Published online by Cambridge University Press: 11 January 2023
Provision of adequate space for captive animals is essential for good welfare. It affects not only their behaviour but also determines whether there is sufficient room for appropriate environmental enrichment. Most importantly, appropriate cage size permits captive animals to be housed in socially harmonious groups and to fulfil their reproductive potential. For animals used in the laboratory, the environment can be an additional source of suffering and distress. If they can be better housed and cared for to reduce the overall impact of experiments upon them, then we are obliged to do so for ethical, legal and scientific reasons. Practically all current guidelines specify minimum cage sizes for laboratory primates based on unit body weight. We believe that no single factor is sufficient to determine minimum cage sizes for primates, and that instead a suite of characteristics should be used, including morphometric, ecological, social and behavioural characteristics. Here we explore the relevant differences between tamarins (Saguinus labiatus and S. oedipus) and marmosets (Callithrix jacchus) that have a bearing on setting minimum cage sizes. These include: body size; arboreality and cage use; home range size, mean daily path length and stereotypic behaviour; breeding success in the laboratory; and species predisposition and aggression. We conclude that it is even more important to provide tamarins with a good quantity of space in the laboratory than it is marmosets if well-being and breeding success are to be maximised.