Fakten zu den Bären
(source: Ursusus International)
Few animals inspire more in the human psyche than the grizzly bear. At once loved and despised, revered and feared, the grizzly bear simultaneously fulfills the role of nurturing spirit and nemesis, for human beings. There is perhaps no greater symbol of wilderness than the grizzly bear, and, indeed, where the grizzly survives in viable populations it is a general sign of the integrity of that ecosystem. Despite its image of ferocity and strength, the grizzly bear's place in the ecosystem sits in a fine balance and is intolerant of much disturbance. This, combined with a slow reproductive rate linked to very high maternal investment, means that the loss of just one or two bears, or an ecological disturbance resulting in habitat marginalisation, can result in serious population reduction or even regional extinction. There are many places that we see as wilderness, because they are devoid of the structures we associate with developed areas, but the levels of disturbance or human activity in them may mean that grizzly bears no longer exist there. Their absence is the first sign of wilderness status having been lost, and, like the keystone of a bridge being removed and the whole structure collapsing afterwards, so the interactions of the other species in an ecosystem are disrupted by the loss of the grizzly bear.
The grizzly (brown) bear was apparently named by early European explorers and settlers in North America because of a combination of the appearance of its coat, and character traits they observed in its behaviour (grisly)! The grizzly bear ranges today from the Yellowstone ecosystem in north-west Wyoming to the northern coast of Alaska and Canada's Yukon and Northwest Territories. While brown bears in general are omnivores, the Kodiak bear is largely carniverous, and the grizzly bear, is about 90% herbivorous. All bears are opportunist feeders, and much of the 10% of meat in the grizzly bear's diet, is comprised of carrion. The lower protein, more herbivorous diet of the interior or mountain grizzly means that it is significantly smaller than its Alaskan coastal cousin or the Kodiak.
The grizzly bear was originally an animal of the Great Plains, but it may have begun a retreat to the west when the Plains Indians began to use horses for hunting. It was then pushed out of the plains and into the mountains by the westward advance of European settlers in North America, in the 18th and 19th Centuries. As recently as the early 1920's grizzly bears still existed as far south as California and Arizona, populating every western state of the continental United States between there and the Canadian border. In only 80 years since, however, the exponential growth of the human population in the west, and all its attendant development, has reduced this range to a contiguous area encompassing Montana from the Rocky Mountains west, and northern Idaho. Technically separated from this, the Greater Yellowstone Ecosystem still supports a good population of grizzly bears. Otherwise, the only grizzly bears remaining south of Canada are in the North Cascades of Washington State.
Grizzly bears mate between May and July, while implantation of eggs into the uterus is delayed until October or November. The total gestation period is between 180 and 266 days, with the cubs being born between January and March, when the mother is hibernating. Cubs generally stay with their mother for two years, although they will stay for three or four if the sow does not become pregnant in the fall of their second year. Pregnancy triggers a reaction in the sow through which she drives the cubs off and hibernates on her own in preparation for giving birth to new cubs the following spring. Cubs will often spend their first hibernation together, and three-year olds observed in frequent close proximity in the spring are most likely to be siblings who have denned together. Female grizzly bears become sexually mature at between 4 and 6 years old, though growth continues later than that, while first pregnancies occur on average between the ages of 5 * and 7.
Grizzly bears are extremely good mothers, and, consistent with the high level of 'investment' they make in their cubs to ensure their survival, they are very protective of them. Because of this, encountering a grizzly bear, indeed any bear, with young can be very dangerous. During the first two years of their lives, the sow will teach her cubs everything they need to know to survive on their own. She will literally school them in finding and exploiting different food sources, and the cubs spend significant time observing her actions and learning them for themselves. This can be very clearly seen in footage from McNeil Falls or Brooks Camp, in Alaska, where cubs will sit watching their mother catch fish. Because this high level of input is critical if cubs are to survive on their own after separation from their mother, it is easy to understand why cubs that lose their mother in their first year are severely disadvantaged. Many bears that become what we term 'nuisance' animals as adults, were orphaned as cubs and as a result did not learn all they needed to from their mother. Because bears are adaptable and intelligent, many that are classed as nuisance animals are in fact improvising on what is available for their survival. If one considers that many cubs lose their mothers due to human action or negligence, it seems doubly hard on the bear that it should then be dealt with as a nuisance or 'problem' bear for adapting to its surroundings in the absence of its mother's teaching.
