Fishing around for the right mate.

Finding the right male to mate with is not a simple matter-not even for a female guppy. Oh sure, she could go just for good looks: a guy's size, tail length, and color, for example. Some of these physical preferences are so important to reproduction that they appear to be hard-coded into a guppy's genetic heritage.

Yet female guppies don't depend solely on those factors for choosing a mate, notes Lee Alan Dugatkin of the University of Louisville in Kentucky. A few years ago, he found that a female guppy often imitates the mating choices of other females.

In the April 2 Proceedings of the National Academy of Sciences, he reports on the first systematic look at whether appearance or cultural cues dominate this fishy issue. He finds that female guppies, which normally prefer a mate with lots of orange, are easily persuaded to pick a male with less orange coloration if they observe another female mating with him.

In special cases, looks can override those cultural cues. 'When the males are dramatically different [in amount of color], females don't copy,' says Dugatkin. If one of two available males has at least 40 percent more orange color than the other, a female will mate with him regardless of the other females' actions. Dugatkin suggests that examining the behavior of guppies may provide insight into how to study the inherited and cultural factors that govern mating choices of women.