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SOUTHEASTERN NATURALIST
2014
13(3):572–586
Dispersal Behavior of Diamond-backed Terrapin
Post-hatchlings
Andrew T. Coleman1,4,*, Thane Wibbels1, Ken Marion1, Taylor Roberge1,
David Nelson2, and John Dindo3
Abstract - Post-emergence dispersal behavior of hatchling turtles has been investigated in
several species, and a variety of species-specific orientation patterns have been reported.
In the current study, we examined the orientation and dispersal behavior of hatchling,
post-hatchling, and yearling Malaclemys terrapin pileata (Mississippi Diamond-backed
Terrapin) by utilizing an orientation arena on two natural nesting beaches. Each age group
displayed strong orientation and dispersal towards high-marsh vegetation instead of open
water. The results suggest an innate behavior in young Diamond-backed Terrapins in which
they orient from open beach areas toward vegetated marsh areas. The results also stress
the importance of having healthy marsh habitat adjacent to nesting areas to provide critical
habitat for these vulnerable life-history stages of Diamond-backed Terrapins.
Introduction
Orientation behavior of hatchlings has been investigated in several turtle spe-
cies, most notably in sea turtles. Salmon et al. (1992, 1995) and Lohmann et al.
(1997) reviewed previous research on this topic and summarized that sea turtle
hatchlings primarily utilize visual cues to guide them from the nest to the open
water. Hatchlings collect these cues within their “cone of acceptance”, which is a
visual field with a wide horizontal angle and a narrow vertical angle. They display
orientation to the brightest direction, and due to the narrow vertical angle within
their “cone of acceptance”, the light closest to the horizon, which is usually moon-
light reflecting on the water, has the greatest influence. Additionally, hatchling sea
turtles tend to orient away from high silhouettes on the horizon, such as dunes or
vegetation bordering the beach (Lohmann et al. 1997, Salmon et al. 1992). Unfortu-
nately, artificial lighting that is located near the nesting beach can be brighter than
natural light, thus resulting in hatchlings orienting away from open water and trav-
elling inland (Salmon et al. 1995). More recent research has shown that olfactory
(Fuentes-Farias et al. 2011) and magnetic cues (Fuentes-Farias et al. 2011, Stapput
and Wiltschko 2005) in addition to visual cues are used by sea turtle hatchlings in
their movements to the water after emergence.
Orientation behavior of freshwater turtle hatchlings has been examined in a
variety of studies, but the results do not reveal a succinct pattern as with sea turtle
species. Anderson (1958) observed hatchlings of Apalone mutica Lesueur (Smooth
1Department of Biology, University of Alabama at Birmingham, Birmingham, AL 35294.
2Department of Biology, University of South Alabama, Mobile, AL 36688. 3Dauphin Island
Sea Lab, Dauphin Island, AL 36528. 4Current address - Institute for Marine Mammal Stud-
ies, Gulfport, MS 39503. *Corresponding author - acoleman@imms.org.
Manuscript Editor: John Placyk
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Softshell), Graptemys oculifera Baur (Ringed Map Turtle), and Graptemys pulchra
Baur (Alabama Map Turtle) display negative orientation to tall, dark forms, a strat-
egy similar to sea turtles. But although it was noted that hatchlings of these species
venture from their nests to the water after sunset, they do not utilize light reflected
off the water in their dispersal (Anderson 1958).

Standing et al. (1997) and McNeil et al. (2000) found that Emydoidea blandingii
Holbrook (Blanding’s Turtle) hatchlings from a population in Nova Scotia do not
seek water after emergence despite the seemingly strong selective pressures favor-
ing entering the water. Visual cues appear to be utilized by hatchlings even though
silhouettes of nearby vegetation along with slope and open horizon are not impor-
tant cues (Standing et al. 1997). The hatchlings’ movements showed some evidence
of “cover seeking” behavior (McNeil et al. 2000), and their movements were more
direct under vegetative cover (Standing et al. 1997). However, some hatchlings
exhibited a diverse array of orientation behaviors after emergence, which was pro-
posed as an adaptive “bet-hedging” strategy in which different responses to various
environmental stimuli in a dynamic habitat presumably better ensure higher overall
survival rates for the population (McNeil et al. 2000, Standing et al. 1997). Tuttle
and Carroll (2005) observed similar scattered dispersal in Glyptemys insculpta
LeConte (Wood Turtle) hatchlings, and they suggested that in addition to visual
cues, olfactory and auditory cues along with positive geotaxis appear to influence
hatchling orientation.

