Seasonal variation in fertility in female meadow voles (Microtus pennsylvanicus).

These experiments explore how, in the laboratory, a small, short-lived rodent, the meadow vole, behaviorally controls fertility. Meadow voles inhabit an unpredictable niche, which suggests that facultative responses to environmental cues should have evolved in this species. These studies explore the behavioral and physiological mechanisms that meadow voles exhibit which influence reproductive success. In Chapter 2, the effects of diet on development in juvenile meadow voles with three different maternal photoperiod histories is examined. Chapter 3 reports on mating latency, fertility and spontaneous behavioral estrus in nulliparous and multiparous female meadow voles in long (14 hr light/day) and short (10 hr light/day) photoperiods. Chapter 4 correlates mating patterns and photoperiod with fertility in nulliparous females. Chapter 5 investigates whether the vomeronasal organ is necessary for the expression of behavioral estrus in nulliparous females, and Chapter 6 explores LH and prolactin in females with different mating latencies and fertility in long and short photoperiods. These experiments demonstrate that fertility in meadow voles is controlled by a variety of mechanisms and suggests a possible scenario for field animals. Juveniles respond to the presence of green food with developmental acceleration. Females in long daylengths have spontaneous behavioral estrus and mate quickly ($$85% give birth. For multiparous females, short daylengths do not turn off reproductive responses. Many virgin females respond to short daylengths with reproductive suppression. They mate late ($>$56 hours), 40% do not ovulate and few produce litters. Some females in short photoperiods mate quickly ($<$9 hours), 100% ovulate, but only 50% produce litters, probably due to a failure to maintain elevated prolactin. Only females in short photoperiods which mate between 14-48 hours after pairing exhibit mating behavior which results in both a LH surge and sustained prolactin, since 86% produce litters. These experiments demonstrate that meadow voles are facultative breeders, and respond to changes in photoperiod and food quality with a variety of behavioral and physiological mechanisms which influence fertility.PhDPsycho logyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104002/1/9423267.pdfDescription of 9423267.pdf : Restricted to UM users only