Chimpanzee

The chimpanzee (; Pan troglodytes), also simply known as the chimp, is a medium-sized great ape species found in the forests and savannas of equatorial Africa. It has four confirmed subspecies and a fifth proposed one. When its close relative, the bonobo, was more commonly known as the pygmy chimpanzee, this species was often called the common chimpanzee or the robust chimpanzee. The chimpanzee and the bonobo are the only species in the genus Pan. Evidence from fossils and DNA sequencing shows that the two species are humans' closest living relatives. The chimpanzee is covered in coarse black hair but has a bare face, fingers, toes, palms of the hands, and soles of the feet. It is larger and more robust than the bonobo. The species lives in groups that range in size from 15 to 150 members, although individuals travel and forage in much smaller groups during the day. The species lives in a strict male-dominated hierarchy, where disputes are generally settled without the need for violence. Nearly all chimpanzee populations have been recorded using tools, modifying sticks, rocks, grass and leaves and using them for hunting and acquiring honey, termites, ants, nuts and water. The species has also been found creating sharpened sticks to spear small mammals. Its gestation period is eight months. The infant is weaned at about three years old but usually maintains a close relationship with its mother for several years more. The chimpanzee is listed on the IUCN Red List as an endangered species. Between 170,000 and 300,000 individuals are estimated across its range. The biggest threats to the chimpanzee are habitat loss, poaching, and disease. Chimpanzees appear in Western popular culture as stereotyped clown-figures and have featured in entertainments such as chimpanzees' tea parties, circus acts and stage shows. Although chimpanzees have been kept as pets, their strength, aggressiveness, and unpredictability makes them dangerous in this role. Some hundreds have been kept in laboratories for research, especially in the United States. Many experimental attempts have been made to attempt teaching languages such as American Sign Language to chimpanzees, which have been challenged by academics such as Noam Chomsky. Etymology The first use of the name chimpanze is recorded in The London Magazine in 1738, glossed as meaning "mockman" in a language of "the Angolans" (reportedly modern Vili, a Kongo language of the coast, has the comparable ci-mpenzi). The spelling chimpanzee is found in a 1758 supplement to Chamber's Cyclopædia. The colloquialism "chimp" was most likely coined some time in the late 1870s. The genus name Pan derives from the Greek god, while the specific name troglodytes was taken from the Troglodytae, a mythical race of cave-dwellers; it had first been proposed for the genus but a genus of wren took priority. Taxonomy Both chimpanzees and bonobos are part of the Hominidae, or, hominids, whose members are known as the great apes, a taxonomic family of primates that includes eight extant species in four genera: Pongo (the Bornean, Sumatran and Tapanuli orangutan); Gorilla (the eastern and western gorilla); Pan (the chimpanzee and the bonobo); and Homo, of which only modern humans (Homo sapiens) remain. The first great ape known to Western science in the 17th century was the "orang-outang" (genus Pongo), the local Malay name being recorded in Java by the Dutch physician Jacobus Bontius. In 1641, the Dutch anatomist Nicolaes Tulp applied the name to a chimpanzee or bonobo brought to the Netherlands from Angola. Another Dutch anatomist, Peter Camper, dissected specimens from Central Africa and Southeast Asia in the 1770s, noting the differences between the African and Asian apes. The German naturalist Johann Friedrich Blumenbach classified the chimpanzee as Simia troglodytes by 1775. Another German naturalist, Lorenz Oken, coined the genus Pan in 1816. The bonobo was recognised as distinct from the chimpanzee in 1933. Evolution Despite a large number of Homo fossil finds, Pan fossils were not described until 2005. Existing chimpanzee populations in West and Central Africa do not overlap with the major human fossil sites in East Africa, but chimpanzee fossils have now been reported from Kenya. This indicates that both humans and members of the Pan clade were present in the East African Rift Valley during the Middle Pleistocene. Evolutionary biologists and paleontologists have attempted to reconstruct the last common ancestor of Homo and Pan (CHLCA). By the end of the 20th century, it was assumed that humans evolved from a chimpanzee-like ancestor. A 2015 study of Ardipithecus, an early human relative dated 4.4 mya, disputed this interpretation. The study concluded that humans, chimpanzees and bonobos evolved from a generalised species that lacked the derived traits of both genera. Subsequent studies disputed this, finding that the hand of Ardipithecus was adapted for suspension climbing and the heel for vertical climbing, much like modern African apes. Anthropologist Alice Roberts indicates that at least 24 species of hominin have appeared after the divergence of humans from chimpanzees estimated at 10 to 7 million years ago. When describing the extinct species Sahelanthropus in 2002, Brunet and colleagues noted the combination of ancient features not expressed in chimpanzees that would be considered archaic or derived for a species on the human line (the subtribe Hominina). These latter ancient features being bipedal locomotion and reduced canine teeth, which they interpreted as evidence of its position near the CHLCA. For example, in addition to the study of Ardipithecus in studying traits expressed and not expressed in chimpanzees, researchers such as M. Burnet have examined Sahelanthropus, the oldest Hominina, shifting the centre of origin for the clade away from East Africa and CHLCA origins. They also suggested that Sahelanthropus could be a sister group to the 5.5-to-4.5-million-year-old Ardipithecus and later Hominina after the separation from the chimpanzee line. According to studies published in 2017 by researchers at George Washington University, bonobos, along with chimpanzees, split from the human line about 8 million years ago; then bonobos split from the common chimpanzee line about 2 million years ago. Another 2017 genetic study suggests ancient gene flow (introgression) between 200,000 and 550,000 years ago from the bonobo into the ancestors of central and eastern chimpanzees. Subspecies and population status Four subspecies of the chimpanzee have been recognised, with the possibility of a fifth: Central chimpanzee or the tschego (Pan troglodytes troglodytes), found in Cameroon, the