Take it from a fish: if you have your eye on someone cute at the beach or a party this weekend, pretend to your friends that you have no interest whatsoever in him (or her), to throw them off the scent.
Everything else being equal, male Atlantic mollies (Poecilia Mexicana) prefer to mate with female Atlantic mollies rather than female Amazon mollies (a cousin species, but one in which male sperm do not contribute any genes to the offspring, meaning there’s hardly any evolutionary reason to bother mating). They all prefer large female Atlantic mollies to smaller ones, since the former are more fecund. That’s indeed what scientists led by Martin Plath of the University of Potsdam in Germany and the University of Oklahoma found: they put male mollies in a tank with a large female and a smaller one, and the males nipped (that’s a sign of affection) and tried to mate with the larger molly more and sooner than with the smaller. Same thing when the males had a choice of an Atlantic molly or an Amazon: they went for the girl of their own species.
But as the biologists report in a study in the online edition of Current Biology, when another male molly was watching the action in a nearby Plexiglass cylinder, they ignore the girl of their dreams and direct their sexual advances toward the punier female in the first case and the Amazon in the second—neither of which was their true first choice.
“I find it particularly interesting that fish are capable of such a sophisticated behavior,” Plath said in a statement. “The study highlights that traits that we typically ascribe to humans only can also be found in other, seemingly simpler animals and that no consciousness or self-awareness is needed for a behavior like deception to occur.”
Deception is rife in the animal world—the non-human part, too. Ravens try to trick other birds about where they hid food, for instance. But this seems to be the first evidence that males deceive other males about their preferred mate rather than simply, as Plath expected, acting as though they’d lost interest in sex. Feigning interest in the not-girl-of-their dreams is smart strategy: male mollies are known to copy other males’ mating preferences, so by leading a rival away from his preferred female a male increases the chance that he and not they will sire offspring.