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| Polar Bear - Ursus maritimus | |
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| Tweet Topic Started: Jan 7 2012, 07:57 PM (26,214 Views) | |
| Taipan | Mar 15 2013, 05:29 PM Post #16 |
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DNA Study Clarifies How Polar Bears and Brown Bears Are Related ABC Island brown bears actually came from a population of polar bears that mated with male brown bears over thousands of years, new research suggests. Mar. 14, 2013 — At the end of the last ice age, a population of polar bears was stranded by the receding ice on a few islands in southeastern Alaska. Male brown bears swam across to the islands from the Alaskan mainland and mated with female polar bears, eventually transforming the polar bear population into brown bears. Evidence for this surprising scenario emerged from a new genetic study of polar bears and brown bears led by researchers at the University of California, Santa Cruz. The findings, published March 14 in PLOS Genetics, upend prevailing ideas about the evolutionary history of the two species, which are closely related and known to produce fertile hybrids. Previous studies suggested that past hybridization had resulted in all polar bears having genes that came from brown bears. But the new study indicates that episodes of gene flow between the two species occurred only in isolated populations and did not affect the larger polar bear population, which remains free of brown bear genes. At the center of the confusion is a population of brown bears that live on Alaska's Admiralty, Baranof, and Chicagof Islands, known as the ABC Islands. These bears--clearly brown bears in appearance and behavior--have striking genetic similarities to polar bears. "This population of brown bears stood out as being really weird genetically, and there's been a long controversy about their relationship to polar bears. We can now explain it, and instead of the convoluted history some have proposed, it's a very simple story," said coauthor Beth Shapiro, associate professor of ecology and evolutionary biology at UC Santa Cruz. Shapiro and her colleagues analyzed genome-wide DNA sequence data from seven polar bears, an ABC Islands brown bear, a mainland Alaskan brown bear, and a black bear. The study also included genetic data from other bears that was recently published by other researchers. Shapiro's team found that polar bears are a remarkably homogeneous species with no evidence of brown bear ancestry, whereas the ABC Islands brown bears show clear evidence of polar bear ancestry. A key finding is that the polar bear ancestry of ABC Islands brown bears is conspicuously enriched in the maternally inherited X chromosome. About 6.5 percent of the X chromosomes of the ABC Islands bears came recently from polar bears, compared to about 1 percent of the rest of their genome. This means that the ABC Islands brown bears share more DNA with polar bear females than they do with polar bear males, Shapiro said. To understand how hybridization could lead to this unexpected result, the team ran simulations of various demographic scenarios. "Of all the models we tested, the best supported was the scenario in which male brown bears wandered onto the islands and gradually transformed the population from polar bears into brown bears," said first author James Cahill, a graduate student in ecology and evolutionary biology at UC Santa Cruz. This scenario is consistent with the known behavior of brown bears and polar bears, according to coauthor Ian Stirling, a biologist at the University of Alberta in Edmonton, Canada. Mixing of polar bears and brown bears is seen today in the Canadian Beaufort Sea, where adult male brown bears wander onto the remaining sea ice in late spring and sometimes mate with female polar bears, he said. In areas such as western Hudson Bay and the Russian coast, polar bears are spending more time on land in response to climate warming and loss of sea ice, a behavior that could have left polar bears stranded on the ABC Islands at the end of the last ice age. Young male brown bears tend to leave the area where they were born in search of new territory. They may well have dispersed across the water from the Alaskan mainland to the ABC Islands and hybridized with polar bears stranded there when the sea ice disappeared. "The combination of genetics and the known behavior of brown and polar bears hybridizing in the wild today tells us how the ABC Islands bears came to be: they are the descendants of many male brown bear immigrants and some female polar bears from long ago," Stirling said. The findings suggest that continued climate warming and loss of arctic sea ice may lead to the same thing happening more broadly, said coauthor Richard E. (Ed) Green, an assistant professor of biomolecular engineering in UCSC's Baskin School of Engineering. "As the ice melts in the Arctic, what is going to happen to the polar bears? In the ABC Islands, the polar bears are gone. They're brown bears now, but with polar bear genes still present in their genomes," he said. The first genetic studies of ABC Islands brown bears looked at their mitochondrial DNA, which is separate from the chromosomes and is inherited only through the female lineage. The mitochondrial DNA of ABC Islands brown bears matches that of polar bears more closely than that of other brown bears, which led some scientists to think that the ABC Islands brown bears gave rise to modern polar bears. The new study looks at the "nuclear DNA" carried on the chromosomes in the cell nucleus. It is the latest in a series of genetic studies of polar bears published in recent years, each of which has prompted new ideas about the relationship between polar bears and brown bears. A 2010 study of fossils and mitochondrial DNA supported the idea that polar bears evolved from the ABC Islands brown bears. But a 2011 study of mitochondrial DNA from extinct Irish brown bears showed an even closer match to polar bears and suggested that polar bears got their mitochondrial DNA from hybridization with Irish bears. Shapiro, a coauthor of that study, said she now thinks the Irish brown bears may be another example of what happened in the ABC Islands, but she can't say for sure until she studies their nuclear DNA. "In retrospect, I think we were wrong about the directionality of the gene flow between polar bears and Irish brown bears," she said. Two studies published in 2012 sought to determine when the polar bear lineage diverged from the brown bear lineage using nuclear DNA data. The first, published in April in Science, put the split at 600,000 years ago and concluded that polar bears carry brown bear mitochondrial DNA due to past hybridizations. The second, published in July in Proceedings of the National Academy of Sciences, suggested that brown bears, black bears, and polar bears diverged around 4 to 5 million years ago, followed by repeated episodes of hybridization between polar bears and brown bears. The new study does not address the question of how long ago polar bears diverged from brown bears, but it may help sort out the conflicting results of recent studies. "It's a good step in the right direction of understanding what really happened," Shapiro said. The study does indicate that the divergence of polar bears from brown bears was only half as long ago as the split between the brown bear and black bear lineages, said Cahill. "We can tell how long brown bears and polar bears have been separate species as a proportion of how long ago they separated from more distantly related species, but putting a year on it is very difficult," he said. Green noted that efforts to understand the relationship between polar bears and brown bears has been complicated by the unusual case of the ABC Islands brown bears. "It's as if you were studying the relationship between humans and chimpanzees and your analysis included DNA from some weird population of humans that had hybridized with chimps. You would get very strange results until you figured that out," he said. In addition to Cahill, Green, Shapiro, and Stirling, the coauthors of the new paper include postdoctoral researchers Tara Fulton and Mathias Stiller, undergraduate Rauf Salamzade, and graduate student John St. John at UC Santa Cruz; Flora Jay and Montgomery Slatkin at UC Berkeley; and Nikita Ovsyanikov at the Wrangel Island State Nature Reserve in Russia. Green and Shapiro direct the UCSC Paleogenomics Lab. This research was funded by the Searle Scholars Program. http://www.sciencedaily.com/releases/2013/03/130314175654.htm Journal Reference: Cahill JA, Green RE, Fulton TL, Stiller M, Jay F, et al. Genomic Evidence for Island Population Conversion Resolves Conflicting Theories of Polar Bear Evolution. PLoS Genet, 9(3): e1003345; 2013 DOI: 10.1371/journal.pgen.1003345 Abstract Despite extensive genetic analysis, the evolutionary relationship between polar bears (Ursus maritimus) and brown bears (U. arctos) remains unclear. The two most recent comprehensive reports indicate a recent divergence with little subsequent admixture or a much more ancient divergence followed by extensive admixture. At the center of this controversy are the Alaskan ABC Islands brown bears that show evidence of shared ancestry with polar bears. We present an analysis of genome-wide sequence data for seven polar bears, one ABC Islands brown bear, one mainland Alaskan brown bear, and a black bear (U. americanus), plus recently published datasets from other bears. Surprisingly, we find clear evidence for gene flow from polar bears into ABC Islands brown bears but no evidence of gene flow from brown bears into polar bears. Importantly, while polar bears contributed <1% of the autosomal genome of the ABC Islands brown bear, they contributed 6.5% of the X chromosome. The magnitude of sex-biased polar bear ancestry and the clear direction of gene flow suggest a model wherein the enigmatic ABC Island brown bears are the descendants of a polar bear population that was gradually converted into brown bears via male-dominated brown bear admixture. We present a model that reconciles heretofore conflicting genetic observations. We posit that the enigmatic ABC Islands brown bears derive from a population of polar bears likely stranded by the receding ice at the end of the last glacial period. Since then, male brown bear migration onto the island has gradually converted these bears into an admixed population whose phenotype and genotype are principally brown bear, except at mtDNA and X-linked loci. This process of genome erosion and conversion may be a common outcome when climate change or other forces cause a population to become isolated and then overrun by species with which it can hybridize. http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1003345 Edited by Taipan, Oct 2 2017, 02:32 PM.
