Effects of early rearing conditions on problem-solving skill in captive male chimpanzees (Pan troglodytes).

Naruki Morimura, Yusuke Mori


Early rearing conditions of captive chimpanzees characterize behavioral differences in tool use, response to novelty, and sexual and maternal competence later in life. Restricted rearing conditions during early life hinder the acquisition and execution of such behaviors, which characterize the daily life of animals. This study examined whether rearing conditions affect adult male chimpanzees' behavior skills used for solving a problem with acquired locomotion behavior. Subjects were 13 male residents of the Chimpanzee Sanctuary Uto: 5 wild-born and 8 captive-born. A pretest assessed bed building and tool use abilities to verify behavioral differences between wild- and captive-born subjects, as earlier reports have described. Second, a banana-access test was conducted to investigate the problem-solving ability of climbing a bamboo pillar for accessing a banana, which might be the most efficient food access strategy for this setting. The test was repeated in a social setting. Results show that wild-born subjects were better able than captive-born subjects to use the provided materials for bed building and tool use. Results of the banana-access test show that wild-born subjects more frequently used a bamboo pillar for obtaining a banana with an efficient strategy than captive-born subjects did. Of the eight captive-born subjects, six avoided the bamboo pillars to get a banana and instead used, sometimes in a roundabout way, an iron pillar or fence. Results consistently underscored the adaptive and sophisticated skills of wild-born male chimpanzees in problem-solving tasks. The rearing conditions affected both the behavior acquisition and the execution of behaviors that had already been acquired.


rearing condition, problem-solving skill, cognitive task, chimpanzees