PSU McNair Scholars Online Journal


Amphibians -- Eggs, Amphibians -- Habitat, Hylidae -- Reproduction, Predation -- Biology


An organism’s fitness is determined by its ability to produce viable offspring. For animals that lack post-hatching parental care, assessing and discriminating between oviposition sites may increase offspring survival. The Neotropical treefrog, Dendropsophus ebraccatus, is the only vertebrate known to be able to lay eggs both aquatically and terrestrially, and can do so in a given night. Laying eggs in water can increase hypoxia and aquatic predation, whereas desiccation and terrestrial predation increase with oviposition on land. Dendropsophus ebraccatus therefore provides a unique opportunity to measure adult reproductive choices in response to opposing costs associated with aquatic versus terrestrial reproduction. To test this, I 1) quantified aquatic predation risk in a natural setting, 2) tested whether D. ebraccatus demonstrates oviposition site discrimination in response to an aquatic egg predator, and 3) measured the relative importance of egg desiccation and aquatic predation risk on D. ebraccatus oviposition decisions. Aquatic egg predation risk is high in nature and the presence of an aquatic egg predator altered reproductive mode choices by D. ebraccatus. Not only did D. ebraccatus discriminate against pools with aquatic egg predators, but aquatic egg predation risk outweighed terrestrial egg desiccation risk, causing frogs to lay eggs out of water even in unshaded habitats where desiccation risk is high.

Faculty Mentor: Sarah Eppley



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