A Multi-isotope Investigation of Mammoth Diet, Habitat, and Movement Patterns in the Central Great Plains, U.S.A.

Authors

Jacob McCloskey, University of Nebraska-LincolnFollow

First Advisor

Ross Secord

Committee Members

R. Matthew Joeckel, Sherilyn Fritz

Date of this Version

8-2025

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Earth and Atmospheric Sciences

Under the supervision of Professor Ross Secord

Lincoln, Nebraska, August 2025

Comments

Copyright 2025, Jacob McCloskey. Used by permission

Abstract

During the Last Glacial Maximum (LGM), the Great Plains in Nebraska consisted of wooded parklands and grasslands, whereas spruce (Picea) forests, parklands, and steppe grasslands dominated east of the Missouri River. I analyzed bulk carbon (δ¹³C), oxygen (δ¹⁸O), and strontium (⁸⁷Sr/⁸⁶Sr) isotopes from tooth enamel in isolated mammoth (Mammuthus) molars to compare diet and movement patterns in two late Pleistocene assemblages: one in Nebraska (n = 24), and one in western Iowa and Missouri (n = 17). Furthermore, I identified a morphometric subset of molars as belonging to either M. primigenius (woolly mammoth, n = 19) or M. columbi (Columbian mammoth, n = 12) for species-specific isotope comparisons. Carbon isotope data indicate that C₃ plants were primarily consumed, although eight mammoths in Nebraska yielded a mixed C₃/C₄ signal. I find no statistically significant differences in C₃ diet (δ¹³C < -8‰), δ¹⁸O, or ⁸⁷Sr/⁸⁶Sr between assemblages, or between species in either assemblage. Most identified mammoths that consumed C₄ vegetation were M. columbi, whereas M. primigenius fed almost exclusively on C₃ plants. Carbon and strontium isotopes in the Iowa and Missouri assemblage suggest six mammoths occupied areas several hundred kilometers northeast of southwest Iowa where they died, whereas all others in the assemblage show local values suggesting relatively small home ranges. Most individuals from Nebraska also possess ⁸⁷Sr/⁸⁶Sr values indistinguishable from modern plant values. However, one M. primigenius individual from southern Nebraska possesses anomalously high ⁸⁷Sr/⁸⁶Sr (0.71260), and low δ¹⁸O_VSMOW (15.23‰), suggesting a trek of over 500 km to the Rocky Mountains in Colorado or Wyoming, or the Black Hills in South Dakota. A ⁸⁷Sr/⁸⁶Sr value of 0.71155 in a tooth fragment collected in southwestern Nebraska also suggests some occupancy outside of the local area. Additionally, my strontium data indicate that, like modern elephants, most mammoths did not travel long distances, although some individuals did.

Advisor: Ross Secord