Isotopic Reconstruction of Home Range and Migration in Extinct Mammals

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9725854 Koch Migration patterns, dispersal, and home range are important attributes of the biology of living animals that have proven difficult to reconstruct for extinct species. Current methods, based on analogy to modern relatives, scaling relationships, or taphonomic interpretations of multiple individual sites are either controversial or they lack resolution. Migration and home range have figured prominently in ongoing debates about susceptibility to extinction, differences in speciation rates, biogeographic patterns, and patterns of co-evolution between predator and prey. Clearly, a method for determining the scale of animal movement is essential. Strontium exhibits geologically-controlled spatial variation in the isotope composition, whereas oxygen isotopes differ among regions due to climatic differences. Animals consume vegetation and drinking water and ingest the Sr and O isotope signature characteristic of their local environment. Consequently analysis of isotopic variations within and among individuals may indicate the habitat and movement patterns of individual animals. This study has three sections. First, the susceptibility of tooth enamel apatite to diagenetic alteration will be examined through analysis marine fossils deposited in sediments derived from the continent. This study will reveal if biogenic 87Sr/86Sr, phosphate (18O, and carbonate (18O values are preserved in bioapatite of progressively older fossils, and assess the rate and mechanism of alteration. This will be the first test of the isotopic fidelity of Sr in enamel, and the first attempt to examine whether known phosphate (18O values can be retrieved from ancient enamel and bone bioapatite. A second study will take advantage of the extremely low Sr isotope variability in peninsular Florida to examine home range size and migration in extinct Pleistocene proboscideans. The study will reveal if late Pleistocene proboscideans had large or small home ranges, if they undertook seasonal migrations, and if either of these attributes of range use changed between full glacial and late glacial ecosystems. Finally, it has been proposed that Paleo-Indian hunters efficiently stalked and killed entire elephant family groups. The empirical support for this conclusion, the age structure of multiple death sites, has been controversial. Large Sr or O isotopic differences among samples in enamel deposited in the last few years of life would falsify the family group's hypothesis. Overall, isotopic analysis has the potential to cast new light on old debates regarding animal movement, and it supplies a new method for detecting time or spatial averaging in a multi-individual sample.