USE OF NATURAL AND ARTIFICIAL VERNAL POOLS BY SEMI-AQUATIC
SALAMANDERS IN THE CUMBERLAND REGION OF JACKSON COUNTY,
ALABAMA
by
CHELSEA NICHOLE SCOTT
A THESIS
Submitted in partial fulfillment of the requirements
for the degree of Master of Science
in the Department of Natural Resources and Environmental Science
in the School of Graduate Studies
Alabama A & M University
Normal, AL 35762
OCTOBER 2008
Submitted by CHELSEA NICHOLE SCOTT in partial fulfillment of the
requirements for the degree of MASTER OF SCIENCE specializing in NATURAL
RESOURCES AND ENVIRONMENTAL SCIENCE.
Accepted on the behalf of the Faculty of the Graduate School by the Thesis
Committee:
_____________________________
_____________________________
_____________________________
_____________________________
_____________________________ Major Advisor
__________________________________ Dean of the Graduate School
__________________________________ Date
ii
Copyright by
CHELSEA NICHOLE SCOTT
2008
iii
USE OF NATURAL AND ARTIFICIAL VERNAL POOLS BY SEMIAQUATIC SALAMANDERS IN THE CUMBERLAND REGION OF
JACKSON COUNTY, ALABAMA
Scott, Chelsea N., M.S., Alabama A&M University, 2008. 110 pp.
Thesis Advisor: Yong Wang
Vernal pools occur naturally in most forests but can be created by land managers
for various management purposes. Semi-aquatic salamanders depend on these temporary
pools to fill with water and remain wet most of the winter and spring. However, the
actual use of these pools by salamanders had not been quantified in Alabama. The
overall objective of this study was to examine the use of vernal pools by breeding
salamanders in Jackson County, Alabama and to compare the suitability of natural and
artificial pools as breeding habitat for pool breeding salamanders. Habitat variables
within pools and surrounding pools, hydrology, and water chemistry were monitored at
twenty pools in Jackson County, Alabama through biweekly visual surveys and weekly
sampling with minnow traps. Drift fences and pit fall traps were installed at six of these
pools, three natural and three artificial, to monitor salamander activity. Environmental
conditions and microhabitat variables at natural and artificial pools were significantly
different between natural and artificial pools when compared using all twenty pools.
Artificial pools tended to be larger, deeper, and located at lower elevations. Artificial
pools also had a higher pH than natural pools. Five pool- breeding species were
encountered as well as four terrestrial species. The Spotted Salamander (Ambystoma
maculatum) was the most abundant of the pool breeding species, accounting for 43% of
captures and the Four-toed Salamander (Hemidactylium scutatum) was the rarest,
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accounting for only 2% of captures. Species diversity and community composition were
similar between natural and artificial pools. Mole salamanders (A. talpoideum) had
significantly longer bodies and tails in artificial pools and Marbled salamanders (A.
opacum) had significantly longer bodies and tails and weighed more at natural pools.
Four-toed salamanders also had significantly longer bodies at natural pools.
v
TABLE OF CONTENTS
CERTIFICATE OF APPROVAL………………………………………………………...ii
ABSTRACT…...…………………………………….…………………………………...iv
LIST OF TABLES……………………………………………………………………...viii
LIST OF FIGURES……………………………………………………………………...xi
AKNOWLEDGMENTS…………………………………………………………..…….xiv
CHAPTER 1- INTRODUCTION…………………………………………………………1
Statement of Problem……………………………………………………………...1
Objectives of Study………………………………………………………………..4
Hypotheses………………………………………………………………………...4
Significance of Study……………………………………………………………...6
CHAPTER 2- LITERATURE REVIEW………………………………………………….8
Vernal Pool Ecology………………………………………………………………8
Salamander Ecology……………………………………………………………..11
Cumberland Plateau in Northern Alabama………………………………………16
Conservation of Amphibians…………………………………………………….17
Description of Common Salamander Species in the Study Area………………..24
CHAPTER 3- METHODOLOGY……………………………………………………….30
Study Site………………………………………………………………………...30
Study Pool Selection..........………………………………………………………32
Water Chemistry and Environmental Parameters……………………….……….34
Monitoring Salamanders…………………………………………………………36
Data Analyses...………………………………………………………………….41
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CHAPTER 4- RESULTS……………………………………………………………...…43
Characteristics of Natural and Artificial Pools…………………………………..43
Species Richness and Abundance………………………………………………..55
Species Diversity…………………………………………………………….…..60
Spatial Distribution and Temporal Patterns…………………………………..….62
Community Similarities………………………………………………………….73
Canonical Correspondence Analysis (CCA)…………………………………….78
CHAPTER 5- DISCUSSION……………………………………………………………84
Environmental Conditions and Environmental Factors………………………….84
Artificial Pools as Suitable Habitats…..................................................................90
CHAPTER 6- CONCLUSION AND RECOMMEDATIONS…………………………..97
LITERATURE CITED…………………………………………………………………101
VITA
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LIST OF TABLES
TABLE
Page
4.1. Comparisons of biophysical features of artificial and natural vernal pools at the
James D. Martin Skyline Wildlife Management Area and the Walls of Jericho
Forever Wild property on the southern extent of Cumberland Plateau in Jackson
County, Alabama…………………………………………………………………….44
4.2. Comparisons of biophysical features of artificial and natural vernal pools selected
for intensive drift fence trapping at the James D. Martin Skyline Wildlife
Management Area and the Walls of Jericho Forever Wild property on the southern
extent of Cumberland Plateau in Jackson County, Alabama………………………...45
4.3. Comparison of MANOVAs comparing microhabitat variables (percent coverage)
between at natural and artificial vernal pools in Jackson County, Alabama…...……49
4.4. Comparison of microhabitat variables (percent coverage) between natural and
artificial vernal pools selected for intensive drift fence trapping in Jackson County,
Alabama…...…………………………………………………………………………50
4.5. Description of twenty vernal pools at the James D. Martin Skyline Wildlife
Management Area and the Walls of Jericho Forever Wild property on the southern
extent of Cumberland Plateau in Jackson County, Alabama………………………...51
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4.6. Description of average water conditions at twenty vernal pools at the James D.