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| Taipan | Mar 20 2013, 05:14 PM Post #17 |
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For Polar Bears, It's Survival of the Fattest This is a subadult polar bear on a lake on the shores of Hudson Bay in Manitoba, Canada in November waiting for the sea ice to re-form. Mar. 20, 2013 — One of the most southerly populations of polar bears in the world -- and the best studied -- is struggling to cope with climate-induced changes to sea ice, new research reveals. Based on over 10 years' data the study, published in the British Ecological Society's Journal of Animal Ecology, sheds new light on how sea ice conditions drive polar bears' annual migration on and off the ice. Lead by Dr Seth Cherry of the University of Alberta, the team studied polar bears in western Hudson Bay, where sea ice melts completely each summer and typically re-freezes from late November to early December. "This poses an interesting challenge for a species that has evolved as a highly efficient predator of ice-associated seals," he explains. "Because although polar bears are excellent swimmers compared with other bear species, they use the sea ice to travel, hunt, mate and rest." Polar bears have adapted to the annual loss of sea ice by migrating onto land each summer. While there, they cannot hunt seals and must rely on fat reserves to see them through until the ice returns. Dr Cherry and colleagues wanted to discover how earlier thawing and later freezing of sea ice affects the bears' migration. "At first glance, sea ice may look like a barren, uniform environment, but in reality, it's remarkably complex and polar bears manage to cope, and even thrive, in a habitat that moves beneath their feet and even disappears for part of the year. This is an extraordinary biological feat and biologist still don't fully understand it," he says. From 1991-97 and 2004-09, they monitored movements of 109 female polar bears fitted with satellite tracking collars. They tagged only females because males' necks are wider than their heads, so they cannot wear a collar. During the same period, the team also monitored the position and concentration of sea ice using satellite images. "Defining precisely what aspects of sea ice break-up and freeze-up affect polar bear migration, and when these conditions occur, is a vital part of monitoring how potential climate-induced changes to sea ice freeze-thaw cycles may affect the bears," he says. The results reveal the timing of polar bears' migration can be predicted by how fast the sea ice melts and freezes, and by when specific sea ice concentrations occur within a given area of Hudson Bay. According to Dr Cherry: "The data suggest that in recent years, polar bears are arriving on shore earlier in the summer and leaving later in the autumn. These are precisely the kind of changes one would expect to see as a result of a warming climate and may help explain some other studies that are showing declines in body condition and cub production." Recent estimates put the western Hudson Bay polar bear population at around 900 individuals. The population has declined since the 1990s, as has the bears' body condition and the number of cubs surviving to adulthood. Because polar bears' main food source is seals, and these are hunted almost exclusively on sea ice, the longer bears spend on land, the longer they must go without energy-rich seals. "Climate-induced changes that cause sea ice to melt earlier, form later, or both, likely affect the overall health of polar bears in the area. Ultimately, for polar bears, it's survival of the fattest," says Dr Cherry. He hopes the results will enable other scientists and wildlife managers to predict how potential climate-induced changes to sea ice freeze-thaw cycles will affect the ecology, particularly the migration patterns, of this iconic species. https://www.sciencedaily.com/releases/2013/03/130319202040.htm Journal Reference: Seth G. Cherry, Andrew E. Derocher, Gregory W. Thiemann, Nicholas J. Lunn. Migration phenology and seasonal fidelity of an Arctic marine predator in relation to sea ice dynamics. Journal of Animal Ecology, 2013; DOI: 10.1111/1365-2656.12050 Summary Understanding how seasonal environmental conditions affect the timing and distribution of synchronized animal movement patterns is a central issue in animal ecology. Migration, a behavioural adaptation to seasonal environmental fluctuations, is a fundamental part of the life history of numerous species. However, global climate change can alter the spatiotemporal distribution of resources and thus affect the seasonal movement patterns of migratory animals. We examined sea ice dynamics relative to migration patterns and seasonal geographical fidelity of an Arctic marine predator, the polar bear (Ursus maritimus). Polar bear movement patterns were quantified using satellite-linked telemetry data collected from collars deployed between 1991–1997 and 2004–2009. We showed that specific sea ice characteristics can predict the timing of seasonal polar bear migration on and off terrestrial refugia. In addition, fidelity to specific onshore regions during the ice-free period was predicted by the spatial pattern of sea ice break-up but not by the timing of break-up. The timing of migration showed a trend towards earlier arrival of polar bears on shore and later departure from land, which has been driven by climate-induced declines in the availability of sea ice. Changes to the timing of migration have resulted in polar bears spending progressively longer periods of time on land without access to sea ice and their marine mammal prey. The links between increased atmospheric temperatures, sea ice dynamics, and the migratory behaviour of an ice-dependent species emphasizes the importance of quantifying and monitoring relationships between migratory wildlife and environmental cues that may be altered by climate change. Source Edited by Taipan, Oct 2 2017, 02:35 PM.
