The adaptive significance of multiple mating in female mink (Mustela vison) and its effects on the mating system \ by Melissa Anne Fleming

Thesis (Ph. D.)--University of Washington, 1996Female multiple mating is common in mammals, but studies of its advantages are often constrained by our limited understanding of the reproductive physiology underlying it. The reproductive physiology underlying female multiple mating in the American mink (Mustela vison) is well-known, but this is the first study to focus on the functions of female multiple mating and its possible effects on the mating system.Multiple mating by female mink has different effects depending on the interval between matings. Matings at eight day intervals (8DI) during delayed implantation induce additional ovulations while matings at one day intervals (1DI) around ovulation promote sperm competition. To determine female mating preferences and males' response, I gave fur farm females opportunities to remate at 1DI and/or 8DI with the same male (familiar) and/or unfamiliar males.Females mated multiply in the absence of male coercion. Females remated after eight days regardless of male familiarity, possibly because females that experience only matings early breeding season are more often barren. For familiar pairs at the 1DI, males showed less interest in remating than females did, which led to females mating different males on consecutive days and to their fecundity not being reduced when one male was infertile. Allozyme electrophoresis confirmed the paternity advantage of males mating around later ovulations and showed a first male advantage in consecutive day matings.Copulation duration increases over the course of the breeding season beyond what is necessary to induce ovulation and achieve fertilization. Copulation duration increased for unfamiliar pairs and pairs that had last mated more than a week before, but not for pairs that had mated the previous day--further illustrating the decreased interest of familiar males at the 1DI and suggesting that prolonging copulation is a male strategy in sperm competition.Wild-caught Mustela vison evagor mated in May rather than March, but otherwise showed multiple mating behavior similar to fur farm mink. Female mink may multiply mate during delayed implantation to insure maximum fecundity and to increase offspring quality by increasing opportunities for male-male competition and mate choice