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| Polar Bear - Ursus maritimus | |
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| Tweet Topic Started: Jan 7 2012, 07:57 PM (26,212 Views) | |
| maker | Jan 7 2015, 05:50 PM Post #31 |
Apex Predator
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http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0112021 http://www.usgs.gov/newsroom/article.asp?ID=4093#.VK3q4jTF-YE Edited by maker, Jan 7 2015, 06:02 PM.
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| Taipan | Apr 2 2015, 01:35 PM Post #32 |
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Polar bears unlikely to thrive on land-based foods Date: April 1, 2015 Source: United States Geological Survey Summary: Polar bears, increasingly forced on shore due to sea ice loss, may be eating terrestrial foods including berries, birds and eggs, but any nutritional gains are limited to a few individuals and likely cannot compensate for lost opportunities to consume their traditional, lipid-rich prey -- ice seals.  Polar bear laying down to dry after a swim in the Chukchi sea. A team of scientists led by the U.S. Geological Survey found that polar bears, increasingly forced on shore due to sea ice loss, may be eating terrestrial foods including berries, birds and eggs, but any nutritional gains are limited to a few individuals and likely cannot compensate for lost opportunities to consume their traditional, lipid-rich prey -- ice seals. "Although some polar bears may eat terrestrial foods, there is no evidence the behavior is widespread," said Dr. Karyn Rode, lead author of the study and scientist with the USGS. "In the regions where terrestrial feeding by polar bears has been documented, polar bear body condition and survival rates have declined." The authors detail their findings in a review article in Frontiers in Ecology and the Environment. The scientists noted that over much of the polar bear's range, terrestrial habitats are already occupied by grizzly bears. Those grizzly bears occur at low densities and are some of the smallest of their species due to low food quality and availability. Further, they are a potential competitor as polar bears displaced from their sea ice habitats increasingly use the same land habitats as grizzly bears. "The smaller size and low population density of grizzly bears in the Arctic provides a clear indication of the nutritional limitations of onshore habitats for supporting large bodied polar bears in meaningful numbers," said Rode. "Grizzly bears and polar bears are likely to increasingly interact and potentially compete for terrestrial resources." The study found that fewer than 30 individual polar bears have been observed consuming bird eggs from any one population, which typically range from 900 to 2000 individuals. "There has been a fair bit of publicity about polar bears consuming bird eggs. However, this behavior is not yet common, and is unlikely to have population-level impacts on trends in body condition and survival," said Rode. Few foods are as energetically dense as marine prey. Studies suggest that polar bears consume the highest lipid diet of any species, which provides all essential nutrients and is ideal for maximizing fat deposition and minimizing energetic requirements. Potential foods found in the terrestrial environment are dominated by high-protein, low-fat animals and vegetation. Polar bears are not physiologically suited to digest plants, and it would be difficult for them to ingest the volumes that would be required to support their large body size. "The reports of terrestrial feeding by polar bears provide important insights into the ecology of bears on land," said Rode. "In this paper, we tried to put those observations into a broader context. Focused research will help us determine whether terrestrial foods could contribute to polar bear nutrition despite the physiological and nutritional limitations and the low availability of most terrestrial food resources. However, the evidence thus far suggests that increased consumption of terrestrial foods by polar bears is unlikely to offset declines in body condition and survival resulting from sea ice loss." http://www.sciencedaily.com/releases/2015/04/150401133025.htm Journal Reference: Karyn D Rode, Charles T Robbins, Lynne Nelson, Steven C Amstrup. Can polar bears use terrestrial foods to offset lost ice-based hunting opportunities? Frontiers in Ecology and the Environment, 2015; 13 (3): 138 DOI: 10.1890/140202 Increased land use by polar bears (Ursus maritimus) due to climate-change-induced reduction of their sea-ice habitat illustrates the impact of climate change on species distributions and the difficulty of conserving a large, highly specialized carnivore in the face of this global threat. Some authors have suggested that terrestrial food consumption by polar bears will help them withstand sea-ice loss as they are forced to spend increasing amounts of time on land. Here, we evaluate the nutritional needs of polar bears as well as the physiological and environmental constraints that shape their use of terrestrial ecosystems. Only small numbers of polar bears have been documented consuming terrestrial foods even in modest quantities. Over much of the polar bear's range, limited terrestrial food availability supports only low densities of much smaller, resident brown bears (Ursus arctos), which use low-quality resources more efficiently and may compete with polar bears in these areas. Where consumption of terrestrial foods has been documented, polar bear body condition and survival rates have declined even as land use has increased. Thus far, observed consumption of terrestrial food by polar bears has been insufficient to offset lost ice-based hunting opportunities but can have ecological consequences for other species. Warming-induced loss of sea ice remains the primary threat faced by polar bears. Read More: http://www.esajournals.org/doi/10.1890/140202 Edited by Taipan, Oct 2 2017, 02:51 PM.
