Equatorial Africa contains a multitude of landscape ecosystems including multi-strata tropical forest, dry deciduous forest, woodland, mosaic grassland forests, savannah woodlands, savannah, and desert. The robust chimpanzee has adapted to living in a variety of these habitats, including mosaic grassland forests, savannah woodlands and tropical moist forests. Chimpanzees also occur at altitudes ranging from sea level to around 2,899m in elevation. The tropical zone of Africa is reported to be drier than the tropical zones of Asia and America. Only a few regions receive more than 2500mm of rainfall per year. Many of these forests lie close to the equator and therefore receive two rainy and two dry seasons per year. It is suggested that the forests of Africa were fragmented by dry forests or woodland prior to human clearing activities. This is one possible explanation for the adaptive nature of chimpanzees, as evidenced by their ability to utilize these drier forests. These habitats are marginal habitats for chimpanzees as sourcing water can limit the ability of chimpanzees to survive in such habitats.
Feeding behaviour in chimpanzees varies seasonally and is greatly influenced by food availability and habitat type. The feeding repertoire of chimpanzees over their range shows many differences, some of which cannot be explained by variation in their biotic environments. They reflect traditional and possibly cultural variants between communities. There are also differences in food processing techniques and the use of plants for self-medication purposes.
Chimpanzees are omnivorous and have a diverse diet. Fruit usually comprises the largest portion of their diet but they are also known to eat flowers, bark, roots and tubers, tree gum and insects such as adult termites (Isoptera sp.), ants (Dorylus sp. and Oecophylla longinoda), and the larvae and eggs of ants, bees and several species of beetles such as the Raphia coleopteran and RhynchoÂphorus quadrangulus.
Different communities vary in the diversity of their dietary repertoire and the proportion of low-quality foodstuffs they consume. They also incorporate different insect prey into their diet, with some being ignored at some sites while consumed at others.
Hunting by chimpanzees is usually confined to males and prey is usually captured opportunistically. They prey on duikers, young bushbuck, baboons and other monkeys. However, these same species can often be seen near chimpanzees that ignore them. Attacks are usually quick and well coordinated and generally successful. Intense excitement is often evident during hunts followed by intense competition for the spoils, as usually, there is not enough to be shared, with the killer having full rights to the meat and the remainder chimpanzees begging. Infanticide by adult males has also been observed with the infants being eaten.
Like people, chimpanzees communicate in various ways. They communicate with body language (positions and gestures), facial expressions and vocalizations. There are intraparty calls (calls among chimps that are in a group together) and distance calls (calls made between groups that are separated, sometimes over a great distance). Below are some calls that chimpanzees make and the emotions that go with them.
Table 1: Chimpanzee Calls
|Soft Bark, or cough
|Food-grunt or food “aaa” call
|Rage or distress
|Laugh, lip-smack, pant
The food calls, a mixture of food grunts, barks and pant hoots, alert other chimpanzees to the whereabouts of food sources. A special intensity of excited calls of this type indicates that there has been a successful kill after a hunt.
Each individual has his or her own distinctive pant-hoot, so that the caller can be identified with precision.
A loud, long, savage-sounding wraaaa call is made when a chimpanzee comes across something unusual or dangerous.
When young chimpanzees play, they emit breathy laughter.
Soft grunts uttered by foraging or resting chimpanzees probably serve to maintain communication within the group.
Posture, gestures, and facial expressions communicate many messages and emotions within a group. When greeting a dominant individual after an absence or in response to an aggressive gesture, nervous subordinates may approach with submissive signals – crouching, presenting the rump, holding their hand out, accompanied by pant-grunts or squeaks. In response, the dominant individual is likely to make gestures of reassurance, such as touching, kissing, or embracing the subordinate.
Friendly physical contact is crucial in maintaining good relationships among chimpanzees. For this reason, social grooming is probably the most important social behaviour, serving to sustain or improve friendships within the community and to calm nervous or tense individuals.
The grin of fear seen in frightened chimpanzees may be similar to the nervous smiles given by humans when tense or in stressful situations. When angry, chimpanzees may stand upright, swagger, wave their arms, throw branches or rocks – all with bristling hair and often while screaming or with lips bunched in ferocious scowls.
Male chimpanzees proclaim their dominance with spectacular charging displays during which they slap their hands, stamp with their feet, drag branches as they run, or hurl rocks. In doing so, they make themselves look as big and dangerous as they possibly can, and indeed may eventually intimidate a higher-ranking individual without having to fight.
Table 2: Chimpanzee Facial Expressions
|Grin with mouth closed or slightly open
|Associated with submissive behaviour and fear
|Grin with open mouth (b)
|Non-aggressive physical contact with other chimpanzees; when threatened by a superior or another species that the chimpanzee fears
|Open-mouth threat. Mouth open, teeth covered by lips, glaring
|Threatening subordinate, distant subordinate, or another species that is feared very little
|Tense-mouth face. Lips pressed tightly together, glaring
|Prior to, or during chase/attacks upon subordinates and prior to copulation
|Pout face (e)
|Situations of anxiety or frustration, detecting strange objects, begging, infant searching for mother, after threat or attack
|Play face (c)
|During playful physical contact with other individuals
|While grooming another chimpanzee
Chimpanzee Facial Expressions supporting graphic