Martin Skyline Wildlife Management Area and the Walls of Jericho Forever Wild
property on the southern extent of Cumberland Plateau in Jackson County,
Alabama………………………………………………………………………….......52
4.7. Species richness and relative abundance of drift fence and minnow trap captures
between February 2007 and July 2008 (8,850 Total Captures) ……………………..54
4.8. Comparisons of total captures at artificial and natural vernal pools at the James D.
Martin Skyline Wildlife Management Area and the Walls of Jericho Forever Wild
property on the southern extent of Cumberland Plateau in Jackson County,
Alabama…...…………………………………………………………………………57
4.9. Comparisons of individual captures (total captures excluding adults traveling out) at
artificial and natural vernal pools at the James D. Martin Skyline Wildlife
Management Area and the Walls of Jericho Forever Wild property on the southern
extent of Cumberland Plateau in Jackson County, Alabama …………………...…...57
4.10. Adults captured by drift fences and minnow traps at intensively studied vernal
pools in Jackson County, Alabama between February 2007 and July
2008……………………………………………………………………….…………58
4.11. Emergent and metamorph drift fence and minnow trap captures at intensively
studied vernal pools in Jackson County, Alabama between February 2007 and July
2008………………………………………………………………………………….59
4.12. Diversity indices of the fenced natural and artificial pools using total
captures……………………………………………………………………………..61
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4.13. Diversity indices of the fenced natural and artificial pools using only adults
traveling into pools, emergent, and metamorph captures……………………….…..61
4.14. Comparison of averaged Morisita’s Index of Similarity index scores for fenced
natural and artificial pools………………………………………………………….75
4.15. Comparison on averaged Morisita’s Index of Similarity scores for fenced natural
and artificial pools excluding adults traveling out of pools……..………………….75
4.16. MANOVA comparing SVL, tail length, and weight of adults of each species
captured at fenced pools…………………………….................................................76
4.17. MANOVA comparing SVL, tail length, and weight of emergents and metamorphs
of each species captured at fenced pools………….................................................77
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LIST OF FIGURES
FIGURE
Page
3.1. James D. Martin Skyline Wildlife Management Area and Forever Wild
Property located in northern Jackson County, Alabama……...……………………...31
3.2. Vernal pool locations in the Skyline WMA and Forever Wild Property in
Jackson County, Alabama…………………….……………………………………...33
3.3. Schematic for the set-up of drift fences at an artificial pool………………………..37
3.4. Schematic for the set-up of drift fences at a natural pool…………………………..38
4.1. Hydroperiod of natural vernal pools in Jackson County, Alabama between
January 2007 and July 2008………………..………………………………………...47
4.2. Hydroperiod of artificial vernal pools in Jackson County, Alabama between
January 2007 and July 2008……………………………………………………….....47
4.3. Total salamander captures per month between February 2007 and July 2008 at
fenced natural pools in Jackson County, Alabama….……………………………….55
4.4. Total salamander captures per month between February 2007 and July 2008 at
fenced artificial pools in Jackson County, Alabama………………………………...55
4.5. Drift fence and minnow trap captures by pool in Jackson County, Alabama.
Includes total adult, emergent, and metamorph captures…………………………….64
4.6.Total captures of Spotted salamanders at natural (n= 3) and artificial (n= 3)
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pools in Jackson County, Alabama……………………………………………..…....66
4.7. Total captures of Marbled salamanders at natural (n= 3) and artificial (n= 3)
pools in Jackson County, Alabama …………………………………………….........67
4.8. Total captures of Four-toed salamanders at natural (n= 3) and artificial (n= 3)
pools in Jackson County, Alabama …………………………………………….........69
4.9. Total captures of Red-spotted newts at natural (n= 3) and artificial (n= 3)
pools in Jackson County, Alabama ………………………………………….............70
4.10. Total captures of Mole salamanders at natural (n= 3) and artificial (n= 3)
pools in Jackson County, Alabama …………………………………………….........71
4.11.Relationships between pool environmental features (Max Depth, Distance to Edge,
and Origin) and salamanders captured based on canonical correspondence
analysis……………………………………………………………………………….79
4.12. Relationships between pool environmental features (Conductivity, Max Depth,
Distance to Edge, and Origin and salamanders captured based on canonical
correspondence analysis …………………………………………………...……….81
4.13. Relationship between pool environmental features in spring and salamander
captures based on the first and second canonical correspondence axes...………….82
4.14. Relationship between pool environmental features in spring and salamander
captures based on the second and third canonical correspondence axes...…...…….83
4.15. Relationship between pool environmental features in spring and salamander
captures based on the first and third canonical correspondence axes.……......…….83
6.1. Diversity indices as related to the age of fenced artificial pools in Jackson
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County, Alabama...………………………………………………………………….99
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ACKNOWLEDGMENTS
I would like to thank my committee members: Drs. Yong Wang, Callie
Schweitzer, Robert Lawton, William Stone, and J. Drew Lanham for their guidance and
support of my graduate study and thesis research. I would like to acknowledge Zachary
Felix and Jeff Crocker’s early monitoring work of vernal pool breeding amphibians in
Jackson County and thank them for their insights and help in initiating this study. I thank
Brandon Haslick, Becky Hardman, and Rachel Bru Bolus for their field and technical
assistance. I would also like to thank my undergraduate assistants: Seward Hamilton,
Brian Norris, Jeanette Williams, Steven Gaither, and Derek Hemsley for helping with
field data collection. I greatly appreciate the support and friendship of my fellow
graduate students and the staff and faculty in the Department of Natural Resources and
Environmental Sciences, especially: Florence Chan, Kelvin Young, Meiko Thompson,
Nevia Brown, Timothy Baldwin, William Sutton, Lisa Gardener, Dawn Lemke, Allison
Bohlman, and Drs. Caula Beyl and Rory Fraser. I thank the Lands Division of the
Alabama Department of Natural Resources and Conservation (ALDNRC) for letting me
use the study site and Nick Sharp and Frank Allen from ALDNRC for their assistance in
locating vernal pools. Special thanks go to Jim Schrenkel, who provided historical
information concerning pools and was responsible for the construction of many of the
artificial pools at the study site. My graduate study and thesis research were supported by
xiv
the National Science Foundation through the Center for Forest Ecosystem Assessment at
Alabama A&M University and Southern Research Station of USDA Forest Service, and I
thank them for their financial support.
