The Web of Life – Apes


The mental life of the other great apes is much more sophisticated than is often assumed. ~ German psychologist Daniel Haun

Imitation is commonly called aping because apes do it. The facial muscles of apes and humans are more developed than other mammals, affording a repertoire of facial expressions for communication.

All apes have the capacity for cultural learning and transmission: sharing useful techniques and passing them on to the next generation. Various complex learned behaviors – tool use, grooming, and even courtship – have been seen in various groups of apes.

While monkeys are exceptionally noisy, apes are more reserved: generally speaking only when they have something to say. Apes communicate with facial expressions, gestures, body language, and sound, including extensive vocalizations.

Chimpanzees, orangutans, gorillas, and bonobos make sophisticated decisions, weighing their chances of success. Based upon experience, they estimate likelihood and take calculated risks. Their memory of events in the distant past is at least the equal of people.

Emotions play a critical role in shaping how humans make complex decisions. Apes exhibit emotional responses to decision-making like humans. ~ American psychologist Alexandra Rosati & American evolutionary anthropologist Brian Hare


Orangutans stand out among primates in several ways, including being among the most intelligent. Yet they are among the least social.

Orangutans may live to 30 years. They are the most arboreal of the apes, and the largest tree-dwelling mammal. On the ground, orangutans move more slowly and deliberately than in the trees, where they move quickly.

Adult females and their young rarely come down to the forest floor, except to enjoy eating termites. Adult males may spend a fair amount of time to forage on the ground, then climb up to eat.

Orangutans like water. Sometimes they will wade up their hips across jungle streams.

The trees offer protection from ground predators, most notably tigers, their main predator; though leopards, crocodiles, and wild dogs are threats. Orangutans spend somewhat more time out of the trees when on safer ground.

Orangutans prefer areas which offer a mosaic of habitat types that can provide quantities of food throughout the year. Lowland swamp forests are ideal, as contrasted to hilly or mountainous regions. Population densities reflect this.

Orangutan hands are like humans, with 4 long fingers and an opposable thumb. But orangutan hands are adapted for arboreal locomotion. They lack the dexterity that human hands are capable of, as orangutans have curved hands and feet. Orangutans can grasp objects using their hands or feet. Their feet, like their hands, have 4 long toes and an opposable big toe.

Orangutans have a pronounced sexual dimorphism, in both body size and appearance. Gorillas likewise.

Orangutans are about 2/3rds the size of gorillas. An adult female orangutan averages 0.95 m, 50 kg, while a male is 1.2 m, 90 kg.

Befitting their arboreal lifestyle, with frequent brachiating branch to branch, orangutans have proportionally long arms. Adult males have an arm span of 2–2.3 meters.

Orangutan societies comprise residents and transients of both sexes. Upon entering adulthood, a male disperses from his home ground; entering a transient phase until he can challenge and displace a resident male from his home range. Younger males and females may be nomadic, without a home range.

A female tends to settle into a home range that overlaps with her mother; though an especial social bond between an adult daughter and her mother is not common.

Resident males too have overlapping ranges. An adult male range is typically 5–8 km. Females settle into smaller home ranges, which they usually do not leave.

Orangutans are not territorial but have a decided sense of personal space.

Males play almost no part in rearing young. In contrast, orangutan mothers are exceedingly devoted to their infant offspring. The relationship between a mother and her infant is very affectionate.

Infants are wholly dependent upon their mothers for 2 years. A mother may have the help of older offspring in helping socialize an infant.

Adolescent independence is gradual. A 3-year-old juvenile may appear confident, but only when mother is present.

Juveniles are usually weaned at 4 years, though with considerable reluctance by the youngling. Adolescents socialize with their peers while maintaining contact with their mothers. Offspring maintain close contact with their mothers for at least 5 to 8 years. Young males avoid adult males.

Males sexually mature at 15 years but they exhibit arrested development in a few ways: not developing until later distinctive cheek pads, pronounced throat pouches, long fur, or a spine-chilling mating call (the long call) that attracts females. Such young adults are termed unflanged.

A male typically becomes flanged by the time he is 20, prodded by gaining residence. Transformation from unflanged to flanged can happen quickly, as it is only a hormonal change initiated by social circumstance, albeit resulting in a striking facial change.

Depending upon the social environment, a male orangutan may choose not to flange for years, or even ever. In a society where a dominant male drives out others with cheek pads, a male is better off not displaying his virility.

Being inconspicuous lets a male still have a go at females. While 60% resist the advances of an unflanged male, 40% succumb to forced copulation.

Conversely, in a community where multiple males are flanged, there may be no advantage to staying unflanged. Since males constantly fight over sex, with the smaller one always losing, if an orangutan has what it takes to win mating battles, the flange goes on.

Females become fertile between 6 to 11 years; typically earlier for females with more body fat.

Orangutans have the longest interbirth interval of all apes: 8 years. A female may have 4–5 offspring in her lifetime.

Orangutans are unusual among primates in not practicing infanticide. This may be because of the long infertility interval of females between births.

Adult males have been typified as largely solitary, but that appears to be something of a cultural norm. Orangutans vary quite a bit in how social they are.

Borneo and Sumatra are the 2 islands in Indonesia where orangutans still live, having been wiped out elsewhere. Sumatra orangutans are relatively sociable: gathering in large groups – up to a 100; hanging out, foraging, trading tool tips, sharing food. None of these behaviors have been observed in orangutans in Borneo.

Overall, the intelligence of orangutans and chimpanzees is comparable. Like chimps, orangutans recognize themselves in a mirror.

Orangutans learn by observation and imitation, by trial and error, and by exploratory behaviors involving varying degrees of chance, depending upon an individual’s appetite for risk. Orangutans are quite capable of planning and executing complex tasks and considering contingencies.

Readily navigating the canopy requires a deep spatial memory, as well as cleverness at times. When a canopy gap is too wide to accommodate simple tree swinging, an orangutan may break off a branch and use it as a hook to rake in the tree on the other side.

Imitation is the basis for cultural transfer. Sumatra orangutans appear to employ tools more often than their Borneo brethren, but both are known to use tools.

Orangutans are selective eaters that require enormous quantities of food. Their diets are dominated by fruit (60–90%), with shoots, leaves, and bark as supplement. Flowers, fungi, insects, honey, and bird eggs are on the menu when they can be had. Borneo orangutans have been observed eating 317 different food items.

