Migratory response of polar bears to sea ice loss: to swim or not to swim

Pilfold, Nicholas W.; McCall, Alysa G.; Derocher, Andrew E.; Lunn, Nicholas J.; Richardson, Evan S.

doi:10.1111/ecog.02109

Cited by 108 publications

(83 citation statements)

References 85 publications

(157 reference statements)

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“…; Pilfold et al. ) when they began a directional move toward shore. Long‐distance swimming (>50 km) in Hudson Bay is uncommon relative to other subpopulations and is likely related to the distribution of sea ice at breakup (Pilfold et al.…”

Section: Discussionmentioning

confidence: 99%

Habitat‐mediated timing of migration in polar bears: an individual perspective

Cherry

Derocher

Lunn

2016

Ecology and Evolution

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Migration phenology is largely determined by how animals respond to seasonal changes in environmental conditions. Our perception of the relationship between migratory behavior and environmental cues can vary depending on the spatial scale at which these interactions are measured. Understanding the behavioral mechanisms behind population‐scale movements requires knowledge of how individuals respond to local cues. We show how time‐to‐event models can be used to predict what factors are associated with the timing of an individual's migratory behavior using data from GPS collared polar bears (Ursus maritimus) that move seasonally between sea ice and terrestrial habitats. We found the concentration of sea ice that bears experience at a local level, along with the duration of exposure to these conditions, was most associated with individual migration timing. Our results corroborate studies that assume thresholds of >50% sea ice concentration are necessary for suitable polar bear habitat; however, continued periods (e.g., days to weeks) of exposure to suboptimal ice concentrations during seasonal melting were required before the proportion of bears migrating to land increased substantially. Time‐to‐event models are advantageous for examining individual movement patterns because they account for the idea that animals make decisions based on an accumulation of knowledge from the landscapes they move through and not simply the environment they are exposed to at the time of a decision. Understanding the migration behavior of polar bears moving between terrestrial and marine habitat, at multiple spatiotemporal scales, will be a major aspect of quantifying observed and potential demographic responses to climate‐induced environmental changes.

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Section: Discussionmentioning

confidence: 99%

Habitat‐mediated timing of migration in polar bears: an individual perspective

Cherry

Derocher

Lunn

2016

Ecology and Evolution

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“…Arctic summer sea ice cover is declining (33,34), which is affecting lower trophic levels through increased primary productivity, changes in plankton community structure, and altered benthic-pelagic coupling (35)(36)(37). Sea ice loss also affects ice-dependent upper trophic-level species, such as ringed seals (Phoca hispida), bearded seals (Erignathus barbatus), and polar bears (Ursus maritimus), that use the ice as a platform to forage and breed (38)(39)(40)(41)(42)(43). In addition, summer sea ice historically served as a barrier to many open water species.…”

Section: Figmentioning

confidence: 99%

Sustained disruption of narwhal habitat use and behavior in the presence of Arctic killer whales

