Chimpanzee

The English word chimpanzee is first recorded in 1738.^[5] It is derived from Vili ci-mpenze^[6] or Tshiluba language chimpenze, with a meaning of "ape".^[7] The colloquialism "chimp" was most likely coined some time in the late 1870s.^[8] 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.^[9][10]

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Vili language

Vili language

Vili (Civili) is one of the Zone H Bantu languages, grouped with the Kongo clade.

Ape

Ape

Apes are a clade of Old World simians native to sub-Saharan Africa and Southeast Asia, which together with its sister group Cercopithecidae form the catarrhine clade, cladistically making them monkeys. Apes do not have tails due to a mutation of the TBXT gene. In traditional and non-scientific use, the term "ape" can include tailless primates taxonomically considered Cercopithecidae, and is thus not equivalent to the scientific taxon Hominoidea. There are two extant branches of the superfamily Hominoidea: the gibbons, or lesser apes; and the hominids, or great apes.The family Hylobatidae, the lesser apes, include four genera and a total of 20 species of gibbon, including the lar gibbon and the siamang, all native to Asia. They are highly arboreal and bipedal on the ground. They have lighter bodies and smaller social groups than great apes. The family Hominidae (hominids), the great apes, include four genera comprising three extant species of orangutans and their subspecies, two extant species of gorillas and their subspecies, two extant species of panins and their subspecies, and humans in a single extant subspecies.

Pan (god)

Pan (god)

In ancient Greek religion and mythology, Pan is the god of the wild, shepherds and flocks, rustic music and impromptus, and companion of the nymphs. He has the hindquarters, legs, and horns of a goat, in the same manner as a faun or satyr. With his homeland in rustic Arcadia, he is also recognized as the god of fields, groves, wooded glens, and often affiliated with sex; because of this, Pan is connected to fertility and the season of spring.

Specific name (zoology)

Specific name (zoology)

In zoological nomenclature, the specific name is the second part within the scientific name of a species. The first part of the name of a species is the name of the genus or the generic name. The rules and regulations governing the giving of a new species name are explained in the article species description. For example, the scientific name for humans is Homo sapiens, which is the species name, consisting of two names: Homo is the "generic name" and sapiens is the "specific name".

Troglodytae

Troglodytae

The Troglodytae, or Troglodyti, were people mentioned in various locations by many ancient Greek and Roman geographers and historians, including Herodotus, Agatharchides, Diodorus Siculus, Strabo, Pliny, Josephus, Tacitus, Claudius Aelianus, Porphyry.

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.^[11] 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 by 1933.^[9][10][12]

Evolution

Relationships among apes. The branch lengths are a measure of evolutionary distinctness. Based on genome sequencing by The Chimpanzee Sequencing and Analysis Consortium. Figure from Yousaf et al. 2021,^[13] adapted from Prado-Martinez et al. 2013.^[14]

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.^[15]

DNA evidence suggests the bonobo and chimpanzee species separated from each other less than one million years ago (similar in relation between Homo sapiens and Neanderthals).^[16][17] A 2017 genetic study suggests ancient gene flow (introgression) between 200 and 550 thousand years ago from the bonobo into the ancestors of central and eastern chimpanzees.^[18] The chimpanzee line split from the last common ancestor of the human line around six million years ago. Because no species other than Homo sapiens has survived from the human line of that branching, both chimpanzee species are the closest living relatives of humans; the lineage of humans and chimpanzees diverged from gorillas (genus Gorilla) about seven million years ago. A 2003 study argues the chimpanzee should be included in the human branch as Homo troglodytes and notes "experts say many scientists are likely to resist the reclassification, especially in the emotionally-charged and often disputed field of anthropology".^[19]

Subspecies and population status

Two juvenile central chimpanzees, the subspecies Pan troglodytes troglodytes

Four subspecies of the chimpanzee have been recognised,^[20][21] with the possibility of a fifth:^[18][22]

• 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.^[23]
• 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.^[24][25]
• Nigeria-Cameroon chimpanzee (P. troglodytes ellioti (also known as P. t. vellerosus)),^[20] that live within forested areas across Nigeria and Cameroon, with 6000–9000 individuals still in existence.^[26][27]
• 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.^[28]
• 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,^[22] but it is not recognised by the IUCN.^[3]

Genome

A draft version of the chimpanzee genome was published in 2005 and encodes 18,759 proteins,^[29][30] (compared to 20,383 in the human proteome).^[31] The DNA sequences of humans and chimpanzees are very similar and the difference in protein number mostly arises from incomplete sequences in the chimp genome. Both species differ by about 35 million single-nucleotide changes, five million insertion/deletion events and various chromosomal rearrangements.^[32] Typical human and chimpanzee protein homologs differ in an average of only two amino acids. About 30% of all human proteins are identical in sequence to the corresponding chimpanzee protein. Duplications of small parts of chromosomes have been the major source of differences between human and chimpanzee genetic material; about 2.7% of the corresponding modern genomes represent differences, produced by gene duplications or deletions, since humans and chimpanzees diverged from their common evolutionary ancestor.^[29][32]

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Bornean orangutan

Bornean orangutan

The Bornean orangutan is a species of orangutan endemic to the island of Borneo. Together with the Sumatran orangutan and Tapanuli orangutan, it belongs to the only genus of great apes native to Asia. Like the other great apes, orangutans are highly intelligent, displaying tool use and distinct cultural patterns in the wild. Orangutans share approximately 97% of their DNA with humans. Also called mias by the local population, the Bornean orangutan is a critically endangered species, with deforestation, palm oil plantations, and hunting posing a serious threat to its continued existence.

