Parental-care strategies among muskrats in a female-biased population

In mammals, parental care is primarily maternal, male participation being influenced by access to mates. We studied parental behaviours of muskrats (Ondatra zibethicus) in a female-biased free-ranging population over two breeding seasons, with the objective of assessing the plasticity of parental care under differing mating strategies (monogamy versus polygyny). Weaned juveniles received predominantly paternal rather than maternal care, and the care provided was both direct (i.e., food harvesting) and indirect (i.e., burrow maintenance). Parental care appeared to be affected by the multiple mating opportunities available to some males. Polygynous males provided less parental care, presumably because they devoted extra time to pursuing a multiple-mating strategy. However, polygynous males provided care only to the offspring of their first mate (i.e., a mixed reproductive strategy). Females that were secondary mates of polygynous males appeared to compensate for the lack of male assistance by increasing their level of parental care compared with primary females. These results support the view that monogamy constitutes the fundamental social system in muskrats.