Spikes in the data: biological validation and applications of an assay for detecting faecal glucocorticoid metabolites in Western European hedgehogs (Erinaceus europaeus)

Assessment of wildlife health and welfare is an increasingly important tool in identifying environmental stressors affecting species of conservation concern. An improved understanding of physiological responses to stress can inform management practises and provide methods for detecting factors that may influence individual and population viability. Faecal glucocorticoid metabolites (FGMs) are a popular non-invasive proxy for stress. To measure FGMs, the chosen assay must be sensitive to changes, and biological validation is required to demonstrate that these changes are relevant responses to stress. This study carried out a preliminary validation of three enzyme immunoassays (EIAs) previously used on mammals, and biologically validated the most sensitive assay for use in Western European hedgehogs (Erinaceus europaeus), which are classified as Near Threatened (International Union for Conservation of Nature) and are a species of European conservation concern. All three assays were sensitive to FGM changes, with the 11 beta-hydroxyetiocholanolone EIA (hereafter, 'assay 69a') showing the greatest increase above baseline, and therefore being the most sensitive. A biological validation using assay 69a compared FGMs from hedgehogs exposed to stressors after admission to rehabilitation (Day 1) with FGMs collected 7 days later (Day 7) following veterinary care. Individual FGMs were highest on Day 1 (x- = 743 ng/g, standard deviation [SD] = 602.7) and reduced by Day 7 (x- = 224 ng/g, SD = 207.5). Hedgehogs with FGMs below 1000 ng/g had an 82% chance of surviving rehabilitation; at 3000 ng/g, they had a 52% chance of survival, while survival rates for those with FGMs over 10 000 ng/g were less than 1%. Finally, a comparison of wild hedgehogs with and without the parasite Capillaria showed higher FGMs in infected individuals, demonstrating the utility of assay 69a for measuring different stressors in Western European hedgehogs. We recommend that assay 69a be used in future hedgehog conservation and welfare studies, to better understand the environmental, and anthropogenic stressors that may contribute to their ongoing decline. Faecal glucocorticoid metabolites (FGMs) are used to measure stress in wildlife non-invasively. We assessed three enzyme immunoassays (EIAs) and biologically validated the 11 beta-hydroxyetiocholanolone (69a) EIA for Western European hedgehogs. The assay detected variations in FGMs associated with parasites, and survival during rehabilitation. We recommend the 69a EIA for use in future hedgehog conservation and welfare studies.

Aberystwyth University
Nottingham Trent University