Gombe Stream National Park
Chimpanzees feed for about six hours every day. They spend about 50-70% of that time eating fruit, about 20% eating leaves, and the remainder on a variety of other things-seeds, flowers, pith, bark, stems and resin. Nor are they only vegetarians; at certain times of year they eat a lot of insects, and they are opportunistic hunters of bird eggs and nestlings, and of small to medium-sized mammals.
They seem to like variety; they have been seen to eat 147 different plant species at Gombe. On average a chimp may eat 40-60 of these per month. However, they are conservative and do not readily try new things. This implies that their knowledge of what is edible is passed on from mother to infant; infants readily try new foods, but are often prevented by their mother from eating them. Chimps in different areas do show important cultural differences in their diet and feeding behavior, just as we humans do!
In spite of all this variety, chimps do tend to concentrate on a few major food crops during the year, and if you understand this cycle it may help you to find chimps. Perhaps the most important chimp food is palm-nuts, for these are a concentrated high-energy food available all year round. Thus, it is always worth looking in the tops of palm trees, where one or two chimps may sit very quietly for a long time.
In November, at the start of the rains, chimps "fish" for termites, wherever there are mounds. Also coming into season are the sour orange berries of a tree (Garcinia) and the warty lemon-like fruits of a vine (Saba florida), both found in forest.
In January to March, the middle of the rains, chimpanzees often join together in large groups in evergreen forest to eat the fruit of a vine (Dictyophleba lucida), and they may stay in the vine thickets for days at a time eating little else.
In April and May, the end of the rains, chimps feed partly in the forest (small orange berries of the shrub Monanthotaxis poggei, fruits of vine Uvaria angolensis) but also move into more lightly wooded slopes to eat the sticky milky pods of Diplorhynchus and the yellow flowers of Pterocarpus.
In June to October, the dry season, chimps range far and wide through wooded grassland, eating Diplorhynchus, the sweet brown fruit of Parinari, and on higher ridges and slopes, the pods of Brachystegia. Occasionally they return to riverine forest to make increasing use of figs, palm nuts, and the small green clustered fruits of a forest tree Pseudospondias. Then in November termite season starts with the rains, and the cycle continues.
The flexible grouping pattern within a chimp community seems geared to an environment where food sources are often widely scattered and too small to feed a large troop of apes traveling together. Their intelligence helps them make best use of this complex environment. Studies suggest that chimps have a very detailed"mental map" of their environment; that they know accurately where they can find food at any time of year, and that they know the position of individual food trees so well that they can head straight to them through trackless, viewless thicket. Also, complex behavior such as tool use and hunting give chimps access to extra sources of high-quality food.
Chimpanzees also eat certain plants for their medicinal value, a habit which has not yet been observed in any other creature except mankind. Occasionally when chimps get up in the morning, they will seek out one of two species of Aspilia, a herb with a yellow daisy-like flower (Kiha name is "Mitati"). They eat just a few leaves of this, slowly but without chewing, before moving on to feed in earnest on other foods. These same Aspilia species are used medicinally by local people, and analysis has shown their leaves to contain a powerful antibiotic and worm-killer.
Special Thanks to Thomson Safaris and Tanzania National Parks for contributing Tanzanian information.
Details mentioned in this article were accurate at the time of publication