van Leeuwen Edwin J C, Cronin Katherine A, Haun Daniel B M
Max Planck Institute for Psycholinguistics, Max Planck Institute for Evolutionary Anthropology, PO Box 310, 6500 AH, Nijmegen, The Netherlands,
Anim Cogn. 2014 Nov;17(6):1421-5. doi: 10.1007/s10071-014-0766-8. Epub 2014 Jun 11.
Social learning in chimpanzees has been studied extensively and it is now widely accepted that chimpanzees have the capacity to learn from conspecifics through a multitude of mechanisms. Very few studies, however, have documented the existence of spontaneously emerged traditions in chimpanzee communities. While the rigour of experimental studies is helpful to investigate social learning mechanisms, documentation of naturally occurring traditions is necessary to understand the relevance of social learning in the real lives of animals. In this study, we report on chimpanzees spontaneously copying a seemingly non-adaptive behaviour ("grass-in-ear behaviour"). The behaviour entailed chimpanzees selecting a stiff, straw-like blade of grass, inserting the grass into one of their own ears, adjusting the position, and then leaving it in their ear during subsequent activities. Using a daily focal follow procedure, over the course of 1 year, we observed 8 (out of 12) group members engaging in this peculiar behaviour. Importantly, in the three neighbouring groups of chimpanzees (n = 82), this behaviour was only observed once, indicating that ecological factors were not determiners of the prevalence of this behaviour. These observations show that chimpanzees have a tendency to copy each other's behaviour, even when the adaptive value of the behaviour is presumably absent.
黑猩猩的社会学习已经得到了广泛研究，现在人们普遍认为黑猩猩有能力通过多种机制向同类学习。然而，很少有研究记录在黑猩猩群体中自发出现的传统行为。虽然实验研究的严谨性有助于探究社会学习机制，但记录自然发生的传统行为对于理解社会学习在动物实际生活中的相关性是必要的。在这项研究中，我们报告了黑猩猩自发模仿一种看似非适应性的行为（“草塞耳行为”）。这种行为包括黑猩猩挑选一根硬的、稻草状的草叶，将草插入自己的一只耳朵，调整位置，然后在随后的活动中一直将其留在耳朵里。我们采用每日焦点跟踪程序，在一年的时间里，观察到12只群体成员中有8只出现了这种奇特行为。重要的是，在相邻的三组黑猩猩（共82只）中，这种行为只观察到过一次，这表明生态因素并不是这种行为普遍存在的决定因素。这些观察结果表明，黑猩猩有相互模仿行为的倾向，即使这种行为可能不存在适应性价值。
