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Kingdom Animalia Phylum Chordata Class Mammalia Order Carnivora Family Ursidae Genus Ursus Species Ursus maritimus
Size Male head-and-body length: 2.4 - 2.6 m Female head-and-body length: 1.9 - 2.1 m Male weight: 400 - 600 kg Female weight: 200 - 300 kg
Description The polar bear is the largest living land carnivore in the world today, with adult males growing up to 2.6 meters in length. The most well known of all bears, the polar bear is immediately recognisable from the distinctive white colour of its thick fur. The only unfurred parts of the body are the foot pads and the tip of its nose, which are black, revealing the dark colour of the skin underneath the pelt. The neck of the polar bear is longer than in other species of bears, and the elongated head has small ears. Polar bears have large strong limbs and huge forepaws which are used as paddles for swimming. The toes are not webbed, but are excellent for walking on snow as they bear non-retractable claws which dig into the snow like ice-picks. The soles of the feet also have small projections and indents which act like suction cups and help this bear to walk on ice without slipping. Females are about half the size of males, although a pregnant female with stored fat can exceed 500 kg in weight. Polar bear cubs weigh up to 0.7 kilograms at birth. They look similar in appearance to adults, though they have much thinner fur.
Range This bear is found throughout the circumpolar Arctic on ice-covered waters, from Canada, to Norway, parts of the US, the former USSR and Greenland (Denmark). The furthest south the polar bears occur all year round is James Bay in Canada, which is about the same latitude as London. During the winter, when the ice extends further south, polar bears move as far south as Newfoundland and into the northern Bering Sea. They rarely enter the zone of the central polar basin as there is thick ice all year round and there is little to eat.
Habitat The preferred habitat is the annual ice near the coastlines of continents and islands, where there are large numbers of ringed seals (Phoca hispida), on which these bears feed.
Biology Polar bears are solitary mammals throughout most of the year, with the exception of breeding pairs and family groups. Populations, or stocks, of polar bears are distributed throughout the Arctic and have overlapping home ranges which are not defended, and may vary in size from a few hundred to over 300,000 square kilometres.
Diet The main food source is ringed seals P. hispida, and, to a lesser degree, bearded seals (Erignathus barbatus). The polar bears capture seals when they surface to breathe, or hunt them in their lairs, where young seals are nurtured. Polar bears show some amazing adaptations to their Arctic life and are able to detect prey that are almost a kilometre away and up to a metre under the compacted snow, using their heightened sense of smell. They also feed opportunistically on walruses, belugas, narwhals, waterfowl and seabirds.
When food is available these bears have a remarkable ability to devour large amounts of food rapidly, and are also metabolically unique in their ability to switch from a normal state to a slowed-down, hibernation-like condition at any time of year when there is less food available. For example, in Hudson Bay the ice melts completely by mid-July and, as it does not re-freeze until mid-November, pregnant females do not feed for 8 months. During this fasting time, they metabolise their fat and protein stores and recycle metabolic by-products. During periods of particularly cold weather polar bears may also fast, and are known to conserve energy by occupying temporary dens.
Reproduction Polar bears breed from late March to late May. Females nurse and care for their cubs for 2.5 years and are therefore only available for mating once the cubs are independent, every three years. As this means that only a third of females can breed each season there is intense competition by the males for females, which may explain why males are so large in size. Females must mate many times over a period of several weeks before ovulation and fertilisation are stimulated (induced ovulation), and breeding pairs remain together for one to two weeks to ensure successful mating. If the female’s partner is displaced she may mate with more than one male at this time. Implantation of the fertilised egg is delayed until mid-September to mid-October, and the female gives birth to the young in a snow den some two to three months later. Two-thirds of litters are twins, and single litters and triplets are also born. Though the polar bear has low reproductive potential, individuals do live for a long time, and have been known to live for up to 30 years.
Threats Polar bears are not endangered, though if hunting was not regulated they would be, due to their slow rates of population growth. They do face threats however, that must be constantly monitored. The Polar Bear Specialist Group reported in their 2005 meeting that the greatest challenge to the conservation of polar bears may be large-scale ecological change resulting from climatic warming, if the trend documented in recent years continues. Other threats to this species include pollution, poaching, and disturbances from industrial activities.
While the effects of climate change are not certain, it is recognised that even minor climate changes can have profound effects on polar bears and their sea-ice habitat. For example, if climate change results in increased snow in the Arctic, polar bears may be less able to hunt prey by entering seal birth lairs, which will affect the survival of both polar bear adults and cubs. On the other hand, if there is reduced snow and increased seasonal rain, seal productivity may be reduced as the lairs may not be thick enough to protect the pups as they develop, or lairs may collapse and kill the seals. In turn this would reduce prey for the polar bears. Unusual warm weather could also impact the polar bear’s denning activity.
Persistent Organic Pollutants (POP) also pose a threat to polar bears. Studies on the accumulation of organochlorines (caused by pollutants) through food chains have shown that polar bears, as top predators, are at risk of accumulating elevated levels of these compounds. These levels are associated with a range of effects, including neurological, reproductive and immunological changes, which may, for example, reduce ability to fight diseases and reproduce.
In the 1960s and 1970s, extensive hunting of polar bears had pushed them to the brink of extinction. This threat had a considerable impact on polar bear populations, and, though hunting is now controlled, populations are still recovering.
A large male bear emerges from the willows below a small hill as the sun begins to set. Hudson Bay area near Churchill MB.
Massive polar bear images
Polar bears defy extinction threat CHRIS MCAULEY
THE world’s polar bear population is on the increase despite global warming, which scientists had believed was pushing the animal towards extinction.
According to new research, the numbers of the giant predator have grown by between 15 and 25 per cent over the last decade.
Some authorities on Arctic wildlife even claim that hunting, and not global warming, has been the real cause of the decrease in polar bear numbers in areas where the species is in decline.
A leading Canadian authority on polar bears, Mitch Taylor, said: "We’re seeing an increase in bears that’s really unprecedented, and in places where we’re seeing a decrease in the population it’s from hunting, not from climate change."
Mr Taylor estimates that during the past decade, the Canadian polar bear population has increased by 25 per cent - from 12,000 to 15,000 bears.
He even suggests that global warming could actually be good for the bears, and warns that the ever-increasing proximity of the animals to local communities could mean that a cull will be required sooner rather that later if bear numbers are to be kept under control.
In the northern territories, where temperatures have risen an average of four degrees since 1950, wildlife experts such as Mr Taylor say the bears have never been healthier or more plentiful.
The findings fly directly in the face of recent warnings from the scientific community on the demise of the species, with the Canadian World Wildlife Fund currently speculating that the last polar bear could vanish from the earth within 100 years.
The WWF website states: "By 2100, there may be no ice left in the Arctic in the summer. That means no polar bears. Global warming - caused by fossil fuels - is to blame."
The contradicting claims on the consequences of global warming are not confined to the Arctic, however.
The situation is mirrored on the opposite side of the world, where the extent of global warming and shifting ice in Antarctica is currently the subject of debate.
Scientists looking southward from the tip of South America, over steel-grey waters towards icy Antarctica, see only questions on the horizon about the fate of the planet.
Research carried out during a recent two-month exploratory mission to the South Pole has suggested that the West Antarctic ice shelf may be much thicker that at first thought - many hundreds of feet thicker in some parts - with the potential to raise water levels by around 15 feet worldwide if the shelf should gradually melt.
The hunt for data on ice movements around the South Pole has taken on fresh urgency after Antarctica’s "Larsen B," an ice shelf bigger than Luxembourg, collapsed into the Southern Ocean over the space of just 35 days in 2002.
And now that one mammoth Antarctic ice shelf has actually collapsed into the ocean, is it possible that another, even bigger one, might also crumble and slip into an ever-warming sea?
"People don’t have the answer to the question yet - what the probability is of that collapse, if any," said a scientist Gino Casassa, an authority in global warming based in Chile.
With the potential to raise ocean levels by around five metres worldwide should the ice melt, it is little wonder that glaciologists such as Mr Casassa view developments around the West Antarctic ice sheet with concern.
Should the ice eventually turn to water it would signal a slow-motion catastrophe for global coastlines - not instantly deadly like the tsunami in Asia - but more universal and more permanent. Although stressing that all the data secured from the recent two-month trip to the South Pole was still awaiting full analysis, Mr Casassa stressed that "the deeper the West Antarctic Ice Sheet, the greater the potential impact to sea level".
But scientists concede that much remains unknown about the links between ice, ocean and skies.
It still isn’t known, for example, how excess amounts of cold, fresh water from glaciers could affect the ocean current that circles Antarctica from west to east - a main driver of all the world’s ocean currents and therefore of global climate.
From walruses we pass to bears. Mr.Lamont believes that the Polar Bear - the Ursus Maritimus of naturalists - is, in a state of nature, the largest and strongest carnivorous animal in the world. Be this as it may, his first specimen - the one which he was watching through the old opera-glass of which we have spoken - was a monster. His carcass measured eight feet in length, and almost as much in circumference. He stood four and a half feet high at the shoulder. The fore-paws were 34 inches around. His weight was at least 1200 pounds: of this the fat constituted 400 pounds, and the hide 100. When skinned, his neck and shoulders were like those of a bull. The hunters say that he will kill the biggest bull-walrus, although nearly three times his own weight, by springing upon him from behind, and battering in his skull by repeated blows. Mr. Lamont believes this, though he doubts the stories told of the way in which he is killed by hunters. One man, who professes to know all about it, says that the hunters use a spear having a cross-piece a couple of feet from the point. Hunter presents point to Ursus; Ursus seizes spear by cross-piece, and in trying to drag it away buries the blade in his own body, and so kills himself.
And this: Stout as he is, Ursa maritimus has to use cunning to get a living. He relies mainly upon walruses and seals. Though quite competent to manage the biggest walrus singly, he is overmatched by a herd; and unluckily for him walruses are apt to go in herds. He can not pick up a "junger" without bringing down upon him a score of tusked cousins and uncles. Then the seals are so shrewd. In the water they do not fear him. They can outswim and outdive him. There they will play around him in a manner calculated to aggravate his feelings to the utmost. Mr. Lamont thinks he catches one in the water now and then, but he can not con- ceive how he does it. Upon the ice Ursa has the advantage. But the seals know this, and sleep with both ears and one eye open. But Ursa's eyes and nose are of the sharpest. When either of these tell him that seals are floating about on the ice he slips into the water, half a mile or so to the leeward, and paddles quietly along, with his nose only visible, until he is close under the cake of ice on the very edge of which the seal is reposing. Then one jump, and a blow of his huge paw, settles the business. Between strength and cunning Ursa manages to make a quite comfortable living, and keep himself in very good order. Three which Mr. Lamont killed yielded 600 pounds of fat. "What a thousand pities," he exclaims, "that it is not worth 3s. 6d. a pot, as in the Burlington Arcade!"
Came across these studies related to Polar bears & their relationship with other polar bears.
"Cannibalism has been observed various times in polar bears (Ursus maritimus) (Lunn and Stenhouse, 1985; Taylor et al., 1985; Derocher and Taylor, 1994; Derocher and Wiig, 1999). On 17 October 2000 at 0900, an adult male bear (> 5 years) feeding on a bear carcass was spotted approximately 800 m north of the observation tower, 500 m south of the Hudson Bay shoreline and 20 m from a tundra vehicle trail. Wounds and blood on the neck, the right facial area, and the right shoulder area were observed on the adult male. Aside from these wounds, the bear appeared to be in good condition and well nourished. A single adult female bear with fresh wounds on her right front leg was spotted on a small gravel island within the lake, approximately 200 m to the east of the male bear and the carcass. She was observed lying down, mostly facing the male and carcass. Female polar bears often stay with slain cubs (Taylor et al., 1985). We therefore speculated from this female’s behaviour and her fresh wounds that she might have been the mother of the dead bear. Taylor et al. (1985) suggested that cannibalism is not rare, basing this conclusion on the observed levels of Trichinella larvae in polar bear populations across the circumpolar basin. Cannibalism by male polar bears for nutritional benefit was suggested by Lunn and Stenhouse (1985), Taylor et al. (1985), and Derocher and Wiig (1999). The frequency of cannibalism for the western Hudson Bay population is unknown. Considering the intensity of ongoing population studies in this area, and the paucity of observation of cannibalism, it seems likely this is not a common occurrence. Claws of cubs have been found in polar bear scats (Russell, 1975), and direct observations of bears feeding on conspecifics have been reported (R. Brook, pers. comm. 2000)"
This info explains the difficulty of determining the causes of deaths in Polar bears, but suggests likely reasons -
"Causes of natural mortalities among polar bears are largely unknown. Because polar bears spend most of their time on drifting seaice, dead animals are likely to go undiscovered and cause of death for animals that are discovered is seldom discernible. Therefore, we are forced to extrapolate from a very few observations to understand natural mortality patterns and causes." The causes they list include - Accidents involving unskilled young must be a common cause of natural death in the harsh arctic environment. Starvation of independent young as well as very old animals must account for much of the natural mortality among polar bears. Injuries sustained in fights over mates or in predation attempts also may lead to natural mortalities of polar bears.
