Animals

Chimpanzees

The chimpanzee (Pan troglodytes), sometimes known as the common chimpanzee, is a species of great ape . Chimpanzees and bonobos together form the genus Pan. These two species are the closest living relatives of human beings.  The common ancestor of humans, chimpanzees and bonobos lived until about 6 million years ago.

Chimpanzees range in height from about 3 feet 3 inches to about 5 feet 6 inches (1 to 1.7 meters). In the wild, adult females weigh between 57 and 100 pounds (26 and 50 kilograms), and adult males weigh between 75 and 154 pounds (34 and 70 kilograms). Chimpanzees in captivity are usually heavier.

A chimpanzee has black hair. When the chimpanzee ages, its hair may turn gray, and it may develop a bald spot on its head.  Some chimpanzee's have white hair around their mouths.

Newborn chimpanzees have white tufts of hair on their tails.

Young chimpanzees, photo by Delphine BruyereA chimpanzee's face is hairless, and can range in color from pink to black.

Chimpanzees have protruding lips and snouts, big ears and brow ridges.

They have long arms. A chimpanzee's arm span is greater than its height.

Chimpanzees can swing from tree to tree (brachiate).

When on the ground, chimpanzees usually walk on their knuckles.  As their arms are much longer than their legs, when they walk, the fronts of their bodies are higher than the backs of their bodies. They can walk upright for short distances.

Chimpanzees are native to central Africa, where they can be found in tropical rain forests, mountain forests and grasslands.

They sleep in nests that they build in trees.

A chimpanzee's diet of includes fruit, nuts, seeds, bark, flowers, eggs, insects and other mammals. Chimpanzees hunt large mammals, including colobus monkeys, baboons and wild pigs.

The life expectancy of a chimpanzee in the wild is about 50 years. In captivity, a chimpanzee can live for another decade.

Chimpanzees are endangered because of hunting and habitat loss.

Chimpanzee Social Structure

Chimpanzees live in large social groups.  One dominant male will have control over a group.  All of the adult males in the group are dominant over all of the females.

Males within a social group sometimes form coalitions, with low-ranking males using relationships with other males to move up in the dominance hierarchy.

Sometimes females leave their group and join other groups after they reach adolescence.

A social group may break up into small subgroups, which travel by themselves.

Mating, Reproduction and Childcare

Mating in chimpanzees has purposes other than reproduction and takes place much more often than is needed for reproduction. Mating is used to create social bonds and to help keep the group together.

Although both males and females can have multiple sexual partners, sometimes a male chimpanzee will prevent a female from mating with other males.

Chimpanzees enter puberty when they are about 7 years old.  Females reach sexual maturity when they are about 13, and males, when they are about 15.

Female chimpanzees have an estrus cycle of about 36 days.

At the beginning of the cycle, a female may mate with adolescent or very young males.  These young chimpanzees are probably learning about sex.

Later on, she may mate with many other males.

After this, dominant males may try to prevent other males form mating with her. Sometimes, a dominant male's proximity to a female may be enough to keep other males away. At other times, he may have to resort to threats or even physical violence.

If the female shows that she is interested in another male, the dominant male might threaten or attack her.

Sometimes, a male may gain exclusive sexual access to a female by leading her away for the rest of the group, in a situation known as a consortship. Consort pairs will stay together for up to three months, often at the edge of the group's territory. The female voluntarily agrees to take part in the consortship.

Male chimpanzees may court sexually receptive females by giving them food.

A female chimpanzee will usually give birth to one child at a time. Sometimes, chimpanzees have twins.

The mother provides most of the parental care.

Babies nurse for about four years and stay with their mothers for about another four years after that.  The mother will not have another child until about four or five years after she has given birth, after she is done nursing.

If a chimp's mother dies when the chimp is very young, an older sibling or another close relative may adopt it and care for it as if it were their own child.

Aggression

While chimpanzees often assert dominance over other members of their group by means of social displays, sometimes conflicts can lead to violence. At times, chimpanzees will fight to the death.

There are large battles between different groups of chimpanzees.  Sometimes a large group of chimpanzees will annihilate a smaller group.

Chimpanzees and human beings are the only species that we know of that will intentionally enter an enemy's territory with the intention of hurting or killing the enemy.

Chimpanzee Intelligence

Chimpanzees use tools.  They use rocks and sticks to crack nuts open and sticks and stems to extract insects from nests. They use leaves as napkins and as sponges, for soaking up drinking water. Chimpanzees use sticks as weapons, both as clubs and as projectiles. They sharpen sticks with their teeth to form spears.

Tool use varies among different chimpanzees communities. Different groups will use different tools in different ways. This indicates that chimpanzees have culture - information is passed from chimpanzee to chimpanzee within a group, and is transmitted through generations.

If a female leaves her group and joins a new one, she may teach members of her new group things that she learned while growing up in her old group.

Sometimes chimpanzees in different groups will eat different foods - even though the same foods are available to both groups.  This indicates that food choice is part of chimpanzee culture.

Chimpanzees seem to use plants for medicinal purposes.  There are plants that chimpanzees appear seem  consume only when they appear to be ill, with stomachaches or headaches, for example,  or at times of the year when parasitic infections are common.

These are the same plants that humans who live nearby use to similar treat medical conditions.

Chimpanzees have been taught to use sign language and to communicate using symbols on a computer.

Washoe, a female chimpanzee, was taught how to use American Sign Language in the 1960s. Washoe could combine words to create new ones.

A female chimpanzee named Ai, who has been part of the Ape Language Research Project at Kyoto University in 1977, can recognize and understand Japanese characters on a computer screen.

Chimpanzees understand numbers. They can count, and they can subtract.

Ai was the first chimpanzee to associate Arabic numerals with the quantities that they represent.

Chimpanzees have bested humans in a short-term memory test that involves memorizing the position of numbers on a screen and then recalling them in numerical order.  Ai's son, Ayumu, is known for the amazing speed at which he can perform this task.

Like all great apes, chimpanzees are self-aware.

Chimpanzees can make plans. They work together when they are looking for food and when they are hunting.

They can think abstractly and make generalizations.  They use manipulation and deception to achieve their goals.