The nest matters: reproductive state influences decision-making and behavioural consistency to conflicting stimuli in male Siamese fighting fish, Betta splendens

Before the heritable basis or fitness consequences of differences in decision-making can be explored, consistent variation in decision-making among individuals must be established. The presentation of conflicting stimuli in the form of a female and a male provides a unique situation that has not been widely explored in terms of consistent individual variation. To assess consistency and plasticity in decision-making, male Siamese fighting fish were presented with a single female, single male and paired male and female presented simultaneously both when they did and did not have nests. Having a nest had a marked effect on male response, but only towards the female. Males differed from one another in the strategies they used when faced with conflicting stimuli; some males focused on the male, others on the female, and still others divided their response between the two. Most importantly, males behaved consistently yet differed from one another when context and reproductive state were constant. Finally, some males exhibited consistent plasticity as a result of social environment and/or reproductive state, the first finding of this kind. This study demonstrates the presence of consistent individual variation in decision-making, providing the groundwork for further studies into the evolution of this trait.