I found this most interesting - "Injuries sustained in fights over mates or in predation attempts also may lead to natural mortalities of polar bears. Some injuries are immediately fatal. I have seen three instances where a bear has killed another and consumed it. Broken teeth and even broken jaws may frequently result from fighting and failed predation attempts. In brown and black bears, such injuries commonly are not life-threatening. L. Aumiller (Alaska Department of Fish and Game, pers. commun.) has observed several brown bears at Alaska's McNeil River Sanctuary with jaws that had broken and healed in a variety of distorted conformations. D. Garshelis (Minnesota Department of Natural Resources, pers commun.) captured a 2-year-old black bear with a missing lower jaw. The jaw and all lower teeth were destroyed by gunshot wounds that had largely healed when Garshelis examined the bear in its winter den. The bear was radio-tracked through the following spring and summer and killed by a hunter the following autumn as a normal-size 3-year-old. Brown bears and black bears often survive on a diet including plant parts, fish, insects, small animals, and carrion. A videotape made by the hunter revealed how ingenious the young Minnesota black bear was in feeding without a lower jaw. These and other observations of injured brown and black bears (D. Moody, Wyoming Game and Fish Department, Pers. Commun.; M. Haroldson, USGS Interagency Grizzly Bear Study Team, pers. commun.) suggest they regularly survive with severely damaged mouth-parts, perhaps because of their great adaptability and the small particle size of most of their foods."
Polar bears only rarely catch seals in open water. They are far more successful at hunting them on the sea ice. On the ice, the bears catch their prey when they surface to breathe.
Rifts in the ice, called leads, give seals access to oxygen. Seals also surface to breathe at polynyas, areas of open water surrounded by ice.
Polynyas are created by a combination of winds, tidal currents, and upwellings of water. They remain open throughout the winter months.
In addition to surfacing at leads and polynyas, seals cut breathing holes in the ice. The Inuit call these holes aglus.
In fall, each seal cuts ten to fifteen aglus in the ice, using the sharp claws on their foreflippers. They keep the aglus open throughout the winter, even when the ice is six feet deep.
Seals swim to the surface to breathe every five to fifteen minute. But because they visit as many as fifteen breathing holes, a polar bear's wait for its prey can be long.
Polar bears locate breathing holes with their powerful sense of smell. When a bear finds an aglu, it waits patiently for the seal to surface — which can take hours or days.
Polar bears depend on the presence of ice for access to seals. In summer, when the floes retreat north, polar bears will travel hundreds of miles to maintain contact with their prey.
Between summer and winter the amount of ice-covered water can change rapidly. Polar bears learn to follow the ice to stay with their food source.
Those polar bears that are stranded on land in summer must stay there until the ice forms again in fall. On land, the bears face lean times, for they seldom catch seals without a platform of ice.
Sources: Polar Bears by Ian Stirling (University of Michigan Press, 1988); Polar Dance by Fred Bruemmer (Images of Nature, 1997).
Polar bear with seal kill
taipan
More Polar Bears Giving Birth on Land Sunday 28 January 2007
Pregnant polar bears in Alaska, which spend most of their lives on sea ice, are increasingly giving birth on land, according to researchers who say global warming is probably to blame. The study by three scientists for the U.S. Geological Survey suggests the state's bear population could be harmed if the climate continues to grow warmer. Though bears are powerful swimmers, at some point they might have to cross vast stretches of open water to reach habitat on shore suitable for building dens in which to give birth.
From 1985 to 1994, 62 percent of the female polar bears studied dug dens in snow on sea ice. From 1998 to 2004, just 37 percent made dens on ice. The rest dug snow dens on land, according to the study. Researchers "hypothesized that the sea ice changes may have reduced the availability or degraded the quality of offshore denning habits," said wildlife biologist Anthony Fischbach, lead author of the study. In recent years, Arctic pack ice has formed progressively later and melted earlier each season, he said.
The study is under review by the Geological Survey. Fischbach spoke about the findings Monday at the Alaska Marine Science Symposium. Scientists estimate the Beaufort Sea polar bear population at 1,526. In the study, researchers used satellite technology to track 89 bears in northern Alaska that led them to 124 dens between 1985 and 2004.
"Cannibalism has been observed various times in polar bears (Ursus maritimus) (Lunn and Stenhouse, 1985; Taylor et al., 1985; Derocher and Taylor, 1994; Derocher and Wiig, 1999). On 17 October 2000 at 0900, an adult male bear (> 5 years) feeding on a bear carcass was spotted approximately 800 m north of the observation tower, 500 m south of the Hudson Bay shoreline and 20 m from a tundra vehicle trail. Wounds and blood on the neck, the right facial area, and the right shoulder area were observed on the adult male. Aside from these wounds, the bear appeared to be in good condition and well nourished. A single adult female bear with fresh wounds on her right front leg was spotted on a small gravel island within the lake, approximately 200 m to the east of the male bear and the carcass. She was observed lying down, mostly facing the male and carcass. Female polar bears often stay with slain cubs (Taylor et al., 1985). We therefore speculated from this female’s behaviour and her fresh wounds that she might have been the mother of the dead bear. Taylor et al. (1985) suggested that cannibalism is not rare, basing this conclusion on the observed levels of Trichinella larvae in polar bear populations across the circumpolar basin. Cannibalism by male polar bears for nutritional benefit was suggested by Lunn and Stenhouse (1985), Taylor et al. (1985), and Derocher and Wiig (1999). The frequency of cannibalism for the western Hudson Bay population is unknown. Considering the intensity of ongoing population studies in this area, and the paucity of observation of cannibalism, it seems likely this is not a common occurrence. Claws of cubs have been found in polar bear scats (Russell, 1975), and direct observations of bears feeding on conspecifics have been reported (R. Brook, pers. comm. 2000)"
Global warming turns polar bears cannibalistic: study
POLAR bears in the southern Beaufort Sea - part of the Arctic Ocean - may be turning to cannibalism because longer seasons without ice keep them from getting to their natural food, a study by American and Canadian scientists has found.
The study reviewed three examples of polar bears preying on each other from January to April 2004 north of Alaska and western Canada, including the first-ever reported killing of a female in a den shortly after it gave birth.
Polar bears feed primarily on ringed seals and use sea ice for feeding, mating and giving birth.
Polar bears kill each other for population regulation, dominance and reproductive advantage, the study said.
Killing for food seems to be less common, said the study's principal author, Steven Amstrup of the US Geological Survey's Alaska Science Centre.
"During 24 years of research on polar bears in the southern Beaufort Sea region of northern Alaska and 34 years in north-western Canada, we have not seen other incidents of polar bears stalking, killing and eating other polar bears," the scientists said.
Environmentalists contend shrinking polar ice due to global warming may lead to the disappearance of polar bears before the end of the century.
The Centre for Biological Diversity of Joshua Tree, California, in February 2005 petitioned the US Government to list polar bears as threatened under the federal Endangered Species Act.
Cannibalism demonstrates the effect on bears, said the lead author of the petition, Kassie Siegel.
Deborah Williams of Alaska Conservation Solutions, a group that pursues solutions for climate change, said the study represented the "bloody fingerprints" of global warming.
At the other end of the earth, a tourism boom is putting pressure on the Antarctic, polar scientists said on Monday.
Opening an international meeting in Edinburgh, Scotland, they noted that tourism had quadrupled to 32,000 in the past eight years.
In a disturbing trend Polar Bears are killing and eating each other because of an increasing difficultly in obtaining their primary food source, say the authors of a new study. The bears use sea ice to hunt for their prey, ringed seals, however with polar ice decreasing the bears are finding it harder and harder to catch the seals. Out of hunger, it seems the bears are resorting to cannibalism.
Researchers say this is an effect of global warming, and have petitioned to have Polar Bears listed as an endangered species. In over two decades of study in the region of North Alaska, scientists have never witnessed Polar Bears killing each other for food.
I wonder if this news will have an impact on the average person in the street. Melting glaciers may not be the most exciting news piece to alarm the general public, but cute, lovable polar bears eating each other? That most certainly is not a Coke ad.
body size The polar bear is the largest of the extant bears (DeMaster and Stirling 1981). In Hudson Bay, the mean scale weight of 94 males >5 years of age was 489 kg. The largest bear in that group was a 13-year-old, which weighed 654 kg (Kolenosky et al. 1992). The heaviest bear we have weighed in Alaska was 610 kg, and several animals were heavy enough that we could not raise them with our helicopter or weighing tripod. Some animals too heavy to lift have been estimated to weigh 800 kg (DeMaster and Stirling 1981). Females are smaller, with peak weights usually not exceeding 400 kg. Total lengths of males in the Beaufort Sea of Alaska ranged up to 285 cm. Such an animal may reach nearly 4 m when standing on its hind legs and is 1.7 m shoulder height when standing on all four legs. Chest girth for large males is close to 200 cm. Although smaller, females in the Beaufort sea were as long as 247 cm with chest girths up to 175 cm. Only prehistoric polar bears and the giant short-faced bear (Arctodus spp.) of the Pleistocene were of greater stature than today's polar bears (Kurt´en 1964; Stirling and Derocher 1990). http://www.polarbearsinternational.org/polar-bears-in-depth/description/
Kolenosky, George B., Pond, Bruce A., and Abraham, Kenneth F. Population characteristics of polar bears in southern Hudson Bay. Int. Conf. Bear Res. and Manage. 9, 301. 1994.
Abstract: During 1984-86, we captured 457 different polar bears (Ursus maritimus) 536 times along the Ontario coast of southern Hudson Bay.? The sex ratio of different bears captured (53 M:47 F) was similar (P = 0.30).? The mean age of captured males and females was 6.9 and 5.5 years, respectively.? The calculated mean annual survival rate for males and females was 0.89 and 0.85, respectively.? The mean natality rate for females ages 5-21 was 0.85.? Seventy-five percent of females _ 5 years were accompanied by young.? Most females produced their first litters at age 5 or 6.? There was no evidence of reproductive senescence in our samples as 4 of 6 females _ 19 years were accompanied by young.? Mean summer litter sizes ranged from 1.4 to 1.8 and averaged 1.6.? Weights of solitary females considered to be pregnant (338 ? 43 kg, N = 20) were heavier than the non-pregnant group (283 ? 47 kg, N = 14).? When captured, 38% of the yearlings were alone, suggesting a 2-year breeding interval.? We estimated a population of about 900 in southern Hudson Bay in 1985 and 1986. http://www.ursusjournal.com/volumes/ursus9-text.htm#Ames
pterodectyle
Polar Bear
The Polar bear (Ursus maritimus) evolved from coastal populations of grizzly bears during the late Pleistocene period. The first recorded mention in North America was in 1794 by Captain Phipps in A Voyage towards the North Pole. Phipps called the bear Ursus maritimus, which is the scientific name by which it is known today. Other names such as Nanook, ice bear and white bear all identify the polar bear.
Polar bears have long bodies with a large neck and head. The tail is short and the claws are long with a slight curve. Colour ranges from the pure white of new coats in summer to coats with a yellowish cast or tinge in later winter and spring. The coat consists of an outer layer of glossy guard hair overlying thick underhair, which covers a heavy layer of sub-cutaneous fat. Short furry ears and dense fur between the pads of the feet complete the bear's arctic survival suit. Polar bears are the largest members of the bear family. Females grow until they are about 4 years old and attain maximum weights of 300 kg, but males, which continue growing until about 8 years of age, may weigh from 500 to 600 kg and measure between 2.5 and 3.5 m from nose to tail.
