Survival and Dispersal of Young White-Footed Mice Born in Nest Boxes

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Abstract
Thirty-nine litters of white-footed mice (Peromyscus leucopus) were followed from birth in nest boxes until establishment of home ranges in an isolated, 2-ha woodlot. The sex ratio at birth was significantly biased toward males in the spring and females in the fall. Mothers were significantly heavier in spring than in fall. In the spring, 39 of 97 pups (40%) were weaned, while in the fall only 8 of 67 (12%) were weaned. After three weeks of age the expectation of further life was more than 9 weeks for spring-born and less than 3 weeks for fall-born mice. Young left the nest at an average age of 5.6 weeks. Mothers consistently retained their home ranges after young dispersed. With the exception of one litter, littermates did not aggregate after dispersal, but scattered throughout the woodlot. Males settled at an average of 75 m from the natal nest, females an average of 39 m. These small dispersal distances, coupled with a near absence of immigration and low spring populations, suggest the possibility of inbreeding.