Polar Bears Ursus Maritimus Research Articles

Further studies on the morphology of Baylisascaris transfuga (Rudolphi, 1819) (Nematoda: Ascaridomorpha: Ascarididae) from the polar bear Ursus maritimus Phipps (Carnivora: Ursidae).

Baylisascaris transfuga (Rudolphi, 1819) is a common parasitic nematode in the digestive tract of various species of bears worldwide, with great veterinary significance. However, our present knowledge on the morphology of B. transfuga remains insufficient. In the present study, the detailed morphology of B. transfuga was studied using light and scanning electron microscopy (SEM), based on specimens collected from the polar bear Ursus maritimus Phipps (Carnivora: Ursidae) in the Shijiazhuang Zoo, China. The results revealed some morphological and morphometric variation between the present specimens and some of those from previous studies, including oesophageal length of female, number and morphology of postcloacal papillae and morphology of tail of males. Present SEM observations clearly showed the detailed morphology of lips, cervical alae, cloacal ornamentation, precloacal medioventral papilla, phasmids and tail tip. These supplementary morphological and morphometric data enable us to identify this ascaridid nematode more accurately.

Lactation performance in polar bears is associated with fasting time and energetic state

Females must continually make resource allocation decisions because of fitness trade-offs between self-maintenance and investment in current offspring, yet factors underpinning these decisions are unresolved. Polar bears Ursus maritimus face considerable allocation challenges when seasonal sea-ice melt precludes access to prey for several months, and females rely solely on energy stores to cover their own energetic needs and provision offspring. We tested how female polar bears regulate lactation during onshore fasting (i.e. capital breeding) and determined the consequences of moderated lactation for females and cubs. Overall, milk energy declined, and lactation was more likely to cease with longer time fasting. Lactation was partially mediated by maternal energetic state and depended on litter characteristics. Milk energy declined more sharply with fasting time (~2.6 times more strongly) in females with 2 offspring compared to those with 1. Females with cubs-of-the-year produced higher energy milk than those with yearlings, and their milk energy also increased more strongly with maternal energy density. Milk energy declines benefited females via reduced depletion of maternal energy reserves, but cub growth decreased. Altered lactation investment likely has consequences for both female survival and the fate of offspring, which could scale up to influence population dynamics. Given that Arctic warming means polar bears across much of their range will experience longer periods without access to primary prey, our results underscore how lactation will likely become increasingly compromised.

Differential expression of myosin heavy chain isoforms type II in skeletal muscles of polar and black bears.

In this study, the pattern of myosin heavy chain (MHC) isoforms expression in skeletal muscles of the trunk, forelimb and hindlimb in Polar Bear (PB) Ursus maritimus; American Black Bear (AmBB), Ursus americanus and Asian Black Bear (AsBB), Ursus thibetanus was analysed by immunohistochemistry and SDS-PAGE. Results showed that slow (MHC-I) and fast (MHC-II) isoforms exist in muscles of bears. Type II fibres were classified further into Type IIa and IIx in PB but not in AsBB and AmBB. The distribution of Type I and Type II fibres in the trunk, forelimb and hindlimb varied based on muscle type and animal species. The proportions of Type I fibres formed approximately one-third of muscle composition in PB (trunk, 32.0%; forelimb, 34.7%; hindlimb, 34.5%) and a half in both AsBB and AmBB whereas Type IIa and IIx formed approximately two-third in PB (trunk, 68.0%; forelimb, 65.3%; hindlimb, 65.5%) and a half of Type II in both AmBB and AsBB. PB is a good swimmer, lives in Arctic Ocean on slippery ice catching aquatic mammals such as seals and is larger in size compared to the medium sized AmBB (living in forest) and AsBB (arboreal). The results suggest that in bears, there is greater diversity in MHC isoforms II, being expressed in selected fast contracting skeletal muscles in response to variety of environments, weight bearing and locomotion.

