Larger cages with housing unit environment enrichment improve the welfare of marmosets.

The provision of adequate space for laboratory animals is essential not only for good welfare but accurate studies. For example, housing conditions for primates used in biomedical research may negatively affect welfare and thus the reliability of findings. In common marmosets (Callithrix jacchus), an appropriate cage size enables a socially harmonious family environment and optimizes reproductive potential. In this study, we investigated the effects of cage size on body weight (BW), behavior, and nursing succession in the common marmoset. Large cages (LCs) with environment enrichment led to an increase in BW while small cages (SCs) caused stereotypic behaviors that were not observed in LCs. In addition, the BW of infants increased with aging in LCs. Our findings indicate that the welfare of marmosets was enhanced by living in LCs. Research on non-human primates is essential for understanding the human brain and developing knowledge-based strategies for the diagnosis and treatment of psychiatric and neurological disorders. Thus, the present findings are important because they indicate that different cages may influence emotional and behavioral phenotypes.