Date of Award
Master of Science (MS) in Biology
"The purpose of this research was to assess the predator-induced responses of a larval amphibian to its natural predators and to an unfamiliar fish. Amphibians express chemically-mediated antipredator defenses in behavior, morphology and life history, and are currently threatened with predation by invasive fish. To investigate this issue, we first initiated a behavioral assay to test the null hypotheses that predator type and diet have no effect on long-toed salamander (Ambystoma macrodactylum) behavior. We exposed individual replicate A. macrodactylum to chemical cues (kairomones) from garter snakes (Thamnophis elegans), tiger salamanders (A. tigrinum) and brook stickleback (Culaea inconstans), which had been fed a larvae-diet of A. macrodactylum or a null-diet of earthworms (Lumbricus terrestris), and measured subsequent changes in A. macrodactylum behavior. A. macrodactylum decreased activity in response to their native predators, and to a greater degree if the predators were fed A. macrodactylum. Larvae increased activity in response to null-diet fish, but decreased activity in response to larvae-diet fish, indicating the use of a diet cue to identify a potential threat. We then conducted a conditioning experiment to test the null hypothesis that repeated exposure to C. inconstans kairomones with larvae-diet cues would not affect A. macrodactylum behavior when later exposed to the predator kairomones alone. A. macrodactylum were repeatedly exposed to kairomones from larvae-diet C. inconstans and later tested for a response to null-diet C. inconstans. Conditioned A. macrodactylum decreased their activity in response to fish kairomones alone, indicating they were able to learn adaptively through the use of the diet cue. We believe this is the first example of diet-dependent learning in an amphibian-fish model. During the conditioning experiment, we also measured for change in morphology, growth and development towards metamorphosis, an important life history event, as indicators of other predator-induced plastic responses. While we did not detect a significant difference in morphology or growth, conditioned A. macrodactylum reached the final stage of metamorphosis at an accelerated rate. We suggest A. macrodactylum is able to use a diet cue for predator labelling and learning, and to make potentially beneficial adjustments to its life history"--Leaf iv.
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Reed, Renae K., "Chemically-mediated prey responses: invasive brook stickleback induced changes in behavior and life history of larval long-toed salamanders" (2016). EWU Masters Thesis Collection. 373.