Asynchronous breeding in the socially monogamous prairie vole

At least two hypotheses have been proposed for why animals should breed synchronously: (1) to swamp predators and reduce the probability of offspring being killed and (2) to promote monogamy when paternal care is important for offspring survival. Thus prey and monogamous species are likely candidates for synchronous breeding. We conducted an experiment to determine if a prey species, the monogamously breeding prairie vole (Microtus ochrogaster (Wagner, 1842)), breeds synchronously. We conducted eight replicates in which we placed six nulliparous females and six adult males in semi-natural enclosures for 18-21 days to determine if they bred synchronously. The time of conception ranged from 2 to 18 days within replicates with no indication of breeding synchrony within any of the populations. Thus neither predator avoidance nor paternal care models were supported for prairie voles. We conclude that rodents in general are not good models for breeding synchrony and that females use alternative mating tactics to enhance their lifetime reproductive Success. We discuss our results in the context of the prairie vole mating system.