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Vocal sac

life science Maturity 9-11 Next article →

Most male frogs and toads have a vocal sac.

Litoria chloris calling
Litoria chloris calling

This is a flexible pouch made of skin. It helps them make very loud calls. These calls are often for mating. The sac is a way to tell if a frog is male. Scientists look at the sac to find the sex.

BennyTrapp Hyla intermedia Italien
BennyTrapp Hyla intermedia Italien

It is an important part of how they live.

To make a sound, the frog follows a few steps. First, the frog fills its lungs with air. Next, it shuts its nose and its mouth. Then, it pushes the air out of its lungs. The air goes through the larynx. This is a part that creates vibrations. The air moves into the vocal sac. The sound vibrates on the elastic skin. This is called amplification. It makes the sound much louder.

Litoria chloris calling
Litoria chloris calling

Muscles help push the air back and forth.

Many species grow their sacs in a similar way. A single-lobed sac starts as two small growths. These growths are on the floor of the mouth. They grow into two small pouches. These pouches expand until they meet in the middle. They form one large cavity. This cavity grows until it is fully developed. This is how the pouch becomes ready to use.

Some frogs do not have these sacs. These frogs often live near flowing water. The sound of the water is very loud. It can overpower the frog's call. Without a sac, a frog is heard only a few metres away. Some frogs with sacs can be heard much further.

BennyTrapp Hyla intermedia Italien
BennyTrapp Hyla intermedia Italien

This helps them attract females from a large area.

Some frogs use the sac for a different job. This happens in the Rhinodermatidae family. Males scoop up newly hatched tadpoles into their mouths. The tadpoles then move into the vocal sac. In Darwin's frog, they stay there until metamorphosis. Metamorphosis is when they change into adults. The Chile Darwin's frog moves them to water.

Litoria chloris calling
Litoria chloris calling

This is a very special way to care for young ones.

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File:Litoria chloris calling.jpg
Litoria chloris calling.jpg
File:BennyTrapp Hyla intermedia Italien.jpg
BennyTrapp Hyla intermedia Italien.jpg
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