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22001155 SOUTHEASTERN NATURALIST 1V4o(3l.) :1449,1 N–5o0. 53
Herpetofaunal Diversity and Seasonality from a Remnant
Coastal Chenier Forest in Southwestern Louisiana
Abstract - Cheniers are ancient beach ridges in southwestern Louisiana that are often characterized
by coastal forest surrounded by marshland. Coastal chenier forests (CCFs) are
considered an imperiled habitat in Louisiana because many forest remnants are considerably
impacted due to human activities and recent hurricanes. Because little is known about
the herpetofaunal community of CCFs, I initiated a seasonal herpetofaunal diversity and
abundance study on a privately-owned, remnant CCF in eastern Cameron Parish, Louisiana.
Utilizing coverboards and drift fence arrays with pitfall and funnel traps, I documented 12
species (4 anuran, 4 snake, 3 lizard, and 1 turtle) comprising CCF obligate and facultative
species, as well as one marsh transient species. Species-accumulation curves indicate
the sample was representative of the small herpetofaunal community. Three amphibian
(Incilius nebulifer [Gulf Coast Toad], Lithobates sphenocephalus utricularius [Coastal
Plains Leopard Frog], and Gastrophryne carolinensis [Eastern Narrow-mouthed Toad]) and
2 reptile (Scincella lateralis [Little Brown Skink] and Thamnophis p. proximus [Orangestriped
Ribbonsnake]) species comprised 94% of the captures. Diversity was highest during
the spring, with 3 months (March–May) of sampling detecting 92% of the total diversity
observed. Sampling during single months only yielded 42–75% of the diversity. Amphibian
abundance varied by month (highest June to September) and with the presence of rain,
whereas reptile abundance only varied by month (highest in March). Funnel traps were more
effective and quantified diversity better than pitfall traps or coverboards. The herpetofaunal
diversity at the site was low and comprised of mostly generalist species; regional specimen
records also exhibit a modest herpetofaunal community. This data will provide baseline
information to determine the impacts of future hurricanes on the herpetofaunal community,
analyze recolonization dynamics following hurricanes, and make comparisons to other CCF
remnants in the region. I also provide recommendations for improving herpetofauna sampling
methodology in coastal settings.
The Chenier Plain of southwestern Louisiana is a band of coastal wetlands
with interspersed narrow sand and shell ridges called cheniers. Cheniers are
relict beach ridges of late Holocene origin (≤2800 years old; McBride et al.
2007) that have been shaped and formed via the shifting delta of the Mississippi
River and by ocean wave energy (Hoyt 1969, McBride et al. 2007). The chenier
system of southwestern Louisiana is extensive and occurs across ~164 km in
Cameron and Vermilion parishes (Fig. 1). The system is very dynamic in both
longer and shorter time scales due to the shifting sediments of the wandering
Mississippi River (i.e., the river shifts every ~1000–1500 years; McBride et al.
*Rockefeller Wildlife Refuge, Louisiana Department of Wildlife and Fisheries, Grand Chenier,
LA 70643; firstname.lastname@example.org.
Manuscript Editor: John Placyk
2015 Vol. 14, No. 3
2007) and periodic intense hurricanes (approximately every 130–450 years; Liu
and Fearn 2000), respectively.
Quercus virginiana Mill. (Southern Live Oak) and Celtis laevigata Willdenow
(Sugarberry) trees dominate coastal chenier forests (CCFs; Neyland and Meyer
1997), with elevations of cheniers slightly higher (1–4 m; McBride et al. 2007)
than surrounding low-lying coastal marsh. Prior to European settlement in the early
1800s (Midkiff et al. 1995), it is estimated that ~40,470 ha of CCFs occurred along
chenier ridges in southwestern Louisiana (Lester et al. 2005). However, only ~809
to 4047 ha of this CCF habitat remain (2–10%; Lester et al. 2005), with far fewer
intact forest remnants (i.e., full complement of understory, midstory, and canopy)
still in existence (Neyland and Meyer 1997). Consequently, CCFs are considered
imperiled in Louisiana primarily due to human development (i.e., community development,
oil and gas facility development) or alternative land uses (i.e., pasture
land, pit mining; Lester et al. 2005).
