Nest-Site Characteristics of Glyptemys muhlenbergii (Bog
Turtle) in New Jersey and Pennsylvania
Robert T. Zappalorti, Jeffrey E. Lovich, Ray F. Farrell, and Michael E. Torocco
Northeastern Naturalist, Volume 22, Issue 3 (2015): 573–584
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2015
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2015 NORTHEASTERN NATURALIST 22(3):573–584
Nest-Site Characteristics of Glyptemys muhlenbergii (Bog
Turtle) in New Jersey and Pennsylvania
Robert T. Zappalorti1,*, Jeffrey E. Lovich2, Ray F. Farrell1, and Michael E. Torocco1
Abstract - Nest-site selection can affect both the survival and fitness of female turtles and
their offspring. In many turtle species, the nest environment determines the thermal regime
during incubation, length of incubation period, sex ratio of the hatchlings, and exposure to
predators and other forms of mortality for both mothers and their offspring. Between 1974
and 2012, we collected detailed data on habitat variables at 66 Glyptemys muhlenbergii
(Bog Turtle) nests in 9 different bogs, fens, and wetland complexes in New Jersey and
Pennsylvania. The nests had a mean elevation above the substrate of 8.2 cm, and many were
shallow and located in raised tussocks of grass or sedges. Females covered most nests, but
we also observed partially or completely uncovered eggs. Some females deposited eggs in
communal nests; we found 4 nests with 2 separate clutches, and 2 nests with 3 clutches.
Principal component analysis confirmed the importance of cover and vegetation to nest-site
selection in this species. Availability of open, shade-free, wet nesting areas is an important
habitat requirement for Bog Turtles.
Introduction
Selection of a nest site has important fitness consequences for mothers and
offspring of oviparous organisms, as recently reviewed for turtles by Lovich et al.
(2015). Female aquatic turtles are at risk because of their exposure to predators
when they leave the comparative safety of their wetland environment to nest (e.g.,
Steen et al. 2006). In addition, because most turtle species do not exhibit parental
care (but see Agha et al. 2013), their offspring are left to fend for themselves in
the post-ovipositional nest environment where nest predation can be extremely
high and variable (Congdon et al. 1994)—up to 100% in some years and species
(Ernst and Lovich 2009). The post-ovipositional environment has the potential to
affect a number of key aspects of the life history of turtles: developmental rate
and duration; hatchling-turtle sex ratios; and phenotype, growth rate, and survival
of hatchlings as reviewed by Wilson (1998) and Lovich et al. (2012). As a result,
it is expected that nesting turtles would select egg-deposition sites that provide
appropriate environmental conditions for hatching success (e.g., solar/thermal exposure
and soil-moisture conditions), including protection of eggs and developing
embryos from predators (Pignati et al. 2013).
Although most gravid female freshwater-turtles migrate away from their aquatic
habitat to locate traditional upland nest sites (Ernst and Lovich 2009), there are
1Herpetological Associates, Inc., Plant and Wildlife Consultants, 575 Toms River Road,
Jackson, NJ 08527. 2US Geological Survey, Southwest Biological Science Center,
2255 North Gemini Drive, MS-9394, Flagstaff, AZ 86001. *Corresponding author -
RZappalort@aol.com.
Manuscript Editor: Todd Rimkus
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some species with nesting behaviors that differ substantially from the norm in
that they nest within the confines of their wetland habitat. In Australia, Chelodina
rugosa Werner (Siebenrock’s Snake-necked Turtle) actually lays eggs underwater
(Kennett et al. 1993). In eastern North America, Glyptemys muhlenbergii (Schoepff)
(Bog Turtle) remains in its wetland and often selects slightly elevated sites (as opposed
to subterranean nests), generally on raised clumps of sedges called tussocks
(pedestal-forming vegetation), for nesting within characteristic marshy habitat
(Zappalorti 1976a, b). Bog Turtle nesting areas typically have limited canopy closure,
support an array of moisture-tolerant plants, and provide ample solar exposure
(Ernst and Lovich 2009). The practice of nesting within their wetland habitat may
reduce predation risk that might occur in nesting forays to uplands and reduce competition
for nest sites used by other turtle species. Bog Turtles are sympatric with as
many as 5 aquatic-turtle species in parts of their range (Lovic h et al. 2014).
