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2019 SOUTHEASTERN NATURALIST 18(2):256–269
Overwintering Anuran Niche Preferences in a Series of
Interconnected Ponds in Northwestern Florida
Caleb M. Bomske1,* and Nate Bickford2,3
Abstract - This study identified variations in pond bank gradients and associated plant assemblages
to better understand niche preferences of 3 species of overwintering anurans—
Acris gryllus (Southern Cricket Frog), Lithobates grylio (Pig Frog), and Lithobates sphenocephalus
(Southern Leopard Frog)—in northwest Florida (Escambia County). We selected 7
regions of 4 interconnected ponds in a coastal pine flatwoods wetland. We conducted visual
and auditory surveys once every week for 10 weeks from 17 January to 24 March 2017. We
categorized survey areas along pond shorelines by the plant assemblage composition and
species richness, pond bank steepness, and sunlight exposure. We looked for correlations
between each species and specific niche characteristics. None of the anuran species studied
showed a preference for the amount of sunlight or the slope of the pond bank. However,
plant species richness was positively correlated with Southern Cricket Frogs and negatively
correlated with Pig Frogs; thus, there was a very strong negative correlation between Pig
Frogs and Southern Cricket Frogs. Southern Cricket Frogs, the smallest frog species in this
study, prefers high plant species richness, possibly for increased cover from predators, and
avoids potential predators like Pig Frogs. Pig Frogs prefer lower species richness, relying
on open water for escape. The Southern Leopard Frog showed no vegetation preferences,
possibly because the species is more adaptable and has a variety of predator evasion methods.
Wetland plant assemblages are an accurate reflection of life-history habits of anurans,
particularly predator evasion tactics.
Introduction
Florida is a hotspot of reptile and amphibian diversity (Blaustein 2008, Farrell
et al. 2011). As one of the 5 most biodiverse regions in North America, no other
place in the US or Canada has more species of frogs than northwestern Florida
(Blaustein 2008). However, amphibians, including anurans, are currently in sharp
decline globally (Catenazzi et al. 2011, Gallant et al. 2007) and Florida is not an
exception (Cassani et al. 2015). Temperate regions like the US, which already have
lower anuran diversity than the tropics, are at a higher risk to environmental stressors
(Wiens 2007). Anurans are sometimes considered environmental indicators of
ecosystem health (Guzy et al. 2012, Kerby et al. 2010, Niemi et al. 2007, Welsh
and Ollivier 1998). Therefore, identifying the environmental factors, such as plant
diversity (Chandler et al. 2015, Cunningham et al. 2007, Sasaki et al. 2015, Shulse
et al. 2012), that contribute to anuran biodiversity is crucial to understanding and
preserving ecosystem health in the future.
1Department of Horticulture and Natural Resources, Kansas State University, Manhattan,
KS 66506. 2Department of Biology, University of Nebraska, Kearney, NE 68849.3Current
address - Departmet of Biology, Colorado State University Pueblo, Pueblo, CO 81001. *Corresponding
author - bomske@ksu.edu.
Manuscript Editor: Scott Markwith
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Many studies have focused on wide-scale environmental factors that influence
amphibian abundances. The availability of high-quality habitat is an accurate predictor
of frog abundances (Ficetola et al. 2015). Habitat fragmentation and loss
are among the leading causes of amphibian declines (Anderson et al. 2004, Becker
et al. 2007, Cushman 2006, Delis et al. 1996, Gallant et al. 2007, Lehtinen et al.
1999). However, frog diversity is sometimes greater in agricultural farm ponds
than in native woodland ponds (Alix et al. 2014) and some species, such as Lithobates
sphenocephalus (Cope) (Southern Leopard Frog), actually prefer agricultural
influences (Alix et al. 2014). Even when species richness increases in a landscape
fragmented by agriculture, logging, and development, behavioral diversity, such
as reproductive modes, usually declines (Almeida-Gomes and Rocha 2015, Bickford
et al. 2010). Many anuran species are completely absent from urbanized areas
(Guzy et al. 2012). Hylids (treefrogs), like Acris gryllus (LeConte) (Southern
Cricket Frog), are particularly sensitive to habitat changes (Alix et al. 2014, Anderson
et al. 2004, Delis et al. 1996, Fardell et al. 2018). Areas of greater amphibian
species richness are currently experiencing the highest rates of habitat loss (Gallant
et al. 2007). A deeper understanding of habitat use among amphibians is crucial to
their preservation.
Comparatively few studies have attempted to characterize frog habitat use on a
fine scale, but microhabitat characteristics are crucial to anuran breeding success
and resource partitioning (Baldwin et al. 2006, Gorman and Haas 2011). Many ranids
(like Lithobates) utilize non-breeding habitats seasonally, so conservation of
adjacent upland areas is important (Baldwin et al. 2006, Blihovde 2006, Fellers and
Kleeman 2007, Grand et al. 2017, Harper et al. 2008, Pitt et al. 2017, Regosin et
al. 2003). Unfortunately, most studies that investigated anuran microhabitat selection
have focused on northern species that hibernate and, therefore, shed little light
on the winter habitat preferences of subtropical (Florida) ranids like the Southern
Leopard Frog and Lithobates grylio Stejneger (Pig Frog). Even studies that had
more-comprehensive data collection times only recorded presence or absence for
ranids at sites (Baskale and Çapar 2016), which says little of niche preferences
within suitable habitat. Some studies have indicated that changes in vegetation have
an insignificant effect on amphibian communities on a broad scale (Chandler et al.
