Sleep monitoring of an Asian elephant Elephas maximus calf at Night Safari, Singapore: testing whether sleep time is a significant predictor of cortisol or the onset of positive elephant endotheliotropic herpesvirus viraemia

Abstract

A number of methods for measuring the welfare of elephants in human care have been used within zoological associations and rescue centres worldwide. The measurement of glucocorticoids in relation to stress has been particularly well validated. Measuring stress is especially important for Asian elephant Elephas maximus calves between one and 8 years of age which are highly susceptible to developing elephant endotheliotropic herpesvirus (EEHV) haemorrhagic disease. Sleep monitoring has been used as a possible means of assessing the welfare state of animals, although the efficacy of this method has not been validated. Our aim was to test whether sleep time or cortisol provided the most significant predictor for the onset of positive EEHV blood viraemia in a 2 year‐old calf at Night Safari, Singapore. Faecal samples were collected twice per week and assayed for glucocorticoids. Using closed‐circuit television, the time the calf slept each night was measured between December 2017 and September 2018. Sleep was not a predictor of viraemia nor of cortisol concentration in this study. However, cortisol appeared to be related to the occurrence of viraemia.