[Show abstract][Hide abstract] ABSTRACT: Few studies have investigated the impacts of climate change on polar bears (Ursus maritimus) in East Greenland (EG), where some of the largest rates of sea ice loss have occurred. We used remotely sensed sea ice data to quantify changes in timing of sea ice freeze-up and breakup in EG polar bear habitat between 1979 and 2012. We then quantified movement rates, area use, habitat selection, and distribution and phenology of maternity denning using data from adult female polar bears tracked with satellite transmitters between 2007 and 2010 (n = 7). We compared results to historical data collected from adult females in the 1990s (n = 4). Adult females in the 2000s used areas with significantly lower sea ice concentrations (10-15 % lower) than bears in the 1990s during winter, a pattern influenced by delayed freeze-up in October-December. Adult females in the 2000s were located significantly closer (100-150 km) to open water in all seasons and spent approximately 2 months longer in areas with
[Show abstract][Hide abstract] ABSTRACT: We provide an expansive analysis of polar bear (Ursus maritimus) circumpolar genetic variation during the last two decades of decline in their sea-ice habitat. We sought to evaluate whether their genetic diversity and structure have changed over this period of habitat decline, how their current genetic patterns compare with past patterns, and how genetic demography changed with ancient fluctuations in climate. Characterizing their circumpolar genetic structure using microsatellite data, we defined four clusters that largely correspond to current ecological and oceanographic factors: Eastern Polar Basin, Western Polar Basin, Canadian Archipelago and Southern Canada. We document evidence for recent (ca. last 1–3 generations) directional gene flow from Southern Canada and the Eastern Polar Basin towards the Canadian Archipelago, an area hypothesized to be a future refugium for polar bears as climate-induced habitat decline continues. Our data provide empirical evidence in support of this hypothesis. The direction of current gene flow differs from earlier patterns of gene flow in the Holocene. From analyses of mitochondrial DNA, the Canadian Archipelago cluster and the Barents Sea
PLoS ONE 01/2015; 6(11). DOI:10.1371/journal.pone.0112021 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Physiological studies involving the use of isotopic water required chemical restraint of free-ranging walruses (Odobenus rosmarus) for several hours. In August 2000, six male walrus (total body mass: 1050–1550 kg) were immobilized in East Greenland by remote delivery of 8.0–9.8 mg of etorphine and subsequently restrained for up to 6.75 h by administration of medetomidine. The effects of etorphine were reversed with 10–24 mg diprenorphine. After termination of the etorphine-induced apnoea, lasting an average of 15.8 min (SD = 9.7, range = 9.5–35.2 min, n = 6), the animals were initially given 10–20 mg medetomidine intramuscularly. The initial dose was further augmented by 5 mg at intervals of 5 min. In two cases, when medetomidine was administered through a catheter inserted in the extradural vein, the animal became instantly apnoeic and regained respiratory function only after intravenous injection of the prescribed dose of the antagonist atipamezole and of the respiratory stimulant doxapram. After an average of 3.5 hours of immobilisation, rectal temperature began to increase and it is conceivable that this is the factor that will ultimately limit the duration of immobilisation. The animals became conscious and fully mobile shortly after an intravenous injection of a dose of atipamezole approximately twice the mass of the total dose of medetomidine given during the procedure followed by 400 mg of doxapram. It is concluded that medetomidine appears to be a suitable drug for chemical restraint of walruses for time-consuming procedures following initial immobilisation by etorphine. With animals of total body mass around 1,000–1,500 kg, the drug should be given intramuscularly in 10–20 mg increments (total mass 10–60 mg) until the breathing rate falls to approximately 1 min -1 . At this level, breathing is maintained and animals do not respond to touch or injection.
Walrus of the North Atlantic, Edited by Rob E.A. Stewart, Kit M. Kovacs, Mario Acquarone, 08/2014; NAMMCO - The North Atlantic Marine Mammal Commission.