2015) and that shallow littoral zones are much better predictors of amphibian species
richness then vegetation (Porej and Hetherington 2005). However, amphibian
diversity is usually associated with high plant species richness (Cunningham et al.
2007, Sasaki et al. 2015, Shulse et al. 2012) and increased canopy cover (Baskale
and Çapar 2016, Werner et al. 2007). Water chemistry, which can be influenced by
plant species, also has an influence on anuran habitat choices (Baskale and Çapar
2016). Compounds from the invasive Triadica sebifera (L.) Small (Chinese Tallow)
are known to inhibit Southern Leopard Frog larval development if leaf litter is allowed
to decompose in the water (Adams and Saenz 2012).
Other wetland species can impact anuran abundances. The presence of predatory
fish normally decreases the abundances of ranids like the Southern Leopard Frog
and Pig Frog (Holbrook and Dorn 2016, Porej and Hetherington 2005). Invasive
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Pomacea maculata Perry (Apple Snail) also depredate anuran eggs (Carter et al.
2018). Other predators, such as snakes and turtles, may also influence anuran
species assemblages. Ecosystem engineers, like Castor canadensis Kuhl (North
American Beaver, hereafter, Beaver), also have an effect on anuran diversity and
abundance (Wright et al. 2002). More research is needed on the niche and microhabitat
level to understand anuran habitat preferences.
All 3 of the species in this study can be considered habitat generalists and 2, the
Southern Cricket Frog and Southern Leopard Frog, are the most abundant species
of anuran on the southeastern US Gulf coast (Erwin et al. 2016). Bayless (1969)
showed that Southern Cricket Frogs and A. crepitans Baird (Northern Cricket
Frog) avoided interspecific competition through differences in habitat preferences.
Although Southern Cricket Frogs prefer ponds like those in our study, Northern
Cricket Frogs prefer more extensive wetlands. This preference may be because
Southern Cricket Frogs are more selective than Northern Cricket Frogs (Alix et
al. 2014, Bayless 1969). However, compared to a wider variety of anuran species,
Southern Cricket Frogs are less habitat selective (Chandler et al. 2015). Southern
Cricket Frogs are declining throughout the Southeast but increasing in Florida (Villena
et al. 2016). Southern Cricket Frogs were the only tree frog species included
in this study.
Studies have indicated that some populations of Pig Frog are in decline, possibly
because of habitat changes (Cassani et al. 2015). Interestingly, Pig Frogs seem
to benefit from encroaching development (Delis et al. 1996). This effect may be
because they have fairly broad habitat preferences (Delis et al. 1996). Variations in
vegetation between different habitats seem to have little effect on Pig Frogs (Chandler
et al. 2015); however, permanency of ponds is crucial, since they rarely inhabit
ephemeral wetlands (Chandler et al. 2015). Pig Frogs are more uncommon than the
other frog species included in this study (Cassani et al. 2015) .
Southern Leopard Frogs are true habitat generalists capable of taking advantage
of disturbed areas (Alix et al. 2014, Chandler et al. 2015, Delis et al. 1996)
and moving widely between various habitats (Pitt et al. 2017). They are often
the most abundant species of anuran in wetland areas because they are largely
unaffected by vegetation cover or hydroperiod (Chandler et al. 2015, Delis et al.
1996). They have adaptable and diverse behaviors, including a variety of escape
methods (Bateman and Fleming 2014). In areas of less vegetation cover, Southern
Leopard Frogs tend to remain still but, in areas of high vegetation density, they
may flee into thick brush or the water (Bateman and Fleming 2014). Younger
frogs tend to remain closer to water for quick escape and vocalize less when fleeing
predators (Bateman and Fleming 2014). Southern Leopard Frog occupancy
has increased throughout most of the southeastern US, including Florida (Villena
et al. 2016), likely due to their adaptability.
Anuran species may select different habitats to avoid interspecific competitors
(Bayless 1969, Gorman and Haas 2011) and predators (Buxton et al. 2017), or
because of their reproductive biology (Gorman and Haas 2011). Predator avoidance
and breeding adaptations are linked because amphibian larvae and eggs are
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particularly sensitive to predators (Buxton et al. 2017, Werner and McPeek 1994).
Lithobates species can coexist at the same ponds because of resource partitioning
(Gorman and Haas 2011). While Southern Leopard Frogs breed through the winter
(Lannoo 2005), Pig Frogs are spring and summer breeders (Lamb 1984). Additionally,
Pig Frogs chorus from deeper water than Southern Leopard Frogs, which
remain closer to the shore (Lamb 1984). Southern Cricket Frogs do not compete
with Lithobates directly, but Pig Frogs have been known to prey on hylids, including
Southern Cricket Frogs (Ugarte et al. 2007). Therefore, Southern Cricket Frogs
probably avoid predatory Lithobates. Microhabitat selection in anurans is important
to understanding their ecology and conservation. This study aimed to analyze
variations in non-breeding, winter microhabitat and niche selection among 3 species
of subtropical American anurans.
