The effect of captivity on reproduction and development in Peromyscus maniculatus

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Abstract
Artificial selection for high productivity (early maturation and large litters) early in life was maintained in a laboratory colony of Peromyscus maniculatus nebrascensis for 11 generations. A comparison of reproductive and developmental characteristics in this colony indicated that some traits, such as weight of females, age at maturation, and litter size, did not change over generations. However, other traits did change. An initial increase in the proportion of pairs breeding was offset by the inability of females to successfully raise their offspring. Weight of offspring was larger among wild females than among females born in captivity, although weight of offspring was not different between early and late generations in captivity. The relationship between offspring weight and litter size also differed between wild and laboratory-born females. We conclude that data derived from laboratory stocks do not necessarily reflect patterns exhibited by mice in natural populations. We recommend that generations in captivity be treated as a covariate in comparisons among laboratory stocks and that the interrelationships among reproductive and developmental traits be examined under natural conditions.