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Polar bear foraging on common eider eggs: estimating the energetic consequences of a climate-mediated behavioural shift
Abstract
Climate-mediated phenological shifts can cause species to lose access to their primary prey while increasing opportunities for alternative-prey encounters. Species that are able to capitalize on alternative resources could potentially profit from prey-switching should the benefits of procuring these alternative resources outweigh their acquisition costs. Polar bears, Ursus maritimus, use sea ice as a platform to hunt seals, and individuals inhabiting the southern-most extent of their range rely on accumulated fat reserves to sustain themselves during the increasingly lengthy ice-free season. In response to declining access to their primary prey through documented sea ice loss, some polar bears are foraging on the eggs of birds in lieu of hunting opportunities on ice, as their onshore arrival is increasingly overlapping with birds’ breeding schedules. To gain a better understanding of the energetic consequences of this behaviour, we used aerial drones to record polar bears foraging on sea duck eggs (common eider, Somateria mollissima) on Mitivik Island, Nunavut, Canada. Using these data, we examined variation in individual polar bear foraging behaviours and estimated the energetic benefits and costs associated with foraging on common eider eggs. Because of low costs associated with nest searching and consumption, the energetic cost of foraging remained relatively constant throughout the 2-week observation period. However, we found that as the common eider breeding season progressed, polar bears consumed eggs at a lower rate as they depleted the nesting colony and spent proportionally more time searching for nests. Collectively, this foraging pattern led to an overall declining trend in the net energy gained from egg consumption. Foraging on common eider eggs during increasingly lengthy ice-free seasons is apparently beneficial for polar bears, but only during a limited window of opportunity. By coupling energetic estimates with detailed behavioural data collected through aerial videography, this study provides a quantification of both the benefits and costs of egg consumption for polar bears.
... For instance, drones have been used to gain novel insights about the foraging behaviour of many marine species (i.e., gray whales, Eschrichtius robustus (Lilljeborg, 1861), Torres et al. 2018;tiger sharks, Galeocerdo cuvier (Péron and Lesueur in Lesueur, 1822); saltwater crocodiles, Crocodylus porosus Schneider, 1801, Gallagher, Papastamatiou, and Barnett 2018;and white sharks, Carcharodon carcharias (Linnaeus, 1758), Tucker et al. 2021); the courting and mating behaviour of green sea turtles (Chelonia mydas (Linnaeus, 1758), Bevan et al. 2016) and loggerhead sea turtles (Caretta caretta (Linnaeus, 1758), Schofield et al. 2017); the parasitic micro-predation behaviour of kelp gulls (Larus dominicanus Lichtenstein, 1823) on southern right whales (Eubalaena australis (Desmoulins, 1822), Azizeh et al. 2021); and the nursing behaviour of southern right whales with associated bioenergetic costs (Nielsen et al. 2019). In a similar fashion, our research team used DJI Phantom 3 and 4 Pro (multirotor) drones to film polar bears foraging on seabird eggsan increasing phenomenon at our study site (Iverson et al. 2014)and subsequently estimate the energetic consequence of this behaviour (Jagielski et al. 2021a) and examine the foraging performance of bears (Jagielski et al. 2021b). Given our success with using drones to glean important insights into polar bear foraging behaviour, we believe that there is great potential for drones to be used to study other aspects of polar bear behaviour as well. ...
... Multirotor drones have the capacity to hover over bears (Fig. 1A), record their behaviours from above in high-quality format (up to 4K) and reach areas that are inaccessible to researchers, such as in the water (Fig. 1B). In our own experience, this "top-down" vantage point paired with the high-quality video footage capability of modern drones allowed us to discern when bears consumed seabird eggs from a nest, ignored a full clutch, and (or) visited an empty nest (Jagielski et al. 2021a(Jagielski et al. , 2021b. We could also assess bears' use of visual cues to locate nests when they responded to a hen flushing from her nest (Jagielski et al. 2021b). ...
... In response to changing sea-ice conditions, some polar bears (particularly those inhabiting seasonal-ice zones) are increasingly foraging on terrestrial resources (e.g., Gormezano and Rockwell 2013;Iverson et al. 2014;Stempniewicz et al. 2021), although the energetic contribution of most food items, while suspected to be minimal , is still unknown (but see Gormezano and Rockwell 2015). Drones can be used to film polar bears eating, searching for food, and resting to produce daily activity budgets, which can subsequently be used to estimate the energetic consequences of consuming a particular resource to help inform the energetic contribution to polar bears' terrestrial diet (e.g., Jagielski et al. 2021a; also see Subsection 4.2). ...
Climate-induced sea-ice loss represents the greatest threat to polar bears (Ursus maritimus), and utilizing drones to characterize behavioural responses to sea-ice loss is valuable to forecasting polar bear persistence. In this manuscript, we review previously published literature and draw on our own experience of using multirotor aerial drones to study polar bear behaviour in the Canadian Arctic. Specifically, we suggest that drones can minimize human-bear conflicts by allowing users to observe bears from a safe vantage point; produce high-quality behavioural data that can be reviewed as many times as needed and shared with multiple stakeholders; and foster knowledge generation through co-production with northern communities. We posit that in some instances drones may be considered as an alternative tool for studying polar bear foraging behaviour, interspecific interactions, human-bear interactions, human safety and conflict mitigation, and den-site location at individual-level, small spatial scales. Finally, we discuss flying techniques to ensure ethical operation around polar bears, regulatory requirements to consider, and recommend that future research focus on understanding polar bears’ behavioural and physiological responses to drones and the efficacy of drones as a deterrent tool for safety purposes.
... We use direct behavioural observations of polar bears foraging on seaduck eggs, and apply a descriptive approach guided by classical optimality theory and previous empirical research on foraging behaviour to explore decisionmaking strategies of polar bears foraging in a terrestrial environment as they deplete the resource. In a previous study in this system, polar bears were observed to consume clutches at a decelerating rate (indicating declining resource density) until they depleted the colony of eggs [48]. Therefore, we examined whether foraging bears are responsive to declining resource density by sampling the area and exhibiting behaviours in accordance with expectations of OFT that would minimize net energetic expenditure. ...
... Importantly, each video was timestamped and foraging bouts were placed in chronological order which served as a proxy for resource depletion (i.e. declining resource density over time) as bears consumed clutches at a decelerating rate until they depleted the colony [48]. ...
... For example, should the number of empty nests encountered decline while bears increased total number of nests visited, the implications of this behaviour (increased foraging efficiency) would be different should the opposite trend be observed (decreased foraging efficiency). For further detail on behaviours at a nest, see [48]. In addition to these foraging behaviours, we also recorded the duration of time a bear spent walking and standing (i.e. ...
Climate-mediated sea-ice loss is disrupting the foraging ecology of polar bears ( Ursus maritimus ) across much of their range. As a result, there have been increased reports of polar bears foraging on seabird eggs across parts of their range. Given that polar bears have evolved to hunt seals on ice, they may not be efficient predators of seabird eggs. We investigated polar bears' foraging performance on common eider ( Somateria mollissima ) eggs on Mitivik Island, Nunavut, Canada to test whether bear decision-making heuristics are consistent with expectations of optimal foraging theory. Using aerial-drones, we recorded multiple foraging bouts over 11 days, and found that as clutches were depleted to completion, bears did not exhibit foraging behaviours matched to resource density. As the season progressed, bears visited fewer nests overall, but marginally increased their visitation to nests that were already empty. Bears did not display different movement modes related to nest density, but became less selective in their choice of clutches to consume. Lastly, bears that capitalized on visual cues of flushing eider hens significantly increased the number of clutches they consumed; however, they did not use this strategy consistently or universally. The foraging behaviours exhibited by polar bears in this study suggest they are inefficient predators of seabird eggs, particularly in the context of matching behaviours to resource density.
... However, in recent years, earlier spring sea-ice break-up in northern Hudson Bay and reduced access to seal prey have driven polar bears ashore to EBI earlier, where bears now overlap with eiders during laying and incubation [24]. As a result, eiders are experiencing increasing nest predation pressure by polar bears [38][39][40], insofar that duckling recruitment rates have been documented close to zero in more recent years (H.G.G. and O.P.L. 2019, personal observations). ...
Several predator–prey systems are in flux as an indirect result of climate change. In the Arctic, earlier sea-ice loss is driving polar bears (Ursus maritimus) onto land when many colonial nesting seabirds are breeding. The result is a higher threat of nest predation for birds with potential limited ability to respond. We quantified heart rate change in a large common eider (Somateria mollissima) breeding colony in the Canadian Arctic to explore their adaptive capacity to keep pace with the increasing risk of egg predation by polar bears. Eiders displayed on average higher heart rates from baseline when polar bears were within their field of view. Moreover, eiders were insensitive to variation in the distance bears were to their nests, but exhibited mild bradycardia (lowered heart rate) the longer the eider was exposed to the bear given the hen's visibility. Results indicate that a limited ability to assess the risks posed by polar bears may result in long-term fitness consequences for eiders from the increasing frequency in interactions with this predator.
... As an indirect effect of climate change, polar bears, a species traditionally dependent on ice as a platform to hunt marine mammals (Thiemann et al. 2008), are coming ashore earlier from a shortened seal-hunting season and are now temporally and spatially overlapping on land with colonial nesting eiders (Stirling et al. 2004, Stirling andParkinson 2006). A consequence of this spatio-temporal overlap is that eiders are now experiencing increasing nest predation pressure by polar bears (Dey et al. 2017, Barnas et al. 2020, Jagielski et al. 2021a, Jagielski et al. 2021b). Polar bear presence in eider nesting colonies had been seldomly reported over the past century (e.g., Lønø 1970), but eider encounters with polar bears have steadily increased over the past few decades. ...