Breed

Matthews

Marcoux

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Although predators influence behavior of prey, analyses of electronic tracking data in marine environments rarely consider how predators affect the behavior of tracked animals. We collected an unprecedented dataset by synchronously tracking predator (killer whales, N = 1; representing a family group) and prey (narwhal, N = 7) via satellite telemetry in Admiralty Inlet, a large fjord in the Eastern Canadian Arctic. Analyzing the movement data with a switching-state space model and a series of mixed effects models, we show that the presence of killer whales strongly alters the behavior and distribution of narwhal. When killer whales were present (within about 100 km), narwhal moved closer to shore, where they were presumably less vulnerable. Under predation threat, narwhal movement patterns were more likely to be transiting, whereas in the absence of threat, more likely resident. Effects extended beyond discrete predatory events and persisted steadily for 10 d, the duration that killer whales remained in Admiralty Inlet. Our findings have two key consequences. First, given current reductions in sea ice and increases in Arctic killer whale sightings, killer whales have the potential to reshape Arctic marine mammal distributions and behavior. Second and of more general importance, predators have the potential to strongly affect movement behavior of tracked marine animals. Understanding predator effects may be as or more important than relating movement behavior to resource distribution or bottom-up drivers traditionally included in analyses of marine animal tracking data.predator-prey dynamics | sea ice | biologging | climate change | trait-mediated effects C onsumptive effects (alternatively termed "density-mediated effects") of predators on prey refer to the mortality incurred when predators kill and consume prey during predation events. They can control prey populations and in certain circumstances, restructure ecosystems through trophic cascades (1-3). Nonconsumptive effects (also termed "trait-mediated effects") can similarly affect prey populations by altering species' behavior and space use under perceived or real predation risk, which are associated with decreased fitness through loss of access to key foraging areas, disrupted social structure, increased energy expenditure and stress imposed by persistent vigilance and escape behaviors, and decreased reproductive success (3-7). Nonconsumptive effects are sublethal (8, 9), but because they can impact many individuals in a population simultaneously, the cumulative effect may exceed consumptive effects (8,(10)(11)(12).In terrestrial systems, movement data collected by electronic telemetry tracking tags have been used to clearly show that carnivores affect prey species' use of space and habitat selection (13-15), and these nonconsumptive effects can negatively impact population dynamics (10, 13, 11). When large enough, such effects have even been suggested to lead to trophic cascades (16,17,3). However, there is disagreement about whether nonconsumptive effects ...

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“…Across ecosystems worldwide, climate change has induced shifts in the timing of critical life‐history transitions for a diversity of organisms, from plants to invertebrates, birds, mammals, amphibians and fish (Parmesan & Yohe, ; Parmesan, ; Wolkovich et al ., ; Poloczanska et al ., ; CaraDonna et al ., ; Charmantier & Gienapp, ; Pilfold et al ., ). Increased temperatures and altered precipitation dynamics have noticeable effects on phenological transitions in the spring, with many species now consistently emerging, migrating, or reproducing 1–3 wk earlier than historical averages (Parmesan & Yohe, ; Menzel et al ., ; Sherry et al ., ; Bertin, ; Amano et al ., ; Poloczanska et al ., ).…”

Section: Introductionmentioning

confidence: 97%

Phenological responses to multiple environmental drivers under climate change: insights from a long‐term observational study and a manipulative field experiment

et al. 2018

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Climate change has induced pronounced shifts in the reproductive phenology of plants, yet we know little about which environmental factors contribute to interspecific variation in responses and their effects on fitness. We integrate data from a 43 yr record of first flowering for six species in subalpine Colorado meadows with a 3 yr snow manipulation experiment on the perennial forb Boechera stricta (Brassicaceae) from the same site. We analyze shifts in the onset of flowering in relation to environmental drivers known to influence phenology: the timing of snowmelt, the accumulation of growing degree days, and photoperiod. Variation in responses to climate change depended on the sequence in which species flowered, with early-flowering species reproducing faster, at a lower heat sum, and under increasingly disparate photoperiods relative to later-flowering species. Early snow-removal treatments confirm that the timing of snowmelt governs observed trends in flowering phenology of B. stricta and that climate change can reduce the probability of flowering, thereby depressing fitness. Our findings suggest that climate change is decoupling historical combinations of photoperiod and temperature and outpacing phenological changes for our focal species. Accurate predictions of biological responses to climate change require a thorough understanding of the factors driving shifts in phenology.

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Migratory response of polar bears to sea ice loss: to swim or not to swim

Cited by 108 publications

References 85 publications

Habitat‐mediated timing of migration in polar bears: an individual perspective

Habitat‐mediated timing of migration in polar bears: an individual perspective

Sustained disruption of narwhal habitat use and behavior in the presence of Arctic killer whales

Phenological responses to multiple environmental drivers under climate change: insights from a long‐term observational study and a manipulative field experiment

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