If you come upon a troop of black howler monkeys in a zoo or in the wild, you might think you are looking at two different species. But don’t be fooled! The males and females are sexually dimorphic, meaning they have different physical characteristics. While adult males are indeed black, adult females and juveniles are a golden tan color.

Speaking Volumes

The black howler monkey is the loudest land animal in the world. Black howler monkeys have special adaptations that enable them to produce calls that can reach 140 decibels. (A jet engine at takeoff is about 150 decibels—loud enough to rupture eardrums.) Their hyoid bones, located in their throats, are modified and form a bony box called a corniculum. The corniculum is an egg-shaped pouch that acts as a resonator, amplifying their calls, which define territory in their dense jungle habitat. “If you can hear me, you’re too close!” The males do most of the calling in the morning when the troop wakes. The males call in a chorus and neighboring males answer. Howlers don’t have exclusive territories, but share home ranges, so the calls help to claim feeding sites and define boundaries. Stronger troops can defend an area with the male chorus and calls and weaker troops will avoid those areas.


Howler monkeys are found in the forests of central South America.


These herbivorous monkeys eat figs, plums, buds, flowers, nuts, and leaves.


  • Length: 24 inches
  • Weight: 15–30 pounds