Some effects of strain differences in the maternal behavior of inbred mice.

The frequencies of occurrence of a variety of activities were recorded for inbred female mice of 3 strains in the presence of their own offspring, in the presence of isogenic fostered offspring, and in the presence of nonisogenic fostered offspring. Differences in the frequency of nursing, of grooming and handling the offspring, and of the absence of the female from the nest were related to differences in the rate of early postnatal development of 2 of these strains: in general, those pups receiving less maternal attention developed more rapidly. The effective stimulus for accelerated maturation may lie in the sequential organization of the manipulation of the offspring by the foster mother, rather than in the overall quantity of manipulation received.