Pappas et al. (2009) studied a population of Blanding’s Turtles that nest a long
distance from their resident wetlands. The authors observed similar orientation be-
havior to that of Standing et al. (1997) and McNeil et al. (2000), with the majority
of Blanding’s hatchlings dispersing towards dark horizons, which correlate with
riparian habitats. However, they doubted the “bet-hedging” strategy because the
hatchlings migrating away from wetlands would most likely not be able to over-
come the increased risks of predation or desiccation. They noted that Blanding’s
hatchlings that initially oriented away from dark horizons modified their direction
when new environmental cues arose (Pappas et al. 2009).

In contrast to hatchling Blanding’s turtles, hatchlings of Chelydra serpentina L.
(Snapping Turtle) and Chrysemys picta belli Gray (Western Painted Turtle) orient
to open areas, mostly near open horizons (Congdon et al. 2011). The authors pos-
tulated that females of these species nest in close proximity to wetlands to reduce
the number of open horizons available to emerging hatchlings. This strategy could
help ensure that the nearest open horizon is associated with a neighboring wetland.
Furthermore, Congdon et al. (2011) argued that a common reproductive ecology
scenario for nesting freshwater turtle species is to nest close to water with hatchling
orientation toward nearby open horizons.

Several studies have investigated various factors that could affect survival prob-
abilities of freshwater turtle hatchlings upon emergence from nests. These factors
include body size (Janzen et al. 2000, Tucker 2000), nest-site characteristics (Kolbe
and Janzen 2001), water loss (Kolbe and Janzen 2002), and exposure to predation
(Janzen et al. 2007).
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We examined the orientation behavior of Malaclemys terrapin pileata Wied-
Neuwied (Mississippi Diamond-backed Terrapin; hereafter Terrapin) hatchlings,
post-hatchlings, and yearlings on two natural nesting beaches. Terrapins exclusive-
ly inhabit brackish water environments of salt marshes, bays, and estuaries along
the Atlantic and Gulf of Mexico coasts (Carr 1952). Although the ecology of adult
Terrapins has been carefully studied (mostly in Atlantic Coast populations [Ernst
and Lovich, 2009]), Seigel and Gibbons (1995) listed juvenile Terrapin ecology
as a topic that was lacking clear insight. Pilter (1985) reported observing juvenile
Terrapins under marsh vegetation, and Lovich et al. (1991) observed hatchlings
released in water swim directly to land and venture to tidal wrack located at the
high-tide line. Additionally, Butler et al. (2004) observed 160 out of 172 hatchlings’
discernible tracks leading directly to marsh vegetation. Thus, upper salt marsh
habitat may serve as a critical refuge in the life cycle of Terrapins. However, this
proposed dispersal to upper salt marsh habitats can be perilous. Numerous organ-
isms prey on Terrapin nests and hatchlings, including Procyon lotor L. (Raccoon;
Feinburg and Burke 2003, Muldoon and Burke 2012), Corvus ossifragus Wilson
(Fish Crow; Butler et al. 2004), Corvus brachyrhyncos Brehm (American Crow;
Butler et al. 2004), Ocypode quadrata Fabricius (Ghost Crab; Butler et al. 2004),
Rattus norvegicus Berkenhout (Norway Rat; Draud et al. 2004, Muldoon and Burke
2012), and even roots of Ammophila breviligulata Fernald (American Beachgrass;
Lazell and Auger 1981). To investigate potential dispersal cues in the current study,
Terrapins were able to choose between migrating to the open water in the bay or to-
ward salt marsh vegetation. Their choices were analyzed to evaluate the importance
of the surrounding environments to the post-emergence orientation of Terrapins.
Materials and Methods