When plentiful, orangutans gorge on fruit. Males particularly put on pounds at the prospect of leaner days. A male may eat 11,000 calories a day during high-fruit season, as contrasted to 2,000 daily calories when dieting on fruit, tree bark, and leaves during low-fruit times.

Orangutans congregate at large fruiting trees when fruit is abundant; residents and transients alike. Subordinates, especially males, defer to dominant members for choice spots. At such times, individuals naturally engage socially.

Orangutans sporadically practice geophagy: eating soil or rock. They do so: 1) to add mineral nutrients; 2) to detoxify, by ingesting clay that absorbs poisons; or 3) medicinally, to treat a disorder, such as diarrhea.

Orangutans apply dayflower leaves as an anti-inflammatory balm, after first chewing the leaves a bit to produce a useful lather.

Foraging is not an exercise in rambling about the home range. Orangutans have excellent memories, allowing them to remember the multitude of food source locations, and the time of year when different fruits ripen.

The tasty pulp and seeds of Neesia fruit – rich in fat and protein – are guarded by sharp needle-like hairs, making getting at the treat using the fingers too painful. So, a smart Sumatra orangutan teases out the treat with a stick. These orangutans also modify sticks to reach honey or insects nestled in trees. And go fishing. They might also use a stick for scratching their back. When it rains, they hold large leaves over their heads as umbrellas.

Orangutans also employ tools in agonistic situations: grabbing a piece of bark for a fight with another orangutan; clubbing snakes, lizards, and other animals with sticks; or throwing objects at other animals.

Orangutans use coconut shells or husks as dippers and fluid or food containers. They use crumpled leaves as a sponge to absorb water to drink.

Orangutans make seat cushions from leaves, as well as making more elaborate beds for a good night’s sleep. Night nests are carefully constructed: taking up to 10 minutes to build a sturdy nest, that, if well done, may last for months to well over a year if in a densely wooded area.

Orangutans cognize material properties and mechanical design. They use strong, rigid branches for the structural part of a nest to support their weight, reserving weaker, more flexible branches for a nest’s lining. Further, support branches are fractured differently than lining branches. Orangutans know the ways in which branches break, and use that understanding to build safe, comfortable nests.

Orangutans have learnt about the mechanical properties of wood and use this knowledge in a clever way. ~ English biomechanist Roland Ennos

If anything, night nests are over-designed, as they are almost always used only once, unless there is no other choice. Changing night nests is sanitary: an excellent way to avoid ectoparasites and the diseases they carry.

Youngsters learn from mom. From 6 months on, orangutans practice nest-building, becoming proficient by the time they are 3 years old. Nest-building is a leading factor in juveniles distancing themselves from their mother for the first time.

Chimpanzees also build sleeping nests, though they are not as accomplished as those built by orangutans. An experienced chimp will put together its night nest in a minute.

In climbing a thorny tree, an orangutan might use stacks of leaves as gloves to pad the hands and feet. Leaf glove use has been seen more often among Sumatra orangutans than those in Borneo.

Unlike most forest-dwelling primates, orangutans are rather silent. They move noiselessly.

While male orangutans may journey through the forest alone, they maintain their social connections. A male on the move schedules his day: announcing the evening before where he plans to go the next day. If he alters his plan, or decides on a different route, he lets his friends know.

Wild orangutans do not simply live in the here and now but can imagine a future and even announce their plans. ~ Dutch primatologist Carel van Schaik

Orangutan communication is not well understood. They clearly have a wide variety of vocalizations: grunts, barks, squeaks, and screams. Orangutan young scream when distressed but are otherwise quiet. The repertoire includes “blowing a raspberry”: putting the tongue between closed lips and producing a flatulent sound. Body language is often used to communicate.

When annoyed, an orangutan will suck in air through pursed lips. Japanese people do the same when facing a difficult situation.

Chantek – a male orangutan – was born in captivity. He was reared much like a human child: toilet trained and taught to do household chores. Chantek mastered sign language, becoming so proficient that he invented some signs of his own upon discovering new objects. Chantek also understood spoken English.

Loud vocals are rare, apart from the personalized histrionics that flanged males summon: the long call, which attracts fertile females interested in that male.

The last long call of the day is when a flanged, male orangutan tells his ladies where he is, and is going to be. Females stop moving when they hear this call and bed down for the night. In the morning, they travel in the direction indicated by the call.

Females have decided mating preferences, both generally and individually. Females typically prefer the most dominant male with whom relations are cordial.

Females consorting with a dominant male are less likely to be raped, as a dominant male normally won’t tolerate another male nearby. Rape is somewhat common, particularly by young, transient (unflanged) males, who have little prospect of sex otherwise.

As males take no part in upbringing, a dominant male happily sires the offspring of several females.


Gorillas are the largest primate. Adult males average 157 kg and stand 1.7 meters. Dominant silverbacks may reach 230 kg and 1.8 m. Females are 1/3rd smaller than males and about half the weight.

In the wild, a gorilla may live 30–40 years. Zoo gorillas have lived to be 50 and more.

Gorillas have short, compact bodies, though with thin, long arms, averaging 2.4 meters (females: 2.1 m). Long arms afford gathering fruit and leaves otherwise out of reach.

Gorilla sight, smell, hearing, and touch are comparable to humans, but their sense of smell is decidedly better. Gorilla vocal cords are different, limiting their vocalization versatility. Gorillas tend to be quiet, though they bark when curious, hoot when alarmed, roar when upset, mumble softly and belch when content.

Facial expressions are telling. Gorillas display a range of emotions that mirrors humans. A stern, fixed stare with lips together tightly shows aggression. An open mouth with exposed canines conveys surprise or fear. Eyes shift nervously when afraid.

If uncertain, a gorilla pulls its thin lips against its teeth, much as a person would. The tongue may peek out of tight lips when concentrating, as humans do. A playful display is made by relaxed eyes and a casually open mouth without showing teeth.

Gorillas gesture. A slap displays displeasure. Submission is shown by a compacted body, arms folded in front or over the head, like people do when they feel defeated.

Males beat their chest to show aggression, but also as a signal to maintain contact at a distance. The hollow sound of chest thumping may be heard a kilometer away.

Male gorillas have massive, wide chests, and powerful shoulders, necks, and backs. They are also naturally potbellied.