xv
INTRODUCTION
Statement of Problem
Vernal or temporary pools are seasonal wetlands which are covered with water for
variable periods during the winter and spring by shallow waters but may be completely
dry during the summer and fall (Colburn, 2004). They occur naturally in most forests,
but can also be man-made. Vernal pools are ideal for studying the relationship between
salamanders and the environment because many semi-aquatic salamanders congregate in
them during breeding seasons (DiMauro and Hunter, 2002).
In northern Alabama, artificial pools are sometimes placed on government lands
to prevent flooding in certain areas by providing a place for water to drain (Frank Allen,
AL Department of Conservation and Natural Resources, personal communication). They
are also placed parallel to game plots which are used to attract deer, turkey, and other
wildlife during hunting seasons. A dam made of compacted soil and earth at one end of
the pool keeps the water from flowing out. Opposite of the game plot, the other side of
the pool is usually forested. In addition to serving as flood prevention and along side
game plots, these pools are sometimes installed to attract amphibians (Jim Schrenkel,
Natural Resources and Conservation Service, personal communication). But unlike
natural pools, some artificial pools retain water for most of, if not all year round. Most
natural pools are usually dry during the summer and most of the fall, which eliminates the
1
presence of fish that would prey upon the salamanders and their larvae and also prevents
the accumulation of disease-causing organisms in the water (OVPA, 2006).
Only a few studies compared the use of natural and artificial pools by breeding
amphibians in other parts of the country (DiMauro and Hunter, 2002; Calhoun et al.,
2003) and a study of this kind has yet to be conducted on the southern Cumberland
Plateau in Jackson County, AL. Results from a study conducted on wood frogs (Rana
sylvatica) and spotted salamanders (Ambystoma maculatum) in Maine suggested that
natural pools produce larger emerging metamorphs which results in salamanders reaching
sexual maturity at an earlier age (DiMauro and Hunter, 2002). Their study also suggested
that some species have the ability to successfully colonize artificial pools, and though
metamorphs may have to emerge earlier, they were able to adjust to the altered conditions
of man-made pools (DiMauro and Hunter, 2002). Another study which evaluated vernal
pools as a basis for conservation strategies, also conducted in Maine, showed that in
highly disturbed areas where over seventy percent of the pools are artificial, amphibians
bred in less favorable conditions (Calhoun et al., 2003). Two of the three indicator
species studied, the wood frog and the ambystomatid salamander (Ambystoma lateralejeffersonianum complex), were found in 47% of the pools in the highly and moderately
disturbed study areas and the wood frog, without the ambystomatid salamander, was
found in an additional 3% of pools in the same area (Calhoun et al., 2003).
A study conducted on the National Bison Range in Montana utilized concrete and
fiberglass tanks to simulate artificial environments (Braun, 2006). Ambystoma larvae
were found in artificial pools with larger circumferences and close proximities to other
2
pools also containing larvae, pools that had higher levels of aquatic vegetation, and pools
which had a lower distance from the ground as artificial tanks were constructed above
ground level (Braun, 2006). Salamanders were also the only amphibian which utilized
both natural and artificial pools in the study area (Braun, 2006). These results highlight
the opportunistic breeding abilities of some salamander species. In a study conducted in
western North Carolina, artificial pools seemed to be more suitable for amphibians than
natural pools (Petranka et al., 2003). Constructed pools were studied for five years and
over that time were larger, deeper, warmer, more oxygen-rich and boasted longer
hydroperiods than the natural pools studied in that area (Petranka et al., 2003). Seven
amphibian species colonized these pools within the first year of their construction,
including the spotted salamander and the eastern newt (Petranka et al., 2003). This again,
suggests that the conditions at a pool rather than its origin dictate its suitability as
salamander breeding habitat.