Polar Bear Population Predicted To Dwindle WIth Retreating Ice
Science Daily — Future reduction of sea ice in the Arctic could result in a loss of 2/3 of the world's polar bear population within 50 years according to a series of studies just released by the U.S. Geological Survey
Last December, Secretary of the Interior Dirk Kempthorne announced that the U.S. Fish and Wildlife Service (Service) was proposing to list the polar bear as a threatened species under the Endangered Species Act. In January 2008, following a one-year review period, the Service is expected to make a recommendation to Secretary Kempthorne on whether or not to list the polar bear as threatened.
To assist the Service in making that recommendation, Secretary Kempthorne requested USGS leadership in studies to inform the Service's deliberations on polar bear status. This information summarizes and integrates the results from a series of studies on polar bear populations, range-wide habitats and changing sea ice conditions in the Arctic.
In making the announcement last December, Secretary Kempthorne said: "I am directing the U.S. Fish and Wildlife Service and the U.S. Geological Survey to aggressively work with the public and the scientific community over the next year to broaden our understanding of what is happening with the species. This information will be vital to the ultimate decision on whether the species should be listed."
Specifically the USGS has improved knowledge on the status of three polar bear sub-populations, projected numbers of polar bears into the future in relation to sea ice and integrated the information into a range-wide assessment of polar bear status under scenarios of future climate change.
The newly-released USGS information, presented to the Service in the form of nine administrative reports to be open for public comment, will now be considered within the context of the Fish and Wildlife Service's one-year review. The Service will analyze it and other information provided by scientists, government agencies and the public in order to arrive at an informed and scientifically justifiable decision. That decision is due in January.
The team investigating the future of polar bears and their habitat included scientists from the USGS, other American and Canadian government agencies, academia and the private sector.
"This team has done a tremendous job in furthering polar bear science through the use of long-term observational measurements on polar bears, their habitats, and many other factors integrated into a range of new and traditional models," said Mark Myers, Director of the U.S. Geological Survey.
During a six-month period of intensive analysis of both existing and new data, the team documented the direct relationship between the presence of Arctic sea ice and the survival and health of polar bears. Polar bears depend on sea ice as a platform to hunt seals, their primary food. But sea ice is decreasing throughout their Arctic range due to climate change. Models used by the USGS team project a 42 percent loss of optimal polar bear habitat from the Polar Basin during summer, a vital hunting and breeding period, by mid-century.
In addition to forecasts, declines in habitat have been recorded throughout the Polar Basin over the past 20 years of observations. To project future sea ice conditions, USGS scientists used 10 general circulation models that best approximated observed trends in sea-ice loss and could be expected to do the best job of simulating future conditions. Scientists characterize their conclusions as conservative because even the best available models are believed to underestimate the actual decline in Arctic sea ice.
The reports are available to the public at the USGS's Polar Bear Finding Web page.
Note: This story has been adapted from a news release issued by US Geological Survey
Future reduction of sea ice in the Arctic could result in a loss of 2/3 of the world's polar bear population within 50 years according to a series of studies just released by the U.S. Geological Survey. (Credit: Photo by Christopher Szorc, Courtesy National Ice Service NOAA) http://www.sciencedaily.com/releases/2007/09/070907224237.htm
taipan
Here's one way the Polar Bear fishes
Diving polar bear confirms Inuit observations
27 September 2007 NewScientist.com news service
The Inuit people of the Arctic have always known about it. But no outsiders have witnessed it for 200 years: a polar bear fishing. Not by scooping the fish out of the water like a brown bear - but by plunging in and swimming.
Polar bears live mainly on seals caught on the sea ice, so the shrinking of the Arctic ice pack is a real worry (New Scientist, 6 May 2006, p 10). Now it seems they may have found other sources of food. Last August, researchers based in Iqaluit, Canada, watched an adolescent polar bear swimming in a river estuary packed with charr, a relative of salmon, that was migrating upstream. It caught about one fish an hour, swimming and peering into the water, then diving. In the two days they saw the bear, it caught three charr and three sculpin, a spiny fish that lives under rocks - which the bear seemed to lose enthusiasm for eating (Polar Biology, DOI: 10.1007/s00300-007-0338-3).
The closely related brown bear catches fish very differently, by lunging and splashing in shallow water. As young polar bears learn hunting techniques from their mothers, the team speculates that this fishing technique could be widespread. But while polar bears easily get enough energy from fat, meaty seals to warrant the effort of catching them, it is not clear if this will be true of the fish they catch.
From issue 2623 of New Scientist magazine, 27 September 2007, page 16
By Jonathan Amos Science reporter, BBC News, San Francisco
The jawbone is about 23cm long
What may be the oldest known remains of a polar bear have been uncovered on the Svalbard archipelago in the Arctic.
The jawbone was pulled from sediments that suggest the specimen is perhaps 110,000 or 130,000 years old.
Professor Olafur Ingolfsson from the University of Iceland says tests show it was an adult, possibly a female.
The find is a surprise because polar bears are a relatively new species, with one study claiming they evolved less than 100,000 years ago.
If the Svalbard jawbone's status is confirmed, and further discoveries can show the iconic Arctic beasts have a deeper evolutionary heritage, then the outlook for the animals may be more positive than some believe.
Age 'confidence'
"We have this specimen that confirms the polar bear was a morphologically distinct species at least 100,000 years ago, and this basically means that the polar bear has already survived one interglacial period," explained Professor Ingolfsson.
Largest of five living bear species of Ursus genus
Brown bear (U. arctos) is nearest evolutionary cousin
Two species able to produce fertile hybrid offspring
Highly specialised predator of seals - but will take other prey
Global population of polar bears may number 20-25,000
Most recent IUCN Red List status: Vulnerable
Previous oldest recovered remains are about 70,000 years old
____________________________________________
"And what's interesting about that is that the Eeemian - the last interglacial - was much warmer than the Holocene (the present).
"This is telling us that despite the ongoing warming in the Arctic today, maybe we don't have to be quite so worried about the polar bear. That would be very encouraging."
The jawbone's discovery is being presented here in San Francisco at the American Geophysical Union (AGU) Fall Meeting.
The specimen was found at Poolepynten on Prins Karls Forland, a narrow strip of land on the far west of the archipelago.
The sediments there are well-described, and record at least two glaciations sandwiched with marine sequences. In other words, they record periods when Poolepynten was alternately covered by ice and water.
These periods are understood in good detail by Professor Ingolfsson's team, so although direct dating at the dig site gives an age range for the bone of 80-140,000 years ago, the group is confident the specimen can be placed at the upper end of this scale.
London detour
The 23cm-long bone itself retains some critical details that have helped identify it.
"It is very well-preserved," Professor Ingolfsson told BBC News.
"We can measure various parameters, such as the cheek-teeth row-length, and the size of the hole made by the third molar - which is very characteristic of polar bears. We've compared all this, both to fossil and recent materials, and there's no question it's a polar bear." They speculate it was a female bear.
Researchers have studied the DNA of modern polar bears to try to gauge when the Arctic animals separated from brown bears, their nearest evolutionary cousins.
Different models have variously put the radiation as near as 70,000 years ago and as distant as 1-1.5 million years ago. One of the problems has been in finding the ancient specimens to put alongside, and constrain, these genetic estimates.
Until recently, one of the oldest polar bear specimens was thought to be British - a 70,000-year-old animal found at Kew Bridge in London.
The presumption was that the creature lived at a lower latitude during a period when ice sheets were more extensive.
But scientists are now confident the Kew animal was in fact a brown bear.
"It's a huge bear; it's a runner - a hunting bear," said Andy Currant, a palaeontologist from London's Natural History Museum. "It's got some of the features of a polar bear, but it's undoubtedly a brown bear.
"With something like polar bears, to make an identification you've got to have a skull or a lower jaw - they've got very reduced teeth, rather surprisingly, and you've got to see that. So I was interested to learn that [Ingolfsson's group] has that."
Hidden Arctic
Building up a more detailed picture of the ancient history of polar bears will be challenging, though. The animals spend much of their lives out on the ice, and when they die their remains are likely to be scavenged by other creatures or fall to the bottom of the Arctic Ocean. Finds will continue to be extremely rare.
The sediments record the passing of ice and water
Concern over the bears' future status centres on the observations of shrinking ice in what is a rapidly warming Arctic. The ice provides a platform from which to hunt ringed, and other, seals. If the ice is diminished and the bears cannot adapt quickly, many of them may be squeezed out of their ecological niche.
Professor Ingolfsson is hopeful the bears will cope - and believes the palaeo-record will offer some reassurance.
"The polar bear is basically a brown bear that decided some time ago that it would be easier to feed on seals on the ice. So long as there are seals, there are going to be polar bears. I think the threat to the polar bears is much more to do with pollution, the build up of heavy metals in the Arctic.
"This is just how I interpret it. But this is science - when you have little data, you have lots of freedom."
The team, which includes Professor Oystein Wiig from the University of Oslo, Norway, will develop its research on the Svalbard specimen by trying to extract DNA.
Here are some pics of a huge polar bear skull that I am currently restoring so that I can make a mold of it (and then casts to sell). The skull scores at 27.5" (17.5 inches long and 10 inches wide) - the biggest polar bear skull in the record books was about 29 3/4".
It is shown with the skull cast of a 500lb South African lion. Even though it is almost a pure carnivore, you still can see that the polar bear still has features of the mostly herbivorous brown bear from which it is believed to have split off from more than 100,000 years ago. The jaws are narrow and the molars blunt, though the width of the skull and bone ridges suggest a formidable bite pressure.
dasyurus
Polar Bears Listed as Threatened Species in U.S.
John Roach for National Geographic News
May 14, 2008
After delaying a decision for several weeks, the U.S. government today listed the polar bear as threatened under the Endangered Species Act (ESA), creating new protections for the bears in their Alaskan habitat.
But officials emphasized that the decision will not be used to determine U.S. climate policy.
At today's announcement, Secretary of the Interior Dirk Kempthorne noted the dramatic decline of Arctic sea ice as the greatest threat to the bears.
Polar bears live in the Arctic and hunt seals and other fatty marine mammals from sea ice. They also travel, mate, and sometimes give birth on the ice.
But sea ice is melting as the planet warms, and it is predicted to continue to do so for several more decades. (Related: "Shrinking Arctic Sea Ice Thinner, More Vulnerable" [March 18, 2008].)
"Because polar bears are vulnerable to this loss of habitat, they are—in my judgment—likely to become endangered in the foreseeable future," Kempthorne said during a press briefing.
Many scientists say human-induced global warming is directly responsible for the melting sea ice and have called for limits on greenhouse gas emissions to stem the loss.
But Kempthorne said that science is not yet able to link specific activities such as carbon dioxide emissions from a coal-fired power plant to impacts on individual polar bears.
Therefore, regulation of greenhouse gases from power plants, automobiles, and other sources is out of the scope of this legislation, he said.
"That would be a wholly inappropriate use of the Endangered Species Act," he said. "ESA is not the right tool to set U.S. climate policy."
Mixed Reactions
As part of the announcement, Kempthorne invoked a section of the Endangered Species Act that stipulates activities permissible under the Marine Mammal Protection Act are allowed to continue under the ESA.
Because the U.S. classifies the polar bear as a marine mammal, the rule means that the bear's new threatened status will not impact oil exploration within its habitat.
Subsistence harvesting of polar bears and interstate trade in native handicrafts made from the animals will also be allowed to continue.
However, the listing means that import of polar bear products from Canada—where trophy hunting is still legal—will now be banned.
Reactions to today's announcement were a mixed bag of elation and frustration.
Scott Bergen is a landscape ecologist with the New York-based Wildlife Conservation Society and a contributing author to a spate of U.S. Geological Survey studies released in 2007 that found two-thirds of the world's polar bears could go extinct by 2050.
He and other WCS staff are "almost elated" with the decision, he said.
"Even though it doesn't directly influence carbon emissions so to speak, we think it is a definite decision in the right direction and we're pleased to see the Fish and Wildlife Service is supporting the best science on this species," he added.
Kassie Siegel, climate program director with the Center for Biological Diversity in Joshua Tree, California, wrote the petition seeking U.S. protections for the polar bear.
"[The] listing is great news for the polar bear, there's no question about that," she said. "The Endangered Species Act provides broad and strong protection. I think it's a watershed moment."
However, she added, the Bush Administration's attempt to exempt regulation of greenhouse gases in plans to protect the polar bear is illegal and wrong.
"We will be continuing to fight for the full protections that the polar bear needs and deserves," she said.
In a telephone briefing with reporters prior to today's announcement, Margaret Williams of the global conservation organization WWF said ESA listing is an important tool in polar bear protections.
