δ 13C, δ18O, and 87Sr/86Sr Values Provide Insights Into the Behavioral Patterns of a Mammuthus jeffersonii During the Bølling-Allerød Interstadial Period

• Main Author: Spendlove, Ian Brent
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2024
• Subjects: Genetics; Geology; Paleontology
• ISBN: 9798383681701

Only two Jeffersonian mammoths (Mammuthus jeffersonii) have been proposed in the western United States. The Coplen Springs mammoth was proposed based on tooth morphology (Nisbet, 2014), and UISSM-001-COLA, discovered in Conda, ID, was proposed based on mtDNA analysis (Morrison et al., 2024). This study focuses on the M. jeffersonii specimen excavated in 1966 in Conda, ID. The mammoth was radiocarbon dated to 13,500 cal yr BP (Morrison et al., 2024), during the Bølling–Allerød Interstadial Period, a time of intense climatic warming and environmental change. While research shows that midwestern United States Jeffersonian mammoths were ranging in mesic environments and consumed C4 grasses and shrubs (Saunders et al., 2010), little is known about the dietary patterns of Jeffersonian mammoths in the western US. This study utilizes δ13C and δ18O isotope ratios from molar enamel to determine the diet and compares 87Sr/86Sr ratios from the molar enamel to those that occur in surface water from the region to determine migration patterns.Using known growth rates of Columbian mammoth (Mammuthus columbi) molars, the tooth was sampled at 1.5 cm intervals to create a 13-year timeline of δ 13C, δ 18O, and 87Sr/86Sr values. Each of the 13 samples represents a yearly average. The 87Sr/86Sr enamel ratios had an average value of 0.709171, which is similar to surface water Sr isotope ratios from the region, indicating the mammoth was likely native to the area and not migrating great distances. δ 13C (VPDB) values of the molar enamel varied from -7.7‰ to -10.2‰, indicating that the mammoth was consuming a diet that was primarily dominated by C3 vegetation. The youngest geologic sample showed that the mammoth consumed a diet with 36.46% C4 vegetation, while the oldest sample is only 18.04%. The increase in the percent of C4 contribution was likely due to the mammoth migrating to an area with less grasses and more C4 shrubs and sedges. The δ 18O (VSMOW) carbonate values ranged from 16.4‰ to 19.6‰. After calibrating the oxygen carbonate enamel values to drinking water (δ 18ODW), δ18ODW values varied between -13.7‰ and -18.2‰. The variability of δ 18ODW values was within the observed variability of other mammoths from the Midwestern United States and is likely due to the mammoth consuming water from variable water sources within the region it was ranging.