of quotations. By Brenda Goldblatt and Jeff van Reemen.

 

 

On 3. 1. 2004 Bavarian television station BR showed at 19:00 o'clock the documentary film Spitsbergen, Svalbard  – In the realm of the polar bear. By Bo Landin:

 

Svalbard, Spitsbergen, 60% of it is covered by ice. 120 days in the year it lies in the arctic darkness.

 

A female polar bear in spring comes out from her cave, in which she has slept during the last winter.

For 2 ½ years the cubs will remain with their mother.

A female bear after her winter-sleep with 2 cubs.

The female polar bear in her winter-cave, she has not eaten or drunken anything. She recycled the water in her body. Her metabolism recycles the liquids.

A female polar bear suckles her cubs.

At first they are only as large as a rat. Now, when they come out from their snow-cave, they weigh 10 kg, due to the fat milk of their mother.

The polar ice cover nearly reaches Svalbard.

The polar sea is one of the most productive seas of the world. 

The sun shines there in the summer 24 hours per day and the rock-meal (powdered mineral soil), which the glaciers have ground down, supplies the Arctic Ocean with important minerals.

In summer there develops an unbelievably thick alga soup. Smaller animals live on it. The krill in the alga forest forms the basis, the beginning of the polar food-chain.

This krill nourishes also the whales and the polar bears. Ringed seals are the basic food of the polar bears. Therefore the polar bear lives mostly on the pack-ice.

 

If the cubs are large and strong enough, the bear mother brings them out onto the ice, so that they will learn there, how to eat meat. The polar bear finds the seals with its excellent sense of smell. The polar bear descends from the brown grizzly.

 

A sea-weed forest in the Arctic Ocean near Svalbard. The cold water is rich in nutrients. It contains many suspended particles. They come from the glaciers.

The seaweed forests are the breeding places for countless organisms. This submarine kindergarten forms one of the bases of the rich life in the sea all around Svalbard.

 

Seaweed forest, sea anemones, and shell-fish.

The sun shines now around the clock, and the temperature of the air lies now for several months a little above the freezing point (5°C).

 

In the summer: Most polar bears have moved out onto the sea and follow the retreating pack-ice. Whoever remains behind, will find it more difficult to survive. He must hunt then during the summer on the rocky coast. But here it is for the polar bear more difficult, to find enough to eat. Usually he does not bother with the reindeer. On Svalbard there are no mice and no lemmings.

 

Polar bear with a seal. 

One is only able to survive in the Arctic, if one puts on enough fat.

The polar bear is only able to survive, if he eats enough fat seals..

On Svalbard the winter begins in August.

The lonely male will wander during the winter through the Arctic on the ice cover of the polar sea.

The female bear digs for herself in the snow a winter-cave, she will sleep in it during the winter.

 

 

Polar bears are strong but clumsy swimmers and wander widely over the sea ice. Walking and swimming, they visit all the northern islands. King Karl’s Land, Svalbard. From: Bernard Stonehouse, Animals of the Arctic the ecology of the Far North (1971:71). Photo: Breumer.

 

 

On 27. 12. 2003 the television station RBB (Berlin) showed at 14:15 o'clock the documentary film Spitsbergen. Surviving in the pack-ice. By Udo Bliss:

 

No tree, no bush.

Greenland huskies and a German shepherd dog.

A hunter of fur-bearing animals on northern Spitsbergen. In winter it gets there very cold, down to -40°C.

Carcasses of seals in a cache. The temperature up there in summer rarely rises above 5°C.

A polar bear in the snow. It tries to approach the cache with the seal-carcasses.

 

During one winter a large polar bear besieged for 4 days the weather station of Spitsbergen. He wanted to get to the cache (supply rack), to fetch the seal carcasses. Then the scientists shot him. He was 4 m long and weighed 850 kg!

End of the quotations.

 

 

On 2. March 2003 the television station 3SAT showed at 20:15 o'clock the documentary film: Siberian Arctic, Wrangel Island, by John Sparks, BBC, Natural History Unit:

 

On Wrangel Island, the realm of the polar bear, it is for several months night. And there is frost, down to -50°C. At the end of January the polar night is over.

