Golden monkey of China © Giles Badger

Did you watch the premiere of Clever Monkeys last night? Share your comments and favorite moments with other NATURE fans using the comment form below.

Do you have a favorite monkey from the show?

Surprised by something you learned?

Clever Monkeys premiered Sunday, November 9 at 8pm (check local listings).

Don’t miss another new episode of NATURE, American Eagle, coming this weekend — Sunday, November 16.

NATURE travels around the world to visit some of these fascinating primates. From tiny pygmy marmoset in South America to aggressive baboons of Africa and compassionate toque macaques in Sri Lanka, Clever Monkeys challenges many ideas about what is purely “human.”

Clever Monkeys premieres Sunday, November 9 at 8pm on PBS (check local listings).

To order a copy of Clever Monkeys, please visit the NATURE Shop.

White-faced capuchins in a tree. Image © BBC

Monkeys are clever, but we think that NATURE viewers are even more clever! Think you can come up with a funny caption for what’s going on in this photo?

Guereza Colobus (Colobus guereza)

• Type: Mammal
• Family: Cercopithecidae
• Habitat: Deciduous and evergreen forests
• Location: Across central Africa
• Diet: Leaves and fruit
• Average lifespan in the wild: 20 years
• Size: Head and body 20.5-27.5 in (52.1-69.9 cm); tail 20.5-39.4 in (52.1-100 cm) 
• Weight: 17.2-20.3 lbs (7.8-9.2 kg) for females; 20.5-29.8 lbs (9.3-13.5 kg) for males

Also known as the eastern black-and-white colobus, or the white-mantled colobus, guereza monkeys have a glossy black coat with beautiful white markings. A mantle of long white hairs adorns their back in a U-shape from their shoulders to the base of their tail. Guerezas have a hairless gray face that is also surrounded by white. Their long tail can be either white or yellowish in color, with a large tuft of white fur at the end. This distinctly marked tail is as long as their head and body combined.

Guerezas have a specialized stomach with two different regions, similar to a cow’s stomach, which helps them digest plant cell walls and fibers from their leafy diet. The upper region of the stomach also contains strains of anaerobic bacteria that aid in digestion. This complex stomach allows guerezas and other colobus monkey species to feed on large quantities of leaves. They also eat fruit. Guerezas live in various habitats across equatorial Africa and as a result their diet can be diverse. Their tough stomachs allow them to digest this variety of food.

Guerezas live in small cohesive groups of 8 to 15 individuals. They spend half their day traveling and feeding. Individual guerezas take turns leading the group to different feeding sites, using quadrupedal motion to travel through the trees. Their hands and feet are adapted especially well for this kind of motion through the forest, grasping and walking on tree limbs. Guerezas also run through tree tops, bounding up and galloping across branches, though they usually make only short leaps across horizontal distances.

Guerezas spend the other half of their day at rest. Between feedings, the group takes breaks to relax and groom each other, and after traveling and feeding during the day, a guereza group will congregate each night before sunset in several adjacent sleeping trees. Most groups consist of one male, several adult females, adolescents, and young. Guereza groups often live close to each other or in overlapping territories, though each group is very territorial. At dawn and dusk, males will “roar” as a way of signaling their territory to other groups.

Did you know: The guereza’s genus name colobus comes from the Greek kolobos, meaning “curtailed” or “mutilated,” appropriate because the animal has only four digits on each hand. Its lack of a thumb may be an adaptation to allow for rapid movement through trees.

Photo by Yoky, Creative Commons license.

On the Web:

Primate Info Net
http://pin.primate.wisc.edu/
Primate Info Net is a comprehensive Web resource including primate news and species factsheets.

The Callicam
http://pin.primate.wisc.edu/callicam/
Check out this live common marmosets webcam!

Institute for Ethnobotany and Zoopharmacognosy
http://www.ethnobotany.nl/institute.htm
This Web site offers recent updates in the field of zoopharmacognosy.

IUCN/SCC Primate Specialist Group
http://www.primate-sg.org/index.htm
This group of concerned primatologists is working with the World Conservation Union (IUCN) and the Species Survival Commission (SSC) to help save primates species from extinction.

Duke Lemur Center
http://lemur.duke.edu/
The Duke Lemur Center aims to promote research and understanding of prosimians.

International Primate Protection League
http://www.ippl.org/
The IPPL is a grassroots nonprofit organization dedicated to protecting the world’s remaining primates, great and small.

Primate Conservation, Inc.
http://www.primate.org/
Primate Conservation, Inc. is an all volunteer not for profit foundation dedicated to studying, preserving, and maintaining the habitats of the world’s least known and most endangered primates. 

Endangered Primate Rescue Center
http://www.primatecenter.org/
The Endangered Primate Rescue Center is dedicated to the rescue, rehabilitation, breeding, research and conservation of the endangered primates of Vietnam.

