1) Department of Geology and Geophysics, 135 South 1460 East, University of Utah, Salt Lake City, UT 84112, USA, 2) Department of Biology, 257 South 1400 East, University of Utah, Salt Lake City, UT 84112, USA, 3) University of California, Berkeley, CA 94720, USA, 4) Department of Zoology, Oxford University, Oxford OX1 3PS, United Kingdom, 5) Save The Elephants Foundation, Nairobi, Kenya Proceedings of the National Academy of Sciences of the USA (2006), V103 (2), pp371–373, doi: 10.1073/pnas.0509606102 Stable isotopes in elephant hair document migration patterns and diet changes Thure E. Cerling (1,2), George Wittemyer (3), Henrik B. Rasmussen (4), Fritz Vollrath (4), Claire E. Cerling (2), Todd J. Robinson (2) and Iain Douglas-Hamilton (5) We use chronologies of stable isotopes measured from elephant (Loxodonta africana) hair to determine migration patterns and seasonal diet changes in elephants in and near Samburu National Reserve in northern Kenya. Stable carbon isotopes record diet changes, principally enabling differentiation between browse and tropical grasses, which use the C3 and C4 photosynthetic pathways, respectively; stable nitrogen isotopes record regional patterns related to aridity, offering insight into localized ranging behavior. Isotopically identified range shifts were corroborated by global positioning system radio tracking data of the studied individuals. Comparison of the stable isotope record in the hair of one migrant individual with that of a resident population shows important differences in feeding and ranging behavior over time. Our analysis indicates that differences are the result of excursions into mesic environments coupled with intermittent crop raiding by the migrant individual. Variation in diet, quantified by using stable isotopes, can offer insight into diet-related wildlife behavior.