Frogs are one of the true circular breathers. When calling they can expand their air sacs using air from the lungs, and then the air can be forced from the air sac back into the lungs in a circular path. This allows them to croak continuously, even if they are under water.

How does frog make sound?

Frogs produce sound from the air sac below their mouth that from the outside, is seen to inflate and deflate. Air from the lungs is channeled to the air sac, which resonates to make the sound louder. ... Only the male frogs are able to produce mating calls to attract gravid female frogs.

What do frog croaks mean?

The short answer is this: Male frogs croak after it rains because they're trying to attract a mate. Rain creates the optimal conditions for the females to lay eggs in fresh pools of water. In addition to this, frogs like moist, humid weather. ... By the way, frogs also croak during the rain and sometimes before it rains.