Mate-choice copying under predation risk in the Trinidadian guppy (Poecilia reticulata)

Although females of numerous species possess genetically-based preferences for certain male traits and mate preferentially with males possessing these traits, recent theoretical and experimental evidence indicates that they may also copy (imitate) the mate choices of other females under certain circumstances. Such mate-choice copying is expected to be most prevalent when females have the opportunity to observe the mate choices of others and when mate choice is costly to females. One potential direct fitness cost of mate choice is increased individual risk of mortality due to predation. Here, we investigate for the first time the effect of increasing the apparent risk of predation on the tendency of females to copy the experimentally staged mate choice of another female. Using adult female guppies (Poecilia reticulata) originating from a Trinidadian population that experiences a relatively high fish predation pressure, we first establish that they possess a preference for the more brightly colored of two simultaneously presented males in the absence of both mate-copying opportunity and an immediate threat of predation. However, most females reversed their initial mate preference when given an opportunity to copy the mate preference of another female in the absence of predation threat. The proportion of females reversing their preference when given the opportunity to do so was not affected by increasing the apparent risk of (fish) predation. This result may be owing either to female guppies tending to copy the mate choice of others whenever the opportunity arises because the benefits of doing so accrue irrespective of the ambient risk of predation or to females choosing randomly between males with respect to their color pattern in the presence of the predator irrespective of mate-copying opportunity. These two explanations for the apparent lack of an effect of predation risk on mate-choice copying per se are both plausible but unfortunately could not be easily distinguished here. It may thus be possible, and interesting, that individual female guppies chose randomly between the available males in the presence of the predator but otherwise copied the choice of others when given the opportunity to do so.