A male gorilla reaches maturity at 10–13 years. At this age, it grows a thick crown of head hair. The hair on its chest falls out. The hair on its back turns silvery gray. Hence the term silverback for the dominant male of a troop.

Younger males are called blackbacks. All young and female gorillas have black hair.

A vegetarian diet has a lower concentration of nutrients, requiring a lot of gut room. An adult male may eat 23–30 kg of food a day.

Favorite gorilla foods include bamboo, wild celery, and blackberries. Bracket fungus is a treat, and so well-liked that its discovery is likely to raise a ruckus if the find is spotted by more than 1 gorilla.

Plant leaves, branches, stems, roots, and fruit are all on the menu, depending upon availability. Termites and ants supplement the diet. Gorillas seldom drink water, as their diet provides enough liquid.

Gorillas are slow, deliberate eaters. They carefully examine their food, choosing the best fruit and leaves.

Gorillas use their long fingers to peel away the hard outer parts of plant stems so they can eat the juicy inner pulp. Gorillas like to hum, grunt, or smack their lips while eating.

A particularly tasty morsel may prompt a gorilla to distance itself from the group before eating, to avoid having it stolen or having to share. Otherwise, the natural sounds of consumption contentment would give a gorilla away.

Like chimps, gorillas knuckle-walk, which saves wear and tear on the hands. The backs of their knuckles are protected by thick calluses.

Gorilla and human hands are similarly shaped. Like chimpanzees, gorillas have prehensile feet.

Like humans, infant gorillas have baby teeth which fall out and are replaced by an adult set. Gorillas are also like humans in having a 4-chambered heart, and the same blood types (A, B, AB, O).

While they spend a lot of time on the ground, gorillas make a night nest in the trees to sleep in; a task that typically takes a minute or 2 for a skilled builder; up to 5 for the less adept. For hygienic reasons, gorillas never use the same nest twice. Gorillas may defecate in their nests at night but their dry manure doesn’t stick to their fur.

Gorillas lead nomadic lives. Each day they travel to a new area of their home range. Constant movement avoids overgrazing. The general pattern is to forage a ways away: from a few hundred meters for mountain gorillas to several kilometers for lowlanders.

Troop ranges of mountain gorillas run 6–12 km. Lowland gorillas have a somewhat larger range, as their food resources are more widely dispersed.

Gorillas are not territorial. Troop ranges often overlap. Lone males may have a home range that overlaps that of several troops.

Though they prefer not to run into each other, 2 groups may feed side by side without conflict. In such situations, adults tend to ignore one another, thought juveniles of the 2 groups may play together.

Gorilla troops number 2 to 30. Troop hierarchy has at its apex a dominant silverback male, overseeing a harem of breeding females and their young.

A troop acts as a family. A silverback will give his life, if necessary, to protect his troop. This social structure makes for an orderly society. Violations of social mores are dealt with swiftly and firmly. The dominant silverback rules. If 2 are fighting over food, a stern stare from the silverback ends the conflict.

Females and males may leave a troop when they mature. Gorillas are careful to avoid inbreeding. A young male typically lives alone for several years, until able to seduce a female into joining him to form a new group.

Only the dominant silverback mates with the females in his troop. His troop’s offspring are his own. When a new silverback seizes control of a troop, or takes in a new female, he may kill infants sired by other males.

Chimpanzees often employ sexual behavior for bonding among group members. Gorillas are not so inclined.

Gorillas mate only occasionally, any time of the year, as the tropical climate provides food year-round. The female menstrual cycle generally follows the lunar cycle, as it does with women. Gorilla mating usually occurs mid-cycle, close to ovulation. Females initiate mating more often than males.

Gestation is 8 1/2 months; a couple of weeks shy of human gestation. After birth, a mother licks her newborn clean, and often eats the placenta.

Females bear a single offspring. Twins are rare: 1 in 110, as contrasted to 1 in 80 for humans. A female bears a child once every 3 to 4 years; sooner if baby does not survive.

Gorillas are attentive, caring mothers. Mothering is a learned skill. As gorillas are polygynous, mothers are the primary caretaker.

Baby gorillas need affectionate nurturing to grow into healthy adults. Uncared-for females do not know how to be good mothers. Young females practice and learn parenting skills. Mothers let an older daughter babysit from time to time.

A female may have only 3 to 4 progeny that survive to adulthood. The first years are the most dangerous. Nearly half of offspring die before reaching 6 years, from disease, hardship, or injury. Most fatalities are infants less than a year old. In the best of times, gorilla populations grow very slowly.

One silverback may challenge another for troop domination. They beat their chests, grunt, howl, and break off tree branches to show their determination. Before leaving his home group, a young male may challenge the troop leader, almost never successfully.

Seldom does a challenge come to bites or blows. Intimidation most often does the trick. A gorilla concedes defeat by staring at the ground or leaving the scene.

Gorilla troops generally lead a relaxed life. Mornings and afternoons are spent foraging and feeding on favorite foods. In the meantime, adults nap in a nest while youngsters play. Young gorillas like to tickle each other, wrestle, play follow-the-leader, king-of-the-hill, and tag. All gorillas in a troop, even the silverbacks, play gently with babies.

Females reach reproductive maturity around 8 years; males about 10 years. Gorillas have a longer adolescence than any other primate save humans.

Grooming consumes a fair portion of free time, though gorillas are not as tactile as some other primates. Gorilla babies are in almost continuous contact with their mother. A mother grooms her offspring. Adolescent friends sometimes groom each other. Adult females groom the dominant silverback, though without reciprocation. Otherwise, grooming between adults is rare.

Gorilla life is typically idyllic in its peacefulness. Disputes do arise from time to time, however short-lived.

Gorillas throw objects agonistically. At one zoo, a female gorilla would frequently strip a branch from a tree, sharpen a point at one end with her teeth, and chuck the spear at a disliked caretaker.

Gorillas can creatively employ tools. One female was observed sitting on a stump digging herbs with a stick. Another tore a branch off a tree to help gauge water depth as she waded into a deep pool.

Overall, gorillas are not big tool users, as there is little need. Most everything needed is at hand. Nest-building is about the only manipulative skill that a gorilla regularly practices.

As with chimps, female gorillas tend to use tools more often than males. Tool tips are shared. Mothers train their young for 3 to 5 years on a variety of matters, including tool use.

