Red howler monkey (Alouatta seniculus)
Range: Western Amazon Basin of Venezuela, Colombia, Ecuador, Peru, Bolivia, and Brazil
After hearing the howler monkey’s roar, no one would question that this primate was appropriately named. The monkey’s earth-shaking calls, which can be heard miles away, are used by monkey troops to make their presence known and avoid confrontations with other troops, usually over food. Howler monkeys are among the largest of the New World monkeys, with nine species currently recognized. They can be seen high in the forest canopy using their long, prehensile tails to grab branches and living in groups of up to nine individuals. These groups contain only one or two males, which each have several female mates.

Researchers have found that red howler monkey populations decline during El Niño events, which affect food availability. The intensification of El Niño events due to climate change puts the red howler monkey in further peril.