The Alabama population of Terrapins has experienced a significant historical
decline (Coleman 2011, Nelson and Marion 2004), so a head-start program was
initiated to address unsustainable levels of nest predation (Coleman 2011). We
obtained Terrapin eggs from nesting females captured in pitfall traps on the nesting
beach surrounding Cedar Point Marsh. This site is located north of Dauphin Island
along the Gulf Coast of Alabama. We palpated captured females to determine if
they were gravid. If so, they were given a safe dose of oxytocin, which stimulates
egg laying as described by Ewert and Legler (1978). Terrapins display tempera-
ture-dependent sex determination (Roosenburg and Kelley 1996), and eggs were
incubated at a constant temperature of either 26 °C (male-producing temperature)
or 31 °C (female-producing temperature) in the animal facility located at the Uni-
versity of Alabama at Birmingham (UAB). The majority of eggs were incubated at
31 °C to increase the number of females in the population to theoretically quicken
the pace of recovery (Shaver and Wibbels 2007). UAB animal-facility rooms did
not have access to sunlight and were kept at 24–26 ºC. We separated eggs and
hatchlings by clutch and fed hatchlings daily to satiation. Obtaining these hatch-
lings provided opportunities to research various aspects of Terrapin biology, such
as this study; however, the main purpose of the project was the eventual release of
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the captive-reared Terrapins into Cedar Point Marsh after they had grown to ap-
proximately 200–300 g, usually at about one year of age.
We created open-orientation arenas on the nesting beach surrounding Cedar
Point Marsh (CPM) and on another nesting beach at Airport Marsh (AM), which is
located behind Dauphin Island, AL (Fig. 1). The nesting beach surrounding CPM
has a north–south orientation, whereas the AM nesting location runs east–west.
Given the narrow width of nesting beaches at CPM and AM, arenas had a diameter
of 6 m and consisted of 12 open “gates” delineated by short PVC pipes inserted into
the ground (Fig. 2). PVC pipes were evenly spaced around the circumference of the
circular arenas (at 30° intervals relative to the center) to mark the 12 “gates”. Gate 1
always faced Due North (0°). We performed orientation trials only at CPM in 2008,
at both CPM and AM in 2009, only at AM in 2010, and only at CPM in 2012.

It was not logistically possible to utilize naturally emergent hatchlings because
the shell-hash substrate of CPM beach made it unsuitable to predictably find in situ
nests. Terrapins were transported from UAB to the nesting beaches and held prior
to their trials in a cooler to prevent access to natural orientation cues (e.g., natural
light, olfaction, slope, open horizons). After their tests, the Terrapins were placed
back in the cooler and transported back to UAB.
We tested three age groups of Terrapins: hatchlings, post-hatchlings, and year-
lings. Hatchlings were classified as turtles within one week after pipping (Table 1).
We waited until the yolk sac of hatchlings had been absorbed within the plastron
before trialing. Post-hatchlings were classified as turtles that were between one
to eight weeks of age (McCauley and Bjorndal 1999). Yearlings were turtles that
hatched and were trialed the previous nesting season and were approximately one
year of age when retrialed. We tested Terrapins individually per trial and placed
them under an opaque releasing device in the center of the arena for two minutes be-
fore starting. An observer, in a cryptic location outside the arena, remotely removed
the releasing device via a string. The open arena allowed Terrapins to encounter
multiple potential orientation cues. Terrapins were allowed to crawl in the arena
for up to 10 minutes or until they travelled through one of the gates. We noted the
gate the Terrapin passed through, along with the time taken to exit the arena and
any notable orientation behavior. Trials were conducted between mid-morning to
mid-afternoon hours (0900–1600).
Table 1. Sample sizes of Diamond-backed Terrapin groups tested in orientation arena by location
and year.
Year
Location
Terrapin age group
n
2008
Cedar Point Marsh
Post-hatchlings
60
2009
Cedar Point Marsh
Post-hatchlings
55


