Influence of females on conflict among wild rats

Ten male wild rats, Rattus norvegicus , trapped as adults, (“residents”) were each kept singly in large cages. During each of four weeks they were exposed daily, on five successive days, for 15 min, to a strange adult male of the same species. In weeks 1 and 3 the residents were alone; in weeks 2 and 4 two adult females were present. A further four males were similarly studied for three weeks; in weeks 1 and 3 females were present, and in week 2 they were absent. All residents except two attacked strange males more when females were present, though the females played no direct part in the encounters. There was evidence of a positive correlation between a ‘threat posture’ and the duration of attack. The theoretical implications of these observations are discussed.