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Post by Gorilla king on Jul 10, 2021 9:26:22 GMT -5
Longest recorded underwater dive by a polar bear
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.
www.researchgate.net/publication/277573604_Longest_recorded_underwater_dive_by_a_polar_bear
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Post by tyrannosaurs on Jul 10, 2021 13:31:06 GMT -5
Polar bear population dynamics in the southern Beaufort Sea during a period of sea ice decline: In the southern Beaufort Sea of the United States and Canada, prior investigations have linked declines in summer sea ice to reduced physical condition, growth, and survival of polar bears (Ursus maritimus). Combined with projections of population decline due to continued climate warming and the ensuing loss of sea ice habitat, those findings contributed to the 2008 decision to list the species as threatened under the U.S. Endangered Species Act. Here, we used mark–recapture models to investigate the population dynamics of polar bears in the southern Beaufort Sea from 2001 to 2010, years during which the spatial and temporal extent of summer sea ice generally declined. Low survival from 2004 through 2006 led to a 25–50% decline in abundance. We hypothesize that low survival during this period resulted from (1) unfavorable ice conditions that limited access to prey during multiple seasons; and possibly, (2) low prey abundance. For reasons that are not clear, survival of adults and cubs began to improve in 2007 and abundance was comparatively stable from 2008 to 2010, with ;900 bears in 2010 (90% CI 606–1212). However, survival of subadult bears declined throughout the entire period. Reduced spatial and temporal availability of sea ice is expected to increasingly force population dynamics of polar bears as the climate continues to warm. However, in the short term, our findings suggest that factors other than sea ice can influence survival. A refined understanding of the ecological mechanisms underlying polar bear population dynamics is necessary to improve projections of their future status and facilitate development of management strategies. www.researchgate.net/publication/274314469_Polar_bear_population_dynamics_in_the_southern_Beaufort_Sea_during_a_period_of_sea_ice_decline
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Post by tyrannosaurs on Jul 10, 2021 13:41:11 GMT -5
Hoarding Behavior in Polar Bears By Dr. Thea Bechshoft, Staff Scientist Just when you thought you knew everything about polar bears, new information comes to light. In this case, a recent scientific paper explores caching behavior in some bears—including kills hidden under the snow and guarded, providing a secret stash to feast on over a period of one to several days. The study, led by Dr. Ian Stirling, is the first comprehensive look at this behavior, pulling together data on caching from an impressive number of polar bears and places around the Arctic. “My curiosity about short-term food caching was re-activated by receiving a photo from a friend of a male polar bear lying on the ice with a mostly snow-covered harp seal [1a above],” Stirling said. “I had seen this kind of behavior only once in over 40 years of research on polar bears. On talking with colleagues—Kristin Laidre, Andy Derocher, and Rinie van Meurs—all had seen this behavior, but only rarely. “Since polar bears evolved from brown (grizzly) bears only about half a million years ago, but caching is a frequent occurrence in the latter, we wondered why they were so different. That led to a wider search for observations and some speculation about why the different pattern of behavior might have evolved in polar bears.” Unusual but not unheard of The study, published in NRC Research Press, documents food-storing behavior in just 19 individual polar bears out of thousands observed over a 45-year period. Despite the rarity of the behavior, the case stories add fascinating insights into the polar bear’s ecology, behavior, and evolution. A polar bear’s feeding schedule is unpredictable, to say the least. Even though bears on the sea ice constantly watch for seals and other prey, they don’t know when the next potential meal will appear on the horizon and whether the hunt for it will be successful. The uncertainty still exists even after a successful hunt. Will other polar bears in the area move in and try to steal the fresh kill from under their paws? A polar bear can eat 10 to 20 percent of its own body mass in one go, a trait that is exceedingly practical, allowing a bear to eat as much of a seal’s fat layer as possible before a potential competitor shows up. Even so, adult seals are too big for most polar bears to eat in one go. This means the bear will have to decide: Will it leave the leftovers behind and go on an uncertain search of another seal, choosing instead to maximize the chances of finding new prey? Or will it