Animals use social information, available from conspecifics, to learn and express novel and adaptive behaviours. Amongst social learning mechanisms, response facilitation occurs when observing a demonstrator performing a behaviour temporarily increases the probability that the observer will perform the same behaviour shortly after. We studied “robbing and bartering” (RB), two behaviours routinely displayed by free-ranging long-tailed macaques (Macaca fascicularis) at Uluwatu Temple, Bali, Indonesia. When robbing, a monkey steals an inedible object from a visitor and may use this object as a token by exchanging it for food with the temple staff (bartering). We tested whether the expression of RB-related behaviours could be explained by response facilitation and was influenced by model-based biases (i.e. dominance rank, age, experience and success of the demonstrator). We compared video-recorded focal samples of 44 witness individuals (WF) immediately after they observed an RB-related event performed by group members, and matched-control focal samples (MCF) of the same focal subjects, located at similar distance from former demonstrators (N = 43 subjects), but in the absence of any RB-related demonstrations. We found that the synchronized expression of robbing and bartering could be explained by response facilitation. Both behaviours occurred significantly more often during WF than during MCF. Following a contagion-like effect, the rate of robbing behaviour displayed by the witness increased with the cumulative rate of robbing behaviour performed by demonstrators, but this effect was not found for the bartering behaviour. The expression of RB was not influenced by model-based biases. Our results support the cultural nature of the RB practice in the Uluwatu macaques.

中文翻译：

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社会对巴厘岛长尾猕猴抢劫和易货行为表达的影响

动物使用可从特定物种获得的社会信息来学习和表达新颖的适应性行为。在社交学习机制中，观察演示者执行某项行为会临时增加响应，这会增加观察者不久后将执行同一行为的可能性。我们研究了“抢劫与易货”（RB），这是印度尼西亚巴厘岛乌鲁瓦图庙（Uluwatu Temple）放飞长尾猕猴（Macaca fascicularis）经常表现出的两种行为。当抢劫，猴抢断访客不可食用的对象，并且可以通过与寺庙工作人员兑换成食品用这个对象作为一个令牌（实物交易）。我们测试了是否可以通过响应促进来解释RB相关行为的表达，并且是否受基于模型的偏见（即，支配者的主导地位，年龄，经验和成功）的影响。我们比较了44名见证人（WF）在观察到小组成员进行的RB相关事件后的视频记录焦点样本，以及相同焦点对象的匹配控制焦点样本（MCF），这些焦点样本距前示威者的距离相似（N = 43个主题），但没有任何与RB相关的演示。我们发现抢劫和易货的同步表达可以通过响应促进来解释。两种行为在WF期间发生的频率比在MCF期间发生的频率高得多。在发生类似传染的影响之后，证人表现出的抢劫行为比率随着示威者执行的累计抢劫行为比率而增加，但是这种结果在交换行为中并未发现。RB的表达不受基于模型的偏差的影响。我们的结果支持乌鲁瓦图猕猴的RB实践的文化性质。