Predator-prey dynamics in the Arctic are being altered with changing sea ice phenology. The increasing frequency of predation on colonial nesting seabirds and their eggs by the polar bear (Ursus maritimus) is a consequence of bears shifting to terrestrial food resources through a shortened seal-hunting season. We examined antipredator responses in a colony of nesting Common Eiders (Somateria mollissima) on East Bay Island, Nunavut, Canada, which is exposed to established nest predators, such as arctic fox (Vulpes lagopus), but also to recent increases in polar bear nest predation due to the bears’ lost on-ice hunting opportunities. Given eiders’ limited eco-evolutionary experience with bears, we aimed to experimentally contrast eider responses to the recent predation pressure by polar bears to those induced by their more traditional mammalian predator, the arctic fox. Our goal was to characterize whether this population of eiders was vulnerable to a changing predator regime. Using simulated approaches of visual stimuli of both predator types, we measured eider heart rate and flight initiation distance as physiological and behavioral metrics, respectively, to characterize the perceived risk of and subsequent response to imminent threat posed by these two predators that differ in historical encounter rates. Eider heart rates were more responsive to impending visual cues of arctic foxes compared to polar bears, but birds responded behaviorally to all simulated threats with similar flight initiation distances. Results suggest eiders may not perceive the full risk that bears pose as egg and adult predators, and are therefore expected to suffer negative fitness consequences from this ongoing and increasing interaction. Eiders may therefore require conservation intervention to aid in their management.
... Arctic coastal habitats lack an abundance of energy-dense (high-fat) foods that polar bears need to offset lost time consuming marine mammal blubber on the sea ice (Rode et al., 2015b). Although polar bears have been observed eating birds, bird eggs, Arctic char (Salvelinus alpinus), berries, herbaceous vegetation, and other foods on land (Derocher et al., 1993;Gormezano andRockwell, 2013, Iverson et al., 2014), the low availability and quality of most terrestrial foods are insufficient to meet the energetic demands of the majority of bears in populations for extended periods (Rode et al., 2015b;Jagielski et al., 2021a;. Despite consumption of terrestrial foods by some bears, they continue to lose body mass while on land (Atkinson et al., 1996) and longer durations spent onshore during the ice-free period have been correlated with lower body mass, cub survival, and population declines (Stirling et al., 1999;Regehr et al., 2007;Scuillo et al., 2016;Lunn et al., 2016). ...
Monitoring changes in the distribution of large carnivores is important for managing human safety and supporting conservation. Throughout much of their range, polar bears (Ursus maritimus) are increasingly using terrestrial habitats in response to Arctic sea ice decline. Their increased presence in coastal areas has implications for bear-human conflict, inter-species interactions, and polar bear health and survival. We examined observed trends in land use over three decades by polar bears in the southern Beaufort Sea (SB) and Chukchi Sea (CS) where bears have traditionally spent most of the year on the sea ice. Using data from 408 adult females fitted with satellite radio-collars, we examined trends in the annual proportion of bears coming onshore (hereafter referred to as “percent of bears”) during the summer for ≥21 days, arrival and departure dates, duration spent onshore and relationships with sea ice metrics. We then estimated future land use through 2040 by extrapolating trends and by combining observed relationships between land use and sea ice with projections of future sea ice from an ensemble of earth system models. The observed percent of bears summering onshore and their duration onshore was correlated with the percent of open water that occurred within their population’s range between July and October. As sea ice declined, the percent of bears summering onshore increased from ~5 to 30% in the SB and ~10 to 50% in the CS and duration onshore increased by >30 days to 60–70 days in both populations. Using a range of greenhouse gas emission scenarios and adjustments for faster than forecasted sea ice loss we estimated that 50-62% of SB and 79-88% of CS bears will spend 90–108 and 110–126 days onshore during summer in the SB and CS, respectively, by 2040. Sea ice projections varied little between greenhouse gas emission scenarios prior to 2040 but diverged thereafter. Observed and forecasted increases in polar bear land occupancy puts more bears in proximity to human activities and settlements for longer durations while extending the lack of access to their primary prey. Because human conflict is one of the primary factors affecting the conservation of large carnivores worldwide, mitigation of bear-human interactions on land will be an increasingly important component of polar bear conservation.
... In regions where a substantial decline in sea ice habitat has occurred, the strength of the predator-prey relationship between polar bears and ringed seals appears to be weakening, which may signal this change as a generalized response of polar bears to sea ice loss (Hamilton et al., 2017;Yurkowski et al., 2020). Increased summer land use by polar bears in many parts of their range has the potential to further affect this predator-prey relationship as bears use alternative food resources to replace lost hunting opportunities on the sea ice (Hamilton et al., 2017;Jagielski et al., 2021). Because polar bears are a specialist predator with low dietary diversity, they are particularly sensitive to declines in the availability and condition of their primary prey (Rode, Regehr, et al., 2021;Stirling, 1995). ...
Sea ice loss is fundamentally altering the Arctic marine environment. Yet there is a paucity of data on the adaptability of food webs to ecosystem change, including predator‐prey interactions. Polar bears (Ursus maritimus) are an important subsistence resource for Indigenous people and an apex predator that relies entirely on the under‐ice food web to meet their energy needs. Here, we assessed whether polar bears maintained dietary energy density by prey switching in response to spatial‐temporal variation in prey availability. We compared the macronutrient composition of diets inferred from stable carbon and nitrogen isotopes in polar bear guard hair (primarily representing summer/fall diet) during periods when bears had low and high survival 2004‐2016, between bears that summered on land versus pack ice, and between bears occupying different regions of the Alaskan and Canadian Beaufort Sea. Polar bears consumed diets with lower energy density during periods of low survival suggesting that concurrent increased dietary proportions of beluga whales (Delphinapterus leucas) did not offset reduced proportions of ringed seals (Pusa hispida). Diets with the lowest energy density and proportions from ringed seal blubber were consumed by bears in the western Beaufort Sea (Alaska) during a period when polar bear abundance declined. Intake required to meet energy requirements of an average free‐ranging adult female polar bear was 2.1 kg/day on diets consumed during years with high survival but rose to 3.0 kg/day when survival was low. Although bears that summered onshore in the Alaskan Beaufort Sea had higher fat diets than bears that summered on the pack ice, access to the remains of subsistence‐harvested bowhead whales (Balaena mysticetus) contributed little to improving diet energy density. Because most bears in this region remain with the sea ice year‐round, prey‐switching and consumption of whale carcasses onshore appear insufficient to augment diets when availability of their primary prey, ringed seals, is reduced. Our results show that a strong predator‐prey relationship between polar bears and ringed seals continues in the Beaufort Sea. The method of estimating dietary blubber using predator hair, demonstrated here, provides a new metric to monitor predator‐prey relationships that affect individual health and population demographics.
... Despite the considerable dietary flexibility of polar bears (Thiemann et al. 2008), feeding during ice-free summer periods and during winter freeze-up is generally thought to be less common (Stirling and Øritsland 1995). During these periods, polar bears may seek alternative, terrestrial foods, including items from landfills (Lunn and Stirling 1985), caribou (Rangifer tarandus) (Gormezano and Rockwell 2013), beached whale carcasses (Laidre et al. 2018), and eggs within bird colonies (Divoky et al. 2015;Bourque et al. 2020;Jagielski et al. 2021). ...
Polar bears ( Ursus maritimus ) in the southern Beaufort Sea experience long annual periods when preferred seal prey are scarce or are unavailable. Consumption of bowhead whale ( Balaena mysticetus ) carcasses from native Alaskan subsistence hunting is increasingly common for onshore polar bears, yet the energetic consequences of this consumption remain unclear. We use data on bears captured repeatedly over periods that encompassed autumn and winter, combined with calculations, to show that adult female bears likely consume an average of at least 4 seal equivalents during both autumn and winter periods and that considerable variation in energy intake exists across individual bears. We further show that subsistence-caught whale carcasses provide an upper threshold of > 4000 seal equivalents, which could potentially meet mean consumption needs of ~ 80% of the southern Beaufort Sea bear subpopulation during autumn and winter periods. Finally, we modify an existing model to show that observed mass changes over autumn and winter could substantially alter spring foraging habitat choice by females with cubs and the chance that a female with reduced energy reserves would abort a pregnancy or abandon cubs in favor of increasing her own survival; these behaviors could potentially influence population vital rates. Our study highlights the importance of mass dynamics over the autumn and winter months, points to the need for additional data on foraging and energetics over this period, and indicates that the recent declines in polar bear body condition in some subpopulations could have complex effects on reproduction.
... However, similar arguments can be made for species that hibernate, which have phenologies impacted by climate change [32] and depend on multiple habitats throughout the year [33]. Coldresistant species also have phenologies linked to dwindling fat reserves or food resources [34] and are closely tied to high-latitude habitats [35] undergoing rapid change [8]. There are even conflicting claims-for instance that migratory species might be less sensitive to climatic changes (e.g. ...
Freezing temperatures are inherently challenging for life, which is water based. How species cope with these conditions fundamentally shapes ecological and evolutionary processes. Despite this, there is no comprehensive conceptual framework for cold-survival strategies—seasonal migration, cold resistance and torpor. Here, I propose a framework with four components for conceptualizing and quantifying cold-survival strategies. Cold-survival strategies are (i) collectively encompassed by the proposed framework, and that this full breadth of strategies should be considered in focal species or systems ( comprehensive consideration ). These strategies also (ii) exist on a spectrum, such that species can exhibit partial use of strategies, (iii) are non-exclusive, such that some species use multiple strategies concurrently ( combined use ) and (iv) should collectively vary inversely and proportionally with one another when controlling for the external environment (e.g. when considering species that occur in sympatry in their summer range), such that use of one strategy reduces, collectively, the use of others ( proportional use ). This framework is relevant to understanding fundamental patterns and processes in evolution, ecology, physiology and conservation biology.