Anthropogenic food: an emerging threat to polar bears

AbstractSupplemental food from anthropogenic sources is a source of conflict with humans for many wildlife species. Food-seeking behaviours by black bears Ursus americanus and brown bears Ursus arctos can lead to property damage, human injury and mortality of the offending bears. Such conflicts are a well-known conservation management issue wherever people live in bear habitats. In contrast, the use of anthropogenic foods by the polar bear Ursus maritimus is less common historically but is a growing conservation and management issue across the Arctic. Here we present six case studies that illustrate how negative food-related interactions between humans and polar bears can become either chronic or ephemeral and unpredictable. Our examination suggests that attractants are an increasing problem, exacerbated by climate change-driven sea-ice losses that cause increased use of terrestrial habitats by bears. Growing human populations and increased human visitation increase the likelihood of human–polar bear conflict. Efforts to reduce food conditioning in polar bears include attractant management, proactive planning and adequate resources for northern communities to reduce conflicts and improve human safety. Permanent removal of unsecured sources of nutrition, to reduce food conditioning, should begin immediately at the local level as this will help to reduce polar bear mortality.

Serosurvey of Selected Zoonotic Pathogens in Polar Bears (Ursus maritimus Phipps, 1774) in the Russian Arctic

Antibodies to several pathogens were detected in the serum samples of nine polar bears (Ursus maritimus, Phipps, 1774) from areas of the Russian Arctic. Plasma was studied for antibodies to sixteen infectious and parasitic diseases using indirect Protein-A ELISA. It is known that when using ELISA, the interaction of antibodies with a heterologous antigen is possible due to immunological crossings between antigens. We investigated the plasma for the presence of antibodies to the major pathogens and for the presence of antibodies to pathogens, for which the cross-immunological reactions to these pathogens are described. For example, antibodies to the pathogens of opisthorchiasis, clonorchiasis, and ascariasis were found simultaneously in four polar bears. Antibodies to both anisakidosis and trichinellosis pathogens were found in six animals. The data obtained may also indicate a joint invasion by these pathogens. Unfortunately, due to the small number of animals sampled, it is impossible to carry out statistical processing of the data.

Energy‐based step selection analysis: Modelling the energetic drivers of animal movement and habitat use

The energetic gains from foraging and costs of movement are expected to be key drivers of animal decision-making, as their balance is a large determinant of body condition and survival. This fundamental perspective is often missing from habitat selection studies, which mainly describe correlations between space use and environmental features, rather than the mechanisms behind these correlations. To address this gap, we present a novel parameterisation of step selection functions (SSFs), that we term the energy selection function (ESF). In this model, the likelihood of an animal selecting a movement step depends directly on the corresponding energetic gains and costs, and we can therefore assess how moving animals choose habitat based on energetic considerations. The ESF retains the mathematical convenience and practicality of other SSFs and can be quickly fitted using standard software. In this article, we outline a workflow, from data gathering to statistical analysis, and use a case study of polar bears Ursus maritimus to demonstrate application of the model. We explain how defining gains and costs at the scale of the movement step allows us to include information about resource distribution, landscape resistance and movement patterns. We further demonstrate this process with a case study of polar bears and show how the parameters can be interpreted in terms of selection for energetic gains and against energetic costs. The ESF is a flexible framework that combines the energetic consequences of both movement and resource selection, thus incorporating a key mechanism into habitat selection analysis. Further, because it is based on familiar habitat selection models, the ESF is widely applicable to any study system where energetic gains and costs can be derived, and has immense potential for methodological extensions.

Bear diets and human–bear conflicts: insights from isotopic ecology

AbstractBears, Ursidae, are considered omnivores, except for giant pandas Ailuropoda melanoleuca and polar bears Ursus maritimus. However, omnivory includes a wide range of dietary variation and trophic positions, making bear dietary ecology unclear. We inferred bear trophic positions from δ15N (‰) values and examined their correlation with diets reported in the literature, including frequency of human–bear conflicts (livestock predation and crop damage incidents). Overall, 15N signatures were consistent with diet estimates. Bear species with higher 15N signatures differed more from each other, including cases of large regional intraspecific variance, than bear species with lower 15N signatures. Bear trophic position and frequency of reports of human–bear conflicts were uncorrelated, suggesting that livestock predation by bears is an opportunistic behaviour rather than a response to food availability dynamics.