Coastal chenier forests are also prone to periodic hurricanes, including high
winds and prolonged stormwater-inundation events. Recently, 2 major hurricanes—
Rita in 2005 and Ike in 2008—made landfall along the southwestern
Louisiana coastline, with wind and storm surges (~3–4.6 m; NOAA 2014) causing
major damage to human infrastructure as well as CCFs in the area. Because many
herpetofauna are not adapted to deal with major flooding and salinity increases associated
with large hurricane storm surges, CCFs likely undergo significant faunal
change and turnover following these major tropical events.
Figure 1. Southwestern Louisiana (inset), with location of chenier ridges (shaded) and
Evariste Nunez Woods and Bird Sanctuary (ENWBS; bottom). Major ridges and ridge complexes
are labeled, as is the Mermentau River which separates eastern and western cheniers.
2015 Vol. 14, No. 3
Other than anecdotal and opportunistic specimen records (e.g., from road cruising),
little data exist on the diversity and abundance of herpetofaunal species that
inhabit CCF remnants. In this study, I sought to determine herpetofaunal diversity
and abundance on a remnant CCF property. Along with this primary goal, I also
wanted to determine the correlates that drive seasonal herpetofaunal diversity and
abundance throughout the annual cycle, as well as determine effective sampling
methodology in this coastal forest habitat type. The information gained will provide
a “baseline” for the herpetological community for the area, enable a comparison of
the current community to historical records for the area, and develop a sampling
methodology for assessing CCF herpetofaunal communities.
The study was conducted at Evariste Nunez Woods and Bird Sanctuary
(ENWBS; 29.738794°N, 92.836653°W), a privately owned CCF remnant (34.9 ha)
located on the Grand Chenier Ridge in eastern Cameron Parish, LA (Fig. 1). Within
the CCF remnant, the site formerly included a private airstrip (4.8 ha) that was
routinely used by Louisiana Department of Wildlife and Fisheries (LDWF) pilots
from the early 1960s until 1998 (G. Perry, LDWF, Grand Chenier, LA, pers. comm.;
Fig 2). Following cessation of flights, the former airstrip has been intermittently cut
for hay and used as a wildlife food plot, while the area surrounding the airstrip has
remained relatively undisturbed as a CCF (30.1 ha).
Hurricanes Rita and Ike changed the structure of the ENWBS, with many large
trees dying, particularly on the northern side of the property (Fig. 2); this massive
tree death was likely associated with long-term stress associated with the 2 hurricanes,
subsequent extended droughts, prolonged water ponding of roots, and salt
inundation. The remaining woods (16.8 ha; 56% of pre-hurricane forest) are dominated
in the overstory by Live Oak and Sugarberry, in the midstory by Ilex decidua
Walter (Deciduous Holly) and Ulmus americanus L. (American Elm) and in the
understory by Sabal minor (Jacq.) Pers. (Dwarf Palmetto) and Rubus sp. (briars).
Even with the loss of some of the mature forest on the property, ENWBS remains
one of the few relatively intact CCF properties in southwestern Louisiana.
I surveyed herpetofauna at ENWBS from July to September 2012 and February
to June 2013; months inclusive between October 2012 and January 2013 could not
be sampled due to an agreement with the landowners to not access the property during
hunting season. I used standard herpetological sampling techniques including
a combination of drift fences with pitfall and funnel traps, as well as coverboards
(Wilson and Gibbons 2010). Five drift fences were set at ENWBS, with each
30.5-m drift fence (i.e., silt fencing material with wooden stakes) containing 2
funnel traps placed on each side and each end of the fence (n = 4 traps per array),
as well as 4 pitfall traps (for schematic design, see Baxley and Qualls ).
2015 Vol. 14, No. 3
Funnel traps made of window screen were covered with Dwarf Palmetto fronds
both for trap concealment and to prevent overheating of trapped individuals. For
pitfall traps, two 18.9-L buckets were recessed at ground level on each side of the
drift fence and equally spaced along the fence at 10.1 m and 20.2 m; holes were
punctured in the bottom of the bucket to promote draining following heavy rains.
A sponge was included in each bucket, and I added small amounts of water on hot
days to prevent overheating and desiccation of trapped individuals. These sponges
also served as floating platforms for trapped individuals during high rain/water
events. During 2013 months (February–June), I utilized plywood coverboards (91
cm x 91 cm x 1.9 cm, n = 4 per array) spaced equally and perpendicular to the fence
( ~5 m away). Each month I attempted to survey the site for 7 consecutive days,
checking the drift-fence arrays (including funnel traps, pitfalls, and coverboards)
once per day during most months, but checking traps twice per day in July and August
2013 because of warmer temperatures (maximum daily temperature >30°C).