"The ESA listing will require that critical habitat be identified [and] that a recovery plan be put into place, and those are important steps forward," she said.
"However, the bottom line is that climate change and warming temperatures are changing the Arctic dramatically, and that is the overall issue we need to address."
Global Efforts
Kempthorne noted that tackling global climate change and the melting Arctic sea ice requires the efforts all major economies in the world to be effective.
"That's why I'm taking administrative and regulatory action to make certain that the ESA isn't abused to make global warming policies," he said.
WCS' Bergen noted that saving the polar bear will hinge on international cooperation.
Permanent sea-ice habitat is likely to remain in areas outside of the U.S., particularly in Canada and Greenland.
Scientists view these slices of habitat as refuges that could allow some polar bear populations to survive over the long term and repopulate the Arctic if temperatures decrease and sea ice returns.
"If you take a long-term view—meaning a hundred-year view into the future," he said, "polar bears' existence is not necessarily totally dependent on what happens in the United States."
body size The polar bear is the largest of the extant bears (DeMaster and Stirling 1981). In Hudson Bay, the mean scale weight of 94 males >5 years of age was 489 kg. The largest bear in that group was a 13-year-old, which weighed 654 kg (Kolenosky et al. 1992). The heaviest bear we have weighed in Alaska was 610 kg, and several animals were heavy enough that we could not raise them with our helicopter or weighing tripod. Some animals too heavy to lift have been estimated to weigh 800 kg (DeMaster and Stirling 1981). Females are smaller, with peak weights usually not exceeding 400 kg. Total lengths of males in the Beaufort Sea of Alaska ranged up to 285 cm. Such an animal may reach nearly 4 m when standing on its hind legs and is 1.7 m shoulder height when standing on all four legs. Chest girth for large males is close to 200 cm. Although smaller, females in the Beaufort sea were as long as 247 cm with chest girths up to 175 cm. Only prehistoric polar bears and the giant short-faced bear (Arctodus spp.) of the Pleistocene were of greater stature than today's polar bears (Kurt´en 1964; Stirling and Derocher 1990). http://www.polarbearsinternational.org/polar-bears-in-depth/description/
That is quite different from: Anyone think that we should considering reevaluating coastal brownie vs. the Ice King?
taipan
Goose Eggs May Help Polar Bears Weather Climate Change
ScienceDaily (Dec. 15, 2008) — As polar bears adapt to a warming Arctic—a frozen seascape that cleaves earlier each spring—they may find relief in an unlikely source: snow goose eggs. New calculations show that changes in the timing of sea-ice breakup and of snow goose nesting near the western Hudson Bay could provide at least some polar bears with an alternative source of food. This new analysis appears in Polar Biology.
"Over 40 years, six subadult male bears were seen among snow goose nests, and four of them were sighted after the year 2000," says Robert Rockwell, a research associate in Ornithology at the American Museum of Natural History and a Professor of Biology at City College at City University of New York. "I've seen a subadult male eat eider duck eggs whole or press its nose against the shell, break it, and eat the contents. This is similar to a different research group's observations of polar bears eating Barnacle Goose eggs on Svalbard, an island near Norway."
Polar bears, Ursus maritimus, are listed as a threatened species under the United States' Endangered Species Act and are classified as "vulnerable with declining populations" under IUCN's Red List. Polar bears' habitat rings the Arctic south of 88˚ latitude. Most of this area is sea ice from which bears hunt seals, although the breakup of sea ice over the summer forces some bears to move north, to pack ice, or onto land. More often, it is subadult males that are pushed to these less ideal conditions, where they live, in part, off stored fat reserves.
When bears switch to the tundra in some areas, they may enter the nesting grounds of snow geese. Goose eggs and developing embryos are a highly nutritious source of food to opportunistic foragers. Although geese populations were in decline in the early 1900s, the population rebounded and expanded. There are now too many geese for the Arctic to support in the summer, mainly because their over-wintering habitat has increased to cover the northern plains, where they eat waste corn and forage in rice fields.
Polar bear and snow geese populations come into contact in the Hudson Bay. Here, some bears routinely live on land for 4-5 months of the year, subsisting on fat reserves. The new research shows that the effects of climate change will bring additional sources of food as the movement of both populations begins earlier each spring. Rockwell and his graduate student, Linda Gormezano, calculated that the rate of change in ice breakup is, on average, 0.72 days earlier each year, and that hatching time is also moving forward by 0.16 days each year. Current trends indicate that the arrival of polar bears will overlap the mean hatching period in 3.6 years, and egg consumption could become a routine, reliable option. At this point, a bear would need to consume the eggs of 43 nests to replace the energy gained from the average day of hunting seals. But within a decade, because timing changes would put bears in contact with even more nests with younger embryos (younger embryos are more nutritious), a bear would only need to consume the eggs of 34 nests to get the same amount of energy.
"Polar bears went through the Eemian 125,000 years ago, when sea level was 4-6 meters higher than it is now and trees lived above the Arctic Circle. They've been through warming before," says Rockwell. "I just read a piece in Natural History with a quote from Ilkoo Angutikjuak that sums this up: 'If the changes continue…the animals will adapt. I've heard that because they depend on sea ice, polar bears will go extinct, but I don't believe it…Polar bears might get skinnier and some might die, but I don't think they will go extinct.'"
Rockwell and Gormezano authored this research article, currently available in the early online version of Polar Biology. Research was funded by the Hudson Bay Project and the American Museum of Natural History.
May switch to eggs: sub-adult male polar bear near Churhchill, Manitoba, Canada.
Environmental stresses could be causing physical changes in the bears
Polar bears have shrunk over the last century, according to research.
Scientists compared bear skulls from the early 20th Century with those from the latter half of the century.
Their study, in the Journal of Zoology, describes changes in size and shape that could be linked an increase in pollution and the reduction in sea ice.
Physical "stress" caused by pollutants in the bears' bodies, and the increased effort needed to find food, could limit the animals' growth, the team said.
The researchers used the skulls as indicators of body size. The skulls from the later period were between two and 9% smaller.
Polar bears are one of the most polluted mammals on the globe - Christian Sonne, University of Aarhus
"Because the ice is melting, the bears have to use much more energy to hunt their prey," explained Cino Pertoldi, professor of biology from Aarhus University and the Polish Academy of Science, and lead scientist in this study.
"Imagine you have two twins - one is well fed during its growth and one is starving. (The starving) one will be much smaller, because it will not have enough energy to allocate to growth."
The team, which included colleagues from Aarhus University's Department of Arctic Environment, also found shape differences between the skulls from the different periods.
This development was slightly more mysterious, said Dr Pertoldi.
He explained that it was not possible to determine the cause, but that the changes could be linked to the environment - more specifically to pollutants that have built up in the Arctic, and in the polar bears' bodies.
The aim of the study was to compare two groups of animals that lived during periods when sea ice extent and pollution levels were very different.
The pollutants that the scientists focused on were compounds containing carbon and halogens - fluorine, chlorine, bromine or iodine.
Some of these compounds have already been phased out, but many still have important uses in industry. These include solvents, pesticides, refrigerants, adhesives and coatings.
The team used skulls from the Zoological Museum of Copenhagen
Genetic brink
The changes, the team says, could also be related to a reduction in the genetic diversity of the species.
Hunting over the last century, said Dr Pertoldi, could have depleted the gene pool, leaving polar bears to suffer the effects of inbreeding.
"We also know from previous studies that some chlorinated chemical pollutants have affected the fertility of the females," he continued.
Rune Dietz from Aarhus University was another member of the research team.
He explained that he and his colleagues had already determined a link between man-made "persistent organic pollutants" and reduced bone mineral density in polar bears - which could leave the animals vulnerable to injury and to the bone disease osteoporosis.
The maximum sea ice extent is declining by about 2.7% per decade
Skull collection
The collection of almost 300 polar bear skulls was provided by the Zoological Museum of Copenhagen in Denmark.
Christian Sonne, a veterinary scientist from Aarhus University who worked with the team, said that this provided a unique and "fantastic sample", providing a window into the bears' development over a whole century.
During that time, he said, concentrations of many man-made pollutants in the Arctic have significantly increased.
He said: "Polar bears are one of the most polluted mammals on the globe."
Page last updated at 09:52 GMT, Friday, 2 October 2009 10:52 UK By Jody Bourton Earth News reporter
A common occurrence?
Arctic waters are at best chilly and at worst close to freezing.
Which may explain why a polar bear cub has recently been seen riding on the back of its mother as the bears swim across parts of the Arctic Ocean.
The cub then briefly rode her back as she clambered out of the icy water, a unique event photographed by a tourist.
Experts have rarely seen the behaviour, and they say the latest find suggests it may be a more common practice than previously thought.
Dr Jon Aars from the Norwegian Polar Institute in Tromso describes what happened in the journal Polar Biology.
On the 21 July 2006, Mrs Angela Plumb, a tourist from the UK, was aboard a ship in the mouth of a fjord in the Svalbard archipelago.
Holidaying in the wildlife hotspot of Duvefjorden, Nordaustlandet, Mrs Plumb spotted the mother bear with a seven-month-old cub hitching a ride on her back.
"The cub was on the back of the polar bear when it was in the water, then it got out of the water and stayed on its mother's back a little, then she shook it off," Mrs Plumb explains.
For large parts of the year, polar bears (Ursus maritimus) live among the sea ice, feeding mainly on seals.
The challenge for the bears is to navigate the many areas of open water between the islands of floating ice.
Seeing the bear had a radio collar, Mrs Plumb got in touch with Dr Aars to report her sighting and asked if this was a common behaviour.
"I hadn't seen this behaviour before or heard about it so I asked other researchers and found out it is something that has been observed but not frequently at all," Dr Aars says.
Out of the cold
Cubs are known to ride their mother's back when moving through deep snow as they leave their den areas.
Cubs of other bear species such as the sloth bear also ride on their parents.
However, the the extent to which polar bear cubs hitch a ride on swimming adults in open water is unknown.
Dr Aars was especially interested if this behaviour might have some adaptive value for the bears.
"This could be potentially important because it means that the cubs get exposed to less water. If they are in the water they would have to swim and very small cubs are very badly insulated in water," he says.
Adults are well adapted to swimming in the cold water with insulating subcutaneous fat and and large body mass.
However, young bears have very little insulating fat, as they do not develop brown fat stores until adulthood. Their fur coat also loses most of its insulating properties if immersed in ice water.
Dr Aars suggests staying out of the water could be vital for the cub's ability to survive in habitats where sea ice is scattered across open ocean.
Speedy transport
Another reason for the behaviour could be that it aids the mother's mobility in the water.
"I would imagine a big benefit is the ride is faster, an adult female polar bear is a strong swimmer, cubs of this size are much slower and time in water is time lost hunting," suggests Professor Andrew Derocher from the University of Alberta, Edmonton, Canada.
"The mother would rather put her time into gaining more food by reaching good habitat rather than swimming and using energy," he explains.
The scientists are interested to find out if this behaviour might be a regular occurrence within the polar bear population.
"It's important to remember the vast areas it may happen in. It has not been observed that much, but it could be more common than we think," says Dr Aars.
Prof Derocher also wonders if the people who share the bears' habitat might be able to help unravel this behaviour.
"It would be interesting to hear if Inuit have seen this behaviour, I'm always very impressed that our observations match what local people have seen before, but they don't tell you about them unless you ask."
Heres some cases of Polar Bears killing adult Male Walrus. Two killing scenarios of adult male walrus 1. If their 'hole' freezes over the Walrus has no escape, no 'herd protection' and it therefore becomes a 1 on 1 fight, which based on these accounts the Polar Bear wins.
" In 2 cases, the haulout hole near the carcass was still unfro- zen, suggesting the walruses were killed on the ice before they could escape, and that freezing-out was not a factor. There was blood soaked into the snow beneath the head of the adult male found dead in February 1987 at the shoreline tidal cracks below our camp (site 11), suggest- ing that a bear killed him, though possibly only after the ice shifted and he was frozen out."
2. Even if the Walrus escapes to its hole, the bear must club it to death when it surfaces, and then drags out the carcass!!
"The date of death is known only for the kill at site 2 where the bear was observed killing a large adult male walrus and pulling it from its haulout hole (D. Grant, pers. commun.)."
Polar bears eating young due to shrinking sea ice: Scientists Bob Weber THE CANADIAN PRESS Published On Fri Nov 27
Scientists fear polar bears won't survive severe climate change.