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| Jinfengopteryx | May 18 2013, 02:59 AM Post #18 |
Aspiring paleontologist, science enthusiast and armchair speculative fiction/evolution writer
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This year, a relatively comprehensive (and well illustrated) book has been published. Here the preview: http://books.google.com/books?id=Kd6b6I3L5vkC&lpg=PP1&hl=de&pg=PP1#v=onepage&q&f=false |
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| Jinfengopteryx | May 18 2013, 03:21 AM Post #19 |
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Aspiring paleontologist, science enthusiast and armchair speculative fiction/evolution writer
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Marianne Iversen, Jon Aars, Tore Haug, Inger G. Alsos, Christian Lydersen, Lutz Bachmann, Kit M. Kovacs (2013) The diet of polar bears (Ursus maritimus) from Svalbard, Norway, inferred from scat analysis Polar Biology Volume 36, Issue 4, pp. 561-571 Here the pdf: http://www.ub.uit.no:8080/munin/bitstream/handle/10037/3714/thesis.pdf?sequence=1 |
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| Taipan | Jul 24 2013, 05:40 PM Post #20 |
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Environmental Toxins Enter the Brain Tissue of Polar Bears Scientists have been monitoring the polar bear for contaminants in East Greenland over the past 30 years. They are worried by the findings of bioaccumulated perfluoroalkyl substances (PFASs) in the brain. July 23, 2013 — Scientists from Denmark and Canada are worried by their new findings showing that several bioaccumulative perfluoroalkyl substances (PFASs) are crossing the blood brain barrier of polar bears from Scoresby Sound, East Greenland. PerFluoroAlkyl Substances (PFASs) and precursor compounds have been used in a wide variety of commercial and industrial products over the past six decades. Applications include water and oil repellent coatings, e.g. for textiles, paper products, carpets and food packaging, pharmaceuticals and surfactants in cleaning products and fire-fighting foams. PFASs are highly resistant to chemical, thermal and biological degradation. PFASs and their precursor compounds have shown a dramatic increase and dispersal around the world over the past four decades. An increasing amount of information is becoming available on the toxicity of these compounds. Hence, studies have documented the toxicity of PFASs on wildlife and human health, including carcinogenesis, genotoxicity and epigenetic effects as well as reproductive and developmental toxicities, neurotoxicity, effects on the endocrine system and immunotoxicity. Bioaccumulative PFASs enter all parts of the brain Despite the fact that the liver is considered the major repository in the body for most PFASs, some shorter chain compounds from this grouping have previously been reported in the brain of chicken embryos, suggesting that they are able to cross the blood-brain barrier. Previous studies have shown a dramatic biomagnification of several PFASs, and particularly one known as perfluorooctane sulfonate (PFOS) as well as several compounds of the perfluorinated carboxylate (PFCAs) grouping, in polar bears. PFOS have been shown to be at concentrations in the liver that are 100 fold higher than the ringed seals on which they are predating. In a new study Arctic researchers from Carleton University in Canada and Aarhus University in Denmark have used the polar bear as a sentinel species for humans and other predators in the top of the food chain. The researchers demonstrated accumulation of PFOS and several PFCAs in eight brain regions of polar bears collected from Scoresby Sound, East Greenland. Dr. Robert Letcher, Carleton University, explains: "We know that fat soluble contaminants are able to cross the brain-blood barrier, but is it quite worrying that the PFOS and PFCAs, which are more associated with proteins in the body, were present in all the brain regions we analyzed." Professor Rune Dietz, Aarhus University, is also worried about the results: "If PFOS and PFCAs can cross the blood-brain barrier in polar bears, it will also be the case in humans. The brain is one of the most essential parts of the body, where anthropogenic chemicals can have a severe impact. However, we are beginning to see the effect of the efforts to minimize the dispersal of this group of contaminants." Select environmentally labeled products The eight carbon chain PFOS and perfluorooctane carboxylate (PFOA) are PFASs have been phased out and are no longer produced in the western world. However, production in China, today the only known production source of PFOS and PFOA, has increased by roughly a factor of 10, since it was phased out in the USA. Unfortunately, no emission inventory is so far available from this region. Furthermore, replacements for PFOS and PFOA are now marketed and produced in e.g. the U.S.A. and China, which generally have perfluorinated carbon chains that are shorter or branched. Another recent study from Aarhus University documents that PFOS concentrations in Greenlandic polar bears and ringed seals started to decline after 2006. Other wildlife populations closer to the sources in Europe and North America have shown a decline prior to the Greenlandic animals. Rune Dietz comments: "It is promising to see that the PFAS are on the decline. This development should be encouraged by the authorities globally. In the meantime my best advice to the consumers is to go for environmentally labeled products. But avoiding products is difficult, because PFASs are so widespread in many kind of products and they are rarely declared." FACTS With fluorine in the tail Perfluoroalkyl substances (PFASs) constitute a group of compounds where one end of the molecule consists of a carbon chain in which all the hydrogen atoms are replaced by fluorine atoms. This so-called perfluoroalkyl "tail" can be short or long, but the strong C-F bonds make the tail more or less impossible to degrade, compared to the more well known CFC-bonds. The best known PFAS is PFOS with an eight-chained perfluoroalkyl tail. http://www.sciencedaily.com/releases/2013/07/130723081350.htm Journal Reference: Greaves, A.K., R.J. Letcher, C. Sonne, R. Dietz. Brain region distribution and patterns of bioaccumulative perfluoroalkyl carboxylic and sulfonic acids in highly exposed East Greenland polar bears (Ursus maritimus). Environ. Toxicol. Chem., 2013 DOI: 10.1002/etc.2107 Abstract The present study investigated the comparative accumulation of perfluoroalkyl acids (PFAAs) in eight brain regions of polar bears (Ursus maritimus, n=19) collected in 2006 from Scoresby Sound, East Greenland. The PFAAs studied were perfluoroalkyl carboxylates (PFCAs, C6C15 chain lengths) and sulfonates (C4, C6, C8, and C10 chain lengths) as well as selected precursors including perfluorooctane sulfonamide. On a wet-weight basis, bloodbrain barrier transport of PFAAs occurred for all brain regions, although inner regions of the brain closer to incoming blood flow (pons/medulla, thalamus, and hypothalamus) contained consistently higher PFAA concentrations compared to outer brain regions (cerebellum, striatum, and frontal, occipital, and temporal cortices). For pons/medulla, thalamus, and hypothalamus, the most concentrated PFAAs were perfluorooctane sulfonate (PFOS), ranging from 47 to 58ng/g wet weight, and perfluorotridecanoic acid, ranging from 43 to 49ng/g wet weight. However, PFOS and the longer-chain PFCAs (C10C15) were significantly (p<0.002) positively correlated with lipid content for all brain regions. Lipid-normalized PFOS and PFCA (C10C15) concentrations were not significantly (p>0.05) different among brain regions. The burden of the sum of PFCAs, perfluoroalkyl sulfonates, and perfluorooctane sulfonamide in the brain (average mass, 392g) was estimated to be 46 mu g. The present study demonstrates that both PFCAs and perfluoroalkyl sulfonates cross the bloodbrain barrier in polar bears and that wet-weight concentrations are brain regionspecific. Edited by Taipan, Oct 2 2017, 02:37 PM.
