UV wavelengths affect female mate choice in three-spined sticklebacks

Recent behavioural studies on fish have emphasized the role of ultraviolet (UV) wavelengths in mate choice. We performed female mate choice experiments, focusing on the UV wavelength range, with the three-spined stickleback, Gasterosteus aculeatus, a species in which the role of visually guided behaviour in the human-visible wavelength range (400–700 nm) has been well studied. Ripe female sticklebacks were given the opportunity to watch courting males behind UV-transmitting (UV+) and UV-blocking (UV−) optical filters. We tested the hypothesis that a difference in viewing conditions, manipulated by the two optical filters, would affect male attractiveness, as indicated by the time that the female stayed near the males. Females significantly preferred UV+ males. They also became less selective with time. Control experiments, in which neutral-density optical filters were used, showed that the ability to perceive UV wavelengths is likely to be used for colour discrimination instead of detecting brightness differences.