Impact of Microhabitat Selection on Burrow Distribution of Nine-Banded Armadillos and Gopher Tortoises in a Pine Plantation

Nine-banded armadillos and gopher tortoises cohabit pine forests in the southeastern United States but may compete for burrowing locations. This may be problematic because gopher tortoises are a declining species. To examine coexistence, a microhabitat selection study was carried out at Moody Air Force Base near Valdosta, Georgia. In addition, preference of habitat parameters was compared between burrow categories, such as armadillo burrow types based on location and gopher tortoise burrow types based on age of occupant. Eighty-six burrows were randomly selected and a discriminant analyses was used to identify parameters that differentiate the locations of both species’ burrows from each other and from random sites (N = 250). Armadillo burrows (N = 40) were found in areas with higher vegetation density, greater canopy cover, steeper slopes and thicker ground cover than gopher tortoise burrows (N = 46). Steeper slopes, low visibility and farther distance from edges separated armadillo burrows from random sites. Armadillo prefer to build burrows on berms that have steeper slopes, higher vegetation density, higher ground cover, less sunlight and lower elevation than off berm burrows. In addition to the microhabitat study, I determined the detectability of different types of burrows by comparing burrow surveys conducted prior to and after a prescribed burn. Gopher tortoise juvenile and hatchling burrows and those of armadillos off berm had low detectability during the pre-burn survey. Adult gopher tortoise burrows had higher visibility than other burrow categories. This is the first study to provide evidence that synoptic armadillos and gopher tortoises prefer to build burrows in different microhabitats. This spatial niche partitioning was probably related to their physiology. Competition may be occurring because of the presence of coopted burrows and might suggest a complex or mixed mechanism to explain coexistence. Keyword 1: Nine-banded armadillos Keyword 2: Gopher tortoise Keyword 3: burrows Keyword 4: microhabitatChapter I: INTRODUCTION 1 -- Chapter II: LITERATURE REVIEW 7 -- Microhabitat selection and coexistence theories 7 -- Burrowing ecology 11 -- Life history of nine-banded armadillos 14 -- Life history of gopher tortoises 18 -- Interactions between armadillos and gopher tortoises 23 -- Chapter III: MATERIALS AND METHODS 25 -- Study area 25 -- Burrows 26 -- Activity status 27 -- Microhabitat selection 28 -- Detectability of burrows 33 -- Data analysis 33 -- Chapter IV: RESULTS 41 -- General burrow information 41 -- Armadillo burrows 41 -- Gopher tortoise burrows 42 -- Burrow activity 43 -- Compass orientation 44 -- Placement of armadillo and gopher tortoise burrows 44 -- Comparison of random sites with burrows sites 45 -- Burrow support structures 45 -- Influence of habitat parameters on the placement of different age classes of gopher tortoise burrows 46 -- Influence of habitat parameters on the placement of armadillo burrows on -- and off berms 47 -- Effect of fire on burrow visibility 48 -- Temperature modulation 49 -- Detectability of burrows 49 -- Chapter V: DISCUSSION 73 -- Placement of armadillo and gopher tortoise burrows 73 -- Comparison of placement of age class of gopher tortoise burrows 81 -- Comparison of placement of armadillo burrows on and off berm 81 -- Burrow morphometrics 82 -- Compass orientation 83 -- Detectability of burrows 85 -- Conclusions 87 -- REFERENCES 91 -- APPENDIX A: Compass orientation for armadillo and gopher tortoise burrows -- chosen randomly in the study site at Moody Air Force Base 120.McDonough, Colleen M.Anderson, CoreyLockhart, J. MitchellSmith, LoraCruz, Becky K. daM.S.Biolog