Monkeys always live in groups that have a distinct hierarchy, and it is the responsibility of the leaders of these groups to organize the other monkeys to defend against predators. When fighting with each other, monkeys may bite or scratch.
When threatened by ground-based predators such as hyenas and jackals, adult monkeys gather together to bark, bare their teeth and possibly throw sticks or other debris in an attempt to scare them off. If this does not work, the monkeys may attack the predator as a group. Some monkeys, such as capuchins, can use sticks as clubs. Monkeys that live in trees have little defense against airborne predators such as eagles and simply attempt to hide from and avoid them.
Some types of male monkeys may fight among themselves for dominance in the hierarchy and to display their abilities to females. They may exhibit any of the techniques they use against predators when fighting amongst themselves. Monkeys have also sometimes been used in fights against other types of animals, a practice known as monkey-baiting. Records of some of these fights indicate that an adult male monkey was consistently able to defeat dogs by leaping onto their backs and clawing and biting at their windpipes.