Current Biology, Volume 19 Supplemental Data Selection of Effective Stone Tools by Wild Bearded Capuchin Monkeys Elisabetta Visalberghi, Elsa Addessi, Valentina Truppa, Noemi Spagnoletti, Eduardo Ottoni, Patricia Izar, and Dorothy Fragaszy Supplemental Procedures Study Area Our field site was located at Fazenda Boa Vista in the southern Parnaíba Basin (9°39’ S, 45°25’ W) in Piauí, Brazil. It is a flat open woodland (altitude 420 m asl) punctuated by sandstone ridges, pinnacles and mesas rising steeply to 20-100 m above it [1]. Subjects Subjects were five adult males, two adult females and one juvenile male. Their weights, collected four months before the present study, ranged between 3540 g (largest adult male) and 1780 g (juvenile male). Subjects belonged to a group of 19 monkeys (Chicao group), composed of five adult males, five adult females, four juveniles, and five infants (two of which were born during the present study, one of them to Dita, one of our experimental subjects). Our sample included all the nut-cracking capuchins of the group except Teninha, a subordinate adult female that never approached the experimental area. The Chicao group was provisioned in the experimental area with water and some food (approximately 700 Kcal per day for the entire group). Although capuchins were