Abstract:
The brown hyaena (Hyaena brunnea) is the least known of the large predators of southern Africa.
The current IUCN status of the brown hyaena is “Near Threatened”, and there are conservation
concerns related to a general lack of biological knowledge of the species. For instance, a better
knowledge of the responses to environmental and social stressors would improve our abilities to
sustainably manage brown hyaena populations in both captive and free-ranging environments. We
conducted adrenocorticotrophic hormone (ACTH) challenges in one female and one male adult
brown hyaena at Lion Park Zoo, South Africa, to validate measurements of glucocorticoid
metabolites (GCM) in brown hyaena faeces via an enzyme linked immunoassay (EIA). We also
measured gastrointestinal transit times (GIT times) and the GCM degradation in faeces left in
ambient temperature for up to 32 hours to more reliably assess the use of this assay as a tool for
non-invasive glucocorticoid measurements. Intramuscular injections of synthetic ACTH yielded
GCM levels of 388% (female) and 2682% (male) above baseline with peak increases occurring 25-
40 hours post injection. The time delay of faecal GCM excretion approximately corresponded with
food transit time in the brown hyaenas. Faecal GCM levels declined significantly over time since
defecation. Our results provided a good validation that faecal GCM's accurately reflects circulating
glucocorticoid stress hormones in brown hyaenas, but we highlight that samples have to be frozen
immediately after defecation to avoid bias in the measurements due to bacterial degredation.