... While consumption of bird eggs by bears has been reported in the past (Canadian Wildlife Service 1992, Cooke et al. 1995, Derocher 2012, climateinduced loss of spring sea-ice is increasing the amount of time bears spend on land in recent years resulting in more frequent overlap with the incubation period of Arctic nesting birds than has likely occurred in the past (Smith et al. 2010, Iverson et al. 2014. Polar bears are not efficient predators of bird eggs as they are likely to incur energetic losses searching for eggs (Jagielski et al. 2021a, b), but even so, a relatively small number of bears can cause mass colony failure in a short amount of time (Rode et al. 2015, Gormezano et al. 2017, Jagielski et al. 2021b. Mechanisms by which birds can reduce nest loss to foraging bears has garnered little attention and should be relevant for understanding how populations will respond to increasing bear presence. ...
The presence of foraging bears in Arctic breeding bird colonies has been increasingly reported in the literature, and these may constitute disturbance events which cause incubating birds to leave their nest. Avian predators may associate with bears during such events, likely to capitalize on unattended nests in the presence of bears. Here, we estimated changes in daily nest attendance of lesser snow geese Anser caerulescens caerulescens in the presence of foraging bears, and estimated the association between foraging bears and avian predators. We predicted decreased nest attendance by geese on days with bears, and close associations between avian predators and bears. We monitored snow goose nests with cameras from 2013 to 2018 to assess nest attendance behaviours on days when bears were in the colony compared to control days without bears. When bears were present in colonies, we estimated the probability of avian predator occurrence compared to control periods. When controlling for day of incubation and camera placement types, we found no significant effects of bears on daily nest attendance behaviours of snow geese (n = 85). We found a significantly higher probability of observing avian predators when bears were present (0.72) compared to control periods without bears (0.11). We show that snow geese do not alter daily nest attendance in the presence of foraging bears, and suggest this is due to the presence of avian predators.
... This sanctuary is an 112,811 ha area that supports a vast array of migratory Arctic breeding birds, including various species of gulls, ducks, geese and shorebirds. Several mammals, such as Arctic foxes (Vulpes lagopus) and polar bears (Ursus maritimus), also use the area [23][24][25] and take advantage of the abundance of seabird eggs and young as a food source [26]. Due to its importance as a nesting site for a variety of migratory birds, East Bay and the surrounding area has been designated as an Important Bird Area [27], and listed as a key migratory bird terrestrial habitat site by the Canadian Wildlife Service [23]. ...
The Arctic is warming three times faster than the rest of the globe, causing rapid transformational changes in Arctic ecosystems. As these changes increase, understanding seabird movements will be important for predicting how they respond to climate change, and thus how we plan for conservation. Moreover, as most Arctic-breeding seabirds only spend the breeding season in the Arctic, climate change may also affect them through habitat changes in their non-breeding range. We used Global Location Sensors (GLS) to provide new insights on the movement of Arctic-breeding herring gulls ( Larus smithsoniansus ) in North America. We tracked gulls that wintered in the Gulf of Mexico ( n = 7) or the Great Lakes ( n = 1), and found that migratory routes and stopover sites varied between individuals, and between southbound and northbound migration. This inter-individual variation suggests that herring gulls, as a generalist species, can make use of an array of regions during migration, but may be more susceptible to climate change impacts in their overwintering locations than during migration. However, due to our limited sample size, future, multi-year studies are recommended to better understand the impacts of climate change on this Arctic-breeding seabird.
Research on the ecology and biology of marine mammal populations is necessary to understand ecosystem dynamics and to support conservation management. Emerging monitoring tools and instruments offer the opportunity to obtain such information in an affordable and effective way. In recent years, unmanned aerial vehicles (UAVs) have become an important tool in the study of marine mammals. Here, we reviewed 169 research articles using UAVs to study marine mammals, published up until December 2022. The goals of these studies included estimating the number of individuals in populations and groups via photo-identification, determining biometrics and body condition through photogrammetry, collecting blow samples, and studying behavioural patterns. UAVs can be a valuable, non-invasive, and useful tool for a wide range of applications in marine mammal research. However, it is important to consider some limitations of this technology, mainly associated with autonomy, resistance to the marine environment, and data processing time, which could probably be overcome in the near future.
The degree to which individuals adjust foraging behavior in response to environmental variability can impact foraging success, leading to downstream impacts on fitness and population dynamics. We examined the foraging flexibility, average daily energy expenditure, and foraging success of an ice-associated Arctic seabird, the thick-billed murre (Uria lomvia) in response to broad-scale environmental conditions at two different-sized, low Arctic colonies located <300 km apart. First, we compared foraging behavior (measured via GPS units), average daily energy expenditure (estimated from GPS derived activity budgets), and foraging success (nutritional state measured via nutritional biomarkers pre- and post- GPS deployment) of murres at two colonies, which differ greatly in size: 30,000 pairs breed on Coats Island, Nunavut, and 400,000 pairs breed on Digges Island, Nunavut. Second, we tested whether colony size within the same marine ecosystem altered foraging behavior in response to broad-scale environmental variability. Third, we tested whether environmentally induced foraging flexibility influenced the foraging success of murres. Murres at the larger colony foraged farther and longer but made fewer trips, resulting in a lower nutritional state and lower foraging success compared to birds at the smaller colony. Foraging behavior and foraging success varied in response to environmental variation, with murres at both colonies making longer, more distant foraging trips in high ice regimes during incubation, suggesting flexibility in responding to environmental variability. However, only birds at the larger colony showed this same flexibility during chick rearing. Foraging success at both colonies was higher during high ice regimes, suggesting greater prey availability. Overall, murres from the larger colony exhibited lower foraging success, and their foraging behavior showed stronger responses to changes in broad-scale conditions such as sea ice regime. Taken together, this suggests that larger Arctic seabird colonies have higher behavioral and demographic sensitivity to environmental change.
Aerial drones are increasingly being used as tools for ecological research and wildlife monitoring in hard-to-access study systems, such as in studies of colonial-nesting birds. Despite their many advantages over traditional survey methods, there remains concerns about possible disturbance effects that standard drone survey protocols may have on bird colonies. There is a particular gap in the study of their influence on physiological measures of stress. We measured heart rates of incubating female common eider ducks (Somateria mollissima) to determine whether our drone-based population survey affected them. To do so, we used heart-rate recorders placed in nests to quantify their heart rate in response to a quadcopter drone flying transects 30 m above the nesting colony. Eider heart rate did not change from baseline (measured in the absence of drone survey flights) by a drone flying at a fixed altitude and varying horizontal distances from the bird. Our findings suggest that carefully planned drone-based surveys of focal species have the potential to be carried out without causing physiological impacts among colonial-nesting eiders.
Nest predation is a primary cause of reproductive failure in birds; thus, predators apply strong selective pressure on nesting behaviour, especially risk assessment behaviours during predator encounters at nests. Prey's risk assessments are not static; rather, dynamic risk assessment theory predicts that prey assess risk in real-time and update it according to changes in cues posed by the predator(s). We used drone videography to film nest-flushing behaviours of common eiders, Somateria mollissima, in response to foraging polar bears, Ursus maritimus, on East Bay Island (Nunavut, Canada). We assessed how cue use influenced flushing behaviour and nest fate in a path analysis using 200 observations of 193 eiders in 2017. Our most supported model found that more direct angles of visual gaze and travel angle by polar bears resulted in conspicuous nest flushes by eiders (β = −0.236 ± 0.059), whereas the presence of herring gulls, Larus argentatus, resulted in more discrete flushes of hens walking from their nests (β = −0.181 ± 0.059). Shorter flush initiation distances between eiders and approaching bears resulted in greater nest predation by polar bears (β = −0.203 ± 0.076). We found no support that an eider's visibility from the nest influenced any component of flushing behaviour. We suggest that during encounters with bears, eiders are capable of assessing risk and making appropriate behavioural decisions to reduce the chances of nest loss. However, as the colony experienced heavy predation by bears in 2017, behavioural responses alone appear to be insufficient to mitigate polar bear predation at the population level.
Drones are increasingly popular tools for wildlife research, but it is importantthat the use of these tools does not overshadow reporting of methodological detailsrequired for evaluation of study designs. Thediversity in drone platforms, sensors, andapplications necessitates the reporting of specific details for replication, but there is littleguidance available on how to detail drone use in peer-reviewed articles. Here, we presenta standardized protocol to assist researchers in reporting of their drone use in wildliferesearch. The protocol is delivered in six sections: Project Overview; Drone System andOperation Details; Payload, Sensor, and DataCollection; Field Operation Details; DataPost-Processing; and Permits, Regulations, Training, and Logistics. Each section outlinesthe details that should be included, along with justifications for their inclusion. To facilitateease of use, we have provided two example protocols, retroactively produced for publisheddrone-based studies by the authors of this protocol. Our hopes are that the current versionof this protocol should assist with the communication, dissemination, and adoption ofdrone technology for wildlife research and management.
