The Web of Life (116-3) Chimpanzees

Chimpanzees

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.

 Diet

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.

 Communication

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.

 Parenting

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.

 Sociality

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.

 Culture

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

 Intelligence

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.

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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.

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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.