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Chimpanzee
Chimp.jpg
General Information
Universe Real Life
Aliases Chimp
Classification Pan troglodytes
Species Type Great Ape
Homeworld Earth
Environment Arboreal
Intelligence Non-sapient
Sapient
Biochemistry Carbon-based
Biological Information
Lifespan Wild: 15 years
Captivity: 32-39 years
Reproduction Sexual, viviparous
Average Height 1.5 m (4'11.06")
Average Weight ♂: 40-70 kg (88.18-154.32 lbs)
♀: 27-50 kg (59.52-110.23 lbs)
Locomotion Semi-bipedal
Feeding Behavior Omnivorous
Prey Insects
Predators Leopards
Snakes
Humans (illegally)
Lineage Information
Related Species Bonobo
Cultural Information
Language(s) Varies
Sociocultral characteristics
Scientific Taxonomy
Planet Earth
Domain Eukaryota
Kingdom Animalia
Subkingdom Bilateria
Infrakingdom Deuterostomia
Phylum Chordata
Subphylum Vertebrata
Infraphylum Gnathostomata
Superclass Tetrapoda
Class Mammalia
Subclass Theria
Infraclass Placentalia
Superorder Euarchontoglires
Order Primates
Suborder Haplorhini
Infraorder Simiiformes
Superfamily Hominoidea
Family Hominidae
Subfamily Homininae
Tribe Hominini
Genus Pan
Species P. troglodytes
Other Information
Status Endangered
Creator God (debated)

The chimpanzee (Pan troglodytes), often shortened to simply "chimp" is an arboreal hominid.

Description[]

Adult chimpanzees have an average standing height of 150 cm (4 ft 11 in).[30] Wild adult males weigh between 40 and 70 kg (88 and 154 lb)[31][32][33] with females weighing between 27 and 50 kg (60 and 110 lb).[34] 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, the big toe being 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 and, in adult males, sharp canine teeth. Chimpanzees lack the prominent sagittal crest and associated head and neck musculature of gorillas.[37][11]

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, and females develop swelling pink skin when in oestrus.[37][11]

Chimpanzees are adapted for both arboreal and terrestrial locomotion. Arboreal locomotion consists of vertical climbing and brachiation.[38][39] On the ground chimpanzees move both quadrupedally and bipedally, which appear to have similar energy costs.[40] As with bonobos and gorillas, chimpanzees move quadrupedally by knuckle-walking, which probably evolved independently in Pan and Gorilla.[41] 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.[42] According to Japan's Asahiyama Zoo, the grip strength of an adult chimpanzee is estimated to be 200 kg (441 lb),[43] while other sources claim figures of up to 330 kg (727 lb).

Ecology[]

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.[46][47] In Gombe, the chimpanzee mostly uses semideciduous and evergreen forest as well as open woodland.[48] At Bossou, the chimpanzee inhabits multistage secondary deciduous forest, which has grown after shifting cultivation, as well as primary forest and grassland.[49] At Taï, it is found in the last remaining tropical rain forest in Ivory Coast.[50] The chimpanzee has an advanced cognitive map of its home range and can repeatedly find food.[51] 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.

Diet[]

The chimpanzee is an omnivorous frugivore. It prefers fruit above all other food items but also eats leaves and leaf buds, seeds, blossoms, stems, pith, bark and resin.[53][54] A study in Budongo Forest, Uganda found that 64.5% of chimp feeding time concentrated on fruits (84.6% of which being ripe), particularly those from two species of Ficus, Maesopsis eminii and Celtis durandii. In addition, 19% of feeding time was spent on arboreal leaves, mostly Broussonetia papyrifera and Celtis mildbraedii.[55] 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.[53][56] Insect species consumed include the weaver ant Oecophylla longinoda, Macrotermes termites and honey bees.[57][58] The western 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.[59]

Despite the fact that chimpanzees are known to hunt, and to collect 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.[54][60] Female chimpanzees appear to consume much less animal flesh than males, according to several studies.[61] Jane Goodall documented many occasions within Gombe Stream National Park of chimpanzees and western red colobus monkeys ignoring each other despite close proximity.[62][52]

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.[63] The two apes may also feed on different species, whether fruit or insects.[64][57][58] Chimpanzees and gorillas usually ignore or avoid each other when feeding on the same tree,[63][65] but coalitions of chimpanzees have been observed attacking families of gorillas including silverbacks and killing infants.

Mortality and health[]

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. Wild individuals may live over 25 years and on rare occasions, around 60 years. Captive chimpanzees tend to live longer, with median lifespans of 31.7 years for males and 38.7 years for females.[67] The oldest known male captive chimpanzee to have been documented lived to 66 years,[68] and the oldest female, Little Mama, was over 70 years old.[69]

Leopards prey on chimpanzees in some areas.[70][71] It is possible that much of the mortality caused by leopards can be attributed to individuals that have specialised in chimp-killing.[70] Chimpanzees may react to a leopard's presence with loud vocalising, branch shaking and throwing objects.[72][70] There is at least one record of chimpanzees killing a leopard cub, after mobbing it and its mother in their den.[73] 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.[74]

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.[75] 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.[75] 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.

Behavior[]

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 observation.

Group structure[]

Chimpanzees live in communities that typically range from around 20 to more than 150 members, but spend most of their time travelling in small, temporary groups consisting of a few individuals, which may consist of any combination of age and sex classes. Both males and females sometimes travel alone.[52] This fission-fusion society may include groups of four types: all-male, adult females and offspring, 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.[79] 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,"[80] 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.[37] 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 and congregate into parties in a particular area.

Male chimpanzees exist in a linear dominance hierarchy. Top-ranking males tend to be aggressive even during dominance stability.[81] 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.

Males maintain and improve their social ranks by forming coalitions, which have been characterised as "exploitative" and are based on an individual's influence in agonistic interactions.[83] 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.[81][84] 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.[83][85] 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.[86] Females in Taï have also been recorded to form alliances.[87] While chimpanzee social structure is often referred to as patriarchal, it is not entirely unheard of for females to forge coalitions against males.[88] 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.[89] Social grooming appears to be important in the formation and maintenance of coalitions. It is more common among adult males than adult females and between males and females.

Chimpanzees have been described as highly territorial and will frequently kill other chimpanzees,[90] 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, and might not reflect innate characteristics of the species as a whole as such.[91] 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.[92] 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.[93][85] 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.

Mating and parenting[]

Chimpanzees mate throughout the year, although the number of females in oestrus varies seasonally in a group.[95] 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.[96][97]

These alternative mating strategies give females more mating opportunities without losing the support of the males in their community.[97] 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.[98][99] Females sometimes practice infanticide; this may be related to the dominance hierarchy in females, or may simply be pathological.[86]

Copulation is brief, lasting approximately seven seconds.[100] The gestation period is eight months.[37] 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.[101][102] Newborn chimpanzees are helpless; 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.[103]

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.[103] 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. 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.[106] 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.[107]

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.[107][105] Grunting is made in situations like feeding and greeting.[107] Submissive individuals make "pant-grunts" towards their superiors.[108][86] Whimpering is made by young chimpanzees as a form of begging or when lost from the group.[107] Chimpanzees use distance calls to draw attention to danger, food sources, or other community members.[109] "Barks" may be made as "short barks" when hunting and "tonal barks" when sighting large snakes.

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.[110] While both adults and infants are taken, adult male colobus monkeys will attack the hunting chimps.[111] Male chimpanzees hunt more than females. When caught and killed, the meal is distributed to all hunting party members and even bystanders.

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