Closeup of a white-headed langur holding onto a branch while it holds a green leaf in its mouth
Some Endangered


  • CLASS: Mammalia (Mammals)
  • ORDER: Primates
  • FAMILY: Callitrichidae (marmosets and tamarins); Cebidae (New World monkeys); Cercopithecidae (Old World monkeys)
  • GENERA: 37
  • SPECIES: 196


A barrel of monkeys: They’re magnificent, mischievous, and sometimes mysterious—monkeys! They have many different adaptations, depending on their habitat. Most are arboreal. Others, like macaques, baboons, and some mangabeys, are more terrestrial. All monkeys can use their hands and feet for holding on to branches, but some arboreal monkeys can use their tails, too. Tails that can grab and hold are called prehensile. These special tails are ridged on the underside and very flexible, so much so that they can grab a tree branch or pick up something as small as a peanut!

Monkeys are found in two main regions of the world, so scientists have grouped them as either Old World monkeys or New World monkeys. Old World monkeys are found in Africa and Asia. Some examples are guenons, mangabeys, macaques, baboons, and colobus monkeys. New World monkeys are found in Mexico, Central America, and South America. Some examples are woolly monkeys, spider monkeys, howler monkeys, capuchin monkeys, and squirrel monkeys. Marmosets and tamarins also live where New World monkeys are found but are different enough to be in their own different scientific grouping. 

There are a few characteristics that are different in Old World and New World monkeys:

Noses: Most Old World monkeys have small curved nostrils set close together. Most New World monkeys have round nostrils set far apart.

Cheek pouches: Macaques and some of the other Old World monkeys have cheek pouches, where food is stuffed on the run so it can be chewed later. New World monkeys don’t have cheek pouches.

Rump pads: Some Old World monkeys, such as drills, have sitting pads on their rumps, but New World monkeys do not.

Tails: Some New World monkeys, such as spider monkeys, have prehensile tails, but Old World monkeys do not. And one Old World monkey species, the Barbary macaque, has no tail at all!


Most monkey species live in the tropical rain forests of Asia, Africa, and Central and South America, or the savannas of Africa. Geladas and golden monkeys are mountain dwellers, and Japanese macaques live in parts of Japan where it snows; these are the monkeys you may have seen on TV that find hot springs and spend a lot of time in the winter sitting in the warm water—kind of like a macaque Jacuzzi! Baboons live in savannas, open wooded areas, and rocky hillsides; although they are able to climb trees, they spend most of their time on the ground.

Many monkey species are known for their tree-swinging leaps that put human acrobats to shame! Many monkey species use the “arm over arm” technique you may have seen children practicing on the “monkey bars” at the playground! Colobus monkeys, unlike other monkey species, have hind legs that are much longer than their forelimbs, making for incredible leaping ability with great speed. 

Monkey feet are as flexible as their hands, which also help them travel through small branches high up in the rain forest canopy. Monkeys play an important role in the wild by pollinating flowers and dispersing seeds as they travel. Some monkeys can swim; their webbed toes help them paddle through the water, and they may swim across a stream or river to avoid predators or get to food. 

Night or owl monkeys are strictly nocturnal, using their enormous eyes to see well in the dark. They communicate with one another through scents and calls, including a series of grunts that resonate in the forest.

Prehensile tails come in handy for holding on while the monkey collects food: flowers, fruits, nuts, leaves, seeds, insects, birds’ eggs, spiders, and small mammals. Old World monkeys fill up their large cheek pouches with fruits, leaves, and insects as they forage during the day, stopping to chew and swallow their food when they find a safe spot to rest. Baboons are also known to eat meat when they can catch it, including young antelope, rabbits, and birds like guinea fowl.

Leaves are the food of choice for some monkey species. Colobus monkeys and langurs have chambered stomachs that carry bacteria, which help ferment and digest leaves. Geladas prefer to graze on grass!

Monkeys at the San Diego Zoo and the San Diego Zoo Safari Park are offered a variety of vegetables, special herbivore biscuits, and a variety of leafy branches (mulberry, willow, hibiscus, and ficus) to munch on.


Groups of monkeys, called troops, travel together by day to find food. A troop can number from a few individuals to a thousand or more, depending on the species.

Within huge troops, the animals form smaller groups, called harems, which include an adult male, several adult females, and their offspring. Unattached adult males, called bachelors, may form their own group. To keep family bonds, monkeys engage in daily mutual grooming.

One exception to social living is the gray titi monkey, native to the tropical forests of Bolivia. These small monkeys, which only weigh about 2 pounds (0.9 kilograms), live in small, monogamous family units made up of the parents and their immature offspring.

