Research: drivers of migration
What ultimately drives animals to migrate? Why are some species migratory and others sedentary?
Migration, the predictable seasonal movement between multiple habitats is a surprisingly common behavior seen in birds, fish, reptiles, insects, mammals, amphibians, even crustaceans. There are many hypotheses for why species migrate, typically related to climate, breeding resources, and food availability.
We have developed mathematical models to explore the role of infection risk and cost (from parasites or pathogens) in the evolution of migration. We show that migration can lower infection prevalence in a population via several factors (Johns & Shaw 2016). We find that migrants should generally have lower infection prevalence and infection intensity (compared to residents) but should simultaneously have higher parasite diversity (Shaw et al. 2018). We show that migration can be favored as a strategy to reduce infection and is most easily favored when the cost of migration is paid in terms of reduced fecundity, while the cost of infection is paid in terms of reduced survival (Shaw et al. 2019). Finally, we demonstrated that migration can also evolve if it allows parasitized individuals to recover from infection, e.g., by crossing a strong salinity gradient (Shaw & Binning 2016).
Migration, the predictable seasonal movement between multiple habitats is a surprisingly common behavior seen in birds, fish, reptiles, insects, mammals, amphibians, even crustaceans. There are many hypotheses for why species migrate, typically related to climate, breeding resources, and food availability.
We have developed mathematical models to explore the role of infection risk and cost (from parasites or pathogens) in the evolution of migration. We show that migration can lower infection prevalence in a population via several factors (Johns & Shaw 2016). We find that migrants should generally have lower infection prevalence and infection intensity (compared to residents) but should simultaneously have higher parasite diversity (Shaw et al. 2018). We show that migration can be favored as a strategy to reduce infection and is most easily favored when the cost of migration is paid in terms of reduced fecundity, while the cost of infection is paid in terms of reduced survival (Shaw et al. 2019). Finally, we demonstrated that migration can also evolve if it allows parasitized individuals to recover from infection, e.g., by crossing a strong salinity gradient (Shaw & Binning 2016).
We show using both analytic optimal control models (Reluga & Shaw 2014; Reluga & Shaw 2015) and individual-based simulations (Shaw & Couzin 2013) that the details of spatial and temporal resource patterns determine whether migratory or non-migratory behavior is a better movement strategy. We show that traveling in a group allows individuals to effectively 'vote' and make better decisions by pooling information. The conditions that favor the evolution of migration over residency depend strongly on the ultimate motivation for migrating (to breed, feed or to escape harsh climate). This means that future changes in environmental conditions have the potential to impact migratory species in quite different ways, depending in part on the reason particular species migrate. (Shaw & Couzin 2013). We also show that migration timing in the land crab Gecarcoidea natalis is closely tied to sufficient rainfall (Shaw & Kelly 2013). |
Relevant papers
Shaw AK, Craft ME, Zuk M, Binning SA (2019) "Host migration strategy is shaped by forms of parasite transmission and infection cost." Journal of Animal Ecology 88(10) 1601-1602
Shaw AK, Sherman J, Barker FK, Zuk M (2018) "Metrics matter: the effect of parasite richness, intensity and prevalence on the evolution of host migration." Proceedings of the Royal Society B 285(1891): 20182147.
Gnanadesikan GE, Pearse WD, Shaw AK (2017) "Evolution of mammalian migrations for refuge, breeding and food." Ecology and Evolution 7(15): 5891–5900.
Shaw AK (2016) "Drivers of animal migration and implications in changing environments." Evolutionary Ecology 30(6): 991-1007.
Shaw AK, Binning S (2016) "Migratory recovery from infection as a selective pressure for the evolution of migration." American Naturalist 187(4): 491-501.
Johns S, Shaw AK (2016) "Theoretical insight into three disease-related benefits of migration." Population Ecology 58(1): 213-221.
Reluga TC, Shaw AK (2015) "Resource distribution drives the adoption of migratory, partially migratory, or residential strategies." Theoretical Ecology 8: 437-447.
Reluga TC, Shaw AK (2014) "Optimal migratory behavior in spatially-explicit seasonal environments." Discrete and Continuous Dynamical Systems - Series B 19: 3359-3378.
Shaw AK, Kelly KA (2013) "Linking El Niño, local rainfall, and migration timing in a tropical migratory species." Global Change Biology 19: 3283-3290.
Shaw AK, Couzin ID (2013) "Migration or residency? The evolution of movement behavior and information usage in seasonal environments." American Naturalist 181(1): 114-124.
Shaw AK, Sherman J, Barker FK, Zuk M (2018) "Metrics matter: the effect of parasite richness, intensity and prevalence on the evolution of host migration." Proceedings of the Royal Society B 285(1891): 20182147.
Gnanadesikan GE, Pearse WD, Shaw AK (2017) "Evolution of mammalian migrations for refuge, breeding and food." Ecology and Evolution 7(15): 5891–5900.
Shaw AK (2016) "Drivers of animal migration and implications in changing environments." Evolutionary Ecology 30(6): 991-1007.
Shaw AK, Binning S (2016) "Migratory recovery from infection as a selective pressure for the evolution of migration." American Naturalist 187(4): 491-501.
Johns S, Shaw AK (2016) "Theoretical insight into three disease-related benefits of migration." Population Ecology 58(1): 213-221.
Reluga TC, Shaw AK (2015) "Resource distribution drives the adoption of migratory, partially migratory, or residential strategies." Theoretical Ecology 8: 437-447.
Reluga TC, Shaw AK (2014) "Optimal migratory behavior in spatially-explicit seasonal environments." Discrete and Continuous Dynamical Systems - Series B 19: 3359-3378.
Shaw AK, Kelly KA (2013) "Linking El Niño, local rainfall, and migration timing in a tropical migratory species." Global Change Biology 19: 3283-3290.
Shaw AK, Couzin ID (2013) "Migration or residency? The evolution of movement behavior and information usage in seasonal environments." American Naturalist 181(1): 114-124.