Higher rates of dispersal in one sex than the other are widespread, and often attributed to the genetic advantages of reduced inbreeding. The direction of sex-biased dispersal shows strong phylogenetic conservatism (e.g. males disperse more than females in most mammals, but the reverse is true in most birds). By contrast, our genetic data reveal strong inter-population variation in the relative dispersal rates of two species of sea snakes (Laticauda saintgironsi and L. laticaudata) in the Noumea Lagoon of New Caledonia. Assignment methods using microsatellite data identified parallel variation in sex-specific dispersal in both species: dispersal was female-biased in the north-west of the sampling area (in islands far from the main island), but male-biased in the south-east (in islands closer to the main island). This flexibility may reflect sex differences in diets, with spatial variation in sex-specific resources generating spatial variation in sex-specific dispersal distances.