Hansen M J, Schaerf T M, Krause J, Ward A J W
Animal Behaviour Lab, School of Biological Sciences, the University of Sydney, Sydney, NSW 2006, Australia.
School of Science and Technology, University of New England, Armidale, NSW 2351, Australia.
PLoS One. 2016 Feb 5;11(2):e0148334. doi: 10.1371/journal.pone.0148334. eCollection 2016.
Decision making in moving animal groups has been shown to be disproportionately influenced by individuals at the front of groups. Therefore, an explanation of state-dependent positioning of individuals within animal groups may provide a mechanism for group movement decisions. Nutritional state is dynamic and can differ between members of the same group. It is also known to drive animal movement decisions. Therefore, we assayed 6 groups of 8 rainbowfish foraging in a flow tank. Half of the fish had been starved for 24h and half had been fed 1h prior to experimental start. Groups were assayed again one week later but individuals were allocated to the opposite nutritional treatment. During the assay the positions of individually identified fish were recorded as were the number of food items they each ate and the position within the group they acquired them from. Food-deprived fish were more often found towards the front of the shoal; the mean weighted positional score of food-deprived fish was significantly larger than that of well-fed fish. Individuals were not consistent in their position within a shoal between treatments. There was a significant positive correlation between mean weighted positional score and number of food items acquired which displays an obvious benefit to front positions. These results suggest that positional preferences are based on nutritional state and provide a mechanism for state-dependent influence on group decision-making as well as increasing our understanding of what factors are important for group functioning.
研究表明，移动动物群体中的决策受到群体前端个体的影响过大。因此，解释动物群体中个体的状态依赖性定位可能为群体移动决策提供一种机制。营养状态是动态的，同一群体的成员之间可能存在差异。已知营养状态也会驱动动物的移动决策。因此，我们对6组每组8条彩虹鱼在流水槽中觅食的情况进行了测定。一半的鱼在实验开始前已饥饿24小时，另一半在实验开始前1小时喂食。一周后再次对这些组进行测定，但将个体分配到相反的营养处理组。在测定过程中，记录了每条被单独识别的鱼的位置，以及它们各自吃掉的食物数量和获取食物时在群体中的位置。食物匮乏的鱼更常出现在鱼群前端；食物匮乏的鱼的平均加权位置得分显著高于喂食良好的鱼。不同处理之间，个体在鱼群中的位置并不一致。平均加权位置得分与获取的食物数量之间存在显著的正相关，这表明处于前端位置有明显优势。这些结果表明，位置偏好基于营养状态，为状态依赖性影响群体决策提供了一种机制，同时也增进了我们对哪些因素对群体功能重要的理解。