Fecal DNA metabarcoding shows credible short-term prey detections and explains variation in the gut microbiome of two polar bear subpopulations

This study developed and evaluated DNA metabarcoding to identify the presence of pinniped and cetacean prey DNA in fecal samples of East Greenland (EG) and Southern Beaufort Sea (SB) polar bearsUrsus maritimussampled in the spring of 2015-2019. Prey DNA was detected in half (49/92) of all samples, and when detected, ringed sealPusa hispidawas the predominant prey species, identified in 100% (22/22) of EG and 81% (22/27) of SB polar bear samples with prey DNA detected. Bearded sealErignathus barbatusDNA was found in 19% (5/27) of SB polar bear samples for which prey DNA was detected. Prey DNA detection frequencies and relative abundances were compared to estimates from quantitative fatty acid signature analysis (QFASA) for a subset of SB polar bears. Ringed seal and bearded seal were the main prey identified by both methods, but QFASA also identified 2 cetacean prey species not found by prey DNA. Differences in DNA metabarcoding vs. QFASA results were likely related to the different dietary timescales captured by each approach, i.e. short-term vs. long-term diet, respectively. Prey DNA detection, sex/age class, and subpopulation significantly explained variation in polar bear gut bacterial composition. Polar bear samples with prey DNA detected were associated with higher abundances of the bacterial classes Clostridia and Bacilli and lower abundances of Negativicutes. Fecal DNA metabarcoding is thus useful for identifying recent prey of polar bears, complementing quantitative and likely longer-term QFASA estimates, and may help understand variation in the polar bear gut microbiome.

Classifying the effects of human disturbance on denning polar bears

Climate change is resulting in decreased sea ice extent and increased industrial activity in Arctic regions. In northern Alaska, USA, sea ice loss has increased the frequency of land-based polar bearUrsus maritimusmaternal dens, leading to greater potential for overlap between industrial activities and denning bears. Responses of denning bears to human disturbance could result in costly reproductive outcomes, although observation of these responses is logistically challenging and expensive. We developed a method to standardize the process of classifying the response of denning polar bears to disturbance using decision rules based on polar bear biology and denning chronology. We applied this method to 46 maternal polar bear dens exposed to human activity (e.g. vehicle traffic, ground-based monitoring). Because the timing of disturbance influences the response and subsequent fitness consequences, we determined outcomes specific to 4 denning periods: (1) den establishment (excavation to cub birth); (2) early denning (cub birth to 60 d old); (3) late denning (60 d old to emergence); and (4) post-emergence (emergence to den site departure). We classified the outcomes of 79 exposures as 37 having ‘no documented effect’ (no observed response), 7 as ‘behavioral’ (observed behavioral disruption), 17 as ‘early emergence’ (den emergence occurring earlier than an undisturbed emergence), 14 as ‘early departure’ (den site abandonment post-emergence earlier than if undisturbed), and 4 as ‘cub mortality’ (death or abandonment of ≥1 cub). Outcomes with potential fitness consequences occurred in every denning period. Our classification method facilitated a standardized approach that can be used to classify the outcome of den disturbance. Determining outcomes in relation to a specific denning period may facilitate improved implementation of mitigation strategies to reduce disturbance to denning bears.

