MAMMALIAN SPECIES ABUNDANCES AS CLIMATIC INDICATORS IN HALL’S CAVE, TEXAS

Correlations exist between both the absolute and relative abundance of certain mammal groups (i.e. Arvicolinae, Lagomorpha, Carnivora) and climatic values in modern ecosystems. This could become a potentially valuable method of paleoecologic reconstruction. The advantage of this method is that it is not dependent on particular individual taxa; rather it simply looks at the number or proportion of species to estimate climate variables. To test the correlations we plotted the temperature, precipitation, range of temperature, and frost-free days against the number of species of various mammal groups found in an ecoregion. Ecoregions were previously delimited for all of North America based upon biologic and physical parameters. The equation of the linear regression for each plot can then be used to return temperature or another climatic variable when the number of species is known.

We applied these correlations from modern ecosystems to late Pleistocene through Holocene assemblages of mammals from Hall’s Cave, Kerr County, Texas. Caves found on the Edwards Plateau provide a great deal of information on the Quaternary mammals of Texas, but Hall’s Cave is unique because it provides a nearly continuous record of the Holocene. This cave is stratified and extensively AMS carbon dated. To accurately test whether species numbers can provide paleoclimate data, an independent climate signal is needed. We utilized a combination of climate signals to eliminate potential biases associated with each method. Climate data were taken from previously established pollen records, stable isotopes, and climate models. We began by studying the Holocene because the climate and mammals should be most similar to today. The larger goal of this project is to determine the temporal limits and applicability of this method to paleoecology.