Field-site Description
We performed this study at West Campus (30°23'35''N, 87°25'19''W) of Pensacola
Christian College (PCC), a 107-ha (265-ac) private property with recreational
facilities for sailing, kayaking, fishing, and other activities. The average winter
temperatures is 10–15 °C, but temperatures often rise above 20 °C. Northwest
Florida has a humid subtropical climate within the expansive southeastern conifer
forests ecoregion. Southern yellow pine forest, comprised of Pinus echinata Mill.
(Shortleaf Pine), P. elliottii (Slash Pine), P. palustris Mill. (Longleaf Pine), and
P. taeda L. (Loblolly Pine), is the predominant ecosystem. Average annual precipitation
is ~1.5 m, but most rainfall occurs during summer’s wet season (hurricanes
and tropical storms are common along the Gulf of Mexico’ s coast).
The wetland complex at our study site consists of 6 ponds along the shores of
Perdido Bay in northwestern Florida (Fig. 1). Pond 1 is the most isolated pond. For
most of the year, the narrow channel through pine flatwoods forests is dry but, during
storms and wet periods, it drains directly into Pond 2, about 75 m away. Pond 2
drains into Pond 3, but during high water both ponds merge together over the shallow,
10-m, Sphagnum (peat moss)-choked channel connecting them. Pond 3 is the
largest pond in the study area but, at its midpoint, a beaver dam partially separates
it from Pond 4. Pond 4 drains into Pond 5, which drains into Pond 6. However, Pond
5 and 6 are closer to Perdido Bay and had saltwater intrusions from a hurricane.
Therefore, we excluded Ponds 5 and 6 from this study. Pond 1 is 500 m long and 20
m wide, pond 2 is 75 m long and 10 m wide, pond 3 is 50 m long and 10 m wide,
and pond 4 is about 90 m long and 50 m wide. All 4 ponds varied greatly in their
shape and depth.
We identified locations for the study based on transitions in plant assemblages,
canopy cover, and the slope of the bank. We organized locations into 7 distinct
areas. Area 1 included all of Pond 1 and Area 2 included all of Pond 2. Area 1 was
characterized by open, gently sloping, grassy banks with sparse woody plants. Area
2 was characterized by steep banks lined with Slash Pine, Taxodium distichum
(Bald-Cypress), and Vaccinium corymbosum (Highbush Blueberry). Area 3 was the
northernmost 150 m of Pond 3, Area 4 included the next 200 m southwest of Area
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3, and Area 5 was the final, southernmost 150 m of Pond 3. Trees and shrubs were
uncommon in Area 3. Emergent species were common because of the increased
sunlight. The only common aquatic and emergent plant of Area 5 was Eleocharis
spp. (spike rushes; there appears to be more than one species at Pond 3, or else a
different species than those commonly found at ponds 1 and 2). The lack of aquatic
and emergent vegetation can be attributed to the abundance of Slash Pine. We divided
Pond 4 in half, with Area 6 covering the southern half and Area 7 including
the northern half. Area 6 had very steep banks. Trees and shrubs were uncommon.
Specific plant species and variations in plant community structure at each area are
listed in Table 1.
Methods
We conducted anuran surveys weekly from 17 January 2017 through 24 March
2017. This timing represents winter anuran assemblages. Although many species
continue to chorus throughout the summer, this study focused on overwintering
anurans at permanent ponds. We avoided the diversity of later choruses of anurans,
primarily composed of hylids, by limiting this study to Florida’s winter months.
Figure 1. Map of the study areas at West Campus (Google Maps 2018). Study areas are
circled by dotted lines and bodies of water are solid white. P1 = Pond 1, P2 = Pond 2, P3 =
Pond 3, P4 = Pond 4, P5 = Pond 5, and P6 = Pond 6.
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Anurans chorus most in the evenings after sunset. To avoid biases, we performed
surveys regardless of varying weather conditions (cold, rain, humidity, etc.) beginning
at sunset and lasting for as long as it took to complete the transect at each
pond. We undertook surveys at all West Campus ponds every Friday night for 10
weeks. We collected plant data from April to May 2018, when many species were
more conspicuous and easier to identify than at other times. Although vegetative
mass increases later in the season, the number of plant of species present at the sites
remained approximately the same throughout the duration of this study.
We performed surveys around the circumference of every pond, and set as the
unit of observation a 2-m wide transect parallel to the corresponding sections of
pond shore in each of the 7 survey areas. Ponds were longer than wide and we
sampled transects on both sides of the ponds to be as representative as possible.
We identified individual anurans primarily through call detection. On most nights,
we were able to identify the source of each call, which eliminated duplication
bias. On warmer nights, when chorusing was more profuse, identifying individual
frogs was difficult. In these cases, we positioned ourselves in the center of
each study area and counted as many frogs as possible to produce a sample that
Table 1. Plant species richness at the 7 study areas. 2 = common species (present in at least half of all segments
surveyed), 1 = uncommon species (present, but in less than half of all segments surveyed), and 0 = absent.
