Mating success of male bushy-tailed woodrats: when bigger is not always better

To determine the factors that regulate mating opportunities of male bushy-tailed woodrats (Neotoma cinerea), we used stepwise multiple regression on measurable morphological and behavioral traits. DNA fingerprinting was used to determine the paternity of juveniles, allowing mating success (the number of females mated with), and reproductive success (the number of offspring fathered) to be quantified. Both measures of male success were significantly related to the growth rate of males while reproductively active. The most successful males were those that had higher growth rates, indicating that there is relatively little cost (weight loss) associated with successful mating in male woodrats. Our findings demonstrate that although this species is highly sexually dimorphic, large body size does not influence mating success. In addition, it appears that male mating success cannot be predicted from morphological measures and may instead be determined by behavioral or olfactory cues.