For captive primates, environmental enrichment may improve psychological well-being, as indicated by changes in the frequency of species-typical and abnormal behaviours. The effects of enrichment on physical well-being have also been examined, but little attention has been devoted to the relationship between enrichment and animal health. We therefore studied the health records of 98 rhesus macaques (Macaca mulatta) to measure the effects that enrichment and social housing manipulations had on the number of veterinary treatments and days of therapy required by the monkeys. Subjects were housed singly, in pairs and in groups. Half of the subjects in each housing condition were enriched and the others were controls. Control and enriched subjects did not differ in the number of treatments they required, but enriched subjects received longer therapies than did controls. Neither treatments nor days of therapy were frequent or randomly distributed across housing conditions; pair-housed subjects required the least treatment and therapy, whereas singly-housed subjects were treated slightly more frequently for diarrhoea-related problems, and group-housed subjects for trauma-related problems. Subject age, however, was a potential confounding factor. Because subjects were part of a specific pathogen-free breeding programme, they spent only certain ages in each housing condition. Results suggest that inanimate enrichment neither diminishes nor improves the health of young macaques, but that enriched monkeys may require longer periods of therapy than do controls. Pair housing may be an effective housing strategy from both veterinary and behavioural points of view, necessitating relatively few treatments, but providing some social enrichment opportunities.

A technique measuring leukocyte (neutrophil) activity was used to examine differences between stress levels in a breeding colony of rhesus macaques housed in either a traditional caging system or open-rooms. The leukocyte activation test measured the degree to which blood from the two treatment groups could launch a further neutrophil response (superoxide production) to an in vitro challenge. Animals housed in a traditional caging system produced a significantly lower leukocyte response than animals housed in open-rooms, indicating that there was a higher level of stress associated with caged housing than open-room housing. This was not influenced by whether animals were physically restrained or trained to stand for a sedating injection. No differences were found between treatment groups in leukocyte numbers or composition. This study validates the use of the leukocyte activation test to assess physiological stress levels in non-human primates and demonstrates the animal welfare benefits of open-room housing over traditional laboratory caging systems.

This study demonstrates that only a minimal time investment was needed to train a large troop of laboratory non-human primates to co-operate in the catching procedure. A group of 45 rhesus macaques (Macaca mulatta) was trained to enter a chute system voluntarily and be caught one by one. The total duration of the training sessions was under six hours, with less than 15 total work-hours invested by three people. The result was an improved capture procedure which minimized risk to personnel and distress to the animals.

In order to assess the environmental enrichment value of a small swimming pool for captive juvenile rhesus macaques (Macaca mulatta), observations of social and individual behaviours were made during baseline and experimental (pool) conditions. When the pool was available there was less social grooming and cage manipulation, and more play. Most of the monkeys engaged in diving and underwater swimming. The presence of pieces of banana at the bottom of the pool reduced these water-related activities, whereas when raisins were spread along the bottom or when there was no food in the water, there was more diving and less aggression. Certain effects tended to vary with dominance status, but individual differences appeared more important than social status in determining reactions to the water. The provision of a small swimming pool for captive macaques is an effective contribution to improving their welfare.

An attempt was made to encourage more foraging behaviour in eight pair-housed adult rhesus macaques (Macaca mulatta). No special device and no special food were used Daily commercial dry food rations (238g per animal) consisting of 33 bar-shaped or 16 star-shaped biscuits per animal were placed on the mesh ceiling of the cages instead of in the feed-boxes. This induced an 80-fold increase (17.0 vs 1362.9s) and 289-fold increase (12.3 vs 3551.4s), respectively, in foraging time. The animals spent on average 9.6 per cent and 24.7 per cent respectively, of four-hour observation sessions foraging for biscuits from the mesh ceiling. Working for their food did not discourage them from eating all left-overs in the course of a day regardless of the shape of the biscuits.

It was concluded that the new feeding procedure enhanced the animals’ behavioural well-being by encouraging foraging activities thereby helping to counteract understimulation.

Large animal species are prone to local extirpation, but ecologists cannot yet predict how the loss of megaherbivores affects ecosystem processes such as seed dispersal. Few studies have compared the quantity and quality of seed dispersal by megaherbivores versus alternative frugivores in the wild, particularly for plant species with fruit easily consumed by many frugivorous species. In a disturbed tropical moist forest in India, we examine whether megaherbivores are a major frugivore of two tree species with easily edible, mammal-dispersed fruit. We quantify the relative fruit removal rates of Artocarpus chaplasha and Careya arborea, by the Asian elephant (Elephas maximus) and alternative dispersers. Through focal watches and camera trapping, we found the elephant to be amongst the top three frugivores for each tree species. Furthermore, seed transects under A. chaplasha show that arboreal frugivores discard seeds only a short distance from the parental tree, underscoring the elephant's role as a long-distance disperser. Our data provide unprecedented support for an old notion: megaherbivores may be key dispersers for a broad set of mammal-dispersed fruiting species, and not just fruit inaccessible to smaller frugivores. As such, the elephant may be particularly important for the functional ecology of the disturbed forests it still inhabits across tropical Asia.