Causes of natal dispersal in a monogamous ungulate, the Japanese serow, Capricornis crispus

We examined two hypotheses to explain the natal dispersal of Japanese serows: competition for mates and/or resources and inbreeding avoidance. We predicted that if the competition hypothesis were valid, serow offspring would disperse when the same-sex but not opposite-sex parent was present, whereas if the inbreeding avoidance hypothesis were valid, the opposite would apply. Only adult males were aggressive, and only to male offspring; this aggression may have led to offspring dispersing, although, over the 29-year study, no significant sex difference was found in the dispersal rate, mean age at dispersal or dispersal distance. All philopatric offspring, one male and two females, remained in the natal home ranges after the disappearance of the same-sex parent or territorial resident, and all 30 dispersals of both sexes occurred when the same-sex parent or territorial resident was present in the natal home ranges. Four male and five female offspring, however, left the natal home ranges after their opposite-sex parent had already disappeared. These results suggest that serow dispersal can be explained by the competition hypothesis.