Central African Republic, Equatorial Guinea, Gabon, the Republic of the Congo, and the Democratic Republic of the Congo, with about 140,000 individuals existing in the wild. Western chimpanzee (P. troglodytes verus), found in Ivory Coast, Guinea, Liberia, Mali, Sierra Leone, Guinea-Bissau, Senegal, and Ghana with about 52,800 individuals still in existence. Nigeria-Cameroon chimpanzee (P. troglodytes ellioti (also known as P. t. vellerosus)), that live within forested areas across Nigeria and Cameroon, with 6,000–9,000 individuals still in existence. Eastern chimpanzee (P. troglodytes schweinfurthii), found in the Central African Republic, South Sudan, the Democratic Republic of the Congo, Uganda, Rwanda, Burundi, Tanzania, and Zambia, with approximately 180,000–256,000 individuals still existing in the wild. Southeastern chimpanzee, P. troglodytes marungensis, in Burundi, Rwanda, Tanzania, and Uganda. Colin Groves argues that this is a subspecies, created by enough variation between the northern and southern populations of P. t. schweinfurthii, but it is not recognised by the IUCN. A 2013 genetic study which used samples from the four recognised subspecies found that they can be divided into two branches or clades, the Nigeria-Cameroon and Western chimpanzee forming one clade and the Central and Eastern subspecies belong to the other. Genome A draft of the chimpanzee genome was first published in 2005 and found that almost 99% of the species DNA sequences were shared with humans, along with roughly 30% of proteins. They differ in the number of chromosome pairs, with chimpanzees having 24 and humans 23; this is due to a fusion in two chromosomes during human evolution, producing human chromosome 2. A 2006 study concluded that around 6% of the genes in chimpanzees and humans differ due to gene duplications, insertions, and deletions, contributing to major genetic differences between the two species. In addition, a 2012 study comparing brain tissue found that chimpanzees and humans diverged significantly in the activating and de-activating of genes. A more complete chimpanzee genome was published in 2025. The paper concluded that while chimpanzee and human DNA differ by only 1.2% in one-to-one genetic code sequences, when looking at entire DNA strands—including insertions, deletions and non-coding material—additional 12.5% to 13.3% differences were found. These differences are primarily in genes related to the brain, immune system and aging. Characteristics Adult chimpanzees have an average standing height of 150 cm (4 ft 11 in). In the wild, males weigh an average of around 40 kg (88 lb) while female weigh an average of around 30 kg (66 lb). In exceptional cases, certain individuals may considerably exceed these measurements, standing over 168 cm (5 ft 6 in) on two legs and weighing up to 136 kg (300 lb) in captivity. The chimpanzee is more robust than the bonobo but less than the gorilla. It has longer arms than legs and can reach below the knees. The elongated hands have long fingers with short thumbs and flat fingernails. The big toe is opposable, allowing the ape to grasp with its feet. The body or thorax is short but wide, while the hips are long with a wide top. A chimpanzee's head is rounded with a forward-projecting jaw and a pronounced brow ridge. It has forward-facing eyes, a small nose, circulator non-lobed ears and a long flexible upper lip. Like all great apes, it has two incisors, one canine, two premolars, and three molars on both halves of each jaw. The canine teeth of males are sharp. Chimpanzees lack the prominent sagittal crest and associated head and neck musculature of gorillas. Chimpanzee bodies are covered by coarse hair, except for the face, ears, fingers, toes, palms of the hands, and soles of the feet. Chimpanzees lose more hair as they age and develop bald spots. While normally black, chimpanzee hair can also be shades of brown or ginger. As they get older, white or grey patches may appear, particularly on the chin and lower region. The skin underneath the hair is white, while exposed areas vary between white and dark depending on the subspecies and can include mottled patterns. The skin can become darker with age and female skin gets pinker when in oestrus. Like bonobos, male chimpanzees have a long slender penis with a small bone, but no glans. Chimpanzees are adapted for both arboreal (trees) and terrestrial (ground) locomotion. Arboreal locomotion consists of vertical climbing and swinging with the arms. On the ground, chimpanzees move both bipedally (upright) and quadrupedally (on all four limbs); which differ little in energy costs. As with bonobos and gorillas, chimpanzees move quadrupedally by knuckle-walking, which probably evolved independently in Pan and Gorilla. Their muscles are 50% stronger per weight than those of humans due to higher content of fast twitch muscle fibres, one of the chimpanzee's adaptations for climbing and swinging. The chimpanzee brain is around 66% smaller than that of a human's while the skull has an average endocranial volume of 400 cm3 compared to 1,201 cm3 for humans. The brains also show differences in neuron connectivity that are independent of size. While chimpanzees and humans have the same basic wiring, those of the former are more attuned for quick and direct action, while the latter are more adapted for higher cognition. The chimpanzee brain contains equivalents of both Broca's area and Wernicke's area, regions which process language in humans. Ecology The chimpanzee can adapt to a variety of habitats, including dry savanna, evergreen rainforest, montane forest, swamp forest, and dry woodland-savanna mosaic. In Gombe, the chimpanzee mostly uses semideciduous and evergreen forest as well as open woodland. At Bossou, they live at the intersection of forests, savannas and cultivated areas. Chimpanzees are active during the day, spending much of their time feeding and traveling in their home range. They can repeatedly find food within their range due to advanced cognitive maps. The apes eat for around two hours after they wake in the morning while midday is spent traveling and resting. After more foraging later in the afternoon, they begin to build nests in trees for the night. Each evening, the chimpanzee constructs a sleeping nest in a tree, never in the same location and never using the same nest more than once. Chimpanzees sleep alone in separate nests, with the exception of infants and juvenile chimpanzees, which sleep with their mothers. Chimpanzees do not appear to directly compete with gorillas in areas where they overlap. At Lopé National Park, gorillas and chimpanzees both will consume fruit when it is abundant, but when it is scarce