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Modelling optimal responses and fitness consequences in a changing Arctic
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- Author(s) / Creator(s)
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Animals must balance a series of costs and benefits while trying to maximize their fitness.
For example, an individual may need to choose how much energy to allocate to reproduction
versus growth, or how much time to spend on vigilance versus foraging. Their decisions depend
on complex interactions between environmental conditions, behavioural plasticity, reproductive
biology, and energetic demands. As animals respond to novel environmental conditions
caused by climate change, the optimal decisions may shift. Stochastic dynamic programming
provides a flexible modelling framework with which to explore these tradeoffs, but this method
has not yet been used to study possible changes in optimal tradeoffs caused by climate change.
We created a stochastic dynamic programming model capturing tradeoff decisions required by
an individual adult female polar bear (Ursus maritimus), as well as the fitness consequences of
her decisions. We predicted optimal foraging decisions throughout her lifetime, as well as the
energetic thresholds below which it is optimal for her to abandon a reproductive attempt. To
explore the effects of climate change, we shortened the spring feeding period by up to 3 weeks,
which led to predictions of riskier foraging behaviour and higher reproductive thresholds. The
resulting changes in fitness may be interpreted as a best-case scenario, where bears adapt instantaneously
and optimally to new environmental conditions. If the spring feeding period was
reduced by 1 week, her expected fitness declined by 15%, and if reduced by 3 weeks, expected
fitness declined by 68%. This demonstrates an effective way to explore a species’ optimal
response to a changing landscape of costs and benefits and highlights the fact that small annual
effects can result in large cumulative changes in expected lifetime fitness. -
- Date created
- 2019-01-01
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- Type of Item
- Article (Draft / Submitted)