Determinants of Natal Dispersal and Space Use in Grey-Sided Voles, Clethrionomys rufocanus: A Combined Field and Laboratory Experiment

The potential influences of prenatal and postweaning social environment on natal dispersal, space use, body growth and social behaviour were studied in an experimental population of Clethrionomys rufocanus. The experimental population consisted of 14 females and their laboratory born litters which were introduced onto the experimental plot; a 2 ha island. The effects of prenatal stress were studied by exposing an experimental group of captive, pregnant females to new, unfamiliar, adult females during the 2-3 last days of pregnancy, while postweaning maternal influences were studied by removing an experimental group of free-ranging mothers from their home ranges 7 d after their offspring were weaned. Offspring from experimental mothers did not show significant responses in space use, dispersal tendency or social behaviour to the stress treatment or removal of mothers from maternal home ranges. However, female offspring from prenatally stressed mothers grew more rapidly than offspring from control mothers. Females originating from litters with a male-biased sex ratio had the greatest tendancy to disperse, while males were not affected by litter sex ratio. Dispersing females showed significantly more avoidance behaviour in arena encounters, shared less space and had larger home ranges than philopatric females. I conclude that whether an individual C. rufocanus disperses or not seems to be more dependent on predisposed behavioural characteristics than to local variability in the social environment.