ABSTRACT. Details are presented of the composition of the diet of eastern lowland gorillas, derived mainly from a study of their fresh trails and fecal analysis, during the course of an entire year in the tropical lowland forests of the Itebero region, Zaire. Gorillas ate 194 plant foods from 121 species and 45 families. They consumed 48 species of fruits; and 89~ of fecal samples contained fruit seeds, but fruits were a relatively small part (25070) of the total number of food items. The composition of their diet changed seasonally. When consumption of fruit decreased in the long rainy and the long dry seasons, the gorillas ate, in addition to Zingiberaceae and Marantaceae, many kinds of leaf and bark, which may be an important buffer against the shortage of fruits. Gorillas also fed regularly on ants (Ponerinae), and the frequency of consumption showed small seasonal variations. From a comparison of diet composition, eastern lowland gorillas appeared to be intermediate between the other two subspecies. The choice of food showed differences in preference of fruits and insects between subspecies and may reflect high similarities within subspecies in lowland and montane forests.

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ABSTRACT. Evidence was obtained that Eastern lowland gorillas feed regularly on ants in the lowland forests of eastern Zaire. The six species of ants that may have been consumed by the gorillas were identified as Ponerinae, which possess a painful sting. Gorillas consumed the ants in both rainy and dry seasons, and fragments of ants were found in fecal samples from gorillas of all age-sex classes. Field signs indicated that the gorillas search intensively ants in primary and ancient secondary forests. Such searching may stimulate the gorillas to range through various types of vegetation and, thus, it may contribute to elongation of the distances that they travel daily.

ABSTRACT. Two sticks were found near a broken bee-nest of Meliplebeia tanganyikae aft. nigrita ALFKEN in the Mt. Kahuzi region of Zaire, and were thought to have been used by a chimpanzee or perhaps several chimpanzees to dig out the subterranean nest. Honey, larvae, and most of the nest had been eaten by them. We did not find any evidence to indicate tool-use by chimpanzees in the Masisi or Itebero-Utu regions, although stingless bees were observed and honey was eaten by chimpanzees in both regions. The sticks resembled in length and diameter those known to be employed for digging termite-mounds in south-west Cameroon and Equatorial Guinea. The tool-behavior of the chimpanzees observed at Mt. Kahuzi may be similar to that of those in central Africa, rather than of those in east Africa where digging-tools have yet to be found. Another possibility is that the chimpanzees have developed the digging-tools independently, based on the need to take animal protein in the Mt. Kahuzi region, where termite-mounds are rarely observed. Instead of seeking termites, they may have a stronger motivation to seek bee larvae, especially the larvae of stingless bees beneath the ground, than to the chimpanzees inhabiting lower or drier forests.