Human researchers long wrongly considered gorillas a lesser intelligent primate, especially compared to chimpanzees. This may have been because they are more gentle, shy, less aggressive, and vegetarian.

Gorillas flunked the mirror test. The gorillas didn’t even look. The researchers were stumped for quite some time, considering the complex social structure that gorillas have.

Finally, it dawned upon the dim humans that gorillas are shy of making sustained eye contact. For a gorilla, staring is an act of aggression. A quick glance at a mirror image, seeing another gorilla, satisfies a gorilla of a presence. Further curiosity about the mirror image is curtailed out of politeness.


Koko has some predisposition to think and analyze. The ways in which she learns about the language are similar to the ways human infants experiment with language, particularly deaf children learning the same language Koko is acquiring. Koko has a grasp of the underlying structure from which signs are generated. ~ American psychologist Francine Patterson

Koko became a famous gorilla. Born 4 July 1971 at San Francisco Zoo, Koko was taught sign language a little late: beginning when she was 1 year old. Koko came to understand more than 1,000 signs of sign language, and about 2,000 words of spoken English.

Koko invented new signs to communicate novel thoughts. Upon seeing a ring on a human finger, Koko had no word to point it out, so combined finger and bracelet to describe what she saw. The first time Koko saw a duck on a lake, she signed “water-bird.” Melon juice was described as “fruit-drink.”

The essense of Koko’s humor is her ability to diverge from norms and expectations in a recognizably incongruous manner. Her humor taps in various ways her capacity for displacement, a cardinal attribute of symbolic communication. These capacities are further confirmed by a number of Koko’s other creative uses of language. ~ Francine Patterson

Having been reared by humans, without normal gorilla social inhibitions, Koko readily passed the mirror test, showing that gorillas possess self-recognition, though they would be too shy to show it in the wild.

Koko also played with dolls, treating them maternally: carrying, cradling, kissing, putting a doll’s face on her nipple to suckle.

A grieving adult female gorilla in the wild, who had lost her 1-month-old infant, fashioned a doll from vegetation and treated it with the same care as she had her child. Chimps are also known to indulge in making and playing with dolls; one instance involved a young male.

Koko shares many of our mental experiences. When she looks at the world, she is conscious of her surroundings and, to a degree, of the laws that govern them in much the same way that we are conscious. ~ Francine Patterson


Gorillas share their habitat with hundreds of animal species, but direct interactions are few. Gorilla lifestyle, including vegetarian diet, is ecologically idyllic.

Gorillas are among the most powerful creatures. Few predators will attack a gorilla troop, excepting leopards and humans. A leopard my occasionally stalk and kill a young or weakened gorilla.


Our genetic cousin is half our size and weight. As with humans, chimpanzee sexual dimorphism is modest. Adult female chimps are 0.66–1 m and 26–50 kg, while males are 0.9–1.2 m and 35–70 kg.

Though they face many dangers, chimps may live for more than 50 years.

Chimpanzees are quadrupeds. They are excellent climbers, but also travel on the ground.

As their arms are longer than their legs, chimps walk on all fours. Their heads are above their backs and rear, letting them easily look forward instead of down. To protect their hands, chimps walk on their knuckles. Better than gorillas, chimps can walk on 2 feet for short distances but find knuckle-walking faster and easier.

Chimpanzee hands resemble human hands, with 4 flexible fingers and opposable thumbs. Chimps have nails on their fingers and toes, not claws. They readily grasp objects as humans do. Chimp thumbs are shorter than ours. A chimp cannot touch its thumb and forefinger together.

Chimp feet look much like human feet, but the big toe is longer, more flexible, and more useful. A chimp can readily grasp objects with its feet; something we cannot do.


Chimpanzees are omnivores. They will eat anything that is not toxic: flowers, fruit, foliage, eggs, birds, and small mammals, including monkeys.

Each morning, community members break up into small groups to forage. A mother and her children are a typical foraging group. If they find a tree full of fruit, they tell the others with excited cries.

Chimpanzees remember when certain tree species produce fruit. They use their botanical knowledge to forage.

Chimps hunt when the opportunity presents itself. They are the only ape that hunts in groups.

Males are more prone toward hunting; a relative few do so on their own. Most prefer a group endeavor led by the troop leader. Several chimps may work together to stalk monkeys in the trees. Some wait quietly while others drive monkeys into an ambush.

Hunting necessarily becomes a cooperative venture when larger or more elusive prey is spotted. A troop will encircle a hapless intruder, driving it toward others in the hunting party until the animal is caught. A kill is made by a bite to the neck, or battering it with a rock, stick, or bashing it onto the ground.

A successful hunt is cause for celebration: a time of great excitement. The catch is shared among the hunters, with the killer doling out the spoils. The males tolerate begging females, who can get a bite if there is enough to go around.

 Tool Use

Palm hearts are tasty but not an easy treat. How does a chimp connoisseur procure oil palm pith? First, climb up the palm tree. Pry apart branches with hands and feet. Pull off a palm frond. Use the frond as a pestle to pound the hard-shelled pith at the center of the tree crown, softening it. Lunch is served: scoop up the pounded pith.

Nuts are cracked using a flat stone as a hammer, after placing the nut on a stone anvil.

Chimps readily pick up sticks and large stones for weapons. Using their teeth, they sharpen sticks for hunting spears, such as for stabbing bush babies deep within tree nests. Those little night monkeys are delicious. A chimp does not need to see that a bush baby is there. Indirect evidence indicating the likelihood of a bush baby lunch is sufficient to work a spear.

Chewed leaves are wadded up to sponge up water in the hollows of trees, or even to drink from a stream. Leaf sponging is quite common.

When water is scarce, chimpanzees dig up water-holding roots and carry them along like a thermos. To get a drink, they squeeze water from the root pulp.

Chimps use leaves as napkins, as a washcloth, or for toilet paper.

Chimpanzees learn to fish for termites and ants. The process takes years, as chimps must learn when to fish. October and November are peak termite season. They must locate sealed termite tunnels. Then there is the issue of tools, which are typically carried to the site.

Sturdy but pliable twigs are stripped of leaves, bitten off to get just the right length. The stick tool is then inserted in the tunnel with a twisting motion, to follow the curves of the termite tunnel. A chimp vibrates the stick to alert and attract termites. The stick is then carefully retracted, to avoid scraping off the termites on it. Finally, a lick of the stick, and yum: tasty termites. An anthropologist researcher who studied the technique for months was no better at it than a novice chimp.