Scientists say shrinking Arctic sea ice may be forcing some polar bears into cannibalizing young cubs.
"When (bears) are very hungry, they go looking for something to eat," biologist Ian Stirling said Friday. "There's nothing much to eat along the Hudson Bay coast in the fall other than other bears."
So far this fall, tour operators and scientists have reported at least four and perhaps up to eight cases of mature males eating cubs and other bears in the population around Churchill, Man. Four cases were reported to Manitoba Conservation; four to Environment Canada.
"That's a very big number," said Stirling, a retired Environment Canada scientist, who has studied the Churchill population for 35 years.
"I worked there well over 30 years and never saw a single case of cannibalism."
Bears lose up to 30 per cent of their body mass as they spend the summer and autumn on land waiting for the sea ice to refreeze so they can use it as a platform to hunt seals.
They used to be able to get out on the ice of Hudson Bay by early November, but freeze-up is now weeks later. This year, as December approaches, it still isn't solid enough for the bears.
Bill Watkins, a zoologist with Manitoba Conservation, reports he hears about one or two cases of cannibalism a year. He said it's possible more cases have been seen this year because more tourists are on the land, but he also suspects a climate change link.
"We would really need several years of data like this to confirm that something unusual's going on," he said. "While it's very suggestive of an impact of climate change, it's a little early to confirm that definitively."
Nick Lunn, another Environment Canada scientist who's spent decades studying the bears of Wapusk National Park near Churchill, said he saw polar bears eating other polar bear carcasses four times this fall. He couldn't confirm the bears killed their meal themselves, but he suggested the number of cases was startling.
"I've been working there since the early 1980s and I have never come across (four) cases of bears feeding on the remains of bears before. There's something going on."
The cases may be increasing.
Stirling said between 2004 and 2006, he and other researchers found evidence of cannibalism in the carcasses of three adult females and one yearling.
"Killed, simply to be eaten."
He added that there have also been four cases of such cannibalism in the past several years among the southern Beaufort population in Canada's northwest corner.
Adult males killing young of their species isn't unknown among animals, especially bears. But in most cases it happens in the spring so the male can then impregnate the sow he has left without cubs.
The timing of the recent killings suggests hunger may be the motivation, said Stirling, because "the females aren't going to be reproductively receptive until next spring."
Stirling's research has shown for years that the condition of the bears around Churchill is slowly deteriorating. Adult females are weighing less and less.
The Hudson Bay bears are considered Canada's most vulnerable bear population. Scientists point to them as an example of what may happen to other bears as Arctic sea ice continues to shrink.
A group of specialists recommended over the summer that, in light of sea ice trends, Canada should reconsider its decision not to include the mighty predators on its list of endangered species.
Canada has 13 of the world's 19 bear populations, which amounts to somewhere between 12,000 and 16,000 animals.
The International Union for the Conservation of Nature, one of the world's largest environmental science networks, considers eight bear populations to be in decline. Three populations are considered stable and one is increasing.
Information on seven populations is still too scarce for scientists to draw solid conclusions
Climate change not to blame for polar bear cannibalism
An adult polar bear with the remains of a cub. Scientists argue that climate change may be causing a spike in the rate of cannibalism among bears. 'Act of nature'
Alison Brownlee, National Post Published: Wednesday, December 09, 2009
The gory photos of male polar bears devouring cubs, dragging shredded carcasses around and creating a bloody mess on the white snow of Canada's North have caused a stir on the Internet and in reports that link the activity to climate change.
But cannibalism among the species is a natural occurrence, says one expert, disputing what is just the latest story to put the polar bear in the debate over man-made global warming.
"Both Inuit and scientific knowledge show that cannibalism in polar bears happens, and it probably always has," said Steve Pinksen, director of policy and legislation for Nunavut's Department of Environment.
The concern over cannibalism comes after a tourist group witnessed adult male bears attacking cubs for food. There have been at least eight reports of similar sights from Churchill, Man. The photos accompanying stories on the issue show bright-red remains strewn across blankets of snow.
Mr. Pinksen, however, called the incidents an "act of nature," and said the public reaction has been taken out of proportion.
"Maybe if you're sitting in an armchair in the city somewhere these pictures would be a shock, but people up here see these things all the time," he said, adding residents that are out hunting animals for food, clothing and income have seen evidence of these attacks in the past.
"A bear eating a bear is not a pretty picture, but nature is not really a pretty thing all the time," Mr. Pinksen said.
However, Dr. Ian Stirling, research scientist emeritus with the Canadian Wildlife Service, said the number of cannibalism incidents among polar bears is a result of warmer global temperatures. He said all species of bears experience cannibalism, but rates among polar bears have increased due to environmental changes.
"When we get a later-than-expected freeze up, that's when the bears get hungry," he said, adding the bears would usually be hunting seals and building up fat stores by now. Without a source of fat, the adult males target the vulnerable cubs, which are about 50% fat at six months old.
"If there was ice, the mothers would try to keep the cubs away from the males, for sure, but hundreds are waiting in the same general area for ice to form," Dr. Stirling said.
With the bears landlocked, Dr. Stirling said the number of infanticides has increased dramatically from the previous one every two or three years.
"This is a situation aggravated and made worse by the steady warming of the climate and loss of sea ice. If it continues, in 50 years there won't be many cubs left in Canada and the Hudson's Bay region," he said. "There's not really anything we can do to protect the cubs in nature. The only thing to do is to curb the affects of global warming."
Polar bears have often been part of the climate change debate, whether in iconic photos of bears on ice floes used to illustrate stories about the reduction of Arctic ice, or in the debate about listing them as an endangered species. Some groups have sought that protected status for the bears, arguing they are in danger because of climate change, but local organizations say the bear numbers are steady - and that the "endangered" status would only hinder traditional hunts.
Mr. Pinksen, meanwhile, said more attacks on cubs are likely witnessed in Churchill because the polar bear population is dense due to ice not forming on Hudson's Bay, leaving more chance of tourists seeing bear cannibalism. But that doesn't necessarily mean more attacks are happening, According to a media release by Polar Bears International, the Churchill bears usually wait for Hudson's Bay to freeze, then walk the ice to hunt seals. The lack of ice so far this season has left bears with little recourse for food sources, resulting in cannibalism, said the release. It links the late freeze to global warming.
Mr. Pinksen said there is no evidence to connect the cannibalism to climate change.
"It's nice to see people paying attention to climate change, but we're hoping people can keep a cooler head regarding arctic resource management," he said.
Polar Bears Changing Habitat in Response to Sea Ice Conditions
ScienceDaily (Jan. 7, 2010) — A long-term study showing the changes in habitat associations of polar bears in response to sea ice conditions in the southern Beaufort Sea has implications for polar bear management in Alaska.
Karyn Rode, a polar bear biologist with the U.S. Fish and Wildlife Service in Anchorage, Alaska and one of the study's authors, says data collected between 1979 and 2005 show that polar bears in the region are occurring more frequently on land and in open water and less frequently on ice during the fall. This means there are increased chances for human/bear interaction. The paper was published in the December issue of Arctic -- the journal of the Arctic Institute of North America.
Polar bears were observed over the 27-year period by U.S. government Minerals Management Services staff as part of the fall bowhead whale aerial survey conducted annually in the southern Beaufort Sea. Ice conditions were also recorded.
Data showed that as ice conditions changed, bears were being found on different habitats. Between 1979 and 1987, 12% of bear sightings were associated with no ice. Between 1997 and 2005 however, 90% of bear sightings were associated with no ice.
"When bears were seen, they were more often seen in open water and on land than on sea ice. At the same time, changes were observed in ice, suggesting that these observations are connected," says Rode.
In addition, the number of bears sighted steadily increased from 138 bears in the years 1979-1987, to 271 bears between 1988 and 1996, and finally to 468 bears between 1997 and 2005. Rode warns that this study was not designed to estimate the number of bears using the nearshore area. Data were drawn from studies created to track bowhead whale migration routes, not polar bear populations. Therefore, it should not be concluded that more bears are occurring in the nearshore waters off the Southern Beaufort Sea coast.
However, Rode states that "Our results do suggest that bears that use the nearshore area are more likely to occur on land in recent years because their preferred habitat, sea ice, is unavailable.
"This is one of the few data sets available over such a long time frame. It shows there has been a shift in habitat use," she says.
In the Beaufort Sea region, there was less ice in 2005 than when the study period began in 1979. In general, freeze up is later and spring melt comes earlier with measurements showing since 1979 the summer melt period has increased by 13 days per decade. This is one reason for the region's rapid retreat of multi-year ice, which provides a thicker, more stable platform for hunting and denning.
This work is helpful in highlighting the need to proactively develop programs to manage bear-human interactions in coastal areas. Bear-human interactions in Native villages and with industry in Alaska have been on the rise in recent years.
This media release is part of the Promotion of Arctic Science, an Arctic Institute of North America project made possible with the generous support of the Government of Canada Program for International Polar Year.
The mission of the Arctic Institute of North America at the University of Calgary is to advance the study of the North American and circumpolar Arctic and to acquire, preserve and disseminate information on physical, environmental and social conditions in the North. More information can be found at [url]www.arctic.ucalgary.ca[/url]
The Hudson bay bears appear to be very massive: The polar bear is the largest of the extant bears (DeMaster and Stirling 1981). In Hudson Bay, the mean scale weight of 94 males >5 years of age was 489 kg. The largest bear in that group was a 13-year-old, which weighed 654 kg (Kolenosky et al. 1992). The heaviest bear we have weighed in Alaska was 610 kg, and several animals were heavy enough that we could not raise them with our helicopter or weighing tripod. Some animals too heavy to lift have been estimated to weigh 800 kg (DeMaster and Stirling 1981). Females are smaller, with peak weights usually not exceeding 400 kg. Total lengths of males in the Beaufort Sea of Alaska ranged up to 285 cm. Such an animal may reach nearly 4 m when standing on its hind legs and is 1.7 m shoulder height when standing on all four legs. Chest girth for large males is close to 200 cm. Although smaller, females in the Beaufort sea were as long as 247 cm with chest girths up to 175 cm. Only prehistoric polar bears and the giant short-faced bear (Arctodus spp.) of the Pleistocene were of greater stature than today's polar bears (Kurt´en 1964; Stirling and Derocher 1990). From here.
Beaufort Sea bears appear to be smaller. I'm sure more data than this exists, although someone would have to spend some time finding all of it in the future.
Thank you Ursus Arctos.
Polar bears prey heavily throughout their range on ringed seals (Phoca hispida) and, to a lesser extent, bearded seals (Erignathus barbatus) and in some locales, other seal species. Although seals are their primary prey, polar bears also have been known to kill much larger animals such as walruses (Odobenus rosmarus), narwhal (Monodon monoceros) and belugas (Delphinapterus leucas) (Stirling and Archibald 1977, Kiliaan et al. 1978, Smith 1980, 1985, Lowry et al. 1987, Calvert and Stirling 1990, Smith and Sjare 1990).
Adult males have been recorded weighing 654 kg (1440 pounds) (Kolenosky et al. 1992), with some individuals too large for the weighing equipment, estimated at 800 kg (1760 pounds) (DeMaster and Stirling 1981). Adult females weigh 181 to 317 kg (400-700 pounds). Adult males range in nose to tail length from 230 to 285 cm (7.5 - 9.3 feet) and adult females range in length from 180 to 2.40 cm (6-8 feet) (Amstrup 2003, Stirling 1988).
Body weights of mothers and their cubs decreased markedly in the mid-1970s in the Beaufort Sea following a decline in ringed and bearded seal pup production (Stirling et al. 1976, 1977b, Kingsley 1979, DeMaster et al. 1980, Stirling et al. 1982, Amstrup et al. 1986).
Stirling et al. (1999) reported a significant decline in body condition (weights) of both male and female adult polar bears since the 1980s in Western Hudson Bay, which was interrupted by improved condition in 1992 and 1993.
Body weights for adult males decreased significantly and skull measurements were reduced since 1990. Since male polar bears continue to grow into their teen years (Derocher et al. 2005, p. 898), if nutritional intake was similar since 1990, the size of males should have increased (Regehr et al. 2006, p. 18). The observed changes reflect a trend toward smaller size adult male bears. Although a number of the indices of population status were not independently significant, nearly all of the indices illustrated a declining trend.
By Jonathan Amos Science reporter, BBC News, San Francisco
The jawbone is about 23cm long
What may be the oldest known remains of a polar bear have been uncovered on the Svalbard archipelago in the Arctic.