With the exception of unpublished research by Whitlock (2002), few studies have
focused on the environmental attributes of Bog Turtle nests in the wild. Information
on the species’ natural history is needed to guide effective conservation for the
recovery of this federally threatened turtle (Lovich and Ennen 2013). In this study,
we examined the physical characteristics of nests and proximate-habitat characteristics
of nest sites selected by Bog Turtles. We conducted our research episodically
between 1974 and 2012 at 9 different bogs, fens, and wetland complexes in New
Jersey and Pennsylvania (Table 1). In the absence of similar data for sites without
nests, we were unable to specifically address nest-site selection relative to available
microhabitats. However, our data allow a quantitative assessment of environmental
attributes associated with nest sites used by Bog Turtles in the mid-Atlantic region.
Field-Site Description
All of our study areas were wetland marshes, bogs, or fens with soils (Feaga et
al. 2013), hydrology (Feaga 2010), and vegetation (Chase et al. 1989, Zappalorti
1997) typical of Bog Turtle habitat (USFWS 1997, 2001). To protect this popular
and imperiled turtle species from exploitation, we do not provide exact localities
and specific place names of research areas. Our 9 study sites occurred within
emergent, scrub-shrub portions of wetlands. Bog Turtle habitat descriptions are
well-documented elsewhere from the landscape (Myers and Gibbs 2013, Rosenbaum
and Nelson 2010) to the site-specific level (Carter et al. 1999, Chase et al.
1989, Ernst et. al. 1989, Feaga et al. 2013, Kiviat 1978, Morrow et al. 2001, Pittman
et al. 2009, Zappalorti 1976a); thus, we provide only a general description of
the habitat features present at most of our study sites. The common habitat features
at all of our study areas were wetlands that had year-round spring seeps and soft,
muddy substrate (Zappalorti 1978, 1997).
The dominant herbaceous plant species present in the 9 emergent scrub-shrub
wetlands (Table 1) we studied included: Carex stricta Lam. (Tussock Sedge),
Carex atlantica spp. atlantica L.H. Bailey (Prickly Bog Sedge), Carex vulpinoides
Michx. (Foxtail Sedge), Juncus effusus L. (Soft Rush), Leersia oryzoides (L.) Sw.
(Rice Cutgrass), Onoclea sensibilis L. (Sensitive Fern), Polygonum sagittatum L.
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(Arrowleaf Tearthumb ), Impatiens spp. (jewelweed), Sagittaria latifolia Willd.
(Broadleaf Arrowhead), Symplocarpus foetidus (L.) Salisb. ex W.P.C. Barton
(Skunk Cabbage), Typha angustifolia L. (Narrowleaf Cattail), Panicum spp.
(panic grasses), Eleocharis spp. (spike-rushes), Parnassia glauca Raf. (Grass-of-
Parnassus), Dasiphora fruticosa (L.) Rydb. (Shrubby Cinquefoil), Acorus calamus
L. (Sweetflag), Sagittaria cuneata Sheldon (Arumleaf Arrowhead), Polygonum sp.
(smartweed) Scirpus atrovirens Willd. (Dark Green Bulrush), Scirpus cyperinus
(Woolgrass), Acer rubrum L. (Red Maple), and Sphagnum spp. (sphagnum moss).
Common shrub species included Alnus spp. (alders), Viburnum sp. (viburnum), Red
Maple, Salix spp. (willows), and Larix laricina (Du Roi) K. Koch (Tamarack). The
disturbed portions of the wetlands supported invasive plants including Phragmites
australis (Cav.) Trin. Ex Steud. (Common Reed), Rosa multiflora Thun. Ex Murr.
(Multiflora Rose), Phalaris arundinacea L. (Reed Canary Grass), and Lythrum
salicaria L. (Purple Loosestrife).
Methods
We conducted our searches during and after the Bog Turtle nesting season in
June. Turtles in our study region typically lay their eggs between 8 and 29 June,
but we found 1 female nesting on 6 June and another on 1 July (R.T. Zappalorti,
pers. observ.). We searched intensively for concealed eggs in canopy-free areas of
sedges, sphagnum mosses, and other types of graminoid tussocks. We took great
care not to step on tussocks so we did not disturb or crush any unseen eggs in
hidden nests. From 1974 to 1993, we carried out ecological and mark–recapture
studies in addition to finding eggs and monitoring hatching success in the field and
laboratory. Between 1994 and 2012, we concentrated on monitoring nests and eggs
in natural habitat (Zappalorti 1997). We marked with a wooden stake and flagged
each nest found to prevent researchers from accidently stepping on eggs. Prior to
searching for nests and eggs, all researchers thoroughly cleaned their hands with
Lysol® dual-action wipes, 70% isopropyl rubbing alcohol, and/or wore latex surgical
gloves (Star-Med, Sempermed, Clearwater, FL). We took these steps to reduce
human scent at the nest sites and reduce the likelihood of attracting mammalian
egg-predators (but see Burke et al. 2005, Tuberville and Burke 1994).
