Ethological studies of well-being in two species of macaques after transition from single cages to housing in social groups (1997)

Ljungberg, T., Westlund, K., Ryden, L.

Abstract

Two species of macaques (M. mulatta and M. fascicularis) have been used for several decades in biomedical research at the University of Uppsala, Sweden. The monkeys were previously housed in single cages and enrichment routines were not ordinarily used. Infants of M. mulatta were weaned early, kept separated from the mother and often hand-fed by the keepers. These monkeys thus became, at least partially, imprinted on man and this routine was deliberately used for facilitating handling. During recent years, the housing of the macaques has been changed and larger cages and group-housing has been introduced. Interestingly, different strategies have been used for the M. mulatta and fascicularis. For the fascicularis, cages with a floor area of 2.8-3.6 m2 and with a height of 2.25 m were used. In these cages, 2-4 animals, tested for compatibility, formed a group. Enrichment material was provided. For the mulatta, larger cages were constructed and each of six cages consisted of a 100 m2 outdoor area and 30 m2 indoor area. No enrichment material except a row of wooden shelves on the walls of the indoor area was provided. The groups at the time of study consisted of between 3-8 animals, with a single male present in each group. Ethological studies of social interactions, affiliative and aggressive behaviours and time-budgets were performed for both species using previously developed ethograms and focal sample technique. Each animal was the focal individual for 80-100 minutes. The social interactions between the M. fascicularis in their small groups were characterized by low levels of aggression and social grooming at normal levels including all individuals. Time-budget studies showed effect of enrichment in that foraging times were high and abnormal behaviours were almost absent. The results for the M. mulatta were radically different. Over all, the animals were very inactive. The groups were not well functioning, with certain individuals in each group being the main victims of the observed aggression and being without social grooming relationships. High levels of auto-grooming was often seen in these animals. Stereotypes or other forms of abnormal behaviours were seen in almost all animals. We also studied the occurence of reconciliatory behaviour, a behaviour previously described in great detail in the rhesus monkey. In 4 of the 5 rooms studied, reconciliatory behaviours were absent. Our results show that the change from keeping macaques in single cages to keeping them in groups has to be done with awareness of the advantages and problems associated with different forms of group-housing. It is not recommended to on a trial-and-error basis try to create new, large social groups with e.g. adult rhesus macaques, especially when the animals have a history of early weaning, social separation and imprinting on man. It is not enough to just give macaques more space, this has to be combined with adequate knowledge of primate social behaviour and an enrichment program.