Effect of environmental enrichment on the behavior of great apes - Pizzutto, Cristiane Schilbach; Nichi, Marcilio; Sgai, Manuela Gonçalves Fraga Geronymo; Corrêa, S. H. R; Nunes, A. L. V; Pessutti, C; Beresca, Ana Maria; Barnabé, Renato Campanarut; Guimarães, Marcelo Alcindo de Barros Vaz (International Conference on Environmental Enrichment, 2007)