Some situational and experiential determinants of maternal aggression in mice

Abstract

Five experiments were conducted in order to examine the influence of some simple situational and experiential factors on the maternal aggression displayed by Rockland-Swiss (R-S) Albino mice toward adult male R-S intruders. The results of Experiment 1 showed that aggression is highest during the early lactation period (Postpartum Days 4 and 8) and is absent by the end of the lactation period (Postpartum Days 16 and 20). Experiment 2 showed that the aggression displayed by recently parturient (i.e., early lactating) females rapidly declines during a 10 minute test session with most attacks exhibited during the first 3 minutes of the encounter and few thereafter. The results of Experiment 3 showed that the behavior is significantly reduced when aggression testing takes place in a neutral cage as compared to testing in the homecage environment. The findings of Experiment 4 showed that young male and female intruders (25 and 45 days of age) are attacked as vigorously as adult (65 days of age) intruders of both sexes. The results of Experiment 5 showed that postweaning social deprivation (i.e., isolation) does not influence the development of aggression by lactating females. The significance of these findings for our understanding of the psychobiological basis of maternal aggression and other forms of agonistic behavior is discussed.