Seasonal Habitat and Shelter Selection by Reintroduced Eastern Indigo Snakes in 
Conecuh National Forest, Alabama 
 
by 
 
Sierra Hulsey Stiles 
 
 
 
 
A thesis submitted to the Graduate Faculty of 
Auburn University 
in partial fulfillment of the 
requirements for the Degree of 
Master of Science 
 
Auburn, Alabama 
December 14, 2013 
 
 
 
 
Keywords: Eastern Indigo Snake, Drymarchon couperi, reintroduction, habitat selection, 
shelter  
 
 
Copyright 2013 by Sierra Hulsey Stiles 
 
 
Approved by 
 
Craig Guyer, Chair, Professor of Biology 
Robert Boyd, Professor of Biology 
Michael Wooten, Professor of Biology 
Sharon Hermann, Assistant Professor of Biology 
Christopher Jenkins, Adjunct Professor of Biology 
 
 
 
 
ii 
 
 
 
 
 
 
Abstract 
 
 
 Understanding how reintroduced snakes select habitats is crucial to the success of 
reintroduction projects. This study examines habitat selection by a federally threatened 
snake species in the southeastern United States following its reintroduction to Alabama.  
 In Chapter 1, I introduce my study organism, the Eastern Indigo Snake 
(Drymarchon couperi), illustrating the reasons it was listed as a threatened species. I 
outline the factors that led to the species? extirpation and a current reintroduction project 
in Alabama. I describe the habitats documented in studies of wild indigo snakes and 
explain why it is important to study habitats selected by reintroduced animals. 
Chapter 2 describes the study of habitat selection by reintroduced indigo snakes. 
Habitat selection is examined at multiple spatial and temporal scales. Landscape, home 
range and shelter scales are investigated for habitat selection, as well as seasonal 
examinations at the home range and shelter scales. The results of habitat selection by 
reintroduced snakes in this study are compared to the results from a previous study of 
habitat selection in a wild population of indigo snakes in Georgia near the source sites of 
animals in this reintroduction. The results of habitat selection in this study are discussed 
in the context of hierarchical habitat selection. Strategies for managing habitat for indigo 
snakes are recommended based on the results of this study.  
Chapter 3 summarizes the key results of this study and highlights their importance 
and application to future indigo snake reintroductions.  My results demonstrate that 
 iii 
reintroduced snakes selected habitats in a manner mimicking habitat selection in naturally 
distributed populations. I conclude that management practices that create and maintain 
open-canopied habitats supporting gopher tortoises will be essential for the successful 
reestablishment of indigo snakes in the northern portion of their range.   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 iv 
 
 
Acknowledgments 
 
 
 This work would not have been possible without my husband Jimmy who has 
lovingly supported me in every way on my journey through this life and has given every 
part of it meaning for me. I love you from the depths of my soul. I thank my beloved late 
brother, Shane Harper Hulsey, who always believed I was smarter than I am and whose 
pride in me has always made me want to work harder. You are always with me, Shane. I 
thank my parents, Donald and Billie Sue Hulsey; my sister, Ashley Hulsey-Coutch; my 
parents-in-law, Robert and Linda Stiles; and my friends for supporting me through the 
good times and bad. With sincere gratitude, I thank Craig Guyer, who has been a true 
mentor to me for many years now. Without him, I would not be the scientist or person 
that I am today. I am also grateful to the Guyer Lab, past and present, especially Sean 
Graham, David Steen, David Laurencio, Christina Romagosa, Jennifer Deitloff, Valerie 
Johnson, Ashley Rall, Mike Wines, Scott Goetz, Melissa Miller, Chris Murray, Brian 
Folt, Jeff Goesling and Diane Alix. Jim Godwin, Mark Bailey and Sharon Hermann 
offered me much wisdom along the way. Robert Boyd, students from the Auburn Society 
for Conservation Biology, the Field Herp Forum and a number of volunteers helped out 
on numerous work days on the forest. I also thank the Conecuh National Forest staff, 
especially Mark Garner, Ronda Mullins and Tim Mersmann for all their hard work. I also 
thank all the partners who made this research possible, Chris Jenkins with The Orianne 
Society, Mark Sasser with the Alabama Department of Conservation and Natural 
Resources, the Georgia Department of Natural Resources, Conecuh National Forest, US 
Fish and Wildlife Service and Zoo Atlanta.  
 v 
 
 
 
 
 
 
 
Table of Contents 
 
 
Abstract .......................................................................................................................... ii 
Acknowledgments .......................................................................................................... iv  
List of Tables.................................................................................................................. vi  
List of Figures ...............................................................................................................vii 
Chapter 1. Introduction   .................................................................................................. 1 
Chapter 2. Seasonal Habitat and Shelter Selection by Reintroduced Eastern Indigo Snakes 
in   Conecuh National Forest, Alabama   .............................................................. 5 
 
 Abstract   ............................................................................................................. 5 
 Introduction   ....................................................................................................... 6 
 Methods   ............................................................................................................. 9 
 Results   ............................................................................................................. 17 
 Discussion   ........................................................................................................ 19 
 References   ....................................................................................................... 27 
Chapter 3. Conclusions   ................................................................................................ 47 
Cumulative Bibliography   ............................................................................................. 49 
 
 
 
 
 
 vi 
 
 
 
 
 
 
 
List of Tables 
 
 
Table 1. Ranking matrix of landscape-scale habitat use versus availability .................... 36 
Table 2. Ranking matrix of non-seasonal home range-scale habitat use versus   
availability ......................................................................................................... 34 
Table 3. Ranking matrix of non-winter home range-scale habitat use versus availability 
 .......................................................................................................................... 38 
Table 4. Ranking matrix of winter home range-scale habitat use versus availability ....... 39 
Table 5. Ranking matrix of non-winter shelter use versus availability ............................ 40 
Table 6. Ranking matrix of winter shelter use versus availability  .................................. 41 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 vii 
 
 
 
 
 
 
 
List of Figures 
 
 
Figure 1. Differences in proportional use and availability of habitats at home range and 
landscape scales in 2010-2012, Alabama ............................................................ 42 
 
Figure 2.4. Differences in proportional use and availability of habitats for Eastern Indigo 
Snakes in 2003-2004, Georgia (Hyslop 2007)  ................................................... 43 
 
Figure 3.1. Comparison of landscape-scale mean availability and use of habitats for 
Hyslop 2003-2004 and Stiles 2010-2012   .......................................................... 44 
 
Figure 3. Underground shelter use by Drymarchon couperi radiotracked 2002-2004, 
Georgia (Hyslop et al. 2009)  ............................................................................. 45 
 
Figure 4. Mean proportion of shelter use and availability by Drymarchon couperi in 
winter and non-winter seasons, Conecuh National Forest, Alabama ................... 46 
 
 
 
 
 
 
 