stay, sleep off the meal, and hope to eat a bit more of the kill later – meanwhile, running the risk that another bear will move in and eat it first? Some bears choose the latter and may even—as described in the new paper—bury their leftovers (or a carcass if they happen to come across one) under a blanket of snow in an attempt to dissuade other bears from coming into the area to investigate. Although the snow cover is unlikely to cover up the smell, it will at least presumably make the sight of the kill less conspicuous on the otherwise white surface of the sea ice. Determining factors The authors found that some factors were likely important in determining whether an individual polar bear cached its prey or not: size of the killed prey, how much was left of the kill after the bear had first had its fill, and how deep the snow was on the ice around the kill. The authors also speculated that skinnier bears might be more likely to cache their food. Caching kills or scavenged carcasses is a well-known phenomenon in brown bears, the closest relative to the polar bear. Over time, however, the differences in ecology between the two species would likely have shaped the frequency with which they cache—for example, brown bears occur in much higher densities than polar bears do, so they have a higher incentive to want to hide their kill. Further, brown bears compete with a lot of very efficient scavengers (ravens, for example, have been found able to remove 2-37 kilograms of food per day from a carcass!) while polar bears only have the occasional Arctic fox and a low number of birds to worry about. “Basically, the fat and meat from smaller seals, such as pup or yearling ringed seals are largely devoured immediately, leaving little to hoard,” Stirling said. “In contrast, the carcasses of adult ringed seals, harp seals, and bearded seals may be covered with snow, to reduce the chance of kleptoparasitism [theft] by another bear or other scavengers visually detecting a dark spot on the ice, while the hoarding bear lies nearby.” Although less than 0.5% of the polar bears included in the paper exhibited caching behavior, the story it paints is wonderful, adding another little piece of the puzzle to our knowledge of everyday polar bear life far out on the Arctic sea ice. If you’re curious for more details of the study, it can be accessed here. Source: polarbearsinternational.org/news/article-research/hoarding-behavior-in-polar-bears/
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Post by tyrannosaurs on Jul 10, 2021 13:43:35 GMT -5
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Post by tyrannosaurs on Jul 10, 2021 13:48:59 GMT -5
Demography and behavior of polar bears summering on land in Alaska: Polar bears (Ursus maritimus) in the southern Beaufort Sea population (SB) are spending increased time on the coastal North Slope of Alaska between July and October (Gleason and Rode 2010). The duration spent on land by polar bears, satellite collared on the sea-ice in the spring, during the summer and fall has also increased (USGS, unpublished data; Figure 1). This change in polar bear ecology has relevance for human-bear interactions, subsistence harvest, prevalence of defense kills, and disturbance associated with existing land-based development [e.g., National Petroleum Reserve of Alaska (NPRA), Arctic National Wildlife Refuge (ANWR)], Native Alaskan communities, recreation (ANWR) and tourism (e.g., bear viewing in Kaktovik, AK). These activities have the potential to impact, in new ways, the status of the entire SB population. Concomitantly, the change in polar bear ecology will impact these human activities, and a base-line characterization of this phenomenon can better inform mitigation (e.g., industry permitting under the Endangered Species Act and Marine Mammal Protection Act). In this study we aim to characterize the demography, habitat-use, and aspects of foraging ecology and health of polar bears spending fall on land. The SB population is characterized by a divergent-sea ice ecology, where polar bears typically spend most of the year on the sea-ice, even as the pack ice retreats northward, away from the coast, to its minimal extent in September (Amstrup et al. 2008; Durner et al. 2009). From 2000 – 2005, using coastal aerial surveys, Schliebe et al. (2008) observed between 3.7 and 8% of polar bears from SB (~ 60 – 120 of 1526, Regher et al. 2006) on land during the autumn. Sighting probability was not estimated in these surveys, and therefore the numbers represent minimum numbers of bears on land. Our analysis of USGS data suggest an annual average of 15% (± 3%, SE) of polar bears satellite-tagged on the spring-time sea ice (total n = 18 of 124 satellite tags, 2003 – 2009) come to land during July – October. Based on these data, and an assumption that bears satellite-tagged on the spring time sea ice are representative of the entire SB population of