Microstructure, elemental composition and mechanical properties of enamel and dentine in the polar bear Ursus maritimus

ObjectiveTo investigate the microstructure, elemental composition and mechanical properties of polar bear teeth. DesignIncisors, canines and fourth premolar teeth of two subadult male museum specimens were analysed. Teeth were measured, photographed, embedded in Epoxy resin, sectioned, polished and etched for scanning electron microscope (SEM) imaging, elemental composition and nanomechanical testing analyses. ResultsThe thickness of enamel ranged from 350-430 µm in canines, 220–330 µm in incisors and 320–510 µm in premolars. SEM images showed distinct transversely-oriented undulating Hunter Schreger bands from the enamel-dentine junction (EDJ) to the outer enamel surface. Enamel prisms had a hexagonal shape, with open prism sheaths. Prisms measured 6–8 µm in diameter. The EDJ was straight with no evidence of scalloping. Larger tubules adjacent to the EDJ were observed in the mantle dentine zone. Enamel Hardness and Elastic modulus values were higher in premolars (6.9 GPa and 269 GPa), followed by canines (6.5 GPa and 230 GPa) and incisors (4.9 GPa and 187 GPa). Dentine Hardness and Elastic modulus values were higher in canines. CaO and P2O5 were the components with higher oxide weight percentage in both enamel and dentine. ConclusionsUnderstanding the microstructure, elemental composition and mechanical properties of polar bear teeth can help elucidate the biology and functional morphology of this globally threatened species and could be used as a proxy for studies with fossil ursids.

Feeding habits of Baffin Bay polar bears Ursus maritimus: insight from stable isotopes and total mercury in hair

Loss of sea ice brought on by climate change affects polar bear Ursus maritimus access to prey. Here we investigated variation in feeding habits of the Baffin Bay (BB) polar bear subpopulation in relation to sea ice, habitat use, season, and demography using hair carbon (δ13C), nitrogen (δ15N), and sulfur (δ34S) stable isotope values and total mercury (THg) concentrations as ecological tracers. We analyzed hair samples from BB polar bears (n = 131) of all age and sex classes live-captured in West Greenland during the spring in 2009-2013. BB polar bears occupied a narrow isotopic space, suggesting limited variation in carbon sources and trophic position within the subpopulation. THg concentrations (median ± SE: 5.1 ± 0.2, range: 0.3-12.5 µg g-1 dry weight, DW) were related to age class, and nearly half exceeded the suggested threshold for neurological effects in polar bears at 5.4 µg g-1 DW. Although distinct coastal and offshore space-use strategies have been reported for BB polar bears, our results suggest that both strategies lead to similar carbon sources and trophic positions. We found seasonal variation in δ13C and δ34S across both space-use strategies, with δ34S suggesting that all BB polar bears may prey on a higher proportion of benthic-feeding bearded seals Erignathus barbatus in late summer relative to spring. Despite wide fluctuations in inter-annual sea ice conditions and differences in space-use strategies among individuals, stable isotope values and THg concentrations suggested limited variation in feeding habits among BB polar bears. The variation of habitat tracers (δ13C and δ34S) was related to season, whereas trophic tracer (δ15N and THg) variation was driven by demographic group. The specialized BB polar bear diet suggests limited feeding plasticity under continued climate warming.

Demographic risk assessment for a harvested species threatened by climate change: polar bears in the Chukchi Sea.

Climate change threatens global biodiversity. Many species vulnerable to climate change are important to humans for nutritional, cultural, and economic reasons. Polar bears Ursus maritimus are threatened by sea‐ice loss and represent a subsistence resource for Indigenous people. We applied a novel population modeling‐management framework that is based on species life history and accounts for habitat loss to evaluate subsistence harvest for the Chukchi Sea (CS) polar bear subpopulation. Harvest strategies followed a state‐dependent approach under which new data were used to update the harvest on a predetermined management interval. We found that a harvest strategy with a starting total harvest rate of 2.7% (˜85 bears/yr at current abundance), a 2:1 male‐to‐female ratio, and a 10‐yr management interval would likely maintain subpopulation abundance above maximum net productivity level for the next 35 yr (approximately three polar bear generations), our primary criterion for sustainability. Plausible bounds on starting total harvest rate were 1.7–3.9%, where the range reflects uncertainty due to sampling variation, environmental variation, model selection, and differing levels of risk tolerance. The risk of undesired demographic outcomes (e.g., overharvest) was positively related to harvest rate, management interval, and projected declines in environmental carrying capacity; and negatively related to precision in population data. Results reflect several lines of evidence that the CS subpopulation has been productive in recent years, although it is uncertain how long this will last as sea‐ice loss continues. Our methods provide a template for balancing trade‐offs among protection, use, research investment, and other factors. Demographic risk assessment and state‐dependent management will become increasingly important for harvested species, like polar bears, that exhibit spatiotemporal variation in their response to climate change.