 
1 
 
Chapter 1 
 
Introduction 
 
With reptile populations declining around the globe (Gibbons et al. 2000), 
reintroduction of extirpated species is gaining popularity as a conservation method 
(Germano and Bishop 2009). Research that indicates habitat requirements and responses 
to management regimes is needed to direct science-based recovery plans for declining 
species (Van Lear et al. 2005) because maintenance of high quality habitat is crucial for 
conserving these species. This is particularly true for reptile and amphibian reintroduction 
projects because poor habitat quality at release sites is one of the most frequently reported 
reasons for failure in amphibian projects and is understudied in reptile projects (Germano 
and Bishop 2009).  
In the southeastern United States, many imperiled reptile species are intimately 
associated with fire-maintained longleaf pine forests in the Coastal Plain (Guyer and 
Bailey 1993; Bailey 2004). The longleaf pine ecosystem is now thought to be one of the 
most imperiled ecosystems in the world (Noss and Peters 1995), with less than 3% 
remaining in longleaf pine (Frost 1993) and less than 0.002% remaining in old growth 
(Simberloff 1993). Throughout the current range of longleaf pine, at least 36 vertebrate 
species adapted to longleaf pine forests are of conservation concern (Means 2006), 
including the Eastern Indigo Snake (Drymarchon couperi).  
Historically, Eastern Indigo Snakes ranged across the Coastal Plain from Florida 
and southeastern Georgia through southern Alabama and into Mississippi (Conant and 
Collins 1998). This range encompasses much of the 14,000,000 ha historical range of 
 2 
longleaf pine (Pinus palustris) in the southeastern United States. As a species closely tied 
to longleaf pine in the northern portion of its range, the indigo snake has also experienced 
range-wide declines. In 1978, indigo snakes were listed as Threatened under the federal 
Endangered Species Act (United States Fish and Wildlife Service 1978). Wild 
populations of indigo snakes are currently known only from southeastern Georgia and 
Florida (Diemer and Speake 1983; Moler 1985). 
A reintroduction effort to reestablish viable populations of the indigo snake is 
currently under way within the Conecuh National Forest (CNF) in Alabama, where 
indigo snakes have been extirpated, with the last confirmed free-ranging snake being 
observed near the CNF by Neill (1954). The major causes of extirpation are thought to be 
increased mortality due to gassing of gopher tortoise burrows used by indigo snakes 
(Speake and Mount 1973) and reduced habitat quality. Return to a natural fire frequency 
has been recommended for increasing habitat quality for indigo snakes (Gunzberger and 
Aresco 2007) and fire management on the CNF over the  past 20 years has transformed 
significant portions of this forest to the open aspect of the ancestral landscape required by 
indigo snakes (Guyer et al. 2007). Additionally, new state regulations outlawing gassing 
of gopher tortoise burrows and reduced evidence of human predation of tortoises in the 
CNF indicate increased suitability for indigo snake survival. 
Source populations for the reintroduction project are located in areas of southern 
Georgia that contain the largest viable populations of the species in the northern portion 
of its range (Diemer and Speake 1983; Moler 1985). Free-ranging individuals in southern 
Georgia use large home ranges that contain multiple habitats, including xeric uplands and 
wet lowlands that are used by indigo snakes each year (Hyslop 2007).  The presence of 
 3 
gopher tortoises is a particularly important habitat component for indigo snakes (Diemer 
and Speake 1983; Lawler 1977) because these snakes overwinter in gopher tortoise 
burrows (Diemer and Speake 1981; 1983), often returning to the same burrows in 
different years (Stevenson et al. 2003). Gopher tortoise burrows are also used by indigo 
snakes for nesting, foraging, and as refuges prior to ecdysis (Landers and Speake 1980; 
Smith 1987).  
Snakes are known to demonstrate variation in which habitats they select as well as 
the scales at which they select habitats. Geographic differences in habitat use between 
indigo snakes in the northern and southern portions of its current range have been 
documented (Lawler 1977; Speake et al. 1978; Steiner et al. 1983; Moler 1992; Hyslop 
2007).  Many studies of habitat selection in snakes have demonstrated the need to 
examine habitat selection at multiple scales (e.g., Moore and Gillingham 2006; Steen et 
al. 2010; Hoss et al. 2010). This underscores the importance of documenting which 
habitats are selected by reintroduced snakes as well as the scale of habitat selection 
exhibited at release sites.  
Studies examining habitats selected by reintroduced animals may provide early 
indications of the success of reintroduction efforts. If patterns of space use by 
reintroduced individuals mimic habitat selection by free-ranging animals from source 
populations then opportunities for achieving growth rates and reproduction levels 
equivalent to those of the source populations should be maximized on reintroduction sites 
(Himes et al. 2006).  Additionally, gaining an understanding of how reintroduced animals 
select habitat at release sites, including the scale of selection, may provide valuable 
insight for adaptive management at current release sites, as well as enhancing the 
 4 
potential for success in future reptile reintroductions. For these reasons, in this study, I 
examined not only which habitats were selected, but also how habitats were selected by 
indigo snakes reintroduced to CNF.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 5 
Chapter 2 
 
Seasonal Habitat and Shelter Selection by Reintroduced Eastern Indigo Snakes in 
Conecuh National Forest, Alabama 
 
 
Abstract 
Species reintroduction has become an increasingly popular conservation method 
for reestablishing extirpated populations of declining species. Because poor habitat 
quality at release sites has been one of the most frequently reported reasons for failure of 
reintroductions, evaluating habitats selected by reintroduced animals is of paramount 
importance. I radio-tracked 38 Eastern Indigo Snakes reintroduced to Conecuh National 
Forest, Alabama. My study objectives were to: 1) quantify habitat and shelter selection at 
multiple spatial and temporal scales, 2) compare results from my study to the results of a 
study of a wild population near the source sites, 3) evaluate whether hierarchical habitat 
selection occurred in reintroduced snakes, and 4) inform future management of habitat at 
the release site. My results document that habitat selection in reintroduced snakes 
occurred at multiple spatial and temporal scales.  At a landscape scale, snakes selected 
fields and roads and mixed pine-hardwood habitats significantly more than wetlands and 
hardwoods. Habitat selection at a home range scale was not significant overall, although 
open canopy longleaf pine forest was selected significantly more than mixed pine-
hardwood forest. However, when seasons were examined separately, significant 
differences emerged at the home range scale. During the spring, summer, and fall 
months, snakes selected open canopy longleaf pine forests significantly more than fields 
and roads or mixed pine-hardwood habitats. During winter months, snakes selected fields 
 6 
and roads significantly more than wetlands and hardwood or mixed pine-hardwood 
habitats. Among sites used as shelters, gopher tortoise burrows ranked highest, followed 
by stump/root in both non-winter and winter seasons. Snakes in my study used habitats 
and shelters in a manner similar to that of snakes studied previously in Georgia near the 
source sites of my snakes. Selection was strongest at shelter and landscape scales when 
compared to home range scale and, therefore, I conclude that habitat selection by 
reintroduced snakes in my study was not hierarchical. My observations indicate that 
maintenance of high quality gopher tortoise habitat, including prescribed burning to 
maintain open-canopied habitats, will be critical for the successful reestablishment of 
Eastern Indigo Snake populations in the northern part of its range.  
 