Yearlings
23
2009
Airport Marsh
Post-hatchlings
4


Yearlings
23
2010
Airport Marsh
Post-hatchlings
41
2012
Cedar Point Marsh
Hatchlings
39
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Figure 1. Google Earth© image of orientation arenas location on nesting beach at Cedar
Point Marsh (top) and Airport Marsh (bottom). Arena drawn to scale, and due north and
scale are indicated.
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We performed chi-square goodness-of-fit analyses on each dataset to determine
if preference for orientation-arena gates was non-random among the test subjects.
We also performed Rayleigh z tests on each dataset to determine the uniformity
of and the mean direction of dispersal. First, we examined the overall orientation
behavior of Terrapins, regardless of age group, by year. Next, we examined if year-
lings that had been exposed to orientation cues at a previous year’s trial display
different dispersal than naïve hatchlings and post-hatchlings. Third, we investi-
gated any potential effects of incubation temperature on orientation and dispersal.
Incubation temperature has been found to influence turtle hatchling performance in
sea turtles (Burgess et al. 2006, Mickelson and Downie 2010) and freshwater turtles
(Booth et al. 2004, Freedberg et al. 2004). All analyses were separated by location.
For the incubation-temperature analysis, we only utilized the Terrapins’ initial
trial, so no yearlings were included; Airport Marsh results were also not analyzed
because of the low number of post-hatchlings incubated at 26 ºC that were initially
tested at this location. Finally, we performed a one-way ANOVA on the exit times
(i.e., time required to travel from the center of arena and pass through a gate) of
Terrapins separated by age groups and incubation temperature. We transformed the
exit-time data with natural logs to approximate normality. We completed all statisti-
cal analyses in Microsoft© Excel.
Figure 2. Diagram of open orientation arena used on both Cedar Point and Airport marshes.
The arena was composed of twelve “gates” that were delimited by PVC pipes positioned
evenly around the circumference of the arena at intervals of 30° angles relative to the center.
Gate 1 always faced due north (0°).
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Results
Overall orientation and dispersal behavior

In total, we performed 245 individual trials utilizing orientation arenas at CPM
and AM, and 208 trials resulted in hatchlings, post-hatchlings, and yearlings exiting
the arena in the allotted 10 min. Terrapins displayed a significant orientation prefer-
ence at CPM and dispersed in the direction of marsh vegetation (Fig. 3, Table 2).
The 2009 trials at AM indicated significant orientation preference and non-uniform
dispersal (Fig. 4), but the 2010 trials at AM did not. The mean angle for the 2009
trials was 199.1°, which was facing marsh vegetation. The average exit time for
Terrapins that made it out of the arena in under the allotted 10 min was 281.92 s ±
17.86 95% CI.
Effect of orientation experience

Experienced yearlings and naïve hatchlings and post-hatchlings displayed sig-
nificant orientation at CPM (Table 3). The dispersal of all three groups was in the
direction of marsh vegetation. At AM, neither group displayed a significant gate
preference. However, yearlings did display non-uniform dispersal toward marsh
vegetation. Significant differences were detected between age groups in the exit
Figure 3. Results from 2008 trials examining orientation behavior of Diamond-backed
Terrapin post-hatchlings on a natural nesting beach surrounding Cedar Point Marsh. Seven
post-hatchlings of the 60 released did not exit the arena in the allotted 10 minutes. Post-
hatchlings showed a significant preference for gates facing marsh vegetation (χ2 = 162.20, df
= 11, P < 0.001). Their dispersal was not uniformly distributed (Rayleigh’s z41.75, P < 0.001),
and the mean angle was 50.78° as denoted by the arrow.
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times (F = 46.26; df = 2,155; P < 0.0001) at CPM. Yearlings (mean = 118.42 s ±
24.82 95% CI) displayed the fastest exit times, followed by post-hatchlings (mean
= 306.72 s ± 24.09 95% CI) and hatchlings (mean = 332.43 s ± 38.42 95% CI). Sig-
nificant differences (F = 12.95, df = 1,45, P = 0.0008) were also detected between
yearlings (mean = 185.58 s ± 43.73 95% CI) and post-hatchlings (mean = 299.20 s
± 41.02 95% CI) at AM.
Effect of incubation temperature
We detected no differences in orientation between Terrapins incubated at 26 °C
and 31 °C at CPM (Table 4). Both groups displayed significant dispersal toward
Table 2. Results of chi-square goodness-of-fit analyses examining dispersal preferences of Diamond-
backed Terrapins as well as results of Rayleigh’s z analyses examining the uniformity of dispersal and
mean angle of direction. Each chi-square analysis had 11 degrees of freedom. Asterisk denotes levels
of significance at α level of 0.05.









