Comparison of Gopher Tortoise and Nine-Banded Armadillo Associate Fauna

Burrowing organisms are ecosystem engineers that augment the availability of resources for other species. Throughout the Coastal Plain of the southeastern United States the gopher tortoise (Gopherus polyphemus) is a keystone species in open canopy pine-forest ecosystems as its burrows are utilized by over 360 species. These species are responsible for numerous ecosystem processes that maintain ecosystem functionality and health. Across its current range, the gopher tortoise is in decline and has been listed as a vulnerable species by the International Union for the Conservation of Nature (IUCN). Declining tortoise abundance negatively impacts the populations of species that depend on tortoise burrows which will, in turn, have negative impacts on ecosystem function. The introduced nine-banded armadillo (Dasypus novemcinctus) is another burrowing species of similar size that is highly abundant and syntopically distributed with the gopher tortoise. Recent research has found high diversity of vertebrates utilizing armadillo burrows, implicating that armadillos support local biodiversity in a similar manner as gopher tortoises. I compared vertebrate visitation between armadillo and tortoise burrows in a mixed-pine hardwood forest at the Lake Louise Field Station in Lowndes County, Georgia using motion activated game cameras placed at equal numbers of burrows produced by each excavator species. I also tested for burrow and microhabitat effects on visitation by associate vertebrates and investigated patterns of metacommunity nestedness within the study area. A total of 40 vertebrate taxa were observed visiting burrows between October 2019 and December 2020. Species richness, biodiversity, and community composition were not significantly different between burrow types. However, total visitation was significantly greater at tortoise burrows as well as visitation frequency for 15 taxa. Burrow and microhabitat variables showed varying effects on burrow visitation for different categories of vertebrates. Most notably, vertebrate visitation frequency was positively affected by tortoise burrows, active burrows, and increased tree species richness while consistently negative effects were observed for increased canopy cover and high proportions of hardwood trees. Patterns of nestedness were not found to correspond with any applicable environmental variable. This research provides a unique framework for comparing utilization of habitat features, adds information to the growing body of work on the ecological effects of the nine-banded armadillo’s range expansion, and pinpoints aspects of the habitat that relate to the importance of burrows for other species. My study also highlights and reinforces the ecological significance of the gopher tortoise and suggests that armadillo control efforts may need to be considered on a case-by-case basis.Introduction 1 -- Study Objectives 5 -- Hypotheses 9 -- METHODS 12 -- Study Site 12 -- Survey 13 -- Camera Trap Configuration 15 -- Sampling 16 -- Environmental Data 19 -- Statistical Analysis 22 -- Differences in Commensal Visitation Between Burrow Types 23 -- Community Dissimilarity 24 -- Environmental Characteristics’ Influence on Commensal Visitation 25 -- Meta-Community Nestedness 26 -- RESULTS 28 -- Survey Data 28 -- Camera Trap Data 29 -- Multiple Individuals 31 -- Comparison of Species Richness, Diversity, and Visitation Frequency 32 -- Mean Comparisons 32 -- Comparisons of Burrow Visitation Frequency 32 -- Community Dissimilarity 34 -- Environmental Factors’ Effects on Commensal Visitation 35 -- Meta-Community Nestedness 39 -- DISCUSSION 40 -- Conclusion 48 -- Literature Cited 50Anderson, CoreyMcDonough, Colleen M.Lockhart, Jack MitchellM.S.Biolog