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| Taipan | Jul 17 2015, 01:23 PM Post #33 |
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Polar bears threatened: Experience limited energy savings in summer Date: July 16, 2015 Source: University of Wyoming Summary: Some earlier research suggested that polar bears could, at least partially, compensate for longer summer food deprivation by entering a state of lowered activity and reduced metabolic rate similar to winter hibernation -- a so-called 'walking hibernation.' But new research shows that the summer activity and body temperature of bears on shore and on ice were typical of fasting, non-hibernating mammals, with little indication of 'walking hibernation.'  A young polar bear stands on pack ice over deep waters in the Arctic Ocean in October 2009, during a major research project headed by the University of Wyoming. Polar bears are unlikely to physiologically compensate for extended food deprivation associated with the ongoing loss of sea ice, according to one-of-its-kind research conducted by University of Wyoming scientists and others, and published today in the journal Science. "We found that polar bears appear unable to meaningfully prolong their reliance on stored energy, confirming their vulnerability to lost hunting opportunities on the sea ice -- even as they surprised us by also exhibiting an unusual ability to minimize heat loss while swimming in Arctic waters," says John Whiteman, the UW doctoral student who led the project. The loss of sea ice in the Arctic, which is outpacing predictions, has raised concern about the future of polar bears, leading to their listing as a globally threatened species under the U.S. Endangered Species Act in 2008. The bears depend on hunting seals on the surface of the sea ice over the continental shelf, most successfully from April to July. In parts of the polar bears' range, the lengthening period of sea ice retreat from shelf waters -- caused by increasing temperatures -- can reduce their opportunities to hunt seals, leading to declines in bear nutritional condition. Some earlier research suggested that polar bears could, at least partially, compensate for longer summer food deprivation by entering a state of lowered activity and reduced metabolic rate similar to winter hibernation -- a so-called "walking hibernation." But the new research shows that the summer activity and body temperature of bears on shore and on ice were typical of fasting, non-hibernating mammals, with little indication of "walking hibernation." Whiteman and his colleagues concluded in the Science publication: "This suggests that bears are unlikely to avoid deleterious declines in body condition, and ultimately survival, that are expected with continued ice loss and lengthening of the ice-melt period." The researchers reached that conclusion by capturing more than two dozen polar bears, implanting temperature loggers and tracking their subsequent movements on shore and on ice in the Arctic Ocean's Beaufort Sea, north of Alaska and Canada, during 2008-2010. The unprecedented effort, logistically supported by the U.S. Geological Survey (USGS) and funded by the National Science Foundation, USGS, U.S. Fish and Wildlife Service (USFWS), as well as the Environmental Protection Agency, required the assistance of numerous personnel, multiple helicopters and deployment of the U.S. Coast Guard ice-breaker, the Polar Sea. "Many colleagues -- even some on our research team -- doubted whether the study was possible, until we actually did it," says Merav Ben-David, the UW professor who developed the research plan along with Professor Hank Harlow, an eco-physiologist and colleague in the Department of Zoology and Physiology, and Steve Amstrup, previously with the USGS and currently the chief scientist at Polar Bears International. "This project was logistically so intense that it may never be replicated." At the same time, the scientists found that polar bears use an unusual physiological response to avoid unsustainable heat loss while swimming in the cold Arctic waters. To maintain an interior body temperature that allows them to survive longer and nowadays more frequent swims, the bears temporarily cool the outermost tissues of their core to form an insulating shell -- a phenomenon called regional heterothermy. "This regional heterothermy may represent an adaption to long-distance swims, although its limits remain unknown," wrote the scientists, who in an earlier publication -- in the journal Polar Biology -- noted that one of the bears in the study survived a nine-day, 400-mile swim from shore to ice. When recaptured seven weeks later, the bear had lost 22 percent of her body mass, as well as her cub. By shedding light on potential mechanisms that facilitated that bear's survival during her long swim, as well as the overall metabolism and activity of bears, the current study "profoundly contributes to understanding the value of summer habitats used by polar bears in terms of their energetics," Harlow says. Amstrup adds, "It fills a gap in our otherwise extensive knowledge of polar bear ecology and corroborates previous findings that the key to polar bear conservation is arresting the decline of their sea ice habitat." In addition to Whiteman, Ben-David, Harlow and Amstrup, co-authors of the Science paper are Research Zoologist George Durner of the USGS Alaska Science Center and Wildlife Biologist Eric Regehr of the USFWS Marine Mammals Management in Alaska, both previously Ph.D. students at UW, who also participated in project development and execution; and Professor Richard Anderson-Sprecher of UW's Department of Statistics and Research Scientist Shannon Albeke of UW's Wyoming Geographic Information Science Center, who contributed to data analyses. Additional support for the project was provided by the UW Program in Ecology and Wyoming NASA Space Grant Consortium. Consultation with key Inuit communities in Alaska and Canada ensured the successful completion of the study. Story Source: University of Wyoming. "Polar bears threatened: Experience limited energy savings in summer." ScienceDaily. www.sciencedaily.com/releases/2015/07/150716160322.htm (accessed July 16, 2015). Journal Reference: J. P. Whiteman, H. J. Harlow, G. M. Durner, R. Anderson-Sprecher, S. E. Albeke, E. V. Regehr, S. C. Amstrup, M. Ben-David. Summer declines in activity and body temperature offer polar bears limited energy savings. Science, 2015; 349 (6245): 295 DOI: 10.1126/science.aaa8623 ABSTRACT Polar bears (Ursus maritimus) summer on the sea ice or, where it melts, on shore. Although the physiology of “ice” bears in summer is unknown, “shore” bears purportedly minimize energy losses by entering a hibernation-like state when deprived of food. Such a strategy could partially compensate for the loss of on-ice foraging opportunities caused by climate change. However, here we report gradual, moderate declines in activity and body temperature of both shore and ice bears in summer, resembling energy expenditures typical of fasting, nonhibernating mammals. Also, we found that to avoid unsustainable heat loss while swimming, bears employed unusual heterothermy of the body core. Thus, although well adapted to seasonal ice melt, polar bears appear susceptible to deleterious declines in body condition during the lengthening period of summer food deprivation. http://www.sciencemag.org/content/349/6245/295 |