Figure 2. Aerial imagery of Evariste Nunez Woods and Bird Sanctuary in 1998 (top) and in
2012 (bottom). For the latter, note the location of drift fences (white lines) and the dramatic
loss of trees on the northern side of the property (light-colored polygon).
2015 Vol. 14, No. 3
I did not choose to utilize Anuran call surveys during the study due to the narrow
strip of CCF (maximum width = 200 m) and the inability to differentiate between
anurans calling from the CCF and the surrounding marshland.
I removed all captured individuals from traps and recorded the species, drift
fence and trap number, and date captured for each individual; individual length and
mass were recorded for a related study. Following processing of each individual,
I immediately released them at the site of capture. I collected meteorological data
(mean, maximum, minimum daily temperatures, and rainfall) from a VantageVue
Weather Station (Davis Instruments, Hayward, CA) located at Rockefeller Wildlife
Refuge (RWR; 29.72847°N, 92.81850°W), ~2.0 km ESE of the center of the
In order to determine the effectiveness of sampling the herpetofaunal community
as well as the efficiency of trap effort across months, I created species
accumulation curves for sampling beginning at 4 spring–summer sampling months
(February–May). One species, Nerodia erythrogaster (Plain-bellied Watersnake),
was not included because it is considered a marsh-transient species and only a
single individual was captured. Sampling was not continuous (only 5–7 days each
month), and therefore, cumulative days are presented in accumulation curves with
the understanding that gaps occurred between sampling months.
I used 2 separate two-factor ANOVAs to determine if amphibian and reptile
abundance (i.e., daily total captures) was equal by month (February–September)
and by the presence of rainfall recorded (yes or no), and a month × rain presence
interaction. For total anuran captures and for the 3 most-common species captured
(Gastrophryne carolinensis [Eastern Narrow-mouthed Toad], Incilius nebulifer
[Gulf Coast Toad], and Lithobates sphenocephalus utricularius [Coastal Plains
Leopard Frog]), I used linear regressions to determine if the amount of rainfall (cm)
corresponded to daily captures.
Throughout the study period at ENWBS, I sampled herpetofauna on 53 days across
8 months (mean = 6.6 days per month) for a total of 1013 funnel trap days (mean
= 126.6/month), 794 pitfall trap days (mean = 99.3/month), and 677 coverboard
days (mean = 135.4/month) (Table 1). Values were less than the maximum possible
throughout the study (funnel and pitfall: 1120, coverboard: 700) due to excessive
water accumulation within pitfall traps and under coverboards, rodent holes in funnel
traps (i.e., may have facilitated escapes), and Solenopsis invicta Buren (Red Imported
Fire Ant) colonies around funnel traps or coverboards.
A total of 908 individuals of 12 species were captured throughout the study,
including 4 anuran, 4 snake, 3 lizard, and 1 turtle species (Tables 2, 3). Three amphibian
species—Gulf Coast Toad (relative abundance [RA]: 0.37), Coastal Plains
Leopard Frog (RA: 0.21), and Eastern Narrow-mouthed Toad (RA: 0.14)—and 2
2015 Vol. 14, No. 3
reptile species—Scincella lateralis (Little Brown Skink; RA: 0.12) and Thamnophis
p. proximus (Orange-striped Ribbonsnake; RA: 0.10)—comprised 94% of
the herpetofaunal community. All other species had RA values ≤ 0.03, with 5 of the
species represented by 3 or fewer captures (Table 3).
Overall, funnel traps captured all 12 species encountered during the study,
while pitfall traps and coverboards captured only 5 (42%) and 4 (33%) species,
respectively. Funnel traps also had a higher overall herpetofaunal capture rate
(0.90 individuals/trap day) compared to pitfall traps (0.37) or coverboards (0.06)
Table 2. Number of captures and capture rates for each species by trap type. Species abbreviations
are as follows: Ac = Anolis c. carolinensis, Cc = Coluber constrictor flaviventris, Gc = Gastrophryne
carolinensis, Hc = Hyla cinerea, In = Incilius nebuliber, Ks = Kinosternon subrubrum hippocrepis,
Lh = Lampropeltis holbrooki, Ls = Lithobates s. utricularius, Ne = Nerodia erythrogaster, Pf = Plestiodon
fasciatus, Sl = Scincella lateralis, and Tp = Thamnophis p. proximus.
