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One size does not fit all: Monitoring faecal glucocorticoid metabolites in marsupials

Kerry V. Fanson a,b,⇑, Emily C. Best c, Ashley Bunce c,d, Benjamin G. Fanson b, Lindsay A. Hogan e,f, Tamara Keeley e, Edward J. Narayan g, Rupert Palme h, Marissa L. Parrott i, Trudy M. Sharp j, Kim Skogvold k,l, Lisa Tuthill m, Koa N. Webster n, Meredith Bashaw a,o

a Wildlife Reproductive Centre, Taronga Conservation Society Australia, Dubbo, NSW, Australia

b Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong, VIC, Australia

c School of Biological Sciences, The University of Queensland, Brisbane, QLD, Australia

d Department of Environment and Heritage Protection, Brisbane, QLD, Australia

e Wildlife Biology Unit, School of Agriculture and Food Sciences, The University of Queensland, Gatton, QLD, Australia

f Native Species Breeding Program (NSBP), Perth Zoo, South Perth, WA, Australia

g Graham Centre for Agricultural Innovation & School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, NSW, Australia

h Department of Biomedical Sciences, University of Veterinary Medicine, Vienna, Austria

i Wildlife Conservation and Science, Zoos Victoria, Parkville, VIC, Australia

j Fowlers Gap Arid Zone Research Station, Centre of Ecosystem Science, School of Biological Earth and Environmental Sciences, University of New South Wales, Kensington, NSW, Australia

k Conservation Medicine Program, School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, Australia

l Perth Zoo Veterinary Department, Perth Zoo, South Perth, WA, Australia

m Moonlit Sanctuary, Pearcedale, VIC, Australia

n Department of Biological Sciences, Macquarie University, Sydney, NSW, Australia

o Department of Psychology, Franklin and Marshall College, Lancaster, PA, USA

ABSTRACT

Marsupial research, conservation, and management can benefit greatly from knowledge about glucocorticoid (GC) secretion patterns because GCs influence numerous aspects of physiology and play a crucial role in regulating an animal’s response to stressors. Faecal glucocorticoid metabolites (FGM) offer a non-invasive tool for tracking changes in GCs over time. To date, there are relatively few validated assays for marsupials compared with other taxa, and those that have been published generally test only one assay. However, different assays can yield very different signals of adrenal activity. The goal of this study was to compare the performance of five different enzyme immunoassays (EIAs) for monitoring adrenocortical activity via FGM in 13 marsupial species. We monitored FGM response to two types of events: biological stressors (e.g., transport, novel environment) and pharmacological stimulation (ACTH injection). For each individual animal and assay, FGM peaks were identified using the iterative baseline approach. Performance of the EIAs for each species was evaluated by determining (1) the percent of individuals with a detectable peak 0.125–4.5 days post-event, and (2) the biological sensitivity of the assay as measured by strength of the post-event response relative to baseline variability (Z-score). Assays were defined as successful if they detected a peak in at least 50% of the individuals and the mean species response had a ZP 2. By this criterion, at least one assay was successful in 10 of the 13 species, but the best performing assay varied among species, even those species that were closely related. Furthermore, the ability to confidently assess assay performance was influenced by the experimental protocols used. We discuss the implications of our findings for biological validation studies.