Climate change is asymmetrically altering environmental conditions in space, from local to global scales, creating novel heterogeneity. Here, we argue that this novel heterogeneity will drive mobile generalist consumer species to rapidly respond through their behaviour in ways that broadly and predictably reorganize — or rewire — food webs. We use existing theory and data from diverse ecosystems to show that the rapid behavioural responses of generalists to climate change rewire food webs in two distinct and critical ways. First, mobile generalist species are redistributing into systems where they were previously absent and foraging on new prey, resulting in topological rewiring — a change in the patterning of food webs due to the addition or loss of connections. Second, mobile generalist species, which navigate between habitats and ecosystems to forage, will shift their relative use of differentially altered habitats and ecosystems, causing interaction strength rewiring — changes that reroute energy and carbon flows through existing food web connections and alter the food web’s interaction strengths. We then show that many species with shared traits can exhibit unified aggregate behavioural responses to climate change, which may allow us to understand the rewiring of whole food webs. We end by arguing that generalists’ responses present a powerful and underutilized approach to understanding and predicting the consequences of climate change and may serve as much-needed early warning signals for monitoring the looming impacts of global climate change on entire ecosystems.
The California Current Ecosystem (CCE) is a productive eastern boundary upwelling system that supports a wide variety of forage stocks. Decadal and interannual variability in the environment influence forage species, which in turn affects predators. The recent diet of California sea lions (Zalophus californianus; CSL) from Central California was determined using identification of hard parts from scat samples (n = 785) collected on Año Nuevo Island (37.1083°N 122.3378°W) in 2010 and 2012–2016. Comparisons were made with previously reported data from the late 1990’s and with prey availability as measured by fishery-independent surveys. A significant shift in diet was seen between the two decades where diet from the 1990’s was dominated by Pacific sardine (Sardinops sagax) and northern anchovy (Engraulis mordax). By 2010, diet was more diverse, characterized by rockfishes, Pacific hake, and market squid. There were also strong interannual differences in diet during the most recent decade, a time of substantial climate variability in the North Pacific Ocean. In general, prey were consumed in relation to what was available in the environment.
Polar bears (Ursus maritimus) are expected to be adversely impacted by a warming Arctic due to melting of the sea‐ice platform from which they hunt ice‐breeding seals. We evaluated the hypothesis that scavenging on stranded large whale carcasses may have facilitated polar bear survival through past interglacial periods during which sea‐ice was limited by analyzing: (1) present‐day scavenging by polar bears on large whale carcasses; (2) energy values of large whale species; and (3) the ability of polar bears, like the brown bears (Ursus arctos) from which they evolved, to quickly store large amounts of lipids and to fast for extended periods. We concluded that scavenging on large whale carcasses likely facilitated survival of polar bears in past interglacial periods when access to seals was reduced. In a future, ice‐impoverished Arctic, whale carcasses are less likely to provide nutritional refuge for polar bears because overharvesting by humans has greatly reduced large whale populations, carcass availability is geographically limited, and climate‐induced sea‐ice loss is projected to occur at a more rapid pace than polar bears have experienced at any previous time in their evolutionary history.
Ursids are the largest mammals to retain a plantigrade posture. This primitive posture has been proposed to result in reduced locomotor speed and economy relative to digitigrade and unguligrade species, particularly at high speeds. Previous energetics research on polar bears (Ursus maritimus) found locomotor costs were more than double predictions for similarly sized quadrupedal mammals, which could be a result of their plantigrade posture or due to adaptations to their Arctic marine existence. To evaluate whether polar bears are representative of terrestrial ursids or distinctly uneconomical walkers, this study measured the mass-specific metabolism, overall dynamic body acceleration, and gait kinematics of polar bears and grizzly bears (Ursus arctos) trained to rest and walk on a treadmill. At routine walking speeds, we found polar bears and grizzly bears exhibited similar costs of locomotion and gait kinematics, but differing measures of overall dynamic body acceleration. Minimum cost of transport while walking in the two species (2.21 J kg-1 m-1) was comparable to predictions for similarly sized quadrupedal mammals, but these costs doubled (4.42 J kg-1 m-1) at speeds ≥5.4 km h-1 Similar to humans, another large plantigrade mammal, bears appear to exhibit a greater economy while moving at slow speeds.
Intermittent breeding may be adaptive for long-lived species subjected to large accessory reproductive costs, but it may also reflect reduced adaptation to the environment, reducing population growth. Nevertheless, environmental influences on breeding propensity, particularly that of predation risk, remain poorly understood and difficult to study, because non-breeders are typically not identified. Female eiders Somateria mollissima from the Baltic Sea provide an excellent testbed, because nesting females have been exposed to intensifying predation and growing male bias that may increase female harassment. We based our study on long-term data (14 years) on females captured and marked at the nest, and females individually identified at sea irrespective of capture status. We hypothesized that breeding propensity decreases with increasing predation risk and male bias, and increases with breeder age. Consistent with our hypotheses, females nesting on islands with higher nest predation risk were more likely to skip breeding, and breeding probability increased with age. In contrast, the steep temporal decline in breeding propensity could not be reliably attributed to annual adult sex ratio or to the abundance of white-tailed sea eagles (Haliaeetus albicilla), the main predator on females, at the nearby Hanko Bird Observatory. Breeding probability showed significant consistent individual variation. Our results demonstrate that spatiotemporal variation in predation risk affects the decision to breed and high incidence of non-breeding was associated with low fledging success. The increased frequency of intermittent breeding in this declining population should be explicitly considered in demographic models, and emphasis placed on understanding the preconditions for successful reproduction.
In recent decades, traditional ecological knowledge (TEK) has played an increasing role in wildlife management and biodiversity conservation in Canada and elsewhere. This study examined the potential contribution that Inuit TEK (which is one aspect of Inuit Qaujimajatuqangit or Inuit traditional knowledge) could offer to detect and monitor avian cholera and other disease-related mortality among Northern Common Eiders (Somateria mollissima borealis) breeding in the eastern Canadian Arctic. Avian cholera is an infectious disease (Pasteurella multocida) that has been a major conservation issue because of its potential to cause high rates of disease and mortality in several bird species in repeating epizootics; it has spread geographically in North America since the 1940s. In 2004, Inuit hunters from Ivujivik, Nunavik, Québec, were the first to detect avian disease outbreaks among Northern Common Eiders nesting in northeastern Hudson Bay and western Hudson Strait. Laboratory analysis of bird tissues confirmed avian cholera in that region. From 2007 to 2009, we collected Inuit TEK about mortality among Common Eiders and other bird species north and west of where the outbreaks were first detected. During interviews in the communities of Kimmirut, Cape Dorset, Coral Harbour, and Igloolik, Nunavut, Canada (n = 40), Inuit participants reported seeing a total of 8 Common Eiders and 41 specimens of other bird species either sick or dead in northern Hudson Strait, Hudson Bay, and Foxe Basin. Most of the observed disease and mortality events were at sea, on sea ice, or on small nesting islands. Such events probably would have gone undetected by biologists, who were mainly monitoring avian cholera outbreaks on large nesting islands in that region. Inuit participants readily recalled details about the timing, location, and numbers of sick and dead birds that they observed. Some reported signs of disease that were consistent with avian cholera. Inuit also revealed knowledge of two past bird mass mortality events that took place about 60 years and a century ago. Those interviewed indicated that that bird mass mortality events potentially caused by avian cholera had not occurred in the study area prior to 2004, supporting the hypothesis that avian cholera emerged only recently in the eastern Canadian Arctic. This study demonstrated that TEK can be a valuable tool for monitoring future avian cholera outbreaks and other wildlife diseases in remote regions.
A demanding lifestyle
Polar bears appear to be well adapted to the extreme conditions of their Arctic habitat. Pagano et al. , however, show that the energy balance in this harsh environment is narrower than we might expect (see the Perspective by Whiteman). They monitored the behavior and metabolic rates of nine free-ranging polar bears over 2 years. They found that high energy demands required consumption of high-fat prey, such as seals, which are easy to come by on sea ice but nearly unavailable in ice-free conditions. Thus, as sea ice becomes increasingly short-lived annually, polar bears are likely to experience increasingly stressful conditions and higher mortality rates.
Science , this issue p. 568 ; see also p. 514
For many organisms, climate change can directly drive population declines, but it is less clear how such variation may influence populations indirectly through modified biotic interactions. For instance, how will climate change alter complex, multi-species relationships that are modulated by climatic variation and that underlie ecosystem-level processes? Caribou (Rangifer tarandus), a keystone species in Newfoundland, Canada, provides a useful model for unravelling potential and complex long-term implications of climate change on biotic interactions and population change. We measured cause-specific caribou calf predation (1990–2013) in Newfoundland relative to seasonal weather patterns. We show that black bear (Ursus americanus) predation is facilitated by time-lagged higher summer growing degree days, whereas coyote (Canis latrans) predation increases with current precipitation and winter temperature. Based on future climate forecasts for the region, we illustrate that, through time, coyote predation on caribou calves could become increasingly important, whereas the influence of black bear would remain unchanged. From these predictions, demographic projections for caribou suggest long-term population limitation specifically through indirect effects of climate change on calf predation rates by coyotes. While our work assumes limited impact of climate change on other processes, it illustrates the range of impact that climate change can have on predator–prey interactions. We conclude that future efforts to predict potential effects of climate change on populations and ecosystems should include assessment of both direct and indirect effects, including climate–predator interactions.
