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Frog Vocal Sacs

4-16-13  vocal sacs“Peeps” and “quacks” fill the air these days.  How is it that these frog calls travel so far?  It’s all thanks to a thin membrane , or sac, that most frogs have. Note the single inflated sac of the spring peeper, and the paired sacs on either side of the wood frog’s head. These vocal sacs act as resonating chambers, causing the male frog’s mating call to be amplified and carried far (some species of frogs can be heard over half a mile away). Most frogs have one of three basic types of vocal sacs: a single throat sac (the most common), paired throat sacs (partially separated by connective tissue) and paired lateral sacs (completely separate chambers on either side of the head). Vocal sacs are outpocketings of the floor of the frog’s mouth. When calling, a frog closes its mouth and nostrils, and expels air from its lungs through the larynx and into the vocal sacs. The vibrations of the larynx emit a sound which resonates within the vocal sacs. The frog continues calling as muscles within its body wall force the air back and forth between the lungs and vocal sac. The thickness of the vocal sac wall in frogs varies. Typically, small frogs that call in the air (spring peeper) have thin vocal sac walls, whereas those that call in the water, particularly large species (green and bull frogs) often have thick-walled vocal sacs that appear swollen, not inflated like a balloon, when filled with air.

4 responses

  1. Emmylou

    Frogs quack?i didn’t know that!

    April 17, 2013 at 4:35 pm

    • Well, I use the word “quack” loosely — wood frogs sort of sound like ducks, but maybe more like two rocks being hit together?

      April 23, 2013 at 11:01 pm

  2. karen

    Spring peepers’ peeping is my favorite sound and your informative comments make my day. What is the difference between the “peeps” and “quacks” we hear from the same area? It seems that during the day we hear the quacking and the peeping in the evening.

    April 21, 2013 at 7:43 pm

    • You’re right, peepers are more vocal at night than wood frogs, but both are active during the day.

      April 23, 2013 at 11:00 pm

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