Male Reproductive Success And The Mating System Of Bushy-tailed Woodrats

Bushy-tailed woodrats are nocturnal cricetid rodents distributed throughout the mountainous regions of western North America. Despite a number of studies on the population ecology of this species, little is known about the behaviour of males during the breeding season.;I investigated the reproductive behaviour of male bushy-tailed woodrats in three ways. First, I examined the spatial distribution of individuals within a breeding population, using radiotelemetry and mark-recapture livetrapping. Both males and females exhibited considerable overlap with animals of both sexes, mean intersexual and intrasexual overlap values for each sex did not differ in two of the three years of study. This pattern of overlap is more indicative of a promiscuous mating system, than of harem polygyny, which had previously been suggested for this species.;Second, I examined the pattern of reproductive success among breeding males, using DNA fingerprinting to determine paternity of all juveniles. No multiple paternity within litters was observed in all years of study. Male woodrats appeared to gain matings by sequestering females throughout estrus, but were unable to restrict access to more that one female at a time. The distribution of male reproductive success, coupled with the spatial overlap of the population, suggests that bushy-tailed woodrats exhibit a roving-male promiscuous mating system.;Third, I investigated the manner in which male woodrats compete for access to females. I examined the relationship between male reproductive success and male characteristics that would be favoured under differing mechanisms of male intrasexual competition. Traits associated with scramble, reproductive endurance, and contest competition showed no significant correlations with reproductive success. However, traits associated with choice by females and sperm competition showed significant correlations with male reproductive success.;I conclude that woodrats exhibit a promiscuous mating system where males attempt to sequester females to ensure paternity of the litters. This male mating strategy is most likely favoured in woodrats due to the short, asynchronous, periods of estrus, and the large, unpredictable, movements of females