During much of the year, polar bears in western Hudson Bay use energy-conserving hunting
tactics, such as still-hunting and stalking, to capture seals from sea-ice platforms. Such
hunting allows these bears to accumulate a majority of the annual fat reserves that sustain them
on land through the ice-free season. As climate change has led to earlier spring sea-ice breakup
in western Hudson Bay, polar bears have less time to hunt seals, especially seal pups in their
spring birthing lairs. Concerns have been raised as to whether this will lead to a shortfall in the
bears’ annual energy budget. Research based on scat analyses indicates that over the past 40
years at least some of these polar bears eat a variety of food during the ice-free season and are
opportunistically taking advantage of a changing and increasing terrestrial prey base. Whether
this food will offset anticipated shortfalls and whether land-based foraging will spread throughout
the population is not yet known, and full resolution of the issues requires detailed physiological
and genetic research. For insight on these issues, we present detailed observations on
polar bears hunting without an ice platform. We compare the hunting tactics to those of polar
bears using an ice platform and to those of the closely related grizzly bear. We examine how
the techniques are related and explore how they may have evolved. We also discuss how they
may contribute to polar bear adaptability in the face of climate change projections.
Determining how environmental conditions interact with individual intrinsic properties is important for unravelling the underlying mechanisms that drive variation in reproductive decisions among migratory species. We investigated the influence of sea ice conditions and body condition at arrival on the breeding propensity, i.e. the decision to reproduce or not within a single breeding season, and timing of laying in migrating common eiders (Somateria mollissima) breeding in the Arctic. Using Radarsat satellite images acquired from 2002 to 2013, we estimated the proportion of open water in the intertidal zone in early summer to track the availability of potential foraging areas for pre-breeding females. Timing of ice-breakup varied by up to 20 days across years and showed strong relationship with both breeding propensity and the timing of laying of eiders: fewer pre-breeding individuals were resighted nesting in the colony and laying was also delayed in years with late ice-breakup. Interestingly, the effect of sea ice dynamics on reproduction was modulated by the state of individuals at arrival on the breeding grounds: females arriving in low condition were more affected by a late ice-breakup. Open water accessibility in early summer, a likely proxy of food availability, is thus crucial for reproductive decisions in a (partial) capital breeder. Our predictive capacity in determining how Arctic-breeding seabirds respond to changes in environmental conditions will require incorporating such cross-seasonal cumulative effects.
Significance
Climate change is altering the seasonal timing of biological events, effectively rescheduling the potential interactions among species. We know specialist consumers suffer when they fail to synchronize with their prey; however, little is known about how generalist consumers respond to phenological shifts across multiple food resources. This reshuffling may create novel temporal overlap between foods that were once separated in time. We examined how a generalist consumer, the Kodiak brown bear, responded when two key foods, red elderberry and sockeye salmon, became synchronized. Bears switched from eating salmon to elderberries, disrupting an ecological link that typically fertilizes terrestrial ecosystems and generates high mortality rates for salmon. These results demonstrate an underappreciated mechanism by which climate-altered phenologies can alter food webs.
Drones and unmanned aerial vehicles are increasingly used in research on wildlife. Their wide applications can also give interesting insights into habitat use and population distribution. However, the disturbance they might be responsible for, on species and especially in protected areas has yet to be investigated. We assessed and compared the behavioural response of 11 southern seabird species at the Crozet Islands, Southern Indian Ocean, to drone approaches at specific altitudes. We first show that the behavioural response differed between species depending on the altitude of the drone approach. At 50 m of altitude, only one of the studied species showed a detectable reaction, whereas at 10 m, most species showed strong behavioural postures of stress. Adult penguins breeding in large colonies, and some albatross species showed little behavioural response even when the drone was as close as 3 m, whereas other species such as giant petrels or cormorants appeared highly sensitive to drone approaches. Among King Penguins, although incubating adults showed little signs of behavioural stress, non-breeding adults and fledglings in crèches exhibited strong behavioural responses to the drone approach. Monitoring heart rate allowed us to investigate the link between behavioural and physiological response to that specific potential stressor in king penguins. Whereas we confirmed the expected link between physiological and behavioural response in chicks, breeding adults showed no behavioural sign of stress but had a significant increase in heart rate, the relative increase being higher than in chicks. All together these results have important implications for the conservation of species and should be helpful for future legislations on the use of drones.
Trade-offs between locomotory costs and foraging gains are key elements in determining constraints on predator–prey interactions. One intriguing example involves polar bears pursuing snow geese on land. As climate change forces polar bears to spend more time ashore, they may need to expend more energy to obtain land-based food. Given that polar bears are inefficient at terrestrial locomotion, any extra energy expended to pursue prey could negatively impact survival. However, polar bears have been regularly observed engaging in long pursuits of geese and other land animals, and the energetic worth of such behaviour has been repeatedly questioned. We use data-driven energetic models to examine how energy expenditures vary across polar bear mass and speed. For the first time, we show that polar bears in the 125–235 kg size range can profitably pursue geese, especially at slower speeds. We caution, however, that heat build-up may be the ultimate limiting factor in terrestrial chases, especially for larger bears, and this limit would be reached more quickly with warmer environmental temperatures.
Nineteen subpopulations of polar bears (Ursus maritimus)
are found throughout the circumpolar Arctic, and in all regions they depend
on sea ice as a platform for traveling, hunting, and breeding. Therefore
polar bear phenology – the cycle of biological events – is linked to the
timing of sea-ice retreat in spring and advance in fall. We analyzed the
dates of sea-ice retreat and advance in all 19 polar bear subpopulation
regions from 1979 to 2014, using daily sea-ice concentration data from
satellite passive microwave instruments. We define the dates of sea-ice
retreat and advance in a region as the dates when the area of sea ice drops
below a certain threshold (retreat) on its way to the summer minimum or
rises above the threshold (advance) on its way to the winter maximum. The
threshold is chosen to be halfway between the historical (1979–2014) mean
September and mean March sea-ice areas. In all 19 regions there is a trend
toward earlier sea-ice retreat and later sea-ice advance. Trends generally
range from −3 to −9 days decade−1 in spring and from +3 to +9 days decade−1 in fall, with larger trends in the Barents Sea and
central Arctic Basin. The trends are not sensitive to the threshold. We also
calculated the number of days per year that the sea-ice area exceeded the
threshold (termed ice-covered days) and the average sea-ice concentration
from 1 June through 31 October. The number of ice-covered days is declining
in all regions at the rate of −7 to −19 days decade−1, with larger
trends in the Barents Sea and central Arctic Basin. The June–October sea-ice
concentration is declining in all regions at rates ranging from −1 to −9 percent decade−1. These sea-ice metrics (or indicators of habitat
change) were designed to be useful for management agencies and for
comparative purposes among subpopulations. We recommend that the National
Climate Assessment include the timing of sea-ice retreat and advance in
future reports.
Polar bears (Ursus maritimus) have adapted to an annual cyclic regime of feeding and fasting, which is extreme in seasonal sea ice regions of the Arctic. As a consequence of climate change, sea ice breakup has become earlier and the duration of the open-water period through which polar bears must rely on fat reserves has increased. To date, there is limited empirical data with which to evaluate the potential energetic capacity of polar bears to withstand longer fasts. We measured the incoming and outgoing mass of inactive polar bears (n = 142) that were temporarily detained by Manitoba Conservation and Water Stewardship during the open-water period near the town of Churchill, Manitoba, Canada, in 2009-2014. Polar bears were given access to water but not food and held for a median length of 17 d. Median mass loss rates were 1.0 kg/d, while median mass-specific loss rates were 0.5%/d, similar to other species with high adiposity and prolonged fasting capacities. Mass loss by unfed captive adult males was identical to that lost by free-ranging individuals, suggesting that terrestrial feeding contributes little to offset mass loss. The inferred metabolic rate was comparable to a basal mammalian rate, suggesting that while on land, polar bears can maintain a depressed metabolic rate to conserve energy. Finally, we estimated time to starvation for subadults and adult males for the on-land period. Results suggest that at 180 d of fasting, 56%-63% of subadults and 18%-24% of adult males in this study would die of starvation. Results corroborate previous assessments on the limits of polar bear capacity to withstand lengthening ice-free seasons and emphasize the greater sensitivity of subadults to changes in sea ice phenology.
Nineteen distinct subpopulations of polar bears (Ursus maritimus) are found throughout the Arctic, and in all regions they depend on sea ice as a platform for traveling, hunting, and breeding. Therefore polar bear phenology – the cycle of biological events – is tied to the timing of sea-ice retreat in spring and advance in fall. We analyzed the dates of sea-ice retreat and advance in all 19 polar bear subpopulation regions from 1979 to 2014, using daily sea-ice concentration data from satellite passive microwave instruments. We define the dates of sea-ice retreat and advance in a region as the dates when the area of sea ice drops below a certain threshold (retreat) on its way to the summer minimum, or rises above the threshold (advance) on its way to the winter maximum. The threshold is chosen to be halfway between the historical (1979–2014) mean September and mean March sea-ice areas. In all 19 regions there is a trend toward earlier sea-ice retreat and later sea-ice advance. Trends generally range from −3 to −9 days decade−1 in spring, and from +3 to +9 days decade−1 in fall, with larger trends in the Barents Sea and central Arctic Basin. The trends are not sensitive to the threshold. We also calculated the number of days per year that the sea-ice area exceeded the threshold (termed ice-covered days), and the average sea-ice concentration from 1 June through 31 October. The number of ice-covered days is declining in all regions at the rate of −7 to −19 days decade−1, with larger trends in the Barents Sea and central Arctic Basin. The June–October sea-ice concentration is declining in all regions at rates ranging from −1 to −9 percent decade−1. These sea-ice metrics (or indicators of change in marine mammal habitat) were designed to be useful for management agencies. We recommend that the National Climate Assessment include the timing of sea-ice retreat and advance in future reports.