Jacobus Bontius

Jacobus Bontius

Jacobus Bontius was a Dutch physician and a pioneer of tropical medicine. He is known for the four-volume work De medicina Indorum. His 1631 work "Historiae naturalis et medicae Indiae orientalis" introduced the word "Orang Hutan" into Western languages.

Johann Friedrich Blumenbach

Johann Friedrich Blumenbach

Johann Friedrich Blumenbach was a German physician, naturalist, physiologist, and anthropologist. He is considered to be a main founder of zoology and anthropology as comparative, scientific disciplines. He was also important as a race theorist.

Chimpanzee–human last common ancestor

Chimpanzee–human last common ancestor

The chimpanzee–human last common ancestor (CHLCA) is the last common ancestor shared by the extant Homo (human) and Pan genera of Hominini. Due to complex hybrid speciation, it is not currently possible to give a precise estimate on the age of this ancestral population. While "original divergence" between populations may have occurred as early as 13 million years ago (Miocene), hybridization may have been ongoing until as recently as 4 million years ago (Pliocene).

Evolution

Evolution

In biology, evolution is the change in heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation tends to exist within any given population as a result of genetic mutation and recombination. Evolution occurs when evolutionary processes such as natural selection and genetic drift act on this variation, resulting in certain characteristics becoming more common or more rare within a population. The evolutionary pressures that determine whether a characteristic is common or rare within a population constantly change, resulting in a change in heritable characteristics arising over successive generations. It is this process of evolution that has given rise to biodiversity at every level of biological organisation.

Homo

Homo

Homo is the genus that emerged in the genus Australopithecus that encompasses the extant species Homo sapiens, plus several extinct species classified as either ancestral to or closely related to modern humans, most notably H. erectus and H. neanderthalensis. The oldest member of Homo is H. habilis with records of just over 2 million years ago. However, a recent phylogenetic study in hominins using morphological, molecular and radiometric information, dates the emergence of Homo at 3.3 Ma. Homo, together with the genus Paranthropus, is probably sister to Australopithecus africanus, which itself had previously split from the lineage of Pan, the chimpanzees.

Clade

Clade

In biological phylogenetics, a clade, also known as a monophyletic group or natural group, is a grouping of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. In the taxonomical literature, sometimes the Latin form cladus is used rather than the English form.

East African Rift

East African Rift

The East African Rift (EAR) or East African Rift System (EARS) is an active continental rift zone in East Africa. The EAR began developing around the onset of the Miocene, 22–25 million years ago. In the past it was considered to be part of a larger Great Rift Valley that extended north to Asia Minor.

Introgression

Introgression

Introgression, also known as introgressive hybridization, in genetics is the transfer of genetic material from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species. Introgression is a long-term process, even when artificial; it may take many hybrid generations before significant backcrossing occurs. This process is distinct from most forms of gene flow in that it occurs between two populations of different species, rather than two populations of the same species.

Human evolution

Human evolution

Human evolution is the evolutionary process within the history of primates that led to the emergence of Homo sapiens as a distinct species of the hominid family, which includes all the great apes. This process involved the gradual development of traits such as human bipedalism, dexterity and complex language, as well as interbreeding with other hominins, indicating that human evolution was not linear but weblike. The study of human evolution involves several scientific disciplines, including physical and evolutionary anthropology, paleontology, and genetics.

Gorilla

Gorilla

Gorillas are herbivorous, predominantly ground-dwelling great apes that inhabit the tropical forests of equatorial Africa. The genus Gorilla is divided into two species: the eastern gorilla and the western gorilla, and either four or five subspecies. The DNA of gorillas is highly similar to that of humans, from 95 to 99% depending on what is included, and they are the next closest living relatives to humans after chimpanzees and bonobos.

Central chimpanzee

Central chimpanzee

The central chimpanzee or the tschego is a subspecies of chimpanzee closely related to the other great apes such as gorillas, orangutans, and humans. The central chimpanzee can be found in Central Africa, mostly in Gabon, Cameroon, Republic of Congo and the Democratic Republic of Congo.

Skeleton

Adult chimpanzees have an average standing height of 150 cm (4 ft 11 in).^[33] Wild adult males weigh between 40 and 70 kg (88 and 154 lb)^[34][35][36] with females weighing between 27 and 50 kg (60 and 110 lb).^[37] 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.^[a]

The chimpanzee is more robustly built than the bonobo but less than the gorilla. The arms of a chimpanzee are longer than its legs and can reach below the knees. The hands have long fingers with short thumbs and flat fingernails. The feet are adapted for grasping, and the big toe is opposable. The pelvis is long with an extended ilium. A chimpanzee's head is rounded with a prominent and prognathous face and a pronounced brow ridge. It has forward-facing eyes, a small nose, rounded non-lobed ears, a long mobile upper lip. Additionally, adult males have sharp canine teeth. Chimpanzees lack the prominent sagittal crest and associated head and neck musculature of gorillas.^[40][12]

Chimpanzee bodies are covered by coarse hair, except for the face, fingers, toes, palms of the hands, and soles of the feet. Chimpanzees lose more hair as they age and develop bald spots. The hair of a chimpanzee is typically black but can be brown or ginger. As they get older, white or grey patches may appear, particularly on the chin and lower region. The skin may range from pale to dark, though females develop swelling pink skin when in oestrus.^[40][12]

Chimpanzees are adapted for both arboreal and terrestrial locomotion. Arboreal locomotion consists of vertical climbing and brachiation.^[41][42] On the ground, chimpanzees move both quadrupedally and bipedally. These movements appear to have similar energy costs.^[43] As with bonobos and gorillas, chimpanzees move quadrupedally by knuckle-walking, which probably evolved independently in Pan and Gorilla.^[44] The physical strength of chimps is around 1.5 times greater than humans due to higher content of fast twitch muscle fibres, one of the chimpanzee's adaptations for climbing and swinging.^[45] According to Japan's Asahiyama Zoo, the grip strength of an adult chimpanzee is estimated to be 200 kg (440 lb),^[46] while other sources claim figures of up to 330 kg (730 lb).^[b]

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Ilium (bone)

Ilium (bone)

The ilium is the uppermost and largest part of the hip bone, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.