[Show abstract][Hide abstract] ABSTRACT: To date no problem-free method exists for the immobilisation of free‑ranging walruses (Odobenus rosmarus). In the period 1989-2001, 69 immobilisations with etorphine HCl were performed by remote darting of 41 individual free-ranging adult Atlantic walruses (O. r. rosmarus), with body masses 633 ‑ 1883 kg, as a rerequisite for the attachment of radio tracking and dive recording instruments, and for studies of metabolism. Ten individuals were immobilised several times. We present data on these 69 immobilisations and evaluate the method. Full immobilisation was achieved in 58 cases (84 %). The animals were insufficiently restrained in 6 cases (9 %) and 5 animals died (7 %) following the immobilisation. The animals were fully immobilised and approachable after 5 min (n = 38, range = 1.9 ‑ 12.4 min, SD = 2.2) with a dose of etorphine of 6.1 μg/kg (range 2.4 ‑ 12.6 μg /kg, SD = 2.4). Induction time was negatively correlated with the dosage of etorphine. Etorphine-induced apnoea lasted 13.7 min (n = 36, range 17.0 ‑ 26.7 min, SD = 5.1) and was reversed by multiple doses of the antagonist diprenorphine HCl. The first dose of antagonist of 12.2 mg (n = 39, range 6.0 ‑ 21.0 mg, SD = 3.5) was administered 8.4 min (n = 38, range 4.7 ‑ 18.0 min, SD = 2.8) after injection of the agonist. The total dose of diprenorphine per animal ranged between 7.7 and 41.7 μg/kg (n = 31, mean = 17.2 μg/kg, SD = 7.5). For some animals blood pH values were measured following the apnoea and reached low levels (min pH 6.8). For animals that were immobilised several times there were no indications of changed sensitivity to etorphine as reflected in unchanged induction times. Mortalities could neither be related to the doses of agonist and antagonist, nor to the times of administration of the drugs. From this (n = 69) and other (n = 103) studies involving etorphine immobilisation of walruses (both Atlantic and Pacific) the overall success rate is 83 % (8 % casualty rate). We conclude that the combination etorphine‑ diprenorphine is suitable for both single and multiple immobilisations of walruses provided that (a) a casualty rate of 7-8% is acceptable (b) the antagonist diprenorphine is administered fast and well into a tissue with good blood irrigation, and (c) the animal is promptly intubated endotracheally to facilitate the restoration of breathing after drug-induced apnoea.
[Show abstract][Hide abstract] ABSTRACT: 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. PAPERCLIP:
[Show abstract][Hide abstract] ABSTRACT: Between 2005 and 2008, 31 walruses were tagged with Argos satellite transmitters at their
wintering grounds at Store Hellefiske Banke, Central West Greenland (N=23), and at their
summering grounds off the coast of Southeast Baffin Island, Canada (N=8). Two male
walruses moved along the Greenland coast from Store Hellefiske Banke north to Disko
Banke, where contact was lost. Two other males went further north, up to the Upernavik
area. Contact was lost with one of these tags, but the other animal travelled southward again
and went towards SE Baffin Island. Eight of the tagged walruses moved between West
Greenland and Baffin Island, demonstrating a connection between walruses at these sites.
Walruses left the Store Hellefiske Banke during the period 7 April to 17 May and on
average used 7 days to swim the 400 km across Davis Strait. The migration routes were
quite similar; they travelled over the shallowest areas at the narrowest part of the strait. The
timing of the spring dispersal and migration towards Canada was closely linked to the
extent and timing of the retreat of the pack ice edge. One flipper tagged male that was
marked off South Baffin Island was recovered in a hunt on Store Hellefiske Banke,
documenting that the reverse migration also occurs. Off West Greenland satellite tagged
walruses spent a lot of time around the Store Hellefiske Banke (55.0o-56.5o W), using this
shallow area as feeding grounds irrespective of the ice cover in this area. Partial sexual
segregation was observed. Despite a tendency in West Greenland for males to occur farther
offshore, farther from the ice edge and at greater depths, only their preference for denser ice
cover (64% ice cover) differed significantly (P=0.019) from the habitat preferences of
females (52% ice cover). Coast dispersal was more condensed and the segregation between
males and females was more pronounced during autumn along the Southeast Baffin Island.
Females remained farther north (P<0.001) and farther east (P=0.006), and males were more
often located offshore in areas with greater water depths (P=0.024). Males had also had
larger home range than females during both seasons.