Method Ac Cc Gc Hc In Ks Lh
Number of captures
Pitfall 1 0 66 0 182 0 0
Coverboard 0 0 0 0 5 0 0
Funnel trap 2 2 63 3 149 2 7
Pitfall 0.014 0.000 0.083 0.000 0.229 0.000 0.000
Coverboard 0.000 0.000 0.000 0.000 0.007 0.000 0.000
Funnel trap 0.002 0.002 0.127 0.003 0.147 0.002 0.007
Method Ls Ne Pf Sl Tp Total
Number of captures
Pitfall 10 0 15 17 0 291
Coverboard 0 0 6 27 3 41
Funnel trap 177 1 10 68 92 576
Pitfall 0.013 0.000 0.019 0.021 0.000 0.366
Coverboard 0.000 0.000 0.009 0.040 0.004 0.061
Funnel trap 0.175 0.001 0.010 0.067 0.091 0.896
Table 1. Summary table for environmental data at ENWBS, Cameron Parish, LA. Abbreviations : Trap
= funnel trap, Pit = pitfall trap, and CB = coverboard.
Month Days Trap days Pit days CB days Rainfall (cm) Mean temp. (°C) (range)
February 2013 7 132 112 140 0.6 14.4 (10.3–17.6)
March 2013 5 132 112 140 0.4 18.6 (14.6–22.2)
April 2013 6 119 80 120 6.0 20.2 (16.2–23.6)
May 2013 7 132 126 137 3.3 19.2 (14.9–22.7)
June 2013 7 140 140 140 0.6 28.3 (24.5–31.5)
July 2012 7 140 63 n/a 14.2 26.4 (22.8–29.0)
August 2012 5 98 65 n/a 1.7 26.6 (23.4–30.5
September 2012 6 120 96 n/a 3.5 26.8 (23.2–31.6)
Sum total 53 1013 794 677 30.3 -
Mean 6.6 126.6 99.2 135.4 3.8 22.6
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Table 3. Summary table for capture data for ENWBS, Cameron Parish, LA. Abbreviations : Trap = funnel trap, Pit = pitfall trap, and CB = coverboard.
Species abbreviations follow those presented in Table 2. RA. = species relative abundance. TA = total anurans, TR = total reptiles, and TC = total captures.
Month Ac Cc Gc Hc In Ks Lh Ls Ne Pf Sl Tp Diversity TA TR TC
February 2013 1 0 0 1 2 0 0 0 0 0 6 3 5 3 10 13
March 2013 1 0 12 0 2 0 1 0 0 1 34 53 7 14 90 104
April 2013 0 0 1 0 4 0 0 0 1 1 12 14 6 5 28 33
May 2013 0 2 2 0 6 1 4 3 0 5 12 7 9 11 31 42
June 2013 0 0 16 0 19 1 0 78 0 13 17 3 7 113 34 147
July 2012 0 0 30 2 162 0 1 94 0 1 14 1 8 288 17 305
August 2012 0 0 45 0 98 0 0 10 0 6 5 4 6 153 15 168
September 2012 1 0 23 0 43 0 1 2 0 4 12 10 8 68 28 96
Sum total 3 2 129 3 336 2 7 187 1 31 112 95 - 655 253 908
Mean 0.38 0.25 16.13 0.38 42.00 0.25 0.88 23.38 0.13 3.88 14.00 11.88 7 81.88 31.63 113.50
RA less than 0.01 less than 0.01 0.142 less than 0.01 0.370 less than 0.01 less than 0.01 0.21 less than 0.01 0.03 0.12 0.11
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(Table 2). Funnel traps also outperformed the other 2 capture methods with all species
pairwise comparisons except Gulf Coast Toad, Anolis c. carolinensis (Northern
Green Anole), and Plestiodon fasciatus (Common Five-lined Skink), which were
captured in marginally higher rates in pitfall traps relative to funnel traps (Table 2).
