#35 - Enamel isotopes reveal late Pleistocene ecosystem dynamics in southeastern North America

The end of the late Pleistocene (~10,000 years ago) witnessed the extinction of over seventy percent of North America’s megafaunal genera. Although this pattern has been extensively investigated, its causal mechanisms remain elusive. Much of this difficulty is related to the spatial and temporal discontinuity of sites dating to the period leading up to the extinctions. Due to its removal from glacial conditions, southeastern North America provides a unique window into ecosystem dynamics just prior to human arrival in the region. In this study, we present new stable carbon and oxygen isotope data from Mammuthus columbiand Bison latifronsteeth collected from a well-dated Last Glacial Maximum (~20,000 rcybp) locality called Clark Quarry in coastal Georgia, USA. We compare these data to those from similarly aged (middle and late Rancholabrean) localities from Florida and demonstrate the presence of a vegetation gradient with elevated levels of C3vegetation at higher latitudes. We hypothesize that this pattern may have contributed to previously described migratory patterns of mastodon (Mammut) populations in southeastern North America. Serially-sampled δ13C and δ18O values suggest that Clark Quarry Mammuthus and Bison changed their diet seasonally with the incorporation of elevated quantities of C4vegetation during warmer periods. Our data indicate more exaggerated seasonal dietary variability in these taxa at Clark Quarry relative to those collected from the interglacial locality of Waccasassa River in Florida, providing additional evidence for the significant influence of glacial dynamics in structuring North American ecosystems

CAN ANCIENT FELIDS AND CANIDS BE DISTINGUISHED BASED UPON THEIR TOOTH MARKS? A CASE STUDY ON MODERN BONES

Predator-prey relationships are vital for structuring modern ecosystems but have been especially challenging to investigate in the fossil record. Although there is abundant evidence of carnivore presence in ancient ecosystems in the form of behavioral traces (e.g., tooth marks), their fossils are rare relative to the animals they ingest. In this study, we use a large sample (n = 33) of modern Bos taurus (cow) tibia that have been processed by Canis lupus (wolf) and Panthera leo (lion) to assess whether morphology and location of tooth marks can be used to distinguish canids and felids in the fossil record. The tibia were divided into three sections (proximal, middle, distal) based upon their total length. Based upon previously published studies and our own observations, a new categorization scheme was developed for this study to characterize each tooth mark within these three regions. Our preliminary results indicate that the overall size and position of tooth marks can be used to distinguish wolf and lion behavioral traces. In particular, we find that lions and wolves differ in the manner by which they process the proximal end of cow tibia. These results could infer that lions prefer areas with higher flesh to bone ratios, which is consistent with interpretations based upon dental morphology. This study indicates that behavioral traces on fossils could be the key to unlocking predator-prey relationships in the fossil record

23. Lion and wolf tooth mark frequency and morphology as a model for ancient carnivore bone damage

Predator-prey relationships are vital for structuring modern ecosystems, but have been especially challenging to investigate in the fossil record. Although there is abundant evidence of carnivore presence in ancient ecosystems in the form of behavioral traces (e.g., tooth marks), their fossils are rare relative to the animals they ingest. In this study, we use a large sample (n = 33) of modern Bos taurus (cow) tibia that have been processed by Canis lupus (wolf) and Panthera leo (lion) to assess whether morphology and location of tooth marks can be used to distinguish canids and felids in the fossil record. The tibia were divided into three sections (i.e., proximal, middle, distal) based upon their overall length. We developed a new categorization scheme (based upon published literature and our own observations) to characterize each tooth mark within these three regions. Our preliminary results indicate that the overall size and position of tooth marks can be used to distinguish wolf and lion behavioral traces. In particular, we find that lion and wolf differ in the manner by which they process the proximal end of cow tibia. This could indicate that lions prefer areas with higher flesh to bone ratios, which is consistent with interpretations based upon dental morphology. This study indicates that behavioral traces on fossils could be the key to unlocking predator-prey relationships in the fossil record

SEASONAL CHANGES IN REPTILE DIVERSITY AND DISTRIBUTION ACROSS VARYING ENVIRONMENTS IN SMITHGALL WOODS STATE PARK, WHTE COUNTY, GEORGIA**

Reptiles are essential to the health of North Georgia ecosystems, primarily by acting as important components of the food webs that aid in population control of insects and small rodents. Additionally, due to their ectothermic physiology, reptiles are sensitive to environmental alterations resulting from climate change and other anthropogenic activities. Understanding the diversity and distribution of these populations in heterogenous environments across seasons can provide essential information for conservation and management strategies, as well as a better understanding of the impact of climate change on these organisms. In this study, we present data on three sites located within Smithgall Woods State Park (SWSP) in White County, Georgia. Each study site has distinctive environmental differences in regard to elevation, terrain, vegetation, and canopy coverage. Habitat assessments were performed in each site, and an ongoing extensive survey of snake and turtle populations is being implemented during each season of the year. All individuals captured are marked with a unique code, and a series of morphological measurements (e.g., carapace dimensions, snout to vent length) and health assessments (e.g., presence of scarring, fungal infections, external parasites) are taken to quantify changes in individuals and the population across time. Using these data, we will be able to determine if there are certain periods of the year or environmental circumstances where reptiles are especially susceptible to harm. This information can then be used to implement management and conservation strategies targeting taxa and localities (within SWSP) that are particularly vulnerable during certain periods of the year. These strategies can then provide a framework for similar localities around Northeast Georgia

Enamel isotopes reveal late Pleistocene ecosystem dynamics in southeastern North America

The end of the late Pleistocene (∼10,000 years ago) witnessed the extinction of over seventy percent of North America\u27s megafaunal genera. Although this pattern has been extensively investigated, its causal mechanisms remain elusive. Much of this difficulty is related to the spatial and temporal discontinuity of sites dating to the period leading up to the extinctions. In this study, we present new stable carbon and oxygen isotope data from Mammuthus columbi and Bison latifrons teeth collected from a well-dated Last Glacial Maximum (∼20,000 rcybp) locality called Clark Quarry in coastal Georgia, USA. This site lies in direct proximity to where Sir Charles Lyell collected the type specimen of M. columbi in 1846 and therefore is of added historical significance. We compare these data to those from similarly aged (Sangamonian interglacial and Wisconsin glacial intervals) localities from Florida and demonstrate the presence of a vegetation gradient with elevated levels of C3 vegetation at higher latitudes. Serially-sampled δ13C and δ18O values suggest that Clark Quarry Mammuthus and Bison changed their diet seasonally with the incorporation of elevated quantities of C4 vegetation during warmer periods. Our data indicate more exaggerated seasonal dietary variability in these taxa at Clark Quarry relative to those collected from the Sangamonian interglacial locality of Waccasassa River in Florida, providing additional evidence for the significant influence of glacial dynamics in structuring North American ecosystems. These high-resolution ecological patterns should be incorporated into hypotheses focused on extinction dynamics in southeastern North America and more broadly