Introduction 
Population decline is a growing problem that is affecting reptile species on a 
global scale (Gibbons et al. 2000). In order to address this burgeoning crisis, species 
reintroduction has become a practical recourse for reestablishing extirpated populations 
of declining species. Unfortunately, the success rate for this method has been variable 
and many attempts have either failed or have lacked conclusive assessments of their 
success (Fischer and Lindenmayer 2000).  
Poor habitat quality at release sites has been one of the most frequently reported 
reasons for failure in reptile and amphibian reintroductions (Germano and Bishop 2009). 
Additionally, it has been shown that animals experiencing a new environment may 
respond with abnormal behaviors including abnormal use of habitat, which may increase 
 7 
mortality (Roe et al. 2010). To minimize these problems, it has been recommended that 
habitats selected as release sites should be as similar to the habitat at the source site as 
possible (Osborne and Seddon 2012) and also that chosen habitats be reevaluated after an 
initial release to inform continuing management at the release sites (Cook et al. 2010).  
Habitat selection is the process by which an animal chooses a habitat (Johnson 
1980). In habitat selection studies, selection for a particular habitat is inferred when the 
use of a habitat defined in the study differs from its availability (Manly et al. 2002).  
Choosing the appropriate scale for habitat selection studies may affect the study?s ability 
to detect how a species responds to its environment because ecological patterns and 
processes are scale-dependent (Wiens 1989). Jenkins et al. (2009) recommended that a 
priori scales of investigation not be set, but instead concluded that habitat selection 
examined at multiple scales would offer a better understanding of how animals relate to 
their environment. 
  In snakes, habitat selection has been shown to vary across space (i.e., geographic 
range of a species; Martino et al. 2012) as well as time (i.e., seasonally; Waldron et al. 
2006). This variation underscores the importance of understanding how habitats are 
selected by reintroduced animals.  Habitat selection is thought to be a hierarchical process 
in which finer scales of selection are dependent on coarser scales. Johnson (1980) defines 
first, second and third order selection by ranking selection orders from coarser to fine 
scale. The landscape or coarse scale of selection is thought to be the most revealing for 
driving selective behaviors that minimize the effects of limiting factors in the 
environment (Rettie and Messier 2000), but some studies suggest that this may not apply 
to ectotherms (Harvey and Weatherhead 2006). Understanding the scale of selection is 
 8 
important for gaining insight into the ecology of an animal (Wiens 1989) and is 
particularly crucial for reintroduced snakes because habitat selection affects animal 
physiology, especially among ectotherms (Huey 1991). For this reason, I examined 
habitat selection by reintroduced Eastern Indigo Snakes (Drymarchon couperi), referred 
to hereafter as indigo snakes, at multiple spatial and temporal scales.  
Indigo snakes were federally listed as a threatened species in 1978 due to habitat 
loss and degradation, overcollecting, and mortality caused by gassing of gopher tortoise 
burrows (Speake 1993). Across most of its historic range, this species is strongly 
associated with sandhills bordering wetland habitats (Hyslop 2007) within the longleaf 
pine ecosystem of the southeastern United States, a forest type now recognized as one of 
the most endangered in the world (Frost et al. 1986; Noss 1989; Stout and Marion 1993). 
Previous studies of the indigo snake in the northern part of its range have indicated that 
shelter availability may be a potent environmental constraint (Hyslop et al. 2009; Speake 
et al. 1978). In particular, indigo snakes in this part of their range are documented to rely 
chiefly on Gopher Tortoise (Gopherus polyphemus) burrows for shelter, especially in 
winter. These deep burrows provide important protection from temperature extremes and 
may constitute a critical habitat component limiting the northern distribution of indigo 
snakes to areas where this commensal species is abundant.  
One measure of success for reintroductions is habitat use that mirrors that of 
individuals from the source populations. Studies that use information gained from wild 
populations (Himes et al. 2006) may provide early indications of the challenges 
reintroduced animals face in adapting to a new environment. I compared the results of my 
study to Hyslop (2007), who examined wild indigo snakes near the source sites of snakes 
 9 
obtained for this multi-partner reintroduction project. My study objectives were to 1) 
quantify habitat and shelter selection at multiple spatial and temporal scales, 2) compare 
results from my study to the results of a study of a wild population near the source sites, 
3) evaluate whether hierarchical habitat selection was documented in reintroduced 
snakes, and 4) inform future management of habitat at the release site.  
 
Methods 
Study Area 
This study was conducted in Conecuh National Forest (CNF), Alabama, a 
longleaf pine forest encompassing approximately 34,000 hectares and bordering 
Blackwater River State Forest in neighboring Florida. Combined, these two forests 
provide ca. 117,000 hectares of connected habitats, representing one of the largest 
contiguous tracts of longleaf pine forests remaining in the southeastern United States. 
Additionally, the CNF supports the largest populations of gopher tortoises occurring on 
public lands in Alabama (Guyer et al. 2011), making it an area vital to indigo snake 
conservation in the northern portion of the snake?s range.  
A reintroduction effort for indigo snakes is currently under way in Compartment 
28 of CNF within the 9,458 hectare Blue Springs Wildlife Management Area (WMA). 
Soils in the area include a range of upland and lowland types: Troup loamy sand (0 to 5% 
slopes), Bonifay loamy fine sand (5 to 10% slopes), and Muckalee, Bibb, and Osier soils 
(0 to 2% slopes, frequently flooded) (Cotton 1989). These soils support diverse upland 
and lowland plant communities on CNF including longleaf pine-dominated rolling clay 
 10 
hills and sandhills that support gopher tortoises; pine flatwoods; mesic hammocks and 
bays; wildlife food plots and old fields; hardwood-dominated ravines; rivers, creeks, 
permanent, semi-permanent and ephemeral ponds; and herb and shrub bogs. CNF 
implements management focused on restoring the longleaf pine ecosystem. Active 
management includes prescribed burning, stand thinning, mechanical and chemical 
removal of offsite pine species, and replanting of longleaf pines on historical longleaf 
sites. Wildlife food plots scattered throughout the WMA are planted primarily for white-
tailed deer (Odocoileus virginianus), wild turkey (Meleagris gallopavo), and northern 
bobwhite (Colinus virginianus), but often support high densities of gopher tortoises as 
well.  
Telemetry 
Eastern Indigo Snakes in this study were the offspring of gravid wild females 
captured by hand in Georgia. Eggs laid by captured females were hatched and reared to 
approximately two years of age in a multi-partner cooperative effort. Surgeries were 
performed to implant snakes with radiotransmitters. Transmitters used were Holohil SB-2 
temperature calibrated with the following specifications: weight of 5.0g, length x 
diameter (mm) of 19 x 9.5, and lifespan of 10 months (range 6-12 months). Snakes 
surviving their first year post release were captured and surgically fitted with Holohil SI-
2T transmitters with the following specifications: weight of  13.5g, length x diameter 
(mm) of  50 x 11,  and lifespan of 24 months (range of 12-30 months). Following 
surgery, each snake was placed in a circular fiberglass tub (2.27 meters tall by 4.55 
meters across) that was covered by a hardware cloth and shade cloth lid. These tubs were 
located outdoors at the North Auburn Fisheries Unit and contained a sand bottom, a large 
 11 
water bowl, a variety of artificial surface cover types and access to an underground 
chamber made of 7.7 cm diameter Polyvinyl chloride (PVC) pipe. Snakes remained in 
tubs approximately two months before their release on CNF. A total of 38 snakes were 
fitted with transmitters and released on CNF, 17 snakes on 16 June 2010 (nine males, 
eight females) and 21 snakes (10 males, 11 females) on 16 May 2011. After release, a 
Communications Specialist R-1000 Telemetry Receiver coupled with a directional hand-
held antenna was used to locate snakes approximately 1-3 times per week. Upon study 
completion, I recaptured snakes when possible and surgically removed transmitters. 
 
