Female Tree Frogs Prefer Males Who Can Multitask

From frogs to humans, selecting a mate is complicated. Females of many species judge suitors based on many indicators of health or parenting potential. But it can be difficult for males to produce multiple signals that demonstrate these qualities simultaneously. In a study of Cope’s grey tree frogs, a team of University of Minnesota researchers discovered that females prefer males whose calls reflect the ability to multitask effectively. In this species (Hyla chrysoscelis), males produce "trilled" mating calls that consist of a string of pulses. Typical calls can range in duration from 20-40 pulses per call and occur at the rate of between 5-15 calls per minute. Males face a trade-off between call duration and call rate, but females preferred calls that are longer and more frequent, which is no simple task. The findings were published in the August 2013 issue of Animal Behaviour. "It’s kind of like singing and dancing at the same time," says Dr. Jessica Ward, a postdoctoral researcher who is lead author for the study. Dr. Ward works in the laboratory of Dr. Mark Bee, a professor in the College of Biological Sciences’ Department of Ecology, Evolution and Behavior. The study supports the multitasking hypothesis, which suggests that females prefer males who can do two or more hard-to-do things at the same time because these are especially good-quality males, Dr. Ward says. The hypothesis, which explores how multiple signals produced by males influence female behavior, is a new area of interest in animal behavior research. By listening to recordings of 1,000 calls, Dr. Ward and colleagues learned that males are indeed forced to trade off call duration and call rate. That is, males that produce relatively longer calls only do so at relatively slower rates.