Migratory responses to climate change may vary across and within populations, particularly for species with large geographic ranges. An increase in the frequency of long‐distance swims (> 50 km) is one predicted consequence of climate change for polar bears Ursus maritimus. We examined GPS satellite‐linked telemetry records of 58 adult females and 18 subadults from the Beaufort Sea (BS), and 59 adult females from Hudson Bay (HB), for evidence of long‐distance swimming during seasonal migrations in 2007–2012. We identified 115 swims across both populations. Median swim duration was 3.4 d (range 1.3–9.3 d) and median swim distance was 92 km (range 51–404 km). Swims were significantly more frequent in the BS (n = 100) than HB (n = 15). In the BS, subadults swam as frequently as lone adult females, but more frequently than adult females with offspring. We modelled the likelihood of a polar bear engaging in swims using collar data from the BS. Swims were more likely for polar bears without offspring, with the distance of the pack ice edge from land, the rate at which the pack ice edge retreated, and the mean daily rate of open water gain between June–August. Coupled with an earlier study, the yearly proportions of BS adult females swimming in 2004–2012 were positively associated with the rate of open water gain. Results corroborate the hypothesis that long‐distance swimming by polar bears is likely to occur more frequently as sea ice conditions change due to climate warming. However, results also suggest that the magnitude of the effect likely varies within and between populations.

Aim It is generally held that the dominant competitors in a population will occupy high‐quality habitat while forcing subordinates into lower‐quality habitats through interference competition. We examined the distribution of a non‐territorial apex carnivore relative to foraging habitat to assess the effect of two types of interference: competitive asymmetries in predatory ability and conspecific predation risk. Location Beaufort Sea, Canada. Methods The quality of foraging habitat was modelled using resource selection functions to relate the locations of seals killed by polar bears (Ursus maritimus) to attributes of the sea ice. We used estimated seal biomass as a sample weight to reflect the energetic return of different sizes of kills. To test the effect of sample weighting, locations at which polar bears were captured were used to compare habitat quality modelled with kills weighted equally and kills weighted by their biomass. The distributions of different demographic classes of polar bears were then compared with the general predictions of unequal‐competitor models. Results Polar bear distribution was correlated with the quality of the foraging habitat as determined by the kill biomass model (rs = 0.90, P = 0.04), but not in the unweighted design (P = 0.75). No difference was detected in use of the highest‐quality foraging habitat by subadults and adults. Females with cubs‐of‐the‐year used lower‐quality foraging habitat relative to the rest of the population. Main conclusions Weighting the habitat model with biologically relevant information improved its fit to species distribution, and suggested that density of use alone was insufficient to define habitat quality. Intraspecific competition had a varying influence on the distribution: unequal competitors coexisted, while the avoidance of conspecific predation risk resulted in semi‐truncation.

The effects of declining Arctic sea ice on local ecosystem productivity are not well understood but have been shown to vary inter-specifically, spatially, and temporally.Because marine mammals occupy upper trophic levels in Arctic food webs, they may be useful indicators for understanding variation in ecosystem productivity. Polar bears (Ursus maritimus) are apex predators that primarily consume benthic and pelagic-feeding ice-associated seals. As such, their productivity integrates sea ice conditions and the ecosystem supporting them. Declining sea ice availability has been linked to negative population effects for polar bears but does not fully explain observed population changes. We examined relationships between spring foraging success of polar bears and sea ice conditions, prey productivity, and general patterns of ecosystem productivity in the Beaufort and Chukchi Seas (CSs). Fasting status (≥7 days) was estimated using serum urea and creatinine levels of 1,448 samples collected from 1,177 adult and subadult bears across three subpopulations. Fasting increased in the Beaufort Sea between 1983-1999 and 2000-2016 and was related to an index of ringed seal body condition.This change was concurrent with declines in body condition of polar bears and observed changes in the diet, condition and/or reproduction of four other vertebrate consumers within the food chain. In contrast, fasting declined in CS polar bears between periods and was less common than in the two Beaufort Sea subpopulations consistent with studies demonstrating higher primary productivity and maintenance or improved body condition in polar bears, ringed seals, and bearded seals despite recent sea ice loss in this region. Consistency between regional and temporal variation in spring polar bear fasting and food web productivity suggests that polar bears may be a useful indicator species. Furthermore, our results suggest that spatial and temporal ecological variation is important in affecting upper trophic-level productivity in these marine ecosystems.

