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，允许个人从他人那里获取资源。由此产生的战斗或竞争行为一直是密集研究的重点，因为从进化的角度来看，赢得战斗的能力将对个人的成功有很大影响。大多数努力都集中在动物为什么应该战斗以及它们应该如何决定退出战斗和放弃有争议的资源的问题上。相比之下，对于了解动物是如何战斗的，以及成功者和失败者的攻击性行为可能有什么不同，人们所做的努力要少得多。这一点很重要，原因有两个。首先，我们对动物为什么会打架的理解依赖于测量它们的战斗能力。虽然体型较大的个体看起来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，就会发生更多的战斗。因此，可能正是它们攻击性行为上的细微差异真正导致了战斗能力的差异。其次，通过研究攻击性行为本身，我们直接调查了我们认为是自然选择产生的赢得战斗的特征。在这个项目中，我们将把我们的研究重点放在战斗能力的一个潜在的重要组成部分上，这个组成部分到目前为止几乎完全被忽视了：成功者和失败者在技能上存在差异的可能性。技能描述了动物用来形成攻击性行为的运动模式的有效性。我们将利用精准拍摄和3D动画技术来测量打斗寄居蟹的运动模式。这些小型甲壳类动物为争夺它们赖以保护的空蜗牛壳的所有权而战。一只螃蟹，防御者在战斗的大部分时间里紧紧地缩进它的壳里。与此同时，攻击者用它的外壳反复击中防御者的外壳表面。如果攻击者打得很好，这种敲击炮弹的行为将导致防御者释放对其炮弹的内部控制，允许攻击者驱逐它，并接管防御者新腾出的炮弹。我们知道强有力的说唱(也就是高节奏的说唱)很重要，但技巧也应该发挥作用吗？在这里，我们将询问，成功驱逐守卫者的攻击者是否比那些未能获得驱逐的攻击者更巧妙地战斗。首先，我们将通过比较成功和不成功的袭击者之间的位移距离和打击位置来询问他们的炮弹敲击是否更有效和准确。我们还将通过比较攻击点对成功和失败攻击者的集中度来询问精确度是否重要。然后，我们将研究攻击者如何决定何时在贝壳说唱和一种要求较低的策略(称为贝壳摇摆)之间切换。在奖励金的第二部分中，我们将考察可能导致战斗技能差异的因素。例如，更熟练的拳击手是否也表现出更好的体力或认知任务表现？在一场对手应该试图阻碍熟练格斗的战斗中，一个人的熟练格斗(技术)的潜力实际上有多少是被表达出来的？这些研究将是研究技能在动物竞赛中的作用的第一次协同努力。通过更好地了解如何才能成为一名优秀的拳击手，我们将对侵略的演变有新的见解。此外，这些研究将产生超越生物学的潜在更广泛的影响。在体育科学中，技术还包括精确度、精确度、效率和适当的战术。我们将用来分析寄居蟹这些参数的数据的统计方法，可以用于寻找潜在的精英运动员或揭示个别训练方案中需要改进的地方的方案。

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.