[Show abstract][Hide abstract] ABSTRACT: Rapid climate changes are occurring in the Arctic, with substantial repercussions for arctic ecosystems. It is challenging to assess ecosystem changes in remote polar environments, but one successful approach has entailed monitoring the diets of upper trophic level consumers. Quantitative fatty acid signature analysis (QFASA) and fatty acid carbon isotope (δ(13) C-FA) patterns were used to assess diets of East Greenland (EG) polar bears (Ursus maritimus) (n = 310) over the past three decades. QFASA-generated diet estimates indicated that, on average, EG bears mainly consumed arctic ringed seals (47.5 ± 2.1%) and migratory subarctic harp (30.6 ± 1.5%) and hooded (16.7 ± 1.3%) seals and rarely, if ever, consumed bearded seals, narwhals or walruses. Ringed seal consumption declined by 14%/decade over 28 years (90.1 ± 2.5% in 1984 to 33.9 ± 11.1% in 2011). Hooded seal consumption increased by 9.5%/decade (0.0 ± 0.0% in 1984 to 25.9 ± 9.1% in 2011). This increase may include harp seal, since hooded and harp seal FA signatures were not as well differentiated relative to other prey species. Declining δ(13) C-FA ratios supported shifts from more nearshore/benthic/ice-associated prey to more offshore/pelagic/open-water-associated prey, consistent with diet estimates. Increased hooded seal and decreased ringed seal consumption occurred during years when the North Atlantic Oscillation (NAO) was lower. Thus, periods with warmer temperatures and less sea ice were associated with more subarctic and less arctic seal species consumption. These changes in the relative abundance, accessibility, or distribution of arctic and subarctic marine mammals may have health consequences for EG polar bears. For example, the diet change resulted in consistently slower temporal declines in adipose levels of legacy persistent organic pollutants, as the subarctic seals have higher contaminant burdens than arctic seals. Overall, considerable changes are occurring in the East Greenland marine ecosystem, with consequences for contaminant dynamics. This article is protected by copyright. All rights reserved.
Global Change Biology 05/2013; 19(8). DOI:10.1111/gcb.12241 · 8.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Intraspecific differences in movement behaviour reflect different tactics used by individuals or sexes to favour strategies that maximize fitness. We report movement data collected from n = 23 adult male polar bears with novel ear-attached transmitters in two separate pack ice subpopulations over five breeding seasons. We compared movements with n = 26 concurrently tagged adult females, and analysed velocities, movement tortuosity, range sizes and habitat selection with respect to sex, reproductive status and body mass. There were no differences in 4-day displacements or sea ice habitat selection for sex or population. By contrast, adult females in all years and both populations had significantly more linear movements and significantly larger breeding range sizes than males. We hypothesized that differences were related to encounter rates, and used observed movement metrics to parametrize a simulation model of male-male and male-female encounter. The simulation showed that the more tortuous movement of males leads to significantly longer times to male-male encounter, while having little impact on male-female encounter. By contrast, linear movements of females are consistent with a prioritized search for sparsely distributed prey. These results suggest a possible mechanism for explaining the smaller breeding range sizes of some solitary male carnivores compared to females.
Proceedings of the Royal Society B: Biological Sciences 02/2013; 280(1752):20122371. DOI:10.1098/rspb.2012.2371 · 5.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This review critically evaluates the available mercury (Hg) data in Arctic marine biota and the Inuit population against toxicity threshold values. In particular marine top predators exhibit concentrations of mercury in their tissues and organs that are believed to exceed thresholds for biological effects. Species whose concentrations exceed threshold values include the polar bears (Ursus maritimus), beluga whale (Delphinapterus leucas), pilot whale (Globicephala melas), hooded seal (Cystophora cristata), a few seabird species, and landlocked Arctic char (Salvelinus alpinus). Toothed whales appear to be one of the most vulnerable groups, with high concentrations of mercury recorded in brain tissue with associated signs of neurochemical effects. Evidence of increasing concentrations in mercury in some biota in Arctic Canada and Greenland is therefore a concern with respect to ecosystem health.
Science of The Total Environment 12/2012; 443C:775-790. DOI:10.1016/j.scitotenv.2012.11.046 · 4.10 Impact Factor