Study Area
Scientific name Common name 1 2 3 4 5 6 7
Acer rubrum L. Red Maple 0 0 1 0 0 0 0
Andropogon virginicus L. Broomsedge Bluestem 0 1 1 1 2 0 1
Aristida stricta Michx. Wiregrass 0 1 0 0 0 0 0
Centella asiatica (L.) Urb. Spadeleaf 0 1 0 0 0 1 2
Cliftonia monophyla (Lam.) Sarg. Black Titi 1 0 0 0 0 0 0
Dichanthelium sp. Witchgrass 0 0 1 1 2 1 2
Drosera brevifolia Pursh Dwarf Sundew 0 0 0 0 2 0 0
Drosera intermedia Hayne Water Sundew 1 2 2 2 1 1 2
Eleocharis spp. Spikerushes 2 2 2 1 2 1 2
Eriocaulon compressum Lam. Flattened Pipewort 0 0 2 2 2 1 1
Hydrilla verticillata (L.f.) Royle Waterthyme 1 1 2 2 2 2 2
Hydrocotyle bonariensis Comm. ex Lam. Largeleaf Marshpennywort 0 0 0 0 0 0 1
Iva frutescens L. Bigleaf Sumpweed 0 1 0 1 0 0 0
Lachnocaulon anceps (Walter) Morong Whitehead Bogbutton 0 0 0 0 1 0 0
Magnolia grandiflora L. Southern Magnolia 0 0 0 1 0 0 1
Magnolia virginiana L. Sweetbay 0 1 1 0 0 0 1
Morella cerifera (L.) Small Southern Bayberry 0 0 1 1 1 1 1
Panicum sp. Panicgrass 0 2 0 0 0 2 0
Peltandra sagittifolia (Michx.) Morong White Arrow Arum 0 0 1 0 0 0 0
Pinus elliottii Engelm. Slash Pine 2 2 1 2 0 1 1
Sphagnum spp. Peat Mosses 0 0 1 1 2 0 0
Taxodium distichum (L.) Rich. Bald-Cypress 0 1 1 2 1 1 1
Triadica sebifera (L.) Small Popcorntree 0 0 0 0 0 1 0
Utricularia sp. Bladderwort 1 0 0 0 0 0 0
Vaccinium corymbosum L. Highbush Blueberry 0 0 0 2 1 1 1
Vitis rotundifolia Michx. Muscadine 0 0 0 1 1 0 0
Xyris sp. Yelloweyed-grass 1 1 2 1 0 1 1
Species richness 7 12 14 15 13 13 15
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included a minimum number of individuals. On a couple of particularly difficult
nights, we averaged 2 or 3 estimates of the minimum number of individuals at
each area. We used flashlights and headlamps to detect anurans for visual identification
to validate auditory surveys.
Captures were rarely necessary. However, if identification of an anuran proved
difficult, temporary capture was needed. In particular, Acris gryllus (LeConte)
(Southern Cricket Frog) and Acris crepitans Baird (Northern Cricket Frog) are
difficult to distinguish. Some species of Lithobates in this region (L. catesbeianus
[Shaw] [American Bullfrog], L. clamitans [Latreille] [Green Frog], Pig Frog,
L. heckscheri [Wright] [River Frog], etc.) are easily confused when not chorusing,
so captures were occasionally required to identify members of this genus, especially
early in the study. We employed a variety of nets to aid in capture. There were
not always appropriate land paths around ponds, and because identifying individual
anurans in a chorus is sometimes difficult from land, we also utilized waders to allow
movement around the ponds. We excluded from our counts any frogs that we
could not positively identify.
We included other species of potential interest if encountered along the transects.
Beaver were present at all ponds but we noted them only when seen (sign
was excluded). We recorded all sightings as individual data points so that we
could determine the frequency that Beavers would be in any given study area, not
their presence or absence from an area. We used the same method to count turtles
(Trachemys scripta (Thunberg in Schoepff) [Pond Slider]) and snakes (Agkistrodon
piscivorus (Lacépède) [Cottonmouth] and Nerodia fasciata (L.) [Banded
Water Snake]). Turtles habitually rest just below the water’s surface near the
shore at night; thus, they were easy to count. Snakes were active at night, hunting
for frogs around shorelines or shallow water.
We sampled plant communities along transects correlating with those used for
the anuran surveys (see above). We identified plants in each area as common (present
in at least half of all 1-m segments of the transect) or uncommon (present in
less than half of all 1-m segments of the transect). We measured 1-m–long segments
with a marked net handle. We identified all common and uncommon species along
pond margins to at least the genus level. We considered species that appeared as
isolated specimens in just 1 or 2 of the transects to be inconsequential and we excluded
them for this study (a few of these, especially Poaceae, were not identified).
We also recorded canopy cover and steepness of the bank at each area.
We calculated the proportional frequency of each anuran species (Southern
Cricket Frog, Pig Frog, Southern Leopard Frog) and the plant species richness at
each of the 7 study areas (n = 7). We conducted 2-sample t-tests to compare anuran
frequencies at areas with high canopy cover to those that had little canopy cover
(P = 0.5). We also conducted 2-sample t-tests to compare anuran frequencies at
steep and gently sloping banks (P = 0.5). We employed Pearson correlations to
compare all anuran frequencies with one another, plant species richness, and other
recorded species (Beavers, turtles, snakes, fish).
