Howler Monkey , certain monkeys found in Central and South America, known for their characteristic roar, which can be heard at least 3 km (at least 2 mi) away. The hyoid bone-that is, the bone supporting the tongue-is enlarged and hollow and opens into a greatly dilated voice box; together they provide two huge resonating chambers for the production of sound. The howler is the largest and heaviest of the American monkeys, reaching a length of 56 to 92 cm (22 to 36 in), excluding the long, prehensile tail, and a body weight of 4 to 10 kg (9 to 22 lb). The black face is bearded with long black hair in the adult; the lower jaw is wide, and the neck is swollen. The body and tail are covered with thick fur except for the underside of the last third of the tail, which is bare and rough for obtaining firm support when the animal swings from limb to limb. The best-known species, the red howler, is metallic red and has a black face, feet, and hands. Howlers live in trees in groups of 2 to 45 individuals. They feed mainly on leaves and fruit but will also eat insects, seeds, and flower parts .