Nest data
We recorded 2 sets of variables at each nest. The first set described the actual
nest; variables including nest-chamber depth, width, and length, as well as the distance
from the bottom of the elevated nest chamber to the water or substrate below.
To characterize the habitat around the nest, we recorded distance (m) to the nearest
tree with a diameter at breast height (DBH) >7.5 cm and a height > 2 m), distance
to nearest woody shrub <2 m in height, height of nearest emergent vegetation, distance
to nearest emergent vegetation, distance to nearest surface water, and estimated
canopy cover (%) in each cardinal compass direction. We estimated overhead
tree- or shrub-canopy cover at each nest by using a black-plastic ocular tube. The
ocular tube had 2 central cross-hairs (length = 16 cm, diameter = 4 cm). Looking up
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from the nest, but without disturbing it, we held the tube at a 45º angle from the egg
chamber, looked through the tube, and took a total of 4 readings at each nest—1 in
each of the cardinal directions. We estimated up to 25% cover (full cover at a given
cardinal direction) at each compass point for a maximum score of 100% for all 4
estimates. Most canopy trees were fully leafed-out by early June when the turtles
were nesting. Due to time constraints, we collected habitat data from a subset of all
nests found. We used an Oakton pH Tester with BNC Connection (model 35801-00,
Oakton Instruments, Vernon Hills, IL) to record nest-substrate pH.
We combined data both within and between states for analysis because 1 study
site had a relatively small number of nests. While we recognize there may be siteor
state-specific differences, our data represent a range of study sites that might be
considered typical for mid-Atlantic Bog Turtle populations.
Statistical tests
We did not collect data from random points without nests; thus, our analysis is
a quantitative description of known nest sites, not an analysis of nest-site selection
relative to available habitat. We employed principal component analysis (PCA)
with varimax rotation as a data-reduction technique to remove redundancy from our
intercorrelated environmental variables (Kachigan 1991) and identify important
factors and loadings. Chase et al. (1989) used this approach to reduce the number
of habitat variables in their analysis of Bog Turtle habitat. A priori, we decided to
use only those components with eigenvalues >1 in our presentation of the data.
When plotting principal component scores, we used a confidence kernel based on
a nonparametric kernel-density estimator that showed where data (nests) are most
concentrated in the sample. We generated all analyses and figures with SYSTAT®
13 software. Means are reported ± 1 standard deviation.
Results
We found all Bog Turtle nests in microsites that were elevated above standing
water at the time of discovery. Many were in elevated tussocks of grasses or sedges
including Tussock Sedge and Prickly Bog Sedge (n = 28). The nests’ mean elevation
above the substrate was 8.2 cm ± 4.8 (range = 1.4–27.1 cm). Other vegetation
found at nest sites included sphagnum mosses (n = 10), jewelweed (n = 1), Juncus
spp. (rushes; n = 1), Sensitive Fern (n = 1), and Narrow-leaved Cattail ( n = 3). Most
nests concealed under vegetation were covered with a layer of humus, grass blades,
or sphagnum moss (n = 38) at a depth ranging from 0.1–3.5 cm (mean = 1.8 ± 1.1;
(Table 1). Some nests contained eggs that were poorly covered by the turtle, or were
partially or fully exposed to direct sunlight (n = 6; Fig. 1). We covered these nests
with sphagnum moss and all the eggs hatched. We found 2 atypical nests, containing
3 eggs each, atop Red Maple stumps in New Jersey. One nest was in a pocket of soft,
rotting wood. Both were covered in sphagnum moss (depth of cover = 2.2–3.5 cm).
