Stable isotope ecology of fossil hippopotamids from the Lake Turkana Basin of East Africa

The diet of African hippopotamids can be documented through δ13C analyses of enamel and other tissues. Analysis of a 10-million-year sequence of hippopotamids in and near the Lake Turkana Basin of northern Kenya shows that hippos have included a substantial fraction of C 3 vegetation in their diets since the late Miocene when C4 vegetation first appears in hippo diet as a measurable fraction. The C 4 component of vegetation becomes dominant (>50%) by Upper Burgi time (c. 2 million years ago) but does not reach 100% for all individuals. It is therefore not unexpected that the δ13C values of modern hippopotamids show a higher fraction of dietary C3 biomass than has been estimated from traditional observations. Analysis of δ18O of hippos from different stratigraphic levels shows no systematic trend over time; the average value for fossil hippos over the last 10 million years is similar to that of modern hippos from the Omo River system. © 2008 The Authors.