Brow ridge

Brow ridge

The brow ridge, or supraorbital ridge known as superciliary arch in medicine, is a bony ridge located above the eye sockets of all primates and some other animals. In humans, the eyebrows are located on their lower margin.

Sagittal crest

Sagittal crest

A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are exceptionally strong jaw muscles. The sagittal crest serves primarily for attachment of the temporalis muscle, which is one of the main chewing muscles. Development of the sagittal crest is thought to be connected to the development of this muscle. A sagittal crest usually develops during the juvenile stage of an animal in conjunction with the growth of the temporalis muscle, as a result of convergence and gradual heightening of the temporal lines.

Arboreal locomotion

Arboreal locomotion

Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose numerous mechanical challenges to animals moving through them and lead to a variety of anatomical, behavioral and ecological consequences as well as variations throughout different species. Furthermore, many of these same principles may be applied to climbing without trees, such as on rock piles or mountains.

Terrestrial locomotion

Terrestrial locomotion

Terrestrial locomotion has evolved as animals adapted from aquatic to terrestrial environments. Locomotion on land raises different problems than that in water, with reduced friction being replaced by the increased effects of gravity.

Brachiation

Brachiation

Brachiation, or arm swinging, is a form of arboreal locomotion in which primates swing from tree limb to tree limb using only their arms. During brachiation, the body is alternately supported under each forelimb. This form of locomotion is the primary means of locomotion for the small gibbons and siamangs of southeast Asia. Gibbons in particular use brachiation for as much as 80% of their locomotor activities. Some New World monkeys, such as spider monkeys and muriquis, were initially classified as semibrachiators and move through the trees with a combination of leaping and brachiation. Some New World species also practice suspensory behaviors by using their prehensile tail, which acts as a fifth grasping hand. Evidence has shown that the extinct ape Proconsul from the Miocene of East Africa developed an early form of suspensory behaviour, and was therefore referred to as a probrachiator.

Knuckle-walking

Knuckle-walking

Knuckle-walking is a form of quadrupedal walking in which the forelimbs hold the fingers in a partially flexed posture that allows body weight to press down on the ground through the knuckles. Gorillas, bonobos, and chimpanzees use this style of locomotion, as do anteaters and platypuses.

Asahiyama Zoo

Asahiyama Zoo

The Asahiyama Zoo is a municipal zoo that opened in July 1967 in Asahikawa, Hokkaidō, Japan, and is the northernmost zoo in the country. In August 2004, over 320,000 people had visited the zoo, the second highest number of visitors among all the zoos in Japan. Located in Higashi Asahikawa, on the outskirts of Asahikawa, the Asahiyama Zoo is accredited by the Japanese Association of Zoos and Aquariums (JAZA).

Overnight nest in a tree

The chimpanzee is a highly adaptable species. It lives in a variety of habitats, including dry savanna, evergreen rainforest, montane forest, swamp forest, and dry woodland-savanna mosaic.^[49][50] In Gombe, the chimpanzee mostly uses semideciduous and evergreen forest as well as open woodland.^[51] At Bossou, the chimpanzee inhabits multistage secondary deciduous forest, which has grown after shifting cultivation, as well as primary forest and grassland.^[52] At Taï, it is found in the last remaining tropical rain forest in Ivory Coast.^[53] The chimpanzee has an advanced cognitive map of its home range and can repeatedly find food.^[54] The chimpanzee builds a sleeping nest in a tree in a different location each night, never using the same nest more than once. Chimpanzees sleep alone in separate nests except for infants or juvenile chimpanzees, which sleep with their mothers.^[55]

Chimpanzees do not appear to directly compete with gorillas in areas where they overlap. When fruit is abundant, gorilla and chimpanzee diets converge, but when fruit is scarce gorillas resort to vegetation.^[56] The two apes may also feed on different species, whether fruit or insects.^[57][58][59] Interactions between the apes can range from friendly and even stable social bonding,^[60] to avoidance,^[56][61] to aggression and predation on part of chimpanzees.^[62]

Diet

A mother with young eating Ficus fruit in Kibale National Park, Uganda

The chimpanzee is an omnivorous frugivore. It prefers fruit above all other food items but also eats leaves, leaf buds, seeds, blossoms, stems, pith, bark, and resin.^[63][64] A study in Budongo Forest, Uganda found that 64.5% of their feeding time concentrated 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.^[65] 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.^[63][66] Insect species consumed include the weaver ant Oecophylla longinoda, Macrotermes termites, and honey bees.^[58][59] The red colobus ranks at the top of preferred mammal prey. Other mammalian prey include red-tailed monkeys, infant and juvenile yellow baboons, bush babies, blue duikers, bushbucks, and common warthogs.^[67]

Despite the fact that chimpanzees are known to hunt and to collect both insects and other invertebrates, such food actually makes up a very small portion of their diet, from as little as 2% yearly to as much as 65 grams of animal flesh per day for each adult chimpanzee in peak hunting seasons. This also varies from troop to troop and year to year. However, in all cases, the majority of their diet consists of fruits, leaves, roots, and other plant matter.^[64][68] Female chimpanzees appear to consume much less animal flesh than males, according to several studies.^[69] Jane Goodall documented many occasions within Gombe Stream National Park of chimpanzees and western red colobus monkeys ignoring each other despite close proximity.^[70][55]

