Animals are confronted with potential stressors at zoos compared to in the wild, such as visitors and lack of environmental stimulation. This study included two projects conducted on the drills at Parken Zoo in Eskilstuna where I investigated: 1) the effect of visual barriers on the behaviour of the drills and if the visual barriers can moderate the visitor effect on the drills and 2) how outdoor-only access together with feeding enrichment (frozen fruit and tube feeders) affects the behaviour of the drills. 1/0- sampling method was used when observing the behaviours of the drills with 1 minute-intervals. Resting/Sleeping increased, while social agonistic behaviour and stereotypies decreased with visual barriers. A moderated visitor effect was shown in resting/sleeping and social affiliative behaviour in the drills with visual barriers. However, social agonistic behaviour and visitor interaction were still affected by visitors after the installation of the visual barriers, implying that the drills still find visitors stressful to some extent and that further alterations on the observation area viewing the indoor enclosure is recommended for the welfare of the drills. With outdoor-only access together with feeding enrichment, locomotion, foraging/eating and body-shaking increased, while resting/sleeping, social affiliative and agonistic behaviour, stereotypies, visitor interaction, scratching and self-grooming decreased. This suggests that outdoor-only access and feeding enrichment improve the behaviour of the drills and would be a valid option during summer season for the drills at Parken Zoo.