General Information
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Physical Description
Female chimpanzees are smaller in size than males with a weight of up to 176 pounds. Male chimpanzees can weigh up to 196 pounds (Pankopf, 2000). Size varies depending on habitat, with chimpanzees in West Africa and captivity typically larger than those in Gombe (Goodall, 2001). Chimpanzees have arms that are longer than their legs, which allow them to reach for food that grows on branches, such as fruits. They are built for climbing and easily swing from branch to branch. On the ground, Chimpanzees tend to walk on their knuckles, though they are capable of bipedal walking. Chimpanzees also have opposable thumbs that allow them to grip exceptionally well the branches from which they swing, foods they grasp, or tools they use (Goodall, 2001).
These apes lack a tail and facial hair. Their body hair is black or brown, and baldness is frequent, especially among females, during adulthood. Their protruding lips and elastic skin around their eyes are especially conducive for animated facial expressions, an important form of communication among chimpanzees (Pankopf, 2000).
Habitat
The geographic range of the chimpanzee extends over 21 African countries. This area spreads from the west coast of Africa to as far east as Uganda, Rwanda, Burundi, and Tanzania (Goodall, 2001). Though they are the most adaptable of the great apes, the chimpanzees live in the greatest concentration in rain forests. Due to the rapid deforestation of rain forests, chimpanzees will live in savanna settings if their preferred humid, deciduous environment is unavailable (Pankopf, 2000). Due to a varied diet, chimpanzees will obtain their food from areas as varied as semideciduous and evergreen forests, grasslands, high peaks, and ridges (Goodall 1986).
Photo Courtesy of Jane Goodall Institute
Eating Habits
Chimpanzees are omnivores and will eat a wide array of foods, consisting of over 80 different types (Pankopf, 2000). Mostly they consume fruits, nuts, seeds, blossoms, and leaves, as well as insects and occasional small animals (Goodall, 2001). Sixty-percent of their diet consists of fruits and leaves, however. As observed by Tweheyo and Obva (2001), chimpanzees tend to chase away competing animals in pursuit of ripe figs. They also prefer to eat young leaves off of trees. Feeding takes place usually in the morning, and they will rest 11 to 15 hours between feedings.
Hunting Techniques
Hunting may occur individually, but more often it is a group activity. Hunting can be a sporadic event that happens upon the sight of prey, or it can be a carefully planned attack. Chimpanzees are known to hunt arboreal monkeys, bushpigs, bushback fawns, baboons, human infants, and other chimpanzee infants. When chimpanzees cooperate in a hunt, the goal is supposed to still be self-directed; they are not altruistically assisting each other in obtaining food. If one chimpanzee spots prey, he will usually try and signal other chimpanzees who are nearby with physical signs such as staring or erect hair. The chimp will look back and forth from his prey to the other chimps until the intentions are clear. Chimpanzees kill their prey by either biting into the head or neck, flailing the body so as to smash the head against an object, disembowelment, or tearing off pieces of flesh or body parts until the victim dies. Smaller prey are usually killed by eating, and since the brains are usually consumed first, the death is quick. Sometimes with larger prey, killing is more of a struggle. Chimps are not equipped with teeth sharp enough to tear skin, and they must beat larger victims to death. Sometimes the chimps lose interest in this process because it is so difficult and simply leave a badly injured victim to die (Goodall, 1986).
Photo Courtesy of Jane Goodall Institute
Communication
Many facial expressions are linked to certain vocalizations in chimps, while others are made with no accompanying sound. By manipulating the lips and teeth, chimps can express relaxation, fear or threat, distress, excitement, or play. Prolonged eye contact can express threat, but it may also be a sign of friendly expression. Tactile communication is used to express greeting, reconciliation after an aggressive occurrence, reassurance during exciting times, or fear. Social grooming is one of the most significant aspects of their social life because of the friendly nature of the physical contact. While touches can be used, as in the case of grooming, to ease tension between two chimps, other touches can be purely aggressive in nature. Auditory communications are also used, and they are always expressed in conjunction with a specific emotional state (Goodall, 1986).