We investigated scent marking behaviour in the yellow mongoose Cynictis penicillata, focusing on a low-density population where all offspring dispersed upon reaching sexual maturity. Dominant males appeared to be the main territory defenders and demarcators, with offspring foraging and marking only near the territory cores. The cheek-marking rates of dominant males increased during the breeding season and may have been involved in olfactory mate guarding. We compared our low-density population with a high-density population displaying natal philopatry. The two populations differed markedly in terms of individual contributions to territorial marking, as subordinate group members in the low-density population performed almost no territorial marking or defence, but were the primary scent-markers and territory defenders in the high-density population. We discuss scent-marking distinctions between populations in the context of ecological and social differences.