Faecal cortisol metabolites in Bengal (Panthera tigris tigris) and Sumatran tigers (Panthera tigris sumatrae)

Abstract

The tiger (Panthera tigris) faces a great risk of extinction as its wild numbers have plummeted due to poaching and habitat destruction so ex-situ conservation programs are becoming ever more necessary. Reliable non-invasive biomarkers of the stress hormone (cortisol) are necessary for assessing the health and welfare of tigers in captivity. To our knowledge, non-invasive stress endocrinology methods have not been tested as widely in tigers. The first aim of this study was to describe and validate a faecal cortisol metabolite enzyme-immmunoassay (FCM EIA) for two tiger sub-species, the Bengal tiger (Panthera tigris tigris) and the Sumatran tiger (Panthera tigris sumatrae). Individual tigers (n=22) were studied in two large Zoos in Queensland, Australia (Dreamworld Theme Park and Australia Zoo). Fresh faecal samples (<12 h old) were collected each morning from both Zoos over a study period of 21 days. Biological validation was conducted separately by collecting feces 5 days before and 5 days after blood was taken from four male and five female tigers. Results showed that mean FCM levels increased by 138% and 285% in the male and female tigers within 1 day after bloods were taken, returning to baseline in 5 days. Laboratory validations of the FCM EIA were done using an extraction efficiency test and parallelism. Results showed >89% recovery of the cortisol standard that was added to tiger faecal extract. We also obtained parallel displacement of the serially diluted cortisol standard against serially diluted tiger faecal extract. Our second aim was to determine whether the FCM levels were significantly different between tiger sub-species and sex. Results showed no significant difference in mean FCM levels between the Bengal and Sumatran tiger sub-species. Mean levels of FCMs were significantly higher in females than in male tigers. Those male and female tigers with reported health issues during the study period expressed higher FCM levels than the reportedly healthy tigers. Interestingly, those tigers that took part in some activity (such as walks, photos, presentations and guest feeds) expressed moderately higher FCM levels at Dreamworld and lower FCM levels at Australia Zoo in comparison to those tigers that did not take part in such activities. These results indicate potential habituation in some tigers for routine activity through specialized training and pre-conditioning. In conclusion, the FCM EIA described in this study provides a reliable non-invasive method for evaluating the stress status of tigers in Zoos.

Conservation Physiology of Tigers in Zoos: Integrating Stress Physiology and Behaviour to Monitor Their Health and Welfare

“…This study demonstrated that tiger stress levels were significantly different between sexes and zoos, matching with previous studies that also found higher average stress levels in females than males for other felids [18]. Narayan et al's [8] study also showed that individual tigers responded differently to the stressor type, intensity and duration. This highlights the phenomenon of unique personalities or coping abilities in animals [19].…”

“…Glucocorticoids or stress hormones (e.g. corticosterone and cortisol in tigers) are released into systemic blood circulation during the initiation of the physiological stress response [8]. This occurs when a stimulus (e.g.…”

“…Stereotypic or repetitive behaviour in animals serves as indicators or stress, usually associated with elevated glucocorticoid levels [10]. Some of the stressors commonly faced in the captive environment include elements of the enclosure [11], certain aspects of animal care routines [8] and construction noise [12]. Assessment of the welfare of tigers in captivity will be more comprehensive through the integration of behavioural and physiological measures [13].…”

“…Furthermore, the stereotypic extent was reduced with environmental enrichment (e.g. increased enclosure size, presence of pools and stones, social interactions with conspecifics Furthermore, Narayan et al [8] used faecal cortisol monitoring to investigate the stress physiology of two tiger sub-species, the Bengal and Sumatran tigers, held in two Australian zoos. This study demonstrated that tiger stress levels were significantly different between sexes and zoos, matching with previous studies that also found higher average stress levels in females than males for other felids [18].…”

Non-invasive measurement of adrenocortical activity in a myrmecophageous mammal, the bat-eared fox

“…In our 8 study, as well as these other investigations, inter-individual and intersexual variation in fGCM levels appears high. However, it is highly likely that the marked intersexual difference suggested by the post-ACTH data was linked to the injury that the female had sustained during the capture procedure (see also Muenscher et al 2010;Narayan et al 2013). We found no clear, unidirectional intersexual differences in circulating cortisol levels or fGCM, and therefore predict that larger studies will find healthy male foxes exhibiting cortisol levels comparable to non-lactating female bat-eared foxes.…”