Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, Stony Brook, NY 11794-4363, USA.
Am J Primatol. 2012 Jul;74(7):613-21. doi: 10.1002/ajp.22013.
Previous work on mammals and birds has often demonstrated a negative relationship between group size and individual vigilance. However, this relationship has received only weak support in nonhuman primates. This result may be due to the failure to distinguish different forms of vigilance such as antipredatory vigilance and social monitoring. Here, we tested the effects of group size, reproductive status (breeding vs. nonbreeding), and sex on antipredatory vigilance and social monitoring in captive common marmosets (Callithrix jacchus). Behavioral observations using one-zero sampling were conducted on adult members of three captive groups of small, medium, and large size. Data were analyzed using a series of general linear models (GLMs) analyses of covariance (ANCOVAs). We found an overall negative group size effect on antipredatory vigilance and that breeders, especially breeding males, were significantly more vigilant than nonbreeders. Conversely, we found that social monitoring increased with group size. Unlike the results for antipredatory vigilance, neither breeders and nonbreeders nor males and females differed in their amounts of social monitoring. However, the effect of group size appeared to differ for nonbreeding males compared to all other adults. Our results generally support the idea that individuals in larger groups are safer with breeding males likely playing a prominent role in protection from predation. The increase in social monitoring may be related to increased reproductive competition with the presence of adult offspring, but future studies need to clarify the target of social monitoring in both breeders and nonbreeders. Overall, the study underlines the importance of distinguishing different forms of vigilance and other factors as they may confound the effects of group size on antipredatory vigilance.
先前关于哺乳动物和鸟类的研究工作常常表明，群体大小与个体警戒之间呈负相关关系。然而，这种关系在非人类灵长类动物中仅得到了微弱的支持。这一结果可能是由于未能区分不同形式的警戒，如捕食警戒和社会监测。在这里，我们测试了群体大小、繁殖状态（繁殖与非繁殖）和性别对圈养普通狨（Callithrix jacchus）捕食警戒和社会监测的影响。使用零一采样法对三个大小不同的圈养群体的成年成员进行了行为观察。使用一系列协方差分析的一般线性模型（GLMs）对数据进行了分析。我们发现，捕食警戒总体上呈现出负向的群体大小效应，并且繁殖者，尤其是繁殖雄性，比非繁殖者更为警觉。相反，我们发现社会监测随着群体大小的增加而增加。与捕食警戒的结果不同，繁殖者和非繁殖者以及雄性和雌性在社会监测量上没有差异。然而，非繁殖雄性的群体大小效应似乎与其他成年个体不同。我们的研究结果总体上支持这样一种观点，即较大群体中的个体更安全，而繁殖雄性可能在保护免受捕食方面发挥着突出作用。社会监测的增加可能与繁殖竞争的增加有关，因为有成年后代的存在，但未来的研究需要澄清繁殖者和非繁殖者的社会监测的目标。总的来说，这项研究强调了区分不同形式的警戒和其他因素的重要性，因为它们可能会混淆群体大小对捕食警戒的影响。