The Wild Animal Rescue and Education Center
http://www.wared.gibbonproject.org/index.htm
Learn about the endangered primates that call this animal sanctuary in Thailand home.

In Print:

Arnold, K; Y Pohlner; and K Zuberbühler. “A forest monkey’s alarm call series to predator models”. Behavioral Ecology and Sociobiology, 62:549-559. 2008.

De Waal, Franz. Our Inner Ape: A Leading Primatologist Explains Why We Are Who We Are. Riverhead Trade, 2006.

De Waal, Franz (ed.) Tree of Origin: What Primate Behavior Can Tell Us About Human Social Evolution. Harvard University Press, 2002.

Engel, Cindy. Wild Health: Lessons in Natural Wellness from the Animal Kingdom. Houghton Mifflin, 2003.

Hurford, James. The Origins of Meaning (Language in the Light of Evolution). Oxford University Press, 2007.

McGraw, William Scott and Klaus  Zuberbühler. Monkeys of the Tai Forest: An African Primate Community. Cambridge: Cambridge University Press, 2007.

Pereira, Michael E. (ed.), Fairbanks, Lynn A. Juvenile Primates: Life History, Development and Behavior. University of Chicago Press, 2002.

Sapolsky, Robert M. A Primate’s Memoir: A Neuroscientist’s Unconventional Life Among the Baboons. Scribner, 2002.

Zuberbühler, K and K Arnold. “Meaningful call combinations in a non-human primate”. Current Biology, 18(5):R202-R203. 2008.

Pygmy Marmoset (Callithrix pygmaea)

• Type: Mammal
• Family: Cebidae
• Habitat: Tropical rainforest, preferably seasonally flooded riverine forests
• Location: Western Amazonia; Columbia, Ecuador, Brazil, Peru, and Bolivia
• Diet: Tree sap, gums, insects, and fruits
• Average lifespan in the wild: 12 years
• Size: Head and body 4.7-6 in (12-15.2 cm); tail 6.8-9 in (17.2-22.9 cm)
• Weight: 4.20 oz (119 g)

Even though they are the smallest of all the monkeys, pygmy marmosets can leap more than 16 feet. At only 5.35 inches and 4.2 ounces on average, they expertly maneuver through the canopy, scampering vertically up trees using their sharp claw-like fingernails. All other primates have flat fingernails, but pygmy marmosets’ specialized claws are much better for gripping limbs while feeding on tree sap. The diet of pygmy marmosets is largely comprised of tree exudates – the sap, gum, resin or latex that oozes out of plants. The incisors, which are narrow and elongated, help these tiny animals gnaw holes in tree trunks to release sap. Insects and fruit supplement their diet.

Pygmy marmosets live in social groups of two to nine individuals. The dominant female is the only female in the group to mate. Every member in the group aids in the care of offspring. For the first two weeks of their lives, babies are always carried. After that time, they are left in a hole or hidden tangle of vines while the adults forage for food. As the offspring grow, they spend a great deal of their time playing in the trees. When they reach adulthood, they either remain in their natal group as a non-breeding subordinate or venture out to join a new group.

Pygmy marmosets have a v-shaped lower jawbone, and thus a pointed face. Their tales are very long compared to their bodies, measuring about eight inches and banded with faint black and tan rings. The length of their head and body combined is always shorter than the length of their tail. Their fur is a brownish yellow, and dense tufts of hair sweep back from the forehead.

Did you know: Pygmy marmosets give birth to fraternal twins at an unusually high rate — while most primates give birth to only one offspring at a time, up to 70 percent of pygmy marmosets’ births are to fraternal twins.

Photo by Malene Thyssen

Diana monkeys are some of the most clever monkeys when it comes to language.

We all know the expression monkey see, monkey do. But should the saying really go monkey hear, monkey do? Recent studies are finding that the language abilities of some monkeys are more sophisticated than previously believed. Much more sophisticated.

Monkeys live together in social groups. All members contribute by helping to defend food sources, raise young, and watch for predators. But it is impossible to live in a social group without some form of communication. Group members need ways to influence and inform each other. This is what drives language. Monkeys have evolved many ways of communicating, including visual cues, auditory calls, and even some olfactory signals. Some of their visual signals are quite beautiful, like the long, curled tongue of the emperor tamarin, signaling to her mate when she wants to offload her babies. But visual signals only work if they can be seen. In the dense forest and underbrush that most primates live in, auditory cues are a much more powerful tool. Calls and vocalizations can also be modified in pitch, loudness, and duration, which means a vast array of messages can be transmitted. Alarm calls, territorial calls, food calls, personal identification calls, dominance calls — these are the basic messages that primates need to successfully live in groups. But some developed more complex and specialized forms of auditory communication. Some developed language.

