Abstract
Many animal populations providing ecosystem services, including harvest, live in seasonal environments and migrate between seasonally distinct ranges. Unfortunately, two major sources of human-induced global change threaten these populations: climate change and anthropogenic barriers. Anthropogenic infrastructure developments present a global threat to animal migrations through increased migration mortality or behavioral avoidance. Climate change alters the seasonal and spatial dynamics of resources and therefore the effects of migration on population performance. We formulated a population model with ideal-free migration to investigate changes in population size and harvest yield due to barriers and seasonal dynamics. The model predicted an increasing proportion of migrants when the difference between areas in seasonality or carrying capacity increased. Both migration cost and behavioral avoidance of barriers substantially reduced population size and harvest yields. Not surprisingly, the negative effects of barriers were largest when the population benefited most from migration. Despite the overall decline in harvest yield from a migratory population due to barriers, barriers could result in locally increased yield from the resident population following reduced competition from migrants. Our approach and results enhance the understanding of how global warming and infrastructure development worldwide may change population dynamics and harvest offtake affecting livelihoods and rural economies.
Highlights
Many animal populations benefit from seasonal shifts in resource distribution by migrating between seasonally distinct ranges (Fryxell and Sinclair 1988; Avgar et al 2013)
We investigate how population dynamics and sustainable harvest of migratory populations are affected by barriers to migration and changes in seasonality
We presented a simple model for the dynamics of a density-dependent migratory population to investigate the effects of changes in seasonality and migration barriers on population size and harvest
Summary
Many animal populations benefit from seasonal shifts in resource distribution by migrating between seasonally distinct ranges (Fryxell and Sinclair 1988; Avgar et al 2013). A structure can act as a barrier by altering animal behavior, i.e., an individual may avoid a barrier resulting in a decreased crossing probability without necessarily a direct effect on its survival (Beyer et al 2016; Shepard et al 2008; Jaeger and Fahrig 2004) The latter can be a non-adaptive behavioral response, when mortality risk is low and benefits of migration are high. We build upon the migratory population model used by Fryxell and Holt (2013), but replaced the migratory morphs in that model with behaviorally plastic ideal-free migration (Mariani et al 2016) and allowed for population harvest This allowed us to investigate the effects of changing seasonality and movement barriers through both fitness cost and non-adaptive barrier avoidance on population dynamics and harvest strategies. The seasonal fitness in an area will fluctuate between exp(r[1 − N]) in summer and exp(−μ) in winter
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