Reptile Vocalizations

Most people think that reptiles like snakes and lizards are mute animals. But they can hiss and click, and crocodiles often roar.

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In a study, researchers discovered that some cold-blooded vertebrates that were previously assumed to be mute also vocalize. Scientists figured this out by studying their evolutionary ancestors.

Crocodiles and Alligators

Whether they’re snoring on the shore of a lake or hissing in the dark of a swamp, crocodiles and alligators make quite a racket. The sound produced by a crocodilian when it’s feeling agitated or annoyed is called a growl, and it signals to those around the reptile that they better back off. If the situation continues to aggravate the animal, the creature may then begin hissing or even bite.

Baby alligators chirp, a high-pitched call that sounds similar to the chirp of a bird or peep of a tree frog. They chirp when they hatch out of their eggs, and they continue to chirp when they’re in trouble or trying to communicate with their mothers.

Adult gators produce low, deep growls, and males known as bulls make a booming sound called bellowing during the breeding season to attract females or to ward off other males. These noises come from the animal by blowing air out of its lungs, and they can be heard from as far as 165 yards away.

Both crocodiles and alligators have razor-sharp teeth lining their snouts, and the croc’s jaw can exert more pressure than a T-Rex! While crocodilians are usually found in freshwater habitats, such as rivers, lakes and swamps, researchers believe that some species of crocodiles are able to live in marine bodies of water.

Lizards

Though lizards are often thought of as silent creatures content to bask in the sun and catch bugs, these scaly creatures can make sounds for a variety of purposes. From clicks and chirps to hisses and growls, lizards use vocalizations in a variety of ways to attract mates, warn of danger, or signal dominance to other lizards.

Some lizards, such as chameleons, have vocal cords that allow them to produce sound by vibrating their larynx. Other lizards, such as geckos, may create noise by rubbing their scales together or vibrating their bodies. These noises range from clicking to chirping, much like bird song.

For example, hissing noises produced by horned lizards are used to deter predators and rivals. Other lizards use calls to attract mates or defend their territory. For instance, male chameleons make a series of chirps and clicks to serenade potential mates.

Studies have shown that lizards can detect and respond to a wide variety of tones, including those between 100 and 700 hertz. However, attempts to train lizards to respond to tones have not been successful. It is believed that snakes are able to hear sounds through vibrations in the ground, which are transmitted to their inner ear via the lower jaw, quadrate bone, and stapes. In addition, the sensitivity of the snake ear varies by species.

Snakes

A snake’s vocalizations usually serve as a warning to predators. Hissing, the sound a snake produces by forcibly blowing air from its mouth and nose, is meant to scare away any predators that come too close. The rattling noise a snake produces by squeezing its tail is another defensive mechanism. A rattlesnake’s rattle is made of tough keratin, which resembles the material that makes up human fingernails. Keratin fits loosely together at the end of a snake’s tail, and as the snake vibrates its tail, the hard pieces click against each other to make a rattle sound. Rattling is usually used to warn other snakes, but a rattlesnake will also rattle if it feels threatened or angry.

A study published in the Journal of Experimental Biology found that snakes can hear sounds at frequencies up to 85 dB, which is the equivalent of a human screaming. However, snakes’ hearing performance drops off rapidly at frequencies higher than 200 Hz. The researchers concluded that hissing, rattling, and other snake sounds are produced by the same structure in a snake’s throat, an oblong piece of tissue called the epiglottal keel. The keel sits in front of the snake’s windpipe opening and splits air flow like a boulder might divide a river, forcing the remaining air through narrower paths and amplifying the initial burst of sound.

Turtles

Turtles hiss by pushing air out of their lungs as they retract their bodies into their shells. This is a natural, defensive behavior and doesn’t signal aggression. If the turtle’s lungs are too full to retract, they’ll emit a grunting sound that’s shorter in duration than hissing. Hissing also occurs when a turtle is breathing too fast, which can be a sign of illness.

A roaring sound is specific to big-headed turtles (Platysternon megacephalum). This noise is also a sign of stress, but it can also indicate that the animal is hungry or sick. Hissing is more common in baby turtles as they hatch from their eggs. They make this sound to synchronize their hatching and increase their chances of survival in their first moments of life.

The sounds that turtles make can include clicks, croaks, crackles and chirps. Some of these sounds can be heard, but others are too low to be detected by humans without special equipment. Some turtles, including the Malagasy radiated tortoise, emote mount-calls, which are like long, high-pitched barks.

Researchers have also discovered that turtles are sensitive to low frequencies in the range of human hearing. “If you’re snorkeling underwater looking for turtles, you won’t hear them because they’re making very low-frequency sounds,” Vogt says. Before the recent research, many experts considered turtles to be mute and put them in the same category as snakes and other reptiles that don’t vocalize. But after Gabriel Jorgewich Cohen listened to captive turtles, lungfish and caecilians (a genus of limbless amphibians), he came to a different conclusion: turtles are far more likely to produce sound than previously thought.