Social dominance, aggressiveness and mating success among male house mice (Mus musculus).

Aspects of male social hierarchies manifest in confined house mice colonies, of population densities comparable with those observed in natural communities, have been studied. Random processes were found to exert significant influences on the social orders established immediately after founding. In addition to the previously reported effect of orders of arrival at the different localities, relative weights were also found to have significant influences on the initial social order.Several changes in the social orders occurred subsequent to the establishment of the initial hierarchies. Aggressiveness and the degree of previous crowding were both found to exert significant effects on the social orders which were finally stabilised. These results are relevant to models recently proposed by Chitty (1960, 1967, 1970) and Christian (1970) for mechanisms of density regulation in rodent populations. In particular, they are consistent with the postulate of Christian (1970) that social dominance ability and density regulation are largely controlled by the adrenopituitary mediated modification of adult behaviour by the juvenile social environment.The relationship between male social status and relative mating success was also investigated. Only a slight positive association was found. Most previous estimates of effective population size have assumed a very pronounced dependence of mating success on social status. The results of the present study thus suggest that the previous estimates have underestimated the effective population size.