Undergraduate Honors Thesis Projects

Date of Award

Spring 4-28-2024

Document Type

Honors Paper

Degree Name

Zoo and Conservation Science-BS


Biology & Earth Science


Dr. Sarah Bouchard

First Committee Member

Dr. Sarah Bouchard

Second Committee Member

Dr. Kevin Svitana

Third Committee Member

Dr. Ashley Simons


Road salt, Salinization, Gray treefrog, Morphology, Predation response

Subject Categories

Biology | Higher Education | Zoology


The extensive use of road salt has increased the salinity of aquatic ecosystems, leading to negative impacts across trophic levels and potential interactions with other biotic stressors. Predation threat can alter tail morphology, slow larval growth, and accelerate metamorphosis in gray treefrogs (Hyla versicolor). The present study aimed to examine the effects of road salt on H. versicolor growth and development and explore potential impacts on plastic predation responses. Larvae were reared in 30 outdoor mesocosms under no-salt-added (110 mg Cl-/L), low (230 mg Cl-/L), and high (1,000 mg Cl-/L) chloride concentrations, with and without a dragonfly larvae (Pachydiplax longipennis) predator. Caged predators were fed five H. versicolor tadpoles daily to induce kairomone production and generate antipredation responses. Salinity and predation facilitated developmental and morphological changes in H. versicolor larvae and induced interactive effects on tail morphology. Salinity induced greater larval growth rates and increases in tail and organ size. Predation did not affect larval growth or any measures of tail morphology, but also increased organ size. While both stressors decreased time to metamorphosis, they produced opposing results, with higher salinity inducing larger froglets and predation inducing smaller froglets. Interactive effects on tail morphology were found, indicating that plastic predation responses were altered at high salt concentrations. This study has important implications for how increases in environmental salinity levels will affect H. versicolor as morphological and developmental changes in larvae can have greater impacts on fitness post-metamorphosis in the terrestrial environment.

Licensing Permission

Copyright, all rights reserved. Fair Use

Acknowledgement 1


Acknowledgement 2


Available for download on Sunday, April 23, 2028