Reinhardt, V. 2008. Taking Better Care of Monkeys and Apes. Animal Welfare Institute, Washington, DC.

It is documented in professional and scientific journals that housing and handling practices of caged nonhuman primates can be refined, without undue labor and expenses, in such a way that distress responses are minimized or avoided if basic ethological principles are applied: (1) address the animal's need to be with and interact with at least one compatible conspecific; (2) structure their living quarters in species-appropriate ways; (3) address their biologically strong motivation to forage; (4) train them to cooperate during procedures.