Even though traps were checked regularly during the study, overall mortality
was high (10.5%; 95 of 908) due to desiccation of anurans and predation of herpetofauna
by fire ants. Mortality rates were higher for moist-skinned anurans (Coastal
Plains Leopard Frog: 39 of 187 [21%], Eastern Narrow-mouthed Toad: 35 of 129
[27%]) relative to Gulf Coast Toad (16 of 336; 4.8%) and two lizard species (Little
Brown Skink: 2 of 112 [1.7%]; Common Five-lined Skink: 3 of 31 [9.6%]). No
mortality was observed for any of the other species captured.
Species-accumulation curves indicate that an asymptote was reached for herpetofaunal
diversity at this site and that sample efforts accurately represent the site
herpetofaunal community (Fig. 3). Sampling beginning in May appears to best fit
an asymptotic curve for species accumulation, with 10 of the 11 species (91%)
obtained in 15 sample days (7 days in May and June, 1 day in July). To reach a
similar diversity, it took 20, 22, and 25 days for sampling begun in March, April,
and February, respectively. To reach full diversity without marsh species (11 species),
it took between 27 and 36 days, with sampling begun in February needing
the fewest sampling days (27 days, February–May), while sampling begun in April
needing the most sampling days (36 days, April–September).
Figure 3. Herpetofauna species accumulation curves by starting month at Evariste Nunez
Woods and Bird Sanctuary, Cameron Parish, LA.
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Monthly diversity and abundance
Monthly herpetofaunal diversity averaged 7 species, with the greatest species
diversity observed during May 2013 (n = 9) and the lowest during February 2013
(n = 5). Total amphibian captures differed significantly by month (F7,53 = 12.95, P less than
0.0001) and by the presence of rain (F1,53 = 4.07, P = 0.05), but there was no month
× rain presence interaction (F7,53 = 1.74, P = 0.13). Summer months (June–September)
had significantly higher amphibian capture rates than winter (February) or
spring (March–May) months, while days with rain had significantly higher amphibian
capture rates than days without rain. Reptile daily capture rates also differed
significantly (F7,53 = 2.27, P = 0.05) by month, but there was no difference by the
presence of rain (F1,53 = 2.69, P = 0.11) and no month × rain presence interaction
(F7,53 = 1.01, P = 0.43). The month of March had significantly higher daily capture
rates of reptile species than all other sample months.
Rainfall amount was a significant predictor in captures of total amphibians (F1,53
= 14.49, R2 = 0.22, P = 0.0004) and captures of Gulf Coast Toad (F1,29 = 9.30, R2 =
0.26, P = 0.005), but was not a significant predictor of captures of Eastern Narrowmouthed
Toad (F1,30 = 9.30, R2 = 0.0004, P = 0.92) or Coastal Plains Leopard Frog
(F1,22 = 1.86, R2 = 0.09, P = 0.19).
Because some of the CCF obligate (CCF-O) and facultative (CCF-F) species
previously documented in the area (Table 4) were not captured during our
sampling, it is possible that some species may not have been detected, whereas
others may actually not occur in this remnant CCF or are only transient marsh
species (e.g., Nerodia, spp. [watersnakes]). For example, the method of using
Table 4. Herpetofauna of lower Cameron/Vermilion parishes and coastal chenier forests based on
Dundee and Rossman (1989) and specimen records. Under ENWBS, species with a “X*” have been
observed or reported to the author outside of this study. Codes under presence on cheniers (Presence)
represent a presumed chenier obligate species (O), facultative chenier-marsh species (F), and marsh
species (M). EC = eastern cheniers, WC = western cheniers. Continued on the following page.
All species observed on cheniers by clade Presence ENWBS EC WC
Acris blanchardi Harper (Blanchard’s Cricket Frog) F X
Anaxyrus fowleri Hinckley (Fowler’s Toad) O X X
Gastrophryne carolinensis Holbrook (Eastern Narrow-mouthed Toad) F X X X
Hyla cinerea Schneider (Green Treefrog) F X X X
Hyla squirella Bosc (Squirrel Treefrog) F X X
Incilius nebulifer Girard (Gulf Coast Toad) F X X X
Lithobates catesbeianus Shaw (American Bullfrog) M X X
Lithobates clamitans Latreille (Green Frog) M X X
Lithobates grylio Stejneger (Pig Frog) M X X
Lithobates sphenocephalus utricularius Harlan (Coastal Plains F X X X
Pseudacris fouquettei Lemmon et al. (Cajun Chorus Frog) F X
2015 Vol. 14, No. 3
drift-fence arrays poorly detects arboreal species (e.g., Hylid treefrogs). This
limitation is evident because only 3 Northern Green Anoles were detected, and
Pantherophis obsoletus (Sya in James) (Western Ratsnake) or Opheodrys a. aestivus
(L.) (Northern Rough Greensnake) were not detected. However, both of the
latter species have been documented at ENWBS outside of this sampling effort
(W. Selman, pers. observ.).