My study of artificial and natural pools in the Cumberland Plateau region of
Jackson County, AL, builds on and compliments these studies conducted in other
ecosystems. By comparing salamander communities and activity occurring at the
artificial pools to that occurring at the natural pools, I quantified the use of these artificial
pools by different salamander species, identified the length of the breeding season, and
gathered preliminary data on the overall salamander usage of these pools during the
breeding season. By assessing the species richness and relative abundance of
salamanders at these pools, I hoped to determine if artificial pools were equally important
to the salamanders relative to the natural pools.
3
Objectives of Study
(1) Determine the species richness, relative abundance, and breeding phenology of vernal
pool breeding salamanders in natural and artificial vernal pools in Jackson County, AL.
(2) Examine the breeding ecology of vernal pool breeding salamanders in natural and
artificial pools in Jackson County, AL.
(3) Determine the effectiveness of artificial pools as salamander breeding habitat and
possible conservation strategies in Jackson County, AL.
Hypotheses
Hypothesis 1: Environmental conditions will have a significant effect on the use of vernal
pools by breeding salamanders.
(1-A) Vernal pool hydrology, regardless of a pool’s origin (natural or artificial), will
determine species presence. Amphibians select breeding pools during the breeding
season based on the availability of pools in a given area. Some species require pools with
a longer hydroperiod while others require pools that remain wet for a shorter period of
time. The species composition of each pool will be a reflection of its hydrological
period.
(1-B) The hydrology of the vernal pools will be the most important factor determining
amphibian breeding success in both artificial and natural pools. Drying of pools before
metamorphs can emerge will result in mortality among all species.
(1-C) The denser the vegetation within and around the pool, the more successful the
larvae will be. Submerged vegetation attracts food sources of developing larvae and
4
serves as cover from predators. The vegetation may also provide a favorable
environment for egg-laying in the water.
Hypothesis 2: Some artificial pools will be capable of serving as suitable breeding
habitats while others with less favorable conditions will not.
(2-A) Because natural pools are my reference and I am assuming them as the standard for
suitable habitat, I feel that artificial pools with similar biophysical conditions of the
natural pools will be used by salamander populations and support developing larvae.
(2-B) Artificial pools that have not been colonized by plants common to natural
temporary pools in the area and that are in unfavorable or isolated areas will not be
suitable for salamanders seeking breeding sites and therefore will show a lower
abundance of salamanders. Most artificial pools in the area are watering holes for game
species excavated by forest managers near cleared or thinned areas and food plots in
hunting areas. These pools have minimal vegetation and are only partially surrounded by
fully intact and mature forest. Artificial pools of this type will also have lower relative
abundance than natural pools.
Hypothesis 3: Natural pools will display greater species richness, relative abundance,
individual fitness, breeding populations, and overall pool usage than artificial pools.
(3-A) Natural pools are the innate breeding habitat of these salamanders. Natural pools
in the study area are well-vegetated, surrounded by forest, and in primarily undisturbed
(away from major roads and hunting areas) locations. For these reasons, they should
have the greater diversity and higher species richness and relative abundance when
compared to artificial pools.
5
Significance of the study
Because of their complicated life-cycles, amphibians are sensitive to changes in
their environment. Amphibian species abundance, presence, or absence can indicate the
health of an ecosystem. Therefore, salamanders are important bio-indicator species
(Davic and Welsh, 2004). In addition to being bio-indicators, salamanders play several
important roles in the forest ecosystem in which they reside. They are essential to energy
transfer between terrestrial and aquatic habitats by serving as prey and an energy source
for both aquatic and terrestrial consumers (Davic and Welsh, 2004). They are also
regulatory predators, feeding on other organisms such as mosquito larvae that may
otherwise reproduce unchecked and become a problem for the ecosystem as well as
humans.
We can determine how well artificial pools fill the ecological needs of
salamanders by examining their ability to survive and reproduce in vernal pools. Many
artificial pools are constructed as drainage solutions and create breeding habitat for pool
breeding amphibians. The use of these pools by breeding amphibians is rarely monitored
for their actual suitability as salamander habitats. By monitoring and comparing artificial
pools to natural pools in the same area, it can be determined if they are effective as a
conservation tool. A study in Minnesota which compared species richness in established
wetlands to species richness in restored wetlands, found that sixty-seven percent of
species present in established wetlands were also re-colonizing restored wetlands
(Lehtinen and Galatowitsch, 2001). If artificial pools are found to be suitable, they can
possibly be constructed to fulfill the habitat requirements of specific species. Juvenile
6
amphibians disperse to seek suitable habitats (Rothermel and Semlitsch, 2002), so if
artificial pools can be constructed to meet the species’ requirements, it is likely that
salamanders will colonize the area.
7
LITERATURE REVIEW
Vernal Pool Ecology
Vernal pools, also known as “ephemeral ponds,” “autumnal pools,” or simply
“temporary pools,” are usually isolated wetlands characterized by a wet season in which
they are temporarily filled with water, a lack of predatory fish, and a unique herbaceous
vegetation composition (Colburn, 2004). These ecosystems are found in a variety of
landscapes and can occur naturally or have artificial origins. Depending on topography
and regional precipitation (Keeley and Zelder, 1998), they can fill with water via several
sources including rainfall, surface run-off, flooding from nearby bodies of water, ground
water, and intermittent stream flow (Colburn, 2004). Keeley and Zelder (1998) described
vernal pools as having four phases: a wetting phase, an inundation phase, a waterloggedterrestrial phase, and finally, a drought phase. During the wetting phase, moisture collects
in the layers of clay beneath leaf litter, causing the topsoil to swell and become
impermeable to water (Ferren, 2005). Clay particles are small and flat, allowing them to
remain close together and resulting in the impermeability of clay layers (Ferren, 2005).
