Characterisation of the sympathetic nervous system of Asian ( Elephas maximus) and African ( Loxodonta africana) elephants based on urinary catecholamine analyses

Abstract

Assessing the welfare status of captive animals using non-invasive measurements of hormones is of growing interest because this can serve as an effective tool to facilitate the optimization of environmental and husbandry conditions. Both the African elephant ( Loxodonta africana) and the Asian elephant ( Elephas maximus) exhibit extremely low breeding success in captivity, and because elevated levels of stress may negatively influence reproductive functions, this study sought to establish a method for assessing sympathoadrenal activity in captive female elephants. We found a circadian variation in urinary noradrenaline (norepinephrine, NE), adrenaline (epinephrine, Epi) and dopamine (DA) under short day length. Peak activity of noradrenaline and dopamine was noted at 3 a.m. Adrenaline showed a biphasic pattern with a minor peak recorded at 3 a.m. and a major peak 9 a.m. Under long-day photoperiodic conditions, simultaneous peaks of noradrenaline and adrenaline were again noted at 3 a.m. whereas dopamine does not appear to have a distinct circadian pattern under long-day length. A transfer of two elephant cows resulted in a marked increase in urinary adrenaline and noradrenaline levels, confirming that the transfer represented a stressful event. During the peripartal period, noradrenaline concentrations increased and maximum concentrations were obtained at delivery. Daily measurements of urinary dopamine throughout the follicular phase revealed an increase in dopamine secretion close to ovulation. This increase might indicate a role of dopamine in the ovulatory mechanisms. These results suggest that changes in urinary catecholamine excretion reflect fluctuations in sympathoadrenal activity and may be a useful indicator of stress.