Thermoregulation and dental isotopes reveal the behavior and environment of Pleistocene megafauna at Waco Mammoth National Monument.

Waco Mammoth National Monument (WMNM) in central Texas is a significant Pleistocene paleontological site, containing at least 16 Columbian mammoths and specimens of 12 other vertebrate taxa. Interpreting this site, however, is contingent on understanding both the environment Pleistocene animals lived in and how they interacted with that environment behaviorally. Actualistic studies of modern analogs can be used to better understand the behavior and geographic range of a Pleistocene animal and thus increase their usefulness as paleoclimate and paleoenvironmental indicators. Mass and thermal modeling studies done on modern tortoises have been used to determine the temperature tolerance of the giant tortoise species of central Texas, constraining the climate present at WMNM during its formation. Understanding the long-term movements of a fossil organism can reflect the environment it lives in. Strontium isotope ratio analysis of megafaunal teeth from WMNM have shown that not all of the mammoths at the site shared a geographic origin. The behavior revealed – mammoths congregated at WMNM from over a wide area – necessitated a reconsideration of the long-standing mechanism of death for the megafauna there. Serial analysis of carbon and oxygen isotopes from the same teeth revealed that while the animals at WMNM shared a diet, some may have had distinct sources of drinking water. They also reveal that the WMNM megafauna lived in a drier, more drought-prone world that previously thought. Taking a multi-proxy approach to better understand interactions between Pleistocene megafauna and the environmental changes they experienced should inform our attempts to conserve our remaining megafauna.