Graduate Program

Biological Sciences

Degree Name

Master of Science (MS)

Semester of Degree Completion

2013

Thesis Director

Stephen J. Mullin

Thesis Committee Member

Robert E. Colombo

Thesis Committee Member

Scott J. Meiners

Abstract

The trophic niche width of a species varies depending on the foraging strategy employed by the individuals within a population. Among reptiles, the niche breadth of many species of snakes is relatively understudied. Within this clade, the genus Coluber includes wide-ranging, actively foraging snakes that have been historically labeled as dietary generalists. The dietary information on Blue Racers (Coluber constrictor foxii) is limited, and little is known about ontogenetic or seasonal differences in the prey species consumed. Additionally, this information is available from gut and fecal content only. In addition to obtaining gut and fecal contents, I employed stable isotope analyses using δ13C and δ15N to describe the dietary niche breadth of C. constrictor foxii. I performed x2 analyses to investigate patterns in morphometric data and multiple-way ANOVA to investigate differences in the isotope signatures of individual snakes between seasons, tissue types, sexes, and size classes. I used a Bayesian mixing model to determine the potential sources of δ13C and δ15N in the snake tissues. This population of C. constrictor foxii showed differences in standard morphometric data between age classes but not sexes. At the population level, C. constrictor foxii appears to follow a dietary pattern typical of an opportunistic predator. Variation exists among age classes, however, with depleted values of δ15N for large juveniles, indicating that they occupy a dietary niche unique from either hatchlings or adults. Although it appears that certain prey items are incorporated with greater frequency into the diet of this population of C. c. foxii, these snakes are likely practicing an opportunistic foraging strategy.

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