Sex Differences in Chimpanzee's Use of Sticks as Play Objects Resemble Those of Children

After fourteen years of observation of a Kanyawara chimpanzee community in Uganda, researchers conclude that chimpanzees use sticks in four ways: to investigate holes that might contain water or hone, as weapons, during solitary or social play, and in a behavior termed "stick-carrying," which consists of cradling a stick for periods of one minute up to four hours. Stick-carrying represented 38.9% of all recorded stick use observations and 10% of all object use observations.

Stick-carrying does not appear to have any discernible function, but it does appear more frequently among juveniles and females. The use of sticks as a weapon occurred more frequently in males than females, as did the use of leaves by adults for wiping their bodies.

Researchers suggest that sex differences in stick-carrying are related to the female's interest in infant care, with this behavior representative of mothering behavior. In instances where adults females were observed carrying sticks, the behavior always occurred before giving birth for the first time. In addition, carried sticks were regularly taken into day-nests where individuals were seen to play with them in a maternal manner. Finally, the capacity for young chimps to direct care toward objects has been seen previously in apes raised by humans.