KAKINUMA Miki, HAMANO Sayoko, HATAKEYAMA Hitoshi
The bulletin of the Nippon Veterinary and Zootechnical College, 52(52) 11-17, Dec 1, 2003
The degree of mother-infant contact in chimpanzees is examined and compared with the later exploratory behavior of the infants. Two pairs of chimpanzees at Tama Zoo, Tokyo,Japan are video-taped at 1,3,10 and 18 months, and the duration of close contact (mostly ventral-ventral), or contact with other parts of the body, or no contact, is timed. The exploratory behavior of the infant, as well as the mother's or sister's retrieving behavior, is also examined. Although one mother maintained close contact between herself and her baby in the first two months, the other mother encouraged the infant to interact and exercise. At 18 months, the range of exploratory behavior differed. The first child remained close to its mother or elder sister, and exhibited little exploratory behavior. Even when the child tried to explore, the elder sister kept retrieving it. The other child interacted with adults and children in the group, and played with many toys and tools available. The mother stayed close to the second child but did not prevent it from exploring. Both infants have an elder sister at the same zoo, and they also exhibit similar differences in exploration and other social behavior. Individual differences in chimpanzee cognition have been often pointed out, both in wild and in captive animals. Parenting style may be one of the factors in creating these differences, apart from innate ones.