Improving Welfare Through Enrichment: A Case Study in Aged Ex-Laboratory Rhesus Macaques

Rhesus macaques (Macaca mulatta) are among the most commonly used non-human primates in biomedical research, and those retired to sanctuaries often arrive after many years of barren laboratory housing that can compromise their behavioural and psychological welfare. This case follows three aged males (two aged 20 years and one aged 28) relocated in June 2021 from a university laboratory to the Animanatura Wild Sanctuary (Semproniano, Italy), managed by Lega Anti Vivisezione (LAV). The sanctuary and veterinary teams designed a structured, novel feeding-enrichment programme and assessed its impact using a multidisciplinary welfare-monitoring protocol that combined behavioural observation with a non-invasive physiological measure. Behaviour was recorded from video using continuous focal sampling and coded against an ethogram; faecal samples were analysed for cortisol metabolites. The programme followed three phases: a pre-treatment control phase, a treatment (enrichment) phase, and a post-treatment control phase. Compared with baseline, the macaques showed increased locomotion, reduced resting, lower rates of scratching and body-shaking, and lower faecal cortisol concentrations following the enrichment programme. Object manipulation and abnormal behaviours did not change significantly, partly because the latter were very rare from the outset. The case illustrates how enrichment can be used as a practical rehabilitation tool to enhance welfare in captive aged primates, and how behavioural and physiological indicators can be combined to evaluate its effectiveness.