LONDON — When it comes to mating, guppies treasure their ugly friends – because they look so good by comparison.
An article published Wednesday by Britain's Royal Society says that male guppies prefer to associate with their drab-colored counterparts when females were around.
"Males actively choose the social context that maximizes their relative attractiveness," the article said. Or, as lead author Clelia Gasparini put it, "If you are surrounded by ugly friends, you look better."
Gasparini and her colleagues at Italy's University of Padua built their theory on a kind of guppy dating game. An aquarium was set up with one female in partition on either end. Guppy bachelorette No. 1 had two attractive, brightly-colored males placed on either side of her. Guppy bachelorette No. 2 was stuck with uglier, drab-colored fish.
When a male guppy was put in the middle of the tank, and given the choice of which female to sidle up to, Bachelorette No. 2 was the more popular pick, with male guppies spending about 62 percent of their time hanging around her side of the aquarium.
What's more, the researchers found that the time guppies spent with bachelorette No. 2 correlated with their unattractiveness. The uglier the guppy, the less likely it was that he would hang around the brightly colored fish placed next to bachelorette No. 1.
Because it could be argued that that guppies avoided their brightly colored pals because attractive fish were more aggressive, or because predators were more likely to spot them, the experiment was repeated. Researchers ran it without any females, and again with the lights in the male enclosures turned down so that the test guppies couldn't see them.
Gasparini, who's now a post-doctoral researcher at the University of Western Australia, said the extra experiments helped confirm her theory. But she was cagey when asked whether the results from the aquarium could be applied to a night out at the bar.
"Usually in my research we don't really compare humans and animals," she said, chuckling.
Oh, come on. If this works for guppies – small fish popular for use in home aquariums – shouldn't it work for guys?
She admitted that she had seen this same tactic work "pretty well" for humans.
If you hang out "with someone better looking than you, sure, you have less chance to be picked up," she said. "If you want to impress someone, do you think you will look more attractive in comparison with Mr. Bean or George Clooney?"
In a more serious moment, Gasparini said the comparison between guppies and humans was hard to resist. But human dating tricks were far harder to measure.
A subject for further study, then.
Raphael Satter can be reached at: http://raphae.li/twitter