A note on indoor and outdoor housing preferences of common marmosets ('Callithrix jacchus')

This study examined the preferences of six pairs of common marmosets ('Callithrix jacchus') from the colony at the University of New England, Australia, between their home cage and either a large, enriched, indoor room or a smaller outdoor cage. When given free access to move between their home cage and outdoors, the marmosets spent 70% of their day in the outdoor cage from the third day of testing until the end of the first 9 days of the first trial and also at 6 and 13 weeks later. Hence they showed a clear preference for the outdoor cage over the home cage. By contrast, when provided with a choice between the home cage and the indoor room, time spent in the indoor room decreased from 56% to 38% during the first 3 days of the trial and continued to decrease to less than 25% over the next week. The indoor room was visited more often than the outdoor cage (P = 0.001), but the visits were of shorter duration (P = 0.005), and were more often made by just one of the pair (P = 0.001). The results demonstrate that the marmosets had a strong preference to go outdoors during the day and did so without habituation, whereas a larger enriched indoor room apparently decreased in attractiveness to them.