Mortality and health

Chimpanzee named "Gregoire" on 9 December 2006, born in 1944 (Jane Goodall sanctuary of Tchimpounga, Republic of the Congo)

The average lifespan of a chimpanzee in the wild is relatively short, usually less than 15 years, although individuals that reach 12 years may live an additional 15 years. On rare occasions, wild chimpanzees may live nearly 60 years. Captive chimpanzees tend to live longer than most wild ones, with median lifespans of 31.7 years for males and 38.7 years for females.^[71] The oldest known male captive chimpanzee to have been documented lived to 66 years,^[72] and the oldest female, Little Mama, was over 70 years old.^[73]

Leopards prey on chimpanzees in some areas.^[74][75] It is possible that much of the mortality caused by leopards can be attributed to individuals that have specialised in chimp-killing.^[74] Chimpanzees may react to a leopard's presence with loud vocalising, branch shaking, and throwing objects.^[76][74] There is at least one record of chimpanzees killing a leopard cub after mobbing it and its mother in their den.^[77] 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.^[78]

The chimpanzee louse Pediculus schaeffi is closely related to the human body louse P. humanus.

Chimpanzees and humans share only 50% of their parasite and microbe species. This is due to the differences in environmental and dietary adaptations; human internal parasite species overlap more with omnivorous, savanna-dwelling baboons.^[79] The chimpanzee is host to the louse species Pediculus schaeffi, a close relative of P. humanus, which infests human head and body hair. By contrast, the human pubic louse Pthirus pubis is closely related to Pthirus gorillae, which infests gorillas.^[79] 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.^[80]

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Savanna

Savanna

A savanna or savannah is a mixed woodland-grassland ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of grasses. According to Britannica, there exists four savanna forms; savanna woodland where trees and shrubs form a light canopy, tree savanna with scattered trees and shrubs, shrub savanna with distributed shrubs, and grass savanna where trees and shrubs are mostly nonexistent.

Evergreen

Evergreen

In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, which completely lose their foliage during the winter or dry season.

Gombe Stream National Park

Gombe Stream National Park

Gombe Stream National Park is a national park in Kigoma District of Kigoma Region in Tanzania, 16 km (10 mi) north of Kigoma, the capital of Kigoma Region. Established in 1968, it is one of the smallest national parks in Tanzania, with only 35 km2 (13.5 sq mi) of protected land along the hills of the eastern shore of Lake Tanganyika. The terrain is distinguished by steep valleys, and the vegetation ranges from grassland to woodland to tropical rainforest. Accessible only by boat, the park is most famous as the location where Jane Goodall pioneered her behavioural research on the common chimpanzee populations. The Kasakela chimpanzee community, featured in several books and documentaries, lives in Gombe National Park.

Bossou

Bossou

Bossou is a town and sub-prefecture in the Lola Prefecture in the Nzérékoré Region of south-eastern Guinea. Much of the sub prefecture consists of the Mount Nimba Strict Nature Reserve. The Bossou Hills Reserve situated at the south-eastern limit of the city, which is famous for its chimpanzees habituated to humans, and make Bossou Hills the best chimpanzee observer place in Western Africa.

Old-growth forest

Old-growth forest

An old-growth forest, sometimes synonymous with primary forest, virgin forest, late seral forest, primeval forest, or first-growth forest—is a forest that has attained great age without significant disturbance, and thereby exhibits unique ecological features, and might be classified as a climax community. The Food and Agriculture Organization of the United Nations defines primary forests as naturally regenerated forests of native tree species where there are no clearly visible indications of human activity and the ecological processes are not significantly disturbed. More than one-third of the world's forests are primary forests. Old-growth features include diverse tree-related structures that provide diverse wildlife habitat that increases the biodiversity of the forested ecosystem. Virgin or first-growth forests are old-growth forests that have never been logged. The concept of diverse tree structure includes multi-layered canopies and canopy gaps, greatly varying tree heights and diameters, and diverse tree species and classes and sizes of woody debris.

Cognitive map

Cognitive map

A cognitive map is a type of mental representation which serves an individual to acquire, code, store, recall, and decode information about the relative locations and attributes of phenomena in their everyday or metaphorical spatial environment. The concept was introduced by Edward Tolman in 1948. He tried to explain the behavior of rats that appeared to learn the spatial layout of a maze, and subsequently the concept was applied to other animals, including humans. The term was later generalized by some researchers, especially in the field of operations research, to refer to a kind of semantic network representing an individual's personal knowledge or schemas.

Kibale National Park

Kibale National Park

Kibale National Park is a national park in western Uganda, protecting moist evergreen rainforest. It is 766 square kilometres (296 sq mi) in size and ranges between 1,100 metres (3,600 ft) and 1,600 metres (5,200 ft) in elevation. Despite encompassing primarily moist evergreen forest, it contains a diverse array of landscapes. Kibale is one of the last remaining expanses to contain both lowland and montane forests. In eastern Africa, it sustains the last significant expanse of pre-montane forest.

Frugivore

Frugivore

A frugivore is an animal that thrives mostly on raw fruits or succulent fruit-like produce of plants such as roots, shoots, nuts and seeds. Approximately 20% of mammalian herbivores eat fruit. Frugivores are highly dependent on the abundance and nutritional composition of fruits. Frugivores can benefit or hinder fruit-producing plants by either dispersing or destroying their seeds through digestion. When both the fruit-producing plant and the frugivore benefit by fruit-eating behavior the interaction is a form of mutualism.

Pith

Pith

Pith, or medulla, is a tissue in the stems of vascular plants. Pith is composed of soft, spongy parenchyma cells, which in some cases can store starch. In eudicotyledons, pith is located in the center of the stem. In monocotyledons, it extends also into flowering stems and roots. The pith is encircled by a ring of xylem; the xylem, in turn, is encircled by a ring of phloem.

