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Herpetological Review 50(4), 2019
ARTICLES 695
Herpetological Review, 2019, 50(4), 695–698.
© 2019 by Society for the Study of Amphibians and Reptiles
Spatial Ecology of the Striped Mud Turtle,
Kinosternon baurii, in a Restored Florida Wetland
For many turtle species, adequate background data to formulate
useful conservation, restoration, and management plans are
lacking (Ernst et al. 1994; Ernst and Lovich 2009). The knowledge
gap should be filled for understudied turtles, primarily because
recent unforeseen population declines suggest that predicting
population decline is difficult, even for relatively well-studied
turtles (Gibbons et al. 2000; Christiansen et al. 2012; Lovich et al.
2018). Information on how organisms use space is an essential
part of understanding their ecology (Gibbons 1970; Gregory et al.
2001; Slavenko et al. 2016). Movement data can provide insight
into the actual space needed to support species by displaying
where individuals use their time (Gibbons 1970; Wygoda
1979; Harden et al. 2009). This information can be valuable to
land managers and conservation biologists when planning
restoration and conservation projects or providing insight into
turtle declines (Harden et al. 2009; Dudley et al. 2015; Marchand
and Litvaitis 2004).
The Striped Mud Turtle, Kinosternon baurii, is a small
understudied semi-aquatic turtle that resides along the Atlantic
and Gulf Coastal Plains of the eastern United States from Virginia
to the Florida Keys (Ernst et al. 1994; Wilson et al. 2006). The
studies on K. baurii in Florida have been conducted in west-
central Florida (Wygoda 1979; Mushinsky and Wilson 1992;
Wilson et al. 1999), south Florida (Ernst et al. 1972; Meshaka and
Blind 2001), and the Florida Keys (Dunson 1981), but no previous
studies have taken place in central Florida.
Wygoda (1979) used thread bobbins to study K. baurii
movement and found they spend a significant amount of time on
land when aquatic areas desiccate. He concluded that terrestrial
movement of K. baurii was bimodal and correlated with water
depth, precipitation, and temperature. No studies have utilized
radiotracking to examine the movement of this mud turtle
species.
The major threat to Kinosternon in Florida is the loss of
suitable habitat because they require wetlands surrounded
by uplands they use for nesting (Wilson et al. 2006; Cordero
et al. 2012). Hence, they are an ideal species to demonstrate
how conserving wetlands, but not the land around them, is
insufficient for some species (Buhlmann and Gibbons 2001;
Bowne et al. 2006). These habitat requirements are also observed
in Kinosternon subrubrum and Kinosternon integrum (Harden et
al. 2009; Cordero et al. 2012; Pérez–Pérez et al. 2017).
Despite their wide distribution, Striped Mud Turtles
have not been studied in restored habitats and do not have
radiotelemetry-based home range data available. Therefore, we
initiated a study in central Florida to fill knowledge gaps on the
spatial ecology of K. baurii in a restored environment. The study
contributes to an improved understanding about how K. baurii
move in a reestablished area and provides insight for future
management plans.
MaTerials and MeThods
Study site.—Our study area was Circle B Bar Reserve (CBR),
a restored former cattle ranch adjacent to Lake Hancock in Polk
County, Florida, USA. The reserve consists of 512.7 ha of land,
which includes permanent marsh, semi-permanent wetlands,
and upland habitat (Fig. 1). The wetland habitat where we
captured most turtles (all except one) is a canal, Alligator Alley,
that runs parallel to Lake Hancock approximately 2 km away
from upland habitat. On the other side of the canal is a semi-
permanent wetland. Areas of the marsh and wetlands dried up
during the dry season (October–May), but frequently flooded
during June–September. From October 2016 to June 2017 there
was a drought in the area and a majority of the wetlands and
canals that are ordinarily permanent dried up.
Radiotelemetry.—We tagged nine turtles with ATS
radiotelemetry tags (3.5 g) starting in Sept 2016. We caught
turtles using box-style minnow traps, dimensions 39 x 36 x 29
cm, with metal mesh that was 1 x l cm (similar to Karl and Wilson
2001). Most turtles caught were female, so we actively searched
for males to tag. The tag’s mass did not exceed 5 % of the turtle’s
body mass because we affixed transmitters only to turtles > 70
g, as measured with a Pesola scale. We attached the tags with
marine epoxy (Loctite® Marine 2-hour Epoxy, Henkel Corp.,
Westlake, Ohio, USA) to costal scutes, on the anterior portion
of the turtle on the right side of the carapace, with the antenna
facing backwards and up. To minimize stress for the turtle, we
LEYNA R. STEMLE*
e-mail: leynastemle@hotmail.com
KRISTEN M. MARTINET
e-mail: kmartinet@outlook.com
GABRIEL J. LANGFORD
Department of Biology, Florida Southern College,
111 Lake Hollingsworth Drive, Lakeland, Florida 33801, USA
e-mail: glangford@southern.edu
*Corresponding author
Fig. 1. Map of Circle B Bar Reserve and its location within Florida.
The habitats where the turtles were caught are highlighted in green
and marked with green stars. Alligator Alley is the location where 8 of
the 9 turtles were caught.