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| Taipan | Jul 29 2015, 02:56 PM Post #34 |
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Polar Bear Awes with Record-Breaking Dive by Elizabeth Palermo, Associate Editor | July 28, 2015 11:21am ET  This thin polar bear recently impressed researchers with his excellent diving skills. Polar bears are known to be excellent swimmers, but new research suggests that they are also superb divers. Scientists recently observed a polar bear dive that lasted 3 minutes, 10 seconds, shattering the previous known record by about 2 minutes. The researchers — Ian Stirling from the University of Alberta in Canada, and Rinie van Meurs, a naturalist and polar expedition leader from the Netherlands — were studying polar bears in the Norwegian archipelago of Svalbard (located between continental Norway and the North Pole, east of Greenland), when they witnessed this epic underwater swim. The researchers described the dive in the August edition of the journal Polar Biology. Polar bears are known to dive for food, said Stirling and van Meurs, who noted in their report that these animals typically stay submerged for anywhere between 3 and 30 seconds when diving. Sometimes, they'll stay submerged longer to look for kelp, but the longest recorded kelp dive lasted only about 1 minute, 12 seconds, they said. This record-breaking dive was also for food, but this bear had bigger prey in mind. The emaciated polar bear, which the researchers observed from the deck of a ship, was hunting a group of three bearded seals that were lounging about on a sheet of floating ice, called an ice floe. The bear slipped into the water and started swimming toward the seals before diving below the surface to continue what the researchers called his "aquatic stalk." After spending more than 3 minutes underwater, the polar bear "exploded" out of the water and propelled itself halfway onto the ice floe, right in front of where one of the seals was resting. Unfortunately for the hungry bear, the seal got away, the researchers said. But the entire hunt was recorded on video and on film, allowing the researchers to confirm that the polar bear had not come up for air before lunging onto the ice. To put the bear's dive into perspective, the average human being can hold his or her breath for about 2 minutes underwater, though even that is a stretch for some folks. And some people can train themselves to hold their breath for much longer than that. (There are various techniques for increasing the time between breaths.) The polar bear's ability to hold its breath for so long is interesting to the researchers because it could be a sign that these animals are evolving to survive in a habitat that is rapidly changing. Global warming is leading to a dearth of sea ice, the researchers said, meaning polar bears have less ice on which to hunt. As such, the animals must spend more time in the water than they did previously when hunting for seals and other terrestrial prey. "It is possible that the ability to hold its breath for so long may indicate the initial development of a significant adaptation for living and hunting in its marine environment," the researchers wrote in the study. Polar bears diverged from their ancestors, brown bears (Ursus arctos), between 400,000 and 500,000 years ago, which is quite recent in evolutionary terms. The polar bear's propensity for underwater breath holding may be a trait that still hasn't fully evolved, but it's unlikely that the animal can evolve fast enough to adapt to life at the quickly shrinking polar ice caps, Stirling and van Meurs said. http://www.livescience.com/51675-record-breaking-polar-bear-dive.html Longest recorded underwater dive by a polar bear Ian Stirling, Rinie van Meurs Polar Biology August 2015, Volume 38, Issue 8, pp 1301-1304 Date: 25 Mar 2015 Abstract The maximum dive duration for a wild polar bear (Ursus maritimus) of any age is unknown, and opportunities to document long dives by undisturbed bears are rare. We describe the longest dive reported to date, by a wild undisturbed adult male polar bear. This dive was made during an aquatic stalk of three bearded seals (Erignathus barbatus) lying several meters from each other at the edge of an annual ice floe. The bear dove for a total duration of 3 min 10 s and swam 45–50 m without surfacing to breathe or to reorient itself to the locations of the seals. The duration of this dive may be approaching its maximum capability. Polar bears diverged from brown bears (Ursus arctos) about 4–500,000 years ago, which is recent in evolutionary terms. Thus, it is possible that the ability to hold its breath for so long may indicate the initial development of a significant adaptation for living and hunting in its marine environment. However, increased diving ability cannot evolve rapidly enough to compensate for the increasing difficulty of hunting seals because of the rapidly declining availability of sea ice during the open-water period resulting from climate warming. http://link.springer.com/article/10.1007/s00300-015-1684-1 Edited by Taipan, Oct 2 2017, 02:53 PM.
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| Ntwadumela | Nov 10 2015, 11:10 AM Post #35 |
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 Observations of intraspecific predation by polar bears in the southern Beaufort Sea Intraspecific killing has been reported among polar bears (Ursus maritimus), brown bears (U. arctos), and black bears (U. americanus). Although cannibalism is one motivation for such killings, the ecological factors mediating such events are poorly understood. Between 24 January and 10 April 2004, we confirmed three instances of intraspecific predation and cannibalism in the Beaufort Sea. One of these, the first of this type ever reported for polar bears, was a parturient female killed at her maternal den. The predatory bear was hunting in a known maternal denning area and apparently discovered the den by scent. A second predation event involved an adult female and cub recently emerged from their den, and the third involved a yearling male. During 24 years of research on polar bears in the southern Beaufort Sea region of northern Alaska and 34 years in northwestern Canada, we have not seen other incidents of polar bears stalking, killing, and eating other polar bears. We hypothesize that nutritional stresses related to the longer ice-free seasons that have occurred in the Beaufort Sea in recent years may have led to the cannibalism incidents we observed in 2004. Amstrup, S. C., I. Stirling, T. S. Smith, C. Perham, and G. W. Thieman. 2006. Recent observations of intraspecific predation and cannibalism among polar bears in the southern Beaufort Sea. Polar Biology, 29:997-1002. Source: http://alaska.usgs.gov/science/biology/polar_bears/unusual_mortality.html |
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| Taipan | Feb 24 2016, 09:39 PM Post #36 |