Background Polar bears ( Ursus maritimus ) of the Beaufort Sea enter hyperphagia in spring and gain fat reserves to survive periods of low prey availability. We collected information on seals killed by polar bears ( n = 650) and hunting attempts on ringed seal ( Pusa hispida ) lairs ( n = 1396) observed from a helicopter during polar bear mark-recapture studies in the eastern Beaufort Sea in spring in 1985–2011. We investigated how temporal shifts in ringed seal reproduction affect kill composition and the intraspecific vulnerabilities of ringed seals to polar bear predation. Principal Findings Polar bears primarily preyed on ringed seals (90.2%) while bearded seals ( Erignathus barbatus ) only comprised 9.8% of the kills, but 33% of the biomass. Adults comprised 43.6% (150/344) of the ringed seals killed, while their pups comprised 38.4% (132/344). Juvenile ringed seals were killed at the lowest proportion, comprising 18.0% (62/344) of the ringed seal kills. The proportion of ringed seal pups was highest between 2007–2011, in association with high ringed seal productivity. Half of the adult ringed seal kills were ≥21 years (60/121), and kill rates of adults increased following the peak of parturition. Determination of sex from DNA revealed that polar bears killed adult male and adult female ringed seals equally (0.50, n = 78). The number of hunting attempts at ringed seal subnivean lair sites was positively correlated with the number of pup kills ( r 2 = 0.30, P = 0.04), but was not correlated with the number of adult kills ( P = 0.37). Conclusions/Significance Results are consistent with decadal trends in ringed seal productivity, with low numbers of pups killed by polar bears in spring in years of low pup productivity, and conversely when pup productivity was high. Vulnerability of adult ringed seals to predation increased in relation to reproductive activities and age, but not gender.

Individual variation in habitat selection has emerged as an important component necessary for understanding population ecology. For threatened species, where habitat loss and alteration affect population trends, understanding habitat use provides insight into mechanisms of population change. Polar bears, Ursus maritimus, in the Western Hudson Bay subpopulation have experienced declines in body condition, survival, and abundance associated with delayed freeze‐up and earlier break‐up of sea ice due to climate change. Although this subpopulation has been intensively studied, sea ice habitat selection remains poorly understood. We developed a habitat selection model using a mixed conditional logistic regression to determine habitat selection across seasons (freeze‐up, early winter, late winter, break‐up) and assess individual variation in habitat selection. We used 8487 locations collected between 2004 and 2010 from 64 GPS satellite linked radio‐collars on adult females to compare habitat selected to habitat available. Selection changed across seasons and varied the most among individuals during the freeze‐up and break‐up seasons. During later winter, there was less variation in habitat selection among individuals and bears showed the least amount of selection in habitat use. Distance to the denning area, a core terrestrial refuge habitat, was the top‐ranked covariate in all seasons suggesting site fidelity plays a role in habitat selection. Some individual variation may have been due to reproductive status, though we could not account for this directly. Recognizing individual differences, especially in a rapidly changing environment, allows managers to identify critical habitats instead of simply average resources, and may lead to more successful efforts to protect habitats.