Inundation occurs as the rate of water input via various sources exceeds the rate of water
loss, primarily through evapotranspiration (Zelder, 1987). The brief waterloggedterrestrial phase occurs after the water moves from the pool via downward percolation or
evapotranspiration. Finally, the process is culminated in the extreme desiccation of the
8
soil during the drought phase (Zelder, 1987). In northern Alabama, the wetting phase
generally begins in mid December and pools are normally completed inundated by mid
May.
Several factors contribute to the ecology of vernal pools. Characteristics such as
pool area, hydrology, extent of flooding, substrate and surface soil type, surrounding
vegetation, vegetation within pools, and landscape setting all contribute to the ecology of
a vernal pool (Colburn, 2004). The vegetation present varies regionally, but regardless of
location, the plants must be able to survive wet and dry conditions. The standing water
prevents the growth of plants from the surrounding uplands and the regular drying of the
pools prevents the growth of permanent marsh species (Zelder, 2003).
Temperature, pH, conductivity, salinity, and dissolved oxygen are all defining
characteristics of a vernal pool and are the most common aspects of a pool’s water
chemistry assessed in vernal pool studies (Renz and Higgins, 2006). Renz and Higgins
(2006) attributed variation in these parameters to variation in precipitation and several
other factors at a given pool. Temperature is often affected by the large surface area to
volume ratio which causes some pools to undergo extreme temperature fluctuations over
the course of the day (Keeley and Zelder, 1998). pH is most often affected by the lack of
nutrients in vernal pools due to most pools’ dependency on rain water (Keeley, 1991).
Major nutrients that can be found in these pools include but are not limited to nitrogen,
phosphorous, calcium, sodium, sulfur, magnesium, silicon, and potassium (Deas and
Orlob, 1999). But it is carbon, specifically inorganic carbon compounds, which impact
pH levels (Deas and Orlob, 1999). Fresh water, like the precipitation that mainly fills
9
these pools, can lack these compounds (e.g. bicarbonates) in excess, leaving vernal pool
waters largely unbuffered against major fluctuations in dissolved oxygen and carbon
(Keeley, 1991; Keeley and Zelder, 1998). As the day progresses and light and
temperature levels increase, photosynthesis increases to the point where it inhibits itself
due to low levels of carbon dioxide (Keeley and Zelder, 1998). pH depends greatly on
the carbon dioxide-bicarbonate system which is the major buffering system for the acidbase balance. The carbon dioxide-bicarbonate system is the exchange of carbon dioxide
between pool waters and the air which results in the formation of carbonic acid (Kimball,
2008). Once in the aquatic system, carbonic acid breaks down and releases hydrogen and
bicarbonate ions (Kimball, 2008). Low levels of carbon dioxide due to increased
photosynthesis can inhibit this process and cause pH to rise two to three units over the
course of the day (Keeley and Zelder, 1998). Fluctuations in dissolved oxygen can also
be attributed to this process (Keeley and Zelder, 1998). Conductivity and salinity are
usually proportional to the ion concentration of a system and are normally maintained in
lower levels in aquatic systems, but often increase as pools dry and ions are concentrated
(Keeley and Zelder, 1998).
Optimum levels of pH and dissolved oxygen for aquatic life in freshwaters are
6.5-9.0 and 5-11 parts per million (ppm) or 80-125% saturation, respectively (Alabama
Water Watch, 2006). The ideal range for conductivity in freshwater inlands is between
150 and 1500 microsiemans (µS), but waters commonly range from 50-1500 µS (Behar).
For salinity, water with a salt level less than 1,000 ppm or between 0 and .5 parts per
thousand (ppt) is considered freshwater (Behar). Levels outside of these ranges can cause
10
egg and larval mortality, bacteria facilitated oxygen depletion in water, reduced
fertilization, and even developmental abnormalities (Pough and Wilson, 1976; Alabama
Water Works, 2006; Marks, 2006).
Vernal pools are important to amphibians. They allow species which would be
eaten by fish to avoid predation during breeding and during the early developmental
stages of their offspring (Langlois, 2003). Vernal pools support obligate species, which
depend on vernal pools during some stage in their reproduction or development. Many of
these species have adapted to the annual drying of these pools and therefore can not
utilize more permanent breeding habitats (Grant, 2005). Facultative species, on the other
hand, do not depend on vernal pools, but have shown a preference for them as breeding
habitat (Grant, 2005). Vernal pools are also important in the nutrient cycle of an
ecosystem (Langlois, 2003). As leaves collect at the base of pools, they provide nutrition
for developing species and microorganisms. This supports the secondary consumers (e.g.
juvenile and adult salamanders) by providing them with an adequate source of food. This
process continues through the food chain until decomposers then recycle these nutrients
back into the environment. Vernal pools also place nutrients directly back into the
ecosystem by facilitating the biodegrading of materials which fall into the pools
(Langlois, 2003).
Salamander Ecology
Salamanders are in the taxonomic order Caudata and are a group of amphibians
which are intermittently aquatic or remain aquatic throughout life (Zug et al., 2001).
11
They are characterized as having a biphasic life cycle beginning with an aquatic egg and
larval stages, followed by an aquatic metamorphosis and emergence into a terrestrial
form, and culminated by seasonal migrations back to aquatic habitats to breed and lay
eggs (Dodd et al., 2006). They lack lungs and adults breathe through their skin. Due to
this adaptation, salamanders require an aquatic habitat or at least some amount of
moisture in their environment to live. The salamander species involved in this study are
in the suborder Salamandroidea (Mount, 1975; Dodd, 2003), and most of them require an
aquatic habitat in which to breed and lay eggs. Other species in this Order may not
require a completely aquatic habitat to breed, but still must lay their eggs in a moist
environment. The life span, time to metamorphosis, emergence, and sexual maturity all
vary across species (Dodd et al., 2006).