Herpetological Review 50(4), 2019
696 ARTICLES
contained them for < 3 days during the tagging process. We affixed
nine turtles with transmitters, seven females and two males,
with one turtle having the first tag replaced when the transmitter
battery malfunctioned, for a total of 10 transmitters. We located
the nine turtles one to three times every week (less during winter
months) and took a GPS point. When visual confirmation of a
turtle’s location was not feasible, we triangulated a bearing and
approximated the location. We estimated location by using the
geofunction library of Microsoft Excel and the NewPostLat/
NewPostLong equation. We continued tracking until the end
of the battery life, approximately 260 days, or until we could
not obtain the signal. If the signal vanished, we searched for
it in numerous locations at least once every three weeks until
the end of the study. We entered the GPS points into ArcGIS
Explorer version 10.1 (ESRI 2012) to view the movements and
home ranges of each turtle. To estimate home range, we used the
polygon and then area feature of ArcGIS. This involved including
all the outermost GPS points as the edge of the home range and
then recording the area of the formed polygon.
Statistical analysis.—We took the area of each home range
and obtained the means and standard deviation (SD) for all
turtles and by sex. We measured straight-line distance (SLD) to
show the greatest distance between two GPS locations within
the home range and calculated the mean and SD of the SLD. We
performed a Mann-Whitney U-test to compare male and female
home range sizes. We used MiniTab -18 and Microsoft Excel for
statistical analyses (α = 0.05).
resulTs
Home ranges.—We tracked turtles between 66 and 369 days
(mean̅ = 174 ± 97.9; N = 9; Table 1). Home range polygons are
shown in Figs. 2 and 3. A male turtle had the largest home range
(14,396 m2) and SLD (281 m; Table 1). The other male turtle had
the smallest home range, 1111.2 m2. The second largest home
range was a female who was gravid during the last segment
of the tracking period (9200 m2). The mean SLD for the turtles
was 169.3 m and went through mostly shallow, lentic wetlands
and canals, with the occasional trail or road. We confirmed two
females to be gravid during their tracking period (frequencies
209 and 131; Table 1). Females had a mean home range of 5079.0
m2 ± 2274.0 (N = 7) and males had a mean home range of 7753.4
m2 ± 9393 (N = 2). The mean home range difference between the
sexes was not statistically significant (P = 0.76; N = 9).
Movement patterns.—During a drought in 2017, three
tracked turtles were together in a very shallow pool of water,
which was once the canal, for a few days. One turtle retreated
to the nearby lake, which had abundant water, when its normal
pool dried. After tracking her twice in the lake, her signal was lost
and not located after extensive searching. A male estivated when
the water in his home range disappeared. Nesting activities
continued during the drought, as a gravid female was found
while crossing a road. She became sedentary after laying her
eggs near the roadway. Unfortunately, we lost her signal soon
after her nesting event.
discussion
Our study is the first to investigate K. baurii movement with
radiotelemetry and provides the first accurate home ranges for
Striped Mud Turtles. Overall, the mud turtles in our study moved
a considerable amount and their home range sizes fell near the
middle of the variability found for other species of Kinosternidae
(Harden et al. 2009; Cordero et al. 2012; Pérez–Pérez et al. 2017).
The lowest reported mean home range found in Kinosternidae
was 80 m2 for Sternotherus depressus and the upper extreme was
657,000 m2 for Sternotherus odoratus (Dodd et al. 1988; Bennett et
al. 2015). In comparison to other freshwater turtles, kinosternids
have relatively small home ranges (Slavenko et al. 2016).
Table 1. Frequency, sex, home range, straight-line distance, days radio tracked, and number of relocation
points.
Turtle Sex Home range Straight-line Number of Total relocation
frequency area (m2) distance (m) days tracked points
209 F 9200 247 369 66
171, 151 F 5791 154 245 50
310 M 1111 170 230 31
131 F 5184 175 120 16
110 M 14,396 283 152 31
250 F 3146 88 203 31
228 F 2083 123 110 18
290 F 4435 218 66 11
191 F 5716 67 72 16
Fig. 2. Home range polygons of the two male turtles, frequencies 310
and 110, mapped together to show overlap.
Herpetological Review 50(4), 2019
ARTICLES 697
Home ranges.—On average, female home ranges were smaller
than male home ranges, but the difference was not statistically
significant, which could have been impacted by the small
sample size (N = 9). Sex-specific differences in home range are
seen in K. subrubrum, so this difference might be observed with
a larger sample size of K. baurii (Cordero et al. 2012). Although
we only confirmed two gravid females, both appeared to move
outside their standard home range to nest, which is consistent
with reports that nesting forays can expand a turtle’s home range
(Stickel 1989; Cook 2004). A male had the largest home range,
but the second largest was a gravid female. Interestingly, the two
male home ranges barely overlapped, while many female ranges
overlapped extensively (Figs. 2 and 3). Male K. baurii can be
aggressive to each other, as observed in the field by Carr (1952)
and Lardie (1975) as well as in captivity (Wygoda 1979). Females
may be able to tolerate overlap in ranges, whereas males may
be pushed out of established territories of other males. Wygoda
(1979) also questioned whether males are territorial or have
dominance hierarchies, but further investigation is needed to
determine if male avoidance is commonplace and caused by
underlying male behavior.
