The ecology and behavior of one group（G2）of western black crested gibbon（Nomascus concolor）was studied from Jannuary 2008 to December 2011 at Dazhaizi（24°21’N，100°42’E）, Mt. Wuliang, central Yunnan, China. The group was habituated until December 2010. From then on, an annual ecological and behavioral observation were conducted for from January to December 2011 and obtained a total of 610-hour’s data by instantaneous scan sampling on diet, activity budget, duet, grooming behavior, spatial proximity, intra- and inter- group agonism. We intend to know how the group adapted to the different habitat behaviorally and study the social structure of the polygynous group of western black crested gibbon by using social network analysis. The behavioral data were collected by instantaneous scan sampling at a 5-min interval. We collected 19274 behavior records in total. The Gibbons spent most of the time in moving（33.12 %）, feeding（27.19 %）and resting（26.88 %）. Time budget of the study group differed significantly among months, age, and between sex. The feeding time increased when monthly mean temperature was high. Seventy different plants provided food for the gibbons. The diet of group varied monthly significantly, but not between individuals. Compared with the neighbor group（G3, referred from Huang，2011）, we found that G2 spent more time in moving than G3, and two groups’ diet differed significantly. The result showed that gibbons used different feeding strategies for different habitat in their home range to increase fitness. We firstly used social network analysis to study the grooming network in gibbon’s group. Our results showed that the stable group had a more complex grooming network while the group with newly replaced individuals had a simpler network. Moreover, newly immigrated female had the most extensive grooming and chose the resident adult female as her first grooming partner（except her offspring）. Our observations indicated the grooming network was relative to the group dynamic and reflected the change of individuals within the groups. We hypothesize that the immigrant female gave more extensive grooming as an important behavioral strategy in order to achieve the tolerance from the permanent residents as a way to solidify their social status. Social network analysis was also used to investigate the structure and seasonality of the proximity network in our study group, and we analyzed the impact of temperature and rainfall. 31013 proximity records were collected in total. The individual proximity increased in the cold months and decreased in hot months with higher anthropogenic disturbance. Kinship was one explanation for the gibbons’ group social structure, as the offspring preferred to keep proximity with their mothers. The proximity of infant with its mother decreased while it grew up, and the independent offspring have lower proximity to mothers than dependent one. We found that adult male had different proximity relationship with two adult females. We proposed that infanticide avoidance and/or predation protection for dependent infant could be possible reason for the proximity relationship difference. We found gibbons’ duet behavior（duet frequency and great calls by two females synchronously）became more frequent when monthly group proximity was high. This feature supports the group cohesion function hypothesis of duet behavior.During study period, we also observed 38 cases of intra-group agonistic behavior, all but one cases we can identify individuals. According to the behavior difference between individuals, we suggest that male intra-sex competition and extra-pair copulations were the main reason for inter-group encounters.
修改评论