Date Approved


Degree Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department or School


Committee Member

Katherine Greenwald, Ph.D.

Committee Member

Cara Shillington, Ph.D.

Committee Member

Margaret Hanes, Ph.D.


Amidst massive losses in biodiversity, it is vital to identify the factors driving species declines. The main objective of this research was to assess dietary differences between Storeria dekayi and Thamnophis sirtalis and their less abundant and more geographically restricted sister species, Storeria occipitomaculata and Thamnophis butleri, in Illinois and Michigan. I hypothesized that greater abundance and more cosmopolitan distribution are associated with consuming a wide variety of prey and more nonnative prey. To assess diets, I conducted field surveys of Storeria and Thamnophis and analyzed DNA metabarcoding data from fecal samples. I found no significant difference in the dietary diversity or proportion of nonnative prey in the diets of Storeria or Thamnophis. The diet of S. occipitomaculata was dominated by Deroceras laeve (native), whereas T. butleri specialized on Lumbricus rubellus (nonnative). In order to protect rare snake species from decline, we must preserve important predator and prey habitats.