Mean nest-chamber measurements (n = 66) were 3.7 ± 0.99 cm deep (range
= 1.8–6.5), 5.07 ± 1.69 cm long (range = 2.2–10.0), and 3.8 ± 0.9 cm wide
(range = 2.0–6.0). We found evidence of communal-nest sites at 2 Pennsylvania
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Table 1. Dominant vegetation types, habitat characteristics, and structure of Bog Turtle nest sites from 9 study areas in New Jersey and Pennsylvania between
1974 and 2012. The Berks County, PA, study site consisted of 3 meta-populations in a large, connected wetland complex. The Northampton County,
PA, study site consisted of 6 meta-populations in a lar ge, connected wetland complex, but all nests had the same struc ture.
Dominant vegetation Secondary vegetation Nest site structure Type of cover Number
Study area location at nest site 30-cm around nest site or substrate over the eggs of nests
New Jersey
Sussex County Sphagnum moss, Prickly Bog Tussock Sedge, Sensitive Elevated earth and root Sphagnum moss 6
Sedge, Fern hummock
Morris County Sphagnum moss, Red Maple Tussock Sedge, Common Rush Old Red Maple stump Sphagnum moss 1
Monmouth County Sphagnum moss, Red Maple, Prickly Bog Sedge, Tussock Sedge Old Red Maple stump Sphagnum moss 1
Pennsylvania
Lancaster County – A Tussock Sedge, Prickly Bog Reed Canary Grass, Sweetflag Elevated earth and root Twisted blades of 10
Sedge hummock sedge leaves
Lancaster County – B Tussock Sedge, Prickly Bog Fox Sedge, Common Rush Elevated earth and root Twisted blades of 12
Sedge hummock sedge leaves
Berks County Tussock Sedge, Narrow-leaved Fox Sedge, Sweetflag Elevated earth and root Twisted blades of 11
Cattail hummock sedge leaves
Northampton County Tussock Sedge, Prickly Bog Grass-of-Parnassus, Sensitive Fern Elevated earth and root Twisted blades of 5
Sedge hummock sedge leaves
Monroe County Tussock Sedge, Prickly Bog Fox Sedge, Sensitive Fern Elevated earth and root Twisted blades of 19
Sedge hummock sedge leaves
Lehigh County Tussock Sedge, Narrow-leaved Sensitive Fern, Red Maple Elevated earth and root Twisted blades of 1
Cattail hummock sedge leaves
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study sites. Some nests had 2 clutches (n = 4), and we observed 2 nests with 3
clutches. At 1 communal-nest site, a clutch of 4 eggs appeared to have been dislodged
by another nesting female. The substrate pH of the 66 nests ranged from
4.8 to 7.0 (mean = 6.3 ± 0.5). We observed nest-site fidelity in some females. In
Pennsylvania, a radio-tracked female nested in a sheep meadow at the same Prickly
Bog Sedge tussock for 2 consecutive years. Circumstantial evidence suggests similar
behavior in New Jersey—we recaptured gravid females in 2 consecutive years
(n = 4) and 1 turtle for 3 consecutive years at the same nesting area.
Other environmental attributes of nest locations are summarized in Table 2.
PCA of 9 habitat-characteristic variables identified 3 components with eigenvalues
>1. The first component was most strongly related to canopy cover in the west and
distance to the nearest woody shrub, both negatively (Fig. 2). The second component
was related primarily to canopy cover (north and east, respectively), both
positively. The third component was strongly related (positively) to distance to the
nearest tree (Table 3). Collectively, these components explained 65.8% of the total
variance. Four extreme outliers are shown in Figure 2. These nests were characterized
by higher canopy-cover values and/or nearer distances to trees than the means
for the majority of nests. They were also located closer to the nearest emergent
Figure 1. A Bog Turtle nest as found by researchers on 24 June 2012 in Sussex County, NJ.
Three eggs are visible and 1 is partially visible. After the female oviposited, the eggs were
not fully covered. It is not clear if the female left the eggs uncovered after oviposition or
if another turtle or animal disturbed them. After discovering the nest, we covered the eggs
with damp moss to prevent dehydration. All four eggs successfully hatched in the nest.
Photograph © Robert Zappalorti.
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Figure 2. Plot of the
first 2 factor scores
from principal component
analysis of 9
environmental variables
listed in Table
3. Components with
highest loadings are
shown in axis labels.
The enclosed area is
a confidence kernel
based on a nonparametric
kernel-density
estimator that shows
where data (nests)
are most concentrated
in the sample.
The bounds are 1 SD
from the mean. The 4
extreme outliers are
discussed in the text.
