In the wet months of the year, it’s common to see frogs in or near ponds, and other water bodies puffing up their throats. But why do they do it?
Frogs puff up and inflate their throat to croak. The part of the throat that gets inflated is known as a vocal sac. Depending on the species, frogs have a single vocal sac under their throat, or vocal sacs on each corner of their mouth.
Generally, frogs croak to attract females of the same species to mate with.
The loud croaking is typically from male frogs – females move towards calling males, and pick the male that they prefer based on their calls.
If you ever see a frog inflating its throat, chances are, it’s a male frog.
Frogs Inflate Their Throats to Croak
Frogs have simple vocal cords that have two slits in the bottom of the mouth. They also have a vocal sac that can amplify the vibrations from the vocal cords.
When calling, a frog closes its mouth and nostrils, and expels air from its lungs through the vocal cords and into the vocal sacs. The vibrations of the vocal cords emit a sound – and the inflating and deflating vocal sac makes the sound louder or quieter.
By forcing air back and forth between their vocal sac and their lungs, the call becomes rhythmical.
The vocal sac is an elastic membrane of skin. It acts as a resonating chamber, causing the male frogs’ mating call to be amplified and carry significant distances.
Most frogs’ have a single vocal sac under their throat, whereas other frogs have a vocal sac in each corner of their mouth.
When a frog calls, the vocal sac will expand, but its mouth won’t open. Sometimes, it may look like the frog staring off while making the sound.
When not calling, the vocal sac of a male frog will appear as loose skin on the throat and is often a different color than the rest of the belly.
Every frog species has a sound that is unique to their species – and the croaks of some species can be heard over a mile away!
Only Male Frogs Can Inflate Their Throats
Female frogs and toads are generally considered to be the quieter sex since they generally lack or have reduced vocal cords.
In almost all species, only the male will croak.
If you looked at the throat of a female frog, it would not not have any loose skin, because female frogs generally do not have vocal sacs.
Other Types of Frog Vocalizations
Loud croaking to attract mates isn’t the only type of vocalization frogs make.
Here are 4 other types of vocalizations that exist in most frog species.
1. Territorial calls
In the mating season, male frogs often form temporary territories to attract females, which they defend from other males. These territories usually occupy the immediate area around an individual.
Breeding male frogs will defend the boundaries of their territories, and scare off other males by using a variety of calls. Some frogs will even fight intruding males.
Research has shown that male frogs of many species can tell the difference between their established neighbors, and unfamiliar strangers. This helps them avoid aggressive encounters with male frogs that hold territory nearby.
Female frogs choose their mates in part by the quality of their call, and their ability to defend their territory.
2. Distress Calls
Many frog species can make “distress calls” when they are grasped by a predator. This call is usually a high-pitched scream that startles a predator causing it to release the frog, enabling the frog to escape.
3. Release Calls
Another type of vocalization is made by frogs that have been unwillingly grabbed by another frog searching for a mate, these are known as release calls.
When a male frog is trying to mate, he may attempt to grab onto any frog that is close to him. If he grabs onto another male frog, a female that has already mated, or a frog of a different species, the grabbed frog will emit a release call – telling the offending male to let go.
The sound of the release call can be different depending on the frog species. In Green tree frogs (Hyla cinerea) the release call sounds somewhat similar to the soft clucking of a chicken. These calls are also sometimes made by the frog if it is being held too tightly in your hands.
4. Warning Calls
Another vocalization in some frog species is a “warning call”, a noise that is made by a frog that has been startled or disturbed. The frog may make a short squeak as it leaps away.
Like other frog vocalizations, warning calls can be different depending on the frog species.
In green frogs (Lithobates clamitans), the warning call is an abrupt iCUP! In American bullfrog (Lithobates catesbeianus), the warning call is a loud eeek!
Common Questions
Why do frogs inflate their throats? Frogs inflate their throat to croak. The part of the throat that gets inflated is known as the vocal sac. The vocal sac is an elastic membrane of skin and acts as a resonating chamber. The inflating and deflating vocal sac causes the frog’s call to be amplified and carried significant distances.
Why do frogs puff up their throats? Frogs puff up their throats when croaking. The skin of the throat that gets puffed up with air is the vocal sac -which is an elastic membrane of skin and acts as a resonating chamber. By puffing up the vocal sac, the croak gets amplified.
Featured image credit: Robert Dobbs (CC BY-NC 4.0 DEED)
Sources:
Hodl, Walter & Gollmann, Günter. (1986). Distress Calls in Neotropical Frogs. Amphibia-Reptilia. 7. 11-21. 10.1163/156853886X00226.
Kentwood D. Wells, Territoriality in the green frog (Rana clamitans): Vocalizations and agonistic behavior, Animal Behaviour, Volume 26, Part 4, 1978, Pages 1051-1063, ISSN 0003-3472, https://doi.org/10.1016/0003-3472(78)90094-5.
Erhard, H. C. (1994). The Evolution of Vocalization in Frogs and Toads. Annual Review of Ecology and Systematics, 25, 293–324. http://www.jstor.org/stable/2097314
Emerson SB, Boyd SK. Mating vocalizations of female frogs: control and evolutionary mechanisms. Brain Behav Evol. 1999;53(4):187-97. doi: 10.1159/000006594. PMID: 10343085.