gorillas eat more vegetation while chimpanzees continue to consume fruit. In addition, gorillas are not as adept at using tools to feed on insects as chimpanzees. The two apes may also feed on different species, whether fruit or insects. Interactions between them can range from friendly and even stable social bonding, to avoidance, to aggression and even predation of infants on the part of chimpanzees. Diet The chimpanzee primarily eats fruit, but also consumes leaves, seeds, blossoms, stems, pith, bark, and resin. A study in Budongo Forest, Uganda concentrate the majority of their feeding time (64.5%) on fruits (84.6% of which being ripe), particularly those from two species of Ficus, Maesopsis eminii, and Celtis gomphophylla. In addition, 19% of feeding time was spent on arboreal leaves, mostly Broussonetia papyrifera and Celtis mildbraedii. The consummation of woody material like bark appears to have a supplemental or medicinal function rather than just an alternative food source during scarcity. In savanna habitats, chimpanzees have adapted to eating seeds and unripe fruits. While the chimpanzee is mostly herbivorous, it does eat honey, soil, insects, birds and their eggs, and small to medium-sized mammals, including other primates. Insect species consumed include the weaver ant species Oecophylla longinoda, termites of the genus Macrotermes, and honey bees. Mammal prey include monkeys like the Western red colobus, the king colobus and baboons, non-simian primates like galagos, rodents like squirrels and hooved mammals like bushpigs, blue duikers, sunis and bushbuck fawns. The red colobus is the most common prey, though Jane Goodall documented many occasions within Gombe Stream National Park of chimpanzees and western red colobus monkeys ignoring each other despite close proximity. Meat makes up a small portion of their diet, and does not appear to be a high-quality food source since females—who need the energy they can get when pregnant and nursing young—eat far less of it than males. Nevertheless, it is suggested to have some importance in providing nutrients that help in brain development. Chimpanzees are more likely to hunt when fruit is more abundant, since more individuals aggregate during this time and hunting requires large groups. Mortality and health A 2017 study of the Ngogo community in Kibale National Park found that, when environmental conditions are favourable, chimpanzees have an average life expectancy of nearly 33 years, which is within the expectancy of human hunter gatherers (27–37 years). By contrast, the Kanyawara chimpanzees, which also live in Kibale, have an average life expectancy of 20 years. The life expectancy of chimpanzees at Gombe and Taï average 18 and 13 years respectively. Wild chimpanzees can possibly live for over 60 years. The oldest-known male captive chimpanzee to have been documented lived to 66 years, and the oldest female, Little Mama, was nearly 80 years old. Leopards prey on chimpanzees in some areas. It is possible that some mortality caused by leopards can be attributed to individuals that have specialised in killing chimpanzees. Chimpanzees may react to a leopard's presence with loud vocalising, vegetation shaking, throwing objects and climbing up trees. There is at least one record of chimpanzees killing a leopard cub after harassing it and its mother in their den. Four chimpanzees could have fallen prey to lions at Mahale Mountains National Park. Although no other instances of lion predation on chimpanzees have been recorded, lions likely do kill chimpanzees occasionally, and the larger group sizes of savanna chimpanzees may have developed as a response to threats from these big cats. Chimpanzees may react to lions by fleeing up trees, vocalising, or hiding in silence. Less than half the parasite and microbe species that infest chimpanzees also infest humans, who show much more overlap with omnivorous, savanna-dwelling baboons. The chimpanzee is host to the louse species Pediculus schaeffi, a close relative of P. humanus, which lives in human head and body hair. By contrast, the human pubic louse Pthirus pubis is closely related to Pthirus gorillae, which infests gorillas. The mite species Sarcoptes scabiei may infest chimpanzee and cause mange. A 2023 study of chimpanzees in Kibale identified seven species of ticks as parasites, the most numerous being the species Haemaphysalis parmata. A 2017 study of gastrointestinal parasites of wild chimpanzees in degraded forest in Uganda found nine species of protozoa, five nematodes, one cestode, and one trematode. The most prevalent species was the protozoan Troglodytella abrassarti. A study found that chimpanzee nests contain fewer skin bacteria and external parasites, but higher microbial diversity from the surrounding environment, compared to human beds. Behaviour Behaviour of chimpanzees has been studied from multiple perspectives including their group structure, their mating preferences, their parenting capacities, the limits of their communication abilities, their hunting abilities and their ritual behaviour. Group structure Chimpanzees live in communities that typically range from around 15 to more than 150 members but spend most of their time traveling in small, temporary groups consisting of a few individuals. These groups may consist of any combination of age and sexes. Both males and females sometimes travel alone. This fission–fusion society may include groups of four types: all-male, adult females and offspring, adults of both sexes, or one female and her offspring. These smaller groups emerge in a variety of types, for a variety of purposes. For example, an all-male troop may be organised to hunt for meat, while a group consisting of lactating females serves to act as a "nursery group" for the young. At the core of social structures are males, which patrol the territory, protect group members, and search for food. Males remain in their natal communities, while females generally emigrate at adolescence. Males in a community are more likely to be related to one another than females are to each other. Among males, there is generally a dominance hierarchy, and males are dominant over females. There is great individual autonomy within these communities. As a result, individual chimpanzees often forage for food alone, or in smaller groups. Male chimpanzees exist in a linear dominance hierarchy. Top-ranking males tend to be aggressive even during dominance stability. This is probably due to the chimpanzee's fission-fusion society, with male chimpanzees leaving groups and returning after extended periods of time. With this, a dominant male is unsure if any changes have occurred in his absence and must re-establish