Larval and post-metamorphic ecology of the dusky gopher frog (Rana sevosa)
- WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
- Christien Myles Lance (Creator)
- Institution
- Western Carolina University (WCU )
- Web Site: http://library.wcu.edu/
- Advisor
- Joseph Pechmann
Abstract: Amphibians are declining worldwide, and research on their habitats and ecology are critical to their continued conservation. I conducted two experiments with the federally endangered dusky gopher frog, Rana sevosa. The dusky gopher frog breeds exclusively in isolated, open canopy wetlands, usually with extensive herbaceous growth. It is known that larvae of the dusky gopher frog, and of many other anurans, have higher growth and survival under open canopy than under closed canopy conditions. The mechanisms whereby this occurs are poorly understood, however. In the first study, I conducted a complete factorial experiment in mesocosms to compare the relative influence of factors differing between open and closed canopy ponds. A heat/light treatment consisted of one third of tanks being exposed to full sunlight, one third of tanks being shaded with 70% shadecloth, and the final third being shaded with 70% shadecloth but heated to mimic the temperature of the full sun tanks. In addition, tanks received either a closed canopy tree leaf litter mixture or an open canopy herbaceous vegetation mixture, and vertical vegetation-like structure made of polypropylene rope or not. Cool shaded tanks and heated shaded tanks had identical survival to metamorphosis at 74.7% and produced frogs with an average mass of 2.21 g and 2.09 g respectively, while tanks in full sunlight achieved significantly higher 93.4% survival to metamorphosis and 2.64 g mass. The open canopy vegetation mixture yielded an average tank survival of 88.3% and mass of 2.94 g, compared to closed canopy vegetation tanks with a significantly lower survival of 73.5% and mass of 1.61 g. Structure had no effect on survival or mass. These results indicate that sunlight (not heat alone) and herbaceous plants are important in increasing dusky gopher frog survival and mass in open canopy conditions, with implications for captive-rearing and habitat restoration. Dusky gopher frog tadpoles are raised in captivity to increase survival and released back into the wild at metamorphosis to augment wild populations (headstarting) and start new populations (translocation). In the second study, I used radiotelemetry to compare post-metamorphic migratory movements and behavior between tank-reared juveniles and juveniles leaving the pond naturally. Frogs were tracked daily, until the signal was lost, the frog shed the transmitter, or the frog was predated, with a range of 1 to 73 days of tracking. Two of twenty frogs successfully found a permanent refugium, at an average distance of 153 meters from the center of the pond basin. No differences in movements or fates were found between groups; however, natural individuals did utilize grass as cover during migration more often than tank-reared frogs. This suggests that current headstarting protocols produce juveniles that differ only minorly from natural juveniles in movement and ecology, and that headstarting is likely to effectively replicate natural recruitment.
Larval and post-metamorphic ecology of the dusky gopher frog (Rana sevosa)
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Created on 4/1/2022
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Additional Information
- Publication
- Thesis
- Language: English
- Date: 2022
- Subjects
- Frogs
- Larvae -- Ecology
- Endangered species