03.02.2023: Competition between females is typically less overtly aggressive than that between males but may still have negative consequences – for example, when females require key resources to reproduce successfully. A study by the University of Veterinary Medicine Vienna and the University of Liverpool published recently in the journal The American Naturalist used mice to investigate to what extent the competition for nesting sites affects reproductive success and whether this is influenced by cooperative behaviour.

Female reproductive success is often limited by access to resources such as safe nest sites or territories. The competition for and defence of nest sites leads to resource competition between females, which is a form of social competition that is widespread among mammals and other vertebrates and can lead to social competition both within and between kin groups. This has important consequences for social and reproductive systems and for population dynamics. Despite this widespread significance, however, the evolutionary consequences of female resource competition remain largely unexplored.

Reproductive success, resource availability and kin cooperation

A recently published study of an experiment conducted at the University of Liverpool used mice (Mus musculus domesticus) to investigate an empirically untested theory according to which both resource availability and relatedness influence reproductive success. In their experiment, the researchers investigated the reproductive costs of defending nesting sites as a limited resource and whether these costs are influenced by cooperative behaviour.

Adverse consequences of resource competition

“Our results support the hypothesis that competition for nest sites between females has detrimental consequences for reproductive success. When the availability of protected nest sites was limited, the female mice we studied were more active, responded more strongly to territorial intrusion and produced smaller offspring,” says study first author Stefan Fischer of the Vetmeduni’s Konrad Lorenz Institute for Ethology on the key findings of the study. Also, communally breeding sisters weaned fewer offspring when competing with unrelated females. However, the researchers found no evidence that the propensity for kin to cooperate increased through competition with unrelated animals.

The article “Fitness costs of female competition linked to resource defense and relatedness of competitors” by Stefan Fischer, Callum Duffield, Amanda J. Davidson, Rhiannon Bolton, Jane L. Hurst and Paula Stockley was published in The American Naturalist.

Scientific article