Using Stable Isotopes to Understand Survival versus Extinction of Late Pleistocene Muskoxen
This thesis uses stable isotopes to investigate the adaptive advantages of Ovibos moschatus, a muskox, relative to now-extinct Pleistocene megafauna in eastern Beringia (Yukon Territory and Alaska), including another muskox Bootherium bombifrons. Ecological niches were defined for Ovibos and Boother...
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| Format: | Text |
| Language: | English |
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Scholarship@Western
2019
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| Online Access: | https://ir.lib.uwo.ca/etd/6334 https://ir.lib.uwo.ca/context/etd/article/8531/viewcontent/auto_convert.pdf |
| Summary: | This thesis uses stable isotopes to investigate the adaptive advantages of Ovibos moschatus, a muskox, relative to now-extinct Pleistocene megafauna in eastern Beringia (Yukon Territory and Alaska), including another muskox Bootherium bombifrons. Ecological niches were defined for Ovibos and Bootherium using stable carbon and nitrogen isotope compositions of bone collagen. Plant remains trapped in modern Ovibos molars were used to determine the carbon and nitrogen isotope collagen-diet discrimination factors, which were then applied to ancient specimens. Ovibos possessed larger isotopic – and hence ecological – niches than Bootherium across eastern Beringian sites. The larger niche suggests that Ovibos consumed a wider range of forage than Bootherium – an advantage during the major vegetation change in eastern Beringia (and the Mammoth Steppe) during the terminal Pleistocene. Ecological niche size comparisons between Ovibos and other megafauna for the North Slope, Alaska also showed that species facing extinction tended to have small isotopic niches. During the post-Last Glacial Maximum, Ovibos also had a small isotopic niche size, but it increased in size by the Holocene, likely because of Ovibos’ advantageous digestive and feeding strategies relative to other genera that went extinct. Bioapatite oxygen isotope compositions for Ovibos and Bootherium from eastern Beringia were examined as proxies for drinking water isotopic composition – and hence warmer versus cooler conditions. Modern herbivores (Ovibos, Equus, Capra) were used to establish a baseline for assessing bioapatite oxygen isotope alteration in ancient specimens. The results confirmed that the oxygen isotope composition of bioapatite phosphate provides a more robust record of drinking water isotopic composition than structural carbonate. Bone collagen oxygen isotope compositions were also compared to those of bioapatite. In terms of oxygen-isotope preservation quality, collagen is poorer than phosphate but similar to bioapatite structural carbonate. ... |
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