Increasing nest predation will be insufficient to maintain polar bear body condition in the face of sea ice loss.
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 breakup, which forces polar bears into nearshore 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 sea duck 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 breakup 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 nonlinear responses to changes in climate and provides important predictions of ecological change in Arctic ecosystems.
Great Lakes Institute for Environmental Research, University of Windsor, 401 Sunset Avenue, Windsor, ON, N9B 3P4, Canada.
Cody J
CJ
Dey
Environment and Climate Change Canada, Science and Technology Branch, Wildlife Research Division, CW405 Biological Sciences BLDG, University of Alberta, Edmonton, AB, T6G 2E9, Canada.
Evan
E
Richardson
Environment and Climate Change Canada, Science and Technology Branch, Wildlife Research Division, CW405 Biological Sciences BLDG, University of Alberta, Edmonton, AB, T6G 2E9, Canada.
David
D
McGeachy
Environment and Climate Change Canada, Canadian Wildlife Service, 335 River Road, Ottawa, ON, K1A 0H3, Canada.
Samuel A
SA
Iverson
Environment and Climate Change Canada, National Wildlife Research Center, 1125 Colonel By Drive, Ottawa, ON, K1A 0H3, Canada.
Hugh G
HG
Gilchrist
Great Lakes Institute for Environmental Research, University of Windsor, 401 Sunset Avenue, Windsor, ON, N9B 3P4, Canada.
Christina A D
CA
Semeniuk
D000818:Animals; D001110:Arctic Regions; D057231:Climate Change; D004372:Ducks; D005247:Feeding Behavior; D005260:Female; D046448:Ice Cover; D011235:Predatory Behavior; D001503:Ursidae / Q000502:physiology*
Arctic; agent-based model; biological interaction; climate change; ecological forecast; foraging; individual based-model