The most recognizable aspect of a frog is its “call.” Each species has a unique call and it is how females are able to find males even when numerous other species of frog are calling.
The production of sound or “call” is a product of the respiratory system. A frog forces air out of its lungs and into its throat, or buccal cavity. As the air moves across the vocal cords, the chords vibrate producing a call. Some species of frog have vocal sacs that function as resonating chambers that intensify the call. Vocal sacs can be located below the chin or paired on the side of the head.
There can also be variations within calls, including regional dialects. Although there are some species where the female will vocalize, in Virginia only the males will call. Although vocalization is primarily for attracting a female, there are many other reasons why frogs call.
The most common calls are 1) Advertisement, 2) Encounter, 3) Release and 4) Distress.
The Advertisement call is used by the male to attract a female. Even in a large choruses, a female is still able to single-out an individual male that it finds most attractive.
The Encounter call is used to defend territory from an intruding male. If the intruder continues to encroach, the defending male may actually attack the intruder.
The Release call is typically used by the “explosive breeders”. It is during these frenzied breeding events that a male may accidentally jump on the back of another male. The male being pursued will emit a release call to announce to the other male to release him. This commonly occurs in American Toad breeding events.
One of the more odd calls, is the Distress call. The American Bullfrog will emit a cat-like scream when grasped by a predator. The belief is that the high pitch scream will startle the predator and release it.
Want even more frog facts and calls? Check out our Guide to the Frogs and Toads of Virginia, available from ShopDGIF.com, a 44-page field guide that covers all 27 species of frogs and toads that inhabit Virginia. Their calls have been captured on a high quality CD that can be easily listened to in the field, classroom, or at home!