Salamanders that were encountered in this study were either terrestrial or semiaquatic. Terrestrial salamanders, which are members of the Plethodontidae family, are
the largest salamander family in terms of the number of species classified as such.
Species common to this study area are members of the Genera Aneides and Plethodon,
neither of which requires an aquatic habitat (Zug et al., 2001). They are usually found on
the forest floor under logs and other litter, in rock crevices, and will often burrow
underground. Terrestrial salamanders also lack an aquatic life stage and their young
hatch from eggs laid on land and emerges as miniature adults. Eggs are usually deposited
in underground cavities, within or under decomposing logs and vegetation, or on the
underside of rocks (USGS, 2005). Adults and juveniles will surface during moist
conditions to forage on the forest floor beneath rocks and litter, and in some species, will
12
even forage arboreally (USGS, 2005). Terrestrial salamanders lack lungs and must
respire through their skin, so they must remain in a moist environment at all times
(USGS, 2005). Species common to northern Alabama and some that were encountered in
this study include: the Eastern Zig-zag Salamander (Plethodon dorsalis dorsalis), the
Green Salamander (Aneides aeneus) and Slimy Salamander (Plethodon glutinosus)
(Mount 1975; Mirarchi, 2004).
Semi-aquatic or pond-breeding salamanders spend a portion of their life on land
and a portion in an aquatic phase. Pond-breeding salamanders or lentic salamanders are
usually members of the Ambystomatidae or Salamandridae family (Dodd, 2003). This
group includes stream-breeding salamanders and some members of the Plethodontidae
family (Dodd, 2003). Semi-aquatic salamanders require an aquatic habitat to breed and
often use temporary ponds to breed and lay eggs (Dodd, 2003). Young salamanders
metamorphose in these aquatic habitats and as adults spend a considerable amount of
their life in terrestrial habitats (USGS, 2005). Pond-breeding salamanders are seasonally
active and can be generalized as fall or spring breeders. Breeding is triggered by seasonal
rains (Semlitsch et al., 1993) and is usually a mass event with many individuals of a
single species migrating to a breeding site at once. In addition, the start and duration of
the breeding season is dictated by annual variations in hydroperiod in an attempt to
“maximize offspring success and minimize adult mortality” (Semlitsch et al., 1993).
In addition to terrestrial salamanders and pond-breeding salamanders, there are
several stream-breeding or lotic salamander species in this area. The Southern Dusky
salamander (Desmognathus auriculatus), Dusky salamander (Desmognathus fuscus),
13
Mountain Dusky salamander (Desmognathus ochrophaeus), Cave salamander (Eurycea
lucifuga), and Red salamander (Pseudotriton rubber) (Mount, 1975; Mirarchi, 2004) are
all species common to northern Alabama. But, with the exception of the Red salamander,
none were not encountered in this study, as they prefer smaller streams and seeps. Egg
deposition occurs primarily under stream banks and larval development in these species
also takes place in streams (Mount, 1975). After metamorphosis and emergence,
juveniles and adults remain along streams under leaf litter and in subterranean habitats.
Specific breeding site requirements vary from species to species. But generally,
pond-breeding salamanders utilize temporary ponds which usually fill during winter and
are typically completely dry by mid to late summer (Colburn, 2004). Because they are
dry for approximately two seasons out of the year, these pools are usually fishless
(Colburn, 2004). Occasionally, pools will retain water year round, but due to low oxygen
levels, they too usually lack fish (Stratman, 2000). Ponds with a vegetative community
abundant in sedges and grasses provide refuge and structure for larvae, which is an
important factor in breeding site selection (Colburn, 2004). Another breeding site
requirement is the availability of food. Salamanders and their larvae will mostly
consume arthropods and other aquatic invertebrates, but will also eat tadpoles,
zooplankton, and even other salamander larvae (Marks, 2006). Pond-breeding species
common to northern Alabama include: the Spotted salamander (Ambystoma maculatum),
the Marbled salamander (Ambystoma opacum), the Mole salamander (Ambystoma
talpoideum), and the Four-toed salamander (Hemidactylium scutatum) (Mount 1975,
Mirarchi, 2004, Felix, 2007). The Red-spotted newt (Notophthalmus viridescens
14
viridescens), a subspecies of the Eastern newt (Notophthalmus viridescens), is also
common to this area (Mount, 1975).
Salamanders are very important to the health and maintenance of a habitat in
which they are a part of the ecosystem. They are extremely sensitive to changes in their
environment and therefore provide a valuable service to scientists and forest managers as
a bio-indicator species (Marks, 2006). Salamanders and the eggs that they lay are
vulnerable to surrounding environmental changes because they can easily absorb
chemical pollutants (Marks, 2006). They are also susceptible to ultraviolet radiation,
toxins present in the soil and water, as well as toxic gases present in the air (Marks,
2006). Their population health, fitness, and diversity can be directly correlated to the
health of the surrounding ecosystem (Marks, 2006). Salamanders also serve as an
essential link in the energy chain between terrestrial and aquatic habitats (Davic and
Welsh, 2004). Through their migrations to and from these habitats, they link the food
webs of several communities by serving as prey and predator in both arenas. They also
link aquatic habitats by dispersing organisms during their migrations. Ambystoma spp.,
are known to transport some organisms (i.e. Pisidium adamsi and Bidens cernua),
between habitats (Davic and Welsh, 2004). It is also being examined whether
salamanders can transform certain toxic organic compounds (i.e. pesticides and
chlorohydrocarbons) in aquatic habitats, which would be transmitted into terrestrial
habitats, into less toxic compounds (Davic and Welsh, 2004).
