Curr. Biol. doi:10.1016/j.cub.2008.06.067 (2008)

When it comes to choosing a mate, male Atlantic molly fish (Poecilia mexicana) often have to make their selection when other males are watching. Martin Plath at the University of Potsdam in Germany and his colleagues suggest that, in this situation, males try to deceive others about their true intentions regarding mate choice.

When given their choice of a small or large female, males without an audience usually made advances to the bigger one. When another male was present, however, the molly initially paid attention to the smaller female but then stopped expressing a mating preference.

Plath hypothesizes that the behaviour is a counteradaptation to male mate-choice copying, in which males try to mate with a female that others also pursued.