Female meadow voles, Microtus pennsylvanicus, experience a reduction in copulatory behavior during postpartum estrus

In many small mammalian species, females undergo postpartum estrus (PPE), mate, and become pregnant soon after delivering a litter. Mating during PPE implies a trade-off between attending to the new litter and leaving that litter to mate. We tested the hypothesis that copulatory behavior is faster when a female mates during PPE than when it mates outside of PPE, during male-induced estrus (MIE), a time when it is not lactating. We compared several variables of copulatory behavior in female meadow vole mating during both PPE and MIE. Females in PPE received significantly fewer intromissions, with shorter intervals between intromissions. Each ejaculatory series was also shorter for females in PPE. As a consequence, the total amount of time devoted to copulation was much shorter for females in PPE than for those in MIE. These data support the hypothesis that female meadow voles are able to reduce their copulatory behavior during PPE.