Chris Widga1, Stacey Lengyel1, Greg Hodgins2, Jeff Saunders1, J. Douglas Walker3
1. Landscape History Program, Illinois State Museum, Springfield, IL 2. University of Arizona-NSF AMS Facility, Tucson, AZ 3. Department of Geology, University of Kansas, Lawrence, KS
The factors underlying the extinction of 35 genera of North American mammals during the terminal Pleistocene have incited lively debate for over a century. At issue is whether the primary driver of extinctions was human hunting or climate-related landscape changes, the impact of other proposed catastrophic processes on megafaunal populations, or any combination of the above. Unfortunately, ambiguity in the timing of regional proboscidean extinctions has complicated rigorous comparisons of actual extinction events to cultural and climatic timelines. This study will improve the late Quaternary chronology of proboscidean extinctions in the Great Lakes region through direct dating of ~80 mammoth and mastodont assemblages from the study area, a region where these extinctions appear particularly protracted. The project will also refine our understanding of regional evolution in proboscidean ecological niches by examining isotopic records of animal diet (ä13C), seasonality (ä18O), and mobility (87Sr/86Sr) in teeth and bones, as well as skeletal records of individual life histories (e.g., growth rate, pathology). These datasets will be used to define changes in the niche structure of Proboscidea during the last ~50 ka, and to subsequently examine the niche structure of terminal Pleistocene proboscideans in light of these long-term patterns. These parallel chronological and paleoecological studies will be used to elucidate factors underlying presumed changes in proboscidean ecological niches immediately prior to extinction, and to examine the relative importance of proposed extinction processes (e.g., human hunting, vegetation changes) in the disappearance of proboscideans from the Great Lakes region. Dated proboscidean remains, when combined with analyses of individual life histories, diet, and mobility patterns, will offer insight into the structure of terminal Pleistocene ecosystems of the Great Lakes region, including the relative importance of proposed extinction drivers. This project also has the potential to identify ecological thresholds that are important to maintaining the viability of modern large mammal populations when exposed to rapidly changing climate conditions.