Interestingly, while adult grizzly bears do not climb trees, cubs can; sows may tree their cubs as a defensive measure. Grizzly bears have long straight nails for digging, that are not good for climbing, though it has been argued that there is no need for the grizzly bear to climb as, technically, no other animal preys on it. Black bears, which do climb, have short, curled nails that are better suited to climbing. The polar bear has similar nails to the black bear, though in it's case, they are designed for gripping on the ice, when running or climbing out of water, and for tearing apart prey.
A grizzly bear boar may weight 700lbs, averaging perhaps 350-500lbs, while a healthy, mature adult male would not generally be much lower than 350-400lbs. A large sow could weigh 500lbs, though mature females might average between 300-400lbs. By comparison, an Alaskan coastal grizzly bear boar could weigh between 800-1200 pounds, and a female could range between 600-800lbs. Male Kodiak bears can weigh as much as 2000lbs, though an average weight for mature animals would be between 1200-1500lbs. A female Kodiak might weigh 1000lbs, though an average adult weight might be around 700lbs.
One of the characteristics that separates bears from dogs is the ability to 'free' stand on their rear legs, a trait that allows them a better view of their surroundings. An adult male grizzly bear may stand at 7-9 feet tall, while a female may reach 6-8 feet. A male Alaskan coastal grizzly might be between 9-10 feet while a Kodiak bear could reach 11 feet. Kodiak bears may, in extreme cases reach up to 13 feet, but an average height for a mature male would be nearer 11 feet. Females might reach 9-10 feet.
Grizzly bears begin hibernation in the fall, between October and December, with pregnant females being the first to do so, and males the last. They are not true hibernators, but, rather, go into a state of torpor in which their metabolic rate is significantly reduced. They may wake from this, periodically, and, on some occasions, they may leave the den for a while to look for food. The hibernation period is correspondingly less in the southern reaches of the range. Grizzly bears generally dig their own dens, which are normally located on sheltered alpine slopes, and make a bed out of dry vegetation. They may use a particular den repeatedly. A bear of 700lbs may come out of hibernation at 450-400lbs, while a bear of 350-400lbs might come out of hibernation at 250-200lbs. A large female of 500lbs, that was breeding, might come out of the den at 200lbs, while smaller breeding females entering the den at 350-400lbs can deplete to a little as 150lbs. Males will come out of hibernation first, sometimes appearing as early as February, though on average the hibernation period ends between April and May.
Grizzly bears have a potential lifespan of about 30 years in the wild, although in reality few live that long. Bears that range in any close proximity to a human population all to often fall victim to hunting, traffic, or being killed because of a conflict or nuisance situation. In the wild, older bears, past their prime, can be killed by younger animals during the mating season, or, exceptionally, if they were very weak, they could be killed by wolves. Unfortunately, grizzly bears, like black bears, rarely reach their potential longevity in the wild now, in a world where they are constantly under pressure from human encroachment and development.
Alaskan coastal grizzly bears
The Alaskan coastal grizzly bear or Alaskan brown bear illustrates the link between the interior grizzly and the Kodiak, in having much of the appearance of the former, and a good deal of the bulk of the latter. It has a similar diet to the Kodiak, but is less confined in its range, and therefore has a larger amount of genetic material available, making it less susceptible to very specific endemic adaptation. It shares much of the biology and behavioural information of the (interior or mountain) grizzly bear.
