Department of Zoology, University of Oxford, Tinbergen Building, South Parks Road, Oxford OX1 3PS, UK.
Proc Biol Sci. 2011 Feb 7;278(1704):356-63. doi: 10.1098/rspb.2010.1447. Epub 2010 Aug 25.
In order to move effectively in unpredictable or heterogeneous environments animals must make appropriate decisions in response to internal and external cues. Identifying the link between these components remains a challenge for movement ecology and is important in understanding the mechanisms driving both individual and collective motion. One accessible way of examining how internal state influences an individual's motion is to consider the nutritional state of an animal. Our experimental results reveal that nutritional state exerts a relatively minor influence on the motion of isolated individuals, but large group-level differences emerge from diet affecting inter-individual interactions. This supports the idea that mass movement in locusts may be driven by cannibalism. To estimate how these findings are likely to impact collective migration of locust hopper bands, we create an experimentally parametrized model of locust interactions and motion. Our model supports our hypothesis that nutrient-dependent social interactions can lead to the collective motion seen in our experiments and predicts a transition in the mean speed and the degree of coordination of bands with increasing insect density. Furthermore, increasing the interaction strength (representing greater protein deprivation) dramatically reduces the critical density at which this transition occurs, demonstrating that individuals' nutritional state could have a major impact on large-scale migration.
为了在不可预测或异质的环境中有效地移动，动物必须根据内部和外部线索做出适当的决策。确定这些组成部分之间的联系仍然是运动生态学的一个挑战，对于理解驱动个体和集体运动的机制非常重要。一种检查内部状态如何影响个体运动的方法是考虑动物的营养状态。我们的实验结果表明，营养状态对孤立个体的运动影响相对较小，但饮食会影响个体间的相互作用，从而产生较大的群体水平差异。这支持了这样一种观点，即蝗虫的大规模运动可能是由同类相食驱动的。为了估计这些发现对蝗虫蝗蝻带集体迁徙的可能影响，我们创建了一个蝗虫相互作用和运动的实验参数化模型。我们的模型支持这样一种假设，即营养依赖的社会相互作用可以导致我们实验中观察到的集体运动，并预测随着昆虫密度的增加，蝗蝻带的平均速度和协调程度会发生转变。此外，增加相互作用强度（代表更大的蛋白质缺乏）会显著降低发生这种转变的临界密度，这表明个体的营养状态可能对大规模迁徙产生重大影响。