Mean
Year
Location
n
χ2
χ20.05,11
P
z
z0.05,n
P
angle (°)
2008 Cedar Point Marsh
53 162.20* 19.68 <0.001
41.75* 2.982 < 0.001
50.78
2009 Cedar Point Marsh
70 265.81* 19.68 <0.001
53.58* 2.985 < 0.001
53.77
2009 Airport Marsh
21
20.71* 19.68 <0.05
8.65* 2.960 <0.001
199.10
2010 Airport Marsh
28
17.45 19.68 >0.05
1.49 2.969 >0.05
107.37
2012 Cedar Point Marsh
36
57.33* 19.68 <0.001
12.65* 2.975 <0.001
18.67
Figure 4. Results from 2009 trials examining orientation behavior of Diamond-backed Ter-
rapin post-hatchlings and yearlings on a natural nesting beach surrounding Airport Marsh.
Six individuals of the 27 released did not leave the orientation arena in the allotted 10 min.
A significant preference for exiting gates facing marsh vegetation was observed (χ2 = 20.71,
df = 11, P < 0.05). Their dispersal was not uniformly distributed (Rayleigh’s z8.65, P <
0.001), and the mean angle was 199.1° as denoted by the arrow.
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marsh vegetation. We also observed no significant difference in exit times (F =
0.22, df = 1,137, P = 0.64) between the incubation temperature groups at CPM.
Terrapins incubated at 26 ºC displayed slightly faster exit times (mean = 309.04 s
± 36.24 95% CI) than those incubated at 31 ºC (mean = 315.46 s ± 24.84 95% CI).
Orientation behaviors
We observed certain orientation behaviors among the age groups throughout
the study. Terrapins would extend their heads and would often turn their bodies in
a complete circle before making any directional movements. Once movement was
initiated, it was often intermittent, with individuals periodically stopping to perform
another “orientation circle” with heads extended before continuing with their move-
ments. Finally, of the 37 trials in which Terrapins did not exit the arena in the allotted
time, 20 of these trials resulted in individuals burying themselves into the beach sub-
strate instead of dispersing.
Discussion

This study is the first to utilize a constructed arena on a natural nesting beach
to quantitatively assess dispersal preferences of Diamond-backed Terrapins. Ter-
rapins showed significant preference for dispersing toward marsh vegetation rather
than open water. This result is in stark contrast to the orientation preferences of
sea turtles, which rely on visual cues (Lohmann et al. 1997; Salmon et al. 1992,
1995) along with possible olfactory and magnetic cues (Fuentes-Farias et al. 2011)
to orient away from dark silhouettes and toward open horizons of the sea. It was
Table 4. Results of chi-square goodness-of-fit and Rayleigh’s z analyses comparing dispersal behavior
between post-hatchlings incubated at 26 °C and post-hatchlings incubated at 31 °C on the natural nest-
ing beach surrounding Cedar Point Marsh. Asterisks denote levels of significance at α level of 0.05.
Temperature
n
χ2
χ20.05,11
P
z
z0.05,n
P Mean angle (°)
26 °C
49
93.36*
19.68
<0.0001
29.74
2.981
<0.001
31.06
31 °C
105 264.83*
19.68
<0.0001
57.37
2.988
<0.001
41.96
Table 3. Results of chi-square goodness-of-fit and Rayleigh’s z analyses comparing dispersal behavior
among yearlings, naïve post-hatchlings, and hatchlings on the natural nesting beach surrounding Ce-
dar Point Marsh and between yearlings and naïve post-hatchlings at Airport Marsh. Asterisks denote
levels of significance at α level of 0.05.









