Abstract
Wild and captive chimpanzees feed on fruits and terrestrial plants by wadge-making technique. Few reports on wadge-making behaviors by wild orang-utangs are found. Pickford (2005) found that the relative large sizes of incisors of chimpanzees is adapted to their frequent meat eating by comparison on fossil and living great apes and fossil humans.
The aims of this paper are the following four; (1) intra-specific differences on wadge-making behaviors between chimpanzee and oran-utang, (2) sexual deference in those species, and (3) age-dependent development in wadge-making behavior. We fed experimentally sugar canes to the captive animals and collected their individual wadges. Fourthly, new findings on wadge-making behaviors by Japanese monkeys are reported.
In chimpanzees sexual and age-dependent differences were not found. Orang-utangs are better in the efficiency in wadge-making behavior than that in chimpanzees.
In 2005 winter, new wadges made by wild Japanese monkeys were found in the Hinohara village, Tokyo. They fed on the invaded weed species by making wadges in the artificial slopes.
