Shennongjia National Nature Reserve, Hubei Province, People's Republic of China.
Am J Primatol. 2011 Dec;73(12):1280-8. doi: 10.1002/ajp.21000. Epub 2011 Sep 6.
Most Old World monkeys show male-biased dispersal. We present the first systematic data on male dispersal in a provisioned multilevel group of Rhinopithecus roxellana, based on 4.5 years of field observations in Shennongjia National Nature Reserve, China. We evaluated both ultimate (inbreeding avoidance and male mating competition) and proximate (food availability and predation risk) factors influencing male dispersal. The focal group contained 34-53 individuals, in 3-4 one-male units (OMUs) and 1 all-male unit (AMU). We observed 37 dispersal events involving 10 of 11 adults, 7 of 8 subadults, and 7 of 15 juveniles. Most interunit transfers within the focal group occurred around the months of mating season. Adult males competed for the leader positions of OMUs mainly through aggressive takeovers, and young males transferred from the OMUs to the AMU at the median age of 41 months, forced out by leader males. No young males older than 4 years remained in natal or non-natal OMUs. The male mating competition hypothesis was supported. The young males emigrated voluntarily from the focal group at the average age of 58.6 months, and no young emigrating male was observed to return, suggesting inbreeding avoidance also played a role in the dispersal of young males. Most emigration/immigration events were parallel dispersal and occurred during intergroup encounters, suggesting increased predation risk during the dispersal period. Males were more likely to emigrate/immigrate during the months when preferred foods were most available. We compared the dispersal patterns in R. roxellana with those in gelada baboons and hamadryas baboons, both living in multilevel societies. Similar to R. roxellana, young male geladas disperse at puberty, but they may return and breed in their natal groups. Males in hamadryas also disperse, but much less commonly than in R. roxellana. Provisioning may have influenced results, and confirming studies on unprovisioned groups would be valuable.
大多数旧大陆猴表现出雄性偏向的扩散。我们基于在中国神农架国家自然保护区进行的 4.5 年实地观察，首次提供了关于圈养的川金丝猴（Rhinopithecus roxellana）雄性扩散的系统数据。我们评估了影响雄性扩散的终极（避免近亲繁殖和雄性交配竞争）和近因（食物可获得性和捕食风险）因素。焦点群包含 34-53 只个体，分为 3-4 个一雄多雌单元（OMU）和 1 个全雄单元（AMU）。我们观察到 37 次扩散事件，涉及 11 只成年个体中的 10 只、8 只亚成年个体中的 7 只和 15 只幼体中的 7 只。大多数在焦点群内的单元间转移发生在交配季节的月份。成年雄性主要通过攻击性接管争夺 OMU 的领导地位，而年轻雄性在 41 个月的平均年龄时从 OMU 转移到 AMU，被领导雄性驱逐。没有 4 岁以上的年轻雄性留在出生或非出生的 OMU。雄性交配竞争假说得到支持。年轻雄性在平均 58.6 个月的年龄时自愿离开焦点群，没有观察到年轻的移民雄性返回，这表明避免近亲繁殖也在年轻雄性的扩散中发挥了作用。大多数移民/移民事件是平行扩散，发生在群体间相遇期间，这表明在扩散期间捕食风险增加。雄性更有可能在食物最充足的月份进行移民/移民。我们将川金丝猴的扩散模式与生活在多层次社会中的狒狒和山魈的扩散模式进行了比较。与川金丝猴类似，年轻的雄性狒狒在青春期时扩散，但它们可能会返回并在其出生群体中繁殖。山魈的雄性也会扩散，但比川金丝猴少得多。提供食物可能会影响结果，对未提供食物的群体进行确认研究将是有价值的。
