Range expansion during recolonisation: what does animal personality have to do with it?

At the edge of an ongoing expansion, pioneer individuals encounter novel
ecological and evolutionary pressures that may not be experienced by
conspecifics settled in long-colonised areas. Consistent behavioural
differences among conspecifics (animal personality) may be important
determinants of individuals’ successful colonisation of novel environments
and range expansion. By enhancing an individual's ability to find
food and shelter as well as increasing its capacity to navigate novel
environments, behavioural traits such as exploration and risk-taking are
thus expected to be more highly expressed in populations undergoing
expansion than in established populations. We investigated
among-individual variation in behaviours associated to risk-taking and
exploratory tendencies in populations of small mammals during different
stages of the colonisation process. Using a standardized behavioural test
in the field, we quantified exploration and boldness of striped field mice
(Apodemus agrarius, N=95) from six subpopulations from Germany, where they
are established, and in Slovakia, where a recolonisation of the area is
currently in progress, and in control species bank voles (Myodes
glareolus, N=76) that shared the same habitats but were long-established
at all sites. Striped field mice in the expanding populations were
significantly slower in exploring the open field arena, while showing
comparable levels of risk taking compared to conspecifics from established
populations. No difference in behaviour was detected between the
populations of bank voles. Our results suggest that a slow exploration
strategy might play an advantageous role in expansion processes of small
mammal populations.