The role of skill in animal contests: Analysis of a neglected RHP trait in fighting hermit crabs

动物生存和繁殖所需的资源往往供应有限。因此，进化产生了攻击性行为，允许个体从他人那里获取资源。由此产生的战斗或竞争行为一直是激烈研究的焦点，因为从进化的角度来看，赢得战斗的能力对个体的成功有很大的影响。大多数的努力都集中在动物为什么要打架，以及它们应该如何做出放弃打架和放弃争夺资源的决定。相比之下，对于动物是如何战斗的，以及赢家和输家的攻击行为有何不同，人们付出的努力要少得多。这一点之所以重要，有两个原因。首先，我们对动物打斗原因的理解依赖于衡量它们的战斗能力。虽然体型较大的个体显然应该比体型较小的个体更强壮，但在自然界中，当对手势均力敌时，会发生更多的战斗。因此，它们在攻击行为上的细微差异可能真正导致了战斗能力的差异。其次，通过研究攻击行为本身，我们直接研究了我们认为是由自然选择产生的赢得战斗的特征。在这个项目中，我们将把我们的调查重点放在战斗能力的一个潜在的重要组成部分上，这个组成部分迄今几乎完全被忽视了：赢家和输家在技能上的差异的可能性。技能描述了动物用来形成攻击行为的运动模式的有效性。我们将使用精确的拍摄和3D动画技术来测量战斗寄居蟹的运动模式。这些小甲壳类动物为了争夺它们赖以保护的空蜗牛壳的所有权而争斗。一只螃蟹，防御者在战斗中大部分时间都躲在壳里。与此同时，攻击者用它的壳反复撞击防御者的壳的表面。如果攻击者打得很好，这种拍打壳的行为将导致防御者释放对壳的内部控制，允许攻击者驱逐它并接管防御者新腾出的壳。我们知道有力的说唱（即高速度）很重要，但技巧也应该起作用吗？在这里，我们要问的是，驱逐防御者的成功攻击者是否比那些没有被驱逐的攻击者更有技巧。首先，我们将通过比较成功和不成功的攻击者之间的位移距离和攻击位置来询问他们的炮弹敲击是否更有效和准确。我们还将通过比较成功和不成功的攻击者的影响点的集中程度来询问精度是否重要。然后，我们将研究攻击者如何决定何时在弹敲击和一种要求较低的战术之间切换，称为弹摇。在赠款的第二部分，我们将研究可能支持战斗技能变化的因素。例如，更熟练的战士在体力要求或认知任务中是否也表现得更好？在一场对手应该试图阻碍技巧性格斗的战斗中，一个人在技巧性格斗方面的潜力有多大？这些研究将首次共同努力研究技能在动物竞赛中的作用。通过更好地了解如何成为一名优秀的战士，我们将对侵略的进化获得新的见解。此外，这些研究将有潜在的更广泛的影响，超出生物学。在体育科学中，技术也由准确性、精确度、效率和适当的战术组成。我们将用于分析寄居蟹这些参数数据的统计方法可以适用于寻求识别潜在精英运动员或揭示个人训练计划中有待改进的领域的计划。

The resources that animals need to survive and reproduce are often limited in supply. Therefore, evolution has produced aggressive behaviours that allow individuals to take resources from others. The resulting fighting or contest behaviour has been the focus of intense study because the ability to win fights will have a strong effect on an individual's success in evolutionary terms. Most effort has focussed on the questions of why animals should fight and how they should make the decision to quit a fight and relinquish the contested resource. In contrast far less effort has been made to understand how animals fight, and what might differ between the aggressive behaviour of winners and losers. This is important for two reasons. First, our understanding of why animals fight is dependent on measuring their fighting ability. While it seems obvious that larger individuals should be stronger than smaller ones, in nature more fights take place when opponents are evenly matched. Therefore, it could be subtle differences in their aggressive behaviour that really drive differences in fighting prowess. Second, by investigating aggressive behaviour its-self we are directly investigating the traits for winning fights that we assume are produced by natural selection. In this project we will focus our investigations on a potentially important component of fighting ability that has been almost completely ignored to date: the possibility that winners and losers differ in skill. Skill describes the effectiveness of the movement patterns that animals use to form aggressive behaviours. We will use accurate filming and 3D animation technology to measure the movement patterns of fighting hermit crabs. These small crustaceans fight over the ownership of the empty snail shells that they rely on for protection. One crab, the defender spends most of the fight tightly withdrawn into its shell. The attacker, meanwhile, uses its shell to repeatedly strike the surface of the defender's shell. If the attacker fights well, this shell rapping behaviour will cause the defender to release its internal grip on its shell, allowing the attacker to evict it and take over the defender's newly vacated shell. We know that vigorous rapping (i.e. at a high rate) is important but should skill play a role as well? Here we will ask whether successful attackers that evict the defender fight more skilfully than those that fail to gain an eviction. First we will ask if their shell rapping is more efficient and accurate, by comparing the displacement distances and the positions of strikes between successful and unsuccessful attackers. We will also ask whether precision is important by comparing how concentrated the points of impact are for successful and unsuccessful attackers. Then we will examine how attackers decide when to switch between shell rapping and a less demanding tactic called shell rocking. In the second part of the grant we will look at the factors that could underpin variation in fighting skill. Do more skilful fighters, for instance, also show better performance of physically demanding or cognitive tasks? And how much of an individual's potential for fighting skilfully (technique) is actually expressed during a fight where its opponent should try to hinder skillful fighting? These studies will represent the first concerted effort to study the role of skill in animal contests. By providing a better picture of what makes a good fighter, we will gain new insights into the evolution of aggression. Furthermore, these studies will have potential broader impacts beyond biology. In sports science, skill is also composed of accuracy, precision, efficiency and appropriate tactics. The statistical approaches we will use for analysing the data on these parameters in hermit crabs could be adapted for use in programmes that seek to identify potential elite athletes or to reveal areas for improvement in individual training programmes.