Resin

Resin

In polymer chemistry and materials science, a resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on naturally occurring resins.

Budongo Forest

Budongo Forest

The Budongo Forest in Uganda is northwest of the capital city Kampala on the way to Murchison Falls National Park, and is located on the escarpment northeast of Lake Albert. It is known for its former abundance of East African mahogany trees as well as being home to a population of chimpanzees. An exceptionally large mahogany tree is still found here, and is more than 80 meters tall and some 20 meters in circumference.

Ficus

Ficus

Ficus is a genus of about 850 species of woody trees, shrubs, vines, epiphytes and hemiepiphytes in the family Moraceae. Collectively known as fig trees or figs, they are native throughout the tropics with a few species extending into the semi-warm temperate zone. The common fig (F. carica) is a temperate species native to southwest Asia and the Mediterranean region, which has been widely cultivated from ancient times for its fruit, also referred to as figs. The fruit of most other species are also edible though they are usually of only local economic importance or eaten as bushfood. However, they are extremely important food resources for wildlife. Figs are also of considerable cultural importance throughout the tropics, both as objects of worship and for their many practical uses.

Recent studies have suggested that human observers influence chimpanzee behaviour. One suggestion is that drones, camera traps, and remote microphones should be used to record and monitor chimpanzees rather than direct human observation.^[81]

Group structure

Group in Uganda

Chimpanzees live in communities that typically range from around 20 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.^[55] 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.^[82]

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.^[83] However, this unusual fission-fusion social structure, "in which portions of the parent group may on a regular basis separate from and then rejoin the rest,"^[84] is highly variable in terms of which particular individual chimpanzees congregate at a given time. This is caused mainly by the large measure of individual autonomy that individuals have within their fission-fusion social groups.^[40] As a result, individual chimpanzees often forage for food alone, or in smaller groups, as opposed to the much larger "parent" group, which encompasses all the chimpanzees which regularly come into contact with each other and congregate into parties in a particular area.^[82]

Mutual grooming, removing lice

Male chimpanzees exist in a linear dominance hierarchy. Top-ranking males tend to be aggressive even during dominance stability.^[85] 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 "political maneuvering" has 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.^[85][86]

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.^[87] 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 dyadic interactions.^[85][88] Chimpanzee alliances can be very fickle, and one member may suddenly turn on another if it is to his advantage.^[89]

Males in Mahale National Park, Tanzania

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.^[87][89] 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.^[90] Females in Taï have also been recorded to form alliances.^[91] While chimpanzee social structure is often referred to as patriarchal, it is not entirely unheard of for females to forge coalitions against males.^[92] 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.^[93] 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.^[88]

Chimpanzees have been described as highly territorial and will frequently kill other chimpanzees,^[94] although Margaret Power wrote in her 1991 book The Egalitarians that the field studies from which the aggressive data came, Gombe and Mahale, used artificial feeding systems that increased aggression in the chimpanzee populations studied. Thus, the behaviour may not reflect innate characteristics of the species as a whole.^[95] In the years following her artificial feeding conditions at Gombe, Jane Goodall described groups of male chimpanzees patrolling the borders of their territory, brutally attacking chimpanzees that had split off from the Gombe group. A study published in 2010 found that the chimpanzees wage wars over territory, not mates.^[96] 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.^[97][89] 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.^[98]

Mating and parenting

Infant and mother

Chimpanzees mate throughout the year, although the number of females in oestrus varies seasonally in a group.^[99] 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.^[100][101]

These alternative mating strategies give females more mating opportunities without losing the support of the males in their community.^[101] 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.^[102][103] Females sometimes practice infanticide. This may be related to the dominance hierarchy in females or may simply be pathological.^[90]

Copulation is brief, lasting approximately seven seconds.^[104] The gestation period is eight months.^[40] 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.^[105][106] 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.^[107]

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 interact an increasing amount 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 boundary patrolling.^[107] 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.^[108]

Communication

Pant-hoot call

Pant-hoot call made by an adult male, demonstrating the introduction, build-up, climax, and let-down phases.^[109]

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Chimpanzees use facial expressions, postures, and sounds to communicate with each other. Chimpanzees 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 grin. 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 extends a hand. When in an aggressive mode, a chimpanzee swaggers bipedally, hunched over and arms waving, in an attempt to exaggerate its size.^[110] While travelling, chimpanzees keep in contact by beating their hands and feet against the trunks of large trees, an act that is known as "drumming". They also do this when encountering individuals from other communities.^[111]

Vocalisations are also important in chimpanzee communication. The most common call in adults is the "pant-hoot", which may signal social rank and bond along with keeping groups together. 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.^[111][109] Grunting is made in situations like feeding and greeting.^[111] Submissive individuals make "pant-grunts" towards their superiors.^[112][90] Whimpering is made by young chimpanzees as a form of begging or when lost from the group.^[111] Chimpanzees use distance calls to draw attention to danger, food sources, or other community members.^[113] "Barks" may be made as "short barks" when hunting and "tonal barks" when sighting large snakes.^[111]

Adult male eastern chimpanzee snatches a dead bushbuck antelope from a baboon in Gombe Stream National Park.