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| Taipan | Sep 22 2013, 02:55 PM Post #21 |
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Climate Change: Polar Bears Change to Diet With Higher Contaminant Loads Harp seal with cub. Polar bears increasingly exchange ringed seal with harp seal and hooded seal in their diet and therefore become exposed to higher concentrations of contaminants. Sep. 20, 2013 — Over the past 30 years, polar bears have increasingly exchanged ringed seal with harp seal and hooded seal in their diet. This change exposes the polar bear to more contaminants, according to a recent international study. Researchers expect the climate to become warmer in the future and predict that climate change will have a significant impact on the Arctic. How will a warming Arctic affect the polar bears? The East Greenlandic population of polar bears resides in an area, where the Arctic sea ice is expected to disappear very late. However, the decline in the ice sheet here occurs at a rate of almost 1% per year, one of the highest rates measured in the entire Arctic region. How does this affect the prey of the polar bears -- and, in turn, the polar bears' intake of contaminants? An international team of researchers set out to explore this question. The team counted researchers from the Greenland Institute of Natural Resources, Aarhus University (Denmark) and a number of Canadian institutions including: Dalhousie University, Great Lakes Institute for Environmental Research, University of Windsor, Carleton University and the National Water Research Institute. The researchers studied the fatty acid profiles in the adipose tissue from a unique material of 310 polar bears hunted by East Greenland Inuits from the Scoresbysund area in the years from 1984 to 2011. The composition of fatty acids in the fat tissue of the polar bears namely reflects the profile of fatty acids in their diet. The results show that the polar bears primarily feed on three species of seals: the high Arctic ringed seal and the two sub-Arctic species harp seal and hooded seal. Moreover, the results showed that the diet of the polar bears had changed over the almost 30 years during which the samples were collected. In this period, the average relative decline in the ringed seal's significance for the polar bears diet was 42%. Similarly, the intake of the sub-Arctic seals increased during the same period. Also, the researchers found that polar bears are generally in better condition now, so at a first glance the polar bears should be happy with this development. Climate change undermines improvements There are, however, a couple of problems that might mar the happiness, explains Professor Rune Dietz, Aarhus University: "The problem is that the sub-Arctic seals that the polar bear has switched to, have a higher content of contaminants because they live closer to the industrialised world and are higher up in the food chain. Therefore, climate change undermines the improvements that you would otherwise have obtained owing to international regulations in the use of environmental use of persistent organic pollutants (POPs). We can see that the content of the POPs after year 2000 decreases slower in the polar bear than in, the ringed seal." In the long term, the polar bear may very well lose access to the sub-Arctic seals as these depend on packed ice where they give birth to their cubs and are exposed to sunlight allowing them to form vital vitamin D. http://www.sciencedaily.com/releases/2013/09/130920094748.htm Journal References: Melissa A. McKinney, Sara J. Iverson, Aaron T. Fisk, Christian Sonne, Frank F. Rigét, Robert J. Letcher, Michael T. Arts, Erik W. Born, Aqqalu Rosing-Asvid, Rune Dietz. Global change effects on the long-term feeding ecology and contaminant exposures of East Greenland polar bears. Global Change Biology, 2013; 19 (8): 2360 DOI: 10.1111/gcb.12241 Rune Dietz, Frank F. Rigét, Christian Sonne, Erik W. Born, Thea Bechshøft, Melissa A. McKinney, Robert J. Letcher. Three decades (1983–2010) of contaminant trends in East Greenland polar bears (Ursus maritimus). Part 1: Legacy organochlorine contaminants. Environment International, 2013; 59: 485 DOI: 10.1016/j.envint.2012.09.004 Rune Dietz, Frank F. Rigét, Christian Sonne, Erik W. Born, Thea Bechshøft, Melissa A. McKinney, Robert J. Drimmie, Derek C.G. Muir, Robert J. Letcher. Three decades (1983–2010) of contaminant trends in East Greenland polar bears (Ursus maritimus). Part 2: Brominated flame retardants. Environment International, 2013; 59: 494 DOI: 10.1016/j.envint.2012.09.008 Edited by Taipan, Oct 2 2017, 02:38 PM.
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| Taipan | Jan 23 2014, 07:56 PM Post #22 |
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Polar Bear Diet Changes as Sea Ice Melts A polar bear, Ursus maritmus, eats a caribou. Jan. 22, 2014 — A series of papers recently published by scientists at the American Museum of Natural History suggests that polar bears in the warming Arctic are turning to alternate food sources. As Arctic sea ice melts earlier and freezes later each year, polar bears have a limited amount of time to hunt their historically preferred prey -- ringed seal pups -- and must spend more time on land. The new research indicates that at least some polar bears in the western Hudson Bay population are using flexible foraging strategies while on land, such as prey-switching and eating a mixed diet of plants and animals, as they survive in their rapidly changing environment. "There is little doubt that polar bears are very susceptible as global climate change continues to drastically alter the landscape of the northern polar regions," said Robert Rockwell, a research associate in the Museum's Department of Ornithology. "But we're finding that they might be more resilient than is commonly thought." Polar bears are listed as a threatened species under the United States Endangered Species Act and are classified as "vulnerable" with declining populations on the International Union for Conservation of Nature and Natural Resources' Red List. Climate warming is reducing the availability of their ice habitat, especially in the spring when polar bears gain most of their annual fat reserves by consuming seal pups before coming ashore for the summer. The new work, led by Rockwell and Linda Gormezano, a postdoctoral researcher in the Museum's Division of Vertebrate Zoology, examines how polar bears might compensate for energy deficits from decreasing seal-hunting opportunities. In the first paper, published in spring 2013 in the journal Polar Ecology, the researchers provide, for the first time, data and video of polar bears pursuing, catching, and eating adult and juvenile lesser snow geese during mid-to-late summer, when the geese are replacing their primary flight feathers. In the second paper, published in summer 2013 in the journal Ecology and Evolution, researchers used polar bear scat to show that the diet of at least some of the bears has shifted from what it was 40 years ago, before climate change was affecting the Hudson Bay lowlands. Today's polar bears are preying more on caribou as well as on snow geese and their eggs. In the final paper in the series, published in December 2013 in the journal BMC Ecology, the researchers show that polar bears are, with a few exceptions, consuming a mixed diet of plants and animals. The predominance of local vegetation in collected scat suggests little movement among habitat types between feeding sessions, indicating that the polar bears are keeping energy expenditure down. Taken together, the research indicates that during the ice-free period, polar bears are exhibiting flexible foraging behavior. This behavior likely derives from a shared genetic heritage with brown bears, from which polar bears separated about 600,000 years ago. "For polar bear populations to persist, changes in their foraging will need to keep pace with climate-induced reduction of sea ice from which the bears typically hunt seals," Gormezano said. "Although different evolutionary pathways could enable such persistence, the ability to respond flexibly to environmental change, without requiring selective alterations to underlying genetic architecture, may be the most realistic alternative in light of the fast pace at which environmental changes are occurring. Our results suggest that some polar bears may possess this flexibility and thus may be able to cope with rapidly changing access to their historic food supply." Funding for this work was provided by the Hudson Bay Project; the American Museum of Natural History; Churchill Northern Studies Centre; City University of New York; and Manitoba Conservation. http://www.sciencedaily.com/releases/2014/01/140122104025.htm Journal References: D. T. Iles, S. L. Peterson, L. J. Gormezano, D. N. Koons, R. F. Rockwell. Terrestrial predation by polar bears: not just a wild goose chase. Polar Biology, 2013; 36 (9): 1373 DOI: 10.1007/s00300-013-1341-5 Abstract Behavioral predictions based on optimal foraging models that assume an