Fecal glucocorticoid metabolites as biomarkers in equids : assay choice matters

Hinchcliffe, DL; Lea, JMD; Palme, R; Shultz, S

Abstract

Free ranging animals are exposed to environmental, demographic, and ecological challenges over time, which can affect their health and fitness. Non‐invasive biomarkers can provide insight into how animals cope with these challenges and assess the effectiveness of conservation management strategies. We evaluated how free ranging ponies (Equus ferus caballus) on the Carneddau Mountain range, North Wales respond to 2 stimuli: an acute stressor of an annual roundup event in November 2014, and spatial and temporal variation in ecological factors in 2018. We evaluated fecal glucocorticoid metabolites using 2 enzyme immunoassays (EIAs): an 11‐oxoetiocholanolone EIA (measuring 11,17‐dioxoandrostanes [11,17‐DOAs]) and a corticosterone EIA. The former assay has been validated in equids, whereas there is limited evidence for the suitability of the latter. We used an additional parent testosterone EIA to measure fecal androgen metabolites in response to the ecological challenges. Following the roundup, the metabolite concentrations measured by the 2 glucocorticoid EIAs were not correlated. The 11,17‐DOAs were elevated from the second day following the roundup and then slowly returned to pre‐round levels over the next 2 weeks. In contrast, the metabolites measured by the corticosterone assay showed no response to the roundup. For the ecological data, all 3 assays detected a positive correlation between metabolites and social group size in males but not in females. The metabolite concentrations measured by the testosterone and corticosterone assays were highly correlated and were temporally associated with the onset of the breeding season, whereas the 11,17‐DOAs were not. The co‐variance of metabolites measured by the corticosterone and testosterone assays, and the lack of an acute response in the corticosterone assay to the roundup, suggests that metabolites detected by the corticosterone assay were not primarily associated with increased glucocorticoid production. We recommend using well‐validated fecal biomarker assays of hypothalamus‐pituitary‐adrenal axis activity to evaluate and compare the effect of different management interventions and environmental change. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.

Citation

Hinchcliffe, D., Lea, J., Palme, R., & Shultz, S. (2021). Fecal glucocorticoid metabolites as biomarkers in equids : assay choice matters. Journal of Wildlife Management, 85(6), 1175-1186. https://doi.org/10.1002/jwmg.22066

• Journal Article Type: Article
• Acceptance Date: Apr 9, 2021
• Online Publication Date: Jun 1, 2021
• Publication Date: Jul 23, 2021
• Deposit Date: Jun 4, 2021
• Publicly Available Date: Jun 4, 2021
• Journal: The Journal of Wildlife Management
• Print ISSN: 0022-541X
• Electronic ISSN: 1937-2817
• Publisher: Wiley
• Volume: 85
• Issue: 6
• Pages: 1175-1186
• DOI: https://doi.org/10.1002/jwmg.22066
• Publisher URL: https://doi.org/10.1002/jwmg.22066
• Related Public URLs: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1937-2817
• Additional Information: Additional Information : ** Article version: VoR ** From Wiley via Jisc Publications Router ** Licence for VoR version of this article: http://creativecommons.org/licenses/by/4.0/ **Journal IDs: issn 0022-541X; issn 1937-2817 **Article IDs: publisher-id: jwmg22066 **History: published 01-06-2021; accepted 09-04-2021; rev-recd 29-03-2021; submitted 06-05-2020; Funders : Royal Society;Chester Zoo; Projects : UF110641;Conservation Fellowship; Grant Number: UF110641; Grant Number: Conservation Fellowship