Abstract # 51:

Scheduled for Saturday, September 13, 2014 07:00 PM-09:00 PM: Session 11 (Decatur B) Poster Presentation


D. M. Fragaszy1, K. Smith1, R. Baldree1 and M. Haslam2
1University of Georgia, Department of Psychology, Athens, GA 30602, USA, 2Oxford University
     Skill is defined as fluid, effective performance under variable circumstances. Wild bearded capuchin monkeys habitually crack hard nuts by placing them on an anvil and striking them with stone hammers. Previous studies at the EthoCebus field site in Brazil have shown that monkeys are skillful in aspects of nut-cracking including stone and nut selection, placing the nut on the anvil, and producing appropriate striking force. We asked if monkeys handled the hammer stone skillfully during nut-cracking. Four adult monkeys were videotaped voluntarily cracking nuts using two stones (1042 gm, moderately asymmetric and 1100 gm, more symmetric). A 3-D digital reconstruction was made of each stone. For each strike, from video playback we coded nut striking behaviors, accuracy, and the location on the stone that struck the nut. For each stone, at least 14 and up to 20 strikes by each subject were analyzed. All four monkeys struck straight down onto the nut on 90% or more of strikes. The hands moved to the top of the stone during the downward strike. Each monkey struck the nut within 2 cm of the asymmetric stone’s center of mass on 81% of strikes on average. The findings indicate that bearded capuchin monkeys adjust their grips and their actions to achieve consistently accurate strikes. Supported by the European Research Council, the National Geographic Society, and the University of Georgia.