Army ants are a spicy staple. Chimps eat them year-round. Eating ants requires the right tools. Scooping up army ants with the hands would just mean getting badly bitten. Chimpanzees prefer a specific woody plant for their ant dipping sticks. Longer sticks are preferred for more aggressive ants, to avoid their crawling on the fingers.

Researchers have seen over 35 distinct tool types used by different chimp colonies. After being shown how, captive chimps demonstrated the ability to combine tools, and do so cooperatively, such as putting boxes one on top another to reach a hanging banana that cannot be otherwise reached, even with a stick. One chimp knocks the banana down while others help stabilize the boxes. Chimps form a mental representation as a basis for problem-solving.

Tool use follows the human pattern: apprentices learn from masters. Female chimps are the big tool makers and users, some creating clever adaptations.

Adult male chimpanzees seldom employ tools except as battle weapons. As such, males do not depend on food requiring tool use. Females may have evolved greater tool use because they do not participate in group hunting.

Tool use among chimpanzees is cultural. If a chimp is using a tool to good effect, others in the community observe and learn.

All chimpanzees sleep in nests made in the trees from sticks and leaves, which are normally built each night; though chimps use them for a siesta during the day. Juveniles learn nest-building skills from their mother. An infant sleeps with mom in her nest.

Chimps like firm, stable beds. They strongly prefer Uganda ironwood trees to sleep in. Its wood is stiff, with branches that have the best bending strength.

Mothers teach their young a diverse variety of survival skills, tutoring them for 3 to 7 years. The young copy mom. Early attempts are often clumsy. Along with motherly tips, practice renders proficiency.


Chimpanzees definitely have a very complex communication system that includes a variety of vocalisations, but also facial expressions and gestures. Chimpanzees use vocalisations in a sophisticated manner, taking into account their social and environmental surroundings. ~ Canadian primatologist Ammie Kalan

Chimps chat and gesture. Human hand gestures tend to be like those used by chimps, who tend to profusely gesticulate. Chimps try to convey how they feel and what they think.

While many gestures are individual, certain gestures are a social norm, or innate. Presenting one’s rump, crouching down, or holding out a hand indicate submission.

Facial gestures are quite expressive, owing in part to having loose, flexible lips. Toothy grins are of fear. When together, scared chimps will touch each other for emotional support.

A pout indicates interest, especially for a food. Wide-open eyes show excitement. A male chimp may flip his lip when he sees a female he is fond of. A grimace or frown is a sign of aggression. Lips squeezed together are often seen during fights.

Chimp speech nominally comprises 13 distinct types of calls, but their vocalizations are tremendously varied, conveying message content and emotion.

Chimpanzee vocal cords are unlike their human descendants; so, they do not speak in the same way. Chimps have tonal languages, analogous to the tonalities found in Chinese and Vietnamese.

Each chimp has its own distinctive voice, with characteristics reflective of its personality: louder or quieter, high- or low-pitched. Members of a troop recognize one another by their voice.

Young chimps learn the nuances of the language used by adults. A chimp relocating to an area with a different dialect quickly picks it up.

Chimpanzees make long-distance calls to each other, which are called a pant-hoot. A pant-hoot is made accounting for the acoustics of the immediate habitat. Slower, lower-frequency calls are made in a forest, to compensate for sound scattering, than in a more open area.

Chimps have been taught sign language and use it adroitly, including employing basic syntax. A chimp named Washoe learned more than 300 signs, and even concocted some of her own. Her son learned 50 signs from his mother.

Chimpanzees comprehend symbolic representation, such as name, number, and color. They have learned to use symbolic keyboards, to ask questions and request food. One research chimp – Kanzi – understood spoken English.

Like people, chimpanzees take into account the information that others may have in deciding to speak up. A chimp is more likely to let others know of a potential threat, such as a snake, if it thinks that they are not yet aware of the danger. Otherwise it keeps the obvious to itself.

 Personality & Emotions

There are striking parallels of personality between chimpanzees and humans. ~ American psychologist Sam Gosling

Humans personalities have 5 recognized dimensions: sociability, amiability, conscientiousness, neuroticism, and experiential openness. The observed chimp variant of conscientiousness is methodicalness.

Chimps are not inclined to the chronic emotional indulgences that many people are. But they are subject to deep-seated mental stress, which relates to fear. The chimp equivalent of neuroticism is reactivity.

Chimpanzee society is invariably hierarchical. Thus, chimps have an additional dimension of personality not generally recognized by psychologists for humans: dominance.

While human groups commonly have dominance hierarchies, and an innate sense of preeminence in relationships, some people also have a sense of egalitarianism. People do have a similar personality dimension relating to social status, but it is somewhat subdued compared to chimps.

Chimpanzees demonstrate empathy and have innate senses of reciprocity and fairness. Compassion motivates, as does a sincere request for help.

Chimpanzee sense of empathy is limited to familiars. Unfamiliar chimps, or other animals, such as baboons, merit no such response.

Chimpanzees and gorillas are as emotive as humans: conveying a wide range, including grief, frustration, and joy. Their faces and gestures express what they are feeling, as do their hugs and kisses, hand holding, pats on the back, and mutual grooming.

Chimps have a sense of humor. They love to tickle each other and laugh.

Chimps have an aesthetic appreciation of Nature. They contentedly sit and enjoy beautiful sunsets.

On the sadder side, imminent mortality brings anxiety to close relations. Dying friends are looked after, and their loss mourned. An infant whose mother dies may be beyond consolation: refusing to eat and starving itself to death within a few weeks. Out of grief, a mother whose infant dies may refuse to abandon it for days or weeks.


A female chimp may have 4 or 5 offspring in her life, giving birth every 5 to 8 years. She continues to care for her older children when a newborn arrives.

The nuclear chimpanzee family comprises a mother and her children. The closest relationships are between a mother and her grown daughters, who help with rearing youngsters. A female with a newborn, but no family relatives, may seek the protection of a male.

A female mates with several males. With uncertain paternity, males have no interest in babies or paternal caretaking.

Gestation lasts 200–260 days; about a month shorter than human pregnancy. Birth comes at rest in a tree nest, usually at night. Twins are rare.

Babies are of great interest to the family, but chimp mothers are highly protective of their infants.

