Is boldness a resource-holding potential trait? Fighting prowess and changes in startle response in the sea anemone, Actinia equina

Abstract

Contest theory predicts the evolution of a stable mixture of different strategies for fighting. Here, we investigate the possibility that stable between-individual differences in startle-response durations influence fighting ability or 'resource-holding potential' (RHP) in the beadlet sea anemone, Actinia equina. Both winners and losers showed significant repeatability of pre-fight startle-response durations but mean pre-fight startle-response durations were greater for eventual losers than for eventual winners, indicating that RHP varies with boldness. In particular, individuals with short startle responses inflicted more attacks on their opponent. Both repeatability and mean-level responses were changed by the experience of fighting, and these changes varied with outcome. In losers, repeatability was disrupted to a greater extent and the mean startle-response durations were subject to a greater increase than in winners. Thus, following a fight, this behavioural correlate of RHP behaves in a way similar to post-fight changes in physiological status, which can also vary between winners and losers. Understanding the links between aggression and boldness therefore has the potential to enhance our understanding of both the evolution of animal personality and the 'winner and loser effects' of post-fight changes in RHP.

Aggressiveness as a component of fighting ability in pigs using a game-theoretical framework

“…However, the results of this study should be interpreted with some caution as the sample size was limited (although comparable with other studies, e.g. 48 contests in Rudin & Briffa, 2012), and 27% of the dyads did not fight. The fact that some contests did not escalate is something that should be taken into account as it may comprise a substantial part of the sample size.…”

“…However, the importance of integrating animal personality within existing contest theory has only recently been acknowledged (Briffa et al, 2015), with aggressiveness generally having been overlooked. However, boldness has been studied in contest settings in sea anemones, with boldness being correlated with aggressiveness (Rudin & Briffa, 2012). Aggressiveness might account for part of the discrepancy with existing studies in which, contrary to expectations, the contestant with apparently superior RHP does not win.…”

Animal personality as a cause and consequence of contest behaviour

“…The effect of observing a demonstrator of different behavioural type was absent for fish that started out as shy but winning a fight still emboldened them post-contest. In A. equina, losers showed decreased boldness 24 h after fighting and repeatability was reduced across consecutive observations interrupted by fighting [23]. By contrast, P. bernhardus defenders that lost their shells became bolder after the fight, whereas for those that resisted eviction withdrawal durations increased [26].…”

“…Lett. 11: 20141007 repeatable boldness assayed by the duration of tentacle retraction following disturbance [23]. Pre-fight boldness correlates with the chance of winning but, in contrast to the situation in defending hermit crabs, losers show longer startle responses than winners [23].…”

Competition as a source of constraint on life history evolution in natural populations

“…Whether boldness is functionally important for resource acquisition under scramble competition (for example, if bolder individuals more likely to arrive first at a resource) remains to be seen. However, it is worth noting that boldness-related traits can be heritable (Dingemanse et al, 2012) and positively correlated with aggressiveness (Rudin and Briffa, 2012). As aggressiveness is (usually) indicative of success in contest competition, this raises the interesting question of whether populations are characterised by (genetic) variance in competitive ability per se.…”