If you ever looked at a frog you may wonder how they hear. Unlike cats and dogs, frogs do not have visible external ears. Yet frogs clearly hear us when we approach them since they often hop or swim away. Although a frog’s hearing system, may not always be visible, the can hear their surroundings very well.
Frogs do not have outer ears and generally have a middle and inner ear surrounded by tympanic cartilage, as well as tympanic membranes behind their eyes. Some frog species lack middle ears and tympanums, and they instead use their skin, lungs, or mouths to sense external sound vibrations.
While frogs can technically hear what is going on in their environment, the process is far more complex than it may seem. I’m going to explain frog ears and how they hear so you can better understand why frogs know you are coming even before you reach their location.
Why Don’t Frogs Have Outer Ears?
Frogs do not have outer ears like many other animals, and frogs’ auditory systems are comprised of the internal structures in their heads. They generally have middle and inner ears, which are encompassed by tympanic cartilage and other small bones such as stapes that support hearing and balance.
Most frogs typically have tympanic membranes on their heads, right behind the eyes, which they use for most hearing functions. The tympanic membrane is useful for hearing external sounds on land and underwater. Some frogs have very large tympanic membranes, like American Bullfrogs, whereas it may be less prominent on other, typically smaller frogs.
Frogs may use these tympanic membranes in combination with other body parts for optimal hearing. The tympanum will generally appear to have varying circular or ovular shapes from the outside (CTNF).
Outer ears may be useful for many species, but it would likely be impractical and possibly dangerous for a frog’s semi-aquatic lifestyle. Just imagine, if an aquatic frog had external ears. They would probably fill with water and debris while they drink, breathe, and swim. This would probably be painful.
The tympanic membrane allows frogs to hear and protects them while allowing them to fulfil all their daily activities. Their inner ear or tympanum allows sound wave vibrations to enter while blocking out water and dirt. Such an auditory system is far more adapted to frogs than having external ears.
How Do Frogs’ Ears Work?
Generally, frogs have middle and inner ears, or tympanic membranes, that allow them to hear. Some frogs also use their skin, mouth, or lungs to hear and detect vibrations.
In many cases, frogs will use their tympanic membrane, their skin, and occasionally their lungs and mouth lining for hearing. These body parts are used in similar ways, with a primary focus on the vibrations emitted by the sound in question.
Frogs Can Hear Through Their Tympanic Membrane
The tympanum is still the core of the frog auditory system, and they work by sending signals based on the type of vibration that the sound creates. The inner ear can assess the type of sound and where the sound is coming from through various applications.
Frogs can detect both high and low frequencies in varying parts of the tympanum. Once any sound reaches the tympanic membrane, the soundwave’s vibration will trigger a vibration within the fluid of the tympanum. These tympanic vibrations will then trigger an electrical signal, which will be sent to the frog’s brain (CTNF).
After the frog’s brain receives these signals, the sound will be interpreted based on the initially received vibration. Depending on which side of the head received stronger vibrations, the frog can determine from where the sound is emitting.
Frogs Use Their Skin to Hear
Although frog skin is not technically part of the auditory system, they may still use their skin to assist their hearing. Frogs’ skin is incredibly sensitive, and frogs can use their skin to detect vibrations in the surrounding area as well. The vibrations may not trigger the same electrical signals in the tympanum, but the frog’s brain can still interpret these vibrations.
Some Frogs Can Hear With Their Mouth
Some frog species have adapted their auditory system and use their mouth lining to detect sound. For example, the Seychelles Islands Gardiner’s Frog does not have a middle ear or a tympanic membrane for hearing. But, these frogs still have an inner ear, meaning they need more creative methods to interpret sound wave vibrations.
Sound vibrations are amplified and interpreted within the frog’s sensitive mouth lining, after which it can be sent to the inner ear nearby. Once it reaches the inner ear, similar electrical signals can be sent to the frog’s brain, allowing it to interpret the sound’s type and location.
Some Frogs Can Hear With Their Lungs
Some species, such as Coqui Frogs, are so small that their tympanums are predominantly incapable of perceiving most sound waves. Instead, they use their lungs to detect sound since the lungs have a greater surface area for receiving vibrations.
How Good Is a Frog’s Hearing?
Frogs have a fairly good sense of hearing, depending on the species and the primary system used for hearing. Many species have tympanums larger than their eyes, while others have fairly small tympanums, reflecting their size and level of hearing in some cases.
Some frog species can hear very well, while others may have adapted auditory systems that are less efficient than tympanic membranes and eardrums. Some frogs use Ultrasonic communication via high-pitched sound waves, which typically have frequencies over 20 kHz.
Frogs may also listen to certain sounds in their environment and react to them, while ignoring others. This sort of approach can be compared to what humans refer to as ‘selective hearing’.
Frogs Use Selective Hearing
By using selective hearing, frogs can detect sounds that affect their chances of survival. In many cases, frogs may drown out other sounds and only perceive the sounds that would directly impact them, such a detecting possible threats within their environment, predators, prey and mating calls.
Such uses are advantageous within their habitats, as they can focus on what matters most without overloading their sensory systems. However, the use of selective hearing and interpretation of ultrasonic frequencies can pose potential risks as well.
By only focusing on sound waves, frequencies, and vibrations that are classified as important, frogs may have a delayed response to less common sounds within their habitats. This overall lack of awareness can put them at risk in various ways (CTNF).
More About How Frogs Hear
Frogs need to hear what goes on around them just like any other animal would, and their auditory systems primarily involve the inner ear and the use of vibrations. Although they have more innovative auditory systems, they can still find mates, locate prey, detect threats, and warn their companions of danger within their habitats.