Female meadow voles have a preferred mating pattern predicted by photoperiod, which influences fertility.

In a previous study, Meek and Lee found that female meadow voles mated within three distinct time periods after pairing with a male, and fertility was influenced by the time of mating and photoperiod. In the present studies, we tested the hypothesis that different patterns of mating would correlate with high and low fertility. We found two very different patterns of mating were correlated with high fertility. Females housed in long daylengths (long day; 14 h light/day) and mating within 48 h of pairing with a male, received few mounts, intromissions, and intromissions per ejaculatory series, with very short interintromission intervals. All long-day females utilizing this mating pattern ovulated, and 86-100% produced litters. We suggest this pattern of mating is associated with spontaneous estrus. In contrast to long-day females mating within 48 h, females housed in short daylengths (short day; 10 h light/day) and mating between 14-48 h after pairing with a male, received significantly more short mounts and intromissions, with longer interintromission intervals. These short day females all ovulated and 86% produced litters. We suggest that this pattern of mating is associated with an induced estrus. Short-day females that did not exhibit this pattern of mating (66%) produced far fewer litters. We discuss two mechanisms by which fertility may be inhibited in most short-day females.