Mate-choice copying in free-ranging Trinidadian guppies (Poecilia reticulata)

The social experiences of individuals can influence their mate-choice decisions. Mate-choice copying is considered to have occurred if an individual's observation of a sexual interaction between a male and a female increases its likelihood of subsequently preferring the individual observed mating. Although such copying behaviour has been documented extensively in the laboratory, there exists only very limited evidence for its occurrence in nature. Here, we experimentally investigated female mate-choice copying in a wild Trinidadian population of the guppy (Poecilia reticulata), a species that exhibits such copying behaviour in the laboratory. Using a pair of Plexiglas tanks placed in situ in a river in Trinidad, we presented free-ranging adult females with a binary choice of viewing and affiliating with either of two similar-sized stimulus males: one male was viewed next to a visible model (demonstrator) female and the other male viewed apparently alone (placed next to a pseudo-model female hidden from the subject females). Focal subject females preferred to associate with the stimulus male that was near and consorting with a model female than with the lone stimulus male. The results of a separate control experiment suggest that this observed female preference was sexual in nature rather than a simple shoaling response. We conclude that our results are consistent with mate-choice copying behaviour and suggest that female guppies can mate-choice copy in the wild when given the opportunity, as they do under laboratory conditions.