The heritability of migration behaviours in a wide-ranging ungulate

Migration behaviour is thought to be declining globally in the face of rapid human-mediated environmental change. While many species exhibit individual plasticity in their migratory behaviour, not all species demonstrate the level of plasticity necessary to adjust to novel conditions. Selection on heritable behaviours might therefore play an important role in the maintenance of migratory phenotypes for some species. Using GPS and genomic data from 242 individuals (256 animal-years) in a pedigree-free quantitative genetic approach, we estimated heritability, repeatability, and sources of environmental variation for migration traits in migrating mule deer (Odocoileus hemionus). We also estimated heritability of body size to ensure validity of our results. Heritability estimates of body size traits were comparable to the current estimates for ungulate body size. We found low heritability for broad patterns of migration timing, distance, and duration, but high heritability for movement rate along the migratory route. Our findings suggest that wild mule deer populations have the potential to respond to selection pressure generated by human activity or global environmental changes through microevolutionary changes in migration behaviours. Significance StatementMigration behaviour is critical for the reproduction and survival of a wide variety of taxa, yet there have been global declines in migrations in the face of rapid human-mediated environmental change. Despite our understanding that variation in migration behaviour has both genetic and environmental components, studies quantifying the sources of genetic variation contributing to migration phenotypes are lacking. Our study provides, to our knowledge, the first empirical evidence of heritability in a migration behaviour in ungulates. These results have implications for the evolution and maintenance of migration behaviours in natural populations.