Frog Tympanic Membrane

s a kid, it was very intriguing to me how the frogs in our yard could hear.

One time I inadvertently let the dog out while Toady was hopping around in the yard and you bet the dog bark startled him.

But how can a frog hear anything with no visible ears?

Generally, frogs can hear thanks to their tympanic membrane that is situated on their heads behind their eyes. Frogs also pick up vibrations through their skin allowing them to interpret their environment. Some frogs can also hear with their lungs or mouth lining.

But frogs and toads can hear very well.

How else would they hear their mating calls in the Spring?

Let’s dive further into where frogs’ ears are situated, how they hear, and look at very cool exceptions to ways frogs hear.

Frogs Hear Using Their Tympanic Membrane

As a general rule, frogs have a tympanum situated behind their eyes allowing them to hear on land and underwater.

When a sound reaches their tympanic membrane it vibrates the fluid in their inner ear, sending an electrical signal to their brain which they can then interpret.

Frogs can pick up low-frequency and high-frequency vibrations in different parts of their ears.

Depending on which side of the head the sound is stronger, this can help frogs decipher where the sound is coming from. 

Frogs do not have outer ears like humans but they do.

But they have a middle and inner ear housed by tympanic cartilage.

Frogs also have other bones in their ears such as stapes which help the frog hear and stay balanced.

As you can see in the picture above, American Bullfrogs have a very prominent tympanum. Frogs may also use their skin to pick up and interpret vibrations.

Some Frogs Have Adapted Their Hearing

With over 7,500 known frog species around the world, how frogs hear may vary.

Some frogs do not have tympanic membranes and use other methods to interpret sounds around them.

Frogs that do not have tympanic membranes generally hear with their lungs or mouths. Others can pick up ultrasonic calls that humans and other species cannot hear.

Here are exceptions to how frogs hear:

• Coqui Frogs Hear With Their Lungs: Coqui Frogs can hear with their lungs. Since Coqui Frogs are so small their tympanic membranes are not capable of picking up much sound, and so the frog is capable of using its lungs to hear since their lungs have a larger surface area. 
  
• Seychelles Islands Gardiner’s Frogs Hear With Their Mouth: Some frogs like the Seychelles Islands Gardiner’s Frogs do not have tympanic membranes or middle ear to hear, and instead, use their mouth to amplify and interpret sound. The sound is picked up by their mouth instead of a tympanum and is then sent to their inner ear.
  
• Some Frogs Can Hear Ultrasonic Calls: Some frogs can hear using Ultrasonic communication via high-pitched sounds over 20 kHz in frequency, exceeding what humans can hear. Some frogs may do this to favor selective hearing to further adapt to their environments and drown out less useful sounds (CTNF).
  

Frogs Use Selective Hearing to Survive

I was talking to my grandmother about something she wasn’t interested in, and she changed the subject pretending she couldn’t hear me.

Then I was talking to my Aunt all the way at the other end of the room about something my Grandmother was interested in, and she chimed into the conversation like she was there with us!

My Aunt jokes it’s because she had her “Whisper 3000” in her ears. But this is something we all do: selective hearing.

Frogs use selective hearing for survival purposes. You can hear them at night during mating season, calling and croaking trying to attract mates.

Frogs may selectively hear their own species in order to mate with the right partners.

Frogs also selectively hear predator warning signals in order to avoid being eaten. 

In order to further adapt to their environments and drown out useless noise, frogs may also communicate with ultrasonic calls.

This can be an advantage to their survival in order to detect mates and predators, while not overloading their sensory system.

But selective hearing can also cause delays in reactions to less common sounds in their environment putting them at risk.

Some frogs are very sensitive to sound and vibrations, such as African Clawed Frogs. Too much vibration in the water can overload them leading to vomiting, and even lead to death.

Common Frog Ear Questions

How do Frogs Hear? Generally, frogs that have a tympanic membrane have a middle and inner ear that pick up vibrations. The middle ear amplifies vibrations and sends them to the inner ear which is filled with fluid and in turn, sends an electrical signal to the part of the brain that interprets sound.

Why Do Frogs Need to Hear? Frogs need to be able to hear for a number of reasons including to detect mating calls during mating season, to sense, locate and avoid predators, to sense locate and eat prey, and to hear warning calls of other frogs about predators.

Why Don’t Frogs Have Outter Ears? Frogs do not have outer ears because if they did, they would probably get filled with water and debris. Frogs can hear on land and underwater thanks to the tympanic membrane that is situated on their heads behind their eyes. This membrane only lets in sound and keeps water and dirt out. 

Do Frogs Have Ears? Generally, frogs have middle and inner ears to hear sounds and vibrations via a tympanic membrane that is situated on their heads behind their eyes. Some frogs can also hear with their lungs or mouth lining.

Do Toads Have Ears? Generally, earlessness is common in the True Toad Family (Bufonidae) for which the tympanic middle ear is missing in more than 200 species. Toads that do not have ears or tympanic membranes may hear with their lungs or mouth.

Can Frogs Hear With Their Lungs? Some frogs are so small their tympanic membranes are not capable of picking up sound, and so they instead use their lungs or mouths to capture vibrations to hear. For example, Coqui Frogs can hear with their lungs and Seychelles Islands Gardiner’s Frogs hear with their mouths.

Sources

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Pereyra, M., Womack, M., Barrionuevo, J. et al. The complex evolutionary history of the tympanic middle ear in frogs and toads (Anura). Sci Rep 6, 34130 (2016). https://doi.org/10.1038/srep34130

European Synchrotron Radiation Facility. “Frogs that hear with their mouth: X-rays reveal a new hearing mechanism for animals without an ear.” ScienceDaily. ScienceDaily, 2 September 2013. <www.sciencedaily.com/releases/2013/09/130902162712.htm>.

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