Hunting

When hunting small monkeys such as the red colobus, chimpanzees hunt where the forest canopy is interrupted or irregular. This allows them to easily corner the monkeys when chasing them in the appropriate direction. Chimpanzees may also hunt as a coordinated team, so that they can corner their prey even in a continuous canopy. During an arboreal hunt, each chimpanzee in the hunting groups has a role. "Drivers" serve to keep the prey running in a certain direction and follow them without attempting to make a catch. "Blockers" are stationed at the bottom of the trees and climb up to block prey that takes off in a different direction. "Chasers" move quickly and try to make a catch. Finally, "ambushers" hide and rush out when a monkey nears.^[114] While both adults and infants are taken, adult male colobus monkeys will attack the hunting chimps.^[115] Male chimpanzees hunt more than females. When caught and killed, the meal is distributed to all hunting party members and even bystanders.^[114]

Discover more about Behaviour related topics

Unmanned aerial vehicle

Unmanned aerial vehicle

An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without any human pilot, crew, or passengers on board. UAVs were originally developed through the twentieth century for military missions too "dull, dirty or dangerous" for humans, and by the twenty-first, they had become essential assets to most militaries. As control technologies improved and costs fell, their use expanded to many non-military applications. These include aerial photography, precision agriculture, forest fire monitoring, river monitoring, environmental monitoring, policing and surveillance, infrastructure inspections, smuggling, product deliveries, entertainment, and drone racing.

Hunting

Hunting

Hunting is the human practice of seeking, pursuing, capturing, or killing wildlife or feral animals. The most common reasons for humans to hunt are to exploit the animal's body for food and useful animal products, for recreation/taxidermy, although it may also be done for non-exploitative reasons such as removing predators dangerous to humans or domestic animals, to eliminate pests and nuisance animals that damage crops/livestock/poultry or spread diseases, for trade/tourism, or for ecological conservation against overpopulation and invasive species.

Louse

Louse

Louse is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera has variously been recognized as an order, infraorder, or a parvorder, as a result of developments in phylogenetic research.

Dyad (sociology)

Dyad (sociology)

In sociology, a dyad is a group of two people, the smallest possible social group. As an adjective, "dyadic" describes their interaction. The pair of individuals in a dyad can be linked via romantic interest, family relation, interests, work, partners in crime, and so on. The relation can be based on equality, but may be based on an asymmetrical or hierarchical relationship (master–servant). The strength of the relationship is evaluated on the basis of time the individuals spend together, as well as on the emotional intensity of their relationship. The term dyad is from Ancient Greek δυάς (duás) 'pair'.

Social grooming

Social grooming

Social grooming is a behavior in which social animals, including humans, clean or maintain one another's body or appearance. A related term, allogrooming, indicates social grooming between members of the same species. Grooming is a major social activity, and a means by which animals who live in close proximity may bond and reinforce social structures, family links, and build companionships. Social grooming is also used as a means of conflict resolution, maternal behavior and reconciliation in some species. Mutual grooming typically describes the act of grooming between two individuals, often as a part of social grooming, pair bonding, or a precoital activity.

Sexual swelling

Sexual swelling

Sexual swelling, Sexual skin, or Anogenital tumescence refers to localized engorgement of the anus and genital region of some female primates that vary in size over the course of the menstrual cycle. Thought to be an honest signal of fertility, male primates are attracted to these swellings; preferring, and competing for, females with the largest swellings.

Sperm competition

Sperm competition

Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and variety of mates increases a female's chance to produce more viable offspring. However, multiple mates for a female means each individual male has decreased chances of producing offspring. Sperm competition is an evolutionary pressure on males, and has led to the development of adaptations to increase males' chance of reproductive success. Sperm competition results in a sexual conflict of interest between males and females. Males have evolved several defensive tactics including: mate-guarding, mating plugs, and releasing toxic seminal substances to reduce female re-mating tendencies to cope with sperm competition. Offensive tactics of sperm competition involve direct interference by one male on the reproductive success of another male, for instance by physically removing another male's sperm prior to mating with a female. For an example, see Gryllus bimaculatus.

Alternative mating strategy

Alternative mating strategy

An alternative mating strategy is a strategy used by male or female animals, often with distinct phenotypes, that differs from the prevailing mating strategy of their sex. Such strategies are diverse and variable both across and within species. Animal sexual behaviour and mate choice directly affect social structure and relationships in many different mating systems, whether monogamous, polygamous, polyandrous, or polygynous. Though males and females in a given population typically employ a predominant reproductive strategy based on the overarching mating system, individuals of the same sex often use different mating strategies. Among some reptiles, frogs and fish, large males defend females, while small males may use sneaking tactics to mate without being noticed.

Infanticide in primates

Infanticide in primates

Infanticide in non-human primates occurs when an individual kills its own or another individual's dependent young. Five hypotheses have been proposed to explain infanticide in non-human primates: exploitation, resource competition, parental manipulation, sexual selection, and social pathology.

Copulation (zoology)

Copulation (zoology)

In zoology, copulation is animal sexual behavior in which a male introduces sperm into the female's body, especially directly into her reproductive tract. This is an aspect of mating. Many animals that live in water use external fertilization, whereas internal fertilization may have developed from a need to maintain gametes in a liquid medium in the Late Ordovician epoch. Internal fertilization with many vertebrates occurs via cloacal copulation, known as cloacal kiss, while mammals copulate vaginally, and many basal vertebrates reproduce sexually with external fertilization.

Gestation

Gestation

Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals. It is typical for mammals, but also occurs for some non-mammals. Mammals during pregnancy can have one or more gestations at the same time, for example in a multiple birth.

Gombe Stream National Park

Gombe Stream National Park

Gombe Stream National Park is a national park in Kigoma District of Kigoma Region in Tanzania, 16 km (10 mi) north of Kigoma, the capital of Kigoma Region. Established in 1968, it is one of the smallest national parks in Tanzania, with only 35 km2 (13.5 sq mi) of protected land along the hills of the eastern shore of Lake Tanganyika. The terrain is distinguished by steep valleys, and the vegetation ranges from grassland to woodland to tropical rainforest. Accessible only by boat, the park is most famous as the location where Jane Goodall pioneered her behavioural research on the common chimpanzee populations. The Kasakela chimpanzee community, featured in several books and documentaries, lives in Gombe National Park.

