Animals Wildlife 11 Fascinating Facts About Monkeys By Catie Leary Catie Leary Writer and Photographer Georgia State University Catie Leary writes and curates visual stories about science, animals, the arts, travel, and the natural world. Learn about our editorial process Updated May 26, 2022 Juvenile geladas. Anup Shah / Getty Images Share Twitter Pinterest Email Animals Wildlife Pets Animal Rights Endangered Species Monkeys are primates found primarily in tropical rainforests. Most are arboreal, though some, like macaques and baboons, are terrestrial. New World monkeys, like spider monkeys, tamarins, and capuchins, are found in Mexico and South and Central America, while Old World monkeys, including baboons, gelada, and colobus, are found in Asia and Africa. Many species of monkeys are endangered. From strong prehensile tails to highly intelligent use of tools, discover the most fascinating facts about monkeys. Fast Facts Common Name: MonkeysScientific Names: Cercopithecidae, Callitrichidae, Cebidae, Aotidae, Pitheciidae, and AtelidaeAverage Lifespans in the Wild: Colobine monkeys: 20 years; patas monkey: 21 years; rhesus monkey: 30 years; hamadryas baboon: 37 yearsAverage Lifespans in Captivity: Colobine monkeys: 29 years; patas monkey: 21 years; rhesus monkey: 36 years; hamadryas baboon: 28 yearsIUCN Red List Status: 40 critically endangered, 72 endangered, 78 vulnerable, 34 near-threatened, 100 of least concernCurrent Population: Japanese macaque: 2,000 to 3,850; Lowe's monkey: 10,000; grey-shanked Douc langur: 550 to 700 1. Not All Primates Are Monkeys The term "monkey" is sometimes used as a catch-all for every animal in the primate family, but the truth is that monkeys live on completely different branches of the evolutionary tree from both apes (i.e., chimpanzees, gorillas, and humans) and prosimians (i.e., lemurs, tarsiers, and lorises). One big difference between monkeys and other primates is in the tail: Most monkeys have tails, while apes and other primates do not. Apes also tend to be larger than monkeys and, thanks to their larger brains, more intelligent. 2. They Use Grooming to Strengthen Relationships James Warwick / Getty Images For monkeys, picking bugs, dirt, and other debris off their companions is far from an indictment of their personal hygiene—it's an expression of affection and love. Grooming rituals not only keep monkeys healthy, they also strengthen their social bonds and, ultimately, make them feel more comfortable. Researchers have discovered that when vervet monkeys comb each other’s pelts, it fluffs the fur and makes it thicker. After a thorough grooming, the insulation value of the vervet monkey’s pelt increases by as much as 50%. 3. Only New World Monkeys Have Prehensile Tails Only New World monkeys in the Atelidae family, like howler monkeys and spider monkeys, and capuchins in the Cebidae family, have prehensile tails. These arboreal primates live in the tropical regions of Mexico, Central America, and South America. Old World monkeys, which live in Asia and Africa, have tails, but they are not prehensile. In length and gripping ability, spider monkeys and howler monkeys have an edge on capuchins. Spider monkeys have tails that are longer than their entire bodies. Their tails are also hairless and have friction pads for better gripping. Capuchins, which have hair-covered tails that are not nearly as long, primarily use their tails to grasp branches and carry fruit through the forest. 4. There's Only One Species of Wild Monkey in Europe Laura BC / Getty Images Barbary macaques have the distinction of being the only wild nonhuman primates in Europe. While most Barbary macaques inhabit the mountains of Morocco and Algeria, a small population of around 200 individuals was introduced and is maintained in Gibraltar. DNA analysis shows that these macaques, which have been in Gibraltar for many centuries, were originally imported from Northern Africa. Considered endangered in all parts of their range, the population of Barbary macaques has declined more than 50 percent over a period of 24 years. 5. Pygmy Marmosets Are the World's Smallest Monkeys Brian Guzzetti / Design Pics / Getty Images Native to the Amazon Basin of South America, this tiny New World monkey is around five inches long and weighs about four ounces at adulthood. Pygmy marmosets (Callithrix pygmaea) live in groups of two to six individuals and monogamous pairs share parental duties. Females give birth to one to three babies, which frequently include fraternal twins. Although the pygmy marmoset is the tiniest monkey, the award for the smallest living primate goes to the Madame Berthe's mouse lemur. 6. Mandrills Are the World's Largest Monkeys Anup Shah / Getty Images Mandrills (Mandrillus sphinx), which live in the tropical rainforests of central west Africa, are easily recognizable because of the vibrant coloration of their faces and behinds. In addition to color, mandrills exhibit extreme sexual dimorphism in size that sets them apart from other monkeys. While female mandrills weigh in at around 25 pounds on average, adult male mandrills weigh an average of 55 pounds and as much as 119 pounds. 