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Exclusive Video: Polar Bear Cannibalizes Cub A National Geographic expedition filmed the rarely seen behavior, which climate change may be making much more common. EXCLUSIVE: Male Polar Bear Chases and Eats Cub Polar bear cannibalism likely isn't a rare event, but it's rarely witnessed by people. This may be the first time it's been captured so well on video. By Michael Greshko PUBLISHED TUE FEB 23 07:00:11 EST 2016 A new video has captured a gruesome and little seen side to polar bears: When times are tough, males cannibalize cubs. The phenomenon, long known to the Arctic’s native peoples, has been studied since the 1980s. Scientists believe that polar bears eat cubs in the late summer and autumn, when seals, their typical prey, are at sea and less available. “One of the only things that’s left to eat is, in fact, cubs of various ages,” says Ian Stirling, a biologist at the University of Alberta and Environment Canada. “The footage itself is quite rare, but the event probably isn’t.” The raw video, shot in the summer of 2015 off Canada's Baffin Island (map) during a Lindblad Expeditions trip on the National Geographic Explorer, mirrors other scientists’ accounts of polar bear cannibalism. The slow-moving cub and the smaller female are no match for the large, fast male, which swiftly goes in for the kill, repeatedly biting the cub around the head and neck. After briefly trying to rescue her doomed cub, the female hastily retreats, wary of becoming the male’s next meal. Polar Bear Mom & Cubs When they're not playing, polar bear cubs learn under the watchful eye of their mother. “It was really hard to look away,” says naturalist Jennifer Kingsley, who witnessed the event from aboard the National Geographic Explorer ship. “Sure, you understand that this is life in the Arctic, and this is something we know about polar bear biology. But to see it is really dramatic.” Driven to Desperation Cannibalism is common in nature, occurring in hippopotamuses, tiger salamanders, sloth bears, and various other species. The male polar bear's cannibalistic turn is par for the course. Males are twice the size of females and are generally more aggressive, making it "a much smaller step [for males] to turn cannibalistic when hungry," says Stirling. Females, on the other hand, tend to avoid fights, despite the fact that nursing cubs means they're more starved than males. But climate change may be making the behavior more prevalent, Stirling says. Arctic sea ice has been continually shrinking over time; in 2015, scientists measured the lowest maximum extent of sea ice in three decades. As the ice disappears, so do the crucial platforms that polar bears use to hunt seals, Stirling says. (Also see "4 Ways Polar Bears Are Dealing With Climate Change.") Without the ability to hunt seals, polar bears may be driven to ever more extreme cannibalism, if they’re not already. In 2004, for instance, biologists working in Alaska’s Beaufort Sea (map) witnessed an adult male track a pregnant female to her den and eat her—a never-before-seen act perhaps motivated by climate-driven desperation. http://news.nationalgeographic.com/2016/02/160223-polar-bears-arctic-cannibals-animals-science/ |
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| Mammuthus | May 21 2017, 02:59 AM Post #37 |
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Polar bears shift from seals to bird eggs as Arctic ice melts By Thom Hoffman Polar bears are ditching seafood in favour of scrambled eggs, as the heat rises in the Arctic melting the sea ice. A changing coastline has made it harder for the predators to catch the seals they favour and is pushing them towards poaching goose eggs. This is according to a team led by Charmain Hamilton of the Norwegian Polar Institute that monitored the movements of local polar bears and seals before and after a sudden decline in sea ice in 2006, which altered coastal areas in the Norwegian archipelago of Svalbard. The researchers attached tracking devices to 60 ringed seals and 67 polar bears overall, which allowed them to compare their movements before and after the ice collapse. Before the melt, when they were hunting on stable sea ice, the polar bears had a big advantage over their favoured prey. “Both sexes of all age classes successfully hunt seals by stalking or ‘still hunting’,” says Hamilton. However, on a melting coastline punctuated by broken-up icebergs, the odds become stacked in the seal’s favour. In deep water The polar bears must now swim undetected towards the seals before launching themselves out of the water to grab their prey on the floating chunks of ice. Not all bears have mastered this explosive technique and there is a high failure rate even among those that have. “It seems that currently, it is mainly large, male bears using this aquatic hunting method on Svalbard,” says Hamilton. “It is likely [to be] more energetically demanding than the traditional hunting methods.”  In response, the bears are retreating from the coast. The tracking devices show them wandering greater distances in search of alternative land-based food. The bears also spend a lot more time near bird nesting grounds, which suggests eggs have become a significant food source. But they would need an immense omelette to replace a seal breakfast and this type of mass egg hunting can devastate nesting bird populations. Ecologist Jouke Prop at the University of Groningen, Netherlands, is also studying geese in the Arctic. He has filmed bears devouring goose eggs at nesting sites. Smash and grab “It takes on average 30 seconds to locate a nest and 60 seconds to eat the eggs,” he says. Previous research found that affected bird populations can slump by up to 90 per cent. “It is extremely intriguing how the habit of bird egg eating is developing within the polar bear population,” says Prop. “Which bears are eating eggs? Did they learn from their mothers?” “I have seen the diarrhoea faeces of bears eating eggs,” says Maarten Loonen at the University of Groningen. “I think eggs are not their best favourite food. Too much protein. Nevertheless, they have to eat something and they probably can survive on it.” The bears seem to be getting enough nutrition to survive, but Hamilton wonders what the long-term effects of this change in diet will be. “Seal fat is an extraordinarily rich source of lipids that will be very hard to replace,” she says. As the bears move on to eating bird eggs for sustenance, what will happen to the geese population in the future? “If numbers decline – which is to be expected – this will have an impact on the whole terrestrial ecosystem,” says Prop. “For example, Arctic foxes depend on young geese as food; reindeer food intake is facilitated by geese grazing the tundra.” Despite the uncertainty, one thing is clear: the cubs and eggs of the new generation will have to adapt quickly to survive the next phase of Arctic environmental change. https://www.newscientist.com/article/2130821-polar-bears-shift-from-seals-to-bird-eggs-as-arctic-ice-melts/ Edited by Mammuthus, May 21 2017, 03:10 AM.
