Can Turtles Hear? An In-Depth Look at Their Unusual Ears

Although turtles don't have external ears that stick out from the sides of their heads like humans, they do have internal ear anatomy that enables them to hear both in the air and underwater. Turtles have a middle ear cavity, inner ear bone (columella), and eardrum that are all covered by skin and scales on the sides of their head. While their hearing is not as sensitive as many other species, it is still important for helping them sense prey, predators, and mates.

In this in-depth examination of turtles' unusual ears, we will review biological studies that detail the distinctive anatomy and hearing abilities of different types of turtles. This summary will explain how turtles have evolved their ears and hearing to adapt to life in the water and on land over millions of years.

Turtle Ear Anatomy: Adaptations for Hearing Underwater

Turtles have ear anatomy that is specialized for hearing underwater, which includes a thin tympanic membrane, cartilaginous tympanic disc, columella, and large air-filled middle ear cavities. As illustrated in the schematic diagram in a master's thesis at the College of William & Mary, these structures enable the efficient transmission of underwater sound vibrations to the inner ear.

According to research published in PubMed, turtles are most sensitive to low-frequency sounds around 400-500 Hz underwater. Their middle ear is divided into two parts and does not have a round window but does have a fluid-filled pericapsular recess, which may contribute to their underwater hearing ability. Although the turtle's ear is not well-suited for hearing in the air, the thick tympanum probably helps with the conduction of low-frequency sounds through bone.

As explained in the Britannica entry on reptile hearing, the columella connects the cochlea and saccule directly in the turtle's inner ear, so its vibrations would stimulate both end organs for integrated hearing. Research summarized by PubMed shows that this ear anatomy is consistent across all turtle families, which is consistent with an aquatic origin and specialization for underwater hearing via the resonant middle ear cavity. Nevertheless, the turtle's high underwater hearing thresholds leave them susceptible to harm from human-generated noise.

Frequency Ranges and Sound Reception in Turtles

Turtles can hear low-frequency sounds that are common in the shallow waters they inhabit, such as the sounds of the ocean and boats, which can help with navigation, foraging, and predator avoidance. According to the Discovery of Sound in the Sea, sea turtles seem to have the best hearing between 200 and 750 Hz and don’t seem to respond to sounds above 1,000 Hz.

This hearing range is similar to many fish, which means that turtles can hear both naturally occurring sounds in their environment and human-made sounds like shipping and sonar. A study by NOAA Fisheries showed that adult green sea turtles have the best hearing sensitivity between 200-500 Hz.

Although turtles can hear airborne sounds between 50-2,000 Hz, a study in the PMC journal showed that their sensitivity to underwater sounds is generally greater, especially at lower frequencies. This sensitivity is important for helping turtles navigate, communicate, and detect danger in their underwater habitats.

How Noise Pollution Affects Turtles

Noise pollution in the ocean is on the rise due to human activities such as shipping, construction, and sonar, and it can lead to temporary hearing loss in turtles. Research presented at the 2022 Ocean Sciences Meeting showed that exposure to high levels of underwater noise can result in hearing sensitivity loss that can last for minutes to days, which can impact the turtles' ability to hear important sounds.

One study found that the degree of hearing loss is directly proportional to the duration, amplitude, and sound exposure level of the noise, and that there are individual differences in the susceptibility and recovery from hearing loss. Another study showed that the mean predicted onset of temporary threshold shifts (TTS) in turtles was 160 dB re 1 μPa2 s.

Noise-induced hearing loss can be especially problematic for endangered turtle species because it can interfere with their ability to communicate, navigate, and detect predators and prey. As explained by, "If this occurs in nature, turtles would be less able to detect sounds in their environment on these timescales, including sounds used for communication or warning them of approaching predators." More than half of all turtle and tortoise species are currently at risk of extinction, so it's important to understand and address the impact of noise pollution on these animals.

Differences in Turtle and Tortoise Hearing

Although all turtle and tortoise families have a middle ear that is adapted for underwater hearing, studies have shown that there are likely differences in hearing sensitivity and frequency range based on the species' habitats and behaviors.

It is possible that sea turtles and freshwater turtles have adapted their hearing to the sounds they are most likely to encounter in their respective environments. T. Aran Mooney notes that much of what is known about turtle hearing is based on anatomical models, and these models suggest that some species of turtles are more sensitive to lower frequencies.

On the other hand, terrestrial tortoises probably rely more on bone conduction for hearing and therefore have different hearing needs than their aquatic relatives. A study published in the PMC journal showed that the removal or cutting of the columella led to a significant decrease in aerial hearing sensitivity in sea turtles, but only a small decrease in vibrational hearing sensitivity, suggesting that the two types of stimuli are processed differently.

To better understand the unique adaptations and differences in hearing abilities of different turtle species, researchers are using Auditory Evoked Potentials (AEPs) to study and compare the underwater auditory thresholds of turtles in different environments.

Conclusion: Why Protecting Turtle Hearing Matters

Turtles have evolved unique ear structures and hearing capabilities that enable them to detect sounds in both aquatic and terrestrial environments, which is critical to their survival. Their sensitivity to low-frequency sounds is particularly important for navigation, communication, and detecting predators and prey. However, the rising levels of underwater noise pollution are a major threat to turtle hearing, potentially causing temporary or permanent hearing loss and affecting their survival and well-being.

Conservation efforts need to take into account the impact of noise pollution on turtle populations, especially those of endangered species, and take steps to mitigate these impacts in order to protect their hearing.