Some Demographic Aspects of Dispersers in Fluctuating Populations of the Vole Microtus Townsendii

Abstract

Dispersal of the vole M. townsendii was studied by enclosing 2 populations and by providing an area inside each enclosure into which the voles could disperse. More males dispersed than females, but the excess of males was restricted to the adult weight class. At least 40% of the subadult dispersers were in breeding condition during the nonwinter periods, compared with a maximum of 15% of the resident subadults. Dispersers attained sexual maturity at lower weight than did residents. Juvenile and subadult dispersal was common during the peak summer. Selective dispersal during the increase and peak phases may be an important component of the microtine cycle.