Turtles were long considered silent creatures, a misconception stemming from their lack of vocal cords and the subtle nature of their sounds. While they don’t possess vocal cords like many mammals, recent scientific studies reveal they produce a surprising array of noises. These sounds are often low-frequency or quiet, making them difficult for humans to detect without specialized equipment. Despite this, turtles actively use these vocalizations for various forms of communication, challenging the notion of them being entirely mute.
The Spectrum of Turtle Sounds
Turtles produce a diverse range of sounds, including grunts, chirps, clicks, growls, croaks, and even purring sounds. Hissing is a commonly heard sound, often produced when a turtle feels threatened or is handled, resulting from air rapidly expelled from their lungs. Smaller species and young turtles may emit higher-pitched squeaks and chirps, which can sometimes be heard during periods of stress or excitement.
Some aquatic species, like the Western Australian longneck turtle, produce complex, percussive calls, often in frequencies below 1,000 Hertz, well-suited for underwater travel. Giant Amazon River turtles are known for low-frequency sounds that assist in navigation through murky waters and communication during communal nesting. Larger tortoises, such as the Galapagos giant tortoise, can produce deep grunts and moans, particularly during mating rituals. The specific types and volumes of sounds vary significantly across species, reflecting adaptations to different environments and social behaviors.
Reasons Behind Turtle Vocalizations
Turtle vocalizations serve various purposes for intraspecific communication. During courtship and mating, males of many species produce distinct sounds. These range from grunts and moans in larger tortoises to chattering or buzzing sounds in aquatic species, used to attract mates and signal their presence. These mating calls can be loud and carry over considerable distances, attracting females and asserting dominance over rival males.
Turtles also use sounds as distress signals or defensive mechanisms. A common hiss, for example, occurs when a turtle rapidly retracts its head into its shell, forcing air out. This sound can startle potential predators. Communication extends to interactions between mothers and hatchlings; some species, like the Arrau river turtle, use vocalizations to attract attention and potentially synchronize hatching. Low-frequency sounds are particularly effective for communication over distances, especially in aquatic environments, and are used by hatchlings to coordinate emerging from their nests.
How Turtles Produce Their Sounds
Turtles produce sounds using mechanisms distinct from the vocal cords found in mammals. Their vocalizations primarily involve the respiratory system, specifically the larynx and glottis, along with the forceful expulsion of air. When a turtle rapidly pulls its head and limbs into its shell, air is quickly forced out of its lungs, creating a hissing sound. This action compresses the lungs, expelling air through the glottis.
The larynx in turtles is central to sound production. It is composed of cartilages and supported by the hyoid bone. Two bands of elastic fibers within the larynx, located just upstream of the glottis, vibrate during exhalation. These structures are analogous to vocal cords, allowing for sound generation. Some tortoise species possess diverticula within the cricoid cartilage, which may function as resonating chambers to enhance low-frequency sounds. The interplay of air movement, laryngeal vibrations, and internal anatomical structures facilitates their diverse acoustic repertoire.