Graduation Year

2021

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Biology (Integrative Biology)

Major Professor

Jeremiah Sean Doody, Ph.D.

Committee Member

Deby Cassill, Ph.D.

Committee Member

Jeffrey Goessling, Ph.D.

Committee Member

George Heinrich, Ph.D.

Keywords

behavioral adaptation, gap light analysis, hemispherical photography, tortoise burrow

Abstract

Climate warming is expected to continue in coming decades, posing a threat to species worldwide. While some species may be able to shift their ranges in the pursuit of cooler temperatures, a large portion of species may have to find ways to adapt to warmer conditions in situ. Oviparous reptiles may be able to buffer against rising temperatures by altering nest site choice. In this study, I quantified nest site choice and its thermal consequences in a population of the gopher tortoise (Gopherus polyphemus) in southwestern Florida. I found marked variation in the openness of selected nest sites, and at these sites, mean canopy openness was 20.0%, which fell between the mean openness values of potential nest sites in sunnier (61.1%) and shadier locations (14.5%). Canopy openness, incident radiation intensity, and mean nest temperatures were all significantly, positively correlated, demonstrating a direct thermal consequence of nest site choice. Furthermore, this study suggests that females are adequately able to predict incubation conditions at the time of oviposition because canopy openness and incident radiation intensity decreased by negligible amounts over the course of incubation. To my knowledge, this study is the first to quantify the behavior of females of G. polyphemus constructing nests inside their burrows. By nesting 1.5 m inside the burrow or in shadier locations outside the burrow, females could lower mean nest temperature by ~2.5°C or ~3°C respectively to buffer developing embryos against climate warming.

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