Adrian Barnett is an Honorary Research Fellow at the Instituto National de Pesquisas da Amazonas in Manaus, Brazil, and at the Centre for Research in Evolutionary and Environmental Anthropology at Roehampton University. He is a tropical biologist whose research focuses on rare, little-known and hard-to-find species and has spent fifteen years studying tropical primates, particularly the conservation and ecology of uacaris. Liza M. Veiga is a postdoctoral fellow at the Federal University of Pará and the Emílio Goeldi Museum, both in Belém, Brazil. Her research focuses on the conservation biology of the genus Chiropotes, Brazil. Stephen F. Ferrari is a Professor of Zoology in the Biology department of the Federal University of Sergipe, São Cristovão, Brazil. While his research covers a wide variety of mammalian taxa, he has a particular focus on the primate genera Callicebus and Chiropotes, their ecology and conservation. Marilyn A. Norconk is Professor of Anthropology at Kent State University, Kent, OH, USA. Her research focuses on behavioral ecology of South American monkeys, particularly feeding ecology and social behaviour of white-faced sakis and bearded sakis in Venezuela and Suriname.