In the 25th year of the BBC's Natural History Unit, the second half of a series in 26 parts. Narrator David Attenborough 14: The First Voice
Frogs, it is said, divide their world into three classes - if it's small enough you eat it; if it too big you run away from it; and if it's intermediate you mate with it.
Dr Bob Capranica from Cornell University, New York, describes the way frogs rely on sound in order that they mate with the right object.
Written and produced by MICHAEL BRIGHT BBC Bristol