Maternal behavior, pup vocalizations, and pup temperature changes following handling in mice of 2 inbred strains.

A cross-fostering design was used to examine maternal behavior, pup vocalizations, and pup temperature changes following an infantile procedure in C57BL/6J (C) and A/J (A) mice. In Experiment I, maternal behavior of C and A mothers after infantile handling differed in a number of ways irrespective of the strain of the foster pups. In addition, A pups were retrieved faster but licked less than were C pups by mothers of both strains. Handling appeared to increase the probability that strain differences would occur in that no differences between the lines, in either the behavior of the mothers or the capacity of the pups to elicit maternal behavior, were found during observations made just prior to daily handling. These observations also revealed that mothers of both strains treated same-strain foster pups differently than they treated foster pups of another strain. In Experiment II, A pups were found to emit more ultrasound following handling than were C pups, suggesting that retrieval but not pup-licking was stimulated by ultrasonic signals. Measurement of pup temperature during and following the handling procedure showed that (1) strain differences in ultrasonic signaling were not related to strain differences in the degree of hypothermia experienced by the pups; (2) recovery of body temperature following handling was slow for pups of both strains, and depended to some degree on the strain of the pups' foster mother; and (3) development of thermoregulation occurred more rapidly in C than A pups.