FEMALE MEADOW VOLES HAVE A PREFERRED MATING PATTERN PREDICTED BY PHOTOPERIOD, WHICH INFLUENCES FERTILITY

In a previous study, Meek and Lee (26) found that female meadow voles mated within three distinct time periods after pairing with a male, an d fertility was influenced by the time of mating and photoperiod. In t he present studies, we tested the hypothesis that different patterns o f mating would correlate with high and low fertility. We found two ver y different patterns of mating were correlated with high fertility. Fe males 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 interintro mission intervals. All long-day females utilizing this mating pattern ovulated, and 86-100% produced litters. We suggest this pattern of mat ing is associated with spontaneous estrus. In contrast to long-day fem ales 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 lon ger interintromission intervals. These short day females all ovulated and 86% produced litters. We suggest that this pattern of mating is as sociated with an induced estrus. Short-day females that did not exhibi t this pattern of mating (66%) produced far fewer litters. We discuss two mechanisms by which fertility may be inhibited in most short-day f emales.