Incorporating climate change in a harvest risk assessment for polar bears Ursus maritimus in Southern Hudson Bay

Arctic marine mammals are harvested by Indigenous people for subsistence and are socially and culturally important. For ice-dependent species like the polar bear Ursus maritimus, management and conservation require understanding interactions between harvest and sea-ice loss due to climate change. We developed a demographic model to evaluate harvest risk for polar bears in Southern Hudson Bay, Canada, where the annual ice-free season has increased by approximately one month in recent decades. The model was based on the theta-logistic equation and allowed for density-dependent changes (through carrying capacity [K]) and density-independent changes (through population growth rate [r]). Model parameters were estimated using a Bayesian Monte Carlo method that included capture-recapture, aerial survey, and harvest data. Harvest management followed a state-dependent approach under which new estimates of abundance were used to update the harvest level every five years. Under a middle-of-the-road environmental scenario that assumed K and r would decline in proportion to projected sea-ice declines, annual removal of 0.02–0.03 of females resulted in a 0.8 probability of maintaining subpopulation abundance above maximum net productivity level for three polar bear generations (~34 years), our primary criterion for sustainability. Under more pessimistic and optimistic environmental scenarios, comparable female harvest rates were 0.01 and 0.055, respectively. Our coupled modeling-management framework can be used to inform tradeoffs between protection and sustainable use for wildlife populations experiencing habitat loss.

Effects of sea ice fragmentation on polar bear migratory movement in Hudson Bay

Habitat fragmentation can impede an animal’s ability to move through their habitat, affecting both local and long-distance movements. Each year, polar bears Ursus maritimus migrate to refuge habitats on land or to multiyear ice as annual sea ice breaks up. We used polar bear telemetry location data from 39 adult female polar bears tracked in Hudson Bay in 2013-2018 during break-up (2 May-23 July) to show variation in migratory movement and timing as break-up advances. We separated break-up into early and late periods and used standard deviation in temporal spatial autocorrelation (SASD) of sea ice concentration to quantify sea ice fragmentation. Higher spatial autocorrelation reflects dissimilarity in local habitat composition at a single point in time, while SASD reflects variation in local habitat composition over time. In late break-up, there was a significant positive correlation between polar bear path tortuosity and SASD. Individuals arrived on land significantly later when paths moved through sea ice with increasing SASD in late break-up. Reproductive status of adult female polar bears had no effect on the variability of the sea ice an individual travelled through. SASD provides a means of summarizing the complexity and dynamics of sea ice habitat and can be used to understand variation in movement and ecology of ice-associated organisms.

Polar bear Ursus maritimus use of the western Hudson Bay flaw lead

Flaw leads (FLs) and polynyas are recurrent areas of open water within sea ice that provide habitat for a diversity of Arctic species. The western Hudson Bay FL is a major, predictable habitat feature; however, its importance to polar bears Ursus maritimus has not been examined. We mapped the FL using synthetic aperture radar (resolution 62.3 × 121 m) from December to May, 2009-2018, and assessed FL use by 73 adult female polar bears tracked using satellite telemetry. Maximum FL width varied from 4 km in March to 145 km in May. Bears were closest to the FL in May, which coincided with their hyperphagic period and the seal pupping season. Only 31.5% (n = 23) of the bears used the FL, and they travelled faster, with lower turning angles along the FL (16° turns at 101° and -69° relative to the FL), suggesting the feature acted as a corridor that could increase prey encounters. Bears were closer to and crossed sections of the FL that were 68% narrower than those not crossed, indicating that a wider FL deters crossing. Abundant prey likely attracts some bears to the FL, but most bears avoid the FL between hunts, likely to conserve energy on consolidated ice or to reduce intraspecific interactions. Increases in open water resulting from climate warming might make the FL more challenging for bears to cross, but could make it more attractive if open-water prey densities increase.