Through the Alaskan coastal grizzly it is possible to observe a trait that is both uncommon in bears, and which reflects their adaptability: During seasonal salmon runs, the bears will congregate in large groups of sometimes 30 or more animals, in an aggregation that would not be tolerated by individuals if it was not balanced by food supply. Implicit in this 'unusual' behaviour, is a recognition by individuals that the large number of animals will not outdo the food supply and compromise their potential to obtain all the food they need. Other than the association of mothers and cubs, this is one of the few occasions when bears will display any kind of 'pack' behaviour. Kodiak bears behave similarly under similar circumstances, as will black bears, particularly Kermode (spirit) bears. Polar bears congregate in southern reaches of their range, notably at Churchill, Manitoba, during the fall freeze-up of Hudson Bay. This tolerance is brief, and ends as soon as the ice is strong enough to carry a bears weight, permitting them to leave shore. This behaviour can also be observed in a denaturalised setting, such as at a garbage dump or around any plentiful and consistent artificial food source. Pack behaviour in such a context is a symptom of compromised natural behaviour and response, and is indicative of part of a process of habituation that is very dangerous to bears. Habituation is broadly discussed in a number of other areas of this website.
The Alaskan coastal grizzly is the same animal that is found on the Siberian Peninsula. The relationship between those Asian coastal bears and the smaller brown bear of interior Siberia and European Russia and Finnmark, mimics the relationship between Alaskan coastal grizzly bears and those in southern Canada and the United States. Just as the polar bear 'rings' the globe in the Arctic, this impression of the much larger global range of brown bears in the sub-Arctic and temperate zones clearly illustrates their status as a global species.
The Kodiak (brown) bear was named for its being endemic to an area centering on Kodiak Island, off the south coast of Alaska. However, the Kodiak bear is also found on other nearby Alaskan islands such as Admiralty and Shuyak, where, as on Kodiak, it has developed within an isolated genetic niche based on an abundance of high protein food, namely salmon. As a result, the Kodiak is much larger than the grizzly bear of the Rocky Mountains, and the fact that the range of the Kodiak is so confined by island status and diet has meant that there is nothing to dilute its biological and genetic response to its very protein-rich diet.
With a general biology very similar to that outlined for the interior grizzly, the Kodiak bear is often the subject of debate over which is the biggest species of bear. It is often held that the polar bear, which is, in many ways, the most mythologised bear, is the biggest and most ferocious ursid, but there is in fact very little difference in the potential size and bulk of the two species. The term 'potential' is very important here, as even in a particular age/sex class, height and weight variability among North American bear species can be extreme. If anything, the average highest weights amongst Kodiaks are higher than those amongst polar bears, though individual polar bears may exceed the average high weight of Kodiaks by a significant amount. This said, it is difficult to compare bears' weights because of extreme seasonal fluctuation: Kodiaks have a longer feeding period than polar bears, and the point at which the two species are at their maximum weight is a narrow intersection. Comparison at that point might be interesting, but may not mean very much, perhaps giving a false overall impression of the polar bear, whose extreme fat diet over a relatively short time results in a very variable annual weight change. This begs the question of when meaningful comparison might be made, and that perhaps comparison is not very important, but is too much of an issue in our statistics-hungry minds where it simply serves to propagate myth and misunderstanding. For more points and discussion about issues like this, go to the Myths and Legends section of this website.
European brown bears
The European brown bear (Ursus arctos arctos) can be found in reasonable concentration in north-west Europe, from the Ural Mountains west to Finnmark, and in the Baltic States. The bears exist further south in eastern Europe, though in smaller numbers where human populations are higher. The highest concentration is in the Carpathian Mountains, in the Transylvanian region of Romania, where it is higher than in Denali National Park, in Alaska. The extent of this population is due largely to serendipity in that former dictator Ceaucescu was keen on bear hunting and prohibited anyone other than himself from engaging in it. There are brown bears in northern Italy, concentrated in the area of Abruzzo National Park, the Balkan States and in the Pyrenees. The isolated nature of these populations, particularly the latter, and the attendant genetic impoverishment, is a threat to them. Historically, brown bears were widespread in Europe, as is evidenced by the position of the bear in many European cultures where they no longer exist in reality. As the human population in Europe grew, so the range of the bear decreased, predictably, inexorably, and in a way that North Americans would do well to consider in relation to their own continent today.