The jawbone was pulled from sediments that suggest the specimen is perhaps 110,000 or 130,000 years old.
Professor Olafur Ingolfsson from the University of Iceland says tests show it was an adult, possibly a female.
The find is a surprise because polar bears are a relatively new species, with one study claiming they evolved less than 100,000 years ago.
If the Svalbard jawbone's status is confirmed, and further discoveries can show the iconic Arctic beasts have a deeper evolutionary heritage, then the outlook for the animals may be more positive than some believe.
Age 'confidence'
"We have this specimen that confirms the polar bear was a morphologically distinct species at least 100,000 years ago, and this basically means that the polar bear has already survived one interglacial period," explained Professor Ingolfsson.
Largest of five living bear species of Ursus genus
Brown bear (U. arctos) is nearest evolutionary cousin
Two species able to produce fertile hybrid offspring
Highly specialised predator of seals - but will take other prey
Global population of polar bears may number 20-25,000
Most recent IUCN Red List status: Vulnerable
Previous oldest recovered remains are about 70,000 years old
____________________________________________
"And what's interesting about that is that the Eeemian - the last interglacial - was much warmer than the Holocene (the present).
"This is telling us that despite the ongoing warming in the Arctic today, maybe we don't have to be quite so worried about the polar bear. That would be very encouraging."
The jawbone's discovery is being presented here in San Francisco at the American Geophysical Union (AGU) Fall Meeting.
The specimen was found at Poolepynten on Prins Karls Forland, a narrow strip of land on the far west of the archipelago.
The sediments there are well-described, and record at least two glaciations sandwiched with marine sequences. In other words, they record periods when Poolepynten was alternately covered by ice and water.
These periods are understood in good detail by Professor Ingolfsson's team, so although direct dating at the dig site gives an age range for the bone of 80-140,000 years ago, the group is confident the specimen can be placed at the upper end of this scale.
London detour
The 23cm-long bone itself retains some critical details that have helped identify it.
"It is very well-preserved," Professor Ingolfsson told BBC News.
"We can measure various parameters, such as the cheek-teeth row-length, and the size of the hole made by the third molar - which is very characteristic of polar bears. We've compared all this, both to fossil and recent materials, and there's no question it's a polar bear." They speculate it was a female bear.
Researchers have studied the DNA of modern polar bears to try to gauge when the Arctic animals separated from brown bears, their nearest evolutionary cousins.
Different models have variously put the radiation as near as 70,000 years ago and as distant as 1-1.5 million years ago. One of the problems has been in finding the ancient specimens to put alongside, and constrain, these genetic estimates.
Until recently, one of the oldest polar bear specimens was thought to be British - a 70,000-year-old animal found at Kew Bridge in London.
The presumption was that the creature lived at a lower latitude during a period when ice sheets were more extensive.
But scientists are now confident the Kew animal was in fact a brown bear.
"It's a huge bear; it's a runner - a hunting bear," said Andy Currant, a palaeontologist from London's Natural History Museum. "It's got some of the features of a polar bear, but it's undoubtedly a brown bear.
"With something like polar bears, to make an identification you've got to have a skull or a lower jaw - they've got very reduced teeth, rather surprisingly, and you've got to see that. So I was interested to learn that [Ingolfsson's group] has that."
Hidden Arctic
Building up a more detailed picture of the ancient history of polar bears will be challenging, though. The animals spend much of their lives out on the ice, and when they die their remains are likely to be scavenged by other creatures or fall to the bottom of the Arctic Ocean. Finds will continue to be extremely rare.
The sediments record the passing of ice and water
Concern over the bears' future status centres on the observations of shrinking ice in what is a rapidly warming Arctic. The ice provides a platform from which to hunt ringed, and other, seals. If the ice is diminished and the bears cannot adapt quickly, many of them may be squeezed out of their ecological niche.
Professor Ingolfsson is hopeful the bears will cope - and believes the palaeo-record will offer some reassurance.
"The polar bear is basically a brown bear that decided some time ago that it would be easier to feed on seals on the ice. So long as there are seals, there are going to be polar bears. I think the threat to the polar bears is much more to do with pollution, the build up of heavy metals in the Arctic.
"This is just how I interpret it. But this is science - when you have little data, you have lots of freedom."
The team, which includes Professor Oystein Wiig from the University of Oslo, Norway, will develop its research on the Svalbard specimen by trying to extract DNA.
By Clara Moskowitz, LiveScience Senior Writer posted: 01 March 2010 01:40 pm ET
DNA from a polar bear jawbone has revealed the Arctic species first originated about 150,000 years ago, scientists announced today.
It has been known that polar bears evolved from brown bears, but until now, it wasn't clear when this happened.
The discovery was enabled by the rare jawbone find on the Norwegian island of Svalbard in 2004. Very few early polar bear fossils have been recovered so far, so their evolution has not been well understood.
"This really gave us a unique opportunity to try to estimate the origin date of the species," said study leader Charlotte Lindqvist of the University of Buffalo. "Polar bears as a species are fairly young and probably evolved fairy recently."
The jawbone, which is between 110,000 and 130,000 years old, provided the key to the polar bears' past, because it offered a sample of genetic material. The researchers drilled into a tooth on the bone to extract mitochondrial DNA, which is DNA from the energy-producing part of the cell called mitochondria. The scientists then sequenced this DNA and compared it with the DNA of modern polar bears, and modern brown bears from Alaska's Admiralty, Baranof and Chichagof Islands, which are the polar bear's closest relatives.
"We had to compare modern polar bears with this ancient polar bear and also the closest relatives of polar bears in order to reconstruct the family trees to understand their evolution," Lindqvist told LiveScience. "Polar bears actually originated from within brown bears. We found that this ancient polar bear is positioned almost directly at the splitting point between polar bears and brown bears – very close to the common ancestor."
In fact, the polar bear genome the researchers derived is the oldest mammal mitochondrial genome ever to be sequenced. The work was made possible by the most recent genome sequencing technologies, Lindqvist said.
Polar bears are an extremely specialized species. Whereas brown bears are more generalized and can survive in a variety of habitats, polar bears evolved to take advantage of a very specific ecological niche.
"Polar bears are very specialized to the habitat they live in on the edge of the Arctic sea ice," Lindqvist said. "They feed on a few species of seal and are very adapted to that habitat."
This specialization could make it more difficult for them to adapt to the changing climate. The species evolved to live on sea ice, and each year lately there is less and less of it.
"As the arctic sea ice is reduced the polar bears very well may lose lots of habitat," Lindqvist said. "If this trend continues we can only imagine that this must have a dramatic effect for their continued survival. Whether polar bears in the future will be able to adapt to warmer climates is hard to say."
The research was detailed in the March 1 issue of the journal Proceedings of the National Academy of Sciences.
Here two polar bear cubs snuggle up. The polar bears, which evolved from brown bears, originated some 150,000 years ago, according to genetic analyses of a polar bear fossil.
Surface area to volume ratios for the finite element models of polar and brown bear skulls were similar, indicating that similar amounts of bone are used in the skulls of both species (SA/V: polar bear = 0.61, brown bear = 0.59). This finding suggests that differences in stress magnitudes between the polar bear and scaled brown bear skull models can be interpreted in light of differences in external shapes of the skulls. Bite forces measured from the two scaled finite element models were also comparable for all simulated bites, although the polar bear's bite was slightly stronger in each case (Table 2, Fig. 2a). These results suggest that the potential leverage of the jaw muscle systems is also similar for the two species.
Stress distributions and magnitudes differed between the two models for all bites. For each biting scenario, the polar bear skull exhibited more widely varying stresses (Fig. 3) and higher peak stresses (Table 3) than for the brown bear. Differences between the two species were most marked for bites made with the molars, where peak stresses in the polar bear were up to 408% those of the brown bear (Table 3). Similarly strain energy values were higher in the polar bear cranium than for the brown bear for all bites (Table 2; Fig. 2b), indicating that the polar bear skull undergoes more deformation in producing similar bite forces. Again, differences between the polar and brown bear crania were most pronounced for bites made with the post-canine dentition, the main site for processing of ingested food. Our model results are unvalidated by in vivo data and should be treated as estimates only. However, based on our findings, it appears that although the two species are similar in cranial size and have similar muscle leverage potential, the polar bear's skull is a weaker, less work-efficient structure, and does not appear well suited to dealing with large masticatory loads.
The transition to an arctic environment and hypercarnivorous diet resulted in extremely rapid morphological evolution in the polar bear lineage. Our results indicate that the rate of cranial shape evolution in the polar bear lineage was at least twice as fast as in other branches of ursid phylogeny. Our estimate is probably conservative; while the phylogeny that we used for rate estimates dates the polar bear/brown bear split at ~700 kya [3], recent analysis of sub-fossil polar bear remains suggests that polar bears diverged from brown bears as recently as 150 kya, and that the modern polar bear morphology was present by 130 kya [17]. Compared with other ursids, polar bears possess low flat skulls with elevated orbits [2], consistent with both semi-aquatic [18] and faunivorous [2] adaptations. This morphology might also increase hunting efficiency by allowing bears to thrust their heads into breathing holes or pupping dens. Polar bear evolution was facilitated by the expansion of polar ice sheets and floes in the late Pleistocene [19]. If polar bears evolved from coastal populations of brown bears [6], as molecular evidence now suggests [3]–[5], [17], then rapid evolution of adaptations for semi-aquatic life and hypercarnivory could have occurred to facilitate foraging over wider areas. Polar bears have denser fore- and hindlimb bones, a common adaptation of aquatic mammals, than closely related brown bears, further supporting this interpretation [20].
Although polar bears possess mechanically efficient skulls, as indicated by larger bite forces for a given muscle effort (Fig. 2A), we found that they also possess energetically inefficient and structurally weaker skulls (Fig. 2b; Fig. 3). This initially seems somewhat counterintuitive; among other carnivoran families, more carnivorous taxa tend to have stronger skulls [11], [13], [14]. However, polar bears feed almost exclusively on young ringed (Pusa hispida) and bearded (Erignatus barbatus) seals, which, at 68–250kg, are small prey in comparison to a ~500 kg adult polar bear [21], [22]. As a result, cranial reinforcement may not be necessary as in hypercarnivores such as lions or wolves that regularly take prey larger than themselves [11], [13], [14]. The performance of the polar bear skull is particularly poor during bites with the post-canine dentition. (Fig 2b; Fig 3b–d; f–h). Polar bears exhibit reduced premolars and molars in comparison with most other ursids [1] but also lack the well-developed shearing blade-like teeth of hypercarnivores [1], [23]. In this respect they parallel insectivorous carnivorans, such as aardwolf (Proteles cristata), bat-eared fox (Otocyon megalotis) and sloth bear (Ursus ursinus) [1], [2]. Although convergence between a carnivore and insectivores also appears surprising, consideration of food material properties sheds light on this finding. Polar bears feed as almost exclusively on blubber and flesh that, unlike bone, require little or no processing prior to swallowing. If there is no selective advantage to maintaining large molars, they can be rapidly lost through the action of a few small mutations [24] or simple developmental mechanisms [25], [26]. Brown bears, in contrast, are generalized omnivores with unreduced dentitions [1], [2]. Although they consume animal protein when available, brown bears seasonally consume large amounts of plant material, including grasses, which require extensive mechanical breakdown and repeated skull loading prior to swallowing [27]. This is reflected in their larger molar grinding area, similar to other omnivorous ursids [1]. The lower peak stresses and higher work efficiency of the the brown bear cranium may result in part from the species' deep, vaulted and pneumatized forehead (see Fig. 3), a morphology that is characteristic of all herbivorous and omnivorous ursids [2]. Although pneumatized spaces are associated with reduced structural strength of the cranium [28], their presence is also associated with dissipation of regular, large peak masticatory loads in bone-cracking hyaenas and fossil canids [29]–[32]. The low, flat head of the polar bear, while advantageous for its semi-aquatic lifestyle and hunting behavior, reduces the ability of the cranium to withstand repeated large loads generated by bites made with the post-canine dentition.
Polar bear's epic nine day swim in search of sea ice
By Ella Davies Earth News reporter Page last updated at 09:16 GMT, Tuesday, 25 January 2011
A polar bear swam continuously for over nine days, covering 687km (426 miles), a new study has revealed.
Scientists studying bears around the Beaufort sea, north of Alaska, claim this endurance feat could be a result of climate change.
