Monkeys are omnivorous, eating nuts, fruit, leaves, flowers, bark, roots, seeds, rodents, birds and invertebrates—pretty much whatever is available in their habitats. They use all four limbs when moving on the ground (quadrupedal movement), although they can also stand upright for short periods on their hind legs (bipedal). Many species have prehensile tails, which they use to grasp objects, hold branches and vines, and to support themselves while sitting, such as during birthing. Monkeys have opposable thumbs, which enhance their manual dexterity.
They often have a long, thick fur that helps them survive harsh environments such as desert-like savannas or snowy mountains. Some monkeys are so good at adapting to their harsh environments that researchers have dubbed them “mavericks.” For instance, Japanese macaques—sometimes called snow monkeys—have evolved to survive the cold of northern Japan by bathing in hot springs. This behavior spread among the troops after a female macaque named Mukubili began wading in the hot springs in 1963 to retrieve some soybeans thrown in by researchers.
In the wild, monkeys are solitary or live in groups known as troops. The size of the troop depends on the species: a single male rules a group of females with young, as is the case in hamadryas baboons, mandrills and most guenons; other troops have several competing males, such as savannah baboons and some langurs.
Because of their close association with humans, many monkeys are at risk. They are hunted for bushmeat or used in the lucrative pet trade, and many wild monkeys have been driven out of their native habitats due to agriculture and urban development. They are also captured for use as research animals and even for space missions.