HAND PREFERENCE AND TOOL USE IN WILD CHIMPANZEES

The hand preference of chimpanzees in their natural habitat was studie d at Bossou, Republic of Guinea, West Africa. The quantitative differe nce in left/right hand use was small in food picking and carrying. In contrast, the chimpanzees employed either the right or left hand in nu t-cracking behavior using a pair of stones. All adults and many adoles cents and juveniles utilized one hand exclusively for holding a hammer stone. Left hand preference was more prevalent among adults. However, when adolescents and juveniles were included, there was no significan t bias in the ratio of left/right handers. Nut-cracking behavior requi res long-term learning of the fine manipulation of stones and nuts by both hands. Each hand has a separate role, and the hands work together in nut cracking. The differential and complementary use of both hands may be a prime factor promoting exclusive hand preference in chimpanz ees comparable to that of humans.