For the first 3 months, a baby clings to its mother. After that, an infant strays for short periods; though mom is always nearby, keeping a sharp eye on her precious little one. She still carries her child as she travels through the forest. At night, the baby sleeps cuddled in mom’s arms.

At 4 months, a baby starts eating solid food, at first borrowing bits from mother to try. Young chimps take all their early cues from their mother.

Not until they are 3 years old do younglings venture more than 5 meters from their mothers. Their infancy ends between ages 4 and 6, when they are weaned.

Like many mammals, weaning is the first significant negotiation in a young chimp’s social life. While the outcome is certain, an infant has no knowledge of that.

From an infant’s perspective, weaning is conducted with a social partner of paramount importance to survival. The process leading to resignation, and inevitable entry into a new phase of increased independence, shows a combination of conflict and conflux of interests, and a cycling between positive and negative interactions.

This first significant pattern of conflict as negotiation will be innumerably repeated in a chimp’s life. It is particularly critical to ambitious males, who, as adults, constantly jockey for social position.

Young chimps are most playful when 3 or 4 years old. They learn socialization, particularly communication and grooming, which plays a large part in chimpanzee social life.

Chimpanzees share the trees of their tropical forest with a variety of birds and monkeys. Young chimps and monkeys sometimes play together if their family groups are nearby, and the vicinity feels safe.

At first, an infant is groomed only by its mother. Later, when the child has learned how to groom, it begins to join in grooming sessions with others.

Adolescent chimps play with sticks as toys. Juvenile females tend to carry sticks as dolls, mimicking childcare.

Young males are more into rough-and-tumble play. Sticks are more likely brandished as a weapon. Mock battles are common.

At 8 years, a youngster is half the size and weight of an adult. It can fend for itself. But chimps stay with their mother until they become adults, at the age of 13 or 14 years.

Chimpanzees mothers endow their offspring with essential skills. Social skills are especially important.


A happy chimpanzee is one that is living in a complex society with his fellows. ~ American primatologist Stephen Ross

After a bit of socializing, a chimp starts its day with a morning forage. Chimps might take to a cool cave to get out of the hot Sun, sometimes enjoying a picnic lunch. Several hours are spent with a midday meal, relaxation, and social activities.

Time to forage again in the afternoon. Up to 6.4 km may be traversed during a day, searching for food. Chimps spend a lot of time in the trees, as well as sleeping there in nests.

Much time is spent socially: grooming and in play. Friends and family stay together.

What draws and keeps both chimpanzee and human friends together is similarity in gregariousness and boldness. ~ Jorg Massen

A chimp’s closest companions are those who are like-minded. Chimps are most comfortable with others that approach the world like themselves.

A chimpanzee has little body fat, so a chimp does not float in water. Therefore, as suitably adaptive behavior, most chimps avoid going into the water. Contrastingly, savanna living Fongoli chimps in Senegal frolick in the water. These are the same tool maven chimpanzees described before. These behaviors are cultural adaptations.

Chimps live in a fission-fusion social group: a community of up to a few hundred individuals, with dynamic sub-groups that include families, friends, and coalitions.

Everyone in the community recognizes one another. Each community member has a relationship with most every other member. Hence matrices of bonds exist. Though similar in nature, chimp society is more close-knit than modern humans have.

There are separate male and female dominance hierarchies in chimp communities. Females typically inherit the ranks of their mothers.

An alpha male leads a community, with strata of subordinates. Male leaders defend the community from predators and home wreckers and help keep the peace.

Coalitions among chimpanzees, particularly adult males, are exceptional in their frequency, complexity, and flexibility. The most persistent coalition is an alliance by relation or close friendship, especially friends bonded from an early age.

Some males are notoriously fickle: opportunistically changing sides to be in the winning team at the moment. Being in a winning coalition notches a male up in social rank, with better likelihood of mating with a female in estrus.

Male coalitions often enter into alliances with high-ranking females who have their own cliques.

Males complete a border patrol around the community territory every few days, looking for possible incursions by horny males seeking females.

Chimps are territorial. A typical range is 5–52 km2 in forests, and 117–557 km2 in grasslands.

If chimps on patrol hear a rival group, they stealthily approach to check out the situation. If they think they outnumber the outsiders, they hoot and scream to drive them away.

Fighting within a community does occasionally happen. Members of rival groups will readily kill one another. Chimpanzees fight by hitting with clenched hands and feet. They scratch and bite.

Overcrowding can lead to violence, with rival males in the same troop fighting one another. At such times, adult males may kill infant males.

Though rare, a social schism in male leadership can break a peaceful community into camps. A breakdown in comity and sense of resource entitlement can lead to war.

Chimpanzee violence can be extreme in its brutality. Male chimps may be castrated or disemboweled for insubordination.

Females do not escape violence, either as victim or perpetrator. A stressed male may routinely beat his mate to try to prevent her from choosing another.

Murderous sociopathy was seen in a mother-and-daughter duo that stole, killed, and ate baby chimps from their own community. Such violent mental illness is rare in chimps.

The primal aggression of humans descends from chimpanzees. It exists for much the same reasons and is similarly motivated. Like chimps, bands of human aggressors are almost always male.

Adult male chimp life is not all security detail and ultra-violence. Sometimes they get wild: males often break out with a crazy dance, designed especially to impress other males. They make their hair stand on end. They stamp their feet, break branches, fling rocks.

Rain and wind is a great excuse for a dance party. Adult males dance together, stamping and hooting as the rain pours down and the wind howls.

The hollow trunks of trees make great drums, pounded on by agile feet. The noise carries far into the forest, letting other chimps know that this troop is still alive and well: rock n’ roll, chimpanzee style.

Male adult chimps come and go from their troop from time to time but return from a foray with an emotional “welcome back.” Females tend not to travel as much as males, preferring to forage within community territory.

Unlike most other primates, males remain in their natal community. Males welcome new females into their community.

Young, sexually mature females typically emigrate to another community, thereby precluding inbreeding, which would weaken the gene pool. Females in large communities sometimes do not emigrate.

The females of early hominins, Australopithecus africanus, also emigrated to find mates (patrilocality). Humans descended from these australopithecine ancestors.

In contrast to outgoing females, with their social graces, adult chimpanzee males are too aggressive toward male strangers to form bonds. Males only bond with those who they grow up with.

