Abstract # 213:

Scheduled for Monday, September 21, 2009 11:45 AM-11:55 AM: Session 22 (Mission Bay Ballroom AB) Oral Presentation


LONGITUDINAL CASE STUDY OF NUT-CRACKING IN A JUVENILE BEARDED CAPUCHIN MONKEY (CEBUS LIBIDINOSUS): STAND FOR SUCCESS

Q. Liu1, A. M. Salvatori2, D. Fragaszy1, P. Izar2, E. Ottoni2 and E. Visalberghi3
1University of Georgia, Department of Psychology, Athens, GA 30602, USA, 2Department of Experimental Psychology, University of Sao Paulo, Sao Paulo, CEP 05508-030, Brazil, 3Unit of Cognitive Primatology and Primate Center, Institute of Cognitive Sciences and Technologies, CNR, 00197 Rome, Italy
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Our aim is to describe changes in nut-cracking in one wild male bearded capuchin monkey filmed opportunistically at 17-mo, 30-mo and 41-mo (12 to 30 episodes per period). We coded frequency of relevant actions in nut-cracking and, with part of the dataset, kinematic variables. At 17 months, he generated a low variety of behaviors, struck only small pieces of nuts with correct actions sequences, 42% in a sitting position. At 30 months, compared to 17 mo, he used heavier stones [Χ2=6.22, p<0.05], generated a greater variety of behaviors, and attempted to crack whole nuts. He “sat” in only 7% of episodes. When he stood to crack, he extended the trunk to a maximum of 71º and the knee to a maximum of 129º, and lifted the stone higher than when he sat (0.20 vs. 0.34 m, 3 episodes each). At 41 months, he stood in all episodes, with maximum trunk extension reaching 78º and maximum knee extension 124º, similar to the adults. He cracked a higher proportion of nuts compared to 30 months, including some whole nuts (Χ2=2.78, p=0.06]. Analysis of downward striking durations indirectly revealed that he added force to the stone during striking in 2008, but not in the previous two years. This monkey mastered action sequences years before he mastered the kinematic challenges of cracking (posture, balance, force).