Some monkey species give birth to babies that are a completely different color from the parents. For example, adult colobus have black hair, but a newborn is white; langur babies are orange while their parents are black. It’s thought this color distinction makes it easier for the whole troop to identify and look after the infants. The youngster’s color usually changes within the first six months, when the juvenile becomes an almost perfect copy of the adults.

Infants are helpless at birth, so they get rides by clinging to their mothers. But marmosets and tamarins are different—the fathers have almost all the responsibility! They carry the babies on their back and watch over them, only giving them to Mom for nursing. Another difference—they regularly have twin or triplet, not single, births. Is that because Dad helps out so much? 

When the troop is not traveling, monkey babies are very active, spending much of their waking hours playing. These fun activities help young monkeys develop physical and social skills they need for adult life.

Monkeys are very social animals, so it is important that they communicate well in order to get along in their large groups. They use vocalizations, facial expressions, and body movements to get their messages across. Staring, for instance, is a threat in monkey society. Monkeys look down or away to avoid threatening other monkeys, thus preventing fights. Species with long tails use them to communicate with others and indicate their mood. Loud vocalizations can mean, "stay out—this is my territory.” Using vocalizations instead of fighting is a much safer way to communicate. Monkeys use barks, screams, grunts, squeaks, hoots, wails, and moans to communicate with one another.

Grinning, or pulling the lip up to show the teeth, may seem like a smile to us. But for monkeys, this is a sign of aggression or anger, because biting is one of the ways monkeys fight and defend themselves. Other signs of aggression include head bobbing, yawning (again, to show the teeth), and jerking the head and shoulders forward. Cotton-topped tamarins raise and lower a crest of fluffy white hair on their head to emphasize their facial expressions.

Monkeys also express affection and make peace with others by grooming each other. Although grooming helps monkeys keep their fur clean of dirt, dead skin, and parasites, it also helps them build and maintain good social relationships. Grooming seems to be a way to make up after fighting or to make friends with other troop members.


Monkeys have been a part of San Diego Zoo Global since we were founded in 1916, and by 1925 we had 22 species represented. Since then, we have celebrated the births of many endangered monkey species, including golden lion tamarins, lion-tailed macaques, red-shanked douc langurs, gray langurs, and mandrills. Today, the Zoo is home to 27 monkey species, including colobus, swamp monkey, mangabey, mandrill, and guenon species in Lost Forest, langurs and macaques in Asian Passage, and spider monkeys in Discovery Outpost. You can view kikuyu colobus and Geoffroy’s marmosets at the San Diego Zoo Safari Park. Here are some fun facts about monkeys at the Zoo over the years:

A weeper capuchin named Irish was popular in the San Diego Zoo's earliest days. According to a 1946 article in our member magazine, ZOONOOZ, “Irish…has long been a favorite of regular zoo visitors. Since 1927 he has sung unmistakable greeting to his friends and, having once cultivated his acquaintance, no none can pass through the zoo without paying a visit to his cage.”

Irish sired several babies and was declared a “splendid father,” caring for his babies “with infinite tenderness and a patience seldom equaled in human parents.”

Francois’ langurs first came to the San Diego Zoo in 1980 from the Guanqzhou Zoo in China; we were the first zoo in the Western Hemisphere to house this species and established the population now found in American zoos. We also had the first birth of this species in the Western Hemisphere, in 1981, and one of the Zoo’s males, Baba, fathered 22 offspring.

Golden monkeys Min-Min and Rong-Rong lived at the Zoo for six months in 1984 to 1985 as part of an exchange program with a zoo in Chengdu, China. This was an important international zoological event, as it was the first time this species was seen in a Western zoo.

Lion-tailed macaques were the first primate species to be studied by our researchers, starting in 1979 and focusing on their reproductive biology. We knew very little about them and tried to find out how their social organization worked. One of the first things we learned was that we should not house adult males together; this was to avoid a lot of tension and injuries!

The Zoo has exhibits that house different monkey species together, or monkeys living with other animals that they would encounter in the wild. For example, there is a family of Wolf’s guenons with pygmy hippos; black mangabeys and Angolan colobus monkeys; mandrills and kikuyu colobus; and Allens’ swamp monkeys and Schmidt’s spot-nosed guenons sharing a habitat with forest buffalo, red river hogs, and African spot-necked otters!

In July 2011, we became the first zoo known to help raise a baby silvered leaf monkey, born on July 3 to a first-time mother that did not hold her properly for nursing. Our nursery keepers bottle-fed the baby several times a day while allowing her to stay with her family for several hours each day.

