Behavioural Time Allocation and Responses to Environmental Enrichment in Zoo-Housed Yellow-Breasted CapuchinMonkeys [Sapajus xanthosternos]

Understanding how environmental enrichment influences behavioural time allocation is particularly important for threatened primate species maintained under human care. Accordingly, we investigated whether environmental enrichment [EE] influences behavioural time allocation in yellow-breasted capuchin monkeys [Sapajus xanthosternos], aiming to inform evidence-based husbandry practices in zoological settings. Employing the standard ethological approach of behavioural coding, we observed 20 capuchins housed in three groups comprising adult and juvenile males and females. We recorded behavioural categories including: aggressive, exploratory, affiliative/play, general activity, alert, inactivity, and abnormal behaviour. To evaluate individual engagement with EE, we applied the ABA paradigm, wherein phases A1 and A2 [controls] represented standard zoo conditions, while phase B corresponded to the implementation of an EE programme. Each phase spanned 10 days, and behavioural data were collected via focal animal sampling [2 ×[M1] [SN2] 10 min focal sessions per animal per day], resulting in a total of 1200 focal sessions. Behavioural time allocation was analysed using a multivariate generalized linear mixed modelling approach that accounted for the interdependence among behavioural categories. Based on previous studies, we predicted that environmental enrichment may promote higher levels of play and exploration and lower aggression and inactivity. However, despite by-eye suggestions of increases in play and decreases in activity during enrichment, when behavioural categories were analysed simultaneously within the multivariate framework, overall behaviour time budgets and behavioural diversity were found not to change significantly across experimental phases. There were also no sex or age effects on behaviour. This indicates that for S. xanthosternos, the enrichment protocol used here did not provide sufficient novelty or complexity to alter established activity patterns. Integrated analytical approaches are needed to further evaluate the effectiveness of enrichment strategies to ensure they are tailored to specific cognitive and social needs of complex species; future studies could explore how social dynamics, enclosure design, and environmental complexity interact to shape behavioural responses to enrichment.[