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.
Mammalian mating systems are thought to be shaped by the spatial distribution and abundance of key resources, which in turn influence the spacing behaviour of individuals. In particular, female home range size is predicted to reflect the availability of key resources. We documented the availability and distribution of food and shelter resources for two neighbouring populations of bobucks, or mountain brushtail possums, Trichosurus cunninghami, that were characterised by different mating systems: our "forest population" was socially monogamous, whereas the "roadside population" was polygynous. Both silver wattle, Acacia dealbata, the main food resource for bobucks, and den-trees, which provided shelter, occurred at significantly higher density at the roadside site. The pattern of distribution of these two resources also differed between the sites. Both food and den-trees were scattered evenly throughout the roadside habitat. In contrast, den-trees were located predominantly at one end of the forest site, while silver wattle trees were located at the other. There was no significant difference in the amount of silver wattle, or in the number of den-trees, located within the home ranges of individual females at the two sites. However, forest females had home ranges, on average, almost three times the size of those of roadside females. At the roadside site, the size of female home ranges varied inversely with the density of silver wattle, indicating that these females ranged over as large an area as necessary to gain access to sufficient silver wattle trees. There was no such relationship among forest females. These populations provide a clear example of resource distribution determining female home range size. This influenced the number of female home ranges a male's home range overlapped with, which in turn determined the mating system. Such clear links between resource availability and mating system have not previously been established in a marsupial.
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