Human and chimpanzee skull and brain. Diagram by Paul Gervais from Histoire naturelle des mammifères (1854).

Chimpanzees display numerous signs of intelligence, from the ability to remember symbols^[116] to cooperation,^[117] tool use,^[118] and perhaps language.^[119] They are among species that have passed the mirror test, suggesting self-awareness.^[120] In one study, two young chimpanzees showed retention of mirror self-recognition after one year without access to mirrors.^[121] Chimpanzees have been observed to use insects to treat their own wounds and those of others. They catch them and apply them directly to the injury.^[122] Chimpanzees also display signs of culture among groups, with the learning and transmission of variations in grooming, tool use and foraging techniques leading to localized traditions.^[123]

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.^[116]

In controlled experiments on cooperation, chimpanzees show a basic understanding of cooperation, and recruit the best collaborators.^[117] 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 behaviours.^[124]

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.^[125]

Chimpanzees have displayed different behaviours in response to a dying or dead group member. When witnessing a sudden death, the other group members act in frenzy, with vocalisations, aggressive displays, and touching of the corpse. In one case chimpanzees cared for a dying elder, then attended and cleaned the corpse. Afterward, they avoided the spot where the elder died and behaved in a more subdued manner.^[126] Mothers have been reported to carry around and groom their dead infants for several days.^[127]

Experimenters now and then witness behaviour that cannot be readily reconciled with chimpanzee intelligence or theory of mind. Wolfgang Köhler, for instance, reported insightful behaviour in chimpanzees, but he likewise often observed that they experienced "special difficulty" in solving simple problems.^[128] 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.^[129]

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,^[130] nuts,^{[131][132][130][133]} honey,^[134] algae^[135] or water. Despite the lack of complexity, forethought and skill are apparent in making these tools.^[118] Chimpanzees have used stone tools since at least 4,300 years ago.^[136]

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.^[137][138] At Taï, chimpanzees simply use their hands to extract termites.^[118] 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.^[139]

Chimpanzees also fish for ants using the same tactic.^[140] Ant dipping is difficult and some chimpanzees never master it. West African chimpanzees crack open hard nuts with stones or branches.^[140][118] 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.^[140] Chimpanzees also use leaves as sponges or spoons to drink water.^[141]

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.^[142] An eastern chimpanzee has been observed using a modified branch as a tool to capture a squirrel.^[143]

Whilst experimental studies on captive chimpanzees have found that many of their species-typical tool-use behaviours can be individually learnt by each chimpanzees,^[144] a 2021 study on their abilities to make and use stone flakes, in a similar way as hypothesised for early hominins, did not find this behaviour across two populations of chimpanzees - suggesting that this behaviour is outside the chimpanzee species-typical range.^[145]

Language

Hugo Rheinhold's Affe mit Schädel ("Ape with skull"), c. 1893

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.^[146] Over a longer period of time, Washoe was reported to have learned over 350 signs.^[147]

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.^[119] 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.^[148]

Discover more about Intelligence and cognition related topics

Primate cognition

Primate cognition

Primate cognition is the study of the intellectual and behavioral skills of non-human primates, particularly in the fields of psychology, behavioral biology, primatology, and anthropology.

Paul Gervais

Paul Gervais

Paul Gervais full name François Louis Paul Gervais was a French palaeontologist and entomologist.

Mirror test

Mirror test

The mirror test—sometimes called the mark test, mirror self-recognition (MSR) test, red spot technique, or rouge test—is a behavioral technique developed in 1970 by American psychologist Gordon Gallup Jr. as an attempt to determine whether an animal possesses the ability of visual self-recognition. The MSR test is the traditional method for attempting to measure physiological and cognitive self-awareness. However, agreement has been reached that animals can be self-aware in ways not measured by the mirror test, such as distinguishing between their own and others' songs and scents.

Self-awareness

Self-awareness

In philosophy of self, self-awareness is the experience of one's own personality or individuality. It is not to be confused with consciousness in the sense of qualia. While consciousness is being aware of one's environment and body and lifestyle, self-awareness is the recognition of that awareness. Self-awareness is how an individual experiences and understands their own character, feelings, motives, and desires.

Animal culture

Animal culture

Animal culture can be defined as the ability of non-human animals to learn and transmit behaviors through processes of social or cultural learning. Culture is increasingly seen as a process, involving the social transmittance of behavior among peers and between generations. It can involve the transmission of novel behaviors or regional variations that are independent of genetic or ecological factors.

Kyoto University

Kyoto University

Kyoto University , or KyotoU , is a public research university located in Kyoto, Japan. Founded in 1897, it is one of the former Imperial Universities and the second oldest university in Japan. KyotoU is consistently ranked amongst the top two in Japan, the top ten in Asia, and the world's top fifty institutions of higher education.

Primate Research Institute

Primate Research Institute

The Primate Research Institute, Kyoto University is a Japanese research center for the study of primates. It was founded in 1967 by primatologists Kinji Imanishi and Junichiro Itani. The institute works toward understanding the biological, behavioral and socioecological aspects of primates, and the origin and evolution of humans. The institute is located in the city of Inuyama, Aichi Prefecture, which is about 150 km east of the main campus of Kyoto University. Through the Division of Biological Sciences of the Graduate School of Science of Kyoto University, the institute offers graduate programs leading to the Master of Science and Doctorate of Science degrees in the field of primatological science. Since 2013, the director of the institute is botanist Hirohisa Hirai.

