| Description |
Stable isotope analysis of biological and geological materials has provided important information on environmental change over many timescales. Such records rely on an interpretive framework of large isotopic datasets of recent (i.e., modern and/or Holocene-aged) material in order to define paleoecological interpretations. This dissertation will contribute to a better understanding of ancient and historical ecological change in East Africa by (1) providing a modern interpretive framework for a megaherbivore, Hippopotamus amphibius, in East Africa and (2) investigating the relationship between climate and ecology in Kenya during the Holocene using multiproxy records, including stable isotopes of large mammalian herbivores and leaf wax biomarker isotopes. Although H. amphibius (hippo) tooth enamel isotopes are widely used to understand paleoenvironment, little is known about their dietary variability across time and space. In this dissertation, I present an extensive study on stable isotope serial samples (δ13C and δ18O) of modern hippos in order to understand the breadth of their dietary and behavioral flexibility in Kenya. This large dataset (10 mm interval samples of canine tooth enamel for 30 hippo canines; 1,410 samples in total) reveals the remarkable dietary diversity of hippos: they are indiscriminate feeders and can consume both C3 and C4 herbaceous forage. Furthermore, certain profiles with known death dates have captured isotopic indicators of ecological perturbations, such as drought and C3 plant encroachment following elephant extirpation. Multiproxy records of ecology can provide even more paleoecological information than single-mammal records. Assumptions about environmental change in the fossil record are often based on inference from known global climate and presumed changes in ecology. Using a multiproxy approach (tooth enamel isotopes and leaf wax biomarkers), I present Holocene (11.8 Kya - present) paleoecological data from two basins: the arid Turkana Basin in northern Kenya and the more mesic Victoria Basin in southwestern Kenya. These data indicate that as the monsoon was weakening due to global climatic change (i.e, Milankovitch forcing), there was an increase in C3 resources (bush, shrub, trees, and herbs) in Turkana, whereas Lake Victoria remained predominately C4 (tropical lowland grasses). This interbasinal record reveals that we cannot make assumptions about changes in ecology in an entire region based on climatological forcing mechanisms alone. |
