Stable isotope ecology of black rhinos (Diceros bicornis) in Kenya
Stable isotope and elemental ratios in hair are influenced by the environment, including both climate and geology. Stable carbon isotopes can be used to give estimates of the C4/CAM fraction of diets of herbivorous mammals; stable nitrogen isotopes are related to the local water deficit; strontium isotopes are determined by the local geology. We studied hair from rhinos in Kenya to determine spatial patterns in δ13C, δ15N, and 87Sr/86Sr ratios. The samples of rhino hair were collected during Kenya Wildlife Service translocation or veterinary activities. δ13C values showed diets dominated by C3 foods, but in some regions the diet, at least seasonally, contained significant quantities (i.e., > ca. 20%) of C4/CAM foods. δ15N values were related to water deficit, with higher δ15N values in regions with high water deficit. 87Sr/86Sr isotope ratios were found to be related to the local geological substrate suggesting that 87Sr/86Sr isotope ratios are provisionally useful for determining the origins of illegal wildlife materials in Kenya and elsewhere in Africa.
KeywordsIsotope ecology East Africa Diceros Conservation National parks Diet Rhinoceros
We thank the members of Kenya Wildlife Service for assistance in collecting rhino hair samples, Truman Young and Meave Leakey for collecting plant samples, and Nicholas Georgiadis for water and temperature data from the Laikipia region. We thank the government of Kenya for permission to do this work. We thank IsoForensics for making the Neptune MC-ICP-MS available for this study. This work was done under CITES permits US831854, US053837/9, US159997/9, and US08996A/9. Dr. Samuel Andanje died on 4 May 2015 while this manuscript was in the initial stages of preparation; the living authors are grateful to him for his work on this project.
Author contribution statement
TEC and SAA conceived and designed the experiments. TEC, SAA, FG, JMK, LK, JWK, CK, IL, and ANM carried out the field work and laboratory analyses were performed by ANM, CRA, DPF, LH, and SJT. TEC, SAA, and DPF analyzed the data. TEC and SAA wrote the manuscript.
- Emslie RH (2013) African rhinoceroses—latest trends in rhino numbers and poaching. CITES—CoP16 Inf. 51. An update to Doc 54-2-Annexe 2 from the IUCN Species Survival Commission’s (IUCN/SSC) African Rhino Specialist Group to the CITES Secretariat pursuant to Resolution Conf. 9.14 (Rev. CoP15), pp 54-2Google Scholar
- Ganqa NM, Scogings PF, Raats JG (2005) Diet selection and forage factors affecting woody plant selection by black rhinoceros in the Great Fish River Reserve, South Africa. S Afr J Wildl Res 35:77–83Google Scholar
- Kenya National Atlas (1962) Geological map of Kenya. Survey of Kenya. Nairobi, Kenya. 1 sheetGoogle Scholar
- Mackey GN, Fernandez DP (2011) American Geophysical Union Fall Meeting, San Francisco, CA, USAGoogle Scholar
- Ngene S, Bitok E, Mukeka J, Okita-Ouma B, Gakuya F, Omondi P, Kimitei K, Watol Y, Kimani J (2011) Census and ear-notching of black rhinoceros (Diceros bicornis michaeli) in Tsavo East National Park, Kenya. Pachyderm 49:61–69Google Scholar
- NOAA (2017) Carbon-13/carbon-12 ratios in carbon dioxide. https://www.esrl.noaa.gov/gmd/webdata/iadv/ccgg/graphs/pdfs/ccgg.MLO.co2c13.1.none.discrete.all.pdf. Downloaded on 11 March 2017
- Okita-Ouma B, Mijele D, Amin R, Gakuya F, Ndeereh D, Lekolool I, Omondi P, Woodley D, Litoroh M, Bakari J, Kock R (2008) Minimizing competition by removing elephants from a degraded Ngulia rhino sanctuary, Kenya. Pachyderm 44:80–87Google Scholar
- Okita-Ouma B, Amin R, Van Langevelde F, Leader-Williams N (2010) Density dependence and population dynamics of black rhinos (Diceros bicornis michaeli) in Kenya’s rhino sanctuaries. Afr J Ecol 48:791–799Google Scholar
- Patton F, Jones M (2007) Determining minimum population size and demographics of black rhinos in the Salient of Aberdare National Park, Kenya. Pachyderm 43:63–72Google Scholar
- Patton F, Campbell P, Parfet E (2007) Establishing a monitoring system for black rhinos in the Solio Game Reserve, central Kenya. Pachyderm 43:87–95Google Scholar
- Patton F, Campbell P, Parfet E (2008) Biological management of the high density black rhino population in Solio Game Reserve, central Kenya. Pachyderm 44:72–79Google Scholar
- Pienaar DJ, Hall-Martin AJ, Hitchins PM (1991) Horn growth rates of free-ranging white and black rhinoceros. Koedoe 34:97–105Google Scholar
- Quennel AM (1959) Geological map of Tanganyika. Geological Survey Department. Dodoma, Tanganyika (1 sheet)Google Scholar
- Spinage C (1994) Elephants. T. & A.D. Prosser, LondonGoogle Scholar