Howler Monkey caught in the act, Pantanal, Brazil

Howlers are New World monkeys found in tropical Central and South America. They are aptly named for their cacophonous cries. When a number of howlers let loose their lungs in concert, often at dawn or dusk, the din can be heard up to three miles away. Male monkeys have large throats and specialized, shell-like vocal chambers that help to turn up the volume on their distinctive call. The noise sends a clear message to other monkeys: This territory is already occupied by a troop. These large and slow-moving monkeys are the only folivores of the New World monkeys. Howlers eat mainly top canopy leaves, together with fruit, buds, flowers, and nuts. They need to be careful not to eat too many leaves of certain species in one sitting, as some contain toxins that can poison them. Howler monkeys are also known to occasionally raid birds’ nests and chicken coops and consume the eggs.

Howler monkeys generally move quadrupedally on the tops of branches, usually grasping a branch with at least two hands or one hand and the tail at all times. Their strong prehensile tails are able to support their entire body weight. Fully grown adult howler monkeys do not often rely on their tails for full-body support, whereas juveniles do so more frequently. Howler monkeys have beards and long, thick hair which may be black, brown, or red. The red howler species is the most common, but it is often targeted by hunters eager for bushmeat. Other species of howler monkey may be critically endangered over sections of their ranges.