Sea ice is declining over much of the Arctic. In Hudson Bay the ice melts completely each summer, and advances in break-up have resulted in longer ice-free seasons. Consequently, earlier break-up is implicated in declines in body condition, survival, and abundance of polar bears (Ursus maritimus Phipps, 1774) in the Western Hudson Bay (WH) subpopulation. We hypothesised that similar patterns would be evident in the neighbouring Southern Hudson Bay (SH) subpopulation. We examined trends 1980–2012 in break-up and freeze-up dates within the entire SH management unit and within smaller coastal break-up and freeze-up zones. We examined trends in body condition for 900 bears captured during 1984–1986, 2000–2005, and 2007–2009 and hypothesised that body condition would be correlated with duration of sea ice. The ice-free season in SH increased by about 30 days from 1980 to 2012. Body condition declined in all age and sex classes, but the decline was less for cubs than for other social classes. If trends towards a longer ice-free season continue in the future, further declines in body condition and survival rates are likely, and ultimately declines in abundance will occur in the SH subpopulation.
Reproductive output of polar bears in western Hudson Bay declined through the 1980’s from higher levels in the 1960’s and 1970’s. Age of first reproduction increased slightly and the rate of litter production declined from 0.45 to 0.35 litters/female/year over the study, indicating that the reproductive interval had increased. Recruitment of cubs to autumn decreased from 0.71 to 0.53 cubs/female/year. Cub mortality increased from the early to late 1980’s. Litter size did not show any significant trend or significant annual variation due to an increase in loss of the whole litter. Mean body weights of females with cubs in the spring and autumn declined significantly. Weights of cubs in the spring did not decline, although weights of both female and male cubs declined over the study. The population is approximately 60% female, possibly due to the sex-biased harvest. Although estimates of population size are not available from the whole period over which we have weight and reproductive data, the changes in reproduction, weight, and cub mortality are consistent with the predictions of a densitydependent response to increasing population size.
Nonlinear regression models are applied in a broad variety of scientific fields. Various R functions are already dedicated to fitting such models, among which the function nls() has a prominent position. Unlike linear regression fitting of nonlinear models relies on non-trivial assumptions and therefore users are required to carefully ensure and validate the entire modeling. Parameter estimation is carried out using some variant of the leastsquares criterion involving an iterative process that ideally leads to the determination of the optimal parameter estimates. Therefore, users need to have a clear understanding of the model and its parameterization in the context of the application and data considered, an a priori idea about plausible values for parameter estimates, knowledge of model diagnostics procedures available for checking crucial assumptions, and, finally, an understanding of the limitations in the validity of the underlying hypotheses of the fitted model and its implication for the precision of parameter estimates. Current nonlinear regression modules lack dedicated diagnostic functionality. So there is a need to provide users with an extended toolbox of functions enabling a careful evaluation of nonlinear regression fits. To this end, we introduce a unified diagnostic framework with the R package nlstools. In this paper, the various features of the package are presented and exemplified using a worked example from pulmonary medicine.
Significant information gaps exist regarding the status of polar bears, especially with respect to the impacts of climate change, across large portions of the Arctic. To obtain an updated abundance estimate for the Foxe Basin population, we conducted comprehensive aerial surveys during the 2009 and 2010 ice-free seasons, when bears are confined to land. We sampled with mark-recapture distance sampling protocols on inland and coastal transects and surveyed small islands and remnant ice floes. We observed 816 and 1,003 bears in 2009 and 2010, respectively. Although detection functions differed substantially between years, estimates were consistent between analytical methods and years. Averaging four estimates (two from each year) yielded 2,585 (2,096–3,189) bears, which is similar to an estimate from the 1990s. This result, along with robust cub production, suggests a stable and healthy population despite deteriorating sea ice conditions. Collectively, this and other recent on-land surveys provide a framework for implementing aerial surveys elsewhere. Although aerial surveys do not yield estimates of vital rates or population growth, they enable more rapid and frequent monitoring than mark-recapture. Integrating them in long-term monitoring programs will require consideration of ancillary data to infer status and facilitate setting harvest levels.
If climatic warming occurs, the first impacts on Ursus maritimus will be felt at the southern limits of their distribution, such as in James and Hudson bays, where the whole population is already forced to fast for four momths when the sea ice melts during the summer. Prolonging the ice-free period will increase nutritional stress on this population until they are no longer able to store enough fat to survive the ice-free period. Early signs of impact will include declining body condition, lowered reproductive rates, reduced survival of cubs, and an increase in polar bear-human interactions. In the High Arctic, a decrease in ice cover may stimulate an initial increase in biological productivity. Eventually, however, it is likely that seal populations will decline wherever the quality and availability of breeding habitat are reduced. Rain during the late winter may cause polar bear maternity dens to collapse, causing the death of occupants. Human-bear problems will increase as the open water period becomes longer and bears fasting and relying on their fat reserves become food stressed. If climatic warming occurs, the polar bear is an ideal species through which to monitor the cumulative effects in arctic marine ecosysteme because of its position at the top of the arctic marine food chain. -from Authors
Climate change has been identified as a major driver of habitat change, particularly for sea ice dependent species such as the polar bear (Ursus maritimus). Population structure and space use of polar bears has been challenging to quantify because of their circumpolar distribution and tendency to range over large areas. Knowledge of movement patterns, home range and habitat are needed for conservation and management. This is the first study to examine the spatial ecology of polar bears in the Foxe Basin management unit of Nunavut, Canada. Foxe Basin is in the mid-Arctic, part of the seasonal sea ice ecoregion and it is being negatively affected by climate change. Our objectives were to examine intra-population spatial structure, to determine movement patterns, and to consider how polar bear movements may respond to changing sea ice habitat conditions. Hierarchical and fuzzy cluster analyses were used to assess intra-population spatial structure of GPS satellite collared female polar bears. Seasonal and annual movement metrics (home range, movement rates, time on ice) and home range fidelity (static and dynamic overlap) were compared to examine the influence of regional sea ice on movements. The polar bears were distributed in three spatial clusters and there were differences in the movement metrics between clusters that may reflect sea ice habitat conditions. Within the clusters, bears moved independently of each other. Annual and seasonal home range fidelity was observed and the bears used two movement patterns: on-ice range residency and annual migration. We predict that home range fidelity may decline as the spatial and temporal predictability of sea ice changes. These new findings also provide baseline information for managing and monitoring this polar bear population.
Climate change is predicted to expand the ice-free season in western Hudson Bay and when it grows to 180 days, 28-48% of adult male polar bears are projected to starve unless nutritional deficits can be offset by foods consumed on land. We updated a dynamic energy budget model developed by Molnar et al. to allow influx of additional energy from novel terrestrial foods (lesser snow geese, eggs, caribou) that polar bears currently consume as part of a mixed diet while on land. We calculated the units of each prey, alone and in combination, needed to alleviate these lethal energy deficits under conditions of resting or limited movement (2 km d-1) prior to starvation. We further considered the total energy available from each sex and age class of each animal prey over the period they would overlap land-bound polar bears and calculated the maximum number of starving adult males that could be sustained on each food during the ice-free season. Our results suggest that the net energy from land-based food, after subtracting costs of limited movement to obtain it, could eliminate all projected nutritional deficits of starving adult male polar bears and likely other demographic groups as well. The hunting tactics employed, success rates as well as behavior and abundance of each prey will determine the realized energetic values for individual polar bears. Although climate change may cause a phenological mismatch between polar bears and their historical ice-based prey, it may simultaneously yield a new match with certain land-based foods. If polar bears can transition their foraging behavior to effectively exploit these resources, predictions for starvation-related mortality may be overestimated for western Hudson Bay. We also discuss potential complications with stable-carbon isotope studies to evaluate utilization of land-based foods by polar bears including metabolic effects of capture-related stress and consuming a mixed diet.
Humans have brought about unprecedented changes to environments worldwide. For many species, behavioral adjustments represent
the first response to altered conditions. In this review, we consider the pivotal role that behavior plays in determining
the fate of species under human-induced environmental change and highlight key research priorities. In particular, we discuss
the importance of behavioral plasticity and whether adaptive plastic responses are sufficient in keeping pace with changing
conditions. We then examine the interplay between individual behavioral responses and population processes and consider the
many ways in which changes in behavior can affect ecosystem function and stability. Lastly, we turn to the evolutionary consequences
of anthropogenic change and consider the impact of altered behaviors on the evolutionary process and whether behavior can
facilitate or hinder adaptation to environmental change.
Marine animals forage in areas that aggregate prey to maximize their energy intake. However, these foraging 'hot spots' experience environmental variability, which can substantially alter prey availability. To survive and reproduce animals need to modify their foraging in response to these prey shifts. By monitoring their inter-annual foraging behaviours, we can understand which environmental variables affect their foraging efficiency, and can assess how they respond to environmental variability. Here, we monitored the foraging behaviour and isotopic niche of little penguins (Eudyptula minor), over 3 years (2008, 2011, and 2012) of climatic and prey variability within Port Phillip Bay, Australia. During drought (2008), penguins foraged in close proximity to the Yarra River outlet on a predominantly anchovy-based diet. In periods of heavy rainfall, when water depth in the largest tributary into the bay (Yarra River) was high, the total distance travelled, maximum distance travelled, distance to core-range, and size of core- and home-ranges of penguins increased significantly. This larger foraging range was associated with broad dietary diversity and high reproductive success. These results suggest the increased foraging range and dietary diversity of penguins were a means to maximize resource acquisition rather than a strategy to overcome local depletions in prey. Our results demonstrate the significance of the Yarra River in structuring predator-prey interactions in this enclosed bay, as well as the flexible foraging strategies of penguins in response to environmental variability. This plasticity is central to the survival of this small-ranging, resident seabird species.
