Abstract
We studied sexual size dimorphism (SSD) in captive house mice derived from free-living commensal and non-commensal populations. While females of commensal populations and most strains of laboratory mice are more or less tolerant to each other, females from non-commensal populations are as highly aggressive as their male conspecifics.
As body size considerably contributes to fighting success, we addressed the question whether sexual size dimorphism in commensal mice, with larger males, can be attributed to the switch to the commensal way of life. We found that newborn males tended to be larger than newborn females but this tendency rapidly disappeared during the early postnatal period.
Starting from a nearly monomorphic state at the age of two weeks, size difference between the sexes was established gradually up to the end of the experimental period. We found no significant differences in SSD among the studied populations at any age.