Photo credit: Ever Edrey Hernández Cuadrado – (Colombia)
Review: Abdel Rahman El Gamal (Founder of the website)
The vocal sac or pouch is a flexible membrane of skin possessed by most male frogs and is found below its mouth. The vocal sac is used by males to call and attract females from a large area as a part of mating. It is believed that vocal sacs of some species can be heard over 1 km away.
When a frog calls, it inflates its lungs and shuts its nose and mouth. The sound is produced by expelling the air from the lungs, through the larynx, and across the vocal cords. The resulting sound vibrations are amplified by the resonating qualities of the vocal sac.
Muscles within the body wall force the air back and forth between the lungs and vocal sac and hence the sound is produced without expelling air.