The black howler monkey is found in eastern Bolivia, southern Brazil,
Paraguay, and northern  Argentina. The body length of a black howler monkey is 22 to 36 inches, and the tail is 23 to 36 inches long. An adult male Black Howler Monkey is black, while his wife and children are straw colored. Females gice birth every one to two years. Howlers mostly eat leaves, fruit, and other vegetable matter. They can live for weeks at a time eating only leaves because of a special adaptation of their gut which lets them utilize leaf fiber for energy. Howlers have a special egg-shaped hyoid bone which allows them to produce the loudest call of any primate, which can be heard three miles away. Black howler monkeys are hunted for food. They lose their habitats due to the planting of crops and raising of livestock, which is the main reason of their decline.