EXPERIMENTAL INVESTIGATIONS OF THE EVOLUTIONARY SIGNIFICANCE OF SEXUALLY DIMORPHIC NUPTIAL COLORATION IN GASTEROSTEUS-ACULEATUS (L) - THE RELATIONSHIP BETWEEN MALE COLOR AND FEMALE BEHAVIOR

Cladistic analysis of behavioural interactions during a series of female choice trials revealed 3 groups of reproductively unsuccessful males in a population of anadromous three-spined stickleback: inactive losers (losing male did not participate in choice test), active losers (losing male active during choice test), and fighting losers (subgroup of active losers defined by the observation that the female did not immediately follow the first male to approach her). The inactive losers group represents a "no choice' situation. In the remaining groups, females responded preferentially to the most intensely coloured member of the competing male pair. This preferential response was strongest during the prechoice, captive presentation where the majority of females oriented head-up to, and tracked, the brighter red male. Once released, the female's initial response to the brighter courtship signal was overridden by the behavioural actions of the duller intensity male in 4 out of 12 trials. Although 2 of these males eventually lost the female to their rival, the remaining 2 individuals succeeded in spawning. Overall, 10 of 12 females spawned with the brighter red male. Given the brief breeding season and the advantage enjoyed by the most brightly coloured males in mate attraction, a high level of territorial intrusion is one way for an individual to attract a mate if he is surrounded by more intensely coloured neighbours. -Authors