The angle of attack: Rapping technique predicts skill in hermit crab contests

Skill, the ability to perform a challenging behaviour well, has been shown to be an important determinant of success in a variety of contexts, including human sports, animal courtship and most recently, animal contests. Because skilful movement requires precise motor control, skill is assumed to be underpinned by traits that determine these abilities. However, while these traits determine an individual's potential to perform skilful movements (known as technique), this potential may not translate into skilful fighting due to interference from the opponent. Here, we investigate the relationship between technique and skill using the European hermit crab Pagurus bernhardus. By examining the spatial distribution of shell raps, we find that on average, technique exhibited during a "training" fight predicts the level of skill displayed in a real contest. However, our results also demonstrate substantial among-individual variation in the direction of change across the two fights, with some individuals exhibiting better technique than skill and others showing the opposite pattern. Finally, we find that winners, but not losers, progressively adapt their targeting of strikes when faced with a fully functional opponent. Our results indicate that skill is a combination of innate technique and the ability to adapt to an opponent's behaviour.