his dominance. Thus, a large amount of aggression occurs within five to fifteen minutes after a reunion. During these encounters, displays of aggression are generally preferred over physical attacks. Males maintain and improve their social ranks by forming coalitions, which have been characterised as "exploitative" and based on an individual's influence in agonistic interactions. Being in a coalition allows males to dominate a third individual when they could not by themselves, as politically apt chimpanzees can exert power over aggressive interactions regardless of their rank. Coalitions can also give an individual male the confidence to challenge a dominant or larger male. The more allies a male has, the better his chance of becoming dominant. However, most changes in hierarchical rank are caused by one-on-one interactions. Chimpanzee alliances can be very fickle, and one member may suddenly turn on another if it is to his advantage. Low-ranking males frequently switch sides in disputes between more dominant individuals. Low-ranking males benefit from an unstable hierarchy and often find increased sexual opportunities if a dispute or conflict occurs. In addition, conflicts between dominant males cause them to focus on each other rather than the lower-ranking males. Social hierarchies among adult females tend to be weaker. Nevertheless, the status of an adult female may be important for her offspring. Females in Taï have also been recorded to form alliances. While chimpanzee social structure is often referred to as patriarchal, it is not entirely unheard of for females to forge coalitions against males. There is also at least one recorded case of females securing a dominant position over males in their respective troop, albeit in a captive environment. Social grooming appears to be important in the formation and maintenance of coalitions. It is more common among adult males than either between adult females or between males and females. Coalitions of adult males chimpanzees will patrol the boundaries of their home range. Patrols from smaller groups are more likely to avoid contact with their neighbours. Patrols from large groups even take over a smaller group's territory, gaining access to more resources, food, and females. While it was traditionally accepted that only female chimpanzees immigrate and males remain in their natal troop for life, there are confirmed cases of adult males safely integrating themselves into new communities among West African chimpanzees, suggesting they are less territorial than other subspecies. West African chimpanzee males are also less aggressive with female chimpanzees in general. Unusual among animals, but similar to humans, chimpanzees within a community can become more polarized and eventually split into two groups, with one group attacking and raiding the other. The Gombe Chimpanzee War was one such conflict were a prolonged dominance struggle between two males in a community eventually created separate factions. This was followed by a four year conflict (1974–1977) where one group attacked the other leading to the deaths or disappearances of members of the victim group. While chimpanzees are popularly thought of as more war-like than bonobos, primatologist Christine Webb concludes that "Through an analysis of various chimpanzee and bonobo sanctuary communities, we've found that variation within the two species is greater than differences between them". While intra-group rivalry among male chimpanzees to determine alpha-status for mating has been observed within groups, research published in April 2026 in Science has extended these observations to state that such rivalry between intra-group subgroups of chimpanzees battling against each other for dominance within the group was also possible. Mating and parenting Chimpanzees mate throughout the year, although the number of females in oestrus varies seasonally in a group. Female chimpanzees are more likely to come into oestrus when food is readily available. Oestrous females exhibit sexual swellings. Chimpanzees are promiscuous; during oestrus, females mate with several males in their community, while males have large testicles for sperm competition. Other forms of mating also exist. A community's dominant males sometimes restrict reproductive access to females. A male and female can form a consortship and mate outside their community. In addition, females sometimes leave their community and mate with males from neighboring communities. These alternative mating strategies give females more mating opportunities without losing the support of the males in their community. Infanticide has been recorded in chimpanzee communities in some areas, and the victims are often consumed. Male chimpanzees practice infanticide on unrelated young to shorten the interbirth intervals in the females. Females sometimes practice infanticide. This may be related to the dominance hierarchy in females or may simply be pathological. Inbreeding was studied in a relatively undisturbed eastern chimpanzee community that displayed substantial bisexual philopatry. Despite an increased inbreeding risk incurred by females who do not disperse before reaching reproductive age, these females were still able to avoid producing inbred offspring. Copulation is brief, lasting approximately seven seconds. The gestation period is eight months. Care for the young is provided mostly by their mothers. The survival and emotional health of the young is dependent on maternal care. Mothers provide their young with food, warmth, and protection, and teach them certain skills. In addition, a chimpanzee's future rank may be dependent on its mother's status. Male chimpanzees continue to associate with the females they impregnated and interact with and support their offspring. Orphaned chimpanzees are occasionally adopted by adult males who will be "as protective as any mother" and tend to their needs. Newborn chimpanzees are helpless. For example, their grasping reflex is not strong enough to support them for more than a few seconds. For their first 30 days, infants cling to their mother's bellies. Infants are unable to support their own weight for their first two months and need their mothers' support. Wild chimps are seen to exhibit both "secure" and "insecure" attachment styles, with the offspring looking to the mother for comfort in the former and more independent offspring in the latter. However, wild chimps rarely demonstrate "disorganised" attachment styles (maladaptive parent-offspring bonds caused by abuse or neglect); researchers note such attachment styles are mostly observed in captive chimps raised around humans. When they reach five to six months, infants ride on