Social and environmental influences on the welfare of zoo-housed spider monkeys (Ateles geoffroyi rufiventris)
A series of studies was undertaken to assess zoo-housed spider monkey (SM) welfare. Validation of an enzyme immunoassay for urinary cortisol (UC) enabled non-invasive measurement of the impact of various conditions on physiological stress responses in SMs at Chester Zoo over a 7-year period.
The first study was to compare UC levels with visitor numbers (being the first investigation of physiological impact of visitors on zoo animals using UC). Results showed an association between higher visitor numbers and elevated UC, supporting behavioural evidence that visitors can have an adverse impact on zoo primates.
Secondly, aggression in SMs in 55 zoos worldwide was investigated by questionnaire. Results indicated relatively frequent severe and lethal aggression among SMs (adult males: most frequent aggressors; sub-adult males: most frequent targets). This could be a consequence of captivity: males are normally transferred between zoos, whereas wild females emigrate at maturity. Thirdly, a variety of social stressors were investigated over a 7-year period at Chester Zoo, using UC. Aggression had the largest effect, with significant results also obtained for reproductive and separation events.
Lastly, replacement of Chester Zoo’s breeding male was studied; in adult females, a significant behavioural effect was found, but little evidence of elevated UC. Overall, the research indicates that the SM group demonstrated a varying stress response to the studied stressors, but without evidence of long-term chronic stressors normally associated with poor welfare.
A number of recommendations have now been made regarding enclosure design, relocation of individuals and gradual introduction of SMs in zoos.