1. Suitable Habitat for Gopher Tortoises at the Jacksonville Arboretum and Gardens
Steven Kelley
GEO 455
May 20, 15
Abstract
Since the Jacksonville Arboretum's inception in 2008, the park's management has
committed itself to the restoration of the park to promote native plant and wildlife
populations. Two of these restorations have been successful in recruiting gopher tortoises
to nest in these areas. This raises the question as to other locations in the Arboretum that
could be restored on behalf of the tortoises. This paper uses GIS map analysis to survey
the Arboretum to determine where suitable tortoise habitat exists. From these
determinations, recommendations are given for possible restoration sites should
management elect to increase tortoise populations in the park.
Key Words: Jacksonville Arboretum, gopher tortoise, site-selection, habitat
preferences, xeric sandhill, upland forest, GIS

2. INTRODUCTION
Description and Natural History of the Jacksonville Arboretum:
The Jacksonville Arboretum and Gardens comprises approximately 120 acres on
Milcoe Road east of the intersection of highway 9A and Monument Road in Jacksonville,
Florida (Fig. 1). The central feature of the Arboretum is a large pond in a depression that
surrounded by gardens and picnic areas. Trails originate from this area expanding into the
park. No trails exist in the northwestern quadrant. An easement for a power line runs
through the park's southern section. The park is bounded on the east by Jones Creek;
smaller creeks run out of it cutting deep ravines into the property. Elevation increases
dramatically in the northern end of the park. Such variation in elevation, shade, and
moisture permits a wide range of habitats from xeric scrubs to wetlands (Jacksonville
Arboretum Group, 2010).
The original longleaf pine forest of the Arboretum was cleared in the 1880s to
make way for a railroad (Jacksonville Arboretum Group, 2010). In 1944, the property
was sold to the Humphries Mining Company
that stripped the lot for titanium alloys,
further degrading the original ecosystem.
Operations ceased in 1944 and the property
was turned over to the City of Jacksonville
buffering a sewage treatment plant from the surrounding neighborhoods. Management of
the lot was minimal and the forest that succeeded it is dominated by a variety of oaks and
other hardwoods. The understory is a mix of saw palmetto, native shrubs, and invasive
exotics. The Jacksonville Arboretum Group acquired the property in 2008 and ever since,
Figure 1 Aerial photograph of the Jacksonville Arboretum

3. multiple restorations have been conducted to revert the
property to more natural conditions (Fig. 2).
The importance of the gopher tortoise to the
Arboretum:
Among JAG's management objectives is to
protect and develop management plans for species of
special concern found in the park. The only animal listed
in the JAG management plan is the gopher tortoise which
was classified as Threatened by the State of Florida in
2007 (Burr, et al, 2012). The likely cause for their
decline at the Arboretum is the effects of decades of habitat degradation due to fire
suppression (Burr, 2012, Jacksonville Arboretum Group, 2010). Additionally, tortoise
recruitment in the Arboretum has been difficult due to its wet habitats and the presence of
urban areas around the park.
Gopher tortoises are keystone species; many other species depend on the presence
of tortoises for their wellbeing. The tortoise's burrow (Fig. 3) provides shelter for roughly
350 other species. Thus by encouraging tortoise recruitment other species in the park
many species are also protected. These burrows average 15 feet in depth and female
tortoises use the burrow's apron (the sand deposit in front of the burrow from which the
burrow is dug) to nest their eggs. Once dug the tortoise will rarely travelling more than 1-
2 acres from the burrow. However, due to their anatomy and girth they are limited to
making burrows to sandier soils. Thus they will recruit exclusively to open, xeric habitats
Lake
Park-
ing
1
2
3
4Jacksonville Arboretum ecozones
and restoration areas
Legend
Wetland Marsh
Streams
Rosemary/Oak Scrub
Open Water
Marsh
Deciduous Forest
Xeric Hammock
1
2
3
4
Turkey Oak Restoration Site
Slash Pine Restoration Site
Rosemary Scrub Site - Small
Rosemary Scrub Site - Large
Figure 2: Jacksonville Arboretum Habitat Map

