Changes in behaviour following a 'rank changeover by challenge' in the Nicobar long-tailed macaque (Macaca fascicularis umbrosus)

A rank changeover is a sexual strategy by primate males to gain access to reproductive females. We observed one such event in the Nicobar long-tailed macaque (Macaca fascicularis umbrosus) at the Great Nicobar Island, India. In the three and half months of the post-rank changeover period, the home range reduced significantly while there was no change in the intensity of range use and day range length. The sleeping sites in the post-rank changeover period were confined to the centre of the home range. The overall mating rate and aggressive mating approach by males increased significantly during the post-rank changeover period. The females developed sexual swelling and started soliciting the immigrated males within two weeks after the rank changeover event. During this period no female conceived, which suggests that they used situation-dependent receptivity with deceptive swelling as a counter strategy to avoid male aggression for copulation.