From 1981 through 1998, the condition of adult male and female polar bears has declined significantly in western Hudson Bay, as have natality and the proportion of yearling cubs caught during the open water period that were independent at the time of capture. Over this same period, the breakup of the sea ice on western Hudson Bay has been occurring earlier. There was a significant positive relationship between the time of breakup and the condition of adult females (i.e., the earlier the breakup, the poorer the condition of the bears). The trend toward earlier breakup was also correlated with rising spring air temperatures over the study area from 1950 to 1990. We suggest that the proximate cause of the decline in physical and reproductive parameters of polar bears in western Hudson Bay over the last 19 years has been a trend toward earlier breakup, which has caused the bears to come ashore in progressively poorer condition. The ultimate factor responsible for the earlier breakup in western Hudson Bay appears to be a long-term warming trend in April-June atmospheric temperatures.
The Arctic is becoming warmer at a high rate, and contractions in the extent of sea ice are currently changing the habitats of marine top-predators dependent on ice. Polar bears (Ursus maritimus) depend on sea ice for hunting seals. For these top-predators, longer ice-free seasons are hypothesized to force the bears to hunt for alternative terrestrial food, such as eggs from colonial breeding birds. We analyzed time-series of polar bear observations at four locations on Spitsbergen (Svalbard) and one in east Greenland. Summer occurrence of polar bears, measured as the probability of encountering bears and the number of days with bear presence, has increased significantly from the 1970/80s to the present. The shifts in polar bear occurrence coincided with trends for shorter sea ice seasons and less sea ice during the spring in the study area. This resulted in a strong inverse relationship between the probability of bear encounters on land and the length of the sea ice season. Within ten years after their first appearance on land, polar bears had advanced their arrival dates by almost 30 days. Direct observations of nest predation showed that polar bears may severely affect reproductive success of the barnacle goose (Branta leucopsis), common eider (Somateria mollissima) and glaucous gull (Larus hyperboreus). Nest predation was strongest in years when the polar bears arrived well before hatch, with more than 90% of all nests being predated. The results are similar to findings from Canada, and large-scale processes, such as climate and subsequent habitat changes, are pinpointed as the most likely drivers in various parts of the Arctic. We suggest that the increasing, earlier appearance of bears on land in summer reflects behavioral adaptations by a small segment of the population to cope with a reduced hunting range on sea ice. This exemplifies how behavioral adaptations may contribute to the cascading effects of climate change.
1. In total, pregnant Polar Bears that enter maternity dens in late summer/autumn may fast for up to 8 months in addition to meeting the nutritional demands of gestation and lactation. We quantified the nutritional costs of this prolonged `reproductive fast' and examined the effect of variation in maternal body condition on reproductive success. 2. Prior to entering dens, pregnant females were obese, containing as much as 1 kg of fat/kg of lean body mass (LBM). Among bears, LBM increased with body fat mass. This accumulation of LBM may be necessary in order to transport the large fat stores required for fasting, and may also provide a pool of protein essential for reproduction. 3. While fasting, bears lost 43% of body mass. Of the total energy expended on maintenance and reproduction, 93% was drawn from fat stores. This dependency upon fat conforms to the pattern of nutrient metabolism seen among other species adapted to prolonged fasting. Maternal metabolic rate was less than the predicted resting metabolic rate which illustrates the effectiveness of denning as an energy-conserving strategy. 4. Body fat was critically important for reproductive success. In particular, offspring body weight was very strongly related to the size of maternal fat stores before denning. Fatter bears produced heavier cubs which would be more likely to survive. 5. Among bears, pre-denning body condition was positively associated with age. Within the observed range (4-21 years), age-specific reproductive success should thus be highest among older bears. Such an effect could arise if: (1) the body condition of individual bears tends to improve with age and experience or (2) animals of poorer quality and condition die at a younger age.
Dyck and Kebreab (2009) analyzed the required summer intake of arctic char, ringed seal blubber, and berries that polar bears must consume to maintain their body mass during a summer ice-free period. Their calculations of required intake were based on the amount of body mass lost by fasting bears in western Hudson Bay. However, fasting polar bears are in a low metabolic state with energetic requirements less than those of an active, feeding bear. Estimates of energy consumed by captive brown bears were 4-4.5 times higher than the estimates used by Dyck and Kebreab for similar diets. Furthermore, the authors' portrayal of the availability of these resources is misleading because they do not acknowledge limited accessibility of arctic char due to their limited anadromy and predominant occurrence in streams too deep to facilitate efficient capture by polar bears; effects of large interannual fluctuations in the availability of berries or competition with other frugivores; high energetic requirements associated with lengthy foraging times required to locate and consume sufficient fruit; and data from southern Hudson Bay, western Hudson Bay, and the southern Beaufort Sea that document continued declines in several biological indices over the past several decades despite the authors' suggested availability of terrestrially based food resources. Based on current information, arctic char, berries, and ringed seals in open water do not appear to be food sources with the potential to offset the nutritional consequences of an extended ice-free period.
Climate warming is causing unidirectional changes to annual patterns of sea ice distribution, structure, and freeze-up. We summarize evidence that documents how loss of sea ice, the primary habitat of polar bears (Ursus maritimus), negatively affects their long-term survival. To maintain viable subpopulations, polar bears depend on sea ice as a platform from which to hunt seals for long enough each year to accumulate sufficient energy (fat) to survive periods when seals are unavailable. Less time to access to prey, because of progressively earlier breakup in spring, when newly weaned ringed seal (Pusa hispida) young are available, results in longer periods of fasting, lower body condition, decreased access to denning areas, fewer and smaller cubs, lower survival of cubs as well as bears of other age classes and, finally, subpopulation decline toward eventual extirpation. The chronology of climate-driven changes will vary between subpopulations, with quantifiable negative effects being documented first in the more southerly subpopulations, such as those in Hudson Bay or the southern Beaufort Sea. As the bears' body condition declines, more seek alternate food resources so the frequency of conflicts between bears and humans increases. In the most northerly areas, thick multiyear ice, through which little light penetrates to stimulate biological growth on the underside, will be replaced by annual ice, which facilitates greater productivity and may create habitat more favorable to polar bears over continental shelf areas in the short term. If the climate continues to warm and eliminate sea ice as predicted, polar bears will largely disappear from the southern portions of their range by mid-century. They may persist in the northern Canadian Arctic Islands and northern Greenland for the foreseeable future, but their long-term viability, with a much reduced global population size in a remnant of their former range, is uncertain.
Divergent movement strategies have enabled wildlife populations to adapt to environmental change. In recent decades, the Southern Beaufort Sea subpopulation of polar bears (Ursus maritimus) has developed a divergent movement strategy in response to diminishing sea ice where the majority of the subpopulation (73–85%) stays on the sea ice in summer and the remaining bears move to land. Although declines in sea ice are generally considered a challenge to energy balance in polar bears residing in some regions of the Arctic, little quantitative data exists concerning the seasonal energy expenditures of this apex marine carnivore. We used GPS satellite collars with tri‐axial accelerometers and conductivity sensors to measure the location, behavior, and energy expenditure of five adult female polar bears in the southern Beaufort Sea across seasons of sea ice breakup and minimum extent. Using a Bayesian mixed‐effects model, we found that energy expenditure was influenced by month, ocean depth, and habitat type (sea ice or land). Total energy expenditure from May through September ranged from 37.7 – 47.2 mJ kg‐1 for individual bears. Bears that moved to land expended 7% more energy on average from May through September than bears that remained on the receding sea ice. In August, when bears were moving from the sea ice to land or moving north with the receding pack ice, bears that moved to land spent 7% more time swimming and expended 22% more energy. Meaning the immediate cost of moving to land exceeded the cost of remaining on the receding summer pack ice. These findings suggest a physiological reason why the majority of the Southern Beaufort Sea subpopulation continues to inhabit a diminishing summer ice platform. However, bears that moved to land spent 29% more time in preferred hunting habitats over the continental shelf than bears that remained on the sea ice. Bears on land also had access to subsistence‐harvested bowhead whale carcasses. Hence, our findings indicate there may be a greater overall energetic benefit to move to land in this region, which suggests that the use of the diminishing summer sea ice may be functioning as an ecological trap.
Climate change can impact ecosystems by reshaping the dynamics of resource exploitation for predators and their prey. Alterations of these pathways could be especially intense in ecosystems characterized by a simple trophic structure and rapid warming trends, such as in the Arctic. However, quantifying the multiple direct and indirect pathways through which climate change is likely to alter trophic interactions and their relative strength remains a challenge.
Here, we aim to identify direct and indirect causal mechanisms driven by climate affecting predator–prey interactions of species sharing a tundra food web.
We based our study on relationships between one Arctic predator (Arctic fox) and its two main prey – lemmings (preferred prey) and snow geese (alternate prey) – which are exposed to variable local and regional climatic factors across years. We used a combination of models mapping multiple causal links among key variables derived from a long‐term dataset (21 years).
We obtained several possible scenarios linking regional climate factors (Arctic oscillations) and local temperature and precipitation to the breeding of species. Our results suggest that both regional and local climate factors have direct and indirect impacts on the breeding of foxes and geese. Local climate showed a positive causal link with goose nesting success, while both regional and local climate displayed contrasted effects on the proportion of fox breeding. We found no impact of climate on lemming abundance. We observed positive relationships between lemming, fox and goose reproduction highlighting numerical and functional responses of fox to the variability of lemming abundance.