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Results
We regularly detected 3 anuran species (Southern Cricket Frog, Pig Frog,
Southern Leopard Frog) at each area (Table 2). We recorded a 4th species, Anaxyrus
terrestris (Bonnaterre) (Southern Toad), at areas 3, 4, and 5 (n = 6, n = 2, n = 1,
respectively) during periods of warmer weather when it entered the ponds for
breeding purposes only. We heard a single Hyla squirella Bosc (Squirrel Treefrog)
calling at area 5. We excluded both of these species from the anuran data set as nonresident,
seasonal species. We also noted possible anuran predators during surveys
as we encountered them in the anurans’ habitat (Table 3). We detected Esox niger
Lesueur (Chain Pickerel) and Lepomis macrochirus Rafineasque (Bluegill Sunfish)
in ponds 1, 2, and 5 and 2, 4, and 5, respectively. We detected Micropterus salmoides
(Lacépède) (Largemouth Bass) only in pond 3 and Amia calva L. (Bowfin) in ponds
2 and 3. All 4 of these species are known to eat frogs (Beaty 2017, De Oliveira et
al. 2016, Goulet et al. 2016, Lagler and Hubbs 1940). Amphiuma means Garden
(Two-toed Amphiuma), a large salamander species that preys on frogs (Schalk et al.
2010), was also present but found in pond 3 only. Other aquatic predators present
in the ponds were Cottonmouths (ponds 2, 3, and 4), Banded Water Snakes (ponds
3 and 4), and the Pond Sliders (ponds 2, 3, and 4). We observed Beavers at ponds 2,
3, and 4, but old shavings at pond 1 indicated that they also o ccurred there.
There appears to be no relationship between frogs and canopy cover or bank
slope on a microhabitat scale (t-test). Pearson correlation analysis revealed a strong
negative correlation between Southern Cricket Frogs and Pig Frogs (r = -0.9647),
Table 3. Aquatic or semi-aquatic predators of frogs at the study areas. CP = Chain Pickerel, LB =
Largemouth Bass, BF = Bowfin, BG = Bluegill, TA. = Two-toed Amphiuma, CM = Cottonmouth,
BW= Banded Watersnake, and PS = Pond Slider. Numbers under each species denote the number of
individuals detected at each area.
Predators
Areas CP LB BF BG TA CM BW PS
1 1 0 0 0 0 0 0 0
2 2 1 1 1 0 2 0 1
3 0 0 0 0 1 1 2 6
4 0 1 1 1 1 1 0 6
5 2 0 0 1 0 1 0 0
6 0 0 0 0 0 0 0 4
7 0 0 0 0 0 4 2 1
Table 2. Anuran proportions at the 7 study areas.
Species Area 1 Area 2 Area 3 Area 4 Area 5 Area 6 Area 7
Southern Cricket Frog 0.87 0.67 0.71 0.84 0.38 0.57 0.70
Southern Leopard Frog 0.11 0.13 0.19 0.11 0.13 0.14 0.04
Pig Frog 0.02 0.19 0.10 0.05 0.50 0.29 0.26
Plant species richness 13 15 14 12 7 13 15
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but a positive correlation between plant species richness and Southern Cricket
Frogs (r = 0.6187; Fig. 2). Consequentially, there was a negative correlation between
Pig Frogs and plant species richness (r = -0.5931). Plant species richness
also had a positive correlation with snakes (r = 0.5358) and Beavers (r = 0.5253).
Southern Leopard Frogs correlated negatively with snakes (r = -.0.5175; Fig. 3) but
positively with turtles (r = 0.6853) and Beavers (r = 0.7149; Fig. 4). There was also
a strong positive correlation between Beavers and turtles ( r = 0.7685).
Discussion
Localized variations in habitat have a variety of effects on anuran species frequencies.
In contrast to studies conducted at a broader scale (Baskale and Çapar
2016, Porej and Hetherington 2005, Werner et al. 2007), our findings indicate
that the slope of a bank and microhabitat canopy cover had little influence on the
anuran species in this study. Plant species richness has often been correlated to
anuran abundances over broad scales (Cunningham et al. 2007, Sasaki et al. 2015,
Shulse et al. 2012) but, on the assemblage level, the trends were less clear (Fig. 2).
Figure 2. Southern Cricket Frogs have a strong positive correlation to plant species richness,
Pig Frogs have a negative correlation to plant species richness, and Southern Leopard Frogs
have no significant correlation to plant species richness.
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The only anuran in this study to correlate positively with plant species richness
was the Southern Cricket Frog. Pig Frogs, in contrast, had a negative relationship
with vegetation, which is probably a reflection of the tendency of Pig Frogs to sit
directly in the water and escape to the water when approached, rather than relying
on vegetation for cover (Lamb 1984). In our study, Southern Leopard Frogs did not
have any significant relationship with plant species richness; this species has the
most adaptable and diverse escape strategies (Bateman and Flemi ng 2014).
Our results indicate that predator evasion is the driving force behind anuran and
plant associations. This suggestion is confirmed by observed relationships between
predator and anuran occurrences. Pig Frogs are known to prey on Southern Cricket
Figure 3. Southern Leopard
Frogs have a negative
correlation with predatory
snakes (Cottonmouth
and Banded Water Snake).