independent bears, there would be an average of 230 bears on land each fall. In contrast to the SB population, in five of the world’s 19 polar bear populations (Obbard et al. 2010), polar bears spend significant periods of time on land (1 – 5 months) when ice completely melts. In these seasonal-ice populations (Amstrup et al. 2008), polar bears are largely in a hypophagic condition (e.g., Hobson et al. 2009), relying on fat stores from the spring hyperphagic season, when ringed seals (Phoca hispida) pup. In general, these seasonal-ice populations are demographically productive (Taylor et al. 2005), although recently an increase in the ice-free season has resulted in a population decline in western Hudson Bay (Stirling et al. 1999; Regehr et al. 2007). There have been measured declines in the body condition and productivity of polar bears in SB, and changes in these parameters have been linked to declining optimal ice habitat (e.g., Durner et al. 2009; Regehr et al. 2010). We do not understand the relationship between land-use and the overall status of the population. Individual polar bears that use land may have increased or decreased fitness, in comparison to polar bears that remain on ice in the autumn. This project, which focuses on the biology of animals that spend time on-shore, will help address this question. This project is funded by the Bureau of Ocean Energy Management (BOEM) under Agreement No. M09PG00025 and the USGS Outer Continental Shelf Program (OCS) for FY 2009-2014. Parts of this study are also funded by US Fish and Wildlife Service, Office of Marine Mammals Management; the Bureau of Land Management; and the North Slope Borough, Department of Wildlife Management. This report is comprehensive, describing results for achieving the overlap Study area: photos.app.goo.gl/r7P6Qj5377AvPi989Source: pubs.er.usgs.gov/publication/70136151
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Post by tyrannosaurs on Jul 10, 2021 14:16:34 GMT -5
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Post by tyrannosaurs on Jul 10, 2021 14:44:01 GMT -5
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Post by tyrannosaurs on Jul 25, 2021 10:45:54 GMT -5
Clash of the fiercest predators as shark eats polar bear: Global warming may not be the only threat to the polar bear. Scientists are puzzling over the discovery of the jawbone of a young polar bear in the stomach of a Greenland shark, a species that thrives in the cold waters of the far north. The find suggests that the polar bear may have a serious challenger to its place at the top of the Arctic food chain. Until now, only killer whales were thought to offer a threat to Ursus maritimus as the Arctic's top predator. Kit Kovacs, a seal expert at the Norwegian Polar Institute in Tromso, stumbled across the polar bear remains while attempting to find out who or what was killing large numbers of harbour seals in the Arctic archipelago of Svalbard. The Greenland shark, one of two species of sleeper sharks, was the obvious suspect, she said, so they performed autopsies to see what they had been eating. That's when they found the polar bear bone. "We were so shocked we were laughing," Ms Kovacs said. The prospect of a marine battle between the world's largest land predator and the Greenland shark which can grow to a length of more than six metres, is a true clash of the titans. And it is one that is likely to have wildlife film-makers rushing for the North Pole. Climate change has been melting polar ice cover and shrinking the natural habitat for the polar bear, now regarded as an endangered species. With polar sea ice expected to disappear altogether during the Arctic summer within a generation there is speculation that the bears may be spending longer in the water, while hunting or moving between icebergs. This could make them a potential target for large marine predators. Warmer waters may also be tempting more and larger sharks further north. Shark experts were unconvinced and think it more likely that the shark would have fed on a bear's carcass, rather than killed a live bear, as even a young animal would be a fierce opponent. Steve Campana, head of the Canadian shark research laboratory at the Department of Fisheries and Oceans, said he had not heard of sharks attacking a bear before. "It sounds like a scavenge," he told Reuters, adding that it was a "million-dollar question" for researchers as to whether Greenland sharks were preying on polar bears. Ms Kovacs continued, however, to stand by her theory. Sleeper sharks, which are among the longest living of their species, can descend to depths of 2,200 metres, but seal blubber found in their stomachs by researchers indicates that they are seeking food in shallower waters. "We didn't know they went to the surface to feed," she said. "We can't say whether or not the shark took a swimming young bear or ate a carcass." One clue may come from what the