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

• Male guppies change courtship in response to their relative appearance to a rival.
• Superior male guppies do not stop courtship irrespective of type of rival.
• Inferior male guppies abandon courtship when a rival is phenotypically superior.
• Inferior males change partner to less preferred female in presence of a rival.
• Artificially differentiated brothers showed the same behavioural patterns.

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.