Postpartum aggression in mice: The influence of suckling stimulation

The influence of suckling stimulation upon postpartum aggression was studied by removing the nipples (thelectomy) of female mice at various times during pregnancy and lactation. Prepartum thelectomy, regardless of whether it was performed prior to mating or shortly before parturition, in combination with the fostering of young, prevented the exhibition of aggression. The aggressive behavior of females thelectomized following either 2 or 5 days of suckling experience was similar to that of normal lactating females. However, only 25% of animals thelectomized following 24 hr of suckling experience exhibited aggressive behavior. The results demonstrate that suckling stimulation is important for the initiation of postpartum aggression but is not essential in animals that have had at least 48 hr of suckling experience.