Polar bears are known to swim between land and sea ice floes to hunt seals.
But the researchers say that increased sea ice melts push polar bears to swim greater distances, risking their own health and future generations.
In their findings, published in Polar Biology, researchers from the US Geological Survey reveal the first evidence of long distance swimming by polar bears (Ursus maritimus).
"This bear swam continuously for 232 hours and 687 km and through waters that were 2-6 degrees C," says research zoologist George M. Durner.
"We are in awe that an animal that spends most of its time on the surface of sea ice could swim constantly for so long in water so cold. It is truly an amazing feat."
Although bears have been observed in open water in the past, this is the first time one's entire journey has been followed.
By fitting a GPS collar to a female bear, researchers were able to accurately plot its movements for two months as it sought out hunting grounds.
The scientists were able to determine when the bear was in the water by the collar data and a temperature logger implanted beneath the bear's skin.
The study shows that this epic journey came at a very high cost to the bear.
"This individual lost 22% of her body fat in two months and her yearling cub," says Mr Durner.
"It was simply more energetically costly for the yearling than the adult to make this long distance swim," he explains.
Swimming long distances puts cubs at risk
Mr Durner tells the BBC that conditions in the Beaufort sea have become increasingly difficult for polar bears.
"In prior decades, before 1995, low-concentration sea ice persisted during summers over the continental shelf in the Beaufort Sea."
"This means that the distances, and costs to bears, to swim between isolated ice floes or between sea ice and land was relatively small."
"The extensive summer melt that appears to be typical now in the Beaufort Sea has likely increased the cost of swimming by polar bears."
Polar bears live within the Arctic circle and eat a calorie-rich diet of ringed seals (Pusa hispida) to survive the frozen conditions.
The bears hunt their prey on frozen sea ice: a habitat that changes according to temperature.
"This dependency on sea ice potentially makes polar bears one of the most at-risk large mammals to climate change," says Mr Durner.
The IUCN red list identifies polar bears as a vulnerable species, citing global climate change as a "substantial threat" to their habitat.
ScienceDaily (July 8, 2011) — An international team of scientists has discovered that the female ancestor of all living polar bears was a brown bear that lived in the vicinity of present-day Britain and Ireland just prior to the peak of the last ice age -- 20,000 to 50,000 years ago. Beth Shapiro, the Shaffer Associate Professor of Biology at Penn State University and one of the team's leaders, explained that climate changes affecting the North Atlantic ice sheet probably gave rise to periodic overlaps in bear habitats. These overlaps then led to hybridization, or interbreeding -- an event that caused maternal DNA from brown bears to be introduced into polar bears.
The research, which is led by Shapiro and Daniel Bradley of Trinity College Dublin, is expected to help guide future conservation efforts for polar bears, which are listed as threatened under the Endangered Species Act. The results of the study will be published on 7 July 2011 in the journal Current Biology.
Polar and brown bears are vastly different species in terms of body size, skin and coat color, fur type, tooth structure, and many other physical features. Behaviorally, they are also quite distinct: Polar bears are expert swimmers that have adapted to a highly specialized, arctic lifestyle, while brown bears -- a species that includes Grizzlies and Kodiaks -- are climbers that prefer the mountain forests, wilderness regions, and river valleys of Europe, Asia, and North America. "Despite these differences, we know that the two species have interbred opportunistically and probably on many occasions during the last 100,000 years," Shapiro said. "Most importantly, previous research has indicated that the brown bear contributed genetic material to the polar bear's mitochondrial lineage -- the maternal part of the genome, or the DNA that is passed exclusively from mothers to offspring. But, until now, it was unclear just when modern polar bears acquired their mitochondrial genome in its present form."
Although previous researchers had suggested that the ancient female ancestor of modern polar bears lived on the ABC Islands -- the Alaskan islands of Admiralty, Baranof, and Chichagof -- only 14,000 years ago, Shapiro's team found evidence of a much earlier hybridization event. Because of this event, the modern polar bear's mitochondrial DNA probably underwent fixation -- a drastic reduction in genetic variation and a transition to a state in which the entire gene pool includes only one form of a particular gene. After performing genetic analyses of 242 brown-bear and polar-bear mitochondrial lineages sampled throughout the last 120,000 years and across multiple geographic ranges, Shapiro's team found that the fixation of the mitochondrial genome likely occurred during or just before the peak of the last ice age, possibly as early as 50,000 years ago, near present-day Ireland. Shapiro noted that the specific population of brown bears that shared its maternal DNA with polar bears has been extinct for roughly 9,000 years. However, her data offer clear genetic evidence that the two species were in contact long before the brown bear's disappearance from the British Isles.
Shapiro explained that, although both polar bears and brown bears have experienced long periods of geographic stability, episodes of both warming and cooling during the last 500,000 years or more likely led to environmental conditions favorable to hybridization between the two bear species. "Polar and brown bears likely came into contact intermittently, in particular in coastal regions where the effects of climate change may have been more pronounced," Shapiro said. "Whenever they come into contact, there seems to be little barrier to their mating."
Such climate changes, Shapiro said, included vast fluctuations in the amount and distribution of habitats in the North Atlantic region. These fluctuations would have caused the geographic ranges of polar and brown bears to overlap temporarily. For example, during a warming period, elevated air temperatures, melting glacial ice, and rising sea levels likely forced polar bears to spend more time onshore in search of food, and thus closer to their brown-bear neighbors. Likewise, during a cooling glacial period, brown bears living farther from the coast may have been forced into habitat normally occupied by polar bears. The British-Irish Ice Sheet reached its maximum extent about 20,000 years ago, with major tidewater glaciers on the western shelf and down the Irish Sea Basin into the Celtic Sea. During this period, parts of Ireland were probably uninhabitable because of glaciation, pushing brown bears toward ice shelves and land exposed by lower sea levels. "The bottom line is that the two species bumped up against one another for extended periods of time on different occasions, sharing both habitats and genes," Shapiro said.
Climatological data suggest that the planet now is experiencing another warming period -- known as the Holocene or the Present Interglacial -- which is even warmer than the period that marked the beginning of the last ice age. "Interestingly, today we are seeing a similar change in the arctic climate, with melting glacial ice, fewer sea-ice days, longer open-water periods during summer, and rising sea levels," Shapiro said. "And once again that change is providing polar and brown bears the opportunity to share habitats and to hybridize. In fact, several adult hybrid bears have been reported in the last five years." For this reason, Shapiro said, scientists should reconsider conservation efforts focused not just on polar bears, but also on hybrids, since hybrids may play an underappreciated role in the survival of certain species. She added that a thorough understanding of the polar bear's deep genetic history and its response to previous environmental changes could help to inform conservation strategies for the dwindling population of polar bears today.
Shapiro hopes to design future studies of the polar bear's DNA by concentrating on other parts of the animal's genome. "Until now we have focused our efforts on the polar bear's mitochondrial DNA, which traces only the mother's side of the family tree," Shapiro said. "But there is much to be learned from the nuclear genome -- the genetic material contained within the nucleus of the cell, which has been passed to offspring from both mothers and fathers." Shapiro said that a more complete investigation of this part of the genetic story could answer deeper questions about how interactions with other species and environmental changes affected the polar bear in the distant past, how frequently hybridizations between species actually happened, and how these hybridizations affected the genetic diversity of the polar bear generally.
In addition to Shapiro and Bradley, other researchers who contributed to the study include Tara L. Fulton at Penn State and scientists at universities and institutions in California, Ireland, the United Kingdom, Belgium, Spain, Denmark, Russia, and Sweden. The sequencing of ancient Irish and British bears was carried out by Ceiridwen Edwards at Trinity College Dublin, where the unprecedented similarity with polar bears was first noted.
Funding for the research was provided by the European Research Council; the National Evolutionary Synthesis Center (NESCent); the Irish Council for Science, Engineering, and Technology; and the U.S. National Science Foundation.
An international team of scientists has discovered that the female ancestor of all living polar bears was a brown bear that lived in the vicinity of present-day Britain and Ireland just prior to the peak of the last ice age -- 20,000 to 50,000 years ago. The research is expected to help guide future conservation efforts for polar bears, which are listed as threatened under the Endangered Species Act. Climate change has forced polar and brown bears to share habitats. Occasionally, the two species interbreed and produce hybrid bears.
Ceiridwen J. Edwards, Marc A. Suchard, Philippe Lemey, John J. Welch, Ian Barnes, Tara L. Fulton, Ross Barnett, Tamsin C. O'Connell, Peter Coxon, Nigel Monaghan et al. Ancient Hybridization and an Irish Origin for the Modern Polar Bear Matriline. Current Biology, 07 July 2011 DOI: [url]10.1016/j.cub.2011.05.058 [/url]
By Jonathan Amos Science correspondent, BBC News, San Francisco
It is an image that is sure to shock many people.
An adult polar bear is seen dragging the body of a cub that it has just killed across the Arctic sea ice.
Polar bears normally hunt seals but if these are not available, the big predators will seek out other sources of food - even their own kind.
The picture was taken by environmental photojournalist Jenny Ross in Olgastretet, a stretch of water in the Svalbard archipelago.
"This type of intraspecific predation has always occurred to some extent," she told BBC News.
"However, there are increasing numbers of observations of it occurring, particularly on land where polar bears are trapped ashore, completely food-deprived for extended periods of time due to the loss of sea ice as a result of climate change."
The journalist was relating the story behind her pictures here at the 2011 American Geophysical Union (AGU) Fall Meeting, the largest annual gathering of Earth scientists.
A paper describing the kill event in July 2010 has just been published in the journal Arctic. It is co-authored with Dr Ian Stirling, a polar bear biologist from Environment Canada.
Ross had approached the adult in a boat. She could see through her telephoto lens that the animal had a meal, but it was only when she got up close that she realised it was a juvenile bear.
The kill method used by the adult was exactly the same as polar bears use on seals - sharp bites to the head.
"As soon as the adult male became aware that a boat was approaching him, he basically stood to attention - he straddled the young bear's body, asserting control over it and conveying 'this is my food'," the journalist recalled.
"He then picked up the bear in his jaws and, just using the power of his jaws and his neck, transported it from one floe to another. And eventually, when he was a considerable distance away, he stopped and fed on the carcass."
Ross said there was another bear in the area and she speculated that it might have been the mother of the dead juvenile.
Olgastretet is a passage of water that divides the two main islands of Svalbard. Traditionally, it has been an area that has stayed ice-covered throughout the year.
But the recent dramatic retreat of Arctic sea ice in summer months has seen open water appear in the area for extended periods.
And without their customary platform on which to hunt seals, bears have gone looking for alternative sources of food, says Ross.
"On land, they're looking for human garbage and human foods; they're starting to prey on seabirds and their eggs.
"None of those alternative foods can support them, but they are seeking them out.
"Predating another bear is a way to get food; it's probably a relatively easy way for a big adult male. And it seems that because of the circumstances of the loss of sea ice - that kind of behaviour may be becoming more common."
Observations of cannibalism by polar bears (Ursus maritimus) on summer and autumn sea ice at Svalbard, Norway / Stirling, I. Ross, J.E. Arctic, v. 64, no. 4, Dec. 2011, p. 478-482, ill. ASTIS record 75088
We report three instances of intraspecific killing and cannibalism of young polar bears by adult males on the sea ice in Svalbard in summer and autumn. During breakup and melting in summer, the area of sea ice around the Svalbard Archipelago declines to a fraction of the winter total, and in many areas it disappears completely. As the area of sea ice that polar bears can use for hunting declines, progressively fewer seals are accessible to the bears, and therefore the bears' hunting success likely declines as well. Thus, at this time of year, young polar bears may represent a possible food source for adult males. As the climate continues to warm in the Arctic and the sea ice melts earlier in the summer, the frequency of such intraspecific predation may increase.