Table 4, continued.
All species observed on cheniers by clade Presence ENWBS EC WC
Siren intermedia nettingi Barnes (Lesser Siren) M X
Alligator mississipiensis Daudin (American Alligator) M X X
Agkistrodon piscivorus leucostoma Troost (Western Cottonmouth) M X X
Anolis c. carolinensis Voigt (Green Anole) O X X
Aspidoscelis s. sexlineata L. (Eastern Six-lined Racerunner) O X X
Coluber constrictor flaviventris Say (Eastern Yellow-bellied Racer) O X X X
Farancia abacura reinwardtii Schlegel (Western Mud Snake) M X X
Heterodon platirhinos Latreille (Eastern Hog-nosed Snake) O X X
Lampropeltis holbrooki Stejneger (Speckled Kingsnake) F X X X
Lampropeltis triangulum amaura Cope (Louisiana Milksnake) O X
Nerodia c. clarkii Baird and Girard (Gulf Saltmarsh Watersnake) M X X
Nerodia cyclopion Duméril et al. (Mississippi Green Watersnake) M X X
Nerodia erythrogaster Forster (Plain-bellied Watersnake) M X X
Nerodia fasciata confluens Blanchard (Broad-banded Watersnake) M X X
Nerodia r. rhombifer Hallowell (Northern Diamond-backed M X X
Opheodrys a. aestivus L. (Northern Rough Greensnake) O X* X X
Ophisaurus a. attenuatus Cope (Western Slender Glass Lizard) O X
Pantherophis obsoletus Say (Western Ratsnake) O X* X X
Plestiodon fasciatus L. (Common Five-lined Skink) O X X
Regina grahamii Baird and Girard (Graham’s Crayfish Snake) M X X
Regina rigida sinicola Huheey (Gulf Crayfish Snake) M X X
Scincella lateralis Say in James (Little Brown Skink) F X X X
Storeria dekayi limnetes Anderson (Marsh Brownsnake) O X X
Thamnophis p. proximus Say (Orange-striped Ribbonsnake) F X X X
Apalone spinifera pallida Webb (Pallid Spiny Softshell) M X X
Chelydra serpentina L. (Snapping Turtle) M X* X X
Deirochelys reticularia miaria Schwartz (Western Chicken Turtle) F X
Kinosternon subrubrum hippocrepis Gray (Mississippi Mud Turtle) F X X X
Malaclemys terrapin pileata Wied-Neuwied (Mississippi M X X
Pseudemys c. concinna LeConte (Eastern River Cooter) M X X
Terrapene carolina triunguis Agassiz (Three-toed Box Turtle) O X X
Terrapene o. ornata Agassiz (Plains Box Turtle) O X
Trachemys scripta elegans Wied-Neuwied (Red-eared Slider) M X X
Total species 44 15 38 40
2015 Vol. 14, No. 3
Based on the diversity of species captured and CPUE, funnel traps were the
most effective trap for almost every species encountered. They sampled the entire
herpetofaunal community observed during the study. Interestingly, funnel traps
also captured 2 adult Kinosternon subrubrum hippocrepis (Mississippi Mud Turtle)
of 9.3 and 9.4 cm carapace length, respectively. However, funnel traps were prone
to “chew outs” by rodents (i.e., rodents chewing through the window screen trap to
escape) and had high rates of mortality via fire ants and desiccation. For the former,
a stronger gauge wire mesh would be preferred for trapping in similar rodent-prone
areas. Fire ant mortality may be abated through targeted ant-bait application around
traps (Allen et al. 2004). Apparently the palmetto fronds covering the traps did not
provide enough protection from dessication, so that source of mortality may be
harder to relieve. It is likely exacerbated by the relatively constant sea breeze in
coastal habitats, which may therefore warrant the checking of traps twice per day
during windy days (>16 km/h).