Compositional Habitat Selection Analyses 
I radio-tracked Eastern Indigo Snakes (n=38) reintroduced to Conecuh National 
Forest, Alabama from 17 June 2010 - 1 April 2012 to evaluate post-release habitat and 
shelter selection. I performed all habitat selection analyses using the Compositional 
Analysis method (Aebischer et al. 1993) and the program BYCOMP.SAS (Ott and Hovey 
1997) in SAS Version 9.2 (SAS Institute, Cary, North Carolina). Habitat types occurring 
in the study area were characterized from existing AL-GAP categories (Kleiner et al. 
2007). Accuracy of data was assessed both visually in GIS and on the ground. Any 
inaccuracies found were minor and were updated when these fine scale categories were 
assigned to broader scale habitat categories used in this study. For this method, Aebischer 
et al. (1993) suggest either removing animals that did not have all habitats available to 
them, or merging habitats to reduce the number of habitat categories. Rather than 
excluding a large number of animals from my analysis, I chose to combine some similar 
habitat categories into a single category. Habitat types that constituted less than three 
 12 
percent of the study area (i.e. open water, low intensity developed, medium intensity 
developed, evergreen plantations and row cop) were removed because including rare 
habitats can negatively affect analyses.  
If a habitat that was available was not used by an animal, the zero use was 
replaced by a small non-zero value (0.0001) because this method cannot accept missing 
use values for available habitats (Moore and Gillingham 2006; Aebischer et al. 1993). 
For my landscape scale analysis, there were no zero values for use because all animals 
used every habitat type, therefore no zero values were replaced; all snakes had >15 
locations (range 16-115), and no habitat type included was <3% of study area. For my 
non-seasonal home range analysis, nine zero values were replaced, all snakes had >15 
locations (range 16-115), and no habitat type included was <3% of study area.  For my 
non-winter home range scale analysis, eleven zero values were replaced, all snakes had 
>15 locations (range 16-115), and no habitat type included was <3% of study area. For 
my winter home range scale analysis, twenty-six zero values were replaced, all snakes 
had >15 locations (range 16-115), and no habitat type included was <3% of study area.   
Four habitat types were delineated for use in landscape and home range scale 
compositional analyses: 
Fields and Roads- This category included dirt and paved roads, anthropogenically 
disturbed and early successional habitats such as regenerating clearcuts, pasture/ hay 
fields and wildlife food plots. It is characterized by either a complete lack of canopy or an 
extremely sparse canopy. This category combines four AL-GAP categories: Developed 
Open Space, Successional Shrub/ Scrub Clearcut, Successional Shrub/ Scrub Other and 
Pasture/ Hay.  
 13 
Wetlands and Hardwood- This category combines upland areas, mesic slope forest, 
floodplain forest and wetland areas with >75% hardwood overstory. It is characterized by 
a dense canopy that creates a heavy shade. This category combines three AL-GAP 
categories: East Gulf Coastal Plain Southern Mesic Slope Forest, Southern Coastal Plain 
Blackwater River Floodplain Forest, and East Gulf Coastal Plain Interior Upland 
Longleaf Pine Woodland-Offsite Hardwood Modifier.  
Open Canopy Longleaf- This category includes >75% pine with an open canopy 
maintained by more frequent fire. It is typically composed of longleaf pine with a low 
herbaceous understory. This category is the AL-GAP category East Gulf Coastal Plain 
Interior Upland Longleaf Pine Woodland-Open Understory Modifier. 
Mixed Pine-Hardwood- This category includes >75% pine with a relatively more dense 
canopy than open canopy longleaf pine forest resulting from infrequent fire and mature 
hardwood trees scattered in the canopy. It is characterized by a tall shrub layer and a 
denser canopy when compared with open canopy longleaf. This category is the AL-GAP 
category East Gulf Coastal Plain Interior Upland Longleaf Pine-Loblolly Modifier 
(although on my study site, it is more typically a slash pine and hardwood modifier).  
I examined habitat selection at the scale of landscape, home range and shelter. I 
also examined selection seasonally because habitats used by indigo snakes studied near 
the source populations differed by season (Hyslop 2007). Therefore, at the home range 
and shelter scales, I divided data into winter and non-winter seasons. I chose to include 
two rather than four seasons because: 1) these two categories represent time periods that 
are relevant for snakes in this area, 2) I expected winter to be particularly challenging for 
indigo snakes, and 3) this division allowed for robust sample sizes. Individual snakes 
 14 
were used as the sampling unit for all analyses. For snakes tracked in multiple years, data 
were combined to create a single time sequence (Harvey and Weatherhead 2006).   
The study area was defined by creating a 100% minimum convex polygon (MCP) 
of all known locations for all snakes over the entire study. The 100% minimum convex 
polygon defines home range as the smallest convex polygon encompassing all known 
locations (Hayne 1949). I used the Hawth?s Tools extension (Beyer 2004) for ArcGIS 
(ESRI, Redlands, California) to construct MCPs for each snake. For landscape-scale 
habitat selection, I compared the proportion of habitats within the 100% MCP home 
range of each snake (n=29; use) to the proportion of habitats available within the total 
study area (availability).   
Home-range-scale habitat selection was examined by comparing the proportion of 
habitats at telemetry locations for each snake (use) to the proportion of habitats available 
within the 100% MCP of each snake (available). I first analyzed home range scale using 
all data (n=29). I then analyzed winter (15 December - 14 March; n= 16) and non-winter 
(15 March- 14 December; n=29) habitat selection separately.  
To examine shelter selection, underground retreats  (n=1089) were classified as 
Gopher Tortoise burrows (tortoise), stumpholes, rootballs or root channels (stump/root), 
armadillo burrows (armadillo), small mammal burrows (mammal), logs or downed 
woody debris (log), or other underground shelters (other).  If a snake had not moved 
locations since the last time it was tracked, I included the same location in analyses 
multiple times (DeGregorio et al. 2011). To examine the importance of Gopher Tortoise 
burrows in overwintering by reintroduced snakes, I examined shelter use seasonally as 
winter (15 December -14 March; n=18), and non-winter (15 March-14 December; n=38) 
 15 
periods. In both analyses, individual snakes comprised the sample unit and values were 
mean proportions of total use. Availability of underground shelters was estimated by 
raking transects (n=49) at randomly generated points (n=14) in the study area and 
recording all shelters found in each category. Transects were 100 meters long by 2 meters 
wide and extended from the center point out to the intercardinal directions.  Whenever 
possible, I surveyed all four of the intercardinal transects at each point, however, 
occasionally transects landed in areas I could not survey (i.e. private land, open water). 
Therefore, at each point I surveyed 2-4 of the intercardinal transects. The points were 
used as the sampling unit and values are mean proportions.  Compositional analysis 
(Aebischer et al. 1993) was used to compare proportional shelter use in both seasons to 
the proportion of shelters available at my study site. For seasonal analyses, I assumed that 
shelters were equally available to snakes in winter and non-winter seasons.   
 