From left to right the
first 3 were from nests
in Monroe County, PA, and the last one was from Monmouth County, NJ. Factor scores with
missing data are excluded, leaving only 33 nests (some as overl apping points).
vegetation (including Narrow-leaved Cattails and invasive Purple Loosestrife) than
the mean for the other nests, and one was very low to the substrate. The outlier nests
had variable hatching success. All 3 eggs from a nest located in sphagnum on a Red
Maple stump hatched after we took them to the laboratory. Only one egg hatched
in 2 of the nests, and 3 out of 5 eggs hatched in another. We determined that some
eggs were either infertile or contained an embryo that died during development.
The correlation between factor 1 scores and canopy cover to the west was negative,
showing that as canopy cover increased, the associated factor-scores decreased.
The other 2 factor-score correlations with their respective variables with high loadings
were positive.
Table 2. Summary of environmental attributes associated with Bog Turtle nest sites in New Jersey
and Pennsylvania. Height = height of nearest emergent vegetation (cm), and Emerg veg = emergent
vegetation.
% canopy cover Distance (m) to nearest
Woody Emerg Surface
Height North South East West Tree shrub veg water
n 47 66 66 66 66 50 52 61 58
Minimum 1.9 0.0 0.0 0.0 0.0 0.27 0.3 0.0 0.1
Maximum 150.0 25.0 50.0 70.0 75.0 40.0 10.5 30.0 37.0
Mean 61.9 4.1 4.8 8.0 7.9 89.9 3.4 2.1 7.5
SD 31.3 6.5 9.1 12.2 13.5 8.6 2.2 6.1 9.7
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Discussion
Our results, based on the largest sample of Bog Turtle nests previously analyzed,
confirm earlier reports of nesting-site characteristics and nesting behavior
(see summary in Ernst and Lovich 2009). Unlike most other semi-aquatic turtles,
Bog Turtles do not need to leave their wetland habitat and travel to dry upland
areas to deposit their eggs. Instead, they select slightly elevated sites, often on Tussock
Sedge mounds, for nesting. Only a handful of largely anecdotal publications
describe Bog Turtle nesting under natural conditions, although there are numerous
reports of nesting in captivity (e.g., Arndt 1972, Herman 1986, Zovickian 1971).
Barton and Price (1955) may have been the first to note a preference for elevated
nest locations. At a study site in Lancaster County, PA, they noted a nest that was
“… quite shallow and was 4 or 5 inches above the surface of water in the swamp.”
Holub and Bloomer (1977) also noted elevated nests stating, “Regardless of the particular
nest site chosen, all nesting females have 2 things in common. The nesting
site is always uphill, or on ground that is high and dry such as in the top of a sedge
clump.” Later, still others confirmed the tendency of Bog Turtles to nest in elevated
locations like sedge tussocks and sphagnum hummocks (Wilson et al. 2004). Bog
Turtles occasionally nest in unusual locations like stumps (Table 1), a phenomenon
also observed by Fahey and Jensen (1999) in Georgia. The authors speculated that
ecological succession at the bog they studied limited open areas, thereby forcing
turtles to nest in alternative locations.
Barton and Price (1955) further noted, “It appeared that the female had buried
herself in the moss and, after depositing the eggs, crawled out and allowed the moss
to cover the eggs.” Their observation provides a possible explanation for why some
nests are covered haphazardly or not at all, unlike the nests of most other turtle species.
We observed 6 clutches that were partially or fully exposed to direct sunlight.
Had we not covered the exposed eggs with moss, they may not have hatched, given
their dehydrated appearance, but this assumption needs to be tested further. The behavior
of sometimes leaving the eggs uncovered is poorly understood and requires
additional study.
Table 3. Principal component analysis for 9 variables describing the habitat characteristics of Bog
Turtle nest sites. Loadings for factors with an eigenvalue >1 ar e shown. Variance explained for principal
components 1–3 was 25.0%, 23.1% and 17.7%, respectively .
Principal component
Environmental attribute 1 2 3
Canopy north 0.022 0.718 -0.086
Canopy south -0.331 0.557 0.481
Canopy east 0.175 0.866 0.105
Canopy west -0.793 0.269 0.218
Distance to nearest woody shrub -0.792 -0.308 0.101
Distance to nearest emergent vegetation 0.211 0.083 0.669
Distance to nearest surface water 0.516 -0.411 0.472
Distance to nearest tree -0.302 -0.064 0.768
Height of nearest emergent vegetation 0.668 0.184 0.393
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Nesting areas typically have limited canopy closure, support an array of moisture-
tolerant, low-growing vegetation, and provide ample solar exposure (Ernst and
Lovich 2009). Our analysis supports this characterization in that the variables with
the highest loadings in our PCA were canopy cover (west and east) and distance
to the nearest tree. Cardinal directions of nest exposure have been demonstrated to
influence nest temperatures and thus sex ratios of hatchling turtles; southern and
western exposures have more influence on nest temperatures than do northern or
eastern exposures (Janzen 1994). The high loading scores for canopy cover in factors
1 and 2 may be a reflection of solar exposure of nest sites .
