Common chimpanzee

Appearance

The adult male common chimpanzee weighs between 40 and 60 kg, the female weighs 32 to 47 kg. However, large wild males can weigh up to 70 kg and males in captivity, such as Travis the Chimp, have reached 91 kg.

Head-body length ranges from 63 to 94 cm. Males can measure up to 1.6 m tall while standing and females up to 1.3 m tall. Their bodies are covered by coarse black hair, except for the face, fingers, toes, palms of the hands and soles of the feet.

Both its thumbs and big toes are opposable, allowing a precise grip. The common chimpanzee is both arboreal and terrestrial and spends its nights in the trees, while most daylight hours are spent on the ground.

Its habitual gait is quadrupedal, using the soles of its feet and resting on its knuckles, but it can walk upright for short distances. The common chimpanzee is a 'knuckle walker', like the gorilla and the bonobo, in contrast to the quadrupedal locomotion of the orangutan, a 'palm walker' that uses the outside edge of its palms.

Naming

The species name ''troglodytes'', Greek for "cave-dweller", was coined by Johann Friedrich Blumenbach in his book ''De generis humani varietate nativa liber'' published in 1776, This book was based on his dissertation presented one year before to the University of Göttingen for internal use only, thus the dissertation did not meet the conditions for published work in the sense of zoological nomenclature.

The English name ''chimpanzee'' came from a Bantu language of Angola.

Status

Chimpanzee are a legally protected species in most of their range and can be found both in and outside national parks. There are thought to be between 172,700 to 299,700 individuals living in the wild.

The biggest threats to the common chimpanzee are habitat destruction, poaching and disease. Chimpanzee habitats have been limited by deforestationin 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 have not been seriously impacted by humans. While deforestation rates are low in western Central Africa, selective logging may be done outside national parks.

Behavior

Chimpanzees use a variety of facial expressions, postures and sounds to communicate with each other.

Chimps have expressive faces which are important in close-up communications. When frightened, a "full closed grin" causes nearby individuals to be fearful, as well. Other facial expressions include the "lip flip", "pout", "sneer", and "compressed-lips face". When submitting to a conspecific, a chimp will crunch, bob and extend a hand.

When in an aggressive mode, a chimp will swagger bipedally, hunched over and arms waving, in an attempt to exaggerate its size. Chimps will beat their hands and feet against the trunks of large tree, an act known as "drumming".

Vocalizations are also important in chimp communication. The most common and important call in adults is the "pant-hoot". These calls are made when individuals are excited. Pant-hoots are made of four parts, starting with soft "hoos" that get louder and louder and climax into screams and sometimes barks; the former die down to soft "hoos" again as the call ends.

Submissive individuals will make "pant-grunts" towards their superiors. Chimps use distance calls to draw attention to danger, food sources or other community members.

"Barks" may be made as "short barks" when hunting and "tonal barks" when sighting large snakes.

Nearly all chimpanzee populations have been recorded using tools. They will modify sticks, rocks, grass, and leaves and use them when foraging for honey, termites, ants, nuts, and water. Despite the lack of complexity, there does seem to be forethought and skill in making these tools and should be considered such. While it has been known since Jane Goodall's 1960s discovery that modern chimpanzees use tools, research published in 2007 indicates that chimpanzee stone tool use dates to at least 4,300 years ago.

Habitat

The common 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.

The chimpanzee has an advanced cognitive map of its home range and can repeatedly find food. The chimpanzee makes a night nest in a tree in a new location every night, with every chimpanzee in a separate nest other than infants or small chimpanzees, which sleep with their mothers.

Food

The chimpanzee is an omnivorous frugivore. It prefers fruit above all other food items and will even seek out and eat them when they are not abundant. It will also eat leaves and leaf buds. Seeds, blossoms, stems, pith, bark and resin, insects and meat make up the rest of its diet.

While the common chimpanzee is mostly herbivorous, it does eat honey, soil, insects, birds and their eggs, and small to medium-sized mammals, including other primates. The western red colobus ranks at the top of preferred mammal prey. Other mammalian prey include red-tailed monkeys, yellow baboons, blue duikers, bushbucks and common warthogs.

When hunting small monkeys such as the red colobus, the chimpanzee hunts where the forest canopy is interrupted or irregular. This allows it to easily corner the monkeys when chasing them in the appropriate direction. Chimps may also hunt as a coordinated team, so that they can corner their prey even in a continuous canopy.

During an arboreal hunt, each chimp 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 will climb up to block prey that take off an a different direction. "Chasers" move quickly and try to make a catch.

Finally, "ambushers" hide and rush out when a monkey nears. While both adults and infants are taken, adult male black-and-white colobus monkeys will attack the hunting chimps.

Despite the fact that common chimpanzees are known to hunt, and to collect insects and other invertebrates, such food actually makes up a small portion of their diet; from as little as two percent yearly to as much as 65 grams of meat 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.

Defense

When confronted by a predator, the chimpanzee will react with loud screams and use any object it can against the threat. Leopard predation is apparently a significant cause of mortality in chimpanzees at Taï and Lopé National Parks.

Evolution

Despite a large number of ''Homo'' fossil finds, chimpanzee 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. However, chimpanzee fossils have now been reported from Kenya. This would indicate that both humans and members of the ''Pan'' clade were present in the East African Rift Valley during the Middle Pleistocene.

According to John Gribbin and Jeremy Cherfas in their books ''The Monkey Puzzle: Reshaping the Evolutionary Tree'' and ''The First Chimpanzee: In Search of Human Origins'', chimps and bonobos may be descended from ''Australopithecus''. Chimpanzees were amongst the animals affected during the Toba eruption, hinting that Toba ash extended far west as Africa.