Analyses for Comparison with Previous Study 
In addition to compositional analyses of habitat selection, I performed additional 
analyses in order to compare habitat and shelter use by reintroduced snakes to the results 
documented for wild snakes studied near the source population. Because data were not 
appropriate for using the Compositional Analysis method on categories characterized in 
the previous study, I was unable to compare the results of my compositional analysis to 
results from the previous study using this method. To compare reintroduced snakes to 
wild snakes studied near the source population of my snakes at landscape and home range 
scales, I classified habitats into categories matching those identified by Hyslop, (2007). 
These habitat categories, adapted from GAP classifications, consisted of roads and urban 
 16 
areas (roads); open water, forested and non-forested wetlands (wetland); agricultural and 
other fields (field); clearcuts and other sparsely vegetated habitats (cc/sparse); forests 
with at least 75% deciduous trees (deciduous); forests with at least 75% evergreen trees, 
including pine plantations (evergreen); and pine-hardwood mixed forest, including 
shrub/scrub habitats (mixed).  
For my comparison, I assigned pre-existing AL-GAP categories occurring on my 
study site in a manner to most accurately fit these categorical descriptions. My categories 
were as follows: Developed Open Space, Low Intensity Developed and Medium Intensity 
Developed (roads); Open Water, East Gulf Coastal Plain Southern Mesic Slope Forest 
and Southern Coastal Plain Blackwater River Floodplain Forest (wetland); Pasture/ Hay 
and Row Crop (field); Successional Shrub/ Scrub Clearcut and Successional Shrub/ 
Scrub Other (cc/ sparse); East Gulf Coastal Plain Interior Upland Longleaf Pine 
Woodland- Offsite Hardwood Modifier (deciduous); Evergreen Plantations and East Gulf 
Coastal Plain Interior Upland Longleaf Pine Woodland- Open Understory Modifier 
(evergreen); and East Gulf Coastal Plain Interior Upland Longleaf Pine Woodland- 
Loblolly Modifier (mixed).  I also provide a comparison of mean proportional availability 
of these habitat types for each site at landscape scale in order to aid the interpretation of 
the results of my comparison.  
To compare shelter use in reintroduced snakes in this study with shelters used by 
wild indigo snakes in Georgia (Hyslop et al. 2009), categories were classified following 
the descriptions of the previous study, excepting windrows, which were not available on 
my study site. The remaining categories included Gopher Tortoise burrows (tortoise), 
stumpholes, rootballs or root channels (stump/root), armadillo burrows (armadillo), small 
 17 
mammal burrows (mammal), logs or downed woody debris (log), and other underground 
shelters (other). 
 
Results 
Compositional Habitat Selection Analyses 
For my landscape-scale compositional analysis, I delineated my 3,334 hectare 
study area by creating a 100% minimum convex polygon encompassing all telemetry 
points (n= 1641) collected for all snakes tracked during my study. Results of my 
Compositional Analysis at a landscape scale (n=29) indicated overall habitat selection 
(Wilks lambda 0.649; F= 4.73; p= 0.0092). Fields and roads and mixed pine-hardwood 
were selected significantly more than wetlands and hardwood at this scale (Table 1).    
Home-range scale, when examined non-seasonally using all data (n=29), did not 
indicate selection at p< 0.05 (Wilks Lambda 0.790; F= 2.30; p= 0.1011), indicating that 
snakes did not demonstrate strong overall habitat selection at this scale of inquiry, 
although open canopy longleaf was selected significantly more than mixed pine-
hardwood (Table 2).     
However, when home-range scale was examined seasonally, selection was 
indicated for both non-winter and winter seasons. Non-Winter home range scale (n=29) 
analysis indicated overall selection (Wilks Lambda 0.715; F= 3.46; p= 0.0308). Open 
canopy longleaf was selected significantly more than fields and roads or mixed pine-
hardwood (Table 3).    
 18 
Winter analysis (n=16) at a home-range scale also indicated overall selection (Wilks 
Lambda 0.521; F= 3.98; p= 0.0325). Fields and roads were selected significantly more 
than wetlands and hardwood or mixed pine-hardwood (Table 4).     
Shelter use in both winter and non-winter seasons differed significantly from 
availability. Compositional analysis of non-winter shelter use versus availability 
indicated overall shelter selection (Wilks Lambda 0.213; F= 24.42; p= < 0.0001; Table 
5). Tortoise, stump/root, armadillo and other were selected significantly more than 
mammal or log. Tortoise was also selected significantly more than other. Compositional 
analysis of winter shelter use versus availability indicated overall shelter selection (Wilks 
Lambda 0.053; F= 46.16; p= < 0.0001; Table 6). Tortoise, stump/root, armadillo, and 
other were selected significantly more than mammal or log. Mammal was selected 
significantly more than log. Tortoise was selected significantly more than all other shelter 
types.  
Comparison with Previous Study 
Differences in proportional use and availability of habitats characterized by 
Hyslop (2007) at a home-range scale indicated that reintroduced snakes in my study used 
CC/ Sparse more than available and Mixed less than available (??, 95% CI; n= 30; Figure 
1) At a landscape scale, wetlands were used less than available and CC/ sparse and 
deciduous were used more than available (??, 95% CI; n= 30; Figure 1).  
Hyslop (2007; Figure 2.4) shows the differences in proportional use and 
availability of habitats for wild indigo snakes (?? , 95% CI; n=27). Roads, wetlands and 
evergreen areas were used less than available and CC/ Sparse and mixed were used more 
 19 
than available at a home range scale. At a landscape scale, evergreen was used less than 
available and CC/Sparse and mixed were used more than available.  
The mean availability and uses of habitat types characterized after Hyslop (2007) 
differed from my study site when examined at a landscape scale (Figure 3.1).   
Shelter use was similar between my study and that of Hyslop (2009), and snakes 
used a high proportion of gopher tortoise burrows, roots and stumps as shelters at both 
study sites. Hyslop (2009) found a high proportion of gopher tortoise burrows were used 
in all seasons when compared to other shelter types (Figure 3). At my study site, gopher 
tortoise burrows were also used throughout the year, but use was highest in winter and 
stump/root use was highest in non-winter (Figure 4).  
 