their mothers' backs. They remain in continual contact for the rest of their first year. When they reach two years of age, they are able to move and sit independently and start moving beyond the arms' reach of their mothers. By four to six years, chimpanzees are weaned and infancy ends. The juvenile period for chimpanzees lasts from their sixth to ninth years. Juveniles remain close to their mothers but increasingly begin to interact with other members of their community. Adolescent females move between groups and are supported by their mothers in agonistic encounters. Adolescent males spend time with adult males in social activities like hunting and patrolling the boundaries of their territory. A captive study suggests males can safely immigrate to a new group if accompanied by immigrant females who have an existing relationship with this male. This gives the resident males reproductive advantages with these females, as they are more inclined to remain in the group if their male friend is also accepted. Communication Chimpanzees use facial expressions, postures, and sounds to communicate with each other. They have expressive faces that are important in close-up communications. When frightened, a "full closed grin" causes nearby individuals to be fearful, as well. Playful chimpanzees display an open-mouthed "smile". Chimpanzees may also express themselves with the "pout", which is made in distress, the "sneer", which is made when threatening or fearful, and "compressed-lips face", which is a type of display. When submitting to a dominant individual, a chimpanzee crunches, bobs, and reaches its hand out When in an aggressive mode, a chimpanzee swaggers bipedally, hunched over and arms waving, in an attempt to exaggerate its size. Chimpanze beat their hands and feet against the trunks of large trees, an act that is known as "drumming". They also do this when traveling, displaying, begging and when they see individuals from other communities. Vocalisations are also important in chimpanzee communication. The most common call in adults is the "pant-hoot", which can be made in numerous contexts including meetings, feedings and travellings. Pant-hoots are made of four parts, starting with soft "hoos", the introduction; that gets louder and louder, the build-up; and climax into screams and sometimes barks; these die down back to soft "hoos" during the letdown phase as the call ends. Grunting is made in situations like feeding and greeting. Submissive individuals make "pant-grunts" towards their superiors. Whimpering is made by young chimpanzees as a form of begging or when lost from the group. Chimpanzees use distance calls to draw attention to danger, food sources, or other community members. "Barks" come in two forms: "short barks" which are made during hunts and "tonal barks" which are a reaction to large snakes. Hunting Chimpanzees hunt tree-dwelling monkeys in groups or alone. At Taï, members of a hunting group assume different roles. "Drivers" will herd prey into a certain direction without actually catching them. "Blockers" are stationed at the bottom of the trees and climb up to block prey that takes off in a different direction. "Chasers" will pursue and isolate a monkey while trying to catch it. Finally, "ambushers" hide and rush out when a monkey nears. At Gombe, chimpanzees may hunt alone, selecting areas with less continuous tree canopies where they can more easily corner their prey. While both adults and infants are taken, adult male colobus monkeys will attack the hunting chimps. When caught and killed, the meal is distributed to all hunting party members and even bystanders. Male chimpanzees hunt in groups more than females. Female chimpanzees tend to hunt solitarily. If a female chimpanzee were to participate in the hunting group and catch a red colobus, it would likely immediately be taken by an adult male. Female chimpanzees are estimated to hunt around 10-15% of a community's vertebrates. Intelligence Chimpanzees display numerous signs of intelligence, from the ability to remember symbols, to cooperation, and to tool use. They are among species that have passed the mirror test, suggesting self-awareness. In one study, two young chimpanzees showed retention of mirror self-recognition after one year without access to mirrors. Chimpanzees also display signs of culture among groups, with the learning and transmission of variations in grooming, tool use and foraging techniques leading to local traditions. A 30-year study at Kyoto University's Primate Research Institute has shown that chimpanzees are able to learn to recognise the numbers 1 to 9 and their values. The chimpanzees further show an aptitude for eidetic memory, demonstrated in experiments in which the jumbled digits are flashed onto a computer screen for less than a quarter of a second. One chimpanzee, Ayumu, was able to correctly and quickly point to the positions where they appeared in ascending order. Ayumu performed better than human adults who were given the same test. In controlled experiments on cooperation, chimpanzees show a basic understanding of cooperation, and recruit the best collaborators. In a group setting with a device that delivered food rewards only to cooperating chimpanzees, cooperation first increased, then, due to competitive behaviour, decreased, before finally increasing to the highest level through punishment and other arbitrage behaviour. Great apes show laughter-like vocalisations in response to physical contact, such as wrestling, play chasing, or tickling. This is documented in wild and captive chimpanzees. Chimpanzee laughter is not readily recognisable to humans as such, because it is generated by alternating inhalations and exhalations that sound more like breathing and panting. Instances in which nonhuman primates have expressed joy have been reported. Humans and chimpanzees share similar ticklish areas of the body, such as the armpits and belly. The enjoyment of tickling in chimpanzees does not diminish with age. Further study of the discussion of which intelligence traits are genetically inherited in chimpanzees as opposed to those traits which are developmentally acquired by cooperation were examined in a 2026 study suggesting that broader attention might be justified for studying traits acquired developmentally. The study concludes that the acquisition of a broad range of both overt and subtle developmental traits are related to the age of the chimpanzees observed. A 2022 study reported that chimpanzees crushed and applied insects to their own wounds and the wounds of other chimpanzees. Chimpanzees display different behaviour in response to a dying or dead group member. When a chimpanzee dies an unnatural