The data obtained from field studies in 1987 at Bossou, Guinea, Kala Maloue National Park and Campo Animal Reserve, Cameroon have been analyzed and partly published. Summary of the result in each study area was described below.
Guinea team studied on population dynamics, tool-using behavior, sexual behavior, and other social behaviors of wild chimpanzees at Bossou, near Guinea-Liberia border. The group of chimpanzees have been studied since 1976 without artificial feeding, so that the long term data are available. New data on population dynamics was given through the death of a young male chimpanzees. Some other cases of natural death of the chimpanzees of the group in the past were clarified. The body size of the dead chimpanzee was smaller than that of reared chimps in the same age. Experimental and observational studies on tool-using, oil-palmnut cracking with natural stone hammers and anvils, revealed flexibility and optimality in the behavior: the chimps easily use substitutable ma
terials (woods) when stones were not available; they conveyed both stones and palm-seeds; they preferred particular size of stones and particular oldness of palm-nuts; the role of stones was not fixed. We also recorded the use of secondary (meta) tool and the traces of ant dipping which had not been recorded in the Bossou chimps. Our study revealed chimpanzee's high ability of recognition supporting various tool-using behavior, and suggested fruitful result by linking ecology with psycology. Our study on sexual behavior focused on the relationship between female sexual cycles and the number of males. The estorus cycles of female chimpanzees were synchronized when males were sufficient, and not when insufficient. Adaptational switching according to the amount of male resources was suggested. The analysis on the cause for chimpanzee fission-fusion are now undergoing. It will be clarified the relation between fission-fusion and food availability; role playing and social contexts, and so on.
Comparative feeding ecology of monkeys living in the savanna-grassland in Kala Maloue was carried out for patas monkeys (Erythrocebus patas) and savanna monkeys (cercopithecus aethiops). These savanna adapted species were revealed to be different in feeding and ranging behavior as follows. Patas monkeys ranged mainly in grassland, home range was about 6 km^2, and daily travel distance was about 6 km during dry season. On the contrary, savanna monkeys ranged mainly in riverine forest, sometimes in grassland. Home range was only about 1 km^2, and daily travel distance was about 2 km. Both species fed mainly on fruits of several woody plant, seeds, flowers and gum of Acacia trees. In addition, patas monkeys ate insects (e.g., grasshoppers, weevils and lavaes of unidentified insects) as well as meet (chickens, lizards). On the other hand, savanna monkeys sometimes ate insects but hardly did meet. Instead of this, they fed on blades of several herbaceous plant at riverside. These differences in thier diet may affect the protein intake in the two species. As a result, larger protein intake of patas monkeys may enable them to breed in dry season.
Social structure and tool-using behavior of chimpanzees were studied of Campo through artificial feeding since 1985. Some chimpanzees could be observed from inside of the blind at the artificial feeding site during this study period. Most of chimpanzees which came into the feeding site were alone or in small parties of two individuals, occasionally four or more, nine in maximum, containing both sexes of adults and immatures. Sugiyama reported tool-using behavior of chimpanzees in Campo Reserve in 1985. In this study, additional data on the characteristics of termite mound digging sticks were collected. The frequency and the seasonality of termite digging was also studied. Several species of plant seemed to be chosen as the material of digging sticks, and the frequency of termite digging behavior was very low. Less