Discussion 
Habitat loss is known to be one of the greatest threats to imperiled species 
(Wilcove et al. 1998).  In recent years, restoration biology has led to an increased effort 
to restore degraded habitats, but few studies have examined the response of reptiles to 
habitat restoration (Steen et al. 2013). Reintroductions of extirpated animals to restored 
habitats as a conservation measure for imperiled species has become an increasingly 
common procedure (Fischer and Lindenmayer 2000).  Despite an increased recognition 
of the importance of habitat selection in reintroduction success, this aspect of 
reintroductions remains understudied, especially in reptiles (Germano and Bishop 2009).    
Reintroduced indigo snakes in this study selected habitats at multiple spatial and 
temporal scales. This result was not surprising since a number of snake species have been 
 20 
documented as exhibiting multi-scale selection (e.g., Moore and Gillingham 2006; Steen 
et al. 2010; Baxley et al. 2011). However, documenting habitat use in imperiled snakes 
can lead to important recommendations for promoting enhanced conservation of these 
declining species (e.g., Webb and Shine 2000). Using multi-scale selection studies is less 
of an attempt to discover the correct scale of investigation for studying habitat in an 
animal than it is a tool for understanding how selection changes across scales. 
Determining what information is retained or lost as scales change should aid in our ability 
to detect patterns (Levin 1992).  
In this study, at a landscape scale, reintroduced indigo snakes positioned their 
home ranges in areas with more fields, roads; and mixed pine-hardwood habitats; these 
same home ranges contained less wetlands and hardwood habitats than expected by 
chance. Fields and roads and mixed pine-hardwood habitats may provide resources for 
reintroduced indigo snakes that are more limited than the resources found within 
wetlands and hardwoods and open canopy longleaf habitats on my study site.   
My non-seasonal compositional analysis at a home-range scale did not indicate 
significant overall habitat selection for my model, although open canopy longleaf habitat 
was selected significantly more than mixed pine hardwood habitat. The lack of strong 
significance in the overall model at this scale suggests that snakes did not demonstrate 
strong selection for particular habitat types at this scale, suggesting that with the 
exception of a preference for open canopy longleaf when compared to mixed pine 
hardwood, other habitats were used in proportion to their availability, indicating no 
limiting difference in habitat types at this scale.  
 21 
At the home range scale, I detected a seasonal pattern of habitat selection in 
Eastern Indigo Snakes. Open canopy longleaf was selected significantly more than fields 
and roads or mixed pine hardwood habitats in spring, summer and fall. In winter, field 
and roads habitats were selected significantly more than wetlands and hardwoods or 
mixed pine-hardwood habitats. I found that habitat selection varied by season, with the 
most open habitat type (fields and roads) selected most in winter and least in spring, 
summer and fall. Thermoregulation may be a particularly important aspect of habitat 
selection in snakes (Webb and Shine 1998). Because the CNF lies at the northern extent 
of the geographic range of the indigo snake, it may have had a strong influence on habitat 
selection in this study.   
My examination of shelter use in both non-winter and winter seasons indicated 
that habitat selection by reintroduced indigo snakes was strongest at this finest scale of 
examination as the snakes selected shelters. My non-winter shelter analysis indicated that 
the categories tortoise burrow, stump/root, armadillo, and other were selected 
significantly more than mammal or log, and tortoise was also selected significantly more 
than other. My compositional analysis of winter shelter selection found selection at this 
spatial and temporal scale to be the strongest for all scales examined in this study. Stump/ 
root; armadillo; and other were chosen significantly more than mammal or log. Mammal 
was chosen significantly more often than log. Gopher tortoise burrows were chosen 
significantly more frequently than every other shelter type, indicating that this shelter 
type may be an especially limiting resource for indigo snakes at my study site in the 
winter season. Although my results suggest that stumps, roots and armadillo burrows may 
provide adequate shelters for indigo snakes in the non-winter seasons, it appears that 
 22 
gopher tortoise burrows represent a potentially critical habitat component for indigo 
snakes surviving the winter in this most northern part of their geographic range.  
My rigorous examination of habitat selection at multiple spatial and temporal 
scales demonstrated a complex pattern of habitat selection by reintroduced indigo snakes 
on my study site. My findings that the strength of habitat selection varied depending on 
the scale examined underscores the importance of investigating many scales of space and 
time to better understand how reintroduced snakes are responding to their new 
environment. Hierarchical habitat selection theory suggests that factors most limiting to 
animals will be ordered by selection orders, with the coarsest selection orders indicating 
the most relevant limitations to animals (Rettie and Messier 2000; Mayor et al. 2009). 
Selection at multiple scales does not necessarily imply a ?top down? hierarchy however, 
and if finer scale resources such as shelter are not constrained by broader scales such as 
habitat type, then it is possible that fine scale decisions are influencing broad scale 
patterns detected in a ?bottom up? manner (Mayor et al. 2009).  
For snakes selecting habitat at my study site, the order of selection by strength 
was winter shelter, non-winter shelter, landscape, non-winter home range, winter home 
range and lastly non-seasonal home range. Although my results initially appeared to 
support a pattern of hierarchical habitat selection grading from coarse scale to fine scale 
by reintroduced indigo snakes, I conclude that hierarchical habitat selection was not 
documented in my study. Selection was strongest at the finest spatial and temporal scales. 
It is possible that ectothermy impedes free distribution between habitats at coarser scales 
and thermoregulation may affect the process of habitat selection in reptiles (Rubio and 
Carrascal 1994). Although I was unable to quantify the availability of shelter types by 
 23 
habitat type during this study, I believe as suggested by Harvey and Weatherhead (2006) 
that the strength of selection found in my landscape scale compositional analysis is likely 
to be a result of the shelter types available within these broad scale habitats rather than 
the occurrence of the habitat types themselves in my study area.  Future studies should 
attempt to resolve this in order to better understand how selection in snakes and 
reintroduced snakes might differ from the hierarchical pattern documented for other 
vertebrate species.  
My comparison of the results of habitat and shelter use by reintroduced snakes in 
my study on categories characterized by Hyslop (2007) with the results from the previous 
study (Hyslop 2007, 2009) indicate that indigo snakes in my study used habitats and 
shelters in a manner similar to snakes studied previously near the source sites of my 
snakes. Apparent differences can be attributed to differing availabilities of habitat types 
at each study site (See Figure 3.1.).  
At the landscape scale, snakes in my study used CC/ Sparse and Deciduous more 
than available and Wetland less than available, whereas, Hyslop?s snakes used CC/Sparse 
and Mixed more than available and Evergreen less than available.  CC/Sparse was used 
more than available at both study sites, indicating that this habitat type may be a limiting 
resource for indigo snakes in the northern part of their range.   
At the home range scale, snakes in my study used CC/ Sparse more and Mixed 
less than available, whereas, Hyslop?s snakes used CC/ Sparse and Mixed more than 
available and Roads, Wetlands and Evergreen less than available at this scale.  The 
finding that the CC/Sparse category was used more than available at this scale as well as 
 24 
the landscape scale in both studies, again emphasizes the potential for this habitat type to 
contain a limited resource for snakes in this part of their geographic range.   
Hyslop (2007) described the CC/ Sparse habitat category as clearcuts and other 
habitats with sparse canopy cover, and added in her discussion that the specific areas 
used by snakes were not clearcuts, but predominantly young longleaf pine plantations 
with gopher tortoise populations used especially in winter. On my study site, this 
category contained the AL-GAP categories Successional Shrub/ Scrub-Clearcut and 
Successional Shrub/ Scrub-Other. For my compositional analyses, these two categories 
were combined with Developed Open Space and Pasture/ Hay to create a single category, 
Fields and Roads. It is likely no coincidence that this habitat category, which has the 
most open canopy of all habitat types in my analyses and has a large number of gopher 
tortoise burrows within it, ranked highest in my compositional analyses at both landscape 
and winter home range scales. Both the CC/Sparse categories in my comparison and the 
Fields and Roads category used for compositional analyses are likely to represent a 
limiting habitat component tied to thermoregulation constraints. This relationship 
between open-canopied habitats, gopher tortoise burrow abundance and thermoregulation 
should be explored further in future studies of indigo snakes in the northern part of their 
range.  
A comparison of shelter use by reintroduced snakes at my study site and snakes 
studied near the source site also indicated that habitat use by reintroduced snakes at my 
site was similar to shelters used by snakes in a previous study. Indigo snakes used a high 
proportion of gopher tortoise burrows, roots and stumps as shelters at both study sites. 
Hyslop et al. (2009) found a high proportion of gopher tortoise burrows were used in all 
 25 
seasons when compared to other shelter types. At my study site, gopher tortoise burrows 
were also used throughout the year, but use was highest in winter and stump/root use was 
highest in non-winter. Stumpholes and rootballs are known to be an important habitat 
component for many snake species (Means 2006). On CNF snakes were using primarily 
stumpholes left from fallen longleaf pine trees that had rotted away to heartwood. These 
holes were likely to be deep because the tap root of the longleaf pine tree can penetrate 
up to 5 meters deep and its lateral roots can be 22 meters long (Heyward 1933). The 
practice of pulling stumps for turpentine production and to clear agricultural fields still 
persists in this area on surrounding private lands and has made these components of the 
landscape increasingly rare.  
Because poor habitat quality at release sites is frequently reported as a reason for 
failure in reptile and amphibian reintroductions (Germano and Bishop 2009), habitat use 
that mirrors that of individuals from the source populations can be viewed as a measure 
of success for reintroductions. Reintroduced indigo snakes in my study used shelters in a 
manner similar to snakes studied previously near the source sites of my snakes. Conecuh 
National Forest lies in the northern extent of the geographic range of Drymarchon 
couperi. Previous studies in the northern part of its range have indicated that shelter 
availability may be a potent environmental constraint for indigo snakes (Hyslop et al. 
2009; Speake et al. 1978). My results documented that habitat selection by reintroduced 
indigo snakes occurred at multiple spatial and temporal scales, but was driven strongest 
by shelter, especially winter shelter. These results reinforce conclusions from other 
studies that the distribution of gopher tortoise burrows might be the most limiting factor 
for survival in this part of the range.  
 26 
Understanding how spatial and temporal scales affect the strength of habitat 
selection for a species may allow us to better predict how animals may respond to 
environmental changes. It is also vital for informing decisions in adaptive management 
and aiding land managers in future decisions for appropriate reintroduction sites. Based 
on the results of my study, I recommend that areas chosen for reintroduction sites for 
indigo snakes in the northern part of their range contain habitats that include open 
canopies and abundant gopher tortoise burrows. Managers should retain stumpholes 
across the landscape, especially the deep holes left by longleaf pine. Release sites lacking 
these habitat characteristics may force reintroduced snakes into roads and open areas like 
food plots which may increase their vulnerability to traffic fatalities and human 
persecution. My observations indicate that maintenance of high quality gopher tortoise 
habitat, including prescribed burning to maintain habitats with open canopies will be 
critical for reestablishing indigo snake populations in this part of their range. 
 