death (like a tree fall or predator attack), the other group members may act in frenzy, including vocalisations, aggressive displays, and touching of the corpse. In one case chimpanzees cared for a dying elder, and then attended and cleaned the corpse. Afterward, they avoided the spot where the elder had died, and behaved in a more subdued manner. Mothers have been reported to carry around and groom their dead infants for several days. Experimenters now and then witness behaviour that, in the absence of human-like language skills, cannot be readily reconciled with chimpanzee intelligence or theory of mind. For example, Wolfgang Köhler reported insightful behaviour in chimpanzees, but he likewise often observed that they experienced "special difficulty" in solving simple problems. Researchers also reported that, when faced with a choice between two persons, chimpanzees were just as likely to beg food from a person who could see the begging gesture as from a person who could not, thereby raising the possibility that chimpanzees lack theory of mind. By contrast, Hare, Call, and Tomasello found that subordinate chimpanzees were able to use the knowledge state of dominant rival chimpanzees to determine which container of hidden food they approached. Tool use Nearly all chimpanzee populations have been recorded using tools. They modify sticks, rocks, grass, and leaves and use them when foraging for termites and ants, nuts, honey, algae or water. Despite their rudimentary and simple quality, forethought and skill are apparent in making these tools. Chimpanzees have used stone tools since at least 4,300 years ago. A chimpanzee from the Kasakela chimpanzee community was the first nonhuman animal reported making a tool, by modifying a twig to use as an instrument for extracting termites from their mound. At Taï, chimpanzees simply use their hands to extract termites. When foraging for honey, chimpanzees use modified short sticks to scoop the honey out of the hive if the bees are stingless. For hives of the dangerous African honeybees, chimpanzees use longer and thinner sticks to extract the honey. Chimpanzees also fish for ants using the same tactic. Ant dipping is difficult and some chimpanzees never master it. West African chimpanzees crack open hard nuts with stones or branches. Some forethought in this activity is apparent, as these tools are not found together or where the nuts are collected. Nut cracking is also difficult and must be learned. Chimpanzees also use leaves as sponges or spoons to drink water. West African chimpanzees in Senegal were found to sharpen sticks with their teeth, which were then used to spear Senegal bushbabies out of small holes in trees. An eastern chimpanzee has been observed using a modified branch as a tool to capture a squirrel. Chimpanzees living in Tanzania were found to deliberately choose plants that provide materials that produce more flexible tools for termite fishing. In 2020, experimental studies on captive chimpanzees have found that many of their species-typical tool-use behaviour can be individually learnt by individual chimpanzees. However, in comparing hypothesized early hominid making and use of stone flakes, a 2021 study on chimpanzee abilities to make and use stone flakes did not find this behaviour across two populations of chimpanzees—suggesting that this behaviour is outside the chimpanzee species-typical range. Speech and language Scientists have attempted to teach human language to several species of great ape. One early attempt by Allen and Beatrix Gardner in the 1960s involved spending 51 months teaching American Sign Language to a chimpanzee named Washoe. The Gardners reported that Washoe learned 151 signs, and had spontaneously taught them to other chimpanzees, including her adopted son, Loulis. Over a longer period of time, Washoe was reported to have learned over 350 signs. Debate is ongoing among scientists such as David Premack about chimpanzees' ability to learn language. Since the early reports on Washoe, numerous other studies have been conducted, with varying levels of success. One involved a chimpanzee jokingly named Nim Chimpsky (in allusion to the theorist of language Noam Chomsky), trained by Herbert Terrace of Columbia University. Although his initial reports were quite positive, in November 1979, Terrace and his team, including psycholinguist Thomas Bever, re-evaluated the videotapes of Nim with his trainers, analyzing them frame by frame for signs, as well as for exact context (what was happening both before and after Nim's signs). In the reanalysis, Terrace and Bever concluded that Nim's utterances could be explained merely as prompting on the part of the experimenters, as well as mistakes in reporting the data. "Much of the apes' behaviour is pure drill", he said. "Language still stands as an important definition of the human species". In this reversal, Terrace now argued Nim's use of ASL was not like human language acquisition. Nim never initiated conversations himself, rarely introduced new words, and mostly imitated what the humans did. More importantly, Nim's word strings varied in their ordering, suggesting that he was incapable of syntax. Nim's sentences also did not grow in length, unlike human children whose vocabulary and sentence length show a strong positive correlation. Chomsky has voiced opposition to the viewpoint of Terrace and Bever based upon his theory of the inheritance of language capacity as being limited to human inheritance alone among all animals. Human relations In culture and entertainment The Gio people of Liberia and the Hemba people of the Congo make chimpanzee masks. Gio masks are relatively primitive, and worn when warning young people about bad behaviours. The Hemba masks have a smile perceived as disturbing, and are worn at funerals to represent the "awful reality of death". The masks may also decorate homes for protection and promote fertility, for both humans and plants. Stories have been told of chimpanzees kidnapping and raping women. In Western popular culture, chimpanzees have occasionally been stereotyped as childlike companions, sidekicks or clowns. They are especially suited for the latter role on account of their prominent facial features, long limbs and fast movements, which humans often find amusing. Chimpanzees in media include Judy on the television series Daktari in the 1960s and Darwin on The Wild Thornberrys in the 1990s. In contrast to the fictional depictions of other animals, such as dogs (as in Lassie), dolphins (Flipper), horses (Black Beauty) or even other great apes (King Kong), chimpanzee characters and actions are rarely relevant to the plot. Depictions of chimpanzees as individuals