Black howler monkeys are the largest of the New World primates. Female howlers weigh about 14 pounds, and males can weigh up to 25 pounds. These arboreal animals are sexually dimorphic: females are born and remain yellow-brown; males are born brown but turn black at maturity. Unique in appearance, howlers have an enlarged hyoid bone and a greatly enlarged lower jaw, enabling them to create vocalizations loud enough to be heard up to three kilometers through the jungle. They also have a prehensile tail strong enough to hold their entire body weight. Black howler monkeys have a variable diet, mainly eating leaves, fruits and other vegetable matter. They live in troops comprised of one male with many females.