Understanding of causality involved in tool use by tufted capuchin monkeys
Date:2007/08/14 - 2007/08/24
I presented a poster entitled "Substrate choice in nut-cracking behavior of semi-wild tufted capuchin monkeys (Cebus apella)", jointly authored with S. Tsutsumi, Y. Morimoto (Kyoto University), C.G.Coelho, T. Falóticoco, E.B. Ottoni (University of São Paulo) on August 20. This poster received much attention of the audience. I also discussed future research with our collaborator, Dr. Ottoni. The abstract is below. Semi-wild tufted capuchin monkeys (Cebus apella) at the Tiete Ecological Park, São Paulo, Brazil, are known to crack open small Syagrus palm nuts placed on the hard substrate by hammer stones. We tested whether the monkeys knew substrate conditions necessary for successful nut-cracking. Specifically we placed side by side two types of artificial substrates, one made of cement blocks and the other made of soft rubber, on the ground of an open lot where the monkeys frequently use for this feast. A natural hammer, which they routinely use, and dozens of palm nuts were located between the anvils. The experimental observation was conducted opportunistically. During the observation period, 4 males and 7 females attempted to crack open nuts at the experimental site. All were more or less skilled crackers. All of the individuals observed chose the hard substrate from their first attempt with the novel substrates. Thus the monkeys seem to appreciate the hardness of the substrate as an important condition for success.