Qele Qele

Chimps have been known to kill and devour infant chimps from rival groups even when other foods are plentiful. While the cause of cannibalism among the chimps remains unknown, their kind has gained a grim reputation for brutal acts of predation. In some parts of their range, hunting parties of adult male chimps stalk and kill the smaller monkeys who share their forest home. Herded into an ambush by the hunters, the monkeys flee for their lives.

They roar simply to keep intruders out of their territories.
Howlers are vegetarians, but most other monkeys will eat anything they can find A saddle-backed tamarin searches for insects.

And a tufted capuchin gnaws on a shoot while watching for something bigger. The pigmy marmaset, the world smallest monkey is only five inches long, and to it
a grasshopper is a feast. The tiny monkey supplements its diet of leaves, plant gums and fruit with any insects it is able to catch.