Ethological and experimental investigations of tool use have been explored across a wide range of mammalian and avian species, with the extensive review by Beck (1980) still the penultimate volume. The initial field observations of tool use in wild chimpanzees (Pan troglodytes) came from the pioneering work of Goodall (1964, 1968), and were followed by meticulous reports from McGrew (e.g., 1974, 1987; Brewer & McGrew, 1990; for overview, see 1992), detailing two different types of tool use, including termite-fishing and ant-dipping. Subsequent observations of tool use, modification, and transport, including stone tool use by chimpanzees, have provided a window toward understanding cultural transmission among populations of chimpanzees now isolated throughout eastern and western Africa (Boesch & Boesch, 1990; McGrew, 1992; Matsuzawa, 1994). As numerous field workers continue to collect long-term data and behavioral observations of wild chimpanzee populations, new tool types and functions are regularly reported (Sugiyama, 1985, 1995; McGrew, 1992; Suzuki, Kuroda, & Nishihara, 1995; Yamakoshi & Sugiyama, 1995).

The rich archival literature now available on primate tool use, particularly for chimpanzees, coupled with increased awareness of the positive effects of environmental enrichment for captive primates, have resulted in a wide range of creative and innovative efforts at providing captive great apes opportunities for tool use in both zoo and laboratory settings. Despite this history of research, opinions of what can be classified as a tool or tool use vary. In accordance with Goodall (1970), Parker & Gibson (1977), and, more recently, Boesch & Boesch (1990), the present study defines a tool as an object that is held in the hand, foot, or mouth and employed in a functional manner that enables the user to attain a specific goal.