Glucocorticoid concentration and parasitic load in a wild striped hyaena (Hyaena hyaena) population in Southern India

Abstract

Glucocorticoid levels (GCs) are an important parameter that infers the pathological condition of an organism. GCs can vary with life history stages like gender, age, and reproductive stage and signify the degree of allostatic load experienced. Deleterious increases in GCs can severely affect the wildlife population by suppressing the reproductive viability of individuals and may cause immunosuppressive, making the population more susceptible to parasitic load. We have studied the stress physiology and parasitic load across the life history stages in the striped hyaena population confined to the Moyar Valley of Mudumalai and Sathyamangalam Tiger Reserves. The fecal glucocorticoid metabolite concentrations were measured using cortisol enzyme immunoassay from 30 scats. Collected scats were categorized into adults, sub-adults, and juvenile age groups based on the size and colour of droppings. Sex of the scat samples was identified post-DNA extraction from their epithelial lining cells. Parasitic load from scats was quantified as the number of different parasites recorded through sucrose floatation and sedimentation techniques. We found no significant difference in GCs concentration and parasitic load across the life history stages, but juveniles were recorded to have the least parasitic load. The highest GCs concentration and parasitic load were recorded from adults and female individuals, while both parameters were found least among juvenile individuals. Though we did not observe any significant differences across life-history stages, this study provides the first baseline information on stress physiology and parasitic load in striped hyaenas, which could help further studies assess the impact of external perturbations on stress physiology.