energy-maximizing strategy have been challenged on both theoretical and empirical grounds. Although polar bears (Ursus maritimus) are specialist predators of seal pups on the Arctic ice pack, the use of terrestrial food sources during the ice-free period has received increased attention in recent years in light of climate predictions. Across a 10-day period of observation, we documented between four and six individual polar bears successfully capture at least nine flightless lesser snow geese (Chen caerulescens caerulescens) and engage in at least eight high-speed pursuits of geese. The observed predatory behaviors of polar bears do not support predictions made by energy-optimizing foraging models and suggest that polar bears may frequently engage in energy inefficient pursuits of terrestrial prey. Further study of the nutritional needs and foraging behaviors of polar bears during the ice-free period is warranted, given that polar bears are predicted to spend more time on land as climate change advances. http://link.springer.com/article/10.1007%2Fs00300-013-1341-5 Linda J. Gormezano, Robert F. Rockwell. What to eat now? Shifts in polar bear diet during the ice-free season in western Hudson Bay. Ecology and Evolution, 2013; DOI: 10.1002/ece3.740 Abstract Under current climate trends, spring ice breakup in Hudson Bay is advancing rapidly, leaving polar bears (Ursus maritimus) less time to hunt seals during the spring when they accumulate the majority of their annual fat reserves. For this reason, foods that polar bears consume during the ice-free season may become increasingly important in alleviating nutritional stress from lost seal hunting opportunities. Defining how the terrestrial diet might have changed since the onset of rapid climate change is an important step in understanding how polar bears may be reacting to climate change. We characterized the current terrestrial diet of polar bears in western Hudson Bay by evaluating the contents of passively sampled scat and comparing it to a similar study conducted 40 years ago. While the two terrestrial diets broadly overlap, polar bears currently appear to be exploiting increasingly abundant resources such as caribou (Rangifer tarandus) and snow geese (Chen caerulescens caerulescens) and newly available resources such as eggs. This opportunistic shift is similar to the diet mixing strategy common among other Arctic predators and bear species. We discuss whether the observed diet shift is solely a response to a nutritional stress or is an expression of plastic foraging behavior. http://onlinelibrary.wiley.com/doi/10.1002/ece3.740/abstract;jsessionid=1163E466AB2F50C52AA6FBFE637F6B14.f04t01 Linda J Gormezano, Robert F Rockwell. Dietary composition and spatial patterns of polar bear foraging on land in western Hudson Bay. BMC Ecology, 2013; 13 (1): 51 DOI: 10.1186/1472-6785-13-51 Background Flexible foraging strategies, such as prey switching, omnivory and food mixing, are key to surviving in a labile and changing environment. Polar bears (Ursus maritimus) in western Hudson Bay are versatile predators that use all of these strategies as they seasonally exploit resources across trophic levels. Climate warming is reducing availability of their ice habitat, especially in spring when polar bears gain most of their annual fat reserves by consuming seal pups before coming ashore in summer. How polar bears combine these flexible foraging strategies to obtain and utilize terrestrial food will become increasingly important in compensating for energy deficits from lost seal hunting opportunities. We evaluated patterns in the composition of foods in scat to characterize the foraging behaviors that underpin the diet mixing and omnivory observed in polar bears on land in western Hudson Bay. Specifically, we measured diet richness, proportions of plant and animal foods, patterns in co-occurrence of foods, spatial composition and an index of temporal composition. Results Scats contained between 1 and 6 foods, with an average of 2.11 (SE = 0.04). Most scats (84.9%) contained at least one type of plant, but animals (35.4% of scats) and both plants and animals occurring together (34.4% of scats) were also common. Certain foods, such as Lyme grass seed heads (Leymus arenarius), berries and marine algae, were consumed in relatively higher proportions, sometimes to the exclusion of others, both where and when they occurred most abundantly. The predominance of localized vegetation in scats suggests little movement among habitat types between feeding sessions. Unlike the case for plants, no spatial patterns were found for animal remains, likely due the animals' more vagile and ubiquitous distribution. Conclusions Our results suggest that polar bears are foraging opportunistically in a manner consistent with maximizing intake while minimizing energy expenditure associated with movement. The frequent mixing of plant-based carbohydrate and animal-based protein could suggest use of a strategy that other Ursids employ to maximize weight gain. Further, consuming high rates of certain vegetation and land-based animals that may yield immediate energetic gains could, instead, provide other benefits such as fulfilling vitamin/mineral requirements, diluting toxins and assessing new foods for potential switching. http://www.biomedcentral.com/1472-6785/13/51/abstract Edited by Taipan, Oct 2 2017, 02:40 PM.
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| Taipan | Feb 8 2014, 02:29 PM Post #23 |
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New Research Reveals How Polar Bears Stay Warm Cat Ferguson, ISNS Contributor | February 07, 2014 06:48pm ET  New calculations suggest polar bear fur might be so effective at trapping warmth because the hairs scatter infrared light. (ISNS) -- A polar bear’s pelt seems simple. The white color serves as camouflage, and the dense fur acts as a fuzzy blanket, keeping the cold out and the warm in. But how the coat insulates is surprisingly complex - and the subject of some debate. One suggestion, thoroughly debunked, posited that each hair served as a tiny heat pipeline, funneling the sun’s rays down to the skin like a fiber-optic cable. Scientists widely accept that warm coats (and fiberglass insulation) protect against the elements by trapping warm pockets of air in tiny pores. Now, it seems the pelt might have another way to insulate. Body heat that radiates from the bears’ skin as infrared light – the waves of warmth that night-vision goggles pick up –bounces around inside the coat, according to a paper in last month’s Optics Express. The researchers created a computer model representing a stack of polar bear hairs, to investigate how bears and other arctic animals keep warm. At first, they considered the hairs as flat layers. Each layer was a “black body,” designed to perfectly absorb all wavelengths and then perfectly emit them. Solar panels are matte black in an effort to achieve this ideal absorption. They then calculated how infrared waves would move back and forth between the layers. The scientists then imagined that the layers were slightly transparent as is the case with polar bear coats, and recalculated. The layers of fur then acted as “gray bodies,” which neither scatter nor absorb light perfectly; instead, they do some of both. “What is important is the number of hairs, and the density. The light will be reflected many times, and some will go back to the skin,” said Priscilla Simonis, a physicist at the University of Namur, in Belgium, and the lead author of the paper. There are three types of heat transfer. One is conduction, the process by which heat moves between two connected surfaces, such as from a stove coil into a pot. The second is convection, the movement of heat by liquids and gases, like the water in the spaghetti pot circulating from the bottom to the top. Most housing insulation capitalizes on these two types of heat, trapping hot air in a material that resists picking up heat through conduction, and keeping it in a small space so it doesn’t move as much. Scientists have long believed that animal coats do this, too. But the last kind of heat, thermal radiation, is what Simonis and her team believe is most effective at keeping in heat. Radiation is energy released in electromagnetic waves - it’s how the sun warms your skin on a hot day. It’s also how the thin, shiny blankets in emergency kits work: as heat waves radiate from you, they hit the blanket and scatter without heading too far away, keeping heat in. Infrared is the wavelength of thermal radiation that night-vision goggles detect, as living bodies give off heat. Polar bears are actually so well insulated, they’re invisible to night-vision goggles. “When people tried to track polar bears from the air, they couldn't use visible photography, because you can't see them against the snow. Then they tried infrared, but they still blended in with the surroundings. The obvious conclusion is that the pelt is the same temperature as its surroundings,” said Daniel Koon, a physicist from St. Lawrence University, in New York. In