The relationships among nuptial coloration, aggression, and courtship of male three-spined sticklebacks, Gasterosteus aculeatus

A method was devised, using several independent judges, to estimate the degree of nuptial coloration of male three-spined sticklebacks, Gasterosteus aculeatus. Using the color-state scores that resulted from this technique, territorial males were compared with respect to their coloration level and with respect to their responsiveness to live and dummy stimulus fish. These comparisons reveal a positive association between color state and responsiveness: brightly colored males tend to court (zigzag) and attack (bite) stimulus fish more vigorously than duller colored males do. Therefore, the degree to which a male three-spined stickleback's nuptial coloration is developed can be used to some extent to predict its responsiveness, with the particular category of response (courtship or aggression) dependent on the stimulus presented. A close association between zigzag and bite frequencies was also found, responsive males showing higher levels of both courtship and aggression than less responsive ones. These results are consistent with evidence pertaining to the hormonal control of nuptial coloration, courtship, and aggression and to the signal value of nuptial coloration in G. aculeatus.