Marine mammal hotspots in the Greenland and Barents Seas

Environmental change and increasing levels of human activity are threats to marine mammals in the Arctic. Identifying marine mammal hotspots and areas of high species richness are essential to help guide management and conservation efforts. Herein, space use based on biotelemetric tracking devices deployed on 13 species (ringed sealPusa hispida, bearded sealErignathus barbatus, harbour sealPhoca vitulina, walrusOdobenus rosmarus, harp sealPagophilus groenlandicus, hooded sealCystophora cristata, polar bearUrsus maritimus, bowhead whaleBalaena mysticetus, narwhalMonodon monoceros, white whaleDelphinapterus leucas, blue whaleBalaenoptera musculus, fin whaleBalaenoptera physalusand humpback whaleMegaptera novaeangliae; total = 585 individuals) in the Greenland and northern Barents Seas between 2005 and 2018 is reported. Getis-OrdGi* hotspots were calculated for each species as well as all species combined, and areas of high species richness were identified for summer/autumn (Jun-Dec), winter/spring (Jan-May) and the entire year. The marginal ice zone (MIZ) of the Greenland Sea and northern Barents Sea, the waters surrounding the Svalbard Archipelago and a few Northeast Greenland coastal sites were identified as key marine mammal hotspots and areas of high species richness in this region. Individual hotspots identified areas important for most of the tagged animals, such as common resting, nursing, moulting and foraging areas. Location hotspots identified areas heavily used by segments of the tagged populations, including denning areas for polar bears and foraging areas. The hotspots identified herein are also important habitats for seabirds and fishes, and thus conservation and management measures targeting these regions would benefit multiple groups of Arctic animals.

A novel mark-recapture-recovery survey using genetic sampling for polar bears Ursus maritimus in Baffin Bay

Changes in sea-ice dynamics are affecting polar bears Ursus maritimus across their circumpolar range, which highlights the importance of periodic demographic assessments to inform management and conservation. We used genetic mark-recapture-recovery to derive estimates of abundance and survival for the Baffin Bay (BB) polar bear subpopulation—the first time this method has been used successfully for this species. Genetic data from tissue samples we collected via biopsy darting were combined with historical physical capture and harvest recovery data. The combined data set consisted of 1410 genetic samples (2011-2013), 914 physical captures (1993-1995, 1997), and 234 harvest returns of marked bears (1993-2013). The estimate of mean subpopulation abundance was 2826 (95% CI = 2284-3367) in 2012-2013. Estimates of annual survival (mean ± SE) were 0.90 ± 0.05 and 0.78 ± 0.06 for females and males age ≥2 yr, respectively. The proportion of total mortality of adult females and males that was attributed to legal harvest was 0.16 ± 0.05 and 0.26 ± 0.06, respectively. Remote sensing sea-ice data, telemetry data, and spatial distribution of onshore sampling indicated that polar bears were more likely to use offshore sea-ice habitat during the 1990s sampling period compared to the 2010s. Furthermore, in the 1990s, sampling of deep fjords and inland areas was limited, and no offshore sampling occurred in either time period, which precluded comparisons of abundance between the 1993-1997 and 2011-2013 study periods. Our findings demonstrate that genetic sampling can be a practical method for demographic assessment of polar bears over large spatial and temporal scales.