his own research, he debunked the fiber-optic theory. Every electromagnetic wave that hits a molecule is either absorbed and then radiated out again, or it ricochets. Polar bear fur both scatters and absorbs radiative heat. When heat is scattered, or absorbed and re-emitted, it tends to come off in random directions. The bears’ thick, dense fur has many of these stopping points on the way to the surface of the coat. Though the evolutionary basis is unclear, white coats take on double duty, both reflecting heat and blending in with the snow. Polar bears are camouflaged in visible light, too, of course. Sunlight scatters almost entirely off the fur. The sun doesn’t warm them, as scientists learned from disproving the cable-optic theory. This initial study modeled only 100 hairs. The team has begun building more realistic models that can calculate 100,000 hairs in random positions, taking into account all three dimensions. But to model everything infrared radiation does when trying to escape a pelt will take the University of Namur’s supercomputers several months to calculate, Simonis said. Polar bears aren’t the only animals this research applies to. Other arctic mammals, including foxes and rabbits, are likely using the same strategy. Birds, too, benefit from radiative insulation. There are also some interesting applications for building homes. “You can imagine a new type of insulating material,” Simonis said. “The more you reflect the [infrared] light, the more efficient the insulation.” http://www.livescience.com/43217-new-research-reveals-how-polar-bears-stay-warm.html Radiative contribution to thermal conductance in animal furs and other woolly insulators Priscilla Simonis, Mourad Rattal, El Mostafa Oualim, Azeddine Mouhse, and Jean-Pol Vigneron Optics Express, Vol. 22, Issue 2, pp. 1940-1951 (2014) http://dx.doi.org/10.1364/OE.22.001940 Abstract This paper deals with radiation’s contribution to thermal insulation. The mechanism by which a stack of absorbers limits radiative heat transfer is examined in detail both for black-body shields and grey-body shields. It shows that radiation energy transfer rates should be much faster than conduction rates. It demonstrates that, for opaque screens, increased reflectivity will dramatically reduce the rate of heat transfer, improving thermal insulation. This simple model is thought to contribute to the understanding of how animal furs, human clothes, rockwool insulators, thermo-protective containers, and many other passive energy-saving devices operate. http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-22-2-1940 Edited by Taipan, Oct 2 2017, 02:41 PM.
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| Taipan | Mar 26 2014, 02:00 PM Post #24 |
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Study yields 'Genghis Khan' of brown bears, and brown and polar bear evolution Date: March 25, 2014 Source: Molecular Biology and Evolution (Oxford University Press) Summary: By mining the genome of a recently sequenced polar bear, researchers developed Y chromosome-specific markers, and analyzed several regions of the Y chromosome from a broad geographic sample of 130 brown and polar bears. 'This pattern in brown bears covers even larger geographic areas than analogous findings from humans, where the Y-chromosomal lineage of Genghis Khan, founder of the Mongol Empire, was spread across much of Asia,' said experts. Male bears are seemingly always on the prowl, roaming much greater distances than females, particularly for mating. For bear evolution, studying the paternally inherited Y chromosome is therefore a rich source to trace both the geographic dispersal and genetic differences between bear species. This new study is particularly important, because a large part of our current knowledge about range-wide population structuring in mammals relies on data from maternally inherited mitochondrial DNA (mtDNA). More extensive male than female movement in bears and many other mammals implies that males carry genetic material over greater geographic distances than females. Therefore, the pronounced population structuring that has been reported for female-inherited mtDNA genes in brown bears might not be representative of the species as a whole. By mining the genome of a recently sequenced polar bear, researchers from Axel Janke´s group at the Biodiversity and Climate Research Centre in Frankfurt, Germany, developed Y chromosome-specific markers, and analyzed several regions of the Y chromosome from a broad geographic sample of 130 brown and polar bears. They also included a continuous 390,000 base pair long stretch of genomic Y chromosomal region available in brown, polar and black bear genomes to gain a better understanding of the paternal signature of bear evolution. They found evidence of extensive male gene flow that has led to the distribution of some brown bear Y chromosomes across incredibly large geographic distances, with two brown bears as far away as Norway and the Alaskan ABC islands carrying very similar Y chromosomes. This implies that one male brown bear lineage has spread across most of the brown bear's distribution range. "This pattern in brown bears covers even larger geographic areas than analogous findings from humans, where the Y-chromosomal lineage of Genghis Khan, founder of the Mongol Empire, was spread across much of Asia," said Tobias Bidon and Frank Hailer, lead authors of the study. Because their data consistently showed that black, brown and polar bears carry highly distinct Y chromosome lineages, the researchers also estimated the timing of the split between the male lineages of brown and polar bears. The obtained time estimate for the speciation event of brown and polar bears is ca. 0.4 to 1.1 million years ago. This is significantly older than previous estimates based on mtDNA, confirming recent observations from autosomal markers that brown and polar bears from a genetic point of view represent highly distinct species. The study also shows that dispersing males connect the enigmatic brown bear population of the Alaskan ABC-islands to the North American mainland, and that the resulting movement of genes is substantial enough to maintain high genetic variability within this island population. The study demonstrates that the Y chromosome represents an understudied part of the mammalian genome, providing crucial information to our understanding of the geographic structuring and evolutionary history of species. http://www.sciencedaily.com/releases/2014/03/140325210631.htm Journal Reference: Tobias Bidon, Axel Janke, Steven R. Fain, Hans Geir Eiken, Snorre B. Hagen, Urmas Saarma, Björn M. Hallström, Nicolas Lecomte, and Frank Hailer. Brown and polar bear Y chromosomes reveal extensive male-biased gene flow within brother lineages. Mol Biol Evol, March 25, 2014 DOI: 10.1093/molbev/msu109 Abstract Brown and polar bears have become prominent examples in phylogeography, but previous phylogeographic studies relied largely on maternally inherited mitochondrial DNA (mtDNA) or were geographically restricted. The male-specific Y chromosome, a natural counterpart to mtDNA, has remained under-explored. Although this paternally inherited chromosome is indispensable for comprehensive analyses of phylogeographic patterns, technical difficulties and low variability have hampered its application in most mammals. We developed 13 novel Y-chromosomal sequence and microsatellite markers from the polar bear genome, and screened these in a broad geographic sample of 130 brown and polar bears. We also analyzed a 390 kb-long Y-chromosomal scaffold using sequencing data from published male ursine genomes. Y chromosome evidence support the emerging understanding that brown and polar bears started to diverge no later than the Middle Pleistocene. Contrary to mtDNA patterns, we found (i) brown and polar bears to be reciprocally monophyletic sister (or rather brother) lineages, without signals of introgression, (ii) male-biased gene flow across continents and on phylogeographic time scales, and (iii) male dispersal that links the Alaskan ABC-islands population to mainland brown bears. Due to female philopatry, mtDNA provides a highly structured estimate of population differentiation, while male-biased gene flow is a homogenizing force for nuclear genetic variation. Our findings highlight the importance of analyzing both maternally and paternally inherited loci for a comprehensive view of phylogeographic history, and that mtDNA-based phylogeographic studies of many mammals should be re-evaluated. Recent advances in sequencing technology render the analysis of Y chromosomal variation feasible, even in non-model organisms. http://mbe.oxfordjournals.org/content/early/2014/03/20/molbev.msu109 |
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| Vodmeister | Apr 8 2014, 06:37 AM Post #25 |
Ultimate Predator
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Polar Bears from Fox Basin average close to 590 kg, or 1300 pounds.  Some of the heaviest known polar bears on record; 
Edited by Taipan, Oct 2 2017, 02:41 PM.