Mean
Location/exposure
n
χ2
χ20.05,11
P
z
z0.05,n
P
angle (°)
Cedar Point Marsh

Yearlings
19
79.06* 19.68 < 0.001
16.97*
2.956
<0.001 41.80

Post-hatchlings
104 317.39* 19.68 < 0.001
78.14*
2.988
<0.001 42.73

Hatchlings
36
57.33*
19.68 < 0.001
12.65*
2.975
<0.001 18.67
Airport Marsh

Yearlings
19
17.04
19.68 >0.05
6.94*
2.956
<0.001 200.66

Post-hatchlings
30
16.4
19.68 >0.05
1.64
2.971
>0.05
118.45
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also different from other freshwater turtle species that were documented to disperse
away from dark silhouettes (Anderson 1958) or toward open horizons (Congdon et
al. 2011). Congdon et al. (2011) hypothesized that, for freshwater turtles, the most
common strategy is for females to nest near water and hatchlings to orient toward
the nearest open horizon.
As stated above, this tendency was not observed with the Alabama population of
Diamond-backed Terrapins examined in this study. Terrapins displayed a significant
preference for orienting toward marsh vegetation instead of open water. Hatchling
Blanding’s Turtles also disperse toward dark horizons, which are associated with
riparian habitats (Pappas et al. 2009), but these hatchlings traveled much farther to
reach their desired wetlands (average distance 589 m; Congdon et al. 2011) than
Terrapins do to reach high marsh vegetation at our sites. Similar to other turtle
species, visual cues seemed to be the primary cues used by Terrapins in their move-
ments. They would often perform “orientation circles” with extended heads before
moving directionally, thus consistent with the hypothesis that they were scanning
the entire field of view for visual orientation cues.

Burger (1976) observed similar behavior with Terrapin hatchlings raising their
heads and looking around. In her study, hatchlings emerged between 0700 and
1900, with most between 1200 and 1700. When the hatchlings emerged from nests
on flat areas, tracks were observed in random directions; however, they crawled
down the gradient from nests laid on slopes (Burger 1976). Results indicated that
hatchlings would move down inclines in different compass orientations, although
individuals chose moving to vegetation regardless of incline (Burger 1976).
Visual cues were suggested to be vital for hatchling orientation in Kinosternon
flavescens Agassiz (Yellow Mud Turtles; Iverson et al. 2009) and Wood Turtles
(Tuttle and Carroll 2005), as they have been for Blanding’s Turtles (Pappas et
al. 2009, 2013), Western Painted Turtles (Congdon et al. 2011), and Snapping
Turtles (Congdon et al. 2011, Pappas et al. 2013). After displacement from their
normal post-emergence migration to wetlands, Yellow Mud Turtle hatchlings non-
randomly re-oriented toward the direction of the wetland destination. The authors
suggested that reflected light intensity may have been a major visual cue for the
hatchlings (Iverson et al. 2009); however, Congdon et al. (2011) suggested that
positive geotaxis or open-horizon orientation were more probable cues for the turtle
hatchlings in their study. Wood Turtle hatchlings exhibited saltatory searches with
“stop and go” movements (Tuttle and Carroll 2005). Similar saltatory movements
were observed frequently in the current study.
Other cues could have influenced the Terrapin movements in our study. The
arenas were constructed in relatively flat areas, so the influence of positive geotaxis
was not examined in this study. As observed by Burger (1976), compass direction
did not affect hatchling migration in the current study. The arena at CPM had a N–S
orientation, whereas the arena at AM had a E–W orientation. However, the results
obtained from AM were not as clear as those from CPM. A greater diversity in the
location of vegetation surrounding the AM arena may have confounded the orienta-
tion behavior given the strong preference for beach vegetation observed by Burger
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(1976). In contrast, the orientation arena we used at CPM was on a beach with very
sparse vegetation due to overwashing from several tropical storms and hurricanes
during recent years.

Iverson et al. (2009) detected evidence for compass orientation in Yellow Mud
Turtle yearlings. Displaced yearlings non-randomly re-oriented in the same direc-
tion as they were traveling when captured. Although the mechanism for setting the
compass could not be concluded, the authors hypothesized that the compass for
hatchlings was set in their initial wetland migration (Iverson et al. 2009). Pappas
et al. (2009) suggested a sun compass was utilized by displaced experienced hatch-
lings that persisted on their initial direction even if it was in the opposite direction
of their desired target. We did not detect any influence of experience on orientation
direction at CPM, with all age groups distinctly choosing marsh vegetation. Olfac-
tory and auditory cues could also have influence on Wood Turtle hatchlings (Tuttle
and Carroll 2005). Neither of these possibilities was explored in the present study,
but it could be argued that the relatively small distance that Terrapin hatchlings dis-
perse after emergence compared to other turtle species, such as Blanding’s Turtles,
may not require the use of multiple cues.

