Maternal aggression in rats: effects of visual or auditory deprivation of the mother and dyadic pattern of ultrasonic vocalizations.

Previous studies indicate that somatosensory inputs to the snout and the ventral trunk play critical roles in the elicitation and maintenance of maternal aggression by postpartum lactating Long-Evans Norway rats toward a strange male intruder. In the present studies we examined the possible influence of visual and auditory stimuli in the display of this behavior. In Experiment 1, dams temporarily deprived of visual or auditory input by eyelid suturing or ear molds, respectively, on Day 2 postpartum, were found to have normal levels of maternal aggression 1 day later. In Experiment 2, males were found to contribute about 50% of the short-duration 50-kHz vocalizations, which begin shortly after introduction of the intruder, and all of the long-duration 22-kHz vocalizations, which begin after the onset of attacks. Nonetheless, females tested with males surgically devocalized 7 days earlier were not significantly different in aggressiveness from dams tested with vocalizing males on either Day 1 or Day 4 postpartum. These findings indicate that visual or auditory inputs from the pups or intruder are not critical to the display of maternal aggression in rats, at least within the confines of laboratory housing.