Effects of social and environmental contexts on multi-male mating and mixed paternity in socially monogamous female prairie voles

With whom and how often to mate are fundamental questions that impact individual reproductive success and the mating system. Relatively few studies have investigated female mating tactics compared with males. Here, we asked how differential access to mates influences the occurrence of mixed paternity and overall reproductive success in socially monogamous female prairie voles (Microtus ochrogaster). We created male- and female-biased sex ratios of prairie voles living in semi-natural outdoor enclosures. We ran paternity analyses to determine the identity and number of mating partners females had and the number of offspring produced. We found that 57.1% of females had litters fathered by two or more males when males outnumbered females, and 87.5% of females had litters with more than one father when females outnumbered males. However, the percentage of mixed paternity and the total number of embryos were not statistically different between social contexts. We determined that female fecundity (i.e. number of embryos) correlated with the number of male fathers in each litter across social contexts. Although our study did not support the hypothesis that social context directly influences female mating decisions, it did suggest that female multi-male mating might lead to increased fertilization success under semi-natural conditions.