The fun factor in the Zoo's Lost Forest increased 15-fold with the arrival of tufted capuchin monkeys in 2011. These highly intelligent little primates are certainly keeping things lively! They came to us after participating in facial recognition and intelligence tests at Yerkes National Primate Research Center. Each monkey has his or her own distinct personality. Lulu, for example, is timid but can also be quite stubborn. Lance is very people oriented, and Ozzie is clearly the dominant male. Their entertaining "monkey business" keeps Zoo visitors swinging by for more!


Unless human behavior changes, monkeys face an uncertain future. Many live in areas where people live. Monkeys are often considered pests by farmers and are killed. Some are killed for their fur and for meat, which is known as bushmeat; some are hunted for medicinal concoctions. Monkeys are also trapped and sold as pets. People need to remember that monkeys are wild animals, and they do not make good pets. They are loud, messy, difficult to care for, and can be aggressive. Monkeys can also become very sick from not getting the right food, and they lead unhappy and short lives from not living in the right conditions.

Over the past decade, San Diego Zoo Global has been working with our colleagues in Southeast Asia, especially China, on activities collectively known as “The Asian Leaf-eating Monkey Program,” designed to address collateral conservation research, training, and education issues in areas harboring endangered leaf monkeys. To date, substantial progress has been made in all areas and we are continuing our efforts there. In 2011, we installed 40 remote camera traps to monitor habitat use and movement patterns of the last remaining population of Guizhou snub-nosed monkeys in China, estimated at about 750 individuals.

San Diego Zoo Global’s Central Africa Program runs three permanently manned field stations in the Ebo forest, in the heartland of biodiverse Cameroon, Africa. Nine species of day-living monkey species live in the Ebo forest, some of which (like the Preuss’s red colobus) are critically endangered. Many monkey species have been poorly studied, and researchers are only gradually uncovering their social, dietary, and behavioral habits. In Cameroon, hunting to supply the commercial trade in bushmeat destined for big Africa cities is one of the major threats to monkeys, and our research stations are providing a safe haven for many of these species simply because the presence of researchers in the forest deters hunters, and our community outreach efforts in local villages help get the conservation information to the people who live close to these species.

San Diego Zoo Global has also partnered with Nature and Culture International to preserve tropical forest habitat in Mexico and South America. Our scientists are also joining them in biological studies of the animals and plants in the Cazaderos region of Ecuador and in northwestern Peru. Our team has documented several mammal species there, including black howler monkeys, and we see tremendous potential to help save large areas of forest that otherwise might well be lost.

You can help protect monkeys and monkey habitat! Do not buy anything made from monkey body parts. Be careful about buying items made from rain forest trees, unless that wood is certified. Some rain forest products, such as Brazil nuts, actually help protect monkey habitat, because they can only be harvested from healthy rain forests. This type of product usually has a label describing how it helps protect the rain forest. Read the labels! Recycling and buying recycled products also helps save all animal habitats by reducing the amount of resources we take from the Earth.

Join us! You can help us bring monkey species back from the brink by supporting the San Diego Zoo Global Wildlife Conservancy. Together we can save and protect wildlife around the globe.



10 to 50 years, depending on species


Gestation: 4 to 8 months, depending on species

Number of young at birth: 1 or 2 for Old World and New World monkeys; 1 to 3 for marmosets and tamarins

Weight at birth: .5 to 31 ounces (14 to 900 grams), depending on species

Age of maturity: 18 months to 8 years, depending on species


Height: Largest - mandrill Mandrillus sphinx, up to 30 inches (76 centimeters); smallest - pygmy marmoset Cebuella pygmaea, 4.6 to 6 inches (12 to 15 centimeters)

Weight: Heaviest - mandrill, up to 119 pounds (54 kilograms); lightest - pygmy marmoset, 3 to 5 ounces (85 to 140 grams)


Howler monkeys are the loudest monkeys—their deep, howling calls can be heard almost 2 miles (3 kilometers) through the forest and more than 3 miles (5 kilometers) over open areas like lakes. The males call to announce their territory to other troops.

Vervet monkeys have different alarm calls to identify different predators, such as eagles, pythons, and leopards.


Burping is a friendly social gesture among leaf-eating colobus monkeys. Their chambered stomachs digest leaves by bacterial fermentation, which produces lots of gas.

Golden monkeys, with their long golden hair and turquoise blue faces, were depicted in Chinese art for centuries, although they were thought to be a fable until their discovery in 1869.

The Allen’s swamp monkey "goes fishing” by placing leaves or grass on top of the water and grabbing fish that come to hide underneath.


A monkey's face peering out from a tree.

Monkeys Matter

Throughout the world, nonhuman primate species are threatened with extinction, largely due to the actions (and inaction) of humans...