Movement patterns.—The mean SLD for the turtles in this
study was 169.3 m, which was slightly larger than what is observed
in Eastern Mud Turtles in suburban environments (mean = 119.2
m; Harden et al. 2009). However, this SLD is considerably smaller
than what Cordero et al. (2012) found for K. subrubrum in the mid-
Atlantic region of the United States (mean maximum distance
traveled 903 and 887 m). Additionally, these movements are more
substantial than represented in K. integrum (mean distance =
51.44 m; Pérez–Pérez et al. 2017). The variability of the movement
in the three species that have similar habitat requirements is
peculiar. However, Wilson et al. (1999) found that the average
movement for K. baurii from wetland to nest site was 137 m,
which was comparable to our overall SLD found during tracking.
Through the drought in 2017, tracked turtles exhibited
interesting behaviors. As we tracked one female’s signal, it was
lost when she moved from the shallow wetland to the adjacent
lake. After her movement into Lake Hancock, we lost her signal,
which may indicate that she travelled a substantial distance to
establish a new home range (we made extensive efforts to locate
her). Alternatively, she may have been depredated. During
the drought, a male turtle (frequency 310) estivated when his
wetland in his home range dried, which suggests turtles in this
population respond differently to drying ponds, i.e., estivation
vs. relocation. Given his extended period of inactivity, it seems
estivation likely contributed to his relatively small home range.
Wygoda (1979) found that many K. baurii in west-central Florida
estivated, whereas Ernst et al. (1972) found that in southern
Florida they did not estivate because the water was permanent.
The apparent variation in estivation behavior is interesting
but perhaps attributed to the morphometric evidence found
by Iverson (1978) indicating a cline in mud turtle aquatic
specialization throughout varying geography within Florida.
However, our study supports the findings by Wygoda (1979) that
K. baurii have seasonal shifts in movement that are related to
water depth, precipitation, and temperature.
One gravid female’s signal was lost 66 days after she was
tagged. Just before her signal was lost, she was buried while
resting after depositing her eggs, similar to what was seen by
Wilson et al. (1999). It is not known whether she disappeared
due to depredation, tag malfunction, or a long foray. However,
increased vulnerability of nesting females has been observed in
other turtle species and conservation planning should assess this
threat to increase survival rates (Aresco 2005; Iglay et al. 2007).
When tracked turtle 209 was gravid, she stayed near the
sandy levee trail, presumably to nest, during fall 2018, behavior
which also has been observed in K. subrubrum (Cordero et
al. 2012). The trail is the primary elevated area apart from the
upland habitat (approximately two km) from the study site; thus,
given the distance to the natural upland habitat, the levee trail is
the only confirmed nesting area and is presumed to be the main
nesting area for these turtles. It seems possible that the man-
made levee serves as an ecological trap for these turtles (see
Aresco 2005), as egg predators seem to be drawn to the trail by
human activity. Because current nesting habitat is limited and
might reduce egg and hatchling survival, managers of restored
areas may consider constructing additional nesting habitat
closer to the mud turtle home ranges to bolster recruitment
(Reid et al. 2016). If anthropogenically altered areas are to be
managed for both people and fauna, such as these levee trails,
land managers should reflect upon the behavioral patterns and
spatial ecology of wildlife (Bowne et al. 2006; Harden et al. 2009).
Our data show many home ranges encompassing large
portions of land, reinforcing the evidence that K. baurii is a
highly terrestrial species. Setting aside or restoring uplands that
are close to wetlands would benefit numerous species and would
help to conserve wildlife that depend on land and water within
fragmented and disturbed habitats (Williams and Dodd 1978;
Bowne et al. 2006; Harden et al. 2009; Reid et al. 2016). We suggest
future studies on K. baurii nesting and terrestrial movement,
especially in restored areas, to provide a more comprehensive
picture of what they require (see Slavenko et al. 2016).
In increasingly human-dominated landscapes, which are
progressively more common in Florida, restored habitats and
reserves will serve as critical habitat for turtles and other wildlife.
As even “wild” habitats in Florida become gradually more
disturbed, knowledge of mud turtle movement, as well as how
they respond to perturbed habitats, will be key to establishing
comprehensive management plans.
Acknowledgments.—The support of the Circle B Bar Reserve
staff, especially Tabitha Biehl, as well as volunteer Allen Ayris and
the Florida Southern College Department of Biology and Honors
Program, allowed this project to happen. Thanks to Bryanna Wargat
and Joshua Lew for help with fieldwork. This research was approved
by Florida Southern College Institutional Animal Care and Use Com-
mittee protocol #1020 and capturing was done under a Polk County
Environmental Lands Special Use Permit for 2016 and 2017.
Fig. 3. Home range polygons of the seven female turtles, mapped to-
gether to show overlap.
Herpetological Review 50(4), 2019
698 ARTICLES
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