Pitfall traps and coverboards were less effective at sampling the herpetofaunal
community and were not complementary to funnel traps as found by Todd et
al. (2007). Pitfall traps often filled with water following heavy rains even though
drainage holes were drilled in the bottom bucket. Buckets did not drain effectively,
likely due to a high water table and poor drainage in the low-lying coastal
setting. Coverboards were relatively new when deployed in February 2013, with
some authors suggesting that time since deployment is important for coverboard
effectiveness (Willson and Gibbons 2010); conversely, others suggest that time
since deployment is not a determinant in coverboard effectiveness (Houze and
Chandler 2002). However, abundant natural debris cover was present at ENWBS
due to long-term dead or dying trees from recent hurricanes, possibly leaving
coverboards less desirable than natural cover objects (Houze and Chandler
2002). Also, the type of coverboard material may have influenced their effectiveness
(Hesed 2012), and thus, experiments using different materials may be
needed to optimize coverboard efforts. Thus, based on these findings in a coastal
forest setting, there are several recommendations that may improve drift-fence
sampling design in these habitats including (1) sampling with stronger mesh
screen funnel traps, (2) not using coverboards or pitfall traps due to ineffectiveness,
(3) checking funnel traps twice per day in windy conditions, regardless of
ambient temperature, and (4) augmenting drift-fence arrays with line-transects
or timed manual searching to better detect arboreal species (Marsh and Haywood
2010). Collectively, implementing these measures would improve sampling
effectiveness, reduce time installing/checking traps, reduce trap mortality, and
better detect arboreal species.
Based on species-accumulation curves, it appears that my sampling efforts
adequately characterized the herpetofaunal community at ENWBS. The number
of sampling days needed to reach 90% (15–25 days) and 100% (27–36 days) community
accumulation varied ~10 days depending on the month in which the sample
counting began. Monthly curve comparisons indicate that starting sampling earlier
in the spring (from mid-February to March) is the most efficient time to accurately
2015 Vol. 14, No. 3
sample herpetofauna in CCF habitats; initiating studies during this period would
likely be beneficial for surveys in other southern Louisiana coa stal habitats.
Southwestern Louisiana herpetofaunal diversity
Considering specimen records, there are 44 reptile and amphibian species that
have been reported from lower Cameron and Vermilion parishes in southwestern
Louisiana (Table 4). Based on the distribution of these records and because roads
occur along most of the cheniers (due to the fact that they are the only high ground
within surrounding marsh), it is likely that the majority are representative of individuals
encountered on roads (as described by LaDuc and Bell 2010). Of those 44
species, Dundee and Rossman (1989) and this study consider 13 species (29.5%)
tightly associated with CCF habitats (i.e., obligate to CCFs; CCF-O), 13 species
(29.5%) inhabit both CCFs and the surrounding marshlands (i.e., facultative; CCFF),
and 18 species (41%) are mostly associated with marsh habitats (Table 4). For
the latter, many of these species are considered marsh transients moving across
chenier habitats to other marsh habitat (e.g., Alligator mississippiensis [American
Alligator]). Further delineation of the 44 species recorded indicates that 38 species
(86%) have been documented in eastern cheniers (east of the Mermentau River) and
40 (91%) in western cheniers (Table 4). However, even though a similar percentage
is observed in eastern and western cheniers, species are not equally represented
along the longitudinal gradient even within this relatively small geographic range.
Western cheniers are more representative of scrub-shrub habitats and have some
species more characteristic of herpetofauna from Texas (e.g., Terrapene o. ornata
[Plains Box Turtle]).
The sampling site at ENWBS is situated within an eastern chenier complex, and
based on specimen records reported (Dundee and Rossman 1989, Herpnet 2014),
there are 10 CCF-O and 9 CCF-F species that have been recorded in the surrounding
area. Sampling at ENWBS documented 3 CCF-O species (33%), 8 CCF-F species
(89%), and 1 marsh species. Previously documented eastern CCF-O species that
were not documented at ENWBS include Anaxyrus fowleri Hinckley (Fowler’s
Toad), Terrapene carolina triunguis (Agassiz) (Three-toed Box Turtle), Aspidoscelis
s. sexlineata (L.) (Eastern Six-lined Racerunner), Heterodon platirhinos
Latreille in Sonnini & Latreille (Eastern Hog-nosed Snake), Storeria dekayi limnetes
Anderson (Marsh Brown Snake), Northern Rough Greensnake, and Western
Ratsnake. The latter two have been documented by the author at ENWBS outside
of the study period. Marsh Brown Snakes have been observed < 2 km away at RWR
(W. Selman, pers. observ.), and it is not likely that Eastern Six-lined Racerunner
would have been encountered because regional records appear to be from beach
and dune habitats. The only CCF-F species not encountered at the site was Hyla
squirella Bosc in Daudin (Squirrel Treefrog), but this species has been readily heard
calling ~0.5 km away at RWR (W. Selman, pers. observ.).
