Partial migration is observed when only a part of the population migrates, the other part exhibiting a sedentary behaviour. It has been shown that some individuals are more likely to migrate, and induce the departure in migration of others individuals who would have remained non-migrant in their absence. This phenomenon is called imitation. In this study, we have evaluated by a modelling work the influence of the imitation behaviour on the dynamics of partially migratory populations, and on the evolution of the tendency to migrate. Two models have been studied. The first model takes into account only the imitation , and generates cyclical or chaotic dynamics when the growth rate of the migrant population and the negative density-dependance are small. However, it does not predict the appearance of partial migration in the population. The second takes into account imitation and environmental stochasticity. This model leads to the emergence of an intermediate propensity to migrate: migrants and non-migrants can co-exist, which is characteristic of partial migration. In addition, a high propensity to imitate others associated with low negative density-dependence leads to the emergence and maintenance of a dimorphism regarding the tendency to migrate. This phenomenon could be branching, and could help to explain the observations of previous studies indicating that the propensity to migrate is a variable trait in populations. Moreover, it seems that observing a branch in a partial migration model is an unprecedented result.

Language (The language you are writing in)