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| Taipan | Oct 2 2017, 03:05 PM Post #38 |
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Picnic Time! 230 Polar Bears Feast on Whale Carcass By Laura Geggel, Senior Writer | September 29, 2017 03:41pm ET  A convention of polar bears chowed down on this whale carcass off the coast of Wrangel Island, in Russia, on Sept. 19. Credit: Alexander Gruzdev/Wrangel Island State Nature Reserve Hundreds of hungry polar bears were treated to a whale of a buffet last week when the carnivores descended on a whale carcass on the coast of Russia's Wrangel Island. The incredible sight was photographed by tourists on a boating expedition that was traveling through the Northeast Passage. "We were cruising down the coast and saw a 'herd' or 'convention' of polar bears on/near the beach," on Sept. 19, Rodney Russ, the expedition leader, wrote on his blog. Russ is the owner and founder of Heritage Expeditions, the New Zealand-based company that co-led the trip. Russ immediately realized why the polar bears (Ursus maritimus) "of all ages, sexes and sizes" had congregated there: They were feasting on a dead bowhead whale (Balaena mysticetus), he wrote in the blog post. Russ counted more than 150 polar bears, although a statement issued by the Wrangel Island State Nature Reserve put that estimate at closer to 230 bears. Intrigued, the tour group left their boat, the Akademik Shokalskiy (the same vessel that got stuck in Antarctic sea ice in December 2013) and boarded smaller vessels known as zodiacs to get a closer look at the seemingly ravenous bears. "That is the memory we will all carry with us," Russ wrote. "There are no words to describe it." It's possible so many bears attended the impromptu picnic because they smelled the rotting whale. Polar bears can smell seals up to 20 miles (32 kilometers) away, according to the San Diego Zoo. When they're not eating beached whales, the bears are known to eat ringed seals, walrus, caribou, grass and seaweed, the San Diego Zoo says.  These polar bears got a whale of a meal. Credit: Alexander Gruzdev/Wrangel Island State Nature Reserve Polar bears are listed as vulnerable to extinction, largely because human-made climate change is melting the Arctic sea ice where they live, according to the International Union for Conservation of Nature (IUCN). It's unclear, however, whether climate change had made these particular bears hungrier than usual. The frequency of starving polar bears is expected to increase as the climate warms and sea ice declines — not just because of climate change directly, but because ice loss is taking away seals, their main food source, Steven Amstrup, chief scientist at Polar Bears International, a nonprofit research organization dedicated to studying polar bears, told Live Science in 2015. The bowhead whale is listed as an "animal of least concern," meaning it is not at risk, the IUCN says. This isn't the only bear-on-whale banquet in the books. In June 2016, a naturalist guide for a lodge in Alaska spotted a brown bear snacking on a sperm-whale carcass in the southeastern part of the state. If you want to glimpse a polar bear on your own, watch the polar bear cam at the San Diego Zoo — just know these bears won't be eating any whales. https://www.livescience.com/60569-polar-bears-feast-on-whale-carcass.html |
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| Taipan | Dec 9 2017, 02:12 PM Post #39 |
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Starving Polar Bear's Last Hours Captured in Heartbreaking Video By Stephanie Pappas, Live Science Contributor | December 8, 2017 07:12pm ET A hard-to-watch video from Canada's Baffin Islands shows an emaciated polar bear in what were likely the last few hours of its life. National Geographic photographer Paul Nicklen captured the sad sight on video and posted it online Dec. 5. The video shows the bear staggering toward a trash can and searching in vain for something to eat. It ends with the bear resting on the ground, exhausted. Nicklen told National Geographic he wants the footage of the dying bear to communicate the consequences of climate change. "When scientists say bears are going extinct, I want people to realize what it looks like. Bears are going to starve to death," Nicklen said. "This is what a starving bear looks like." Ice-bound hunters Polar bears depend on sea ice to hunt seals, which fuel the bears with their blubbery, energy-rich meat. As the climate warms, the Arctic has been particularly hard-hit. Arctic sea ice reaches its maximum extents in late winter, typically around March, and melts in the summer, hitting its minimums around September. In recent years, ice has been forming later, melting sooner and covering less area. Record or near-record lows in ice extent have become standard each March, when the Arctic should be at its most frosted-over.  Here, a polar bear stands on the island of Spitsbergen, part of the Svalbard archipelago, bordering the Arctic Ocean and the Norwegian and Greenland Seas. Credit: Prisma Bildagentur/UIG via Getty Images In March 2016, NASA scientist Walt Meier told Live Science that the Arctic has lost about half its volume at its maximum extents since record-keeping began. November 2017 saw an average sea-ice extent of 3.65 million square miles (9.46 million square kilometers), according to the National Snow and Ice Data Center, the third-lowest November extent on average since 1979. For polar bears, the loss of sea ice means the loss of hunting grounds. The International Union for Conservation of Nature lists the bears (Ursus maritimus) as "vulnerable," largely because of the loss of sea ice. Already, scientists have found that the loss of ice means polar bears must swim farther for food, a fact that puts cubs, in particular, at risk. Bears must also travel longer distances on foot over sea ice as the drift of the ice increases alongside melt, according to a 2017 study by the U.S. Geological Survey. Another study of bears fitted with tracking collars near Hudson Bay found that bears now spend more time on land, arriving earlier in the summer and leaving later in the fall, a pattern that means their seal-hunting season is limited. Though polar bears do shift their diet to snow goose eggs, caribou and other terrestrial meals when on land, a 2015 study published in the journal Frontiers in Ecology and the Environment found that the calories from these sources aren't enough to offset what the polar bears burn in foraging. Representative bear? Of course, there is no way to know whether any given bear would have starved without climate change, or what the history of the bear in the video is. Shrinking sea ice is causing polar bears to starve more often, but "[y]ou can't say that any one individual is starving because of climate change," Steven Amstrup, chief scientist at Polar Bears International, told Live Science in 2015 after a heart-wrenching photo of a skeletal polar bear circulated online. That's because polar bears do starve in the wild on a regular basis. As apex predators, they have no natural enemies to put them out of their misery when they become too old or injured to hunt, Amstrup explained. Nevertheless, Nicklen's video shows what this looks like for bears that have an increasingly hard time hanging on in warming conditions. He filmed the video with tears rolling down his cheeks, he told National Geographic. He's been asked why he didn't do something to help, he said, but it's illegal to feed wild polar bears in Canada, and there was little he could have done even if it weren't. "t's not like I walk around with a tranquilizer gun or 400 pounds of seal meat," Nicklen said. https://www.livescience.com/61151-starving-polar-bear-captured-on-video.html |
