Environmental, social, management and health factors associated with within- and between-individual variability in fecal glucocorticoid metabolite concentrations in zoo-housed Asian and African elephants
Identifying links between environmental, social, management, and health factors as they relate to physiological stress in captive elephants is crucial for the improvement of welfare and husbandry practices in North American zoos. Studies have examined the effects of short-term and chronic elevations in glucocorticoids in small groups of elephants, but few have examined adrenal activity on a large scale. This study evaluated 106 Asian (Elephas maximus) and 131 African (Loxodonta africana) elephants housed at 64 accredited facilities across North America. Fecal samples were collected every other week for 12 months and analyzed for glucocorticoid metabolite (FGM) concentrations. Risk factors for mean and individual variability (CV) in FGM were subjected to univariate and multivariable analyses using epidemiological methods. Independent variables that included individual traits, social environment, housing and management factors were chosen based on their identification as risk factors in previously published models for the same North American population of elephants. Results indicate that African elephants are more responsive to social stressors than Asians, and that poor joint health is a stress-related welfare problem for Asian, but not African elephants. For both species, higher FGM concentrations were associated with zoos located at more northern latitudes and having free access to indoor/outdoor spaces, whereas spending more time in managed interactions with staff were associated with lower FGM concentrations. Also important for captive management, elephants having diverse enrichment options and belonging to compatible social groups exhibited lower mean and reduced intra-individual variability in FGM. Our findings show that aspects of the zoo environment can be potential sources of stress for captive elephants, and that there are management activities that can facilitate coping and adapting to zoo conditions. Given species differences in factors that affected FGM, targeted, species-specific management approaches likely are needed to ensure good welfare for all elephants.