Male mate choice in the Trinidadian guppy is influenced by the phenotype of audience sexual rivals

Abstract

In populations with male mate-choice copying, males may mitigate their risk of sexual competition by reducing their preference for a particular female in the presence of sexual rivals (audience). Because of the cost of missed mating opportunities from such an audience effect, males should reduce their mating preference to a greater extent in the presence of more sexually competitive rivals compared with less competitive ones. We tested this hypothesis using the Trinidadian guppy (Poecilia reticulata). We compared a focal male's baseline mating preference for either of 2 stimulus females, which differed in overall body size, in the absence of any sexual rival to his preference for the same females in the presence of a sexual rival using dichotomous-choice tests. Focal and audience males differed in body length and proportion of their body covered in orange and black pigmentation. In the presence of a larger rival, focal males exhibited a greater reduction in preference for their initially preferred female compared to focal males in the presence of a smaller rival, irrespective of whether the latter male was more or less ornamented than the focal. The strength of the initial mating preference of focal males and the magnitude of the audience effect were significantly positively correlated when the audience male was larger than the focal male. Male guppies are thus sensitive to the phenotype of nearby males and alter their preference for a particular mate to a greater extent in the presence of relatively larger eavesdropping males compared to smaller ones.