Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK.
Proc Biol Sci. 2022 Oct 26;289(1985):20221653. doi: 10.1098/rspb.2022.1653.
Predation is a powerful selective pressure and probably a driver of why many animal species live in groups. One key explanation for the evolution of sociality is the 'selfish herd' model, which describes how individuals who stay close to others effectively put neighbours between themselves and a predator to survive incoming attacks. This model is often illustrated with reference to herds of ungulates, schools of fish or flocks of birds. Yet in nature, when a predator strikes, herds are often found fleeing cohesively in the same direction, not jostling for position in the centre of the group. This paper highlights a critical assumption of the original model, namely that prey do not move in response to position of their predator. In this model, I relax this assumption and find that individuals who adopt 'selfish herd' behaviour are often more likely to be captured, because they end up at the back of a fleeing herd. By contrast, individuals that adopt a rule of 'neighbour to neighbour alignment' are able to avoid rearmost positions in a moving herd. Alignment is more successful than selfish herding across much of the parameter space, which may explain why highly aligned fleeing behaviour is commonly observed in nature.
捕食是一种强大的选择压力，可能是许多动物物种群居的原因之一。群居性进化的一个关键解释是“自私的羊群”模型，该模型描述了个体如何通过靠近其他个体，将邻居置于自己和捕食者之间，从而有效地在来袭的攻击中幸存下来。该模型通常通过引用有蹄类动物的牧群、鱼类的鱼群或鸟类的鸟群来举例说明。然而，在自然界中，当捕食者袭击时，经常会发现牧群会一致地朝着同一个方向逃跑，而不是在群体中心争抢位置。本文强调了原始模型的一个关键假设，即猎物不会根据其捕食者的位置而移动。在这个模型中，我放松了这个假设，发现采取“自私的羊群”行为的个体往往更容易被捕食，因为它们最终会处于逃跑羊群的后面。相比之下，采取“邻居对邻居对齐”规则的个体能够避免在移动的羊群中处于最后面的位置。对齐在很大的参数空间中比自私的放牧更成功，这可能解释了为什么在自然界中经常观察到高度对齐的逃跑行为。
