We investigated the structure and seasonality of the proximity network in a group of polygynous western black crested
gibbons (
Nomascus concolor
) using social network analysis. The spatial proximity changed seasonally and was affected by
temperature and rainfall. Preferred proximity association was not distributed randomly among individuals. Kinship was one
explanation for the social structure, as offspring preferred to maintain close proximity with their mothers. The proximity of infants to
mothers decreased with age, and independent offspring had lower proximity to mothers than dependent ones. We found that the adult
male had different proximity relationships with two different adult females. The frequency of proximity between the male and the
infant-carrying female was significantly higher than that between the male and the female who had immigrated carrying one
offspring of uncertain paternity into the group. Infanticide avoidance and/or predation protection for dependent infants might explain
the proximity relationship differences. Temperature influenced group proximity association, with individual proximity increasing in
the cold months and decreasing in the hot months. Group proximity decreased in months with higher anthropogenic disturbance.