Carrièrebeslissingen van Beekjuffers (Calopteryx)

Males of Calopteryx splendens and C. virgo sometimes engage in long, escalated fights. This paper adresses the question why these damselflies spend so much time and energy in those fights. By individually marking males from both species we showed that about three quarters of the marked individuals was restricted to a particular site. These males were frequently involved in short disputes with bordering males, suggesting that the males defended territories. Males not restricted to a particular site hardly got engaged in these border disputes, suggesting that these males were non-territorial. Only one escalated fight was observed in which a marked territorial male was displaced by a non-territorial individual after more than 30 minutes continuous fighting. Territorial males attracted females by a flight display, sometimes including a part in which males entered the stream and floated some distance downstream. Non-territorial males chased females in a pursuit flight. The territorial strategy is far more rewarding in Calopteryx damselflies, resulting in 1000 times more eggs fertilized per day than males without territories (Plaistow & Siva-Jothy, 1996). The escalated fights seem to be a way of getting the preferred mating option.