Do unattractive friends make you look better? Context-dependent male mating preferences in the guppy

Recent theory predicts that in species where females tend to mate with the relatively most ornamented males, males may increase their attractiveness to females, and hence mating success, by preferentially associating with females that are surrounded by less ornamented competitors. Despite this prediction, we still lack explicit experimental evidence that males strategically prefer females surrounded by less attractive competitors to maximise their relative attractiveness In this paper we provide a comprehensive test of this hypothesis in the guppy (Poecilia reticulata), a species where female’s perception of a male’s attractiveness depends on his coloration relative to that of surrounding males. We found that males preferentially associated with females that were surrounded by relatively drab competitors, and that the strength of an individual male’s preference was negatively correlated with his level of ornamentation. A series of control experiments made it possible to exclude the pote...