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

• Published in: Ecology and Evolution
• Main Authors: Cherry, Seth G., Derocher, Andrew E., Lunn, Nicholas J.
• Other Authors: ArcticNet, Canadian Wildlife Federation, Environment Canada, Natural Sciences and Engineering Research Council of Canada, World Wildlife Fund, Churchill Northern Studies Centre
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2016
• Subjects: polar bear; Sea ice; Ursus maritimus
• Online Access: http://dx.doi.org/10.1002/ece3.2233; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fece3.2233; https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.2233; https://onlinelibrary.wiley.com/doi/full-xml/10.1002/ece3.2233

Abstract 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.