Combining studies of elephant movement patterns and overall diet with incidences of …

• Stable isotopes in elephant hair document migration patterns and diet changes
• Materials and Methods
• Results and Discussion
• Acknowledgements
• References
• Figures

Biology Articles » Zoology » Stable isotopes in elephant hair document migration patterns and diet changes

Stable isotopes in elephant hair document migration patterns and diet changes

- Stable isotopes in elephant hair document migration patterns and diet changes

Thure E. Cerling ^*, , , George Wittemyer , Henrik B. Rasmussen ^¶, Fritz Vollrath ^¶, Claire E. Cerling , Todd J. Robinson , and Iain Douglas-Hamilton ^||

^*Department of Geology and Geophysics, 135 South 1460 East, University of Utah, Salt Lake City, UT 84112; Department of Biology, 257 South 1400 East, University of Utah, Salt Lake City, UT 84112; University of California, Berkeley, CA 94720; ^¶Department of Zoology, Oxford University, Oxford OX1 3PS, United Kingdom; and ^||Save The Elephants Foundation, Nairobi, Kenya

Contributed by Thure E. Cerling, November 4, 2005

Abstract

We use chronologies of stable isotopes measured from elephant(Loxodonta africana) hair to determine migration patterns andseasonal diet changes in elephants in and near Samburu NationalReserve in northern Kenya. Stable carbon isotopes record dietchanges, principally enabling differentiation between browseand tropical grasses, which use the C₃ and C₄ photosyntheticpathways, respectively; stable nitrogen isotopes record regionalpatterns related to aridity, offering insight into localizedranging behavior. Isotopically identified range shifts werecorroborated by global positioning system radio tracking dataof the studied individuals. Comparison of the stable isotoperecord in the hair of one migrant individual with that of aresident population shows important differences in feeding andranging behavior over time. Our analysis indicates that differencesare the result of excursions into mesic environments coupledwith intermittent crop raiding by the migrant individual. Variationin diet, quantified by using stable isotopes, can offer insightinto diet-related wildlife behavior.

13-carbon | 15-nitrogen | chronology | human–elephant conflict

Source: PNAS, January 10, 2006, vol. 103, no. 2, 371-373

The stable isotope ratios of ¹³C/¹²C in hair records the dietof mammals (1–4). It is particularly useful in distinguishingdiets of C₃ browse versus C₄ grass in tropical regions (5–7)because of the large difference in ¹³C/¹²C ratios between plantsusing the C₃ and C₄ photosynthetic pathways, respectively. Intropical regions, the C₃ pathway is used primarily by treesand shrubs, whereas plants using the C₄ pathway are principallygrasses (8, 9).

Hair is a particularly useful indicator of diet change (3, 4)because the isotope turnover of mammal tissues is high enoughto resolve short-term diet changes. Recent advances in methodology,progressed through the study of large mammals with controlleddiet changes (10, 11), allows detailed reconstruction of thediet history of individual large mammals in wild populations(12, 13).

In this study, we determine the growth rates and stable ¹³C/¹²Cand ¹⁵N/¹⁴N ratios in elephant hair collected between 2001 and2004. We focus on the behavior of a resident population of SamburuNational Reserve, Northern Kenya, for the time period of 2000to 2002. We compare stable isotope results of this residentpopulation with a migrant elephant (B1013) that visited SamburuReserve up to several times each year. Differences in isotoperatios between the resident individuals and the migrant indicatedifferent behaviors, including rapid migration across long distancesby the migrant individual and differences in the fraction C₄biomass in the diet. The latter may be related to seasonal cropraiding, which can be quantified by using stable isotope ratios.