Effects of male kinship and agonistic behaviour on reproduction and odour preferences of female house mice, Mus domesticus

In gregarious species, males may wound or kill females during intermale contest competition, which directly affects females fitness. However, male-male agonistic encounters may also have more subtle effects on females by creating a stressful social environment in which females live. We examined whether male-male aggression affects female fitness and odour preference in house mice. We tested (1) whether pairs of brothers would be less likely to fight than pairs of nonbrothers; (2) whether females housed with two males that were brothers would have higher reproductive success than females housed with two males that were not brothers and (3) whether females would show a preference for the odours of brother or nonbrother pairs. Males that were brothers were less aggressive towards each other than were nonbrothers, and females housed with males that were brothers produced significantly more litters than those housed with males that were not brothers. Females did not show a preference for the odours of brothers or nonbrothers, but they did prefer odours of less aggressive pairs of males. These findings suggest that while contest competition favours fighting among males, female choice and kin selection favour tolerance.