Maternal aggression in CD-l mice: influence of the hormonal condition of the intruder.

PIP: Aggressive maternal behavior was tested by placing intruders in the home cages of 210 individually housed lactating mice 3-8 days postpartum. The intruders were of 6 types: castrated males and females, intact males and females, mothers of 3-8 day old pups, and mothers of older pups. All fights were initiated by the resident lactating female. There were significantly fewer attacks on castrated males than on intact males (p less than .001), and fewer attacks on castrated females than on intact males and females (p less than .001, p less than .01, respectively). There were no attacks on mothers of 3-8 day old pups. Attacks on older mothers were significantly more frequent than on younger mothers (p less than .01). The results indicate that maternal aggression in albino mice is strongly influenced by the hormonal and reproductive state of the intruder.^ieng

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.