Thus, the only species lacking from the sample at ENWBS that had been documented
previously at the site but are lacking recent records or observations in the
area are Fowler’s Toad, Three-toed Box Turtle, and Eastern Hog-nosed Snake.
2015 Vol. 14, No. 3
Specimen records indicate that the most recent collections for these 3 species
date from the 1960s–1970s (Herpnet database search 3 December 2014), with a
personal observation of the Eastern Hog-nosed Snake ~3.5 km east of ENWBS in
the early 2000s (P. Trosclair, LDWF, Grand Chenier, LA, pers. comm.). Because
these species were observed prior to Hurricanes Rita and Ike, it is possible that
their populations were diminished or were extirpated from the region due to the
impacts of those 2 major storms. Other studies along the Gulf Coast have documented
changes to herpetofaunal communities following hurricanes (Nicoletto
2013, Schriever et al. 2009). However, because the sampling in this study was
limited to a single CCF remnant, it is possible that these species still occur in the
area. Additional sample sites and effort may reveal these species to be extant in
the eastern chenier region.
In summary, this study indicates that the herpetofaunal community of ENWBS
is relatively small, but in general it is similar to previously documented species in
the area (including CCF-O and CCF-F species). Further, regional specimen records
from southwestern Louisiana indicate that CCF habitats are represented by 13
CCF-O and 13 CCF-F species, indicating a relatively modest herpetofaunal community
compared to other studies in the southeastern United States (e.g., 54 species
at 24 sites in south Mississippi [Baxley and Qualls 2009], 59 species at a single
site in South Carolina [Todd et al. 2007]). Almost all species documented in CCFs
would be considered “generalist” species.
Effect of season and environmental conditions
There have been few studies that assess herpetofaunal communities across the
annual cycle (Todd et al. 2007). This study found that spring sampling (March–
May) yielded the highest species diversity. During the summer (June–September),
the community remained diverse, but was dominated by 3 anuran species (Gulf
Coast Toad, Eastern Narrow-mouthed Toad, and Coastal Plains Leopard Frog);
however, abundance of only 1 of these species (Gulf Coast Toad) appeared to be
driven by rainfall amounts, whereas patterns of abundance for the other 2 species
may have been most affected by movement between marsh habitats on either side
of the chenier for breeding. I conducted no fall sampling due to stipulations by the
landowner, but it is likely that diversity declines during the period leading into
the winter. Even though the only winter sampling month was February, monthly
diversity was lowest during this month, probably driven by dormancy during cooler
temperatures (Todd et al. 2007, Vitt and Caldwell 2014).
This study indicates that sampling across multiple spring months (March–May)
is needed to characterize most of the community diversity. Sampling a single
week per month from March through May yielded 92% of species (only excluding
H. cinerea [Green Treefrogs]), while sampling for just a single week of a single
month yielded 42–75% of the community. Because little information is known
about CCF herpetofauna, these data can be used for future comparisons following
periodic hurricanes and to determine the dynamics of recolonization events.
2015 Vol. 14, No. 3
LDWF’s Rockefeller Trust Funds financially supported this research project. I would
like to thank J. Landry, A. Toepfer, and C. Reeves for assistance with constructing the
drift-fence arrays, as well as C. Reeves, D. Brown, R. Elsey, and R. King for assisting with
checking traps in 2013. The author also appreciates the Nunez family for permitting access
to sample on their property during the study. Former RWR Program Manager T. Hess and
LDWF administrator B. Baker also supported the implementation of this project. R. Elsey,
J. Boundy, and 2 anonymous reviewers provided helpful comments on an earlier draft of
this manuscript. LDWF approved of this project, and I complied with all applicable animal
care guidelines as outlined by Society for the Study of Amphibians and Reptiles.
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