Influence of females on conflict among wild rats

Abstract

With 2 figures in the text) Ten male wild rats, Rattus rrorvegicus, 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 thesc Observations are discussed.

Facilitation of intermale aggression in mice through exposure to receptive females.

“…In field studies of seasonally polyestrous or monestrous mammals, dramatic increases in fighting among males have been observed during the breeding season (Bermant & Davidson, 1974;Turner & Iverson, 1973). In the laboratory, Barnett, Evans, and Stoddart (1968) demonstrated that cohabitation with females raises the aggressiveness of wild male rats against unfamiliar males, a finding later replicated with laboratory rats by Flannelly and Lore (1977). Taylor (1975Taylor ( , 1976 found that both dominant and submissive male rats show heightened aggression following brief exposure through a wire mesh screen to estrous females.…”

A longitudinal study of dominance in an outdoor colony of domestic rats.

“…The other limitation to the expression of aggression was the use of all-male groups. When, in contrast, sexually receptive females are present, the aggressiveness of males is clearly enhanced (Barnett, Evans, & Stoddart, 1968;Flannelly & Lore, 1977).…”

Sex differences in aggressive behavior in zebra finches (Poephila guttata).

“…Experiments with other species have also seldom if ever directly compared male-male and female-female aggression in response to other conspecifics under similar conditions, and therefore the kinds of interactions between subject sex and stimulus sex that we found have seldom been reported except anecdotally from the field. For example, it has been shown by several laboratories that male rats and mice are more aggressive toward male intruders if they have been exposed to a female (Barnett et al, 1968;de Catanzaro, 1981;Flannelly & Lore, 1977;Taylor, 1975), but these experiments did not look at responses of females to female intruders as a function of exposure to males. Many experiments have compared aggression between male-male, female-female, or male-female pairs of rodents under identical conditions but without presenting additional animals to see if they stim- ulate increased aggression (Ferkin & Seamon, 1987;Floody, 1983).…”