Oral tool use by captive orangutans (Pongo pygmaeus)

Eight captive orangutans (Pongo pygmaeus) were given wooden blocks embedded with raisins and bamboo as raw material for tool making in a study of manu al laterality. In about three quarters of the raisin extraction bouts, the orangutans held the tool in the lips or teeth rather than in their hands. T hree adult males and 2 adult females showed extreme (greater than or equal to 92%) preference for oral tool use, a subadult male and an adult female u sed oral tools about half the time, and 1 adult female preferred manual too l use. Most oral tool users made short tools (approx. 4-10 cm long) that we re held in the lips and (probably) supported by the tongue. Preference for oral tool use does not correlate with body weight, age or sex, but it may b e related to hand size or individual preference. This is the first report o f customary oral tool use as the norm in captive orangutans; it resembles t he behavioral patterns reported by van Schaik et at. and Fox et al. in natu re.