Intelligent tool use in wild Sumatran orangutans

摘要: INTRODUCTION Until recently, there was limited evidence of tool use ( sensu Beck, 1980) by wild orangutans Pongo pygmaeus ), and no manufacture, despite several long-term field studies in Borneo (Ulu Segama: MacKinnon, 1974; Tanjung Puting: Galdikas, 1982; Kutai: Rodman 1973; Mitani 1985; Suzuki, 1989; Gunung Palung: et al., 1991) Sumatra (Ketambe, Leuser: Rijksen, 1978; Sugardjito 1986; Utami & Mitrasetia, 1995). Orangutans had been observed using only “found objects” as tools (Byrne, 1995): simple, unmodified raw materials such leaves to wipe off feces (MacKinnon, 1974), a pad for holding spiny durian fruit (S. Utami, personal communication), leafy branch bee swatter (E. Fox, observation), bunch branches held together an “umbrella” while traveling the rain (Rijksen, E. single stick backscratcher (Galdikas, 1982), or tree trunk missile (all studies). Because observations flexible behavior primates chimpanzees Pan troglodytes it often suggested that manufacture arose chimpanzee–hominid clade (McGrew, 1992, 1993). Such inconsistent with captive orangutans. In contrast their counterparts, rehabilitant demonstrated rich array behavior, at least complex under similar conditions (Lethmate, Russon 1993, Why did demonstrate remained relatively unsophisticated?