The answer to what mammal has no vocal chords is not as simple as “rabbits” or “giraffes.” While the world’s tallest animals may not make sound from their mouths, giraffes can still communicate with one another and their young using a range of unique sounds.
The secret to giraffe vocalizations lies in their larynx, which is located at the top of the throat. The larynx is like a voice box, and it protects the airways that pass through to the lungs. The structure is formed by cartilage and features folds of tissue that vibrate when air passes through them. These vocal cords are what enable humans to talk, pigs to grunt, and lions to roar.
Sloths, on the other hand, have an elongated larynx that produces low-frequency hisses. This unique anatomy allows them to produce low-pitched calls that travel farther in the dense forests where they live. This enables them to communicate over long distances and conserve energy.
While most mammals use a diaphragm muscle to breathe, sloths are the only species that use thoracic breathing. This method results in slower airflow through the larynx, contributing to their low-frequency calls. Additionally, their lungs are smaller than those of most other mammals, and they take fewer breaths per minute to conserve energy. The result is a distinct, low-pitched, and distinctively hissing call that scientists have been able to record. This is how a hissing snake lets its family know that it is around.