Monkeys are primates found primarily in tropical rainforests. Most monkeys 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 ᴇɴᴅᴀɴɢᴇʀed.
There are nearly 200 species of these clever primates. From strong prehensile tails to highly intelligent use of tools, discover the most fascinating facts about monkeys.
1. 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.
2. 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, gorɪʟʟas, 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.
3. Mandrɪʟʟs Are the World’s Largest Monkeys
Mandrɪʟʟs (Mandrɪʟʟus 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, mandrɪʟʟs exhibit extreme sexual dimorphism in size that sets them apart from other monkeys. While female mandrɪʟʟs weigh in at around 25 pounds on average, adult male mandrɪʟʟs weigh an average of 55 pounds, and as much as 119 pounds.
4. Howler Monkeys Are the Loudest
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.
5. They Use Grooming To Strengthen Relationships
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.
Researchers discovered another benefit of grooming. When vervet monkeys comb each other’s pelt, 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 percent.
6. Pygmy Marmosets Are the World’s Smallest Monkeys
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.
7. Many Monkeys Are at Ʀɪsᴋ
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 ʀɪsᴋ factors include habitat loss and fragmentation, live capture for the global pet trade, and ʜᴜɴᴛing for bushmeat or traditional medicines.
Many of the world’s monkeys are at ʀɪsᴋ. Several are included on the IUCN’s list of the 25 most ᴇɴᴅᴀɴɢᴇʀed primates. Some of the most critically ᴇɴᴅᴀɴɢᴇʀed Old World monkeys include the roloway monkey, the Niger Delta red colobus, and Cat Ba langur; only 50 individuals of the latter remain. 234 New World monkeys that are critically ᴇɴᴅᴀɴɢᴇʀed include the cotton-headed tamarin, the Ecuadorian white-fronted capuchin, and the pied tamarin.
8. There’s Only One Species of Wild Monkey in Europe
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.10
Considered ᴇɴᴅᴀɴɢᴇʀed in all parts of their range, the population of Barbary macaques has declined more than 50 percent over a period of 24 years.
9. Capuchins Are Smart With Tools
Capuchins were one of the first primates other than apes to be observed engaging in highly skɪʟʟed tool use in the wild. According to an archaeological study of capuchin stone tool use, wild bearded capuchins have been using tools for over 3,000 years. During that time, their tool usage evolved — a skɪʟʟ previously only attributed to humans.
The most common example of intelligent tool use in capuchins is the way they crack open nuts — 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 mɪʟʟipedes on their bodies to repel mosquitos and other insects.
10. The Color of a Bald Uakari’s Face May Reveal Its Health
Bald uakari have striking red faces. Scientists have found anecdotal evidence that suggests that the brighter the face, the healthier these New World monkeys are. Individuals that are ɪʟʟ — often with ᴍᴀʟᴀʀɪᴀ, 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.
11. Japanese Macaques Enjoy a Relaxing Hot Soak
Japanese macaques, also known as snow monkeys, have evolved to thrive in climates ranging from subtropical to sub-Arctic.
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.