scientists did not find in their examination of the shark: anthropods, tiny creatures that feast on carcasses, gaining access through eyes or belly buttons. Scavengers are usually full of anthropods but none were found in the stomach with the polar bear. "We don't know how active these sharks are as predators," Ms Kovacs said. That is the question scientists will seek to answer. Sleeper sharks are among the most numerous large sharks in the world and are prolific feeders which have thrived while other shark populations have plummeted. What Ms Kovacs and her research team have found suggests that they are also much more skilled hunters than was previously believed. Although no one has witnessed a kill, the scientists' findings appear to show that sleeper sharks can catch live seals, which are fast and agile prey.ball." The discovery of the polar bear's jawbone is likely to leave scientists guessing for some time, but Ms Kovacs said: "I won't be going swimming there again... They are incredibly cryptic, dark sharks, who move slowly and get in close." " Battle for top of the Arctic food chain Weight: Adults Greenland sharks and mature polar bears weigh in at more than one tonne. The bears just have the edge. Age: These sharks are among the oldest on the planet, some living for 200 years. Polar bears rarely live beyond 25. www.google.com/amp/s/www.independent.co.uk/climate-change/news/clash-of-the-fiercest-predators-as-shark-eats-polar-bear-891512.html%3fampThe account from 2008: www.mensjournal.com/adventure/greenland-shark-found-with-polar-bear-remains-in-stomach/
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Post by Gorilla king on Jul 25, 2021 11:12:56 GMT -5
Reply #27, sounds like they are not sure if the shark actually killed or just scavenged that polar bear.
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Post by tyrannosaurs on Jul 25, 2021 13:20:06 GMT -5
Of course, and it was also young. I don't think Greenland sharks would have much chances on killing a polar bear, but if it catches it in the water, the shark can definitely kill it. But, of course, polar bears are known for killing beluga whales, so I think a polar bear can kill a Greenland shark too. What do you think?
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Post by Gorilla king on Jul 25, 2021 13:31:33 GMT -5
Of course, and it was also young. I don't think Greenland sharks would have much chances on killing a polar bear, but if it catches it in the water, the shark can definitely kill it. But, of course, polar bears are known for killing beluga whales, so I think a polar bear can kill a Greenland shark too. What do you think? Yeah i agree. On water the shark should have the edge most times. But a polar bear would be able to win sometimes also in shallow water.
oldindigosilverback, what do you think mate? You are our polar bear expert.
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Tom
Sun bear
Posts: 16
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Post by Tom on Jul 25, 2021 15:38:30 GMT -5
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Post by oldindigosilverback on Jul 25, 2021 18:21:49 GMT -5
Of course, and it was also young. I don't think Greenland sharks would have much chances on killing a polar bear, but if it catches it in the water, the shark can definitely kill it. But, of course, polar bears are known for killing beluga whales, so I think a polar bear can kill a Greenland shark too. What do you think? Yeah i agree. On water Mithe shark should have the edge most times. But a polar bear would be able to win sometimes also in shallow water.
oldindigosilverback , what do you think mate? You are our polar bear expert.There is at least one account of a polar bear attacking a beluga in the open waters. Therefore the polar bear is definitely capable of killing a Greenland shark. However, the shark moves faster than the beluga in open waters making it harder to catch meaning the shark will win more often than not in the waters.
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Post by tyrannosaurs on Aug 15, 2021 5:42:35 GMT -5
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Post by tyrannosaurs on Aug 15, 2021 5:43:03 GMT -5
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Post by tyrannosaurs on Aug 15, 2021 15:02:42 GMT -5
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Post by Gorilla king on Aug 15, 2021 15:50:52 GMT -5
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Post by oldindigosilverback on Aug 16, 2021 8:32:35 GMT -5
Looks like the polar bears will not be going extinct anytime soon . Their genes still live on in the grolar, prizzly, and ABC brown bears.
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Post by Gorilla king on Aug 28, 2021 9:58:01 GMT -5
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Post by Gorilla king on Aug 28, 2021 10:00:35 GMT -5
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