Similarly, Southern Cricket
Frogs avoid Southern Leopard
Frogs. Figure 2 illustrates
this relationship with
plant species richness.
Figure 4. Pond Slider and
Southern Leopard Frog correlations
to Beavers.
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Frogs and other small hylids (Ugarte et al. 2007). The strong negative correlation
between these 2 species is likely a reflection of Southern Cricket Frogs’ avoidance
of Pig Frogs, since other studies have indicated that plant species richness has little
bearing on either species (Chandler et al. 2015). A future comparison of habitat
usage by Southern Cricket Frogs in the absence of Pig Frogs could be revealing.
Our finding of a lack of a negative correlation between Southern Cricket Frogs and
Southern Leopard Frogs, a potential predator, was unexpected, but could be attributed
to a number of habitat elements. Lithobates species seem less sensitive to
predators than Southern Cricket Frogs. Although the negative correlation between
Southern Cricket Frogs and Pig Frogs was very strong, the only significant negative
correlation between Lithobates and a predator was between Southern Leopard
Frogs and snakes. Other predators (e.g., turtles, fish) are unlikely to move out of
water in search of food, but snakes are more versatile; hence, the avoidance by
Southern Leopard Frogs. Curiously, occurrences of predatory fish had no noticeable
effects on anuran species abundances. However, all ponds had fish and the
presence or absence of fish likely has an effect on anuran abundances (Holbrook
and Dorn 2016, Porej and Hetherington 2005). Detecting fish can be challenging
and our sampling methods were likely insufficient. Future studies could perform
more rigorous comparisons of fish-niche selection and anuran abundances in a connected
wetland system.
Beavers are ecosystem engineers (Wright et al. 2002), so it should not be surprising
that they had an effect on habitat usage in other species. Beavers were
strongly correlated with turtles and Southern Leopard Frogs. To a lesser extent,
turtles correlated with Southern Leopard Frogs, but these 2 species rarely interact
(turtles occasionally consume anurans), indicating that this correlation is a result
of both species’ affinity for Beavers. Turtles likely enjoy the open waterways that
Beavers create with channels and dams, and Southern Leopard Frogs probably benefit
from the habitat heterogeneity closer to shore. Beavers are also associated with
higher plant species richness, indicating that they create desirable wetland habitat
for a variety of species. The widespread effects of Beavers on a wetland have a
positive influence on anuran and other wetland species habitat u sage.
Overwintering anuran microhabitat preferences in a network of northwest
Florida ponds was influenced by predator avoidance and plant species richness.
Behavioral adaptations to threats are unique for each species and, therefore, assemblage
preferences were also unique between different species. Our results suggest
predator-evasion strategy is a key driver of microhabitat selection in anurans.
Acknowledgments
We thank M. Bowman and A. Watson for their local expertise on amphibians and plants
of northwestern Florida. A. Ahlers’ suggestions throughout the editing process were invaluable.
We are grateful to Pensacola Christian College for the use of their facilities for this
study. A large part of this research was completed in partial fulfillment of a Master of Science
degree at the University of Nebraska at Kearney .
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2019 Vol. 18, No. 2
Literature Cited
Adams, C.K., and D. Saenz. 2012. Leaf litter of invasive Chinese Tallow (Triadica sebifera)
negatively affects hatching success of an aquatic breeding anuran, the Southern Leopard
Frog. Canadian Journal of Zoology 90:991–998.
Alix, D.M., C.J. Anderson, J.B. Grand, and C. Guyer. 2014. Evaluating the effects of
land use on headwater wetland amphibian assemblages in coastal Alabama. Wetlands
34:917–926.
Almeida–Gomes, M., and C.F.D. Rocha. 2015. Habitat loss reduces the diversity of frog
reproductive modes in an Atlantic forest fragmented landscape. Biotropica 47:113–118.
Andersen, L.W., K. Fog, and C. Damgaard. 2004. Habitat fragmentation causes bottlenecks
and inbreeding in the European Tree Frog (Hyla arborea). Proceedings of the Royal
Society B: Biological Sciences 271:1293–1302.
Baldwin, R.F., A.J.K. Calhoun, and P.G. deMaynadier. 2006. Conservation planning for amphibian
species with complex habitat requirements: A case study using movements and
habitat selection of the Wood Frog, Rana sylvatica. Journal of Herpetology 40:442–453.
Baskale, E., and D. Çapar. 2016. Detection probability and habitat selection of the Beysehir
Frog, Pelophylax caralitanus (Arikan 1988), in southwestern Anatolia, Turkey. Russian
Journal of Herpetology 23:205–214.
Bateman, P.W., and P.A. Fleming. 2014. Living on the edge: Effects of body size, group
density, and microhabitat selection on escape behavior of Southern Leopard Frogs,
Lithobates sphenocephalus. Current Zoology 60:712–718.
Bayless, L.E. 1969. Ecological divergence and distribution of sympatric Acris populations
(Anura: Hylidae). Herpetologica 25:181–187.
Beaty, L.E. 2017. Latent effects of larval experience: The pervasive effects of tadpole
predation risk on frog phenotype. Ph.D. Dissertation. Oklahoma State University, Stillwater,
OK.
