Sex-biased dispersal is common in most mammals, but a female bias is less so and exceptionally rare in solitary mammals. Here we present genetic and observational evidence for strong female-biased dispersal in a solitary foraging small carnivore, the slender mongoose. We suggest that females benefit from dispersal by avoiding kin competition over local resources and inbreeding, while males can benefit from philopatry through kin cooperation leading to an increased success in female defence. The comparison between our observations and those of a previous study in Tanzania suggest that there is ecologically influenced flexibility in dispersal patterns within this species, influencing sex-specific benefits of dispersal and philopatry. Comparing our results with those on the closely related, more social mongoose species in which both sexes commonly disperse suggests that dispersal patterns are linked to a species' social system by the opportunity, or lack of it, in philopatry to obtain unrelated mating partners and gain indirect fitness benefits.