Our study measures causal links and strength of interactions in a food web, quantifying both numerical response of a predator and apparent interactions between its two main prey. These results improve our understanding of the complex effects of climate on predator–prey interactions and our capacity to anticipate food web response to ongoing climate change.
Contemporary climate change has complex effects on animal populations caused by the (non-linear) combination of multiple direct and indirect effects on individuals. These interactions make predictions of the ecological response to climate change challenging; however, predictive models are required to effectively manage wildlife populations and conserve biodiversity. Here, we demonstrate how agent-based models (ABMs) can be used to predict population responses under multiple effects of climate change. We consider the case of northern common eiders (Somateria mollissima borealis), a culturally and ecologically important seaduck which is experiencing dramatic environmental change due to losses in Arctic sea ice. Our model shows that losses in Arctic sea ice will lead to increases in nest predation by polar bears in areas where these species are sympatric. However, climate-mediated increases in breeding propensity and clutch size could have a large positive effect on eider population size. When considered together, these effects are predicted to result in a relatively stable eider population size over a 50-year period. Additionally, assuming eider populations are influenced by climate change in the manner proposed in this study, our model suggests that future eider populations will not be more susceptible to extrinsic perturbations (e.g. severe weather events, disease outbreaks) than were historical populations. As a result, our study demonstrates increasing climatic suitability and increasing nest predation will not lead to major changes in population size in northern common eiders, and emphasizes the importance of considering multiple, interacting effects on wildlife populations experiencing climate change.
Climate change can influence interspecific interactions by differentially affecting species-specific phenology. In seasonal ice environments, there is evidence that polar bear predation of Arctic bird eggs is increasing because of earlier sea ice break-up, which forces polar bears into near-shore terrestrial environments where Arctic birds are nesting. Because polar bears can consume a large number of nests before becoming satiated, and because they can swim between island colonies, they could have dramatic influences on seabird and seaduck reproductive success. However, it is unclear whether nest foraging can provide an energetic benefit to polar bear populations, especially given the capacity of bird populations to redistribute in response to increasing predation pressure. In this study, we develop a spatially explicit agent-based model of the predator-prey relationship between polar bears and common eiders, a common and culturally important bird species for northern peoples. Our model is composed of two types of agents (polar bear agents, and common eider hen agents) whose movements and decision heuristics are based on species-specific bioenergetic and behavioral ecological principles, and are influenced by historical and extrapolated sea ice conditions. Our model reproduces empirical findings that polar bear predation of bird nests is increasing, and predicts an accelerating relationship between advancing ice break-up dates and the number of nests depredated. Despite increases in nest predation, our model predicts that polar bear body condition during the ice-free period will continue to decline. Finally, our model predicts that common eider nests will become more dispersed and will move closer to the mainland in response to increasing predation, possibly increasing their exposure to land-based predators, and influencing the livelihood of local people that collect eider eggs and down. These results show that predator-prey interactions can have non-linear responses to changes in climate, and provides important predictions of ecology change in Arctic ecosystems. This article is protected by copyright. All rights reserved.
The Arctic is warming more rapidly than other region on the planet, and the northern Barents Sea, including the Svalbard Archipelago, is experiencing the fastest temperature increases within the circumpolar Arctic, along with the highest rate of sea ice loss. These physical changes are affecting a broad array of resident Arctic organisms as well as some migrants that occupy the region seasonally. Herein, evidence of climate change impacts on terrestrial and marine wildlife in Svalbard is reviewed, with a focus on bird and mammal species. In the terrestrial ecosystem, increased winter air temperatures and concomitant increases in the frequency of "rain-on-snow" events are one of the most important facets of climate change with respect to impacts on flora and fauna. Winter rain creates ice that blocks access to food for herbivores and synchronizes the population dynamics of the herbivore-predator guild. In the marine ecosystem, increases in sea temperature and reductions in sea ice are influencing the entire food web. These changes are affecting the foraging and breeding ecology of most marine birds and mammals, and are associated with an increase in abundance of several temperate fish, seabird and marine mammal species. Our review indicates that, even though a few species are benefiting from a warming climate, most Arctic endemic species in Svalbard are experiencing negative consequences induced by the warming environment. Our review emphasizes the tight relationships between the marine and terrestrial ecosystems in this High Arctic archipelago. Detecting changes in trophic relationships within and between these ecosystems requires long-term (multi-decadal) demographic, population- and ecosystem-based monitoring, the results of which are necessary to set appropriate conservation priorities in relation to climate warming. This article is protected by copyright. All rights reserved.
Model building and data analysis in the biological sciences somewhat presupposes that the person has some advanced education in the quantitative sciences, and statistics in particular. This requirement also implies that a person has substantial knowledge of statistical hypothesis-testing approaches. Such people, including ourselves over the past several years, often find it difficult to understand the information-theoretic approach, only because it is conceptually so very different from the testing approach that is so familiar. Relatively speaking, the concepts and practical use of the information-theoretic approach are much simpler than those of statistical hypothesis testing, and very much simpler than some of the various Bayesian approaches to data analysis (e.g., Laud and Ibrahim 1995 and Carlin and Chib 1995).
The metabolic rate of three adult female polar bears (Ursus maritimus) was investigated under simulated denning conditions. Experiments were conducted during the winter, using a metabolic chamber as a simulated den. Ambient laboratory temperatures ranged from -10 to -35 C. Adult female polar bears were given the opportunity to enter the den of their own volition. Metabolic measurements were obtained by immobilizing the study animals and moving them into the respiration chamber. The study animals were in the den for a minimum of 1 wk prior to the measurement of oxygen consumption. A total of 50 metabolic measurements were obtained. The average standard metabolic rate for the study animals was reduced by 25% from expected values. The lowest observed metabolic rate averaged about 50% of predicted values for basal metabolism. The bears were held in the simulated den from 27 to 59 days. Weight loss for the three female bears averaged 0.70 kg/day.
Unmanned aerial vehicles (UAVs) have the potential to revolutionize the way research is conducted in many scientific fields [1, 2]. UAVs can access remote or difficult terrain [3], collect large amounts of data for lower cost than traditional aerial methods, and facilitate observations of species that are wary of human presence [4]. Currently, despite large regulatory hurdles [5], UAVs are being deployed by researchers and conservationists to monitor threats to biodiversity [6], collect frequent aerial imagery [7-9], estimate population abundance [4, 10], and deter poaching [11]. Studies have examined the behavioral responses of wildlife to aircraft [12-20] (including UAVs [21]), but with the widespread increase in UAV flights, it is critical to understand whether UAVs act as stressors to wildlife and to quantify that impact. Biologger technology allows for the remote monitoring of stress responses in free-roaming individuals [22], and when linked to locational information, it can be used to determine events [19, 23, 24] or components of an animal's environment [25] that elicit a physiological response not apparent based on behavior alone. We assessed effects of UAV flights on movements and heart rate responses of free-roaming American black bears. We observed consistently strong physiological responses but infrequent behavioral changes. All bears, including an individual denned for hibernation, responded to UAV flights with elevated heart rates, rising as much as 123 beats per minute above the pre-flight baseline. It is important to consider the additional stress on wildlife from UAV flights when developing regulations and best scientific practices.
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Increased land use by polar bears (Ursus maritimus) due to climate-change-induced reduction of their sea-ice habitat illustrates the impact of climate change on species distributions and the difficulty of conserving a large, highly specialized carnivore in the face of this global threat. Some authors have suggested that terrestrial food consumption by polar bears will help them withstand sea-ice loss as they are forced to spend increasing amounts of time on land. Here, we evaluate the nutritional needs of polar bears as well as the physiological and environmental constraints that shape their use of terrestrial ecosystems. Only small numbers of polar bears have been documented consuming terrestrial foods even in modest quantities. Over much of the polar bear's range, limited terrestrial food availability supports only low densities of much smaller, resident brown bears (Ursus arctos), which use low-quality resources more efficiently and may compete with polar bears in these areas. Where consumption of terrestrial foods has been documented, polar bear body condition and survival rates have declined even as land use has increased. Thus far, observed consumption of terrestrial food by polar bears has been insufficient to offset lost ice-based hunting opportunities but can have ecological consequences for other species. Warming-induced loss of sea ice remains the primary threat faced by polar bears.
A study of summer and autumn food habits of polar bears (Ursus maritimus Phipps) on some islands of James Bay and the coastal mainland of southwest Hudson Bay was conducted in 1968 and 1969. Analyses were made of 233 scats collected from islands in James Bay and 212 scats gathered on the southwest coast of Hudson Bay. Birds, primarily Anatidae, were the most commonly used summer and autumn food of bears in James Bay. Marine algae and grasses were the foods most often eaten by bears on the mainland. The diet of the bears from James Bay probably provides a better preparation for winter than the diet of those from the mainland, but evidence suggests that bears in both regions are generally in good physical condition.
Polar bears are a sea ice‐dependent carnivore, sensitive to sea ice habitat loss. Climate change has negatively affected sea ice habitat through much of this species' range. We applied landscape fragmentation analysis to quantify polar bear sea ice habitat loss and fragmentation trends (1979–2008) in Foxe Basin, Hudson Strait and Hudson Bay, Canada. Microwave satellite derived monthly mean sea ice concentration maps were classified into four habitat quality categories, and the trends in fragmentation metrics were analyzed. In all regions where preferred habitat declined, sea ice season length decreased and habitat fragmentation increased. The observed trends may affect polar bear movement patterns, energetics and ultimately population trends. Monitoring of sea ice habitat condition in combination with harvest data can provide a dynamic approach to population management and conservation.