No animals have all the aspects of human language, but several species have some. Diana monkeys, seen in Clever Monkeys, are some of the most clever monkeys when it comes to language. They combine calls to make sentence-like messages. This requires grammar. The meaning of the “sentence” depends on what sounds are included and in what order. Added sounds convey more information, like “maybe,” or “not urgent.” Each predator has an assigned call. The eagle call differs from the jaguar call, meaning Diana monkey language includes semantics: signals convey meaning and refer to features in the real world. And what’s more impressive is that the Diana monkeys can understand other species of monkeys. Putty-nosed guenons also combine calls, and their messages can be understood by the Diana monkeys. A remarkable example of multilingual primates is seen in Clever Monkeys, with eight different monkey species living together and listening to each other. With eight times as many eyes on the lookout, it’s much harder for predators to go unnoticed. Each of the eight species has at least 15 distinct calls — that’s 120 different sounds to remember. There aren’t many humans that speak eight different languages.

One of the most interesting aspects of human language is the ability to deceive. Some primates are capable of displacement, or the use of language to refer to things that are not present. Monkeys use both spatial displacement, referring to objects that are not present in that space, and temporal displacement, referring to objects that are not present at that time. The white-faced capuchin in Clever Monkeys that uses displacement to deceive his troop had to think abstractly about invisible objects. And he had to predict how others would respond. It takes impressive intelligence to tell a monkey lie.

It also takes impressive intelligence to live in very large groups of up to 800 individuals like the geladas of Ethiopia. Within the larger band, gelada males are chosen by females, and they live within harems of females. But staying on top of the social order takes a lot of maneuvering. Most importantly, being a dominant gelada requires a high level of social intelligence and an ability to use visual and auditory signals to communicate. Geladas have over thirty distinct vocalizations. These vocalizations can indicate social status, identity, alarm, friendliness, or submission. Grooming strengthens bonds between group members and brings overall stability to the family unit, but geladas spend most of their day shuffling from spot to spot, picking grass with their thumbs and index fingers. With little time to groom, “chatting” has become a substitute way to relieve tension. This is perhaps what our origins resembled, learning language as we moved across the plains.

Photo by Trisha Shears, Creative Commons license.

Rhesus macaque and baby

The life of a monkey is full of ups and downs. Like us, monkeys form strong friendships and bitter rivalries. They fight for each other and take care of one another. And the leader of a monkey troop, when deposed, will even exhibit signs of depression. When we watch their behavior we get the sense that their emotional lives may share something in common with our own.

Friends and Enemies

Monkeys have a complex social system, and they form relationships with each other on an individual basis. When they encounter each other, monkeys will remember back to past interactions. Old rivals can be greeted with rage if they swing into the wrong part of the jungle. As we see in Clever Monkeys, such skirmishes sometimes even end in death.

By the same token, monkeys will remember the help of a friend. Grooming, for example, shows affection and respect. And when it’s time for a fight, a monkey with whom you’ve built a friendship is much more likely to fight at your side — or clean your wounds afterward!

Dealing with Death

Toque macaques huddle together after a member of their troop is killed in Clever Monkeys. Image © BBC

In Clever Monkeys, when the leader of a troop of toque macaques is killed, the others gather in silence around his body. As though they truly feel remorse, even his old rivals now seem to show their deference, tenderly touching their fallen leader.

Everyone is affected by death, but a monkey mother that has lost her infant seems especially hard-hit. In nearly all species of monkey, the mother will carry her child’s lifeless body around with her for days. Do these examples show that monkeys share our emotional response to death? Some researchers suggest that while they may not understand death in the same way we do, monkeys and apes do seem share our tendency to have trouble accepting it.

Stressed Out!

Monkeys suffer from stress, much like we do, and often it seems to relate to social problems. For example, baboon society is extremely competitive. Males who try to move up the social ladder and fail can suffer from high blood pressure and even ulcers. But those at the top don’t necessarily have it any better: high-ranking males who fall from power often exhibit signs of depression.

A Mother’s Love

A mother monkey’s attention and care during her child’s infancy has a significant impact on the young monkey’s emotional development. Infant rhesus and pigtail monkeys react to the absence of their mothers in much the way we would expect a human child to react. At first, they coo for her and search excitedly. However, after a while, they will stop playing with others and take on a slouched posture.

A lack of love from mother and peers during infancy has an even greater effect later in life. In one study, three-year-old rhesus monkeys that were isolated during their first year of life showed much more aggression toward unknown monkeys than did their peers.

From maintaining complex social relationships, to suffering anxiety and depression, there are many trials in the life of a monkey. Perhaps the next thing monkeys should consider evolving is a good therapist.

Photo (top) © Charlotte Scott