Evidence for Chronic Stress in Captive but Not Free-Ranging Cheetahs (Acinonyx Jubatus) Based on Adrenal Morphology and Function

Abstract

The cheetah (Acinonyx jubatus) is highly endangered because of loss of habitat in the wild and failure to thrive in captivity. Cheetahs in zoos reproduce poorly and have high prevalences of unusual diseases that cause morbidity and mortality. These diseases are rarely observed in free-ranging cheetahs but have been documented in cheetahs that have been captured and held in captive settings either temporarily or permanently. Because captivity may be stressful for this species and stress is suspected as contributing to poor health and reproduction, this study aimed to measure chronic stress by comparing baseline concentrations of fecal corticoid metabolites and adrenal gland morphology between captive and free-ranging cheetahs. Additionally, concentrations of estradiol and testosterone metabolites were quantified to determine whether concentrations of gonadal steroids correlated with corticoid concentration and to assure that corticosteroids in the free-ranging samples were not altered by environmental conditions. Concentrations of fecal corticoids, estradiol, and testosterone were quantified by radioimmunoassay in 20 free-ranging and 20 captive cheetahs from samples collected between 1994 and 1999. Concentrations of baseline fecal corticoids were significantly higher (pϭ0.005) in captive cheetahs (196.08Ϯ36.20 ng/g dry feces) than free-ranging cheetahs (71.40Ϯ14.35 ng/g dry feces). Testosterone concentrations were lower in captive male cheetahs (9.09Ϯ2.84 ng/g dry feces) than in free-ranging cheetahs (34.52Ϯ12.11 ng/g dry feces), which suggests suppression by elevated corticoids in the captive males. Evidence for similar suppression of estradiol concentrations in females was not present. Adrenal corticomedullary ratios were determined on midsagittal sections of adrenal glands from 13 free-ranging and 13 captive cheetahs obtained between 1991 and 2002. The degree of vacuolation of cortical cells in the zona fasciculata was graded for each animal. Corticomedullary ratios were larger (pϭ0.05) in captive cheetahs; however, there was no difference (pϭ0.31) in the degree of corticocyte vacuolation between the two populations. These data provide both morphologic and functional evidence suggestive of chronic stress in captive cheetahs. Further research into the role of hypercortisolemia in the pathogenesis of the reproductive abnormalities and unusual diseases of captive cheetahs is needed.

Monitoring stress in captive and free-ranging African wild dogs (Lycaon pictus) using faecal glucocorticoid metabolites

“…Among the factors that are thought to cause chronic stress in captive mammals, the evidence is strong for noise (Owen et al, 2004), social instability (Peel et al, 2005), on-exhibit display (Terio et al, 2004;Wielebnowski et al, 2002) and the reproductive status of females (Fanson et al, 2011). Pregnancy is energetically costly to females (Creel and Creel, 1991) so it is not surprising that FCM concentrations were higher in pregnant and, interestingly, pseudo-pregnant females, than in acyclic females, and our observations thus agree with those reported previously in other species (Kenagy and Place, 2000;Weingrill et al, 2004).…”

“…The faecal cortisol radioimmunoassay used in this study was able to detect variation in FCM concentrations between populations and among the various social, biological and environmental The FCM values provide strong evidence that captive female wild dogs have higher levels of stress than free-ranging wild dogs, as seen in studies of other carnivores (Fanson et al, 2011;Terio et al, 2004). Among the factors that are thought to cause chronic stress in captive mammals, the evidence is strong for noise (Owen et al, 2004), social instability (Peel et al, 2005), on-exhibit display (Terio et al, 2004;Wielebnowski et al, 2002) and the reproductive status of females (Fanson et al, 2011).…”

“…), GC concentrations were higher in captive than in free-ranging individuals (Fanson et al, 2011;Marra et al, 1995;Rangel-Negrin et al, 2009;Terio et al, 2004). If the level of stress is indeed higher in captive animals than in free-ranging animals, then it might help explain poor reproductive success in captivity in some species (Carlstead and Shepherdson, 1994).…”

How should the psychological well‐being of zoo elephants be objectively investigated?

“…In cases of chronic stress, HPA outputs and responsiveness can be chronically elevated; this can even result in the hypertrophy of the adrenal gland cortex [e.g., Terio et al, 2004]. The HPA system can also respond with changes in circadian patterning (the loss of the normal night-time trough occurs in some humans with depression), or even with decreased adrenal activity largely due to upregulation of negative feedback loops within the axis and/or habituation of the adrenal to ACTH [see also Brown et al, 2008].…”

What do population‐level welfare indices suggest about the well‐being of zoo elephants?

“…Our focus has been elephants, but this approach has been applied to other taxa too [e.g. carnivores: Terio et al, 2000Terio et al, , 2004Munson et al, 2005;. Obviously, valid comparisons must compare like with like (e.g.…”