SNOWBIRD, UTAH--When it comes to which boys they'd like to date, teenage girls aren't the only ones who tend to copy each other's choices. Nature is full of species behaving like adolescent humans, and new research shows that the tendency to copy may be a heritable trait, at least in guppies.
Humans and other brainy mammals often teach their young to mimic the behavior of others. Young chimps, for example, have been observed intently watching as their elders show them how to crack open nuts using rocks. Such lessons ensure that certain behaviors will be passed on to the next generation. But in shorter lived, less social animals such as fish, there aren't many teachable moments. Yet in some species, generation after generation, animals still seem to copy each other's behaviors, leaving scientists to wonder if the copying habit itself can be inherited.
To test the idea, biologist Lee Dugatkin of the University of Louisville in Kentucky examined female guppies, which mimic the mate choices of their peers. After a group of female fish gave birth, Dugatkin watched the moms to see how likely they were to copy another female's mate choice. Each mom was put in a tank alone with two males in adjacent tanks on either side. Another female was placed in a tank next to one of the males, and the mom was able to watch the courtship unfold. The courting female was then removed, leaving the mom alone to make a selection. If she spent more of her time near the male "chosen" by the other female, she was a considered a copier. About 85% of the females proved to be copiers, Dugatkin found.
Once the offspring of the copiers were ready to mate, Dugatkin put them through the same tests and found that they also were more likely to be copiers than were the offspring of the 15% of moms with an independent streak. This suggests that the tendency to copy another's mate choice preference is a heritable trait, says Dugatkin, who presented his results here 9 August at a meeting of the Animal Behavior Society.
The findings suggest that guppy culture, such as it is, may have a strong genetic component, says John Swaddle, a behavioral ecologist at the College of William and Mary in Williamsburg, Virginia, who studies mate choice copying in finches. As a result, behavior may be passed more quickly through copying than through genes in some cases, he says.