Frog Calls at the Zoo Listening Lab

Listening Without Putting Frogs at Risk

At a zoo listening lab, keepers study túngara frogs. Male frogs of this species call to attract females. Some calls are a plain whine. Other calls are a whine followed by extra short notes. Calling style is a behavior trait. A male can change its style, so the study compares calls rather than two fixed kinds of frogs.

Female frogs use calls to find possible mates. Some frog-eating bats also listen for frog calls while hunting. The keepers use recordings to study these responses. These are made-up practice records based on behaviors scientists study.

First, the keepers run 20 female-frog trials. In each trial, a female hears a plain call from one speaker and an extra-note call from another. Next, they run 20 bat trials in a separate flight room, using the same two recordings. No live frogs are in the bat room. Trained keepers care for the animals.

The recordings play at equal loudness for equal lengths of time. The speakers are the same distance from the animal. The keepers switch which side plays each call between trials. They record the first speaker each animal approaches. In these trials, each animal approaches one speaker. Some animals take part in more than one trial. The records do not count mating, young frogs or frogs eaten.