The European brown bear resembles an interior North American grizzly bear in conformation and size, though in general it may be slightly smaller, and it shares much of its biology. The brown bear is widespread east of the Urals throughout Asiatic Russia and Siberia to the Pacific coast, where it is indistinguishable from the Alaskan coastal brown (grizzly) bear. Brown bear populations in the Balkans and the Caucasus, and across Central Asia and in Japan attest to its status as a truly global species. In the modern world, however, with it's burgeoning human population demanding ever more bear habitat for its own ends, the status of many of these populations is weak and in recession, and for some, if present trends do not change, they will soon cease to exist.
Black bears (Ursus americanus)
The black bear or American black bear, which is found in both the US and Canada, is the only bear species that is uniquely endemic to North America. Despite its name, and although principally black, there are many different colour phases of black bear, ranging from jet black to white. These two colour extremes are evident in the sub-species Ursus americanus kermodii, the Kermode or 'spirit' bear, which is found in some areas of the west coast of British Columbia.
The brown phase of the black bear, better known as the cinnamon black bear, is probably the most commonly seen and recognised variant. Cinnamon black bears vary from dark chocolate brown to light gold, and some colourations make them difficult to distinguish from grizzly bears, where their ranges intersect. Another less known variant of the black bear is the 'blue' black bear or 'glacier' bear, which is endemic to the Tatshenshini area of north west British Columbia.
Unlike grizzly bears, black bears are widespread in most of the US and Canada outside the Arctic, though the northern limit of their range depends on the treeline. Black bears exist in the same ecosystems as grizzly bears, though they occupy different niches within it, the black bear being a resident of the montane zone, the grizzly bear one of the alpine zone. Grizzly bears and black bears have a non-interactive tolerance in terms of sharing the same ecosystem, which breaks down on occasions, generally to the detriment of the black bear. Where the two species coincide, black bears significantly outnumber grizzlies, generally by a ratio of 10:1. Black bears exist throughout the contiguous United States, and can adapt better than grizzly bears to disturbance by human beings. As a result, black bears can survive in relatively close proximity to people and human infrastructure in a way that grizzly bears cannot. In this sense the black bear can be compared, in the bear family, to the coyote in the dog family – coyotes are also found throughout the United States and are able to adapt to human settlement and disturbance. The wolf, however, like the grizzly bear, requires very large areas of wild land if it is to thrive, and it does not do so where there is a high human presence. Inevitably, wolves will leave disturbed areas, and their present range within the United States, running through the northern states, from Washington to Maine, is a reflection of this. An interesting correlation in this is the fact that human beings are generally less afraid of black bears and coyotes than they are of grizzly bears and wolves, which also results in our being more tolerant of them. This is significant, but the different behaviours and requirements of the specific species has more relevance in the situation.
The description of the life-cycle of the black bear is very similar to that of the grizzly bear, while the main differences between the two species are mostly to do with appearance and, again, more related to behaviour than biology.
The peak of the black bear mating season is roughly from June to mid-July. Implantation of fertilised eggs in the uterus, however, is delayed until Autumn, and embryonic development only occurs in the last 10 weeks of pregnancy, which lasts about 220 days. Cubs are born in the den between January and March, with litters being generally larger than those of grizzly bears, often comprising three and sometimes four young. Cubs average * to * lb at birth, and are generally weaned at around 6-8 months. Like brown bears, Cubs stay with their mother for their first two years but will remain with her longer if she does not conceive at that time. Female black bears reach sexual maturity at 4-5 years old, while males mature about a year later.
