Abstract
This is a multi-individual (n = 11), stable carbon and nitrogen isotope study of bone collagen (δ13Ccol and δ15Ncol) from the giant beaver (genus Castoroides). The now-extinct giant beaver was once one of the most widespread Pleistocene megafauna in North America. We confirm that Castoroides consumed a diet of predominantly submerged aquatic macrophytes. These dietary preferences rendered the giant beaver highly dependent on wetland habitat for survival. Castoroides’ δ13Ccol and δ15Ncol do not support the hypothesis that the giant beaver consumed trees or woody plants, which suggests that it did not share the same behaviours as Castor (i.e., tree-cutting and harvesting). The onset of warmer, more arid conditions likely contributed to the extinction of Castoroides. Six new radiocarbon dates help establish the chronology of the northward dispersal of the giant beaver in Beringia, indicating a correlation with ice sheet retreat.
Highlights
This is a multi-individual (n = 11), stable carbon and nitrogen isotope study of bone collagen (δ13Ccol and δ15Ncol) from the giant beaver
We use stable isotopes to explore the ecology of Castoroides, which allows us to better understand its diet, its impact on the surrounding Pleistocene landscape, and the mechanisms that led to its demise
Previous studies based on stable isotope analysis of single specimens suggest that the giant beaver consumed aquatic vegetation, and thrived in mid-latitude regions of North America during warm, strongly seasonal conditions between 125,000 and 75,000 BP14,15
Summary
The presence of giant beaver fossils in high latitude regions such as Alaska and Yukon Territory confirm it could persist through harsh arctic climatic and low light conditions in the winter It is unknown if Castoroides shared any behavioural characteristics with the genus Castor, and the possibility that the giant beaver engineered its habitat by constructing dams or lodges remains a topic of debate[1,17,20,21,22,23,24]. The first model predicts that Castoroides filled an econiche similar to that of the muskrat (Ondatra zibethicus), as a semi-aquatic rodent that primarily consumed submerged and emergent freshwater macrophytes in calm wetlands with an expansive littoral zone[14,19,20,21]. The bulk of its diet would have been foliage from deciduous trees and its engineering habits would have promoted local biotic diversity and significantly impacted the hydrological patterns of the Pleistocene landscape
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