Why do some frog species in the family Ranidae have vocal pouches on the sides of their throats? What role does this feature play?

I've known that some Ranidae species, such as leopard frogs, wood frogs, and pickerel frogs (and there are others) have vocal pouches on the sides of their throats, while some in the same family...

18 May 2015 3,519 6 View