Guppies hang with ugly friends to look hotter

By Jude Dineley 15 February 2013
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Male guppies socialise with drab-looking buddies in order to increase their sex appeal, a study has revealed.

If you found yourself all alone on Valentine’s day, maybe the problem is that you’re hanging out with the wrong people – or the wrong fish. A new study has found that given the choice, male guppies will socialise with other, less attractive males to maximise their chance of mating.

This finding, published this week in the Proceedings of the Royal Society B journal, may explain why guppy populations haven’t evolved to consist of only brightly coloured males.

“We have shown for the first time that males are really able to choose the most appropriate [social] context that maximises their attractiveness,” says co-author Dr Clelia Gasparini, an evolutionary biologist at the University of Western Australia in Perth.

Fish socialise with less attractive counterparts

Researchers have long known that female guppies (Poecilia reticulata) compare their suitors, opting for the most colourful males. And while it was suspected that males could exploit this by choosing a social group that made them stand out from the crowd, until now there has been no hard evidence of the behaviour.

Clelia and her collaborators observed the behaviour when they presented individual male guppies with a choice of two females, each surrounded by a group of males.

One group had been carefully selected to contain only drab-looking males, bearing almost no orange – the colour known to be most attractive to females. The other group contained colourful, attractive males with more than 20 per cent of their body covered in orange.

Not only did the individuals consistently choose the group of drab males, the behaviour was accentuated in drab individuals.

“If you are colourful and already successful with females, it’s less important to choose your [social] context,” says Clelia. “While if you are less coloured, this will really make the difference to your success.”

Experience lets guppies know how sexy they are

The research suggests that male guppies most likely learn how attractive they are through experience. Males who had never encountered other males, had no preference when presented with the drab and colourful groups.

“They probably learn how successful they are by comparing their success with other males around them,” says Clelia.

In evolutionary terms, the findings may explain why guppy populations retain a wide variation in colouring, despite the female’s consistent preference for flashy males.

Dr Darrell Kemp, an evolutionary biologist at Macquarie University in Sydney, says the study is the first time such tactical choices have been convincingly demonstrated in any animal.

Darrell says the implications could stretch beyond guppy populations: “Even though we are testing on a specific animal, the implications are broader than that because it really tells us about concepts which might apply across many sexually reproducing animals.”