Weights of black bears vary significantly according to region, and to availability and quality of food in a particular locale. An adult male can weigh up to 700 pounds, and yet an average weight in a general area where such a bear may be found might be 200-250 pounds. It is difficult to state an overall average weight for any age or sex class of black bear due to how widespread the species is, but in terms of region, bears in the southern rocky mountain area are generally smaller than in the northern Rockies. Similarly, in the southern states, unless influenced by a particular abundance or quality of food, bears are generally smaller than in northern New England or in Eastern Canada. As is the case with many wildlife species, human numbers, in relation to habitat quality, and depredation pressure, may have had the result of reducing the overall size and weight of black bears. In North America, northern habitats are generally less disturbed and less populated by people than southern ones; northern bears may therefore benefit from more natural and plentiful food sources. In addition, the colder climate may be conducive to larger or heavier animals through demand for more fat deposition for the hibernation period.
The black colour phase is a very obvious distinguishing feature of black bears, but in any of the brown, or cinnamon, phases, other, more reliable features that can be used to identify a black bear are as follows: Black bears have no shoulder hump, and they have a straight, or 'roman' nose, which actually falls in a very subtle convex arc from top to bottom. Black bears also have relatively larger ears than grizzlies, and they have the appearance of sticking up higher on the head. Black bears have curved claws, which allow them to climb trees. There are also a number of behavioural traits that distinguish black bears from grizzlies: Black bears are generally less aggressive than grizzly bears, and there is a good deal of evidence to show that they are normally less aggressive in response to a challenge or threat. For example, a person has a good chance of repelling a black bear, in the event of an encounter, if they make a directly aggressive display, whereas a grizzly bear, in the same situation, would be more likely to attack.
Black bears are predominantly herbivorous, though, like all bears, they are omnivores and opportunists – if they find meat, they will eat it, though the majority of what they do find will be carrion. An interesting exception to this is the spirit bear, a large part of whose diet is comprised of fish. Like grizzly and polar bears, black bears are capable of great speed, being able to reach 30mph in a short dash. However, although extremely potent, the black bear is seldom associated with the phenomenal strength or potential aggression of the grizzly bear, traits that placed the latter in a very particular place in the human psyche. In the wild, a black bear has the potential to live for 30 years, but the average life span is probably much lower due to the extreme likelihood of conflict, of one form or another, with human beings. Whether this comes about because of hunting in any particular season, traffic, or encounter with people, very few black bears, like grizzlies, reach anything like their potential longevity.
Polar bears (Ursus maritimus)
The polar bear is one of the few animals that occupy a realm that is largely without human population, and so some of the principal conservation issues that relate to it are unique. Whereas habitat loss is probably the most significant reason for decline in bear populations in other parts of the world, it is a less important factor with regard to polar bears. There are cases where human settlement and activity impact polar bears and their habitat, but in general we do not vie with polar bears for their territory, and their range is not in decline. Similarly, conflict with human beings, perhaps the other most significant factor in the decline of bear populations, is less of an issue with regard to polar bears, because interactions with people are so limited that the number of conflicts is very low. Conflict with polar bears has the potential to be very serious, but most problems that have occurred have been confined to specific areas that make up a tiny portion of the overall range of the polar bear.
Perhaps it is partly because of its obscurity that even in its reality the polar bear is partly mythical to us. Many people believe that the great white bear is the ultimate predator, and that it kills relentlessly and without motive. One of the main reasons for such beliefs may be that the polar bear has some uniquely adapted hunting skills, and, if anything, that we observe something of our own calculating and stealth in its behaviour and hunting methods. In general, we are attracted to the biggest and most powerful in any sphere, so that it is the grizzly bear and not the black bear that we hope to see the most when we visit the mountains, the lion and not the leopard when we are on safari. Seldom, when we see such animals do we report on our interaction in a calm and objective way, but, rather, we exaggerate for our own sake, perhaps to try and profit by association. This is the way we make legends, and the polar bear is the subject of many legends. So the polar bear has found its way into our desire and imagination, because it is so powerful, and because it is so much the undisputed king of its realm.
