Why the Guianan red howler monkey howls

July 12, 2014, 1 p.m.
howler monkeys

The reason for all that racket
Howler monkeys are known for their loud calls that can be heard over half a mile away. The Guianan red howler monkey has a specialized piece of anatomy to help it make such deep, resonating calls. A hyoid, a U-shaped bone located between the base of the tongue and the larynx, helps the monkey amplify its voice and generate a roar that can last as long as eight seconds. But why is such impressive noise part of the howler monkey’s daily routine? It isn’t to bring other monkeys closer, as one might suspect. It’s to keep them away. A troop of red howler monkeys will vocalize starting as early as two hours before dawn, to warn off any strange monkeys from approaching their turf. If the home range of two troops overlap, the groups won’t necessarily give chase but will instead yell at each other in a big roar-fest. Roaring is not only used to keep strangers away, but it is also thought that females will howl within their group to rile up competing males. Howler monkeys give a whole new meaning to the phrase, “Use your words.”

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Jaymi Heimbuch is a writer and photographer at Mother Nature Network. Follow her on Google+, and Facebook.