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| Taipan | Apr 23 2014, 09:30 PM Post #26 |
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Polar Bears on Thin Ice, Arctic Expedition Finds By Tanya Lewis, Staff Writer | April 22, 2014 10:07am ET  A researcher fits a sedated polar bear with a geo-location ear tag, as part of the 2014 NPI and WWF-Canon expedition to Svalbard, Norway. An expedition to the islands of Svalbard, Norway, to study how rising temperatures and melting sea ice are affecting polar bears concluded Monday (April 21). Over the 10-day trek, researchers outfitted female bears with satellite tracking collars that will send back data, giving researchers a picture of how shrinking sea ice may be affecting the polar bears' movements and denning patterns. "The bear denning habitats appear to be shifting further north," Geoff York, one of the expedition leaders, told Live Science via satellite phone from the team's ship in Svalbard Thursday (April 17). The team had so far deployed 11 of their 20 collars, York said. The 2013-2014 winter has seen record-low levels of sea ice — which the bears rely on to hunt — around Svalbard, said York, who is a polar bear researcher at the World Wildlife Fund. "The question is how the bears will respond as there's less and less sea ice." Researchers at the Norwegian Polar Institute have been monitoring the polar bears in Svalbard for years using tracking collars. This year, the WWF and camera maker Canon joined the effort, allowing the team to stay longer and put out more collars. The satellite data suggest there are two groups of bears: Those on the northern end of the archipelago mostly keep to the open water and sea ice, rarely coming onshore. Other bears stay mainly onshore in summertime, hardly ever leaving the islands. One thing the researchers don't know is exactly how many bears there are, York said. Researchers estimate there may be about 2,600, plus or minus a few hundred. Capturing a polar bear for tagging is no easy feat. A crew aboard a helicopter locates a bear and darts it with a sedative from the air. On the ground, the team measures the bear's length and weight, and takes blood and hair samples. The researchers only put collars on the adult females — the heads of male bears and cubs are smaller than their necks, so the collars don't stay on them. "All of the movement data is from adult female bears," York said. "We have very little data on cubs and males." The collars have sensors that record temperature, daylight, immersion in saltwater and depth. They tell researchers how much time the bears spend in the dens, and how often they go into the ocean to hunt. The bears primarily eat ringed seal, but they also eat bearded seals, young walruses and sometimes even beluga whales or narwhal, though more often, they eat whale carcasses, York said. Polar bears have also been known to cannibalize other bears, and male bears have been documented committing infanticide for food. http://www.livescience.com/45010-svalbard-polar-bear-expedition.html Edited by Taipan, Oct 2 2017, 02:45 PM.
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| Taipan | May 9 2014, 05:48 PM Post #27 |
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How Polar Bears Survive on 'Heart Attack' Diet By Tanya Lewis, Staff Writer | May 08, 2014 12:31pm ET  Polar bears have evolved genes that allow them survive on a fatty diet of seals and blubber. If humans ate the same fatty foods as polar bears, they would have heart attacks. But a new study reveals how these magnificent Arctic beasts survive on such a specialized diet. It turns out the beasts have evolved genes that allow them to survive on a diet of mostly seals and the blubber those animals contain, not to mention their sky-high cholesterol levels, without developing heart disease. The findings, detailed today (May 8) in the journal Cell, also showed that polar bears and brown bears diverged from each other much more recently than previously thought. "In this limited amount of time, polar bears became uniquely adapted to the extremities of life out on the Arctic sea ice, enabling them to inhabit some of the world's harshest climates and most inhospitable conditions," study leader Rasmus Nielsen, a theoretical evolutionary biologist at the University of California, Berkeley, said in a statement. In their study, Nielsen and his colleagues sequenced the complete genomes of 79 polar bears from Greenland and 10 brown bears from around the world. The researchers discovered that polar bears and brown bears branched off from a common ancestor sometime in the last 500,000 years, compared with previous data that suggested the two species diverged up to 5 million years ago. Since splitting off from brown bears, polar bears have evolved quickly through mutations in genes that play roles in heart function and the metabolism of fatty acids, the study found. These same genes have been linked to human heart disease The dramatic genetic changes in response to a fatty diet have not been reported before, suggesting that scientists should look beyond standard model organisms in studying the genetic causes of human heart disease, the researchers said. http://www.livescience.com/45449-how-polar-bears-survive-on-fatty-diet.html Population Genomics Reveal Recent Speciation and Rapid Evolutionary Adaptation in Polar Bears Shiping Liu20, Eline D. Lorenzen, Matteo Fumagalli, Bo Li, Kelley Harris, Zijun Xiong, Long Zhou, Thorfinn Sand Korneliussen, Mehmet Somel21, Courtney Babbitt22, Greg Wray, Jianwen Li, Weiming He, Zhuo Wang, Wenjing Fu, Xueyan Xiang, Claire C. Morgan, Aoife Doherty, Mary J. O’Connell, James O. McInerney, Erik W. Born, Love Dalén, Rune Dietz, Ludovic Orlando, Christian Sonne, Guojie Zhang, Rasmus Nielsenemail, Eske Willerslevemail, Jun Wangemail DOI: http://dx.doi.org/10.1016/j.cell.2014.03.054 Highlights •de novo assembly of a polar bear reference genome •Polar bears and brown bears diverged only ca. 400,000 years ago •Genes on the polar bear lineage have been under stronger selection than brown bears •Strong selection in polar bears restructured metabolic and cardiovascular function Summary Polar bears are uniquely adapted to life in the High Arctic and have undergone drastic physiological changes in response to Arctic climates and a hyperlipid diet of primarily marine mammal prey. We analyzed 89 complete genomes of polar bear and brown bear using population genomic modeling and show that the species diverged only 479–343 thousand years BP. We find that genes on the polar bear lineage have been under stronger positive selection than in brown bears; nine of the top 16 genes under strong positive selection are associated with cardiomyopathy and vascular disease, implying important reorganization of the cardiovascular system. One of the genes showing the strongest evidence of selection, APOB, encodes the primary lipoprotein component of low-density lipoprotein (LDL); functional mutations in APOB may explain how polar bears are able to cope with life-long elevated LDL levels that are associated with high risk of heart disease in humans.  Polar and brown bear distributions are shown in blue and brown shading, respectively. http://www.cell.com/cell/abstract/S0092-8674(14)00488-7 Edited by Taipan, Oct 2 2017, 02:47 PM.
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| Sam1 | May 10 2014, 02:09 AM Post #28 |
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Specifically evolved into a fat-eater http://www.newscientist.com/article/dn25535-zoologger-polar-bears-evolved-to-eat-junk-food.html?utm_source=NSNS&utm_medium=SOC&utm_campaign=facebookgoogletwitter&cmpid=SOC%7CNSNS%7C2012-GLOBAL-facebookgoogletwitter#.U2z-meAYYuo Edited by Sam1, May 10 2014, 02:11 AM.
