Male guppies change courtship behaviour in response to their own quality relative to that of a rival male

Compared with female mate choice, male mate choice has been an important but minor topic in the past two decades. In the guppy, Poecilia reticulata , a male approaching a female abandons his courtship when a rival male appears next to the focal female; however, the effect of the relative quality of the males on this behavioural change is unknown. We show here that male guppies abandon their approach to a female only when the rival male is phenotypically superior. Both natural and artificially induced brightly coloured males continued to approach a female even when the rival male was brightly coloured, but both natural and induced dull-coloured males abandoned their approach to a female when the rival was brightly coloured. Males decided their behaviours on the basis of their own appearance, not on their genotypes, because artificially induced brightly and dull-coloured brothers differed in their behaviour. Our results show that male mate choice behaviour is finely tuned to maximize the probability of acceptance by the approached female.