Kinship and Origin Effects on Dispersal and Space Sharing in Clethrionomys Rufocanus

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Abstract
An experimental population of Clethrionomys rufocanus with known kinship and life history was established by introducing adult females together with their newly weaned litters onto an island. Dispersal and space use by individual voles were studied by radiotelemetry and intensive live—trapping. Dispersal occurred in relation to the process of sexual maturation. Males matured and dispersed later than females. Dispersal was highly male biased. No mature males remained at their natal site, whereas more than a third of the females were philopatric and reproduced in their natal range. Litter sex ratio accounted for 79% of the total variation in dispersal tendency among young females. Females originating from litters with a male—biased sex ratio had the greatest tendency to disperse. Dispersal in males was not related to litter sex ratio or to three other origin variables that were included in the analysis. Space sharing occurred mainly among philopatric females. Females that dispersed generally avoided contact with other females. Philopatry, coupled with general sociability rather than selective sociability among kin, was probably responsible for the occurrence of extensive space sharing between certain females. Since males dispersed in the absence of obvious external cues, dispersal is most likely triggered by some inflexible physiological mechanism in this sex. Differential exposure to andrigens during prenatal life could possibly explain the great variation in dispersal and space—sharing tendencies among females.