7. The Color of a Bald Uakari's Face May Reveal Its Health Steve Cukrov / Shutterstock Bald uakari have striking red faces. Scientists have found anecdotal evidence suggesting that the brighter the face, the healthier these New World monkeys are. Individuals that are ill—often with malaria, which is prevalent in their rainforest habitat—exhibit a paler skin tone. These monkeys also have excellent color vision, which helps them determine which individuals are healthiest and best-suited for mating. 8. Capuchins Are Smart With Tools Dorit Bar-Zakay / Getty Images Capuchins were one of the first primates other than apes to be observed engaging in highly skilled tool use in the wild. According to an archaeological study of capuchin stone tool use, wild bearded capuchins have been using tools for more than 3,000 years. During that time, their tool usage evolved—a skill previously only attributed to humans. The most common example of intelligent tool use in capuchins is the way they crack open nuts, which is by placing them on pitted stone "anvils" and then hitting them hard with another rock. According to the archaeological study, they adjusted the size of their tools—using smaller rocks for seeds and softer nuts—over time. Another remarkable example of the intelligence of capuchins is the way they rub crushed up millipedes on their bodies to repel mosquitos and other insects. 19. Howler Monkeys Are the Loudest Martin Schneiter / EyeEm / Getty Images While all monkeys can make their presence known, howler monkeys have one of the loudest calls of any land mammal. Humans can hear a howler monkey’s roar from a distance of three miles. Male howler monkeys are larger and louder than females. The deep sound produced by the howler monkey is the result of a physical adaptation of the species: an enlarged hyoid bone in their throats. 10. Japanese Macaques Enjoy a Relaxing Hot Soak Mint Images / Getty Images Japanese macaques, also known as snow monkeys, have evolved to thrive in climates ranging from subtropical to subarctic. Troops of snow monkeys frequent the volcanic hot springs (onsens) at Jigokudani Monkey Park in Yamanouchi, Japan. This behavior appears to be an adaptation to the frigid climate, but researchers have also discovered that the hot baths reduce stress in the monkeys. 11. Many Monkeys Are at Risk Some of the most fascinating monkey species are experiencing rapid declines in population due to a variety of factors based on their unique location. The greatest risk factors include habitat loss and fragmentation, live capture for the global pet trade, and hunting for bushmeat or traditional medicines. Several are included on the IUCN's list of the 25 most endangered primates. Some of the most critically endangered Old World monkeys include the roloway monkey, the Niger Delta red colobus, and the Cat Ba langur; only about 30 individuals of the latter remain. New World monkeys that are critically endangered include the cotton-headed tamarin, the Ecuadorian white-fronted capuchin, and the pied tamarin. Save the Monkeys Donate or volunteer with the Pan African Sanctuary Alliance to help support Africa’s endangered primates. Make a contribution to the Endangered Primate Rescue Center to support their conservation and rescue and release programs for endangered langurs in Vietnam. Support the Rainforest Trust project to save the forest Niger Delta red colobus from extinction. Frequently Asked Questions How many species of monkey are there? The IUCN lists 336 total species between the six families of Old World and New World monkeys: Cercopithecidae, Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. How smart are monkeys? Monkey intelligence has been compared to that of a human toddler, at least when it comes to solving puzzles. Some have even outperformed adult humans in cognitive tests. Capuchins are known to be the smartest of all New World monkey species. What's the difference between a monkey and an ape? Apes are often called monkeys, but the two are vastly different. For starters, most monkeys have tails. Apes are larger, broader-chested, and longer-lived. Because they're larger, they also have bigger and more developed brains. Monkeys are intelligent, yes, but known to be generally more primitive than apes. Which is the rarest monkey? The Hainan gibbon is believed to be the rarest monkey in the world. It lives only on the tropical island of Hainan, off southern China, and when it was last assessed by the IUCN in 2015, only 10 to 25 mature individuals remained. Where are monkeys found? Monkeys inhabit tropical rainforests in Asia and Central and South America. They inhabit both rainforests and savannas in Africa. View Article Sources "Atelidae." IUCN Red List. Accessed on 25 May 2022. "Callitrichidae." IUCN Red List. Accessed on 25 May 2022. "Aotidae." IUCN Red List. Accessed on 25 May 2022. "Cebidae." IUCN Red List. Accessed on 25 May 2022. "Pitheciidae." IUCN Red List. Accessed on 25 May 2022. "Cercopithecidae." IUCN Red List. 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