Young males are accommodated into the social structure of their troop. A male’s ascent in the hierarchy depends upon his personality. The highest positions are held by the smartest, socially savvy chimps, not the largest or strongest.

Chimpanzees create a hierarchical social arrangement that accommodates sharing, tolerance, and alliances from below.

While high-ranking individuals have disproportionate privileges and influence, their dominance depends to some degree on acceptance by those who submit. Ultimately, dominance creates a responsibility to deliver benefits to the group, whether the leadership is in successful hunting or in maintaining social order.

The dominant male is the first to mate with a female in heat. Others wait their chance. Several may mate with a female in quick succession. High-ranking males who habitually practice sexual coercion have more offspring.

Long-term patterns of intimidation allow high-ranking males to increase their reproductive success. ~ American evolutionary anthropologist Joseph Feldblum et al

Sometimes a female in estrous goes into the forest accompanied only by a chosen male. The pair honeymoon for several days: a practice known as consortship. It is a most auspicious time for a female to become pregnant.

Festering conflicts rent the social fabric of a group. Chimps maintain social cohesion by policing conflicts.

Impartial nonparticipants will intervene in an ongoing quarrel to quell it. The policing role is typically taken by high-ranking member of the group, female or male.

Chimps practice reconciliation, which ameliorates lingering hard feelings. After a fight, and a bit of cooling off, chimps will approach each other. One of the former combatants will extend his hand for a shake. This is often followed by an embrace, even sometimes a kiss.

The tension between competition and cooperation works itself out in a negotiation process characterized by agonistic conflict, temper tantrums, greeting ceremonies with uncertain outcomes and so on. The end result is often a state of mutual acceptance and respected boundaries of behavior. ~ Dutch primatologist Frans de Waal

Alliances and social status profoundly affect the lives of male chimps, whereas such social machinations are less pressing to the immediate prospects of females. As such, reconciliation is generally more critical to males than females. Conflicts among males are more often quickly reconciled than those between females.

Chimpanzees share as readily as humans. The inclination to selfishness or generosity is an aspect of personality. The closeness of social bond often makes a difference. In these regards, chimps exhibit the same spectrum of sharing as humans.

Oxytocin – the bonding hormone for humans – works in selfsame fashion with chimps. Food sharing creates a social bond by elevating oxytocin in both giver and receiver.

Like humans, a chimp’s natural selfishness is tempered by social considerations. Given the choice between being popular and making out materially, most chimps prefer profit. Materialism is as inbred in chimpanzees as it is humans.

Chimps are at least as cooperative as humans, if not more so, as their societies are more closely bonded, and anti-social behavior more strictly proscribed.

Younger chimps generally respect their elders. This is a product of chimpanzee upbringing and culture.

Chimps console each other. A chimp having witnessed an altercation, but not involved, will approach one of the fighters, with a consoling hug, kiss, or grooming; winner or loser. Like reconciliation, consolation eases group tension potential. Consolation indicates empathic theory of mind.

Frans de Waal observed “Mama,” a senior female, act as a chimp arbitrator. Mama was keen on promoting social harmony, particularly among the dominant adult males in her group. After a dispute, Mama would approach and group one of the participants, loser or winner, and groom him for a while, relaxing him. Mama would then gently take the male by the hand or arm and lead him to the other former opponent. She would groom the other chimp, while the first gave her a bit of grooming. Eventually, Mama would smoothly extricate herself, leaving the 2 males grooming each other.

Chimpanzees not only intentionally coordinate actions with each other, but that they even understand the necessity to help a partner performing her role in order to achieve the common goal. ~ English primatologist Alicia Melis

Chimps plan and work together to achieve goals. They help each other and transfer tools as needed.

Many of the limitations that chimpanzees have in collaboration are not cognitive, but motivational. In their native habitat, content with their way of life, there is little incentive to perform the complex tasks that they are capable of.


Chimpanzee societies tend to be more stable than human ones. Communities last from several hundred to 2,000 years or more.

From grooming techniques to tool use to foraging and hunting to courtship, different chimpanzee groups have distinct cultures which are transmitted from one generation to the next. Over 3 dozen behaviors have been identified that are purely cultural.

Chimpanzee groups display great stability and longevity. Cultural differences are maintained through social learning, in which group members conform to observed behaviour, either during their juvenile development or as newly immigrant females.

Although females act as an important cultural vector, bringing new behaviours into a group when they arrive, resident males act as a brake on the speed at which cultural variation accrues. Without such a conservative mechanism, cultural differences between groups would be eroded with each passing generation. ~ English archeologist Michael Haslam


The intelligence of chimpanzees is comparable to humans. Both are born with immature forebrains that develop during childhood. Both to some degree inherit their cognitive aptitudes. Chimps and humans learn in the same ways.

Due to bias and unshakable belief in human superiority, researchers failed for decades to decently test and report results on ape intelligence. How smart is that?!

Numerous contemporary researchers in comparative psychology have claimed human superiority over apes in social intelligence. Direct comparisons of humans with apes suffer from pervasive lapses in research designs and systemic interpretive bias. Much of the existing scientific research is deeply flawed. ~ English psychologist David Leavens, American cognitive psychologist Kim Bard, and American psychologist William Hopkins, in 2017

 In the Mirror

Chimps learn to recognize themselves in a mirror. At first, a mirror appears magical: a chimp treats the image as if it were another ape, checking behind the mirror to find the other one, just as a human child would. After a few hours, having understood the mirror concept, chimps use a mirror to view body parts normally hidden from view.

Chimp learning of how a mirror works mirrors human children, who comprehend mirrors between the age of 15 to 18 months. This comprehension occurs as a series of realizations rather than a single epiphany.


Chimpanzees have excellent memories; a necessity for living in a complex society. Young chimps may be better at remembering numbers than adult humans.

Chimpanzees are capable of introspection: knowing what they know, and what is in their mind.

While the cognitive differences between chimpanzees and humans is of degrees, notable differences are both obvious and striking. Hominin language development evolved beyond what chimps have bothered with. Humans took to altering their habitat with an ardor that chimpanzees lack. As with the tendency to teamwork, these owe in part to motivation as well as aptitude.

◊ ◊ ◊

For all the studious fascination with our smaller cousin, much remains unknown about the inner life of chimpanzees. That of course applies to all species, including our own.