rather than stock characters, and as central rather than incidental to the plot can be found in science fiction. Robert A. Heinlein's 1947 short story "Jerry Was a Man" concerns a genetically enhanced chimpanzee suing for better treatment. The 1972 film Conquest of the Planet of the Apes, the third sequel of the 1968 film Planet of the Apes, portrays a futuristic revolt of enslaved apes led by the only talking chimpanzee, Caesar, against their human masters. Entertainment acts featuring chimpanzees dressed up as humans with lip-synchronised human voices have been traditional staples of circuses, stage shows and TV shows like Lancelot Link, Secret Chimp (1970–1972) and The Chimp Channel (1999). From 1926 until 1972, London Zoo, followed by several other zoos around the world, held a chimpanzees' tea party daily. Animal rights groups have urged a stop to such acts, considering them abusive. Domestic pets and dangers Chimpanzees have traditionally been kept as pets in a few African villages, especially in the Democratic Republic of Congo. In Virunga National Park in the east of the country, the park authorities regularly seize chimpanzees from people keeping them as pets. Outside their range, chimpanzees are popular as exotic pets despite their strength and aggression. Even in places where keeping non-human primates as pets is illegal, the exotic pet trade continues to prosper, leading to injuries from attacks. Chimpanzees have attacked humans. In Uganda, several attacks on children have happened, some of them fatal. Some of these attacks may have been due to the chimpanzees being intoxicated (from alcohol obtained from rural brewing operations) and becoming aggressive towards humans. Human interactions with chimpanzees may be especially dangerous if the chimpanzees perceive humans as potential rivals. At least six cases of chimpanzees snatching and eating human babies are documented. A chimpanzee's strength and sharp teeth mean that attacks, even on adult humans, can cause severe injuries. This was evident after the attack and near death of former NASCAR driver St. James Davis, who was mauled by two escaped chimpanzees while he and his wife were celebrating the birthday of their former pet chimpanzee. Another example of chimpanzees being aggressive toward humans occurred in 2009 in Stamford, Connecticut, when a 90-kilogram (200 lb), 13-year-old pet chimpanzee named Travis attacked his owner's friend, who lost her hands, eyes, nose, and part of her maxilla from the attack. Use in research Hundreds of chimpanzees have been kept in laboratories for research. Most such laboratories either conduct or make the animals available for invasive research, defined as "inoculation with an infectious agent, surgery or biopsy conducted for the sake of research and not for the sake of the chimpanzee, and/or drug testing". Research chimpanzees tend to be used repeatedly over decades for up to 40 years, unlike the pattern of use of most laboratory animals. Two federally funded American laboratories use chimpanzees: the Yerkes National Primate Research Center at Emory University in Atlanta, Georgia, and the Southwest National Primate Center in San Antonio, Texas. Five hundred chimpanzees have been retired from laboratory use in the US and live in animal sanctuaries in the US or Canada. A five-year moratorium was imposed by the US National Institutes of Health in 1996, because too many chimpanzees had been bred for HIV research, and it has been extended annually since 2001. With the publication of the chimpanzee genome, plans to increase the use of chimpanzees in America were reportedly increasing in 2006, some scientists arguing that the federal moratorium on breeding chimpanzees for research should be lifted. However, in 2007, the NIH made the moratorium permanent. Other researchers argue that chimpanzees either should not be used in research, or should be treated differently, for instance with legal status as persons. Pascal Gagneux, an evolutionary biologist and primate expert at the University of California, San Diego, argues, given chimpanzees' sense of self, tool use, and genetic similarity to human beings, studies using chimpanzees should follow the ethical guidelines used for human subjects unable to give consent. A recent study suggests chimpanzees which are retired from labs exhibit a form of post-traumatic stress disorder. Stuart Zola, director of the Yerkes laboratory, disagrees. He told National Geographic: "I don't think we should make a distinction between our obligation to treat humanely any species, whether it's a rat or a monkey or a chimpanzee. No matter how much we may wish it, chimps are not human." Only one European laboratory, the Biomedical Primate Research Centre in Rijswijk, the Netherlands, used chimpanzees in research. It formerly held 108 chimpanzees among 1,300 non-human primates. The Dutch ministry of science decided to phase out research at the centre from 2001. Trials already under way were however allowed to run their course. Chimpanzees including the female Ai have been studied at the Primate Research Institute of Kyoto University, Japan, formerly directed by Tetsuro Matsuzawa, since 1978. As of 2021, 12 chimpanzees were held at the facility. Two chimpanzees have been sent into outer space as NASA research subjects. Ham, the first great ape in space, was launched in the Mercury-Redstone 2 capsule on 31 January 1961, and survived the suborbital flight. Enos, the third primate to orbit Earth after Soviet cosmonauts Yuri Gagarin and Gherman Titov, flew on Mercury-Atlas 5 on 29 November of the same year. Field study Jane Goodall undertook the first long-term field study of the chimpanzee, begun in Tanzania at Gombe Stream National Park in 1960. Other long-term studies begun in the 1960s include Adriaan Kortlandt's in the eastern Democratic Republic of the Congo and Toshisada Nishida's in Mahale Mountains National Park in Tanzania. Current understanding of the species' typical behaviour and social organisation has been formed largely from Goodall's ongoing 60-year Gombe research study. Goodall researched common chimpanzee social and family life beginning with the Kasakela chimpanzee community in Gombe Stream National Park, Tanzania, in 1960, and documented much original commentary about their experienced emotional life. She found that "it isn't only human beings who have personality, who are capable of rational thought [and] emotions like joy and sorrow". She also observed behaviour often considered human, such as hugs, kisses, pats on the back, and even tickling. Goodall insisted that these gestures are evidence of "the close, supportive, affectionate bonds that develop between family members and other