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| Taipan | Feb 3 2018, 07:51 PM Post #40 |
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Polar bears finding it harder to catch enough seals to meet energy demands Study reveals high metabolic rates, meaning polar bears need a lot of fat-rich prey, but more than half of those studied were running an energy deficit Date: February 1, 2018 Source: University of California - Santa Cruz  This is an adult female polar bear on the sea ice wearing a GPS satellite video-camera collar. GPS video-camera collars were applied to solitary adult female polar bears for 8 to 12 days in April, 2014-2016. These collars enabled researchers to understand the movements, behaviors, and foraging success of polar bears on the sea ice. Credit: Anthony Pagano, USGS A new study finds polar bears in the wild have higher metabolic rates than previously thought, and as climate change alters their environment a growing number of bears are unable to catch enough prey to meet their energy needs. The study, published February 2 in Science, reveals the physiological mechanisms behind observed declines in polar bear populations, said first author Anthony Pagano, a Ph.D. candidate at UC Santa Cruz. "We've been documenting declines in polar bear survival rates, body condition, and population numbers over the past decade," he said. "This study identifies the mechanisms that are driving those declines by looking at the actual energy needs of polar bears and how often they're able to catch seals." Pagano, who is also a wildlife biologist with the U.S. Geological Survey (USGS), conducted the study as part of his Ph.D. thesis research at UC Santa Cruz, where he has been working with coauthors Terrie Williams and Daniel Costa, both professors of ecology and evolutionary biology. The researchers monitored the behavior, hunting success, and metabolic rates of adult female polar bears without cubs as they hunted for prey on the sea ice of the Beaufort Sea in the spring. High-tech collars on the bears recorded video, locations, and activity levels over a period of eight to 11 days, while metabolic tracers enabled the team to determine how much energy the bears expended. The field metabolic rates they measured averaged more than 50 percent higher than previous studies had predicted. Five of the nine bears in the study lost body mass, meaning they weren't catching enough fat-rich marine mammal prey to meet their energy demands. "This was at the start of the period from April through July when polar bears catch most of their prey and put on most of the body fat they need to sustain them throughout the year," Pagano said. Climate change is having dramatic effects on the Arctic sea ice, forcing polar bears to move greater distances and making it harder for them to catch prey. In the Beaufort Sea, sea ice starts to retreat away from the continental shelf in July, and most of the bears move north on the ice as it retreats. As the Arctic warms and more sea ice melts, the bears are having to move much greater distances than previously. This causes them to expend more energy during the summer, when they are fasting until the ice returns to the continental shelf in the fall. In other areas, such as Hudson Bay, most bears move onto land when the sea ice retreats. There, Arctic warming means the sea ice is breaking up earlier in the summer and returning later in the fall, forcing bears to spend more time on land. "Either way, it's an issue of how much fat they can put on before the ice starts to break up, and then how much energy are they having to expend," Pagano said. Previous studies had tried to estimate polar bear metabolic rates and energy expenditures based on some assumptions about their behavior and physiology. For example, since polar bears are primarily "sit and wait" hunters, it was thought this would minimize their energy expenditure during hunting. Researchers also speculated that polar bears could lower their metabolic rate to save energy if they were not successful catching seals, Pagano said. "We found that polar bears actually have much higher energy demands than predicted. They need to be catching a lot of seals," he said. In the spring, polar bears are mostly preying on recently weaned ringed seals, which are more susceptible to being caught than adult seals. By the fall, the young seals are older and wiser, and polar bears are not able to catch as many. "It's thought that bears might catch a couple per month in the fall, compared to five to 10 per month in the spring and early summer," Pagano said. USGS researchers have been studying polar bears in the Beaufort Sea area since the 1980s. Their most recent population estimate indicates the polar bear population has declined by about 40 percent over the past decade. It has been difficult, however, for researchers to study the fundamental biology and behavior of polar bears in this very remote and harsh environment, Pagano said. "We now have the technology to learn how they are moving on the ice, their activity patterns, and their energy needs, so we can better understand the implications of these changes we are seeing in the sea ice," he said. In addition to Pagano, Williams, and Costa, the coauthors of the paper include USGS researchers George Durner, Karyn Rode, Todd Atwood, and Elizabeth Peacock; Stephen Atkinson of Dugald, Manitoba; and Megan Owen at the San Diego Zoo Institute for Conservation Research. This work was supported by the USGS Changing Arctic Ecosystems Initiative. Story Source: University of California - Santa Cruz. "Polar bears finding it harder to catch enough seals to meet energy demands: Study reveals high metabolic rates, meaning polar bears need a lot of fat-rich prey, but more than half of those studied were running an energy deficit." ScienceDaily. www.sciencedaily.com/releases/2018/02/180201173314.htm (accessed February 2, 2018). Journal Reference: A. M. Pagano, G. M. Durner, K. D. Rode, T. C. Atwood, S. N. Atkinson, E. Peacock, D. P. Costa, M. A. Owen, T. M. Williams. High-energy, high-fat lifestyle challenges an Arctic apex predator, the polar bear. Science, 2018; 359 (6375): 568 DOI: 10.1126/science.aan8677 Abstract Regional declines in polar bear (Ursus maritimus) populations have been attributed to changing sea ice conditions, but with limited information on the causative mechanisms. By simultaneously measuring field metabolic rates, daily activity patterns, body condition, and foraging success of polar bears moving on the spring sea ice, we found that high metabolic rates (1.6 times greater than previously assumed) coupled with low intake of fat-rich marine mammal prey resulted in an energy deficit for more than half of the bears examined. Activity and movement on the sea ice strongly influenced metabolic demands. Consequently, increases in mobility resulting from ongoing and forecasted declines in and fragmentation of sea ice are likely to increase energy demands and may be an important factor explaining observed declines in body condition and survival. http://science.sciencemag.org/content/359/6375/568 |
