Electronic Thesis and Dissertation Repository


Master of Science




Fred J. Longstaffe


Stable isotope analysis was used to explore unresolved questions about the palaeoecology of the extinct Pleistocene giant beaver (Castoroides). The δ13C, δ15N, and δ18O of bone collagen and structural carbonate from enamel served as proxies for palaeodiet and palaeoclimate. A new baseline for freshwater and terrestrial plant δ13C and δ15N was utilized in a mixing model (SIAR) to assess rodent feeding niche. SIAR analysis indicated that Castoroides’ consumed a diet of predominantly macrophytes, making them reliant on wetland habitat for food. Based on isotopic data for potential modern analog species (Castor and Ondatra), SIAR also indicated that Castor and Castoroides occupied complementary dietary niches, allowing them to share habitat space throughout the Pleistocene. The δ13C and δ18O of Castoroides’ ever-growing incisors also recorded seasonal fluctuations in diet and climate. Wetland loss due to climate change during the Last Glacial Maximum, and increased competition for habitat, probably factored into Castoroides’ extinction.