Crocodiles, alligators, and caimans are ancient reptiles. Despite their formidable appearance and reputation for stealth, these animals possess a complex repertoire of communication sounds. The common assumption that they are silent ambush predators is far from the truth; crocodilians engage in a variety of vocal and non-vocal signaling throughout their lives. These acoustic signals play a significant role in their social structure, from establishing territory to coordinating parental care.
The Adult Crocodilian Chorus
The most powerful and widely recognized sound produced by mature crocodilians is the bellow or roar, a loud, sustained vocalization that functions primarily as a long-distance advertisement. This sound is generally used to establish territory and attract mates, making it most common during the breeding season. The bellowing process is a full-body display, often beginning with the animal inflating its lungs and arching its tail, adopting what is known as the “head oblique tail arched” posture.
The bellow itself is often preceded by an infrasonic signal, a vibration so low in frequency that it is mostly undetectable by the human ear, but which travels exceptionally well through water. This low-frequency vibration, often below 20 Hertz, causes the water on the animal’s back to dance and spray in a phenomenon known as the “water dance”. The audible roar follows immediately, a deep, resonant sound with energy concentrated between 20 and 250 Hertz, capable of traveling for a mile or more to signal dominance and availability. While both males and females can produce the audible bellow, the intense infrasound component is typically a sexually distinct feature of the larger males.
Non-Vocal and Contextual Signals
Beyond the powerful bellows, adult crocodilians employ a range of sounds for immediate communication, particularly in situations involving threat or close-range interaction. The most common threat signal is the hiss, which is not a true vocalization but a forced expulsion of air. The hiss serves as a defensive warning, signaling agitation and readiness to fight.
The hiss is a broadband call, lasting between one and three seconds, and is often accompanied by the inflation of the body and an open mouth. For closer-range communication, crocodilians may produce a low growl or a cough-like call used in aggressive or courtship contexts. Non-vocal actions also serve as important signals, such as the rapid closing of the mouth known as a jaw snap or jaw clap, which creates a sharp pop to intimidate rivals. During courtship displays, they will slap their heads against the water’s surface, creating a distinctive splash noise that combines acoustic and visual cues.
Communication Between Hatchlings and Parents
The smallest crocodilians are surprisingly vocal, using specific calls vital for their survival and coordination with their mother. Hatchlings begin communicating while still inside the nest, emitting a high-pitched chirp or peep. This distress call alerts the mother that the young are ready to emerge and need assistance in digging out of the nest, synchronizing the hatching process for safety.
Once the hatchlings have emerged, they continue to use soft, grunt-like croaks to stay in contact with the female. The mother responds with a specific, low grunt or croak of her own, which serves to encourage the young or guide them to the water for the first time. This acoustic connection allows the female to remain attentive to her offspring’s needs, often continuing to provide protection and transport for weeks or even months after they hatch.