4. having well-drained soils with sufficient vegetation for foraging (Burr, et al, 2012).
Figure 3: A gopher tortoise burrow at the Arboretum
The purpose of this paper:
About 10 burrows have been located in the Arboretum, six of which are marked
in figure 4. Of these six, two were found following JAG restoration efforts (zones 1 and
4, figure 2). Therefore it can be assumed that tortoises will recruit when habitat is made
more conducive to their requirements. This paper will determine where suitable tortoise
habitat exists within the Arboretum should
management decide to extend restorations on behalf
of the tortoise through GIS analysis and on-site
inspections of the Arboretum.
Lau (2011) studied how gopher tortoises in
beach dunes determine where to make their burrows
and the relative importance of the various factors
that influence site-selection. He observed fourteen
factors that could be grouped into three categories
that tortoises use in determining burrow sites (Lau,
2011).
Figure 4: Locations of known burrows
at the Arboretum

5. Environmental Factors Biological Factors Anthropogenic Factors
Soil Resistance Percent Canopy Cover Distance to Roads
Elevation Percent Herbaceous Cover Distance to beach access
Slope Percent Bare Ground
Slope Angle Percent Grass Cover
Soil Type Percent Scrub and Vine Cover
Percent Litter Cover
Distance to a Habitat's Edge
Land Cover Type
Number of Existing Tortoise Burrows
Table 1: Factors in Gopher Tortoise site-selection studied by Lau
Land cover and habitat-edge distance exerted the greatest influence on habitat
choice. Elevation and slope were also possible factors since tides risk flooding the
burrows. The number of active burrows was difficult for Lau to determine since
individuals often dig several burrows (Lau, 2011).
The GIS analysis for this project is based on several Lau's factors: land cover, soil
density, and distance-to-edge. The percentage of canopy cove, herbaceous cover, and
similar factors are regarded as components of land cover for the purposes of this research.
Slope and elevation were not considered since the Arboretum is far from the beach and
not subject to tidal flooding. In addition, the Arboretum's burrows have been found both
on both slopes and flatland and at a variety of elevations. The number of burrows is not
analyzed due to the low number of burrows and likelihood that several were made by the
same tortoise. Finally, distance to roads as a factor is not considered since automotive
traffic is a non-issue within the Arboretum.
METHODS
General
Three maps were created to analyze the Arboretum's ground cover, soil density,
and distances from habitat-edges. Each was converted into a raster format and

6. reclassified along a 5-point scale based along Lau's guidelines as they were manifested in
the Arboretum. A category one is considered ideal habitat for the gopher tortoise and a
category five is considered completely inhospitable. The three reclassified maps were
then combined together and converted through a "Weighted Sum" function into a final
suitability map allowing each factor to have a different degree of influence on a final
suitability map.
Ground Cover
Lau found that habitat-selection among tortoises increase as ground cover
increases (Lau, 2011). This seems reasonable as such cover determines foraging success.
However this conclusion has limited applicability to this study since it was conducted in a
coastal, relatively open environment. Another study suggests a ceiling exists on the
amount vegetation that will be tolerated if species mobility becomes restricted. In 2012,
Earl McCoy and Katherine Basiotis published a paper studying tortoise habitat
preferences in the forests of Hillsborough County, Florida where thick stands of invasive
cogon grass were present (McCoy and Bastiosis, 2012). They found through their study
that "tortoises avoided the area where the [cogon grass] had formed a dense monoculture"
(McCoy and Bastiosis, 2012, p.815). This also seems reasonable since a creature is
unlikely to nest in such inaccessible areas. Both Lau and McCoy's findings were
therefore considered in developing the maps for this project since habitats at the
Arboretum range from areas with wide spaces to impassable thickets. When reclassifying
the habitat layers of the Arboretum's map, a category one was considered an area of wide
spaces and a category five was considered completely impassible. Areas for which no

7. trail existed in were also ranked as a category five (Table 5)
The original data for the Arboretum does not accurately depict this variability in
vegetation density. Figure 5, Map 1 displays the original data with each habitat selected
out and recolored. Each habitat is classified as a single polygon as though its
characteristics were uniform throughout the zone. Yet vegetation density and
composition, especially in the "deciduous forest" zone dominating the map is more
complex and varied. Thus the polygons had to be reconstructed to reflect the complexity
of its ecology. This necessitated groundtruthing the data by inspecting the property.
Hence, the habitat polygons were redrawn to more accurately reflect the variety of
vegetation density (Figure 5, Map 2). Common zones were therefore more accurately
grouped together when the map was reclassified (Figure 5, Map 3).