Parental Aggression Displayed by Female Mice in Relation to the Sex, Reproductive Status and Infanticidal Potential of Conspecific Intruders

The parental aggression of female mice (Mus domesticus Rutty) towards strange conspecifics known to vary in their tendency to commit infanticide was examined. Twenty-four hours after stud males removal, resident lactating females (with pups aged 3-5 days) were confronted with the following types of intruders: the reintroduced stud, i.e. the father of the pups, a strange father, sexually naive and recently sexually experienced (24 hr prior testing) males, virgin females. Parental attack was mainly elicited by sexually naive and recently sexually experienced males which were also most likely to kill and cannibalize pups. The stud males did not show infanticide and were never attacked. Remarkably, strange fathers were rarely attacked by lactating females and they rarely killed unrelated pups. The data seem to support the view that lactating female mice might be capable of assessing the infanticidal potential of conspecific intruders and of adopting the most appropriate behavioural strategy. Although parental attack was not very successful in thwarting infanticide, the data are discussed in terms of a possible counterstrategy to defend parental investment, and the situational cues females use to distinguish between males with or without parental experience. © Taylor & Francis Group, LLC