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Susanna Sousa, MS, is a 2024 graduate of the MS Program in Environmental Studies at Antioch University New England

Thesis Committee:

  • Michael Akresh, PhD, Chairperson
  • Jeffrey Larkin, PhD, Committee Member
  • Lisabeth Willey, PhD, Committee Member

Keywords

eastern gray treefrog, Cope’s gray treefrog, spatial scales, landscape, forest management, autonomous recording unit, ARU, detection, occupancy

Document Type

Thesis

Publication Date

2024

Abstract

Understanding the characteristics that influence amphibian occupancy within forest ecosystems is necessary for effective conservation and management. My study focused on how eastern gray treefrog (Hyla versicolor) occupancy is influenced by environmental attributes quantified at various spatial extents. From May through July 2020 and 2021, we deployed autonomous recording units at 986 unique locations within managed forests in Pennsylvania and Virginia. Landcover class and road density were evaluated around each sampling location at ten spatial extents between 60 and 4000 m. Additionally, I measured aspect, elevation, soil drainage class, distance to nearest wetland, and basal area at each sampling location. Using a machine learning classifier, I detected eastern gray treefrogs at 110 out of 875 locations (12.6%). I created single-season occupancy models and performed model selection based on Akaike’s Information Criterion. Daily detection probability increased with average daily temperature, percent humidity, and days since precipitation, and decreased with lunar illumination. Eastern gray treefrog occupancy probability increased as distance to seasonally flooded wetlands decreased and the amount of agriculture within 750 m increased. In Pennsylvania, probability of occupancy increased with forest management practices such as clear cutting, partial cutting, and prescribed burning. Thus, eastern gray treefrog populations do not appear to be negatively affected by forest management. My results suggest that this species is more likely to be found in heterogeneous landscapes and demonstrate the importance of considering landscape variables at multiple spatial scales when making conservation and management decisions. This thesis is available in open access at AURA (https://aura.antioch.edu).

Comments

ORCID No.: 0009-0002-5194-4370

Publications and Presentations

Sousa, S. G., Willey, L. L., Kitzes, J., Larkin, J. L., Fiss, C. J., Cohen, E. B., Syunkova, A., Parker, H. A., Larkin, J. T., Akresh, M. E. (2024, July 28 - 30). Influence of Landscape Characteristics on Eastern Gray Treefrog (Hyla versicolor) Occupancy in Managed Forests of Pennsylvania and Virginia [Conference presentation]. Northeast Partners in Amphibian and Reptile Conservation (NEPARC) Annual Meeting, Winter Harbor, ME, United States.

Sousa, S. G., Willey, L. L., Kitzes, J., Larkin, J. L., Fiss, C. J., Cohen, E. B., Syunkova, A., Parker, H. A., Larkin, J. T., Akresh, M. E. (2024, April 19 - 21). Influence of Landscape Characteristics on Eastern Gray Treefrog (Hyla versicolor) Occupancy in Managed Forests of Pennsylvania and Virginia [Conference presentation]. Northeast Natural History Conference (NENHC), Albany, NY, United States.

Sousa, S. G., Willey, L. L., Kitzes, J., Larkin, J. L., Fiss, C. J., Cohen, E. B., Syunkova, A., Parker, H. A., Larkin, J. T., Akresh, M. E. (2023, April 30 - May 2). Occupancy of eastern gray treefrogs (Hyla versicolor) in relation to landscape characteristics in managed forests in Pennsylvania and Virginia [Poster session]. Northeast Association of Fish and Wildlife Agencies (NEAFWA), Hershey, PA, United States.

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