15
Cumberland Plateau of northern Alabama
The Cumberland Plateau is the southernmost portion of the Appalachian Plateau
and covers most of eastern Kentucky, western West Virginia, the central portion of
Tennessee, and small part of northern Alabama (McNab and Avers, 1994). It extends in
a southwestern direction for 724 kilometer and is approximately seventy kilometers wide
(McNab and Avers, 1994). Elevations range from about 100 to 500 meters; the portion
of the plateau located in Alabama is approximately 400 meters above sea level and is
composed mainly of sandstone, limestone, and coal deposits (McNab and Avers, 1994).
Forest cover type of the plateau is typically mixed hardwood forest composed of oakhickory and oak-pine forests, but there are also areas dominated by shortleaf and/or
loblolly pine (McNab and Avers, 1994). Oak species common to the Cumberland
Plateau are Quercus veluntina, Q. rubra, Q. falcata, and Q. alba (McNab and Avers,
1994). Due to its moderately moist environment and its wide range of topographic
conditions, the Cumberland Plateau is one of the most biologically diverse regions in this
temperate zone (Loucks et al., 2001). Diverse forest communities and rich understories
support even more varied faunal communities (Loucks et al., 2001). This region also
boasts a rich ecosystem of freshwater communities (Loucks et al., 2001).
Over the last 200 years, approximately ninety-five percent of the Cumberland
Plateau has been disturbed at some point (Loucks et al., 2001). Its resources were
untapped until the early 1900s when the Industrial Revolution reached the southern
United States (Loucks et al., 2001). Logging, railroads, and mining were some of the
earliest land uses of the area, but were abandoned by the early 1950s at the close of
16
World War II (Loucks et al., 2001). Prior to that, the lands were converted for
agriculture, dam, and road building (Loucks et al., 2001). Currently, agriculture and
timber harvesting are the main land uses of the area. Eight percent of the area is used for
tobacco, hay, and corn and another eight percent is used as pasture primarily for beef
cattle. The remaining area, approximately eighty percent, is forested with portions being
used for timber harvesting and production. Urbanization in a minor concern in, though
there are some residential areas.
Conservation of Amphibians
Amphibian populations are declining and, in some cases, disappearing worldwide
(Beebee, 1996; Alford and Richards, 1999; Marks, 2006). Most documented declines of
populations have been attributed to habitat destruction, fragmentation, and alteration,
environmental pollution, competition with invasive and non-native species, climatic
changes, and disease (Beebee, 1996; Marks, 2006).
Habitat destruction, fragmentation, and alteration are among the major causes of
decline in amphibians populations. Encroachment upon vital habitats due to human
population growth and development pose serious issues for amphibians (Marks, 2006).
Habitat destruction is the complete elimination of an existing ecosystem which results in
the total loss of its preceding biological function (Alford and Richards, 1999). Examples
of this are the draining or filling of suitable amphibian habitats to build parking lots,
agricultural, residential, and other urban developments (Alford and Richards, 1999).
Agricultural fields and urban developments replace essential breeding habitats, create
17
impassible barriers between habitats, and alter once favorable environments. Forestry
operations, such as clearcutting, also destroy vital amphibian habitat. A study conducted
in the Appalachian Mountains estimated a loss of fourteen million salamanders annually
due to clearcutting operations in North Carolina (Petranka et al., 1993). This study
revealed a significant difference in the species richness and abundance of salamander
populations in clearcut areas and areas of untouched, mature forests (Petranka et al.,
1993). Captures were also five times higher in mature forest stands than in recently clear
cut areas (Petranka et al., 1993).
Habitat alteration is any change made to an ecosystem that may negatively affect
its function (Alford and Richards, 1999). In some agriculture systems, grazing livestock
create large problems for amphibians (Alford and Richards, 1999). Grazing animals
consume and trample aquatic vegetation which provides cover, food and breeding
habitats for some amphibians. In addition, this lack of vegetation ultimately leads to
stream bank erosion, which further reduces the suitability of a habitat (Alford and
Richards, 1999). Other habitat alterations which may adversely affect amphibians are fire
and flood management practices. In natural occurrences, fires and floods facilitate
vegetative succession which benefits and supports amphibian populations by providing
them with their complex habitat requirements (Marks, 2006). When suppressed and in
the absence of these disturbances, habitats become less desirable and less capable of
supporting amphibian populations (Marks, 2006).
Habitat fragmentation occurs as a result of habitat loss. When portions of a larger
ecosystem are developed by humans, smaller disjunctive habitats are formed. Most large
18
amphibian populations are, in actuality, metapopulations composed of several smaller,
interconnected populations (Marsh and Trenham, 2001). When separated by
development or roads, these small, interconnected populations are no longer connected
and this can result in the reduction of genetic diversity, the accumulation of hazardous
compounds, and introduced species (Alford and Richards, 1999). Lower numbers of
individuals reduce the gene pool at locations and also leave room for introduced species
to establish themselves (Alford and Richards, 1999). Isolation of breeding habitats can
also lead to reduced dispersal of individuals, which can lead to local extinction at once
thriving sites (Trenham et al., 2001). Roads are especially hazardous because not only do
they pose an obstacle for amphibians, but they also contribute directly to the mortality of
migrating individuals (Marks, 2006).
