Relative sexual attractiveness does not influence mate-choice copying in male Trinidadian guppies, Poecilia reticulata

Abstract

Copying the mate choice of another conspecific by a bystanding observer is a socially mediated alternative mating strategy to independent mate choice. Because increased sperm competition is a potential cost of mate-choice copying, males should be prudent and less likely to copy the observed mate choice of other males when the latter are more sexually attractive than themselves. We tested this hypothesis using the Trinidadian guppy, Poecilia reticulata. Focal observer males were simultaneously presented with a large and a small female as potential mates, either in the presence or absence of a nearby model male. We varied the relative differences in the body length and colour ornamentation, traits that predict male sexual attractiveness and competitiveness in the guppy, of observer and model males in each of three experimental treatments: (1) observer and model males were matched for body length and colour ornamentation; (2) the model male was larger and more colourful than the observer male; (3) the model male was smaller and less colourful than the observer male. We compared the mating preferences of focal observer males in each of the latter treatments with that of focal males in a control treatment, wherein no model male (and thus no copying opportunity) was present. As predicted, focal males copied the staged apparent mate choice of a model male in all three experimental treatments, but not in the control treatment. However, contrary to our a priori hypothesis, there were no significant differences in the likelihood or strength of the copying response in observer males among the experimental treatments. Although male guppies are known to modify their mating tactics in the presence of sexual competitors, we found no evidence for an influence of the relative phenotypes of observer and model males on mate-choice copying behaviour in focal observer males.