PALEOBIOLOGICAL AND PALEOENVIRONMENTAL IMPLICATIONS OF ISOTOPIC ANALYSES OF PREHISTORIC BISON FROM WYOMING

Isotopic analyses of fossil and archaeological bison remains can provide information about the biology of prehistoric bison as well the paleoenvironmental conditions in which they lived. The oxygen isotope ratios of bison bones and teeth vary with the oxygen isotope ratios of local precipitation, which in turn varies with location and climate. The carbon isotope ratios of bison reflect the carbon isotope ratio of dietary plants; since bison are primarily grazers (i.e., their diet typically consists of at least 90% grass), the carbon isotope ratios of bison reflects the C-3/ C-4 ratio of local grasslands. The relatively high abundance of bison in many archeological site make this taxa of particularly interest to researchers interested in reconstruction Holocene climates in North America. We have analyzed the isotopic values of the teeth of bison from two archeological sites in Wyoming that are Late Prehistoric in age: the Vore and Big Goose Creek bison jumps. We compared the values of archaeological bison with the values of teeth from modern feral bison from five sites in Montana, North Dakota, South Dakota, and Wyoming. The carbon isotope ratios of the teeth archeological bison display a significantly greater range of values than the values of modern bison from the northern Great Plains, suggesting that archeological bison ranged further than their modern counterparts, which are currently restricted to the boundaries of National Parks and preserves. The oxygen isotope ratios of archeological bison do not display a significantly greater range than modern bison, but mean values are slightly lower than their closest modern counterparts.