Hsu Minna J, Lin Jin-Fu, Agoramoorthy Govindasamy
Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, 804, Taiwan.
College of Pharmacy and Health Care, Tajen University, Yanpu, 907, Taiwan.
Primates. 2017 Apr;58(2):323-334. doi: 10.1007/s10329-016-0594-3. Epub 2017 Jan 2.
Group fission in non-human primates has long been proposed to result from interactions between ecological and social factors. Several studies have documented possible causes for group fission, but its proximate causes and ultimate adaptive values are not yet fully understood. We have examined the existing hypotheses on fission from long-term demographic data of Formosan macaques inhabiting the lowland rainforest at Mt Longevity, Taiwan. Five cases of fission occurred in four social groups. We have recorded two types of fission: one involving the separation of a high-ranking adult male and multiple adult females, the other initiated by adult females from main groups. Five adult females immigrated and emigrated a few times between the main and branch groups (oscillation) in three fission events. Data presented in this study are consistent with the prediction that low-ranking females split from main groups when their fitness costs increase due to ecological pressure or population growth. However, their reproductive success may decrease after fission due to a high rate of intra-group competition. Nevertheless, it is beneficial for males to be involved in fission since this increases reproductive benefits by decreasing the sex ratio in small newly formed groups.
长期以来，人们一直认为非人类灵长类动物群体分裂是生态因素和社会因素相互作用的结果。多项研究记录了群体分裂的可能原因，但其直接原因和最终适应价值尚未完全明确。我们根据台湾长寿山低地雨林中台湾猕猴的长期种群数据，对现有的群体分裂假说进行了研究。四个社会群体中发生了五起群体分裂事件。我们记录了两种类型的分裂：一种是由一只高等级成年雄性和多只成年雌性分离导致的，另一种是由主群体中的成年雌性引发的。在三次分裂事件中，有五只成年雌性在主群体和分支群体之间多次迁入和迁出（振荡）。本研究中呈现的数据与以下预测一致：当低等级雌性因生态压力或种群增长导致其适应成本增加时，它们会从主群体中分裂出去。然而，由于群体内部竞争激烈，它们在分裂后的繁殖成功率可能会降低。尽管如此，雄性参与分裂是有益的，因为这通过降低新形成的小群体中的性别比例增加了繁殖收益。