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| Flesh | May 30 2018, 05:19 PM Post #41 |
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Autotrophic Organism
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'They're everywhere': has the decline of the seal hunt saved the polar bear? Despite vanishing sea ice and shorter winters, Labrador’s polar bear population is among the healthiest in the world – and it could be thanks to the harp seals  There are over 2,500 polar bears in the coastal area that includes Labrador and northern Quebec, according to Environment Canada. Photograph: Danita Delimont/Getty Images/Gallo Images Guido Rich, 28, an Inuit hunter from Rigolet, Labrador, brings his Ski-Doo to a careful stop on the sea ice, mindful of the precious cargo it hauls: the body of an 800lb male polar bear. It takes Rich and two other men to roll the animal off the sled and on to the ice, while his wife and young children watch. His sister, Natasha Pottle, who shot the bear the night before, hands her brother the plastic bags used to store liver, hair and fat samples that will be sent away for lab testing. The animal will provide valuable information for Labrador’s biologists, a small windfall for his family and meat for the community. Rich has barely begun cutting into the hide when a parade of people from the village start arriving to take pictures, offer observations or just watch respectfully. “When you get a bear, everyone in town knows it,” Rich said. Scenes like this are being repeated up and down the rugged, remote coast this year. Despite vanishing sea ice and shorter, milder winters, Labrador’s polar bear population is actually growing – which means a bigger harvesting quota for Inuit hunters. There are more than 2,500 polar bears in the vast coastal area that includes Labrador and northern Quebec, according to Environment Canada – far more than was expected earlier in the millennium – and further signs the bears continue to rebound despite the impacts of climate change. Indeed, although scientists and Inuit sometimes clash over the estimates, the polar bear population of coastal Labrador is among the healthiest in the world. “When I grew up, a polar bear was kind of this mythical creature because you didn’t see them very often. You didn’t hear tell of people seeing them,” said Jim Goudie, wildlife manager for Nunatsiavut, the regional indigenous self-government. “This abundance of polar bears is not something my father’s generation grew up with. It’s only since the mid-80s there’s been the boom. Now there’s polar bears everywhere.” The reason, biologists suspect, is the boom in the harp seal population. As Newfoundland’s seal fishery has collapsed under international pressure, the harp seals of the north-west Atlantic have proliferated. They now number about 7.4 million animals – more then seven times the population in the 1970s. That has created a veritable feast for Labrador’s polar bears, who have shifted their diet from ring seals to their more southerly, promiscuous cousins. “They jumped on the harp seal boom,” Goudie said. “They appear to have adapted for this moment in time … We’re seeing them further south than in the past.” Labrador’s Inuit have hunted polar bears for thousands of years. But only recently have they been able to so carefully monitor and protect the population, thanks to a unique, indigenous-run conservation program managed by Nunatsiavut. The bear shot by Pottle was one of 12 killed by Inuit hunters this season under Nunatsiavut’s quota system, which doles out bear hunting licences through a lottery. A hunter has one week to get a bear before the licence expires and is transferred to another person. Only Inuit residents can apply for a licence, and it’s illegal to sell a licence to a big game hunter who is not from the region. In Inuit culture, a polar bear remains a deeply respected animal, called Nanuk in the Inuktitut language, and getting one is still considered the mark of a great hunter. The harvest remains such an important part of local tradition that it has its own statute in Nunatsiavut’s land claim with the federal government. But Pottle isn’t putting on any airs. Shooting her first polar bear was a terrifying experience, she said. “I was scared,” she said. “It was intense. We chased the tracks out on to the ice and there he was. Then our Ski-Doo stalled and he started coming toward us. That’s when I started calling for my brother.”  In Inuit culture, a polar bear remains a deeply respected animal, called Nanuk in the Inuktitut language, and getting one is considered the mark of a great hunter. Photograph: Image Broker / Rex Features Her brother, carrying the rifle on his back, circled around to keep the animal at a safer distance. Then he handed the gun to Natasha and told her to shoot. “She was crying, and I said: ‘What’s wrong?’ She said she’s never going polar bear hunting again,” he said. “I said: ‘It’s your licence. You’ve got to shoot it.’” The bear meat will be divided up and shared among the region’s community freezer program, which provides food for the elderly and others who can’t hunt for themselves. Wasting the meat is prohibited by Nunatsiavut law. Failure to share the meat or submit samples for testing means a hunter can be banned for five years. “Some people say it’s our right. But I’ve always viewed it as a privilege. We ask a lot of [hunters], but you’re getting something that not every Canadian has the right to go out and do,” said Goudie. “That’s why I think Nunatsiavut leads not only Canada, but also the world, when it comes to conservation management and buy-in to our system.” Inuit hunters can sell a bear pelt for $4,000 to $5,000 to a local taxidermist, who will auction it off to buyers around the world. In previous decades, when the international market for pelts was booming, the same bearskin could fetch as much as $30,000. Under Nunatsiavut’s program, a computer chip is embedded in the pelt to prove it was harvested through a legal hunt. Much like the coastal Inuit themselves, the polar bear’s world relies heavily on reliable, vast expanses of sea ice. As the region’s sea ice vanishes because of warming oceans and milder winters, the bear has had to adapt. The animals appear to be thriving, but winter is becoming increasingly unpredictable. The loss of sea ice has been dramatic, according to climatologist Robert Way. He points to the Canadian Ice Service historical database, which shows Nunatsiavut’s northern region has lost about a third of its ice cover in the past decade. Conservationists say the Nunatsiavut model is a lesson for other regions trying to manage their polar bear population. Goudie argues the Inuit, sometimes criticized by animal rights activists for allowing the bear hunt, have a vested interest in preserving the polar bears that live among them. “For Inuit, it would be like losing an entire piece of their culture,” he said. https://www.theguardian.com/world/2018/may/24/canada-polar-bears-labrador-rigolet-seal-hunt |
