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Reptiles Make a Surprising Amount of Noise. Here’s What Those Sounds Might Mean, From Pops to Hoots to Bellows
Scientists are realizing that turtles, lizards and crocodilians communicate vocally more than they once thought
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Along the sandy banks of northern India’s Chambal River, crocodile-like gharials glide silently through the water—but if a gharial spots a stranger, the quiet may be punctuated by a series of explosive pops.
That popping sound—like a champagne cork being released from a bottle—has only recently come to scientists’ attention. It’s unique to male gharials and results when one of the large reptiles fills its nasal cavity with water and then exhales rapidly: The water shoots through a bulbous outgrowth at the tip of the creature’s long snout. The sounds, which are often produced in sequence, appear to broadcast the male’s identity—each gharial’s “pop pattern” is unique.
The gharials aren’t the only reptiles making surprising noises. While mammals and birds are better known for their vocal communication skills, reptiles aren’t just quietly slinking about in the wild—they create their own soundscapes with chirps, squeaks, bellows and roars.
As researchers discover more of these sounds, they are also beginning to determine the importance of such vocal chatter to the animals’ social lives, from mating to parent-offspring interactions. Reptiles have largely been thought of as secretive creatures and “underappreciated for a long time with regard to social behavior,” says conservation biologist Sean Doody of the University of South Florida.
Of the thousands of reptile species out there, “most of them are not studied at all,” says Henrik Brumm, a behavioral biologist at the Max Planck Institute for Biological Intelligence in Germany. Now that scientists are taking note of these varied vocalizations, says Brumm, the idea is to “better understand what they’re saying.”
Syncing up with siblings
When it comes to talkative reptiles, crocodiles are among the best-studied. Scientists have long known that, like their bird cousins, baby crocodilians produce sounds while they are still in the egg. These noises appear to synchronize hatching among siblings and to call their mom for help extracting themselves from their eggshells and leaving the nest. But over the past decade or so, it’s become clear that many turtles, too, make various clicks and chirps from within the egg.
To better understand turtle noises, evolutionary biologist Gabriel Jorgewich-Cohen, now at the National Institute of Amazonian Research, and colleagues looked at species with chatty turtle babies, such as the South American river turtle, as well as more taciturn species, such as the western swamp turtle. The researchers found that while South American river turtles—which lay clutches of more than 100 eggs—have noisy turtle youngsters that synchronize their nest exit, hatchlings of species that lay fewer than ten eggs are less likely to vocalize and to leave the nest together.
This suggests that chitchat made by turtle tykes from large broods may help synchronize hatching, which can help the hatchlings work as a team to dig their way out of their underground nests. And since they have many siblings, making noise is not so risky: Their individual chance of being gobbled up by predators is low, says Jorgewich-Cohen.
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Lizard hoots and squeaks
Vocalizations have also been detected in some 30 percent of lizard families. Chameleons, for example, hoot and bark when they interact with each other, and anoles squeak and growl when distressed.
The Chilean tree iguana, also known as the weeping lizard, can even modulate its distress call. When the lizard is stressed by a predator, for example, it emits simple squeaks. But if things are really dire, the iguana shifts to more complex calls that convey more urgency.
These complex calls have varying frequency and pitch, which result from the weeping lizard’s vocal cords vibrating out of sync. And they seem to inspire fear: The complex calls, more than ordinary calls, prompt nearby lizards to sit perfectly still for longer before escaping—and to spend more time trying to escape. One recent study found that hearing this distress call while witnessing a fellow lizard getting eaten by a snake also triggered a more prolonged fear response. Complex distress calls with more chaotic sounds have also been reported in mammals such as meerkats and human infants and may indicate urgency to the listener.
Geckos, too, can modulate their calls in sophisticated ways. The tokay gecko, with a loud call usually preceded by a series of soft cackles, typically vocalizes to find a mate or defend its territory. As with many birds, these calls are governed by testosterone and are more frequent in the spring, similarities that inspired Brumm to investigate further.
Brumm wondered if these geckos would automatically increase the loudness of their sounds when in noisy surroundings—a phenomenon known as the Lombard effect that has been observed in many birds and some mammals. “Humans do it every day,” says Brumm. “If a bus is driving by your window, without thinking about it you will speak louder.”
So Brumm and colleagues played white noise to geckos in the lab and measured how they adjusted their calls in response. The geckos didn’t dial up the volume of their whole call. Instead, they changed its pattern, reducing the number of soft cackles and letting out longer “geck-o” sounds—the louder part of their call. In the noisier setting, they also adjusted by drawing out the “o” syllable, which made the call more audible. Humans, monkeys and some birds do this as well, evident in the way people draw out their vowels and speak slower to be heard better.
“This was completely unexpected,” says Brumm. “It shows a flexibility in the communication of the reptiles that people would not have thought possible.” His findings suggest that gecko calls are more complex, sophisticated and “much more similar to the intricate things that birds and mammals do than we previously thought.”
Bellows and pops with a purpose
The croons of some geckos vary based on their size—larger barking geckos let out deeper, lower-frequency chirps than more petite peers, for example—suggesting that they may be advertising their might to potential mates. American alligators also emit bellows based on their size—research suggests that the lower the frequencies of the bellow, the larger the animal. But in the case of the alligator-like gharial and its pops, the signal seems to broadcast the identity of each individual male.
Quick fact: Gharial conservation
The gharial is classified as critically endangered, with a few hundred adults likely remaining in the wild in India and Nepal. Since the 1940s, it has experienced a population decline of up to 98 percent.
Working with the Gharial Ecology Project at the Madras Crocodile Bank Trust in India, conservation biologist Jeffrey Lang and project director Jailabdeen A recorded the popping sounds along the Chambal River. Underwater, the male gharials would first emit sub-audible vibrations, followed by either a single explosive pop or a series of pops in quick succession—a pop pattern. The 16- to 20-foot-long creatures would then emerge above water, do an exhalation-inhalation-exhalation sequence, and end by burbling back into the water.
The sounds varied based on the social context: Some pop patterns seemed to alert others to a disturbance; another pop pattern was for patrolling territory. One male had a 22-millisecond-long pop for alerts but a longer, 35-millisecond one while patrolling. The male gharials also let out pops when faced with a potential challenger male, or as a courtship call. And each male had a different pattern of pops for each context.
An individual’s unique pop signal may communicate parental qualities and help females in identifying the best fathers. Gharial males are caring, involved fathers that protect their hatchlings in the water. For the gharial female, this fatherly quality is perhaps more essential than the size of the males.
The pops seem to serve a variety of important purposes, says Lang, sending signals to individual males or females or to the whole group. Yet the scientists still aren’t sure exactly how the animals generate their pops. The bulbous outgrowth at the tip of their snout called the “ghara” (“mud pot” in Hindi) seems essential; males that lose the ghara in fights cannot pop like their peers. The various flaps and cavities inside the bulbous organ could cause some resistance to the water gushing in, and their forceful displacement could potentially end up in a loud pop sound, researchers think. But Lang wants to put a gharial inside a CT scanner to confirm this.
This is just one of many mysteries awaiting elucidation as the known repertoire of reptile vocalizations grows. Doody, who published, with Jorgewich-Cohen and others, an overview of the creatures’ diverse sounds in the 2025 Annual Review of Ecology, Evolution and Systematics, hopes that more scientists will take on the task.
“One of the challenges of reptiles is they do something interesting and then they sit there for hours and hours and hours doing nothing,” Doody says. For these animals, “you need tremendous patience.”
Knowable Magazine is an independent journalistic endeavor from Annual Reviews.