关键词: 西黑冠长臂猿, 雄性取代, 鸣叫行为, 无量山

Abstract: We report a case of male replacement in a free - ranging group of western black crested gibbons (Nomascus concolor) from Wuliang Mountain,Yunnan Province. A subadult male in our study group (G3)begin singing solo bouts in March 2005 when he was about 8 years old. Two years later,in March 2007 at an estimated 10 years of age,this male replaced the resident male in a neighboring group (G2). The original,resident male in G2 disappeared 15 days after the new male joined G2. Before the replacement,G2 produced 5 duet bouts between 10 March and 23 March 2007,but the adult female only produced on average 1.7 great calls in each bout,much lower than the number of great calls in each bout produce by G2 during earlier monitoring between March 2003 and March 2004. We assume that the number of great calls reflects the relationship between adult members in a group. We therefore interpret the relationship between the resident male and two adult females in G2 prior to the replacement as unstable. A serious inter-group conflict between G2 and G3 occurred on March 23,2007. The conflict lasted about 2 hours from 07:50 to 09:50,and the resident male in G2 and G3 chased each other in the overlapped area of their home range. The subadult male in G3 did not join the conflict;we observed him singing in a tree 200 m away from the conflict area from 09:00 to 09:15. After the conflict,the subadult male from G3 joined G2 and began calling on March 26. These calls were accompanied by calls from one or more female (s). The original male produced 2 bouts of singing on 28 March and 6 April;no females responded on the first occasion, but we documented 4 great calls on the second. After 6 April,we never heard the calls of the old resident male in G2. However,from 24 March to 6 April,new male produced 13 bouts. On average,the females produced 2.8 great calls in each duet bout. Geissmann (1986)proposed that in order to concentrate learning time,a newly formed pair should spend more time singing than an established one. Our results support his hypothesis. Compared with the singing behavior of G2 between March 2003 and March 2004,the singing frequency of the new group was significantly higher,whereas the mean number of great calls was significant lower after the replacement. After 4 months,adult females still produced fewer great calls during duet bouts,suggesting that the new male and the two females could not coordinate very well and/ or the relationships between them unstable.

Key words: Male replacement, Singing behavior, Western black crested gibbon (Nomascus concolor), Wuliang Mountain