Their hair is typically black or brown. Males and females differ in size and appearance. Both chimps and bonobos are some of the most social great apes, with social bonds occurring in large communities. Fruit is the most important component of an chimpanzee's diet; however, they will also eat vegetation, bark, honey, insects and even other chimps or monkeys. They can live over 30 years in both the wild and captivity.
Chimpanzees and bonobos are equally humanity's closest living relatives. As such, they are among the largest brained and most intelligent of primates; they use a variety of sophisticated tools and construct elaborate sleeping nests each night from branches and foliage. They have both been extensively studied for their learning abilities. There may even be distinctive cultures within populations. Field studies of Pan troglodytes were pioneered by primatologist Jane Goodall. Both Pan species are considered to be endangered as human activities have caused severe declines in the populations and ranges of both species. Threats to wild panina populations include poaching, habitat destruction, and the illegal pet trade. Several conservation and rehabilitation organisations are dedicated to the survival of Pan in the wild.
A chimpanzee's arms are longer than its legs. The male common chimp stands up to 1.2 m (3.9 ft) high and weighs as much as 70 kg (150 lb); the female is somewhat smaller. When extended, the common chimp’s long arms span one and a half times the body’s height. The bonobo is slightly shorter and thinner than the common chimpanzee, but has longer limbs. In trees, both species climb with their long, powerful arms; on the ground, chimpanzees usually knuckle-walk, or walk on all fours, clenching their fists and supporting themselves on the knuckles. Chimpanzees are better suited for walking than orangutans, because the chimp's feet have broader soles and shorter toes. The bonobo has proportionately longer upper limbs and walks upright more often than does the common chimpanzee. Both species can walk upright on two legs when carrying objects with their hands and arms.
The chimpanzee is tailless; its coat is dark; its face, fingers, palms of the hands, and soles of the feet are hairless. The exposed skin of the face, hands, and feet varies from pink to very dark in both species, but is generally lighter in younger individuals and darkens with maturity. A University of Chicago Medical Centre study has found significant genetic differences between chimpanzee populations. A bony shelf over the eyes gives the forehead a receding appearance, and the nose is flat. Although the jaws protrude, a chimp's lips are thrust out only when it pouts. The brain of a chimpanzee has been measured at a general range of 282–500 cc. The human brain, in contrast, is about three times larger, with a reported average volume of about 1330 cc.
Chimpanzees reach puberty between the age of eight and ten years. A chimpanzee's testicles are unusually large for their body size, with a combined weight of about 4 oz (110 g) compared to a gorilla's 1 oz (28 g) or a human's 1.5 ounces (43 g). This relatively great size is generally attributed to sperm competition due to the polyandrous nature of chimpanzee mating behavior. One study estimates that chimps live about 33 years for males, 37 years for females, in the wild, but some have lived longer than 60 years in captivity.
Anatomical differences between the common chimpanzee and the bonobo are slight, but sexual and social behaviours are markedly different. The common chimpanzee has an omnivorous diet, a troop hunting culture based on beta males led by an alpha male, and highly complex social relationships. The bonobo, on the other hand, has a mostly frugivorous diet and an egalitarian, nonviolent, matriarchal, sexually receptive behaviour. Bonobos frequently have sex, sometimes to help prevent and resolve conflicts. Different groups of chimpanzees also have different cultural behaviour with preferences for types of tools. The common chimpanzee tends to display greater aggression than does the bonobo. The average, captive chimpanzee sleeps 9.7 hours per day.
Chimpanzees live in large multi-male and multi-female social groups, which are called communities. Within a community, the position of an individual and the influence the individual has on others dictates a definite social hierarchy. Chimpanzees live in a leaner hierarchy wherein more than one individual may be dominant enough to dominate other members of lower rank. Typically, a dominant male is referred to as the alpha male. The alpha male is the highest-ranking male that controls the group and maintains order during disputes. In chimpanzee society, the 'dominant male' sometimes is not the largest or strongest male but rather the most manipulative and political male that can influence the goings on within a group. Male chimpanzees typically attain dominance by cultivating allies who will support that individual during future ambitions for power. The alpha male regularly displays by puffing his normally slim coat up to increase view size and charge to seem as threatening and as powerful as possible; this behaviour serves to intimidate other members and thereby maintain power and authority, and it may be fundamental to the alpha male's holding on to his status. Lower-ranking chimpanzees will show respect by submissively gesturing in body language or reaching out their hands while grunting. Female chimpanzees will show deference to the alpha male by presenting their hindquarters.
Female chimpanzees also have a hierarchy, which is influenced by the position of a female individual within a group. In some chimpanzee communities, the young females may inherit high status from a high-ranking mother. Dominant females will also ally to dominate lower-ranking females: whereas males mainly seek dominant status for its associated mating privileges and sometimes violent domination of subordinates, females seek dominant status to acquire resources such as food, as high-ranking females often have first access to them. Both genders acquire dominant status to improve social standing within a group.
Community female acceptance is necessary for alpha male status; females must ensure that their group visits places that supply them with enough food. A group of dominant females will sometimes oust an alpha male which is not to their preference and back another male, in whom they see potential for leading the group as a successful alpha male.
Chimpanzees make tools and use them to acquire foods and for social displays; they have sophisticated hunting strategies requiring cooperation, influence and rank; they are status conscious, manipulative and capable of deception; they can learn to use symbols and understand aspects of human language including some relational syntax, concepts of number and numerical sequence; and they are capable of spontaneous planning for a future state or event.
n October 1960, Jane Goodall observed the use of tools among chimpanzees. Recent research indicates chimpanzee stone tool use dates to at least 4,300 years ago. Chimpanzee tool usage includes digging into termite mounds with a large stick tool, and then using a small stick that has been altered to "fish" the termites out. There have been occasional unsubstantiated or controversial reports of chimpanzees using rocks or sticks as weapons. A recent study claimed to reveal the use of spears, which common chimpanzees in Senegal sharpen with their teeth and use to stab and pry Senegal bushbabies out of small holes in trees. Chimpanzees are also known to use stones as anvils and hammers in order to break open nuts Before the discovery of tool use in chimps, humans were believed to be the only species to make and use tools, but several other tool-using species are now known.
Nest-building, sometimes considered as tool use, is seen in chimpanzees which construct arboreal night nests by lacing together branches from one or more trees. It forms an important part of their behaviour, especially in the case of mothers who teach this trait to infants. Nests consist of a mattress, supported on a strong foundation, and lined above with soft leaves and twigs, and are built in trees with a minimum diameter of 5 metres (16 ft) and may be located at a height of 3 to 45 metres (10 to 150 ft). Both day and night nests are built; they may be located in groups. A study in 2014 found that the Muhimbi tree is favoured for nest building by chimpanzees in Uganda due to its physical properties, such as bending strength, inter-node distance, and leaf surface area.