STABLE ISOTOPIC STUDY OF MODERN AND FOSSIL TRAGELAPHUS: INTERPRETING THE RANGE OF DIETARY SIGNALS WITHIN A SINGLE GENUS

Understanding the dietary adaptations of mammalian fauna has potential implications for inferring their habitat preference. As bovid remains dominate most Pliocene and Pleistocene fossil sites in eastern Africa, stable isotopic studies using bovid dental remains to infer paleodiet is an important way forward to assess paleoenvironments. However, this is hampered by the fact that bovid teeth are not often attributable beyond the tribe level. Thus, it is crucial to explore the range of variations observable within a single tribe. To achieve this, we studied stable carbon isotopic composition of tooth enamel from contemporaneous modern and fossil Tragelaphus species. Modern Tragelaphus is represented here by four species (with a total of 21 specimens collected from five national parks in Ethiopia) namely Tragelaphus buxtoni, Tragelaphus imberbis, Tragelaphus strepsiceros and Tragelaphus scriptus. Overall, it can be said that the four modern species of Tragelaphus analyzed show a more constrained adaptation to C₃ dominated diets. Contemporaneous fossil Tragelaphus sampled here consist of two species: Tragelaphus nakuae (31 specimens) and Tragelaphus gaudryi (21 specimens) from Members E to G in the Shungura Formation, Omo Basin, Ethiopia. In general, although it can be said that both species cover mainly the mixed C₃/C₄ spectrum, differences are observed in the different members. From this study it can be suggested that although modern species may not be very good representatives to infer the diet of fossil species, contemporaneous modern and fossil species within the same genus, at a given time, have similar dietary preferences. However, there may be differences in niche partitioning between species within a given habitat and especially between those belonging to different genera. Larger sample sizes of isotopic data combined with other proxies including detailed field observations of living species might provide a better insight into the dietary evolution and niche partitioning of different species within a given environment.