Frogs croak for many different reasons, but usually it is only the male who makes the noise. The females seem to think the sound is very attractive and move towards the sound. If you watch frogs croak you will often see the frog puff themselves up in order to make the sound.
Why is it important for a croak to be loud enough to travel long distances? How does it help the frog if only males croak? How many different croaking sounds can you hear these frogs make?