Utilization patterns of a marsh grassland within the tropical rain forest by the bonobos (Pan paniscus) of Yalosidi, Republic of Zaire

Abstract

The bonobos of Yalosidi, Ikela zone, near the southeastern limit of the range of this species, make regular visits to a marsh grassland known locally as Iyoko (or Yoku) within the tropical rain forest. They come to the marsh to feed on the fibrous vegetative organs of particular species of aquatic or amphibious herbs and grasses, especially those of the families Alismataceae and Cyperaceae. During fixed point observations at Iyoko between September 1975 and January 1976, seasonal changes were recognized in the party size, attendance rate, and arrival time of the bonobos, while no conspicuous change was observed in the composition and phenology of their food plants. The size of the bonobo parties appeared to be an important factor in determining the duration of stay at the marsh per visit. Throughout the study period with the exception of January, they intensively utilized a particular portion of Iyoko, in which their preferred food was scattered. Iyoko was also utilized frequently as a stable feeding place by other large forest herbivores such as elephants, buffalos, bongos, sitatungas, and duikers. In contrast, various species of cercopithecid monkeys commonly seen in the surrounding forest were never observed to enter Iyoko for foraging. This suggests a comprehensive use of the habitat by the Yalosidi bonobos compared with the more limited ecological niches of other sympatric non-human primates.