From Interactions between Polar Bears and Overwintering Walruses in the Central Canadian High Arctic: Between 1981 and 1989, we found evidence of 10 walruses that we believe were wounded or killed by polar bears (Fig. 1). The date of death is known only for the kill at site 2 where the bear was observed killing a large adult male walrus and pulling it from its haulout hole (D. Grant, pers. commun.). All the other carcasses were frozen and partially eaten when found. Wind-blown snow often obscured the bear tracks in the area, making it difficult to reconstruct the attack, but the presence of bear claw marks, blood smears, and scratching marks made by walrus flippers indicated an interaction had occurred. In 2 cases, the haulout hole near the carcass was still unfro? zen, suggesting the walruses were killed on the ice before they could escape, and that freezing-out was not a factor. There was blood soaked into the snow beneath the head of the adult male found dead in February 1987 at the shoreline tidal cracks below our camp (site 11), suggest? ing that a bear killed him, though possibly only after the ice shifted and he was frozen out. At 6 of 7 sites of kills or probable kills, polar bears were feeding on the carcass when it was sighted, but we did not know if they were predators or scavengers. Although walruses hit each other on the neck shoulder with their tusks when fighting, they are tected by a thick skin. Most wounds are superficial bleeding is limited. At site 3, there was no carcass, from the tracks we determined a bear had stalked walrus from a distance, using a ridge of rough ice to itself until it was close enough to charge the walrus as it lay by its haulout hole at the edge of a frozen- in multiyear floe. There was blood sprayed on the snow at 3 separate breathing holes around the edge ofthe floe in a pattern that probably resulted from the blood being mixed with expired air from the nostrils. We suspect the bear had time to hit the walrus on the head with a paw, or bite it on the face or nose, before the walrus escaped into the water. The bear's tracks went to all 3 holes, suggesting that it tried unsuccessfully to capture the walrus for some time after the initial attempt, possibly because the wounded animal kept resurfacing at different holes to breathe. We also found unusual amounts of blood that appeared to be from wounding attacks at breathing holes at sites 5 and 9, but it was difficult to interpret what had happened because most of the tracks were covered by drifted snow.
In spring 1976, T. Eley (Alas. Dep. Fish and Game, Fairbanks, unpubl. data) tracked polar bears as part of a study on polar bear predation. He recorded 1 kill of young yearling walrus by a polar bear at Cape Lisburne, Alaska. On 13 June 1987, about 60 km northeast of Point Barrow, Alaska, K. Frost (pers. commun.) observed a adult large male polar bear dragging a medium-sized male walrus, with approximately 25-cm tusks, out ofthe water at the edge of a floe. The walrus was bleeding It had profusely, indicating it had just been killed. apparently been alone at the edge of a floe in an area of broken ice, and was farther east than walruses normally occur in that region.
That's one gutsy guard dog! Canines chase starving polar bear away from Siberian weather station By RICHARD HARTLEY-PARKINSON UPDATED: 11:21 EST, 25 November 2011 Comments (125) Share
When you live at one of the most isolated corners of the planet, a dog really is man's best friend. And when a hungry polar bear lumbered ashore to forage for food among the rubbish bins at a weather station, the dogs of Bely Island off the tip of the Yamal Peninsula in Siberia risked their lives to prove their worth. Without fear of their giant adversary, who could have killed them with a single swipe if it wanted to, they charged forward to protect the few human inhabitants of the remote spot from the powerful beast. First one, then two, and finally a third dog joined the fray, barking and growling at the polar bear. Although the polar bear did not exactly beat a hasty retreat, it came no further inland after encountering the hostile 'welcoming' committee and shuffled off elsewhere.
Get off my land: One of the dogs approaches the polar bear at Bely Island weather station after he came ashore on one of the most remote islands in the world
Two's company: A second dog joins in the foray making the polar bear edge backwards as they carry on barking at the unwelcome visitor
Three's a crowd: Amateur photographer Sergey Anisimov captured the exchange as a third dog decided it wanted in on the action The weather station at Bely Island has been there since 1934. The four workers at the station send weather information to Moscow every three hours and polar bears are fairly frequent visitors.
More... Saving the eye of the tiger: Battle to prevent rare white big cat from going blind Back from the brink of death: The recovery of starved Reuben... the thinnest dog the RSPCA staff had ever seen Foxy Roxy makes herself top dog as she moves in with family who rescued her No that's a real DRY ski slope: No snow in Sweden where start of winter has been delayed by a month The man who took these remarkable photographs, Sergey Anisimov, 50, was invited to the weather station by the Government of Yamalo-Nenets Autonomous Okrug, whose officials were travelling there to examine a newly built trading station for deer-breeders. On the island is a memorial stone there dedicated to soldiers and sailors killed during World War Two. There is a Northern Sea Route close to the island and during the war bodies of sailors from sunken ships would wash up on the shore and then be buried inland. Several Russian Orthodox Priests had also travelled to the island to consecrate the memorial stone. Mr Anisimov said: 'We flew to the station by helicopter. And we noticed a bear when we flew closer to the station. 'The bear was digging into boxes of old things, probably rubbish, looking for some food. When we got out of the helicopter we noticed that the bear came closer until it was only about thirty metres from us.
Sorry: The hungry bear looks almost apologetic as it slinks away from the pack of dogs before heading back down to the sea
Sore paw: The bear looks fed up in in front of the bleak scenery after its confrontation with the dogs that were guarding the few inhabitants of Bely Island 'The dogs tried to protect us and we fired a signal pistol to try and scare it away. Eventually it gave up its advance and just lay down. There were also weather station workers near us and ready with the guns to scare the bear away. 'When we flew away the bear was still there and was watching us with sad eyes.' Bely Island is a relatively large island in the Kara Sea off the tip of the Yamal Peninsula, Siberia, Russia. It covers an area of 1,810 square kilometres. It is covered tundra but some dwarf shrubs also grow on the island. It is separated from the mainland by the Malygina Strait, an eight to ten kilometre wide sound which is frozen most of the year. The island belongs to the Yamalo-Nenets Autonomous Okrug which is the northern part of the Tyumen Oblast administrative division of Russia.
Jennifer Welsh, LiveScience Staff Writer Date: 19 April 2012 Time: 02:00 PM ET
A large male polar bear returns to feed on a fin whale carcass. On land, where bears cannot hunt for seals, food is scarce and polar bears mainly depend on washed up marine mammals for food. Holmiabukta Bay, Northwestern Svalbard, Norway.
Polar bears have been chilling on the ice far longer than is generally thought, new research suggests, and they probably interbred with brown bears at one point after the two species separated.
The new German study contradicts data from a study published last July in the journal Current Biology that suggested polar bears separated from brown bears 150,000 years ago. The new study analyzed the bears' mitochondrial DNA, a special "additional genome" that lives in the cell's energy factories and is passed down only from the mother. The new study concludes that the bears became separate species closer to 600,000 years ago.
If the polar bears were only 150,000 years old, as suggested by the previous study, they would have had to evolve many specialized traits in a curiously brief time, the German researchers said.
"I've been long puzzled by the suggestion that the polar bears would have been such a miraculous and rapidly evolving species," Frank Hailer of the Senckenberg Nature Research Society in Frankfurt told LiveScience. "I had this lingering question: Is it really true?"
A polar bear mother and her cubs of the year rest on one of the few remaining piece of drift ice in the Barents Sea in late July, Northeastern Svalbard, Northern Europe.
Nuclear problem solver Hailer and his colleagues looked at the polar bear's nuclear DNA, which comes from both parents and is much larger than the mitochondrial genome.
They compared 9,000 base-pair sequences (the chemicals that make up the "rungs" of DNA's ladderlike molecule) from the nuclear DNA of 45 polar, brown and black bears. This comparison let the researchers build a family tree, with the idea that the greater the genetic differences between the species, the farther they were apart in evolutionary time. They were able to estimate when the polar bears and brown bears separated.
"We found that polar bears are much older than we previously knew from other studies; their appearance dated to about 600,000 years ago," Hailer said. "That would make sense around that time for something like a polar bear to evolve, because Arctic habitats were much larger than they are today, so there would have been much larger habitats that would have been suitable for a species like a polar bear."
Female polar bear with her cub on a frozen lake near Cape Churchill, Canada.
Adapting to environment The researchers say the mitochondrial DNA data could have come from a hybridization event between polar and brown bears 150,000 years ago during the last warm interglacial period. During that time, sea ice melted and polar bears took to the shores, where they came into contact with brown bears.
The researchers say this hybridization (similar to the hybrid "grolar" or "pizzly" bears seen in recent years in Canada) would have introduced the brown bear mitochondrial DNA into the polar bear population. If the DNA from the brown bears helped the polar bears survive the warm period, it's possible it could have easily spread throughout the population.
It seems "the polar bear population at the time they hybridized with brown bears was very small," Hailer said. "The impact of hybridization was very large, so the piece of mitochondrial DNA that came from brown bears to polar bears replaced all the original polar bear mitochondrial DNA."
This study appears in the April 20 issue of the journal Science.
Ancient Warming May Have Reunited Polar and Brown Bears, for a Bit
Wynne Parry, LiveScience Senior Writer Date: 23 July 2012 Time: 03:01 PM ET
A new genomic study estimates polar bears split from other bears as much as five million years ago.
Polar bears' past may echo their future, indicates a genetic study that finds the white-furred, sea ice-dwelling bears interbred with brown bears long after the two species separated as much as 5 million years ago.
Climate change likely drove this mixing among bears, writes the research team, noting there is evidence this is happening again.
"Maybe we're seeing a hint that in really warm times, polar bears changed their lifestyle and came into contact, and indeed interbred, with brown bears," said study researcher Stephan Schuster, a professor of biochemistry and molecular biology at Pennsylvania State University, and a research scientist at Nanyang Technological University in Singapore, in a statement.
The study estimates polar bears split from brown bears between 4 million and 5 million years ago, after which they endured fluctuations in climate, including ice ages and warmer times.
Polar bears are currently facing the effects of climate change, this time caused by humans, as the Arctic sea ice upon which they live recedes to unprecedented levels.
A comparison of the complete genetic blueprints from polar, brown and black bears estimated they diverged roughly 4 to 5 million years ago. (ABC brown bears are a genetically isolated population in Alaska.)
"If this trend continues, it is possible that future [polar bears] throughout most of their range may be forced to spend increasingly more time on land, perhaps even during the breeding season, and therefore come into contact with brown bears more frequently," the researchers write in results published today (July 23) in the journal Proceedings of the National Academy of Sciences.
"Recently, wild hybrids and even second-generation offspring have been documented in the Northern Beaufort Sea of Arctic Canada where the ranges of brown bears and [polar bears] appear to overlap, perhaps as a recent response to climatic changes," they write.
Schuster and colleagues sequenced genomes (the complete genetic blueprint) of three brown bears and a black bear and compared them with the genomes of polar bears, one modern and the other obtained from remains from a 120,000-year-old polar bear.
Based on differences they found in the bears' genetic codes, the team estimated polar and brown bears split apart about the same time black bears became a distinct species After the split between polar and brown bears, the two species remained isolated for some time, allowing genetic changes to accumulate, before interbreeding more recently, their analysis indicates.
This complicated history may explain why other research has estimated a much younger age for polar bears, the researchers write.
A study published earlier this year estimated polar bears evolved 600,000 years ago, contradicting a previous estimate of 150,000 years ago.
Polar Bear Dies After Catching 'Zebra Herpes' At German Zoo
Huffington Post A Polar Bear has died after catching a strain of zebra herpes at a zoo in Germany.
Female polar bear, Jerka, was the first to die at the Zoological Gardens in Wuppertal, suffering seizures and frothing at the mouth after her brain swelled (encephalitis). Her male mate Lars, who was also infected, was saved by vets.
Leibniz-Institute for Zoo and Wildlife Research (IZW) in Berlin extracted DNA from the brain of the dead bear showing that the virus was a form of equine herpes.
Zoo keepers were perplexed as to how the animals contracted the mystery virus, especially as the zebra house is 68 metres from the bear enclosure.
he zebra house is 68 metres away and the zookeepers that work with the animals do not work with the polar bears
Scientists have warned that the equine herpes virus may have developed the ability to jump species in the same way as flu.
Influenza can spread from pigs to birds to humans and is a very unstable virus. There are fears that this virus could be the same.
It is unclear how the mutated herpes virus was transported, as zoo keepers that work with zebras don’t work with bears. Scientists speculated that perhaps mice and rats could have carried the virus to the enclosure, but more research is necessary, Prof Klaus Osterrieder from the Free University Berlin told the BBC.
However emergence of a species-jumping virus could have a significant effect on zoos’ ability to preserve endangered species.
The close proximity of animals which would never be found together in the wild may have indirectly affected the spread of this illness. The report, published in Current Biology,writes that zoos may provide a breeding ground for such species jumping and called for zoo keepers to be vigilant.
"Zoos unintentionally provide pathogens with a high diversity of species from different continents and habitats assembled within a confined space.
"Institutions alert to the problem of pathogen spread to unexpected hosts can monitor the emergence of pathogens and take preventative measures." Full story
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