Bwindi is the only place on Earth where chimpanzees share the same habitat as mountain gorillas. However their niches are very different with little overlap and no interactions between them have been recorded.
Chimps were about 860 in Bwindi in the late 1990s but only 300–400 ten years later. Adults of both sexes can weigh 45kg/100lb, though females may be only 30kg/66lb.
Chimpanzee social structure is markedly different from other primates, being communities of individuals who share a range and freely join or split.
Males remain in their natal community, while females tend to emigrate. Mothers can form matrilineal groups with their offspring and, sometimes, grand-offspring. Group size varies from one to 40, the latter during food abundance or whenever females are in oestrous.
Both sexes take defensive duties, but males are the principal defenders of the community’s range against neighbouring groups. Females become sexually mature at 11–13 years and advertise oestrus with a prominent pink perineal swelling. They may mate with many males though not necessarily during oestrus. Gestation is eight months and birth intervals are around every five years. Mothers invest more time, up to seven years, in raising infants and transmitting learned behaviour.
Chimpanzees travel long distances easily, usually on the ground, over a large home range of around 10km²/3.8mi². They focus on patches with valuable high-energy food, such as the wild fig (85% of their diet), mostly in the middle and top layers of canopy forest. It used to be thought that chimpanzees were vegetarian but part of their diet is also different mammals, such as monkeys and duikers, and abundant insects— harvested or extracted with twig tools.
Chimpanzees don’t have specific nesting places and nightly make new nests with flexible branches bent into a dishshaped platform and lined with leaves. These are very similar to gorillas’ nests and are told apart by their faeces, which they both deposit sometime during the night.
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