Short-term exposure to an endocrine disruptor affects behavioural consistency in male threespine stickleback.

It has been established that exposure to xenooestrogens can have profound effects on reproductive and aggressive behaviours in aquatic organisms. Studies on the effects of 17α-ethinyloestradiol (EE2) on behaviour, however, rarely examine these effects over multiple trials, across time, or across contexts. In addition, it is possible that individuals vary in their sensitivity to EE2 and individuals may differ in the degree to which their behaviour is affected. The study of consistent individual differences in behaviour has grown in popularity in recent years perhaps because of the evolutionary questions this behavioural variation raises. Adult male threespine stickleback (Gasterosteus aculeatus) from an anadromous population repeatedly received the simultaneous presentation of a dummy male and dummy female conspecific both before and after exposure to a short-term, nominal (15 ng L(-1)) concentration of 17α-ethinyloestradiol (EE2). These before and after measures were then compared against one another as well as against responses of males in a control group that was not exposed to EE2. Courtship, aggression, and nesting behaviours were all affected by EE2 exposure. In addition, behavioural consistency over trials was markedly reduced after EE2 exposure, as shown by lower repeatability values in the after exposure measures and in weaker correlations between the before and after exposure measures in the EE2 group compared to the control group. This suggests that male threespine stickleback vary in their sensitivity to EE2. This study is one of the first to examine the effects of short-term EE2 exposure on behaviour across trials and has important implications for population-level fitness consequences of xenooestrogens.