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Fecal glucocorticoid metabolite response of captive koalas (Phascolarctos cinereus) to visitor encounters

Webster, K, Narayan, E & de Vos, N 2017, General and Comparative Endocrinology, vol. 244, pp. 157-163.

This study investigated the effect of visitor encounter experiences involving photography on the cortisol secretion response of captive koalas, which is an indicator of physiological stress. Overall, male koalas had higher mean faecal cortisol metabolite (FCM) concentrations compared to females. In male koalas the highest FCM concentrations were observed during an intensive photography treatment (as opposed to standard photography and control), whereas there was no apparent physiological response to photography regime observed in female koalas.

  Koalas were housed in an enclosure at Taronga Zoo, Sydney with multiple bays, with two or three koalas housed per bay. Animals in each bay were sequentially subject to three different intensities of visitor photography (none, standard or intensive) while FCM concentrations of koalas were monitored. In all bays where male and female koalas were housed together, males’ FCM concentrations were higher than females’ throughout the experiment. Male koalas’ mean FCM concentrations peaked during the intensive photography regime, while captive female koalas’ mean FCM concentrations were higher during the standard regime than the intensive treatment. There was substantial variation between FCM traces between individuals, particularly among female koalas.

  Sexual differences in FCM concentrations have been previously reported in captive koalas. In this study, factors such as reproductive status and social dominance relationships might have contributed to the differentiated individual FCM secretion response of female koalas, but these factors were not controlled or tested. Although less prominent, differences between male FCM concentrations may relate to factors that affect “testosterone-cortisol interplay”, such as hierarchical relationships or the presence/absence of females in the enclosure. For all male koalas used in this study, FCM concentrations decreased during the return to the standard treatment, which suggested that (1) changes in the photography regime might result in only short-term rather than chronic stress in these captive koalas and (2) these captive koalas were able to physiologically respond to environmental cues to maintain homeostasis.

  The findings of this study demonstrate the effectiveness of a non-invasive endocrinology tool for the assessment of physiological stress in captive koalas. The authors recommend that future studies examine differences between individual FCM profiles and complement FCM quantification with monitoring of behaviour and reproductive status to incorporate a wider range of variables that may contribute to stress levels in captive animals.

 

Summarised by Zilong Du

 

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