Date Thesis Awarded


Access Type

Honors Thesis -- Access Restricted On-Campus Only

Degree Name

Bachelors of Science (BS)




Rowan Lockwood

Committee Members

John Swaddle

Nicholas Balascio

Felisa Smith


The end-Pleistocene extinction resulted in a significant loss of North American mammalian fauna—including all species larger than 600 kg. Considerable research has focused on the large-bodied victims of this extinction, but to date, little is known about the impact on the surviving small mammal species.

Here, we characterize the influence of climate and biodiversity loss over the late Quaternary on the hispid pocket mouse (Chaetodipus hispidus) from Hall’s Cave, Texas. Specifically, using a well dated fossil record, we analyzed the changes in the population body size and diet of C. hispidus across the last 16,000 years. In total upwards of 400 specimens were examined with approximately 45 specimens (30 for body size and 15 for diet) from each of 12 time intervals, each representing ~1.3 ka. Body size was estimated from the lower tooth row length and diet was assessed using isotopic niche estimated from carbon (δ13C) and nitrogen (δ15N) isotopes of bone collagen from fossil mandibles. We found that average body mass decreased significantly across the pre- and post-extinction time interval as well as across individual time bins. Isotopic analysis revealed little to no change in δ13C values but a significant decrease in δ15N values. Decreasing body size was shown to be statistically significantly correlated with an increase in temperature and a decrease in precipitation and species richness. Diet appears to have no significant correlation with body size, with decreasing δ15N values possibly linked to a baseline shift in nitrogen within the ecosystem itself. These results suggest C. hispidus is strongly impacted by variations in climate with changes in community structure playing a secondary role; however, whether these relationships are direct or indirect remains unclear.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

On-Campus Access Only