Establishing enzyme immunoassays for quantifying fecal glucocorticoid metabolites in six southern African rodents using biological and physiological stimuli

Abstract

Introduction Global landscape transformations and increased resource use are leading to an overall decline in ecosystem health and natural habitat quality. Due to their low trophic position, small body size, and close association with environmental conditions, rodents can serve as effective biological indicators of ecosystem health and anthropogenic disturbance by monitoring their behavior and physiology, specifically stress-related endocrine responses. This study aimed to establish minimally invasive methods for quantifying fecal glucocorticoid metabolites (fGCMs) in six southern African rodent species ( Aethomys ineptus, Lemniscomys rosalia, Mastomys coucha, Micaelamys namaquensis, Otomys angoniensis, and Steatomys pratensis ). Methods Where possible, one male and one female from each species were live trapped in the Magaliesberg Biosphere, North West province, South Africa, and individually housed on-site for enzyme immunoassay (EIA) validation experiments. Biological (handling and temporary removal from enclosure) and physiological (Synacthen-induced adrenocorticotropic hormone or ACTH challenge test) stimuli were administered, and fGCM concentrations were determined from samples collected before, during, and after each intervention. Results and discussion A 5α-pregnane-3β,11β,21-triol-20-one EIA (detecting fGCMs with a 5α-3β, 11β-diol structure) was identified as the most suitable assay across all six species assessed. Two additional EIAs appear suitable for some of the species tested: Oxoetiocholanolone II, measuring fGCMs with a 5β-3α-ol-11-one structure ( A. ineptus, O. angoniensis, and S. pratensis ); and a Corticosterone EIA ( M. coucha, O. angoniensis, and S. pratensis ). Establishing and validating minimally invasive techniques for monitoring stress-related animal responses in rodents can be beneficial for evaluating the impact of anthropogenic disturbances on natural environments and their associated fauna.