Howler monkeys (Alouatta) are a primate genus from the family of bracketed monkey (Atelidae). They live in Central and South America and are known for their loud shouting, which they mostly emit in the early morning. They feed on leaves and other plant material.
Howler monkeys take their name from the loud roaring of animals that both sexes emit and that can be heard over several kilometers. The roar is primarily used for communication between different groups. All of the males in the group join in. Together with the roar of answers from other animals, there is a loud spectacle. Howler monkeys make their presence clear to warn other groups of their core area. Energy-consuming fights - since the howler monkeys are leaf eaters, they have to keep up with the energy - can thus be avoided. A second reason for the roar may be that individual animals are joining a group - the migration among the groups is relatively high - and by shouting they are signaling their presence and thus receiving an answer as to whether they are welcome or not. Mostly the roar sounds in the morning, if necessary also at other times of the day. (Wikipedia)
