Abstract: Species of the genus Trachypithecus normally live in groups of less than 20 individuals composed of only one adult male and several adult females (one-male unit). While Indochinese gray langurs (T. crepusculus) live in one male group and multi-male group with less than 30 indiviudals in northeastern Thailand, the conspecific populations in Wuliang Mountain, Yunnan live in large group with up to more than 100 individuals. So far, little is known on detail of the social structure of Indochinese gray langurs in Wuliang Mountain. We studied the social structure of a large habituated group (>70 individuals) of Indochinese gray langurs in Dazhaizi, Wuliang Mountain between September 2012 and July 2015. We selected adult males as focal animal randomly, and then recorded the behavior for other individuals who proximity to the focal male within 5m by 10 minutes interval scanning. Restricted by difficulty of individuals identification, we could only accurately identify age-sex classes of all members staying within 5 m with the focal male in 594 scans in which at least one individual was observed. In 44.2% scans, there was at least one adult male remaining within 5 m to the focal male, with an average of 0.62 ± 0.85 adult males. In 32.5% scans, there were both adult male(s) and adult female(s) remaining within 5 m to the focal male. Most notability, higher frequency (60.0%) and more males (0.93 individuals) were observed surrounding the focal male within 5 m during feeding compared to moving and resting. Our results suggested that the study group did not live in multi-level society that composed of several one-male units and all male units, but live in multimale-multifemale group. Our results also demonstrated that tolerance between adult males in this group was high, especially during feeding. Up to 18 individuals feeding within 5 m to the focal male suggested that food resources were abundant in Wuliang Mountain, at least during certain seasons, which partly explained why Indochinese gray langurs could live in such large groups in the area. We provided preliminary results of social structure of Indochinese gray langurs in Wuliang Mountain which will benefit to better understanding of diversity and evolution of social system of langurs in the future.

Key words: Indochinese gray langur, Social structure, Multimale-multifemale, Wuliang Mountain

摘要： 乌叶猴属物种主要以一雄多雌的小群活动，其群体大小一般不超过20只。泰国东北部的印支灰叶猴生活在一雄多雌或多雄多雌群的小群中，而云南无量山的印支灰叶猴却生活在多雄多雌的大群中，有些群大小超过100只，但是对无量山印支灰叶猴的社会结构缺乏研究。2012年9月至2015年7月，在云南无量山国家级自然保护区大寨子片区开展一群习惯化印支灰叶猴的社会结构研究。采用10min间隔的焦点动物瞬时记录法，记录焦点成年雄性5 m范围内不同性别年龄个体的数量。观察期间共有594次准确识别焦点雄性5 m范围内其它个体年龄性别的有效数据 (至少有1只其他个体)。其中，焦点雄性周围出现其它成年雄性的几率为44.2%，数量为(0.62 ± 0.85)只；同时出现成年雄性和成年雌性的几率是32.5%。取食时焦点雄性周围出现其它雄性的比例 (60.0%) 和数量 (平均0.93只) 都大于休息和移动时，数量最多为5只成年雄性。结果表明该群灰叶猴的社会结构不是由多个OMU和AMU组成的重层社会，而是多雄多雌的社会结构。无量山印支灰叶猴群内成年雄性间相互容忍度较高，个体的空间分布在取食时尤其密集，说明无量山印支灰叶猴的食物丰富 (至少在某些季节)，这也部分解释了为什么无量山印支灰叶猴能够生活在大群中。本文为进一步研究亚洲疣猴社会结构的多样性和进化提供了重要的基础资料。

关键词: 印支灰叶猴, 社会结构, 多雄多雌, 无量山