The Yucatán black howler, or Guatemalan black howler, (Alouatta pigra) is a species of howler monkey, a type of New World monkey, from Central America. It is found in Belize, Guatemala and Mexico, in and near the Yucatán Peninsula. It lives in evergreen, semideciduous and lowland rain forests. It is also known as the baboon in Belize, although it is not closely related to the baboons in Africa.
The Yucatán black howler is the largest of the howler monkey species and one of the largest of the New World monkeys. Yucatán black howler males are larger than those of any other Central American monkey species. Adults of both sexes have long, black hair and a prehensile tail, while infants have brown fur. Males over four months old have white scrotums.
The Yucatán black howler shares several adaptations with other species of howler monkey that allow it to pursue a folivorous diet. Its molars have high shearing crests, to help it eat the leaves. The male of the species has an enlarged hyoid bone near the vocal cords. This hyoid bone amplifies the male howler's calls, allowing it to locate other males without expending much energy, which is important, since leaves are a lowenergy food. Howling occurs primarily at dawn and at dusk.
The Yucatán black howler is diurnal and arboreal. It lives in groups of generally one or two adult males. Groups generally have between two and 10 members. The home range is between 3 and 25 hectares. Population density can exceed 250 monkeys per square kilometer in the Community Baboon Sanctuary in Belize.
The Yucatán black howler's diet includes mostly leaves and fruit. Flowers also make up a small part of the diet. The breadnut tree can provide as much as 86% of the monkey's diet during some seasons.
Females reach sexual maturity at four, and males reach sexual maturity between six and eight years old. Males leave their natal group upon reaching sexual maturity, but females generally remain with their natal group. They can live up to 20 years.