Rands Sean A, Cowlishaw Guy, Pettifor Richard A, Rowcliffe J Marcus, Johnstone Rufus A
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
BMC Evol Biol. 2008 Feb 18;8:51. doi: 10.1186/1471-2148-8-51.
Foraging in groups offers animals a number of advantages, such as increasing their likelihood of finding food or detecting and avoiding predators. In order for a group to remain together, there has to be some degree of coordination of behaviour and movement between its members (which may in some cases be initiated by a decision-making leader, and in other cases may emerge as an underlying property of the group). For example, behavioural synchronisation is a phenomenon where animals within a group initiate and then continue to conduct identical behaviours, and has been characterised for a wide range of species. We examine how a pair of animals should behave using a state-dependent approach, and ask what conditions are likely to lead to behavioural synchronisation occurring, and whether one of the individuals is more likely to act as a leader.
The model we describe considers how the energetic gain, metabolic requirements and predation risks faced by the individuals affect measures of their energetic state and behaviour (such as the degree of behavioural synchronisation seen within the pair, and the value to an individual of knowing the energetic state of its colleague). We explore how predictable changes in these measures are in response to changes in physiological requirements and predation risk. We also consider how these measures should change when the members of the pair are not identical in their metabolic requirements or their susceptibility to predation. We find that many of the changes seen in these measures are complex, especially when asymmetries exist between the members of the pair.
Analyses are presented that demonstrate that, although these general patterns are robust, care needs to be taken when considering the effects of individual differences, as the relationship between individual differences and the resulting qualitative changes in behaviour may be complex. We discuss how these results are related to experimental observations, and how the model and its predictions could be extended.
群体觅食为动物带来诸多优势，比如增加找到食物的可能性，或发现并躲避捕食者。为使群体保持在一起，其成员之间必须存在一定程度的行为和行动协调（在某些情况下可能由决策领导者发起，而在其他情况下可能作为群体的一种潜在特性出现）。例如，行为同步是一种群体内动物开始并持续进行相同行为的现象，已在众多物种中得到描述。我们使用一种状态依赖方法来研究一对动物应如何表现，并探讨哪些条件可能导致行为同步的发生，以及其中一个个体是否更有可能充当领导者。
我们所描述的模型考虑了个体面临的能量获取、代谢需求和捕食风险如何影响它们的能量状态和行为指标（例如在这对动物中观察到的行为同步程度，以及个体了解其同伴能量状态的价值）。我们探究这些指标的可预测变化如何响应生理需求和捕食风险的变化。我们还考虑当这对动物的成员在代谢需求或对捕食的易感性方面不相同时，这些指标应如何变化。我们发现这些指标中观察到的许多变化都很复杂，尤其是当这对动物的成员之间存在不对称性时。
所呈现的分析表明，尽管这些一般模式是稳健的，但在考虑个体差异的影响时需要谨慎，因为个体差异与行为产生的定性变化之间的关系可能很复杂。我们讨论这些结果如何与实验观察相关，以及该模型及其预测如何能够得到扩展。