 

The snow-cover protects the pregnant polar bear. The female polar bear comes out from her winter-snow-cave. She shakes out the dry snow from her fur-coat. It has not thawed.

In the middle of March, when the mother with her cubs leaves her snow-cave, it is still -35°C cold.

 

The female bear is able to stay warm through her thick hair-coat and her thick layer of fat. Since October she has slept under this snow-cover. At the end of December she gives birth to her nearly naked cubs in her snow-cave. They are only as large as a rat. She feeds them with her fat milk, and they grow up fast.

 

A female polar bear and one of her two cubs in front of her winter-cave on Wrangel Island. She suckles it. In a few weeks the cubs will be able to follow their mother down to the pack-ice, to hunt seals. Until then they remain in their cosy snow-cave.

 

The female polar bear with her two small cubs in front of her snow cave. The cubs continue to grow and to become stronger. They spend now ever more time outside.

 

Each year about 200 female polar bears give birth here to their young in snow-caves.

Toward the end of the winter these female polar bears leave their den. They move to the Arctic Ocean, which is still covered by ice. The polar bear mother leaves now with her two cubs their winter cave.

 

In the Russian Arctic about 10,000 polar bears are living. That is about a third of the entire population on earth.

 

In the summer the tundra thaws there at the surface to a depth of only 15-30 cm.

 

A polar bear mother with her cub on the pack-ice off Wrangel Island.

 

A polar bear with walruses at the beach of Wrangel Island.

 

In this year there are many polar bears and walruses at the beach of Wrangel Island. Because in this year the pack-ice has melted more strongly than usually. This happens only every 10 years.

Since there are now no ice-floes, the walruses and polar bears have to stay at the sea-shore.

 

This polar bear has just killed there a young walrus.

 

In October the pregnant polar bears climb up onto the mountain slopes. There they will spend the next 5 months.

 

A pregnant polar bear in October at the mountain-slope.

 

She just lays down at the mountain-slope on the broken rocks and begins to sleep. She does not dig there a cave, neither into the ground nor into a snow-drift. She simply lies down there and waits, until the snow, which falls down, covers her.

 

The male polar bears. and not the pregnant female polar bears, in the area of Wrangel Island do remain nearly during the whole winter active. The temperature sinks down to -50° C. Until the end of January the sun will not be seen there anymore.  – End of the quotations.

 

 

Surviving in the white wilderness, Franz-Josef Land, by Anne Macloid, in 3SAT:

 

Franz-Josef Land lies east of Spitsbergen. There the polar night lasts until the end of February. Starting from April the sun does not go down there anymore. Until the end of August she shines there 24 hours per day. Nevertheless, a thick ice-cover continues to cover the sea until July. Only from July onward the Polar Sea is there open again.

 

Polar bear: A thick layer of fat and hair-coat are superior to any polar suit.  

 

The water contains much phosphorus and nitrogen: On them the algae live. On the algae the zooplankton lives. On these the crustaceans nourish themselves. On the crustaceans the fish, seals and polar bear are living.

 

Ringed seal on Franz-Josef Land.

 

In summer many male polar bears move back and forth between East Greenland and Franz-Josef Land. That is about 1200 km. They look for fodder and females. That is a population of about 5000 polar bears. When searching for fodder and females, they also roam across the islands of Franz-Josef Land.

 

A polar bear on the ice. Each individual hair is translucent and leads the light of the sun directly to the body. There the skin then absorbs this light.

 

If two males meet one another, they do not evade each other. They will fight then with one another, until one of the rivals gives up.

 

Two males are fighting. Because only one of three existing female is available for the mating. The others females have cubs. The cubs will remain 2 ½ years with their mother. During this time she does not mate.

 

In order to find a female, male animals cover large distances. Sometimes 1500 km within one year.

 

Ice algae, red and green ones, grow on the snow.

In the summer the water temperature of the Arctic Ocean lies under the freezing point. Then the water is richer than anywhere else.

