Limitations to colour-based sexual preferences in three-spined sticklebacks (Gasterosteus aculeatus)

Female three-spined sticklebacks (Gasterosteus aculeatus) are suggested to select mates based on their red nuptial coloration, males with a redder dis play being more preferred. Although there are both laboratory and field dat a to support this view, there are also published accounts where females do not show a preference for the redder male. Here we report the results of a series of 19 trials where receptive gravid female three-spined sticklebacks were allowed to choose between two size-matched rival males. We used photo graphic and image analysis techniques to quantify male nuptial coloration t o investigate how the magnitude of the colour difference between the two al ternative males influenced female preferences. Using the amount of time a f emale spent oriented towards each male as a measure of his attractiveness t o her, females were not always found to select the redder of the two presen ted males. We did, however, find that that the relative difference in color ation of the two males in each pair was important in determining the level of coloration-based preference, with females only selecting redder males co nsistently when the difference in coloration was sufficiently large.