Howler monkeys are New World monkeys that are found in tropical Central and South America. They are named for their cacophonous calls. When a group of howlers let loose in concert, they can be heard up to three miles away. These calls are used to send a clear message to other monkeys that the territory is already occupied. They are also the largest of the New World monkeys. Howler monkeys have an average lifespan of 15 to 20 years in the wild.