Group size and visitor numbers predict faecal glucocorticoid concentrations in zoo meerkats

Abstract

Measures of physiological stress in zoo animals can give important insights into how they are affected by aspects of their captive environment. We analysed the factors influencing variation in glucocorticoid metabolites in faeces (fGCs) from zoo meerkats as a proxy for blood cortisol concentration, high levels of which are associated with a stress response. Levels of fGCs in captive meerkats declined with increasing group size. In the wild, very small groups of meerkats are at a higher risk of predation, while in larger groups, there is increased competition for resources. Indeed, group sizes in captivity resemble those seen in unstable coalitions in the wild, which may represent a stressful condition and predispose meerkats to chronic stress, even in the absence of natural predators. Individuals in large enclosures showed lower levels of stress, but meerkat density had no effect on the stress measures. In contrast with data from wild meerkats, neither sex, age nor dominance status predicted stress levels, which may reflect less food stress owing to more equal access to resources in captivity versus wild. The median number of visitors at the enclosure was positively correlated with fGC concentrations on the following day, with variation in the visitor numbers having the opposite effect. Our results are consistent with the hypothesis that there is an optimum group size which minimizes physiological stress in meerkats, and that zoo meerkats at most risk of physiological stress are those kept in small groups and small enclosures and are exposed to consistently high numbers of visitors.

Incidence and biomarkers of pregnancy, spontaneous abortion, and neonatal loss during an environmental stressor: Implications for female reproductive suppression in the cooperatively breeding meerkat

“…Moreover, the peak fGCm values we recorded in late gestation exceeded by nearly twofold those of lategestation females during years prior to the drought [59]. Likewise, other temporary stressors, including eviction [60] and exposure to humans [109] in wild and captive meerkats, respectively, have been associated with increased fGCm concentrations, but with lower absolute values than those recorded here.…”

Effect of Tourist Activities on Fecal and Salivary Glucocorticoids and Immunoglobulin A in Female Captive Asian Elephants in Thailand

“…In examining how the tourist-to-elephant ratio affected GCs, we found an inverse relationship for feces and saliva, such that more tourists per elephant were associated with lower FGM. This was unexpected, given studies in other species that show higher visitor numbers are associated with increased GC activity in many zoo animals [ 54 , 55 , 56 ], although not always [ 57 , 58 ]. Camp size also did not affect FGM, although for saliva, elephants in larger camps did exhibit higher concentrations.…”

“…For IgA, there was considerable variability across individuals, comparable to earlier reports in elephants [ 16 , 24 ] and other species [ 61 , 62 , 63 ]. While most studies have used saliva [ 54 , 55 , 56 , 57 ], IgA can be measured in feces, including in elephants [ 16 , 24 ], which provides a noninvasive way to use this immune biomarker. Bareback-riding elephants exhibited higher fecal IgA concentrations overall, although that was primarily due to elephants at Camp C. Camp B in the saddle-riding group also had comparatively higher fecal IgA compared to the other camps.…”

Associations between glucocorticoids and sociality across a continuum of vertebrate social behavior

“…exposure to predators or extreme weather) may not promote affiliative behavior. For instance, studies of zoo-housed mammals report higher fecal/urine GCs and stress behavior coupled with a reduced rate of social behaviours with an increasing number of zoo visitors (Barbosa & Mota, 2009;Davis, Schaffner, & Smith, 2005;Mallapur, Sinha, & Waran, 2005;Scott, Heistermann, Cant, & Vitikainen, 2017). Furthermore, common marmosets (Callithrix jacchus) had higher integrated GCs and less affiliative behaviors during weekdays compared to weekends when the zoo was closed (Barbosa & Mota, 2009).…”