中文摘要：

本文通过长时间的野外监测,首次报道了西黑冠长臂猿的一次雄性取代行为。一个研究群体（G3）中的1只亚成年雄性长臂猿在10岁左右取代了相邻群体（G2）中的成年雄性。整个取代过程持续了15d时间。雄性取代发生前,G2中雌雄的配对关系已经不稳固,这为雄性取代提供了机会。而G2与G3群的一次长时间冲突可能消耗了G2中成年雄性大量体能,这为G3中的亚成年雄性打败并取代G2中的成年雄性创造了机会。本研究在取代发生后,对新形成群体的鸣叫行为进行了连续4个月的监测。结果表明与处于稳定时期的G2群相比,新形成群体的鸣叫频次更高,但每次二重唱中雌性的平均激动鸣叫次数降低。这证明了Geissmann（1986）提出的假说,新配对的群体应该在尽量短的时间内多练习二重唱,这样导致新配对群体的鸣叫频率明显升高。虽然经历了4个月的合唱练习,新形成群体的激动鸣叫次数仍然偏低,并且两只雌性同时激动鸣叫的频次也比较低。这说明新形成的配对之间配合依然不默契,或者说明配对之间的关系还不稳定。

英文摘要：

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. O