The loudest monkeys there are
The Mantled Howler Monkey (mono congo; Alouatta palliata). These large monkeys are often heard before being seen. The loud vocalizations of male howler monkeys can carry for over 1km even in dense rainforests. They howl (or roar or grunt), especially at dawn and dusk, and at other times in response to intruders. Air is passed through a specialized, hollow and much enlarged hyoid bone in the throat, producing the strange and resonant call. The hyoid bone contributes to the typically thick necked appearance of the males.
Howlers live in small groups of about a dozen individuals, and the male calls keep the groups spaced out so they don't compete for food, consisting mainly of leaves, supplemented by fruits and flowers. Howler Monkeys travel less than other monkeys, preferring instead to maintain separated home ranges of about 10 hectares per group. Therefore howlers have survived better than other species in the face of fragmentation of the forest.
Mantled Howler Monkeys are stocky, with wide shoulders, large heads and necks (especially in the males), and relatively small hind parts. Their prehensile tail is often carried coiled. They are black with the exception of their sides and back, where long hairs can give them a golden brown or buff colored mantle. They weigh 5 to 8kg and are 1 to 1.25m in length, of which just over half is tail. They browse and rest in the canopy making it hard to spot them from the ground. Good places to see them are hilly forest where you look out over the treetops.
Pictures by Angela and Jörn Malek. The team of Discovery Travel World wishes you the best of times in our little paradise called Costa Rica.
Text by Lonely Planet.