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

Abstract

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