Faecal glucocorticoid metabolites as a measure of adrenocortical activity in polar bears (Ursus maritimus)

Anna Hein; Rupert Palme; Katrin Baumgartner; Lorenzo von Fersen; Benno Woelfing; Alex D Greenwood; Thea Bechshoft; Ursula Siebert

doi:10.1093/conphys/coaa012

Faecal glucocorticoid metabolites as a measure of adrenocortical activity in polar bears (Ursus maritimus)

Conserv Physiol. 2020 Apr 4;8(1):coaa012. doi: 10.1093/conphys/coaa012. eCollection 2020.

Authors

Anna Hein¹, Rupert Palme², Katrin Baumgartner³, Lorenzo von Fersen³, Benno Woelfing¹, Alex D Greenwood^{4

5}, Thea Bechshoft⁶, Ursula Siebert¹

Affiliations

¹ Institute for Terrestrial and Aquatic Wildlife Research (ITAW), University of Veterinary Medicine Hannover, Bischofsholer Damm 15, 30173 Hannover, Germany.
² Unit of Physiology, Pathophysiology, and Experimental Endocrinology, De for Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210 Vienna, Austria.
³ Nuremberg Zoo, Am Tiergarten 30, 90480 Nuremberg, Germany.
⁴ Department of Wildlife Diseases, Leibniz-Institute for Zoo and Wildlife Research, Alfred-Kowalke-Strasse 17, 10315 Berlin, Germany.
⁵ Department of Veterinary Medicine, Freie Universität Berlin, Oertzenweg 19b, 14163 Berlin, Germany.
⁶ Department of Bioscience, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark.

Abstract

Analysis of faecal glucocorticoid metabolites (FGMs) is frequently applied to assess adrenocortical activity in animal conservation and welfare studies. Faecal sample collection is non-invasive and feasible under field conditions. FGM levels are also less prone to circadian rhythms, episodic fluctuations and short acute stressors than glucocorticoid (GC) levels obtained from other matrices, for example blood or saliva. To investigate the suitability of FGM measurement in polar bears (Ursus maritimus), a species listed as Vulnerable by the IUCN (International Union for Conservation of Nature), a cortisol enzyme immunoassay (EIA) was biologically validated by demonstrating a significant increase in FGMs after five zoo-to-zoo transports. In addition to validating the method, the study also documented an average delay of 7 h until the first occurrence of food colorants in the monitored polar bears, which provides essential information for future studies. After validation, the assay was applied to measure FGM concentrations of five polar bears over a 1-year period. Several pre-defined potentially stressful events were recorded in an event log to measure their effect on FGM concentrations. A mixed model analysis revealed significant increases in FGM concentrations after social tension and environmental changes, whereas season and sex had no significant effect. The study demonstrates that the applied cortisol EIA is suitable for measuring FGM levels in polar bears and that using a carefully validated assay for FGM analysis in combination with a detailed sampling protocol can serve as a valuable tool for evaluating mid- to long-term stress in polar bears. FGM levels can be used to monitor stress in captive polar bears in order to optimize housing conditions but also to elucidate stress responses in wild populations for targeted conservation measures.

Keywords: EIA; Ursus maritimus; biological validation; faecal glucocorticoid metabolites; non-invasive HPA axis assessment; stress.