Becker, C.G., C.R. Fonseca, C.F.B. Haddad, R.F. Batista, and P.I. Prado. 2007. Habitat split
and the global decline of amphibians. Science 318:1775–1777.
Bickford, D., T.H. Ng, L. Qie, E.P. Kudavidanage, and C.J.A. Bradshaw. 2010. Forest
fragment and breeding habitat characteristics explain frog diversity and abundance in
Singapore. Biotropica 42:119–125.
Blaustein, R.J. 2008. Biodiversity hotspot: The Florida Panhandle. BioScience 58:784–790.
Blihovde, W.B. 2006. Terrestrial movements and upland habitat use of Gopher Frogs in
Central Florida. Southeastern Naturalist 5:265–276.
Buxton, V.L., M.P. Ward, and J.H. Sperry. 2017. Frog breeding pond-selection in response
to predators and conspecific cues. Ethology 123:397–404.
Carter, J., D. Johnson, and S. Merino. 2018. Exotic invasive Giant Apple Snails (Pomacea
maculata) will depredate eggs of frog and toad species of the southeastern United States.
Southeastern Naturalist 17(3):470–475.
Cassani, J.R., D.A. Croshaw, J. Bozzo, B. Brooks, E.M. Everham III, D.W. Ceilley, and D.
Hanson. 2015. Herpetofaunal community change in multiple habitats after fifteen years
in a Southwest Florida preserve, USA. PLoS one 10:e0125845.
Catenazzi, A., E. Lehr, L.O. Rodriguez, and V.T. Vredenburg. 2011. Batrachochytrium dendrobatidis
and the collapse of anuran species richness and abundance in the Upper Manu
National Park, Southeastern Peru. Conservation Biology 25:382–3 91.
Chandler, H.C., C.A. Haas, and T.A. Gorman. 2015. The effects of habitat structure on
winter aquatic invertebrate and amphibian communities in pine flatwoods wetlands.
Wetlands 35:1201–1211.
Southeastern Naturalist
C.M. Bomske and N. Bickford
2019 Vol. 18, No. 2
268
Cunningham, J.M., A.J.K. Calhoun, and W.E. Glanz. 2007. Pond-breeding amphibian
species richness and habitat selection in a Beaver-modified landscape. The Journal of
Wildlife Management 71:2517–2526.
Cushman, S.A. 2006. Effects of habitat loss and fragmentation on amphibians: A review
and prospectus. Biological Conservation 128:231–240.
De Oliveira, I.S., V.M. Ribeiro, E.R. Pereira, and J.R.S. Vìtule. 2016. Predation on native
anurans by invasive vertebrates in the Atlantic rain forest, Brazil. Oecologia Australis
20:70–74.
Delis, P.R., H.R. Mushinsky, and E.D. McCoy. 1996. Decline of some west-central Florida
anuran populations in response to habitat degradation. Biodiversity and Conservation
5:1579–1595.
Erwin K.J., H.C. Chandler, J.G. Palis, T.A. Gorman, and C.A. Haas. 2010. Herpetofaunal
communities in ephemeral wetlands embedded within Longleaf Pine flatwoods of the
Gulf Coastal Plain. Southeastern Naturalist 15:431–447.
Fardell, L., J. Valdez, K. Klop-Toker, M. Stockwell, S. Clulow, J. Clulow, and M. Mahony.
2018. Effects of vegetation density on habitat suitability for the endangered Green and
Golden Bell Frog, Litoria aurea. Herpetological Conservation and Biology 13:47–57.
Farrell, T.M., M.A. Pilgrim, P.G. May, and W.B. Blihovde. 2011. The herpetofauna of Lake
Woodruff National Wildlife Refuge, Florida. Southeastern Naturalist 10:647–658.
Fellers, G.M., and P.M. Kleeman. 2007. California Red-legged Frog (Rana draytonii)
movement and habitat use: Implications for conservation. Journal of Herpetology
41:276–286.
Ficetola, G.F., C. Rondinini, A. Bonardi, D. Baisero, and E. Padoa-Schioppa. 2015. Habitat
availability for amphibians and extinction threat: A global analysis. Diversity and Distributions
21:302–311.
Gallant, A.L., R.W. Klaver, G.S. Casper, and M.J. Lannoo. 2007. Global rates of habitat
loss and implications for amphibian conservation. Copeia 2007:9 67–979.
Google Maps. 2018. West Campus. Available online at https://www.google.com/
maps/@30.3926808,–87.425471,667m/data=!3m1!1e3. Accessed 6 August 2018.
Gorman, T.A., and C.A. Haas. 2011. Seasonal microhabitat selection and use of syntopic
populations of Lithobates okaloosae and Lithobates clamitans clamitans. Journal of
Herpetology 45:313–318.
Goulet, C.L., H.J. Smith, and T. Maie. 2016. Comparative lever analysis and ontogenetic
scaling in esocid fishes: Function demands and constraints in feeding biomechanics.
Journal of Morphology 277:144–1458.