 
 
 
 
 
 
 
 27 
 
 
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 36 
Habitat Type Fields and 
Roads 
Wetlands 
and 
Hardwood 
Open 
Canopy 
Longleaf 
Mixed Pine 
Hardwood 
Rank 
Fields and Roads . +++ + + 3 
Wetlands and Hardwood --- . - --- 0 
Open Canopy Longleaf - + . - 1 
Mixed Pine Hardwood - +++ + . 2 
 
Table 1. Ranking Matrix from Compositional Analysis Comparing Proportional Landscape Scale 
Habitat Use Versus Proportion Available to Eastern Indigo Snakes (n=29). Higher rank indicates 
higher disproportionate use. A single sign indicates the row category was used more (+) or less (-
) than the column category, but was not significantly different. A triple sign indicates the row 
category was used significantly more (+++) or less (---) than the column category with a 
significant deviation from random at p< 0.05. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 37 
Habitat Type Fields and 
Roads 
Wetlands 
and 
Hardwood 
Open 
Canopy 
Longleaf 
Mixed Pine 
Hardwood 
Rank 
Fields and Roads . - - - 0 
Wetlands and Hardwood + . - + 2 
Open Canopy Longleaf + + . +++ 3 
Mixed Pine Hardwood + - --- . 1 
 