individuals within a community, which can persist throughout a life span of more than 50 years". Human immunodeficiency virus Two primary classes of human immunodeficiency virus (HIV) infect humans: HIV-1 and HIV-2. HIV-1 is the more virulent and easily transmitted, and is the source of the majority of HIV infections throughout the world; HIV-2 occurs mostly in west Africa. Both types originated in west and central Africa, jumping from other primates to humans. HIV-1 has evolved from a simian immunodeficiency virus (SIVcpz) found in the subspecies P. t. troglodytes of southern Cameroon. Kinshasa, in the Democratic Republic of Congo, has the greatest genetic diversity of HIV-1 so far discovered, suggesting the virus has been there longer than anywhere else. HIV-2 crossed species from a different strain of HIV, found in the sooty mangabey monkeys in Guinea-Bissau. The oral polio vaccine AIDS hypothesis (OPV AIDS) is a largely discredited hypothesis which argued the AIDS pandemic originated from live polio vaccines prepared in Common chimpanzee tissue cultures, accidentally contaminated with simian immunodeficiency virus and then administered to up to one million Africans between 1957 and 1960 in experimental mass vaccination campaigns. Originally, a few scientists, notably the evolutionary biologist W. D. Hamilton, thought the hypothesis required serious investigation, but they received little support from the scientific community. In 2003, Hooper published additional statements that he believed supported his hypothesis in an article in the London Review of Books. In his subsequent book, Hooper also stated that Gaston Ninane was involved in using chimpanzee cells to produce vaccine in Congo. Ninane responded to this allegation by stating that he could "categorically deny" ever having tried to make tissue cultures from chimpanzee cells. The people involved in vaccine production and distribution from America state that no vaccine was prepared locally in Congo and that only the CHAT vaccine from America was used. Barbara Cohen, the technician who was responsible for running the American laboratory that produced this vaccine stated: "At no time did I ever receive or work on chimpanzee kidneys, nor to my knowledge cells derived from chimpanzees. I never made, nor do I know of anyone in the lab who made polio vaccine in chimpanzee cells." In 2004, the Origin of Aids, a French TV documentary strongly supportive of the OPV hypothesis, appeared on several television stations around the world. Conservation The chimpanzee is on the IUCN Red List as an endangered species. Chimpanzees are legally protected in most of their range and are found both in and outside national parks. Between 172,700 and 299,700 individuals are thought to be living in the wild, a decrease from about a million chimpanzees in the early 1900s. Chimpanzees are listed in Appendix I of the Convention on International Trade in Endangered Species (CITES), meaning that commercial international trade in wild-sourced specimens is prohibited and all other international trade (including in parts and derivatives) is regulated by the CITES permitting system. The biggest threats to the chimpanzee are habitat destruction, poaching, and disease. Chimpanzee habitats have been limited by deforestation in both West and Central Africa. Road building has caused habitat degradation and fragmentation of chimpanzee populations and may allow poachers more access to areas that had not been seriously affected by humans. Although deforestation rates are low in western Central Africa, selective logging may take place outside national parks. Chimpanzees are a common target for poachers. In Ivory Coast, chimpanzees make up 1–3% of bushmeat sold in urban markets. They are also taken, often illegally, for the pet trade and are hunted for medicinal purposes in some areas. Farmers sometimes kill chimpanzees that threaten their crops; others are unintentionally maimed or killed by snares meant for other animals. Infectious diseases are a main cause of death for chimpanzees. They succumb to many diseases that afflict humans because the two species are so similar. As the human population grows, so does the risk of disease transmission between humans and chimpanzees. The endangered population of the western chimpanzee once spanned from southern Senegal all the way east to the Niger River. Today, the largest populations remaining are found in Guinea, Sierra Leone, and Liberia. The IUCN lists the western chimpanzee as Critically Endangered on the Red List of Threatened Species. There are an estimated 21,300 to 55,600 individuals in the wild. The primary threat to the western chimpanzee is habitat loss, although it is also killed for bushmeat. The topic of the conservation of chimpanzee in general through the use of vaccinations and other protective medical interventions has been taken up by Jane Goodall and others. Craig Stanford's book Planet Without Apes speaks of the importance of covering diseases significantly beyond HIV. In his Chapter 4, he covers Ebola, influenza, pneumonia, tuberculosis, and even the common cold. Transmission from humans is a major issue, such as contaminated refuse from local poor villages, as well as from the human travel population which makes expeditions to watch chimpanzees in their native habitat. This issue goes beyond only HIV. Transmission of Ebola is also linked to chimpanzee diet of apparent appetite for meat from monkeys. Also is related the topic of Goodall and her introducing the use of vaccines to protect and treat vulnerable chimpanzee populations in Gombe. For example, Goodal indicates five chimpanzee epidemics since the mid-twetieth century which could have been mediated with vaccines such as the crippling polio outbreak in 1966 which Goodall witnessed as killing 6 out of 7 of the Gombe chimpanzee population she was observing. Notes References Literature cited Goodall, J. (1986). The Chimpanzees of Gombe: Patterns of Behavior. The Belknap Press of Harvard University Press. ISBN 978-0-674-11649-8. Hunt, Kevin D. (2020). Chimpanzee: Lessons from Our Sister Species. Cambridge University Press. ISBN 978-1-107-11859-1. External links DiscoverChimpanzees.org Chimpanzee Genome resources Primate Info Net Pan troglodytes Factsheets Archived 13 January 2008 at the Wayback Machine U.S. Fish & Wildlife Service Species Profile View the Pan troglodytes genome in Ensembl Genome of Pan troglodytes (version Clint_PTRv2/panTro6), via UCSC Genome Browser Data of the genome of Pan troglodytes, via NCBI Data of the genome assembly of Pan troglodytes Clint_PTRv2/panTro6, via NCBI Human Timeline (Interactive) – Smithsonian, National Museum of Natural History (August 2016).