The Mating System of the Prairie Vole, Microtus-Ochrogaster - Field and Laboratory Evidence for Pair-Bonding

Abstract

1. Field and experimental evidence is provided for the existence of pair-bonding or monogamy in prairie voles (Microtus ochrogaster).
2. Multiple-capture live-trap data indicated that male and female pairs of M. ochrogaster were repeatedly captured together. (A comparable analysis for data from M. pennsylvanicus revealed no indications of long-term male-female associations.)
3. Male-female pair captures of M. ochrogaster were equally likely during either the breeding or nonbreeding seasons, further suggesting a relative stability of pairs.
4. In laboratory dyadic encounters, both males and females from breeding pairs tended to show relatively high levels of aggression toward unfamiliar animals of the opposite sex. In contrast, aggression was rarely observed between members of established breeding pairs. Nonpaired animals of either sex infrequently initiated aggressive encounters.
5. When pairs were separated for 8 days (during which time the females lived with a new male) the apparent pair-bond with the original male was broken. These females became aggressive toward the male with which they had previously bred, and rarely fought with their new mate. This suggests that the pair-bonding process is reversible.
6. Females in postpartum estrus preferentially showed high levels of sexual receptivity and low levels of aggression toward familiar males and were less likely to mate with unfamiliar sexually experienced males. The presence of pups at the time of testing did not appear to influence female-initiated aggression.