We observed atypical nesting behavior at 5 nests that we measured. The distance
from the top of the nest to the wet ground-surface below ranged from 6.5 cm to 9.0
cm in these unusually low nests, which may be the reason why only 1 out of those
19 eggs hatched. It appears that most of the remaining 18 eggs were lost from water
saturation from repeated rain inundation, causing the embryos to drown. Those
eggs may have hatched during a drought year, but because of high groundwater
levels from excessive rain, the nest sites selected by 5 gravid females were a poor
choice and most eggs did not hatch. Selection of nest sites with excessive cover
and proximity to vegetation including trees can lead to reduced hatching success as
suggested in data for outliers in our PCA analysis.
By selecting nest sites on elevated tussocks or hummocks above the substrate
or water, Bog Turtles protect their eggs from flooding in wetlands. Limited site
availability may explain why multiple females nest in the same tussock (Holub and
Bloomer 1977) and some display nest-site fidelity (see review of nest site fidelity
in turtles in Lovich et al. 2015).
Maintenance of favorable environmental conditions for Bog Turtle nesting is a
significant conservation challenge due to ecological succession of the habitats they
prefer, exacerbated by invasion by exotic plant species (Ernst and Lovich 2009).
Canopy closure due to ecological succession compromises access to the open areas
female Bog Turtles prefer for nesting, as shown by our analysis (Feaga and Haas
2015). Recent studies suggest that low-intensity, pasture-based grazing by livestock
assists in maintaining the conditions that Bog Turtles prefer as nesting habitat
(Tesauro and Ehrenfield 2007). Heavy grazing by too many hoofed stock and associated
nutrient inputs create favorable conditions for invasive plants to become
established; however, these plants may be kept in check by grazing (Tesauro and
Ehrenfield 2007). Careful habitat management, including limited grazing by hoofed
livestock, selective girdling of bark or cutting of trees and shrubs in nesting areas,
and protecting nests with predator-excluder cages may be required to maintain optimum
conditions necessary for nest sites, and ultimately, the survival of Bog Turtle
populations throughout their range (Frier and Zappalorti 1983, Kiviat 1978, Sirois
et al. 2014, Tesauro and Ehrenfield 2007).
Acknowledgments
We thank the following Herpetological Associates employees and other friends who
helped with this long-term study including Tessa Bickhart, Quill Bickley, Dave Burkett,
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Bill Callaghan, the late Peggy Drake, Brain Farrell, Alex Figueroa, Dennis Herman, Matt
McCort, Dave Schneider, Robert Zappolorti Jr., and the late Bern Tryon. Various US Fish
and Wildlife Service personnel from state field offices in the northeast have been particularly
helpful, especially Colin Osborne, Michael Horn, William Koch, Jeremy Markuson,
Wendy Walsh, Alison Whitlock, Bonnie Dershem, and Carole Copeyon. We also thank
Dave Jenkins, Brian Zarate, and Kris Schantz of the New Jersey Department of Environmental
Protection (Endangered and Nongame Species Program), for allowing access to
various wildlife-management areas and for providing the necessary permits to conduct
this research. We appreciate the assistance of Chris Urban from the Pennsylvania Fish and
Boat Commission in providing the necessary permits to work in Pennsylvania. Finally, we
are especially grateful to James Thorne, Michael Pressman and George Gress, of the Pennsylvania
chapter of The Nature Conservancy, for all their help, for permission to work on
their various Preserves, and for funding portions of this important research; however, the
results and conclusions of this study are the responsibility of the authors. Dave Ward provided
useful comments on an earlier version of the manuscript, and Mickey Agha assisted
with manuscript preparation. This research was also partly funded by Herpetological Associates,
Inc., because there are few sources of funding to support such long-term studies.
Any use of trade, product, or firm names is for descriptive purposes only and does not imply
endorsement by the US government.
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