The reality of the polar bear could perhaps disappoint some people, in that many of its behaviours and traits are similar to those of black and grizzly bears. The polar bear adapted from grizzly (brown) bears that moved north, and it is believed that the two species 'separated' about 200,000 years ago. Polar bears and brown bears are so closely linked, in fact, that if they were to interbreed they could produce fertile offspring. The southernmost polar bears in the world live in the James Bay and Hudson Bay areas of Quebec, Nunavut and the Northwest Territories. The continental climatic influence on these inland seas resulting in their being frozen for six months of the year, providing a southern peninsula of habitat that would not otherwise exist. At the southernmost extent of their range, polar bears live at the same latitude as London, England, though in a far harsher climate. At the extreme north west of the range of the brown bear, there is some intersection with the range of the polar bear, so, while the possibility of interbreeding is remote, if it were to happen, that is where it would be most likely. Polar bears are a true global species, existing in North America, Europe and Asia, and, in the far north, they have been documented moving round the world on the ice.
There is very little difference in the size and weight of mature adult male polar bears and Kodiaks. In each case, mature males may weigh up to as much as 2000lbs, though more commonly they will average between 800-1200lbs. Sexual dimorphism in polar bears is very marked, with males often weighing twice as much as females, a factor which may partly be explained by males having significantly longer feeding periods than breeding females. In the Hudson Bay and James Bay areas, polar bears look very much like white grizzly bears, having short necks and broader heads with 'dished' or slightly convex faces. Further north, the bears have a more aquiline appearance, with longer necks and smaller, narrower heads. It is possible that this is an adaptation to more time spent in water, a kind of streamlining. Despite these differences, polar bears were never divided into distinct sub-species as brown bears were until recently.
Polar bears have black skin, which helps to absorb heat. This is only evident if one looks closely at a bear's face, or if the animal has a scar. Their hair is hollow, containing a thin column of air, which gives it exceptional insulation qualities. The feet of the polar bear have a thick covering of hair between the pads, and recent research has shown that the pads themselves actually give out enough heat to very slightly 'melt' the surface of the ice underfoot, enhancing grip. In combination with hooked claws, like that of a black bear, the polar bear is very well equipped to travel on ice.
Polar bears are almost completely carnivorous, being largely reliant on ringed seals (Phoca hispida) for food. Like most bears they are opportunists, and they will feed on other animals or carrion, but they are most adapted to ranging over the ice looking for seals' breathing-holes, and trying to catch them when they come up for air. As this suggests, polar bears are reliant on ice for their hunting. In the Hudson and James Bay areas, the bears only feed when the bays are frozen, which means they do not hibernate, as winter is by far their most active time. In the summer, the bears go through a period that is termed 'walking hibernation', where they are awake but conserving as much energy as possible. At this time, the bears rest and try to stay cool, as they are uncomfortable in temperatures above freezing. In some cases, they will excavate shallow dens, exposing the permafrost, and they will then lie on these ice-benches to keep cool. Apparently, during this ice-free period, polar bears spend up to 87% of their time resting.
During the brief summer months, the bears feed very little, relying instead on the fat stored by the previous winter's hunting. They become more opportunistic during this time, and will feed on stranded mammals and fish, small land mammals and even reindeer. They will also catch sea birds as they sit on the water, and they may eat berries if they come across them. Scat found during this ice-free period may contain some seaweed, and it is thought that the bears eat this in small quantities as a mineral supplement, much the same way ungulates will lick at mineral deposits where they come to the surface or are exposed. Feeding during this period is supplemental compared to feeding during the winter, which permits significant fat deposition.
