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Ejaculate disruption in two species of voles (Microtus): on the PEI matching law

D A Dewsbury1, S M Bauer, J D Pierce

  • 1Department of Psychology, University of Florida, Gainesville 32611-2065.

Journal of Comparative Psychology (Washington, D.C. : 1983)
|December 11, 1992
PubMed

Insights

Sperm transport in voles is disrupted by subsequent mating attempts shortly after ejaculation. This disruption lasts longer in voles than in rats or deer mice, challenging existing reproductive theories.

Area of Science:

  • Reproductive Biology
  • Behavioral Ecology
  • Mammalian Reproduction

Background:

  • Sperm competition is a key factor in mammalian reproductive success.
  • Post-ejaculatory intervals (PEI) may play a role in preventing sperm displacement by subsequent males.
  • Voles (Microtus ochrogaster and M. montanus) provide a model for studying sperm competition dynamics.

Purpose of the Study:

  • To investigate the impact of post-ejaculatory mating thrusts on sperm transport in prairie and montane voles.
  • To determine the duration of susceptibility to sperm displacement in these vole species.
  • To test the applicability of the PEI matching law to vole reproductive behavior.

Main Methods:

  • Male voles received controlled mating thrusts (without ejaculation) at varying intervals after a conspecific's ejaculation.
  • Sperm presence in the female reproductive tract was quantified 1 hour post-ejaculation.
  • Litter production was monitored in prairie voles to assess reproductive consequences.

Main Results:

  • Subsequent thrusts within 15 minutes of ejaculation significantly reduced sperm presence in the female tract for both vole species.
  • This disruptive effect on sperm transport was not observed after a 50-minute delay.
  • No significant reduction in litter size was observed in prairie voles subjected to immediate or 15-minute delayed thrusts.

Conclusions:

  • Sperm transport in prairie and montane voles is vulnerable to disruption for a prolonged period compared to other rodents like deer mice or rats.
  • The findings suggest that the PEI matching law, which posits that males adjust their mating intervals to protect their sperm, may not apply to these vole species.
  • Further research is needed to understand the specific mechanisms and evolutionary implications of prolonged post-ejaculatory vulnerability in voles.

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