Responses of virgin mice, and of maternal females, to normal and caesarian-section delivered pups.

Pups were presented to adult mice of the Porton strain. Significantly more mothers and virgin females retrieved pups to the nest than did virgin males. More virgin females than males licked pups, built nests and assumed lactation posture. Differences were significant even if males that attacked pups were excluded from consideration. Latencies to first appearance of maternal activities were higher than reported by most other workers. Possible genetic strain differences in the response of virgin mice to pups are discussed. In Experiment 2 pups delivered by caesarian section with placentas attached were used. More mothers than either virgin males or females cleaned and accepted pups, indicating that pup cleaning may be controlled by factors different from those influencing other maternal activities.