Hunters versus hunted: New perspectives on the energetic costs of survival at the top of the food chain

Abstract Global biotic and abiotic threats, particularly from pervasive human activities, are progressively pushing large, apex carnivorous mammals into the functional role of mesopredator. Hunters are now becoming the hunted. Despite marked impacts on these animals and the ecosystems in which they live, little is known about the physiological repercussions of this role downgrading from ultimate to penultimate predator. Here we examine how such ecological role reversals alter the physiological processes associated with energy expenditure, and ultimately the cost of survival during peak performance. Taxonomic group, preferred habitat and domestication affected the capacity of the oxygen pathway to support high levels of aerobic performance by carnivorous mammals. Fear responses associated with anthropogenic threats also impacted aerobic performance. Allometric trends for three energetic metrics [maximum oxygen consumption, field metabolic rates (FMRs) and the cost per stride or stroke], showed distinct trends in aerobic capacity for different evolutionary lineages of mammalian predators. Cursorial canids that chase down prey demonstrated the highest relative maximum oxygen consumption rates (10–25 times resting levels) and FMRs, while ambush predators (i.e. felids) and diving marine mammals had aerobic capacities that were similar to or lower than sedentary domestic mammals of comparable size. The maximum energetic cost of performance for apex predators depended on whether the animals were hunters or the hunted. Escape responses were exceptionally costly for marine (narwhal Monodon monoceros) and terrestrial (mountain lion Puma concolor) locomotor specialists, as well as semi‐aquatic (polar bear Ursus maritimus) species; all showed a nearly two‐fold increase in peak energy expenditure when avoiding threats. As the duration and frequency of threats to wild species continue to grow, cumulative energetic costs are becoming more apparent. In view of this, attention to the energy demands of apex predators will provide vital predictive power to anticipate mismatches between a species' functional design and human‐induced pressures, and allow for the development of conservation strategies based on how species are built to survive. A free Plain Language Summary can be found within the Supporting Information of this article.

Bird and Mammal at-sea Distribution Along the North-East Passage off Siberia

Quantitative seabird and marine mammal at-sea distribution was determined along the North-East Passage, off Siberia, in August 2017. A total of 18,400 seabirds were tallied during 340 transect counts, belonging to 31 species. Some bird species were numerically dominant: fulmar Fulmarus glacialis, Brünnich’s guillemot Uria lomvia, shorttailed shearwater Puffinus tenuirostris and crested auklet Aethia cristatellea representing more than 90 % of the total. Humpback Megaptera novaeangliae and bowhead whales Balaena mysticetus formed the bulk of the 100 large whales, as well as 40 white-beaked dolphins Lagenorhynchus albirostris, concentrated in a major hotspot. Two species represented 97 % of the 910 identified pinnipeds: harp seal Phoca goenlandica and walrus Odobenus rosmarus. Polar bear Ursus maritimus was detected as 75 individuals, while more than 3,500 were noted on Wrangel Island, out of effort. The major factors affecting top predators’ quantitative distribution were the geographic differences between seas, and the importance of a major hotspot for humpback whales and harp seals.

Patterns of sea ice drift and polar bear (Ursus maritimus) movement in Hudson Bay

Sea ice habitats are highly dynamic, and ice drift may affect the energy expenditure of travelling animals. Several studies in the high Arctic have reported increased ice drift speeds, and consequently, polar bears Ursus maritimus in these areas expended more energy on counter-ice movement for station-keeping. However, little is known about the spatiotemporal dynamics of ice drift in Hudson Bay (HB) and its implications for the declining Western Hudson Bay (WH) polar bear subpopulation. Using sea ice drift data from 1987-2015 and polar bear satellite telemetry location data from 2004-2015, we examined trends in drift speeds in HB, polar bear movement relative to drift, and assessed annual and individual variation. In contrast to other areas of the Arctic, we did not find an increase in ice drift speed over the period examined. However, variability in ice drift speed increased over time, which suggests reduced habitat predictability. Polar bear movement direction was not strongly counter to ice drift in any month, and ice drift speed and direction had little effect on bear movement rates and, thus, energy expenditure. On an annual scale, we found individuals varied in their exposure and response to ice drift, which may contribute to variability in body condition. However, the lack of a long-term increase in ice drift speed suggests this is unlikely to be the main factor affecting the body condition decline observed in the WH subpopulation. Our results contrast findings in other subpopulations and demonstrate the need for subpopulation-specific research and risk evaluation.