Abstract
The conditions regulating long distance migrations of large animal groups remain elusive in ecology. It has been suggested that individual interactions, environmental constraints and social dynamics play a major role in group formation and migration processes. The challenge is in how to incorporate those dynamics within a framework that reproduces observed dynamics and allows to investigate conditions for the persistence or collapse of migrations. We introduce a general model for seasonally migratory populations where individuals belong to separate contingents each representing a specific migration strategy. Contingents mix during the reproductive phase while the feeding migration is regulated by group formation and social learning. The model is solved numerically, illustrating key factors shaping population dynamics and migration. We identify non-linear critical thresholds in social learning regulating successful migrations. We also determine the conditions for similar thresholds in the behavioural adaptation of the species. This indicates that migration strategies could disappear from a population given social and environmental constraints. These results offer new perspectives on animal conservation and environmental management. Indeed, the removal of individual migrants may have long term consequences for the migratory strategies of the population, possibly leading to irreversible shifts in social behaviour and disruptions of local communities.