Reptiles make a variety of clicks, chirps, grunts and hisses. Turtles and tortoises are surprisingly vocal too.
Geckos are the chattiest lizards, making chirps and squeaks for territorial purposes or as mating calls. Some species will hiss as a defensive strategy. Crocodiles are capable of roaring to communicate their presence and intent.
Lizards
Although lizards are often thought of as silent creatures, the truth is that they actually make quite a few sounds. In fact, lizards can make clicks, grunts, chirps, barks, and even hisses! These sounds are used to communicate with other lizards or warn them of danger.
Some lizards, such as chameleons, use vocalization to attract potential mates. They will chirp or sing to try to get the attention of a female. This is known as a courting call. Other lizards, such as horned lizards, make hissing noises to warn other lizards of their presence. They also make hissing sounds if they feel threatened or are in danger of being killed by another animal.
Other lizards, such as geckos, may make sounds by vibrating their bodies or rubbing their scales together. They can also make sound by squeaking their tongues.
Most lizards have good auditory sensitivity, but they have limited hearing in the lower and higher tones. They are able to hear sounds with frequencies up to 4,000 hertz. They also have a wide variety of inner ear structures, with some having tympanic membranes and others not. Those lizards that live a more subterranean lifestyle usually lack the tympanic cavity and ear canal. Some lizards, such as skinks, have high-pitched cries that are a form of distress calls.
Crocodiles
Crocodiles and alligators are well-known for their ability to roar, but researchers have discovered that these reptiles are capable of more than just that. They also make grunts, hisses, and other sounds to communicate a range of emotions, including aggression, fear, and submission.
The sounds crocodiles make are created by forcing air through their larynx, which opens and closes in order to produce different pitches. The hisses and growls they produce are used to convey different emotions, while the roar is usually used to signal danger.
A roar is a full sound that has a low, deep pitch. This sound is created by a combination of factors, including the length of the vocal cords and the thickness of the throat. These animals use their roars to scare off predators and other competitors, but they may also use them as a way to mark their territory or communicate with other crocodiles.
Researchers recently studied the way Nile crocodiles respond to the calls of distressed juveniles. They found that the reptiles were more likely to draw attention to calls that exhibited certain characteristics, such as chaotic sounds and jitters. This suggests that the crocodiles were better able to judge how upset or distressed a baby was. The crocodiles did not seem to be drawn to the pitch of the call, which could be because that cue was less useful for the reptiles since it changes between species.
Snakes
Research into snakes suggests that, although they lack external ears and eardrums, they can still detect vibrations caused by sound-induced ground movement. They likely receive these vibrations through the lower jaw, which normally rests on the ground, the quadrate bone, and the stapes (also called the columella auris). The stapes transmits the sound pressures to the inner ear where they are processed as sounds. Burrowing lizards also probably perceive ground vibrations in the same way.
Snakes vocalize primarily as a defense mechanism, and their hissing and rattles serve to warn potential predators to stay away. They can also produce rattling noises by pushing air through their cloacal vent (which is located in the back of their neck) instead of through their nose and mouth. This sound is similar to that of a person breaking wind and it can be heard from a great distance, telling the potential predator to back off.
Bull snakes, in particular, make a noise known as the “bellow,” which is comprised of two parts: a short burst of high-amplitude sound that resembles a growl and a longer period of low-amplitude, constant-frequency sound that resembles a hiss. The researchers found that the snakes’ skulls vibrated in response to these sounds. Interestingly, their brains did not respond to the sounds, which suggests that they are perceiving the vibrations through bone conduction, just as fish use their swim bladders and we do when we hear by bone conduction in water.
Turtles
For a long time, scientists assumed that turtles were both incapable of vocalization and completely deaf. But Camila Ferrara, a researcher with the Wildlife Conservation Society, helped put that misunderstanding to bed in October when she and her colleagues published research showing that some 50 turtle species (as well as lungfish, tuatara and worm-like amphibians) make sounds. These include chirps, snorts and clicks, along with some that are used to defend territory, woo females and fight other males.
Specifically, Ferrara and her team recorded clicks made by the baby turtles of the giant South American river turtle. These calls help the babies synchronize their hatching and locate each other. They’re also used to communicate with adults and their offspring, which the researchers found by playing recordings back to Chelodina mccordi and Pangshura tecta turtles that reacted to them by pulling their heads away from their shells or turning their heads toward the source of the sound.
Other sounds produced by the turtles included mounting-calls, which indicate the size of a male. And based on the sounds’ evolutionary history, the researchers believe that turtle vocalizations date to a common reptile ancestor about 407 million years ago. That’s 100 million years earlier than previous research had suggested. Moreover, the study’s results also show that tetrapods—the vertebrates with backbones that include mammals, birds and reptiles—began to use sounds more than 400 million years ago.