The noise sends a clear message to other monkeys: This territory is already occupied by a troop ... diet. Howler monkeys have beards and long, thick hair which may be black, brown, or red.

This is a computer generated 3-D model of a Bolivian red howler (Alouatta sara), with the hyoid bone in red. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases ...