Chopped and dispersed food enhances foraging and reduces stress-related behaviours in captive white-naped mangabeys (Cercocebus lunulatus)

Abstract

The white-naped mangabey is an endangered and rare zoo species, yet little is known concerning their welfare in captivity. The assessment of welfare should incorporate a net balance of negative and positive welfare behavioural indicators. These behaviours, and thus welfare, can be affected by the way food is presented based on its distribution, clumped or dispersed, and its size, chopped or whole. This study investigated the effect of food presentation on time-budget behaviours (i.e. forage, activity, inactivity, allogroom, self-groom, play) and stress-related measures (i.e., diarrhoea, aggression, self-directed behaviours), in four crossed-over test conditions of food distribution. The group-living mangabeys of Rotterdam Zoo were provided with vegetables that differed in distribution and size: clumped-chopped, dispersed-whole, dispersed-chopped, and clumped-whole. Mangabeys spent least time being inactive and subordinates and juveniles spent most time foraging during the dispersed-chopped condition, while the reversed was found during the clumped-whole condition. In addition, mangabeys stole food more often and engaged in less self-directed behaviours during dispersed-chopped, compared with dispersed-whole. In contrast, food distribution and size did not affect aggression, play, activity, self-grooming and diarrhoea. Consistent with most of the literature, chopped, dispersed items appeared to be the best, whereas presenting whole food items appeared to be the worst for welfare. In conclusion, presenting food in a distributed and chopped instead of whole manner is suggested to improve welfare of zoo-housed mangabeys.