 

The polar bear can smell well. On the ice it can smell the breathing-hole of a seal at a distance of 1 km.

 

A female polar bear with one cub on Franz-Josef Land near the shore on a rocky slope. She is searching there for bird eggs. There crab divers are breeding now. This female bear weighs about 300 kg.

 

During the next winter both of them will lose one third of their body weight. They must eat therefore now as much as possible. And the mother still suckles her cub. The summer in the Arctic lasts only 4-6 weeks.

 

The polar bear cub needs more energy, compared with his body weight, than the adult animal. Therefore it will sooner become tired.

 

The young crab-divers in their nests at the cliff must be able to fly within 8 weeks, because then they must fly back to the south.

 

The Franz-Josef Land in summer.

 

A polar bear in the water.

 

A polar bear can swim easily without a break 100 km, in the icy water of the Polar Sea. It paddles with its front paws and steers with its hind legs.

 

When the polar bear swims in the water, it is not able to catch any seals; because the bear must swim, to stay above the water. Only seals, which lie on an ice-floe he is able to catch.

The polar bear shakes out the water from its hair-coat.

 

In summer there is an abundance of food. In winter there is very little food. The algae are growing only in summer. The seaweed survives the long winter by the reserves, which it has stored up in summer. These green plants, these submarine forests, are able to survive many arctic winters.

 

The salty sea water freezes only at -2°C. At the end of August the sea begins to freeze over again. The pack-ice then covers it again.

 

The male polar bear lets himself be snowed in. The female bear spends the winter in a snow-cave with her cubs. Or, if she is pregnant, she will give birth in her snow-cave to her cubs.

 

A polar bear in winter on the pack-ice on Franz-Josef Land.  – End of the quotations. 

 

 

 

White fur: the polar bear’s personal greenhouse. Solar radiation goes into the colourless hair, like into a glass-fibre. And then into its dark hide, warming the animal. From: Bernard Stonehouse, Animals of the Arctic the ecology of the Far North (1971:38). Photo: Breumer.

 

 

On 17. 12. 2002 the television station WDR showed the documentary film In the land of the polar bears. By Sandra Tober:

 

A female polar bear in the Canadian Arctic. The Arctic begins at the timber line.

 

2 polar bears

 

A female polar bear with her two cubs. The southern limit of the home range of the polar bear lies close to the timber line, at the shores of the Hudson Bay. It roams across the tundra and the ice-covered Polar Sea.

 

The ice determines the life of the polar bear. Its life depends completely on the ocean. It needs the ice-cover, to capture its main prey: the seals. In some areas the polar bears do not hibernate in winter, except the pregnant females. They move over the ice-covered sea and look for seals. They smell the seal, when it is still 1 km away. She will continue to hunt there as long as this ice-cover exists.

 

The female bear must kill a prey animal every 4-5 days, to feed herself and her cubs. In the Arctic Ocean she hunts mainly ringed seals. In 9 of 10 attempts she does not have any success.

 

4/5 of the iceberg is under water.

 

A female polar bear swims in the water. They are able to swim more than 100 km without resting. In summer, when the pack-ice has melted away, the polar bears come ashore.

 

The seaweed grows in the shallow water. Also the caribou eats it.

 

These ice-floes have formed from freezing sea water.

 

A polar bear in the water.

A swimming polar bear under water.

Without the ice also the bear is stranded, is helpless. 

A polar bear at the beach attacks walruses.

 

The polar bear weighs 600 kg.

 

The sun shines here all the time for 3 months, and the plants are able to grow well.

Stranded polar bears in summer must be patient. They wait, until the Sea is frozen over again.

 

The polar bear is well adapted to cold weather. But the heat in summer bothers him. That is why he goes into the ice-cold water to cool off.

 

On Canada’s Arctic Islands the winter begins already in August.

Musk-oxen on the arctic islands. They weigh 300 kg, half as much as the polar bear.

 

A female polar bear with cubs in summer.

 

This female polar bear crosses the area of the musk-oxen on her way to the pack-ice, which begins to form now.

 

A female polar bear with 2 cubs in the south-western part of the Hudson Bay.

