Aplin L M, Morand-Ferron J
Edward Grey Institute of Field Ornithology, University of Oxford, Oxford OX1 3PS, UK
Department of Biology, University of Ottawa, Ottawa, Canada K1N 6N5.
Proc Biol Sci. 2017 Apr 12;284(1852). doi: 10.1098/rspb.2016.2872.
There has been extensive game-theoretic modelling of conditions leading to equilibria of producer-scrounger dichotomies in groups. However there is a surprising paucity of experimental evidence in wild populations. Here, we examine producer-scrounger games in five subpopulations of birds feeding at a socially learnt foraging task. Over four weeks, a bimodal distribution of producers and scroungers emerged in all areas, with pronounced and consistent individual tactic specialization persisting over 3 years. Tactics were unrelated to exploratory personality, but correlated with latency to contact and learn the foraging task, with the late arrivers and slower learners more likely to adopt the scrounging role. Additionally, the social environment was also important: at the broad scale, larger subpopulations with a higher social density contained proportionally more scroungers, while within subpopulations scroungers tended to be central in the social network and be observed in larger foraging flocks. This study thus provides a rare example of a stable, dimorphic distribution of producer-scrounger tactics in a wild population. It further gives support across multiple scales for a major prediction of social foraging theory; that the frequency of scroungers increases with group size.
针对导致群体中生产者 - 窃取者二分法达到平衡的条件，已有大量的博弈论模型。然而，野生种群中的实验证据却惊人地匮乏。在此，我们研究了在一项通过社会学习的觅食任务中进食的五个鸟类亚种群中的生产者 - 窃取者博弈。在四周的时间里，所有区域都出现了生产者和窃取者的双峰分布，并且这种明显且一致的个体策略专业化持续了三年多。策略与探索性人格无关，但与接触和学习觅食任务的潜伏期相关，较晚到达者和学习较慢者更有可能采用窃取角色。此外，社会环境也很重要：在宏观层面，社会密度较高的较大亚种群中，窃取者的比例相对更高，而在亚种群内部，窃取者往往处于社会网络的中心位置，并且在较大的觅食群体中更容易被观察到。因此，本研究提供了一个野生种群中生产者 - 窃取者策略稳定、二态分布的罕见例子。它还在多个层面上支持了社会觅食理论的一个主要预测；即窃取者在群体中的比例会随着群体规模的增加而上升。
