The use of operant conditioning with positive reinforcement in order to collect urinary samples of black tufted-ear marmosets (Callithrix penicillata) kept under stable social conditions - Sgai, Manuela Gonçalves Fraga Geronymo; Zeildler, E. V; Rocha, C. G; Portella, T. P; Cottini, Ana Paola; Pizzutto, Cristiane Schilbach; Nichi, Marcilio; Guimarães, Marcelo Alcindo de Barros Vaz (International Conference on Environmental Enrichment, 2007)