Faecal Glucocorticoid Metabolites and H/L Ratio Are Related Markers of Stress in Semi-Captive Asian Timber Elephants

Abstract

Animals are kept in captivity for various reasons, but species with a slower pace of life may adapt to captive environments less easily, leading to welfare concerns and the need to assess stress reliably in order to develop effective interventions. Our aim was to assess welfare of semi-captive timber elephants from Myanmar by investigating the relationship between two physiological markers of stress commonly used as proxies for welfare, faecal glucocorticoid metabolite concentrations (FGM) and heterophil/lymphocyte ratios (H/L), and link these measures to changes in body condition (determined by body weight). We further assessed how robustly these two markers of stress performed in animals of different age or sex, or in different ecological contexts. We measured FGM concentrations and H/L ratios between 2016 and 2018 from 316 samples of 75 females and 49 males ranging in age from 4 to 68. We found a positive and consistent link between FGMs and H/L ratios in Asian elephants, irrespective of their sex, age, or ecological context. Our results will help to inform managers of (semi-) captive elephants about using heterophil/lymphocyte ratio data from blood smears on site as a potentially cheaper and faster alternative to determining stress than measuring faecal glucocorticoid metabolite concentrations in the laboratory.

Measures of Oxidative Status Markers in Relation to Age, Sex, and Season in Sick and Healthy Captive Asian Elephants in Thailand

“…For fGCMs, relationships with age are not always clear. In this study, there was no age effect, which was comparable to a study of semicaptive elephants in Myanmar [97]. However, a study of tourist camp elephants in Thailand found older animals exhibited overall lower fGCM concentrations [98].…”

“…However, a study of tourist camp elephants in Thailand found older animals exhibited overall lower fGCM concentrations [98]. One reason might be how age groups were defined, being across four broad age categories in this study and that of Seltmann et al [97] compared to using age as a continuous variable in Bansiddhi et al [98]. In terms of sex effects, those results have also not always been consistent, even in the same population.…”

Positive reinforcement conditioning as Sumatran tiger's (Panthera tigris sumatrae) social enrichment at Tambling Wildlife Nature Conservation Rescue Centre, Lampung, Indonesia

“…Behavioral observation and physiological indicators were elaborated in this research. In line with other researches (Davis et al 2008;Seltmann et al 2020), this present research showed that the N/L ratio could be used as a physiological stress indicator in the field or remote area. Behavior observation was merely enough to measure stress response (Hofer and East 1998).…”

“…Each neutrophil and lymphocyte were counted within 200 white blood cells under the microscope (Kerr 2002;Theml et al 2004;Shiravastav et al 2012). Then the counted neutrophils were manually divided by counted leucocytes to obtain the N/L ratio (Dhabhar et al 1996;Stockman et al 2011;Seltmann et al 2020).…”

“…Neutrophil/lymphocyte ratio (N/L ratio) can be applied to measure an animal's stress. Examination of the N/L ratio is a more practical and rapid method than hormonal assays to be performed in the field (Seltmann et al 2020).…”