The effects of cage size and complexity on the behaviour of captive common marmosets, Callithrix jacchus jacchus.

Conditions of captivity of primates used in biomedical research may have deleterious effects on the welfare of the animals and consequently on the reliability of the research. We investigated the effects of cage size and cage complexity, two fundamental characteristics of captive conditions, on the behaviour of the common marmoset (Callithrix jacchus jacchus). We found an increase in the general level of activity and significant variation in the frequencies of specific behaviours with an increase in cage size and also with cage complexity. Stereotyped behaviours, which occurred in the small cages, were never exhibited in the large cages. The effect of the novelty of the changed conditions was also assessed and found to be significant for some behaviours. We also measured the time taken to capture an animal, a task frequently performed by the animal technician, under the various cage conditions. Capture time increased significantly in the larger cages, but the overall effect of the changes to the marmosets' housing conditions on the animal technician's work was not regarded as substantial. We conclude that the welfare of captive marmosets is enhanced by the provision of larger and more complex cages, and that such cages do not significantly affect the efficiency of the research laboratory.