It should not be surprising that the Terrapin burying behavior was observed. Ter-
rapins emerge during daylight hours, with the highest emergence occurring during the
hottest portion of the day (Burger 1976). Desiccation has been shown to be a powerful
influence on turtle hatchling migrations (Kolbe and Janzen 2002). Dead hatchlings
that apparently succumbed to overheating have been found at CPM (A.T. Coleman,
UAB, Birmingham, AL, pers. observ.). Thus, burying themselves into the substrate
appears to be an alternative strategy to direct movement to marsh vegetation. We did
not wait to investigate whether Terrapins that buried themselves later completed their
migration when ambient temperatures decreased. However, this strategy could in-
crease their chances of falling prey to nocturnal predators.
Although it was not logistically possible to utilize naturally emergent hatch-
lings, we do not expect our results to significantly deviate from that of naturally
emerging hatchlings. First, previous studies with hatchling Terrapins have revealed
similar orientation behaviors and dispersal (Burger 1976, Lovich et al. 1991, Mul-
doon and Burke 2012). Second, hatchlings and post-hatchlings used in the current
study had not been exposed to any natural orientation cues associated with a nest-
ing beach prior to their experimental trials. And as stated above, each age group
(hatchling, post-hatchling, and yearling) displayed significant orientation towards
marsh vegetation. However, the negative relationship between age and exit times
indicated that size could influence movement rates and thus migration success in
Terrapin hatchlings, which has been observed in other species (Janzen et al. 2000).
Similar to experience, incubation temperature did not appear to affect Terrapin
orientation, although incubation temperature has been shown to influence post-
hatchling growth (Roosenburg and Kelley 1996).

The current findings highlight how a turtle’s ecology and nesting environment
may influence the evolution of orientation mechanisms. The widths of the nesting
beaches at CPM and AM, which are adjacent to marsh habitats, are approximately
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10–15 m, similar to other Terrapin nesting sites in Florida (Butler et al. 2004), Mary-
land (Roosenburg et al. 2003), and New York (Draud et al. 2004). However, Terrapins
in a Rhode Island population travelled much farther to nest (>500 m; Goodwin 1994).
Therefore, different populations of Terrapins may display different dispersal behav-
iors or rely on different cues based on their unique ecology and nesting environments.
For instance, in a population of Terrapins inhabiting Jamaica Bay, NY, a lower pro-
portion of hatchlings was found to disperse to upland marsh habitats than would be
expected based on our results (even though the majority [55–64%] of captured hatch-
lings were moving in the direction of marsh habitats; Muldoon and Burke 2012). A
study in Jamaica Bay designed similar to ours would provide further insight to the
cues used by Terrapin hatchlings from this New York population.
Overall, our results revealed a very robust and innate orientation toward marsh
vegetation in Terrapin hatchlings, post-hatchlings, and yearlings, and they agree
with other published observations (Butler et al. 2004, Pilter 1985) and studies
(Burger 1976, Draud et al. 2004, Lovich et al. 1991) concerning Terrapin habitat use
post-emergence. The results of the current study also stress the importance of ample
higher marsh habitat with associated tidal wrack and debris adjacent to Terrapin
nesting beaches. This habitat could provide the necessary refuge and resources to
individuals of this vulnerable life-history stage (Lovich et al. 1991, Muldoon and
Burke 2012, Pilter 1985). Therefore, the presence of these habitats is critical for
the success of hatchling survival and eventual recruitment into the adult popula-
tion. Unfortunately, loss of marsh habitat is rampant throughout coastal ecosystems
(Bertness et al. 2004), and this loss represents a major threat to the future viability
of Diamond-backed Terrapin populations (Butler et al. 2006, Roosenburg 1991).
Acknowledgments

This project had approval from University of Alabama at Birmingham’s Institution for
Animal Care and Use Committee under APN# 110309342. Funding for this project was
provided for the Alabama Center for Estuarine Studies, the Alabama Department for Con-
servation and Natural Resources through a State Wildlife Grant, and UAB’s Department of
Biology. Logistical support was provided by UAB’s Department of Biology and Dauphin
Island Sea Lab. Numerous UAB undergraduate students in the Wibbels’ lab supplied great
care to the Terrapin hatchlings. J. Pitchford and two anonymous reviewers provided a much-
appreciated review of the manuscript.
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