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| Ursus arctos | Jul 3 2014, 06:21 AM Post #29 |
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I'm short, on time, but this sounds awesome! Hair from the Himalayas matches DNA extracted from 40,000 year old polar bears!!! Abominable news: scientists rule out yetis The yeti, and his shambling hairy cousins the bigfoot, almasty, sasquatch and migyur, may still be out there, high in the snowy peaks of the Himalayas, Rocky Mountains or Urals – but they have escaped a team of scientists who have been testing dozens of samples, all claimed to be genuine chunks of yeti fur. They have turned out to be hairs from depressingly familiar animals including cows, raccoons, horses, dogs, sheep, a Malayan tapir, a porcupine, and, in the case of one sample from Texas, a human being. And also a blade of grass and a strand of fibreglass. "Don't give up yet, the yeti may still be out there," Bryan Sykes said reassuringly. The professor of human genetics at Oxford and an expert on ancient DNA, said he launched the project, writing to museums and collectors all over the world, with only a 5% hope of success. "That would normally be too slim a margin to launch a major study," Sykes said, "but I did think there was just a chance we would uncover something extraordinary." What he hoped for was less the abominable snowman of legend than evidence for a surviving Neanderthal, which some say could be the origin of yeti stories. He found neither. However, the team, which publishes its findings in this week's Proceedings of the Royal Society, has found something almost equally extraordinary, in two samples of bear fur from Bhutan and the Indian Himalayas. Although one is reddish brown and the other golden brown, the bear's closest relative turned out to be a precise match for DNA extracted from fossil remains of a polar bear that lived 40,000 years ago. The samples were quite unlike modern polar bears. This raises the intriguing possibility that descendents of a prehistoric polar bear are at large in the Himalayas. The sample from Ladakh in India is said to be from an animal shot 40 years ago by an experienced hunter, who said the creature's behaviour was very different from the brown bears he knew well. He kept the pelt hidden, and, according to Sykes, was very reluctant to hand over samples to the French explorer who brought them back to the west. The other sample came from Bhutan, where yetis – referred to by the scientists as "anomalous primates" – are known as migyur. "Polar bears have some quite distinct behaviour, including deliberately hunting human prey," Sykes said. "It would be very interesting to go and see if this is a behavioural pattern which has endured in the Himalayan bears." The paper is the first such study in a peer-reviewed journal. Sykes, who is also publishing a book on yetis this autumn – "I wouldn't have done this as a young man, before I had an established reputation as a scientist," he admitted – said he was struck that science was accused by yeti enthusiasts of rejecting the notion of their existence. "This conflicts with the basic tenet that science neither rejects nor accepts anything without examining the evidence," the team wrote. Scientists had largely avoided "this often murky field" for more than half a century, Sykes said, since they joined expeditions in the 1950s led by Sir Edmund Hillary and other explorers. Back then, they could not have conducted sophisticated DNA testing. Samples poured in from collections all over the world, but the only mystery about most was the enduring one of human credulity. Two sent from Russia were claimed to be hairs from an almasty, the Russian version of the bigfoot. They proved to be raccoon and black bear hairs, both natives of North America. The tapir hair came from Sumatra, cow hairs from several places in the US along with the porcupine quill, and a hair from a serow, a goat like creature, from Nepal. "Absence of evidence is not evidence of absence, and this survey cannot refute the existence of anomalous primates," the authors wrote. There is more work to be done, Sykes said – but the grass and the fibreglass have definitely been eliminated from his inquiries. http://www.theguardian.com/world/2014/jul/02/yetis-ruled-out-by-scientists |
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| Taipan | Nov 21 2014, 12:50 PM Post #30 |
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Polar Bear Numbers Plummeting in Alaska, Canada—What About the Rest? Several populations of the Arctic predator are little studied, scientists say.  Polar bears (pictured, an animal in Manitoba, Canada) as a species are considered vulnerable to extinction. Linda Qiu National Geographic PUBLISHED NOVEMBER 19, 2014 A large population of polar bears in Alaska and Canada has decreased by 40 percent since the start of the new millennium, new research shows. The number of the large predators living in the southern Beaufort Sea plummeted from 1,500 animals in 2001 to just 900 in 2010, according to the study, published on November 17 in the journal Ecological Applications. But there's a lot we don't know about the 18 other known polar bear populations, which are scattered throughout the U.S., Canada, Russia, Greenland, Norway, and Denmark, experts say. For instance, nine groups, which live in places like northern Siberia, are little studied due to the remoteness of their locations and lack of funding. Of the most studied populations, four—including the southern Beaufort group—are declining, five are stable, and one, in north-central Canada's M'Clintock Channel (map), is actually increasing, scientists say. The species as a whole is decreasing in number, and is listed as vulnerable by the International Union for the Conservation of Nature. The reason for the variability in numbers is location, location, location. "If you're in the high Arctic, there's a greater possibility of population stability [because] there is more ice pack and prey availability," said David Koons, a National Geographic grantee who studies animal populations at Utah State University, in Logan. On Thin Ice The southern parts of the polar bear's range, such as the southern Beaufort Sea, are warming faster than the northern regions and are thus more susceptible to melting sea ice. As the ocean heats up due to global warming, Arctic sea ice has been locked in a downward spiral. Since the late 1970s, the ice has retreated by 12 percent per decade, and the decline has worsened since 2007, according to NASA. It's not surprising that the southern Beaufort Sea and its bears are feeling the effects first and more dramatically than those in more northern areas, said Ian Stirling, a biologist at the University of Alberta, in Edmonton, who is studying climate change's impact on polar bears. Polar bears in this region are declining because they use sea ice as hunting platforms to catch their primary prey, seals. But "when that ice is there, it's really jumbled up [due to freezing and refreezing events]," said study leader Jeff Bromaghin, a U.S. Geological Survey statistician who studies wildlife population dynamics. "The seals may be there, but [the polar bears] can't get to them." In 2007, the U.S. Geological Survey estimated that the global polar bear population will shrink to a third of its current size by 2050, due to loss of habitat and less access to prey. From the Beaufort numbers, it looks like things are right on track, or perhaps even speeding up, according to Bromaghin. "Nothing in this study contradicts the 2007 estimates," said Bromaghin. "Actually, observed loss of sea ice in the Arctic has been greater than earlier climate models. We're losing ice faster than forecasted." Can Polar Bears Cope? Faced with a less icy Arctic, some polar bears appear to be coping on land, in part by adding snow goose eggs and caribou to their diet. For a species that needs fat-rich, energy-dense foods, though, a diverse palate might not be enough, according to Bromaghin. "Sure, they're starting to use land when food sources are limited. They'll eat whatever they can catch. But it's not enough to sustain them in the long run," he said. "Every scrap of evidence suggests that polar bears are linked to sea ice. There's no evidence they can live on land." The fate of the species also remains unclear because so little is known about the understudied populations in the high Arctic, Utah State's Koons noted. Those bears may be in similarly dire straits, but it's just undocumented, the University of Alberta's Stirling pointed out. "The fundamental concept is simple," he said. "As we continue to lose ice, particularly during key feeding periods, numbers of polar bears will decline." http://news.nationalgeographic.com/news/2014/11/141119-polar-bears-arctic-warming-animals-science-alaska/ Edited by Taipan, Oct 2 2017, 02:49 PM.
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