The Howler Monkey lives in troops that can vary from five to thirty members, with about a quarter being males, half being adult females, and the rest being juveniles or infants.
This monkey is distinguished by its large head and the long, silky beard of adult males. Its body is heavy and compact, with a length that can reach 60 to 62 cm, and it weighs between 15 and 25 pounds. Its coloration ranges from shiny black to reddish-brown. They are easily recognizable by their loud howls, which are caused by the structure of their hyoid bone, acting as a resonance chamber.
On cold nights, troops group together to keep warm, and at dawn, when the sun heats up, they separate and begin foraging. Their habitat ranges from southern Paraguay to northern Guatemala. In Costa Rica, they are found from sea level up to 1600 meters in elevation.
These monkeys inhabit virgin or secondary growth forests, spending their entire lives in the treetops. Each troop occupies a defined area that can range from 500 to 4000 meters in diameter, depending on the availability of food resources. Their diet mainly consists of leaves, tender branches, flowers, and fruits from various trees such as ojoche, nÃspero, mountain almond, and hog plum.
Their predators include some felines and humans, who in some areas hunt them for food. Deforestation represents a significant threat to their natural habitat and is contributing to their potential extinction.