Date Approved

4-2021

Graduate Degree Type

Thesis

Degree Name

Biology (M.S.)

Degree Program

Biology

First Advisor

Jennifer Moore

Second Advisor

Amy Russell

Third Advisor

Charlyn Partridge

Academic Year

2020/2021

Abstract

Characterizing the diet of imperiled species using minimally invasive methods is crucial to understanding their conservation requirements. DNA metabarcoding methods have been used to characterize the diet primarily in mammalian systems, while reptiles are heavily underrepresented in this literature. Here, we apply a DNA metabarcoding approach to study the diet of the eastern massasauga rattlesnake (Sistrurus catenatus); a Federally Threatened snake found throughout the Great Lakes Region. Eighty-three fecal samples collected across 10 different massasauga populations located in Michigan were sequenced. We use universal metazoan primers and develop a host-specific oligonucleotide blocker to uncover the full potential diet of the eastern massasauga. We identified at least 18 prey items. Non-target taxa and taxa from potential secondary consumption were also identified in fecal samples. Eastern massasaugas exhibited a strong preference towards small mammals, with meadow voles (Microtus pennsylvanicus) being the most common (69.4% of diet), along with occasional bird and snake prey. We did not find that younger snakes preferred other snake prey, but instead consumed smaller mammals such as masked shrews (Sorex cinereus) and northern short-tailed shrews (Blarina brevicauda). Adult individuals exhibited a more generalized diet, consuming a wider range of prey taxa, and appear to be opportunistic predators. We conclude that small mammals are a crucial part of eastern massasaugas diet and recommended this be taken into consideration when conservation strategies are developed. Additionally, we tested the efficiency of sample preservation methods with the fecal samples and suggest freezing samples as soon as possible following collection to prevent further degradation of DNA. This study is one of few to apply metabarcoding methods to study snake diet, and the first to study rattlesnake diet. We have demonstrated that DNA metabarcoding is a reliable, accurate approach to obtain quality dietary information from snake fecal samples. As reptiles are currently facing global declines, the methods developed in this study can be applied to other reptile species, providing a way to study the diet of at-risk species minimally invasively.

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