What Drives the Group Size Effect in Ant-Predator Vigilance?

9723437利马这项研究旨在对一种普遍存在的行为现象有一个新的理解：警戒群体规模效应，即社交喂养的动物随着群体规模的增加而变得不那么警惕(警觉)。尽管这是动物行为研究中最成熟的结果之一，但许多重要的问题仍然没有得到解决，甚至没有被认识到。拟议中的实验旨在帮助纠正这种情况，通过这样做，将首先阐明为什么这么多类型的动物是社会性的。这项拟议的研究首先聚焦于对群体规模效应的所有解释的基本假设：动物在低着头积极进食时无法察觉捕食者。最近的研究表明，明显不警惕(进食)的鸟类可以在相当远的距离侦测到逼近的捕食者攻击。因此，一个主要的目标是在现实情况下描述这种能力在鸟类中的特征(以黑眼睛的Junco hyemalis为代表)，然后探索其对群体规模效应本身的影响。这项拟议的工作将确定群体规模效应是否代表了以前未被认识到的低质量警觉(实际进食时)和高质量警觉(公开警觉时)之间的相互作用。这项拟议的研究还探索了关于群体规模效应的两种非正统解释。第一种是基于理论发展的，这些理论表明，群体规模效应的产生仅仅是因为群体规模随着时间的推移而频繁变化(动物在群体中来来去去)。这一想法将通过允许圈养的野熊以固定的群体规模或随时间变化的群体进食来检验。如果新的理论是正确的，那么只有那些经历不同群体大小的鸟类才应该表现出基本的群体大小效应。关于群体规模效应的第二种非正统解释涉及对食物的竞争对警觉的影响。这一观点并不否认动物对捕食者保持警惕，但坚持认为，在较大的群体中，动物降低了对捕食者的警惕，因为随着群体规模的增加，对食物的竞争更加激烈。如果这一观点是正确的，那么当动物以有限的食物供应为食时，群体规模效应应该更加明显；这一预测将在家雀(Carpodacus Micianus)群中得到验证。这项研究的结果将有助于更好地理解群体行为和社会性的演变。

9723437 Lima This research is directed at a new understanding of a widespread behavioral phenomenon: the vigilance group size effect, in which socially-feeding animals engage in less vigilance (alertness) with an increase in group size. Despite the fact that this is one of the most well established results in the study of animal behavior, many important issues remain unaddressed and even unrecognized. The proposed experiments are designed to help remedy this situation, and in doing so, will shed light on the reasons why so many types of animals are social in the first place. The proposed research focuses first on an assumption fundamental to all explanations of the group size effect: that an animal cannot detect predators while it is actively feeding with its head down. Recent work suggests that apparently non-vigilant (feeding) birds can detect approaching predator attacks at a considerable distance. A main goal is thus to characterize this ability in birds (as represented by the dark-eyed junco, Junco hyemalis) under realistic situations, and then explore its consequences for the group size effect itself. This proposed work will determine whether the group size effect represents a previously unrecognized interaction between poor quality vigilance (while actually feeding), and high quality vigilance (while overtly alert). The proposed research also explores two unorthodox explanations for the group size effect. The first is based on theoretical developments which suggest that the group size effect occurs only because group sizes change frequently over time (as animals come and go from the group). This idea will be tested by allowing captive juncos to feed in constant group sizes or in groups that vary over time. If the new theory is correct, only those birds experiencing the variable group sizes should exhibit the basic group size effect. The second unorthodox explanation for the group size effect concerns the effect of competition for food on vigilance. This view does not deny that animals are vigilant for predators, but maintains that they decrease their vigilance in larger groups because competition for food is more intense as group size increases. If this view is correct, then the group size effect should be much more pronounced when animals are feeding on a limited food supply; this prediction will be tested in flocks of house finches (Carpodacus mexicanus). Results from this research will allow a better understanding of group behavior and the evolution of sociality.