Stable isotopes in yellow-bellied marmot (Marmota flaviventris) fossils reveal environmental stability in the late Quaternary of the Colorado Rocky Mountains

a r t i c l e i n f o High elevation plant and animal communities are considered extremely sensitive to environmental change. We investigated an exceptional fossil record of yellow-bellied marmot (Marmota flaviventris) specimens that was recovered from Cement Creek Cave (elev. 2860 m) and ranged in age from radiocarbon background circa 49.8 cal ka BP to ~1 cal ka BP. We coupled isotopic and radiocarbon measurements (δ 18 O, δD, δ 15 N, δ 13 C, and 14 C) of bone collagen from individually-AMS dated specimens of marmots to assess ecological responses by this species to environmental change over time in a high elevation basin in the Rocky Mountains of southwestern Colorado, USA. We find little change in all four isotope ratios over time, demonstrating considerable environmental stability during periods when the marmots were present. The stable ecology and the apparent persistence of the small mammal community in the cave fauna throughout the late Quaternary are in marked contrast to the changes that occurred in the large mammal community, including local extirpation and extinction, at the end of the Pleistocene. Introduction The late Quaternary climatic and environmental history of the southern Rocky Mountains is broadly known through multiple proxy indicators from this and adjacent regions. These proxies include speleothems (Asmerom et al. Although these data paint a generally consistent picture of changes over time, there is variation in the details. Of particular interest is the climate and environment of the Upper Gunnison Basin (UGB) of southwestern Colorado, where there is evidence of significant changes in temperature, precipitation and vegetation over the late Quaternary (e. Stable isotopic analyses of carbon and oxygen of bioapatite of yellow-bellied marmots (Marmota flaviventris) and bushy-tailed woodrats (Neotoma cinerea) from Cement Creek Cave in the UGB show no changes in diet across the Pleistocene– Holocene boundary; however, there was a shift in δ 13 C, which was attributed to changes in atmospheric CO 2 concentration that further influenced the carbon isotope ratio in herbaceous forage plants (McLean and Emslie, 2012). To obtain further insight into the apparent stability of a high-elevation rodent habitat across major climate events (last glacial maximum , Younger Dryas Chronozone, and the Pleistocene–Holocene transition) during the late Quaternary, we investigated the unique fossil record of marmots from Cement Creek Cave, which spans much of the past ~50 ka. We derived a series of individually-AMS dated specimens to provide better …