Ever wondered just how frogs hear? I know I often wonder about this when I listen to their evening calls at the little fishpond I have in my backyard.
When the males become really excited, they can kick up quite the ruckus, and if it hurts my ears, what does it do to the ears of the other frogs?
Just how do frogs hear?
How Frogs Hear
Frogs have circular openings behind their eyes, which are openings to their internal ears. A frog has an internal eardrum, or membrane, that allows them to hear by vibrating in response to sound. Interestingly, frogs have their ears connected to their lungs to help them equalize the pressure in their ears from loud sounds.
The Frog Hearing Process
Frog hearing is quite similar to people’s, except frogs have no external ears. Both frogs and humans have a thin membrane called an eardrum, which vibrates to sound waves.
The vibrations then travel down the small bones of the inner ear that are connected to each other and to the eardrums. The inner ear is made up of delicate bones: the cochlea and the eardrum, or tympanum.
In some frog species, the sound waves travel into one ear, where they are processed and sent to the other ear. Frogs hear twice then!
Most frogs hear lower sounds better than the high-pitched ones. This is why most mating calls among frogs are quite low in tone.
So my bullfrogs that are breeding in the fishpond have a low and deep croak to attract their females as this sound would be heard best.
Frog Adaptations for Hearing
Frogs are not quite like people in the way they hear.
While they also translate sound waves into electrical impulses, they are adapted for different sounds and hear for specific reasons.
Adaptation One: Species-Specific Hearing
One of the main adaptations that frogs have is that they mostly hear what they are supposed to, unlike my husband who hears what he’s not supposed to.
Frogs are programmed to hear the calls of their own frog species. Females frogs are able to distinguish the mating calls of their own species’ males from amid a din of frog croaks.
This is obviously an adaptation to ensure breeding can happen and the frog species can survive. To further help this adaptation along, frogs all croak at different frequencies.
So the New Jersey cricket frog has a croaking frequency of 3,500 hertz. Therefore, the females of the cricket frog species are unable to hear the mating calls of males from other species.
They are effectively deaf to anyone other than their species’ males.
Adaptation Two: Inner Ear Structure
The frog’s inner ear is very similar to a human ear.
There is the tympanum or eardrum that is visible from the outside with frogs, and then there is the inner ear that has a bone attached to it, which vibrates to create sound waves that will trigger the ear glands to send a message to the brain.
Frogs’ eardrums work perfectly above and below water. They can regulate pressure by opening or closing their mouths, just like a human would yawn to adjust their ear drum pressure.
Adaptation Three: Sexing Frogs Based on Ear Drum Size
With some frog species, it is possible to tell which frogs are male and which are female based on the size of their tympanum. I was amused to hear that male frogs have larger tympanums than female frogs do.
Perhaps they were able to listen better than their human counterparts?
This adaptation is to help the male hear the much softer female frog’s croaking. When the male frog is croaking, you will often see their tympanum enlarge and blow up like a hot air balloon.
Adaptation Four: Head Shape
Even the size and shape of a frog’s head are designed to act as a resonance chamber. This means sound travels into their mouths, and from here, it vibrates, drowning out other noises.
For some frogs, the ability to hear is determined by their mouths and the resonance chamber that their heads form. There are other frogs that don’t have any ears either, making them completely deaf.
Adaptation Five: Lungs Vibrate
In frogs, their lungs can sometimes be adapted to vibrate to high-pitched frequencies.
These vibrations help the frog hear higher-pitched sounds. Imagine being able to hear with your lungs!
Frequently Asked Questions about How Frogs Hear
Do frogs hear with their mouths?
While frogs can create vibrations with their lungs, they often rely on hearing via their tympanic membranes. But what about the frogs that have no ears? When a frog has no ears, they begin to vibrate their lungs, which means they can hear with their lungs.
Can a frog hear a sound?
Frogs do hear sounds; however, their ear glands are programmed to focus on the sounds that are relevant to them. A frog may hear their mate calling or the scurry of a predator approaching. Yet that frog won’t necessarily hear the calls of another nearby frog that is of a different species.
The Final Croak
Frogs hear in challenging circumstances, and their ears need to function both during and after their meetings. Amphibians, like frogs, are special in that they have unique hearing.
Next time I hear the frogs croaking in my backyard, I will be sure to really appreciate just what it is about frogs that make people feel drawn to them.