MAMMOTHS AND MASTODONS IN THE GREAT LAKES: NEW DATA ON THE CHRONOLOGY AND PALEOECOLOGY OF EXTINCTION

The North American Midwest has one of the highest densities of terminal Pleistocene proboscideans on the continent. Although regionally dominated by the American Mastodont (Mammut americanum), two species of mammoths (Mammuthus primigenius and M. jeffersonii) are also sympatric. A recent census of Proboscidea in regional museum collections produced a dataset of >1600 specimens, vouchering 576 different localities. Although single-animal localities are by far the most common, multi-animal and multi-taxic assemblages are also present. During the Last-Glacial-Maximum (LGM), Mammuthus is the dominant proboscidean across the midwestern landscape. Mammut is rare or absent from the region during this time. During the subsequent post-LGM period, Mammut becomes the dominant taxon in forested and parkland habitats east of the Mississippi River and throughout the Ozark uplift. At this time, Mammuthus are more common in grassland habitats in the western part of the study area, although they maintain small local populations in forested and parkland areas until their local extirpation at 13,470 cal BP (~11,630 14C BP). Two mastodons from Schimelphenig Bog, WI (~12,700 cal BP; ~10,800 14C BP) are the only proboscideans from the region to survive into the Younger Dryas. Most multi-animal death assemblages occur within 500 years of the terminal extinction date. Against this regional background, demonstrated human or carnivore impacts on proboscideans are extremely rare, despite the ubiquity of natural death assemblages.