Repeatable behavioural type and stable dominance rank in the bluefin killifish

While the prevalence of animal personalities has become apparent in recent years, the importance of animal personalities in determining the outcome of sexual selection remains imperfectly understood. In particular, there are few data on whether repeatable personality differences among males are associated with repeatable outcomes of male–male interactions within the mating context. Using the bluefin killifish, Lucania goodei, we examined the repeatability of individual differences in mating behaviours and the stability of dominance rank, which partially determines mating success in this species. The expression of male behaviours in competition between males and female courtship was significantly repeatable over a 5-week period; the number of aggressive behaviours to males and females, and the number of courtship bouts had significant repeatabilities of 0.71, 0.72 and 0.65, respectively. A maleʹs personality or behavioural type within the mating context, as measured by a composite measure of the overall level of mating behaviour activity, was significantly repeatable at 0.75. Males showed repeatable, linear dominance hierarchies, and a maleʹs rank in the hierarchy was highly correlated with his behavioural type. Neither behavioural type nor dominance rank was associated with body size or body condition. The repeatability of behavioural types and stability in the outcomes of aggressive interactions suggest that these behavioural phenotypes are inherent characteristics of individuals rather than short-term responses to recent social experience or daily levels of food or stress, and may potentially have an early environmental and/or genetic basis.