A female polar bear on the ice.  – End of the quotations.

 

 

Polar bear and melting ice cover

 

The television Journal tv14, 5-18 March 2005, Page 19, 20, had an article about the polar bear and the climate under the heading: “The climate: a fragile system”. I would like to quote from it. I would like to study here the question: Would the polar bear also be able to live on land, when the Arctic Ocean is not covered with pack-ice?

 

Nearly during the whole year the polar bear lives on the ice cover of the Arctic Ocean, because the seals live there, on which he lives. In the open water, the polar bear does not endanger the seals, because he must swim then, to stay above water. Only on the pack-ice is he able, to capture the seal. Usually only the female bear stays during the long arctic winter on the mainland or on one of the arctic islands in her snow cave, to give birth to her cubs.

 

What would happen, if some day the pack-ice on the Polar Sea would melt away, if it would suddenly disappear? Would the polar bear then also be able to live in the Far North: on the polar desert, northern tundra and forest-tundra of North Siberia, Alaska and Canada? In other words: would the polar bear be able to live in the severe arctic climate, where it is so cold and so dry, that no trees are able to grow there?

 

This question is important: Because it will help us, to find out, in what kind of a climate and on what kind of a plant cover the animals of the mammoth fauna have lived. That is, when the mammoth grazed up there, in the central and northern part of Alaska and the Yukon Territory.

 

The polar bear is just us heavy as the brown bear, which lives now at the coast of southern Alaska. He is just as heavy as the now extinct short-faced bear of North America. The short-faced bear has lived in the central and northern part of Alaska and the Yukon Territory, when the mammoth was grazing up there. They have lived there during the Last Ice Age, the ice age experts believe.

 

Of the polar bear from the Last Ice Age, the palaeontologists have either not found any bones at all or only very few. And often they are not sure, whether those are the bones of a Pleistocene polar bear or of a brown bear. In any case: During the Last Ice Age, when the mammoth has lived up there, there either have been no polar bears at all in the Far North or only very few.

 

If the polar bear has lived in the Far North like today, if he has been there just as common as today: what should we expect then? Then we should also find his remains just as often. Palaeontologists often find the remains of other remains of marine mammals, which have lived up there during the Late Pleistocene, like whales and seals. But that is not the case. According to what we do know today, we can say this much: There either have been no polar bears at all during the Last Ice Age in the Far North or only very few. Why this is so, no ice age expert has been able to explain yet convincingly.

 

The brown bear, which has lived during the Last Ice Age in the central and northern part of Alaska and the Yukon Territory, was just as heavy as the brown bear, which lives now at the southern coast of Alaska and on Kodiak Island.

 

The short-faced bear, which has lived near the present Arctic Coast, on Alaska’s North Slope, during the time of the woolly mammoth, was just as heavy as the brown bear, which lives now at the southern coast of Alaska. The palaeontologists base the age of the bones from the Last Ice Age mainly on radiocarbon dates.

 

The Polar Bear in the Arctic: not able to live on land: would starve to death

 

“The polar bears have become, nearly overnight, the most endangered animal species on earth.

 

The background: The NASA has just announced that the North Pole will be ice-free already in this century. According to their analysis, the ice cover disappears much faster, than they had prognosticated. Measurements of the WWF (World Wildlife Fund) do support these results. Each year now, 9.2 percent of the arctic ice cover melts now each year. That is in an area, which is as large as Germany.

 

The polar bears and a catastrophe, which endangers their life. During the winter the sea ice freezes over two weeks later, and in summer it thaws two weeks sooner. Altogether, the animals do lose now one month of time, during which they can eat enough, so that they will be able to store a protective layer of fat. Because: Their favourable prey is the seals. They are only able to kill them on the ice floes, where they wait and sneak up to them. These bears do depend on it that the ice freezes. On land they do not find any food. Already now, most of these bears do have now on the average 80 kilograms of underweight, says the biologist Ian Stirling. And more than half of the babies die, because their mothers are so weak, that they cannot produce enough milk.