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| Taipan | Jun 20 2018, 09:04 PM Post #42 |
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Walking is more efficient than thought for threatened polar bears June 19, 2018, The Company of Biologists  Polar Bear (Ursus maritimus) near Kaktovik, Barter Island, Alaska. Credit: Alan Wilson/Wikipedia. A polar bear plunges into the icy Arctic waters in search of firmer ice; its world, which was once a sea of white, is melting beneath its paws. 'Research has documented declines in polar bear populations in some regions of the Arctic', says Anthony Pagano from the US Geological Survey, explaining that the bears now have to roam further on the receding ice to locate the seals upon which they dine. And, to make their predicament worse, measurements in the 1970s and 1980s suggested that polar bears consume more energy than other similarly sized animals because they have to generate heat to remain warm in the frigid environment and walk long distances to catch food. Knowing how much energy polar bears use just to remain alive is essential if we are to understand how the animals will survive in their dwindling environment, so Pagano and colleague Terrie Williams from the University of California, Santa Cruz, embarked on an ambitious programme of measuring how much energy polar and grizzly bears consume as they amble along. The scientists publish their discovery that polar bears and grizzly bears walk efficiently, consuming the same amount of energy while walking as other large animals, in Journal of Experimental Biology. 'Our conversations with zoos for this study started in 2012', says Pagano, recalling how he and Williams contacted Amy Cutting, Nicole Nicassio-Hiskey and Amy Hash at Oregon Zoo, Portland, USA, and Megan Owen, Tammy Batson and Nate Wagner at San Diego Zoo, USA, as both teams had trained polar bears to participate in husbandry procedures such as providing blood samples for health test. However, Pagano and Williams wanted to measure how much oxygen the 240kg animals consumed to calculate how much energy they were using while walking and the conventional method of placing a mask over the bear's muzzle would not work: 'Big carnivores do not like things on their faces', Williams explains. Instead, Charlie Robbins and Tony Carnahan from Washington State University, USA, built a custom-designed bear-proof metabolic chamber by installing a 3.6m long horse treadmill in a steel-framed chamber constructed from bullet-proof polycarbonate. The team then transported the 2000kg structure to the polar bears' respective locations, where Nicassio-Hiskey and Hash (Portland) and Batson, Owen and Wagner (San Diego) spent months patiently training the animals to walk on the treadmill. Recalling this period, Pagano says, 'Finding foods that the polar bears would be highly motivated to walk for was challenging'. However, the grizzly bears at Washington State University, USA, were more eager: 'They just bowled right in; they did not care if the treadmill moved fast or slow, all they cared about were the training treats', laughs Williams. Once the bears were comfortable with walking in the metabolic chamber, the team begin measuring the animals' oxygen consumption while filming and recording their movements. However, when they calculated the amount of energy consumed by the polar bears and grizzlies while sauntering at speeds of up to 4.6km/h, they were surprised that the two species consumed the same amount of energy (2.21kJ/kg m) and no more than similarly sized animals. The polar bears' walking metabolic rate was not intrinsically higher than that of other large mammals, but the team suspect that swimming could be more costly. And when they fitted GPS collars to six wild female polar bears on the Alaskan sea ice, it was clear that they were moving at similar speeds to the captive animals, ambling at around 3.4km/h and rarely breaking into a run, so their movements were as efficient. However, the news wasn't all good: simply standing up was more costly for both species than it is for other large animals, which could impact polar bears detrimentally as their survival teeters on thin ice. https://phys.org/news/2018-06-efficient-thought-threatened-polar.html Journal Reference: Pagano, A. M., Carnahan, A. M., Robbins, C. T., Owen, M. A., Batson, T., Wagner, N., Cutting, A., Nicassio-Hiskey, N., Hash, A. and Williams, T. M. (2018). Energetic costs of locomotion in bears: is plantigrade locomotion energetically economical? J. Exp. Biol. 221, DOI: 10.1242/jeb.175372 ABSTRACT Ursids are the largest mammals to retain a plantigrade posture. This primitive posture has been proposed to result in reduced locomotor speed and economy relative to digitigrade and unguligrade species, particularly at high speeds. Previous energetics research on polar bears (Ursus maritimus) found locomotor costs were more than double predictions for similarly sized quadrupedal mammals, which could be a result of their plantigrade posture or due to adaptations to their Arctic marine existence. To evaluate whether polar bears are representative of terrestrial ursids or distinctly uneconomical walkers, this study measured the mass-specific metabolism, overall dynamic body acceleration, and gait kinematics of polar bears and grizzly bears (Ursus arctos) trained to rest and walk on a treadmill. At routine walking speeds, we found polar bears and grizzly bears exhibited similar costs of locomotion and gait kinematics, but differing measures of overall dynamic body acceleration. Minimum cost of transport while walking in the two species (2.21 J kg−1 m−1) was comparable to predictions for similarly sized quadrupedal mammals, but these costs doubled (4.42 J kg−1 m−1) at speeds ≥5.4 km h−1. Similar to humans, another large plantigrade mammal, bears appear to exhibit a greater economy while moving at slow speeds. http://jeb.biologists.org/content/221/12/jeb175372 |
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