Eidetic memory

Eidetic memory

Eidetic memory is the ability to recall an image from memory with high precision—at least for a brief period of time—after seeing it only once and without using a mnemonic device.

Ayumu (chimpanzee)

Ayumu (chimpanzee)

Ayumu is a chimpanzee currently living at the Primate Research Institute of Kyoto University. He is the son of chimpanzee Ai and has been a participant since infancy in the Ai Project, an ongoing research effort aimed at understanding chimpanzee cognition. As part of the Ai Project, Ayumu participated in a series of short-term memory tasks, such as to remember the sequential order of numbers displaying on a touch-sensitive computer screen. His performance in the tasks was superior to that of comparably trained university students, leading to a possible conclusion that young chimpanzees have better working memory than adult humans, although this has been disputed.

Cooperative pulling paradigm

Cooperative pulling paradigm

The cooperative pulling paradigm is an experimental design in which two or more animals pull rewards toward themselves via an apparatus that they cannot successfully operate alone. Researchers use cooperative pulling experiments to try to understand how cooperation works and how and when it may have evolved.

Laughter in animals

Laughter in animals

Laughter in animals other than humans describes animal behavior which resembles human laughter.

Kasakela chimpanzee community

Kasakela chimpanzee community

The Kasekela chimpanzee community is a habituated community of wild eastern chimpanzees that lives in Gombe National Park near Lake Tanganyika in Tanzania. The community was the subject of Jane Goodall's pioneering study that began in 1960, and studies have continued ever since, becoming the longest continuous study of any animals in their natural habitat. As a result, the community has been instrumental in the study of chimpanzees and has been popularized in several books and documentaries. The community's popularity was enhanced by Goodall's practice of giving names to the chimpanzees she was observing, in contrast to the typical scientific practice of identifying the subjects by number. Goodall generally used a naming convention in which infants were given names starting with the same letter as their mother, allowing the recognition of matrilineal lines.

In culture

Chimpanzee mask, Gio tribe, Liberia

Chimpanzees are rarely represented in African culture, as people find their resemblance to humans discomforting. The Gio people of Liberia and the Hemba people of the Congo have created masks of the animals. Gio masks are crude and blocky, and worn when teaching young people how not to behave. The Hemba masks have a smile that suggests drunken anger, insanity or horror and are worn during rituals at funerals, representing the "awful reality of death". The masks may also serve to guard households and protect both human and plant fertility. Stories have been told of chimpanzees kidnapping and raping women.^[149]

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. Accordingly, 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).^[150] From 1926 until 1972, London Zoo, followed by several other zoos around the world, held a chimpanzees' tea party daily, inspiring a long-running series of advertisements for PG Tips tea featuring such a party.^[151][152] Animal rights groups have urged a stop to such acts, considering them abusive.^[153]

Poster for the 1931 film Aping Hollywood. Media like this relied on the novelty of performing apes to carry their gags.^[150]

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 (The Black Stallion) 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.^[150]

As pets

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 confiscate chimpanzees from people keeping them as pets.^[154] Outside their range, chimpanzees are popular as exotic pets despite their strength and aggression. Even where keeping non-human primates as pets is illegal, the exotic pet trade continues to prosper, leading to injuries from attacks.^[155]

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,^[156] 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".^[157] Research chimpanzees tend to be used repeatedly over decades for up to 40 years, unlike the pattern of use of most laboratory animals.^[158] 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.^[159] Five hundred chimpanzees have been retired from laboratory use in the U.S. and live in animal sanctuaries in the U.S. or Canada.^[156]

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.^[159] 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.^[159][160] However, in 2007, the NIH made the moratorium permanent.^[161]

Ham, the first great ape in space, before being inserted into his Mercury-Redstone 2 capsule on 31 January 1961

Other researchers argue that chimpanzees either should not be used in research, or should be treated differently, for instance with legal status as persons.^[162] 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.^[159] A recent study suggests chimpanzees which are retired from labs exhibit a form of post-traumatic stress disorder.^[163] 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."^[159]

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.^[164] Trials already under way were however allowed to run their course.^[165] Chimpanzees including the female Ai have been studied at the Primate Research Institute of Kyoto University, Japan, formerly directed by Tetsuro Matsuzawa, since 1978. Some 12 chimpanzees are currently held at the facility.^[166]

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.^[167][168]

Field study

Feeding station at Gombe, where Jane Goodall used to feed and observe the chimpanzees

Jane Goodall undertook the first long-term field study of the chimpanzee, begun in Tanzania at Gombe Stream National Park in 1960.^[169] Other long-term studies begun in the 1960s include A. Kortlandt's in the eastern Democratic Republic of the Congo and Toshisada Nishida's in Mahale Mountains National Park in Tanzania.^[170][171] Current understanding of the species' typical behaviours and social organisation has been formed largely from Goodall's ongoing 60-year Gombe research study.^{[172][173][95]}

Attacks

Chimpanzees have attacked humans.^[174][175] 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.^[176] Human interactions with chimpanzees may be especially dangerous if the chimpanzees perceive humans as potential rivals.^[177] At least six cases of chimpanzees snatching and eating human babies are documented.^[178]

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 (in the St. James Davis Chimpanzee Attack) while he and his wife were celebrating the birthday of their former pet chimpanzee.^[179][180] 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.^[181][182]

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 is largely confined to west Africa.^[183] 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.^[184][185] 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.^[183]

Status and conservation

Cameroonian chimpanzee at a rescue centre after its mother was killed by poachers

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,^[3] a decrease from about a million chimpanzees in the early 1900s.^[186] 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.^[4]

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.^[3]

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.^[3]

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 human populations grow, so does the risk of disease transmission between humans and chimpanzees.^[3]

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