Long-term data on populations, threats, and habitat-use changes are fundamentally important for conservation policy and management decisions affecting species, but these data are often in short supply. Here, we analyze survey data from 57,087 plots collected in approximately three-fourths of the giant panda's (Ailuropoda melanoleuca) distributional range during China's national surveys conducted in 1999-2003 and 2011-2014. Pandas associated preferentially with several ecological factors and avoided areas impacted by human activities, such as roads, livestock, mining, and tourism. Promise is shown by dramatic declines in logging rates, but is counterbalanced with recently emerging threats. Pandas have increasingly utilized secondary forest as these forests recovered under protective measures. Pandas have undergone a distributional shift to higher elevations, despite the elevational stability of their bamboo food source, perhaps in response to a similar upward shift in the distribution of livestock. Our findings showcase robust on-the-ground data from one of the largestscale survey efforts worldwide for an endangered species and highlight how science and policy have contributed to this remarkable success story, and help frame future management strategies. K E Y W O R D Santhropogenic threat, conservation policy, giant panda, habitat use, population distributionThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Ringed seal (Pusa hispida) breeding distribution has been extensively studied across near‐shore habitats, but has received limited attention at a seascape scale due to the difficulty in accessing offshore sea ice environments. Employing highly visible predation attempts by polar bears (Ursus maritimus) on ringed seals in subnivean lairs observed by helicopter, the spatial relationship between predatory behaviour and ringed seal breeding habitat was examined. Resource selection functions were used to determine the relative probability of predation attempts on ringed seals in lairs as a function of habitat during a period of low ringed seal natality (2004–2006). Ringed seal pup kill locations were compared between years of low (2003–2006) and high (2007–2011) natality to assess the effect of reproductive output on habitat use. During years of low natality, polar bear hunting attempts were more likely in near‐shore fast ice, and pup kills were observed predominately in fast ice (fast = 65 %, pack = 29 %, P = 0.002) at a median distance of 36 km from shore. In years of high natality, pup kills were observed farther from shore (median = 46 km, P = 0.03), and there was no difference in the proportion of observations in fast ice and pack ice (fast = 43 %, pack = 52 %, P = 0.29). These results suggest that the facultative use of adjacent offshore pack ice by breeding ringed seals may be influenced by natality. This study illustrates how documenting the behaviour of a predator can facilitate insight into the distribution of a cryptic prey.

The influence of climate change on wildlife disease dynamics is a burgeoning conservation and human health issue, but few long‐term studies empirically link climate to pathogen prevalence. Polar bears (Ursus maritimus) are vulnerable to the negative impacts of sea ice loss as a result of accelerated Arctic warming. While studies have associated changes in polar bear body condition, reproductive output, survival, and abundance to reductions in sea ice, no long‐term studies have documented the impact of climate change on pathogen exposure. We examined 425 serum samples from 381 adult polar bears, collected in western Hudson Bay (WH), Canada, for antibodies to selected pathogens across three time periods: 1986–1989 (n = 157), 1995–1998 (n = 159) and 2015–2017 (n = 109). We ran serological assays for antibodies to seven pathogens: Toxoplasma gondii, Neospora caninum, Trichinella spp., Francisella tularensis, Bordetella bronchiseptica, canine morbillivirus (CDV) and canine parvovirus (CPV). Seroprevalence of zoonotic parasites (T. gondii, Trichinella spp.) and bacterial pathogens (F. tularensis, B. bronchiseptica) increased significantly between 1986–1989 and 1995–1998, ranging from +6.2% to +20.8%, with T. gondii continuing to increase into 2015–2017 (+25.8% overall). Seroprevalence of viral pathogens (CDV, CPV) and N. caninum did not change with time. Toxoplasma gondii seroprevalence was higher following wetter summers, while seroprevalences of Trichinella spp. and B. bronchiseptica were positively correlated with hotter summers. Seroprevalence of antibodies to F. tularensis increased following years polar bears spent more days on land, and polar bears previously captured in human settlements were more likely to be seropositive for Trichinella spp. As the Arctic has warmed due to climate change, zoonotic pathogen exposure in WH polar bears has increased, driven by numerous altered ecosystem pathways.