Physiological validation of the use of faecal glucocorticoid metabolites as a measure of stress in a passerine and a columbid from southern Africa

ABSTRACT

Faecal glucocorticoid metabolite (fGCM) analysis provides a non-invasive, feedback-free approach for monitoring adrenocortical responses to natural and anthropogenic stressors. The use of enzyme-immunoassays (EIAs) to quantify immunoreactive fGCMs has gained popularity in recent years but requires species-specific validation prior to first use. We conducted a pharmacological challenge with adrenocorticotropic hormone (ACTH) to determine whether changes in circulating glucocorticoids are reflected in fGCM, concentrations and therefore to validate excreta as a matrix for monitoring endocrine status in a southern African passerine, the White-browed Sparrow-weaver (Plocepasser mahali) and a columbid, the Laughing Dove (Spilopelia capensis). We tested the suitability of four EIAs to quantify fGCMs in 10 individuals of each species. Two of the EIAs, tetrahydrocorticosterone and 11-Oxoetiocholanolone II, detected significant elevations and were therefore most suitable for quantifying fGCMs in the White-browed Sparrow-weavers. In contrast, the 5α-pregnane-3β, 11β, 21-triol-20-one EIA detected the highest elevations in fGCM concentrations in the Laughing Doves. The lag time between stressor initiation (ACTH injection) and the resulting peak fGCM concentrations was ~2 h in both species. The validations presented here open opportunities for monitoring physiological responses in free-ranging individuals and contribute to our knowledge of the EIAs suitable for non-invasive quantification of avian fGCM concentrations.

KEYWORDS:

• ACTH challenge
• assay validation
• enzyme-immunoassay
• faecal glucocorticoid metabolites
• physiological stress

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed at https://doi.org/10.1080/01584197.2022.2158476

Additional information

Funding

This work was supported by the National Research Foundation of South Africa [Grant 119754 to AEM]. Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Research Foundation of South Africa.