Date of Award

2024

Degree Name

Biological Sciences

College

College of Science

Type of Degree

M.S.

Document Type

Thesis

First Advisor

Dr. Jayme Waldron, Chairperson

Second Advisor

Dr. Shane Welch

Third Advisor

Dr. Kyle Palmquist

Abstract

Amphibians are declining globally, with many declines associated with habitat loss. The longleaf pine (Pinus palustris) ecosystem historically covered most of the southeastern United States and supports a host of endemic amphibians. This ecosystem has declined by over 97% in the last two hundred years and many associated species have declined with it. The Little Grass Frog (Pseudacris ocularis) is a longleaf pine endemic anuran that has been understudied and under-surveyed; almost no information is known on the ecology of this species and no population studies have been conducted. My goals were to create an acoustic recognizer to detect Little Grass Frog calls, better understand the calling phenology of the species, and examine how historical land use and contemporary vegetation structure influence its occupancy. I used ARUs to collect anuran chorus data from wetlands in the South Carolina Coastal Plain. I conducted vegetation surveys in study wetland basins and terrestrial buffers to quantify the contemporary vegetation structure of each. I used historical aerial imagery and ground-truthing to establish historical land use occupancy covariates. In Chapter 1, I used two automated signal detection software to create three acoustic recognizers and their efficacy in detecting LGF calls. I used the best-performing recognizer, made in Raven Pro, to analyze acoustic data from 13 wetlands. I used LGF call detections from the recognizer output to establish occupancy in a single-season occupancy modeling framework. I used human-annotated test data to compare each recognizer's accuracy, precision, and recall. The top-performing recognizer was applied to data collected with autonomous recording units to establish occupancy for Chapter 2. In Chapter 2, I used LGF call detections and single-season occupancy models to evaluate what factors influenced the detection probability and occupancy of Little Grass Frogs in the southern coastal plain of South Carolina. I created a recognizer in Raven Pro 1.6.4 (Cornell Lab of Ornithology, Ithica, N.Y.) that had high precision and was applied to audio files collected across 13 wetlands to establish occupancy. Calling detection was significantly higher when mean daily temperatures were higher, though the Little Grass Frog called throughout the year. Occupancy was associated with the prevalence of fire-dependent species in wetland buffer basal areas, suggesting that the LGF is sensitive to habitat disturbances in wetland buffers. These results confirm that Little Grass Frogs select terrestrial habitats similarly to other longleaf pine endemic species and should be managed similarly. Additionally, the results of this study indicate that the Little Grass Frog may be at higher risk of decline than previously expected, given their reliance on the longleaf pine ecosystem structure and warm breeding conditions in rainfed pools that will be impacted by increasing droughts in the face of climate change.

Subject(s)

Biology.

Ecosystem.

Longleaf pine.

Frogs.

Ecology.

Amphibians -- Population.

Wildlife management.

Wildlife conservation.

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