Grand, L.A., M.P. Hayes, K.A. Vogt, D.J. Vogt, P.R. Yarnold, K.O. Richter, C.D. Anderson,
E.C. Ostergaard, and J.O. Wilhelm. 2017. Identification of habitat controls on Northern
Red-legged Frog populations: Implications for habitat conservation on an urbanizing
landscape in the Pacific Northwest. Journal of Herpetology 45:31 3–318.
Guzy, J.C., E.D. McCoy, A.C. Deyle, S.M. Gonzalez, N. Halstead, and H.R. Mushinsky.
2012. Urbanization interferes with the use of amphibians as indicators of ecological
integrity of wetlands. Journal of Applied Ecology 49:941–952.
Harper, E.B., T.A. G. Rittenhouse, and R.D. Semlitsch. 2008. Demographic consequences
of terrestrial habitat loss for pool-breeding amphibians: Predicting extinction risks associated
with inadequate size buffer zones. Conservation Biology 22:1205–1215.
Holbrook, J.D., and N.J. Dorn. 2016. Fish reduce anuran abundance and decrease herpetofaunal
species richness in wetlands. Freshwater Biology 61:100– 109.
Kerby, J.L., K.L. Richards–Hrdlicka, A. Storfer, and D.K. Skelly. 2010. An examination of
amphibian sensitivity to environmental contaminants: Are amphibians poor canaries?
Ecology Letters 13:60–67.
Southeastern Naturalist
269
C.M. Bomske and N. Bickford
2019 Vol. 18, No. 2
Lagler, K.F., and F.V. Hubbs. 1940. Food of the Long-nosed Gar (Lepomis osseus oxyurus)
and the Bowfin (Amia calva) in southern Michigan. Copeia 1940:239–241.
Lamb, T. 1984. The influence of sex and breeding condition on microhabitat selection and
diet in the Pig Frog, Rana grylio. American Midland Naturalist 111:311–318.
Lannoo, M.J. (Ed.). 2005. Amphibian Declines: The Conservation Status of United
States Species. University of California Press, Berkeley, CA. DOI:10.1525/California/
9780520235922.001.0001
Lehtinen, R.M., S.M. Galatowitsch, and J.R. Tester. 1999. Consequences of habitat loss and
fragmentation for wetland amphibian assemblages. Wetlands 19:1–12.
Niemi, G.J., J.R. Kelly, and N.P. Danz. 2007. Environmental indicators for the coastal region
of the North American Great Lakes: Introduction and prospects. Journal of Great
Lakes Research 33:1–12.
Pitt, A.L., J.J. Tavano, R.F. Baldwin, and B.S. Stegenga. 2017. Movement ecology and
habitat use of three sympatric anuran species. Herpetological Conservation and Biology
12:212–224.
Porej, D, and T.E. Hetherington. 2005. Designing wetlands for amphibians: The importance
of predatory fish and shallow littoral zones in structuring of amphibian communities.
Wetlands Ecology and Management 13:445–455.
Regosin, J.V., B.S. Windmiller, and J.M. Reed. 2003. Terrestrial habitat use and winter
densities of the Wood Frog (Rana sylvatica). Journal of Herpetology 37:390–394.
Sasaki, K., D. Lesbarréres, G. Watson, and J. Litzgus. 2015. Mining-caused changes to
habitat structure affect amphibian and reptile population ecology more than metal pollution.
Ecological Applications 25:2240–2254.
Schalk, C.M., T.M. Luhring, and B.A. Crawford. 2010. Summer microhabitat use of the
Greater Siren (Siren lacertian) and Two–toed Amphiuma (Amphiuma means) in an isolated
wetland. Amphibia-Reptilia 31:251–256.
Shulse, C.D., R.D. Semlitsch, K.M. Trauth, and J.E. Gardner. 2012. Testing wetland features
to increase amphibian reproductive success and species richness for mitigation and
restoration. Ecological Applications 22:1675–1688.
Ugarte, C.A., K.G. Rice, and M.A. Donnelly. 2007. Comparison of diet, reproductive biology,
and growth of the Pig Frog (Rana grylio) from harvested and protected areas of the
Florida Everglades. Copeia 2007:436–448.
Villena, O.C., J.A. Royle, L.A. Weir, T.M. Foreman, K.D. Gazenski, and E.H.C. Grant.
2016. Southeast regional and state trends in anuran occupancy from calling-survey data
(2001–2013) from the North American Amphibian Monitoring Program. Herpetological
Conservation and Biology 11:373–385.
Welsh, H.H., Jr., and L.M. Ollivier. 1998. Stream amphibians as indicators of ecosystem
stress: A case study from California’s redwoods. Ecological Applications 8:1118–1132.
Werner, E.E., and M.A. McPeek. 1994. Direct and indirect effects of predators on two anuran
species along an environmental gradient. Ecology 75:1368–1 382.
Werner, E.E., D.K. Skelly, R.A. Relyea, and K.L. Yurewicz. 2007. Amphibian species richness
across environmental gradients. Oikos 116:1697–1712.
Wiens, J.J. 2007. Global patterns of diversification and species richness in amphibians. The
American Naturalist 170:S86–S106.
Wright, J.P., C.G. Jones, and A.S. Flecker. 2002. An ecosystem engineer, the Beaver, increases
species richness at the landscape scale. Oecologica 132 :96–101.