 

Within 20 years, so the experts have calculated, the last ones of the now 22.000 polar bears will have died out. ‘A long time before man has been able, to study and understand these animals’, says Ian Stirling, ‘these animals have abilities, which to researchers are still a riddle.’ Already their origin is a chapter full of wonders, because the polar bears have split off only quite recently, some 100.000 years ago, from the branch of the brown bears. They are the only ones of their kind, which have evolved into a marine mammal. They are equipped with webs (swimming skins) between their toes.

 

And they have changed from a vegetarian into a flesh eater (carnivore). Today the polar bears are the only mammals, which live during the whole year in the Arctic: Their water-proof pelt stores the heat a 100 percent. It stores the heat so perfect, that one is not able to see these animals on infrared pictures. Their noses are so fine that they are still able to smell a carcass at a distance of 30 kilometers. That is a distance, which they can easily cover. Their paws (claws) are pervaded with tension bones (Spannknochen). Their stability under stress is as large as Titan. In deep snow these bears reach a speed of up to 40 km/h.

 

The melting of the Arctic not only endangers the polar bears. ‘The ice fulfils an important role in the climate of the world’, explains Hartmut Graßl, Director of the Max-Planck-Institute for Meteorology. ‘Now it reflects 80 percent of the incoming solar radiation. And it regulates the temperature of the earth, in such a way, that it stays at an endurable level.’ When the ice disappears, some researchers fear, the Polar Sea will swallow this light. And this will heat up then the atmosphere still more. The result: The precipitation and inundations (floods) will increase then mainly on the northern hemisphere.

 

The climate: a fragile system. Will there be a chain reaction, when the Polar Sea melts? During the next 50 years the temperature of the Arctic will rise by four to seven degrees (Celsius). The sea level will rise then by about seven meters. To this result a new study has come, the ‘Arctic Climate Impact Assessment’. On this study 300 scientists have worked from eight States, which live at the Arctic Ocean.

 

Why does the ice at the North Pole melt?  The global temperature rises mainly, because of the rising amount of greenhouse gases, like carbon monoxide. They arise, when people burn mineral gas and coal.

 

What will happen, when the ice cover at the North Pole melts? Up to now, the scientists are not sure. But most of them now do believe this: Already, when the global temperature rises by only two degrees, South America may not have enough water anymore. In Asia there will be bad harvests (crop failures). And in the Caribbean Sea there will be huge hurricanes.

 

How fast will the ice melt away? When the global climate gets warmer, we will notice this first in the Arctic. The WWF (World Wildlife Fund) has calculated: Already in the year 2026 the global temperature will have risen by two degrees. In the year 2070 most of this ice will the gone (will have disappeared).

 

Result

 

The experts have come now to this conclusion: When the pack ice is gone, when it has disappeared from the Arctic Ocean, when it has melted away, also the polar bear will be gone, will have disappeared there. Because this large bear is only able to live there, when the Polar Sea is covered by pack ice, on which he is able to hunt seals. Because he cannot survive up there on the mainland and on the islands of the Arctic Sea: on the polar desert, the arctic tundra and the forest tundra: Because he does not find there enough to eat. He would starve there to death. And the female polar bear would not be able then, to get any cubs, because in autumn she would not be able to put on (to store) enough fat on her body.

 

From this I do conclude: Also the short-faced bear and the brown bear, in the time of the woolly mammoth, were not able to live in the central and northern part of Alaska and the Yukon Territory, in an arctic climate: Because they were just as heavy as the polar bear today. And because they were just has heavy as the brown bear, which lives now at the southern coast of Alaska. This means: They needed just as much food. And the arctic plant cover is not able to produce so much food!

 

In the tundra and forest tundra of Alaska and the Yukon, only very small grizzlies or brown bears are able to live now, because they find there only little food: Just enough, to survive, despite of their small body weight.

 

 

 

The ice cover on the Arctic Ocean: how large it is today. On this ice cover the polar bear lives. He hunts there his most important food: the seal. Picture: Thomas P. Manngelsen, Premium. After: tv14 2005:19.

