The howler monkey is famous for a loud, echoing call that can be heard several kilometres away.
Howler monkeys produce their booming calls with an enlarged hyoid bone and a resonating throat structure. These anatomical features amplify sound without requiring the animal to expend as much energy as a long-distance physical confrontation would require.
Groups commonly call at dawn or dusk, helping neighbouring troops communicate across forest canopies. The calls can signal territory and group location, and several individuals may join in a chorus.
Howler monkeys live in Central and South America and are among the largest New World monkeys. Their diet consists mainly of leaves, fruit and flowers. They are sometimes confused with gibbons, whose calls are also loud, but gibbons are apes from Asia, whereas howler monkeys are American monkeys.