Table 2. Ranking Matrix from Compositional Analysis Comparing Proportional Non-Seasonal 
Home Range Scale Habitat Use Versus Proportion Available to Eastern Indigo Snakes (n=29). 
Higher rank indicates higher disproportionate use. A single sign indicates the row category was 
used more (+) or less (-) than the column category, but was not significantly different. A triple 
sign indicates the row category was used significantly more (+++) or less (---) than the column 
category with a significant deviation from random at p< 0.05. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 38 
Habitat Type Fields and 
Roads 
Wetlands 
and 
Hardwood 
Open 
Canopy 
Longleaf 
Mixed Pine 
Hardwood 
Rank 
Fields and Roads . - --- - 0 
Wetlands and Hardwood + . - - 1 
Open Canopy Longleaf +++ + . +++ 3 
Mixed Pine Hardwood + + --- . 2 
 
Table 3. Ranking Matrix from Compositional Analysis Comparing Proportional Non-Winter Home 
Range Scale Habitat Use Versus Proportion Available to Eastern Indigo Snakes (n=29). Higher 
rank indicates higher disproportionate use. A single sign indicates the row category was used 
more (+) or less (-) than the column category, but was not significantly different. A triple sign 
indicates the row category was used significantly more (+++) or less (---) than the column 
category with a significant deviation from random at p< 0.05. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 39 
Habitat Type Fields and 
Roads 
Wetlands 
and 
Hardwood 
Open 
Canopy 
Longleaf 
Mixed Pine 
Hardwood 
Rank 
Fields and Roads . +++ + +++ 3 
Wetlands and Hardwood --- . - - 0 
Open Canopy Longleaf - + . + 2 
Mixed Pine Hardwood --- + - . 1 
 
Table 4. Ranking Matrix from Compositional Analysis Comparing Proportional Winter Home 
Range Scale Habitat Use Versus Proportion Available to Eastern Indigo Snakes (n=16). Higher 
rank indicates higher disproportionate use. A single sign indicates the row category was used 
more (+) or less (-) than the column category, but was not significantly different. A triple sign 
indicates the row category was used significantly more (+++) or less (---) than the column 
category with a significant deviation from random at p< 0.05. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 40 
Shelter Type Tortoise Stump/Root Armadillo Mammal Log Other Rank 
Tortoise . + + +++ +++ +++ 5 
Stump/Root - . + +++ +++ + 4 
Armadillo - - . +++ +++ + 3 
Mammal --- --- --- . - --- 0 
Log --- --- --- + . --- 1 
Other --- - - +++ +++ . 2 
 
Table 5. Ranking Matrix Comparing Proportional Non-Winter Shelter Use Versus Proportion 
Available to Eastern Indigo Snakes (n=38) at Home Range Scale. Higher rank indicates higher 
disproportionate use. A single sign indicates the row category was used more (+) or less (-) than 
the column category, but was not significantly different. A triple sign indicates the row category 
was used significantly more (+++) or less (---) than the column category with a significant 
deviation from random at p< 0.05. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 41 
 
Shelter Type Tortoise Stump/Root Armadillo Mammal Log Other Rank 
Tortoise . +++ +++ +++ +++ +++ 5 
Stump/Root --- . + +++ +++ + 4 
Armadillo --- - . +++ +++ - 2 
Mammal --- --- --- . +++ --- 1 
Log --- --- --- --- . --- 0 
Other --- - + +++ +++ . 3 
 
Table 6. Ranking Matrix Comparing Proportional Winter Shelter Use Versus Proportion Available 
to Eastern Indigo Snakes (n=18) at Home Range Scale. Higher rank indicates higher 
disproportionate use. A single sign indicates the row category was used more (+) or less (-) than 
the column category, but was not significantly different. A triple sign indicates the row category 
was used significantly more (+++) or less (---) than the column category with a significant 
deviation from random at p< 0.05. 
 
 
 
 
 
 
 42 
 
Figure 1. Differences in proportional use and availability of habitats characterized after Hyslop 
2007 at home range and landscape scales for reintroduced indigo snakes in Conecuh National 
Forest, 2010-2012 (??, 95%CI; n=30).  
 
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
Roads Wetland Field CC/Sparse Deciduous Evergreen Mixed
Pro
po
rti
ona
l D
iffer
enc
e
Home Range
Landscape
 43 
 
 44 
 
Figure 3.1. Comparison of landscape scale mean availability and use of habitat types for Hyslop 
2003-2004 and Stiles 2010-2012. 
 
 
 
 
 
 
 
 
 
 
 
 
 
0
0.1
0.2
0.3
0.4
0.5
0.6
Roads Wetland Field CC/Sparse Deciduous Evergreen Mixed
Pro
po
rti
on
Stiles Available Stiles Used Hyslop Available Hyslop Used
 45 
 
Figure 3. Underground shelter (??, 95% CI) use by Drymarchon couperi radiotracked 2002-2004, 
Georgia. (Hyslop et al. 2009). 
 
 
 
 46 
 
Figure 4. Mean proportion of shelter use and availablity (??, 95% CI) by Drymarchon couperi in 
winter (n=18) and non-winter seasons (n=38), Conecuh National Forest, AL with individual 
snakes as the sampling unit. 
 
 
 
 
 
 
 
 
 
 47 
Chapter 3 
 
Conclusions 
 
   
1. Habitat selection by reintroduced Eastern Indigo Snakes occurred at multiple 
spatial and temporal scales and selection varied in strength according to the scale 
examined. This result underscores the importance of examining habitat selection 
at many scales.  
 
2. At a landscape scale, indigo snakes selected fields and roads and mixed pine-
hardwood habitats significantly more than wetlands and hardwoods. At my study 
site, fields and roads; and mixed pine-hardwoods are likely to provide resources 
for indigo snakes that are more limited than resources found in wetland and 
hardwood habitats. 
 
3. At home range scale, open canopy longleaf habitats were selected more than 
mixed pine-hardwood habitats; however selection at this scale was strongest when 
examined seasonally. During winter months, snakes selected fields and roads 
significantly more than wetlands and hardwood or mixed pine-hardwood habitats.  
 48 
During the spring, summer, and fall months, snakes selected open canopy longleaf 
significantly more than fields and roads or mixed pine-hardwood habitats.  
 
4. Among sites used as shelters, gopher tortoise burrows ranked highest, followed by 
stump/root in all seasons.  
 
5. Reintroduced snakes in this study used habitats and shelters in a manner similar to 
that of snakes studied previously near the source sites of my snakes.  
 
6. Hierarchical habitat selection was not documented in reintroduced snakes at my 
study site. Selection was instead strongest at shelter and landscape scales when 
compared to home range scale.   
7. Based on my results, I recommend maintaining high quality gopher tortoise 
habitat on current and future release sites for snakes. Management for 
reintroductions that includes prescribed burning to create and maintain open-
canopied habitats will be critical for the successful reestablishment of Eastern 
Indigo Snake populations in the northern part of its range. 
 
 
 
 49 
 
 
 
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