BODY-MASS AND SIZE IN FEMALE DEER MICE, PEROMYSCUS-MANICULATUS, AS A FUNCTION OF TIME SINCE BREEDING

Body masses of 16 littermate pairs of female deer mice, Peromyscus maniculatus, were compared at six points before and after either pairing and breeding with a male or pairing with a female. Females that produced three litters were significantly heavier than littermates paired with females for as long as 4 months after separation. In addition, a significant effect on length of body was found at autopsy. In studies of body size, it is important to consider not only current breeding status, but also recent breeding activity.