 

 

 

Polar bear on ice pack ice of the Arctic Ocean. Photo: Thomas D. Manngelsen Pictures, Premium. After: tv14 2005:20. Only on the pack ice he is able to hunt his most important prey: the seal.

 

 

How the ice cover of the Arctic Ocean will melt away during the next years, when the global climate gets still warmer. When the ice on the Polar Sea is gone, also the polar bear will be gone. Picture: Superbild, Arcticphoto/Laif, Clifford Grabhorn/Acia Map. After: tv14 2005:20.

 

 

 

 

Polar bear and brown bear: how heavy and how much fodder per day?

 

How heavy does the polar bear become? And how heavy does the brown bear become?

How much fodder do they need per day?

 

I contacted therefore Dr. Blaser in the Wilhelma, the zoological garden of Stuttgart, in Germany. He looks there after the bears.

 

Question: How heavy does the male polar bear get, in the autumn, when he is fat? 

 

Dr. Blaser: 400 to 1000 kg.

 

Question: And how heavy does the coastal male brown bear, the Kodiak bear, get, when he is fat?

 

Dr. Blaser: 800 to 1200 kg.

 

Question: How much of the captured seal does the polar bear use, devour?

 

Dr. Blaser: About 70% of the prey-animal. It does not eat the skeleton, or any leg bones.

 

Question: How much fodder does the polar bear and large brown bear get in the zoological garden per day?

 

Dr. Blaser: 12-20 kg. ½ meat, ½ half raw vegetables (wet weight). They do not get any leg-bones.

 

Question: Why does the fodder of these bears consist of one half of meat and one half of raw vegetables? Why do you not give them only meat? Would they also be able to live without those vegetables, only from the meat? Because they are carnivores, flesh-eaters, are they not?

 

Dr. Blaser: The bears get the raw vegetables in place of the internal organs, like liver etc. The liver contains all the necessary vitamins. No carnivore is able to live only on muscle meat. It needs the internal organs. When the polar bear has captured a seal, it first will eat its liver.

 

Note: The grizzly bear in Central Alaska does not eat the skeleton, also not the leg-bones and the head-bones from the carcass of the moose either. They seem to be too hard.

 

How much prey biomass does the bear then need per day?

 

The brown bear and polar bear get 12-20 kg fodder in the zoo per day: half meat, the other half raw vegetables (in place of the internal organs). How much does the brown bear and polar bear (male and female), of average weight, then need per day? 

 

12-20 kg that are then 16 kg meat with internal organs [here raw vegetables] per day. To this we must still add about 30% waste: the parts, which the bear does not eat, like the skeleton with its leg-bones. That is 4.8 kg. 16 kg and 4.8 kg is 20.8 kg of prey biomass per day. How long would the bear then be able to live on this seal, if it weighs 91 kg?

 

On this seal, weighing 91 kg (200 pounds), he can live then 4.4 days (91 kg: 20.8 kg). It needs then 7592 kg of prey biomass per year, if it does not hibernate in winter. That is 83 seals at 91 kg each per year. That applies to the average polar bear and brown bear, male and female.

 

How much fodder does then the large male coastal brown bear and polar bear need, which weighs 700 to 1000 kg?

 

The large coastal brown bear and polar bear need 20 kg of meat with internal organs per day. To this we must still add 30% waste. That is, bones, which it does not eat. That is 6 kg. 20 kg + 6 kg = 26 kg of prey biomass per day (the whole animal, with waste, the parts, which the bear does not eat).

 

The large brown bear and polar bear will be able to live on one seal, which weighs 91 kg, for 3.5 days. The polar bear, which weighs 700 to 1000 kg, must capture then every 3.5 days a seal, weighing 91 kg. That is 9490 kg of prey biomass per year, if it does not hibernate in winter. That is 104 seals at 91 kg each. Actually it will need still more. Because this amount of fodder applies to animals, which live in the zoological garden, where they do not have to exert themselves. Animals, which must capture their fodder in the wilderness themselves, must exert themselves more. One may assume that the animal, which lives in the wilderness, needs 20% more fodder than its relative, which lives in the zoo.