For all the intense interest throughout history, the study of human psychology has produced more misunderstanding than comprehension. Likewise, the pecuniary folly of human economics demonstrates how little men understand social systems or the environment in which people live. Modern human civilization most emphatically illustrates how human reach exceeds its grasp, especially husbanding our habitat in a sustainable way. In contrast, chimps deserve no such condemnation. In sum, to say that humans are smarter than chimps – or any other organism, for that matter – has no basis in fact when viewed holistically.

Intelligence, after all, is in the application. There is a lot to be said for contentment with enough to eat, a comfortable place to sleep, and the company of amiable companions. Nothing better typifies the good life better than bonobos.


Of the apes the bonobo is genetically most similar to humans: 98.7% DNA sequence similarity, slightly closer than chimps (by 1.6%). This simplistic measure ignores epigenetic inheritance, which is quite telling in expressed traits. Besides, genetics altogether provides a grossly incomplete accounting of the ledger of life.

Chimpanzees and bonobos split evolutionarily 2.1–1.5 million years ago, though there has been some interbreeding since. The major distinctions between the two are behavioral. Bonobos live only in central Zaire, south of the Zaire River.

Chimpanzees are more patient and more risk-prone than are bonobos. ~ Alexandra Rosati & Brian Hare

Bonobos are the smallest ape. They have longer legs, shorter arms, and a narrower torso than chimpanzees.

There is modest sexual dimorphism in bonobos. The typical female weights 31 kg versus 39 kg for males. Either sex may be 70–119 cm. In comparison, adult male chimps average 50 kg; females 35 kg. The largest bonobos are about the same size as smaller chimpanzees.

Unlike chimpanzees, bonobos are relaxed about life. Put it down to sex; lots of it.

Bonobos are positively randy. Sex works as a show of affection, an act of appeasement, a stress reducer, or just a good time. Orgasm is seldom involved. Homosexuality, both male & female, is as everyday as heterosexuality. Bonobos enjoy a variety of positions and creative sex play. Genitals are for enjoyment.

The chimpanzee resolves sexual issues with power; the bonobo resolves power issues with sex. ~ Frans de Waal

Bonobos are happy-go-lucky compared to their aggressive and uptight chimp cousins, or practically any other primate. One consequence is that bonobos stay young longer than chimps or humans (relative to life span).

The excitement of finding a new food source can easily incite an orgy among bonobos. The only taboo is a mother not getting it on with an adult son.

The biological backdrop to bonobo promiscuity is that females are more sexually receptive than chimps. Young nulliparous females are continuously in estrus and have the highest copulation rates. In comparison, adolescent chimp females show less regular genital swelling.

Bonobo females are receptive to sex for much longer than chimps when pregnant: up to 20 days before giving birth. Further, bonobos return to sexual activity within a year after parturition, compared to 3.0–5.5 years for chimpanzees.

That greatly reduces the importance to the males of competing for dominance and bullying the females. ~ English primatologist Richard Wrangham

Another comparative factor regards social mores. Adolescent female chimps rarely mate with adult males. In contrast, an adolescent female bonobo happily lets an adult male have at her. Not surprisingly, adult male bonobos actively solicit young females.

As paternity is an open issue with bonobos, a mother rears her child without male assistance. Bonobos are not weaned until they are 4–5 years old.

A young female begins distancing herself from mom around 6–7 years old. A female youngster eventually emigrates from her natal group. The mother-daughter bond is severed.

Male bonobos remain socially close to their mother throughout their lives. A mother’s rank within her group determines her son’s rank when he attains adulthood.

Bonobos live in close-knit communities. Unlike chimp and human groups, bonobos do not war with their neighbors.

One reason for such peaceability is diet. Bonobos eat a lot of herby vegetation which is abundant year-round. With an inexhaustible food supply, bonobos don’t experience competition for food as chimpanzees do.

Bonobos are exceedingly gregarious, with dominance hierarchies, alliances, coalitions, and politics. Females, not males, hold the highest social rankings, which they achieve via social networking.

Bonobos prefer to share with strangers. They’re trying to extend their social network. ~ Brian Hare

Humans are apt to share anonymously if the amount asked is meager to their wealth, given information that they can help someone in need. This coincides with human inclination toward dissonance in cognitive sympathy: a propensity to abstraction, even with emotions, thereby being able to rationalize either compassion or selfishness.

Such conceptualization does not intrude into the empathies of apes. Chimps have all the empathic inclination of capitalists. In contrast, bonobos consider sharing at a personal level, with an eye to ongoing comity.

Bonobos pay most attention to behaviours that promote social cohesion. Bonobos are amazingly good at this: they avoid conflicts or resolve them immediately. ~ Dutch cognitive psychologist Mariska Kret

Bonobos are highly tolerant and are capable of having affiliative interactions with strangers. They care about others. They’ll share when it’s a low-cost / low-benefit kind of situation. But when it’s a no-benefit situation, they won’t share. ~ Brian Hare

For bonobos, sensitivity to the emotions of others emerges early and does not require advanced thought processes that develop only in adults. Bonobos are more likely to comfort those they are emotionally close to. Empathy and emotional sensitivity contribute to consolation behavior. ~ American primatologist Zanna Clay

Bonobos are innately empathic. Adolescents readily comfort younger and less emotionally competent peers.

To spontaneously provide consolation is thought to require some level of other-awareness or emotional perspective-taking, which allows the bystander to both recognize the emotional state of the victim and to provide the appropriate response to reduce distress. Being able to experience another individual’s emotions, while separating them from one’s own, is considered a more cognitively demanding form of empathy, known as sympathetic concern. ~ Zanna Clay & Frans de Waal

High-ranking male bonobos are more assertive, and their mating success higher, than lower-ranking males. Male bonobos succeed not by aggression, but by social engagement: high-ranking males invest more in friendships with females.

Female social dominance over males is rare among mammal species. By contrast to chimpanzees, bonobos are especially striking in this regard. Female bonobos play a more dominant social role than any other ape. Because of this, bonobos are relatively peaceful primates; a lesson humans have been unable to learn.

Female bonobos to do not dominate or win conflicts because of their alliance. It’s in their looks. The more sexually attractive a female, the more likely she can persuade a male to be less aggressive and give way. Charm and allure have a winning way with bonobos.

Bonobos are mostly drawn toward protective and affiliative emotions. ~ Mariska Kret