| Fossil tooth enamel from a diverse assemblage of carnivores and herbivores collected from Natural Trap Cave (NTC, 18 taxa, Bighorn Mountains) and Little Box Elder Cave (LBEC, 13 taxa, Laramie Mountains) were analyzed for carbon and oxygen isotope compositions to reconstruct paleodietary as well as paleoclimate information for late Pleistocene Wyoming. NTC contains stratified fossil assemblages from the Sangamonian interglacial (∼110,000 YBP), the pre-last glacial maximum (23-25,000 YBP), the last glacial maximum (LGM, 20-22,000 YBP), the post LGM (14-17,000 YBP), the Younger Dryas (12-13,000 YBP), and the latest Pleistocene to Holocene (<12,000 YBP). LBEC contains latest Wisconsinan (10-12,000 YBP) to Holocene faunas. Tooth enamel delta13C values from NTC demonstrate the dominance of C3 vegetation during glacial times and the presence of C4 during interglacial times. Large ranges in delta 13C values reflect diet variation, while similar delta 13C values among glacial taxa do not generally allow interpretation for resource/niche partitioning. However, NTC Bison and Equus demonstrate the presence of C4 grasses during Sangamonian interglacial, pre-LGM, and post LGM times, when the climate was likely more favorable for C4 growth. delta18O values from NTC demonstrate differences in precipitation between glacial and interglacial periods and are broadly consistent with changes in atmospheric circulation patterns during glacial vs. interglacial times. Differences in delta18O values among bovids, horses, antelope, and caprines also demonstrate differences in water dependencies. Carnivores exhibit more negative delta13C values and more positive delta18O values relative to herbivores; these offsets differ from modern data and suggest the need for further study. With the exception of Bison and Canis lupus, co-occurring taxa from both caves demonstrate statistical differences in isotopic compositions, signifying spatial differences in ecologies between southern (Laramie) and northern (Bighorn) Wyoming. |