For male bears and non-breeding females, this fasting period is generally from June or July to November, when the bays are ice-free, but for pregnant females who den from October or November until February, it is twice as long. When the female bears emerge with their cubs, having emaciated to about a quarter of the weight they carried on entering their dens, they have as long as the ice remains to regain their fat and feed their cubs adequately to allow them to survive to the next winter. As if this daunting task were not enough, the female polar bear must also defend her cubs from potential attack by males, who, like other bears, may try to kill cubs, particularly male cubs, if they have the chance. Climate change in recent years has meant that the ice in these southern areas of the polar bear's range is forming up to two weeks later than it did in the past. Similarly, in the spring, the ice is melting that much sooner, so the net result is that the feeding period for female polar bears with cubs has shortened by about 25%. If this proves to be a long term trend, or if this reduction increases, it is likely to make these southern polar bear populations non-viable, causing them, inevitably, to shift north.
Further north, where the ice is permanent, the bears do not have a fasting period, though food is less abundant, and climate and activity mean that a constant supply of food is necessary. The abundance and more moderate climate of the southern part of the range is what makes the bears' survival through the ice-free period possible.
Mating occurs on the ice, between March and June, and pregnant females den in the fall. Dens are usually located within 8km of the coast, though in the southern Hudson Bay region, they are concentrated in a 'traditional' denning area that is 30-60km inland. The protection of this denning area is one of the main reasons for the designation of Wapusk National Park. Because implantation of the egg is delayed, gestation lasts from 195-265 days, and cubs are born between November and January. At birth, cubs weigh about 1 *lbs, and they remain in the den until March or April, by which time they weigh 20-40lbs. Generally, polar bears will have twins, though singles and triplets are quite common. As with grizzly bears, quadruplets are rare. In cases of triplets or quadruplets, it is common that one or two cubs will not survive to maturity. It is quite common to observe polar bears with single cubs, which, because twins are more common than singles, suggests that many sows lose at least one cub. After spending a week to 10 days close to the den, for the cubs to get used to being outside, and using their limbs, the sow will then begin heading towards the ice to begin feeding. This is a vulnerable time, as the sow will not have fed for approximately 8 months, and the cubs are completely dependent on her.
Normally the cubs will stay with their mother for two years, unless she does not become pregnant again in the fall of their second year. Initially, after separating from their mother, siblings may remain together for some time. It is quite common to see three and four year-old bears playing and sparring together, and in many cases the bears in these situations are siblings. Play is an important part of the early years of a polar bear's life, and through it they learn about social interaction and, in the case of males, it prepares them for a time during future mating seasons, when their sparring will be more serious. Sexual maturity is reached between 5-6 years, on average, being earlier in females, and adult weight is reached at about 5 years by females and 10-11 years by males.
Polar bears, like black and brown bears, can live to between 25 and 30 years, and in some ways, are more likely to reach their potential longevity than any other species of bear. This is largely because there is little overlap between polar bear habitat and that of human beings, and, unlike the brown bear, there is little difference between their historic and present ranges. Particularly in the high Arctic, polar bears inevitably succumb to the elements of their harsh environment, old age making them less successful at hunting, leading to gradual starvation which, in turn, makes them still less able to find adequate food. Eventually, starvation and, ironically, the cold, combine to kill them. Older bears are also sometimes killed by younger, stronger bears in fighting over females during the mating period; these things are all reflective of the harshness of the life cycle and the environment of the polar bear.
The polar bear is a formidable hunter, and that, combined with its size and the fact that so few people know very much about it, has resulted in it becoming more the subject of legend than almost any other animal. Among the many indigenous peoples who live within the range of the polar bear, the bears are often powerful symbols and spirits, playing important roles in both history and modern culture. In many other societies, the polar bear has gained a reputation for being the most dangerous animal in the world, and for attacking and killing people and other animals for no reason. While people should have a healthy 'fear' and respect of the polar bear, as it is unrivaled in power and speed and adaptation to its environment, the way it is regarded is generally unfounded and based in ignorance, which is the case with many animals that acquire legendary status.
