Abstract
It is important to understand the physiological stressors in animals especially for threatened species or intensively managed to improve their conservation and optimise their reproduction. We sought to understand changes in stress hormones (faecal glucocorticoid metabolites) in black rhinoceros (Diceros bicornis michaeli) in relation to population density and sex (intrinsic factors) and plant minerals, rainfall and land surface temperature (extrinsic factors). We used non-invasive faecal sampling techniques on animals of known sex, age and dominance in seven populations of contrasting population densities over 1 year. We measured variability in faecal corticosterone metabolites through radioimmunoassay and related them to population density, sex and faecal calcium, phosphorus, copper, zinc and potassium as characteristic of plant minerals, rainfall and temperature. We used linear mixed models (LMM) to analyse the data. We did not detect a significant relationship between physiological stress parameters and population density. However, we have indications that stress levels increased as rainfall and temperature increased and were correlated negatively and positively with concentration of faecal phosphorus and copper respectively; we found higher stress levels in females than in males. These results suggest that both intrinsic and extrinsic factors explain the variation in physiological stress observed in black rhinoceros.
Original language | English |
---|---|
Article number | e13239 |
Journal | African Journal of Ecology |
Volume | 62 |
Issue number | 1 |
DOIs | |
State | Published - Jan 2024 |
Funding
Rhinoceros monitoring staff helped in collecting faecal samples. WWF Kenya and Mohamed bin Zayed Species Conservation Fund financed sample collection and shipping costs. Ol Jogi Ranch and Ngulia Safari Lodge provided extra freezers for storing samples in the field. Hesbon Odongo of University of Nairobi and Paul Okwach of Pathcare Kenya Laboratories helped with the initial trialling of hormonal assays. Frank Basiye of KEMRI and George Owiti-Otiang’ helped with the contacts to local laboratories. Hawi Jane helped with sorting faecal samples during storage. Domnic Mijele and Abraham Sangula facilitated testing of samples for Foot-and-Mouth Disease. Frank van Langevelde, Ignas Heitkonig, Sip E. van Wieren, Rajan Amin and George Agogo provided invaluable insights and inputs into the initial drafts of this manuscript. So did Shelley Waterland and Yussuf Wato provide useful comments. Rami Woods of University of Missouri is thanked for assisting in assaying faecal glucocorticoid metabolites. Finally, we sincerely thank the peer reviewers for their insights that improved this article.
Funders | Funder number |
---|---|
Kenya Medical Research Institute |
Keywords
- black rhinoceros
- corticosterone
- density
- faecal minerals
- physiological stress
- rainfall
- sex
- temperature