Similarities in Dispersal Tendency among Siblings in Four Species of Voles (Microtus)

During periods of population increase in four species of Microtus (Rodentia: Cricetidae), there are significant differences in lifetime and probability of dispersal between sibships. Identifiable families tend to survive or disappear as a unit. No between-family differences were detected in peak and declining populations, or in populations in which dis- persal was experimentally prevented by fencing. In declining populations there were very large differences in survival among members of the same sibship.