In reality, the behaviours of the polar bear are quite similar to those of other bears. Polar bears are very specialised hunters, but rather than being cold-blooded, they simply hunt in ways that permit them to sneak up on their prey without cover. There are three main hunting methodologies, the first being the scenting of seals in their den; having approached the den, the bears use their front paws like rams to smash in its roof, giving access to the seals inside. Dens make a significant contribution to the diet of the polar bear, as seal pups are very rich in fat. The second main hunting method involves lying in wait by a seal's breathing-hole, for the seal to surface for air. As proof of how potent a predator the polar bear is, there is an account of a bear waiting by a hole in the ice through which a beluga whale surfaced for air. While the 3-ton whale still had upward momentum, the bear seized it with its claws, and dragged it out of the water onto the ice! The other main hunting methodology is 'aquatic stalking', in which the bears use rivulets on the surface of the ice to approach resting seals while largely submerged.
What these methods have in common is that they are all very highly adapted, requiring calculation and intelligence more than just stealth. It is partly because of this capacity that the polar bear has gained such a notorious reputation amongst human beings; unfortunately, we often learn better from unfounded fear than we do from objective lessons. In his book "Arctic Dreams", Barry Lopez describes polar bears hunting seals on the open ice, crouched and moving directly towards them so that they are camouflaged other than for their black nose. Lopez claims that in such a situation, the bears seem to understand that their nose stands out and may give their presence away, and that they may cover them with their paws as they approach they seal! He also theorises that the bears may understand that if they approach the seal directly, it may not recognise what the nose is nor how far away it is, effectively becoming mesmerised by it, and so sometimes the bears will leave their nose uncovered as they approach. By the time they do realise what the nose is, the bear is generally so close that the seal cannot get away. If these things are true, they are very good illustrations of the great intelligence and adaptability of the polar bear.
For human beings in the arctic, polar bears are a very significant consideration, but their behaviour can, in general, be compared to that of the brown bear. They are similarly predictable, and they are no more given to tendencies that do not profit them or ensure their safety or the safety of their young. Given due warning of human presence, polar bears will avoid us, and they have far too pressing a task to gain and maintain fat to be distracted by some whim to kill for pleasure. That said, polar bears are almost completely carnivorous, and their environment is relentlessly unforgiving in demanding that they be equipped to survive in it. Because of this, there is certainly the potential that an unprepared or ill-equipped human could fall victim to a polar bear, although we are not a prey species to them. Theoretically, bears in the areas of Canada's Hudson or James bays, who do not feed during the summer could be more dangerous during their fast, though there is not specific data to back such speculation up. While the polar bear is master of its domain, human beings are, on the other hand, very poorly suited to it, and there is no doubt that out on the coverless, open ice we are at a huge disadvantage. In black and grizzly bear habitat, we can sometimes recourse to tree climbing or the use of cover or some other defensive option in the event of an encounter, but this does not apply to polar bear habitat.In a sense, this makes polar bears more dangerous than other bears relatively, rather than absolutely, and it demands that in their domain we exercise extreme vigilance.
For bear species in the temperate zone, the two most important issues are habitat loss and conflict with human beings. For the polar bear, these have less significance, although in recent times, oil and gas development has become a threat in some regions. Arguably, the greatest threat to polar bears is climate change, and specifically, global warming. While global warming is disputed in many of the temperate regions of the world, it is very hard to deny it in the polar regions. In the arctic, there is a lot of evidence of less and thinner ice, and of later freeze-ups and earlier thaws. Insufficient and weak ice will reduce the hunting potential of the polar bear and lead to an inadequate supply of food, which will mean less deposits of fat, leading to starvation. In the Hudson Bay and James Bay areas, this trend of later freezing and earlier thawing has reduced the feeding period for sows with cubs-of-the-year, by up to 25% of what it has been previously. This is a non-sustainable situation, and if it continues, these areas will cease to function as viable habitat, and the bears that presently live there will move north. For more information on this topic, go to the Issues section.