Environmental pollution is another major factor in the decline of amphibian
populations. Pollutants can be as extreme as radioactive waste or polychlorinated
biphenyls (PCBs) (Marks, 2006), but are more often one of the four main types of
chemical stressors: pesticides, heavy metals, acidification, or nitrate pollution (Beebee,
1996; Alford and Richards, 1999). Pesticides include insecticides, herbicides, and
fungicides, of which there are currently 19-20,000 available on the market (Beebee,
1996; Alford and Richards, 1999). These chemicals are tested via the Lethal Dose 50%
(LD50) test for their short term affects on various organisms. Though amphibians have a
range of tolerance levels to different chemicals, constant exposure to these chemicals
may result in larval death, high deformity rates, increased vulnerability to predation,
lowered feeding rates, and smaller size at metamorphosis (Alford and Richards, 1999).
19
Herbicides, specifically, reduce the food source of many larval species and have been
found to cause hermaphroditic individuals in the northern leopard frog (Alford and
Richards, 1999). The herbicide Atrazine, which is the most widely used herbicide in the
United States, has been recently scrutinized due to its effects on the endangered Barton
Springs salamander (Environmental News Service, 2005). Not only has it been found to
be toxic to the prey species of this and other amphibians, but it also acts as an endocrine
blocker, “chemically castrating and feminizing male amphibians” (Environmental News
Service, 2005).
Heavy metal and acid contamination often occur simultaneously because the
presence of heavy metals in water increases as pH decreases (Alford and Richards, 1999).
Metals that commonly accumulate in water sources are aluminum, lead, zinc, cadmium,
mercury, silver, copper, arsenic, manganese, molybdenum, and antimony (Alford and
Richards, 1999). Studies on various metal contaminants and their effects on salamanders
show reduced hatch success, lowered larval survival, and increased oral deformities and
metabolic rates as adverse affects (Alford and Richards, 1999). In one study, mercury
was found to reduce fitness in Northern Dusky salamanders which were chronically
exposed to the element via contaminated food sources (Bank et al., 2006). The same
study also found that constant exposure to aluminum can hinder larval respiration in
Northern Dusky salamanders via accumulation on the gills (Bank et al., 2006).
Acidification, which can also be facilitated by acid rain, has been shown to cause reduced
fertilization and developmental abnormalities in eggs (Marks, 2006). Acidification can
also inhibit enzymes which facilitate hatching, trapping a fully developed embryo inside
20
(Alford and Richards, 1999). Finally, nitrate pollution is the result of the excessive
accumulation of nitrogen in an ecosystem (Rouse et al., 1999). Nitrates occur in aquatic
environments naturally but can enter an ecosystem via agricultural runoff, livestock,
precipitation, high fertilizer use, and industrial waste (Rouse et al., 1999). Nitrate
pollution largely affects the eggs and larval forms of amphibians (Rouse et al., 1999).
Chronic effects of nitrate pollution include reduced feeding, swimming and hatching
success, and increased deformities and larval death (Alford and Richards, 1999).
Native amphibian populations can often be decimated by the introduction of
invasive and non-native species. Native species are rarely capable or adapted to deal
with new predators or competition (Marks, 2006). Invasive and non-native species can
be faunal or floral. Examples of faunal introductions which have adversely affected
amphibians are the introduction of the American Bull Frog (Rana catesbeiana)
throughout the west and mid-west for various reasons, the introduction of various species
of trout and other fish for sport fishing in Nevada and throughout the nation, and the
introduction of Mosquito fish to control mosquito populations throughout the world
(Alford and Richards, 1999). Each of these instances have resulted in the increased
predation of larvae, reduced metamorph size, and an overall reduction in amphibian
population size (Alford and Richards, 1999). The introductions of floral invasive and
non-native species alter vegetative aquatic and terrestrial habitats of amphibians, making
it more difficult for them to forage and breed (Maerz and Blossey, 2003). These
introductions can also lead to the displacement of native plants which serve as food to
their prey (Maerz and Blossey, 2003). Many invasive and non-native plants are not
21
edible to key invertebrates in amphibian diets and their introduction often leads to a
significant drop in the arthropod population (Maerz and Blossey, 2003). A study
conducted in New York in 2002 analyzed the impact of Japanese Knotweed on Green
frogs and revealed the invasion of this non-native plant degraded the foraging habitat of
these frogs and contributed to the limitation of prey availability (Maerz and Blossey).
Climatic change is a recent area of concern related to amphibian population
declines. Higher temperatures, lower soil moisture, shorter wet seasons, and more
variability in rainfall are all effects of global climate changes (Marks, 2006). These
changes can lead to amphibians breeding earlier, in many cases too early, which can
expose them to snowmelt-induced floods and early-season freezes (Carey and Alexander
2003). Climate changes can also result in reduced immune system function and an
increase in pathogen outbreaks (Lips et al 2006). Prolonged exposure to cold weather
can alter the immune systems of some amphibians which can lead to increased
vulnerability to pathogens (Carey et al., 1999). Finally, climate changes can lead to a
reduction in invertebrates available for consumption (Marks, 2006).
Disease is also an emerging problem plaguing amphibians. Recently declines in
amphibian populations worldwide have been attributed to a parasitic fungus (Marks,
2006). Two other diseases that have been a constant cause of amphibian mortality
worldwide are Chytridiomycosis and Ranaviral diseases (Daszak et al., 2000).
Chytridiomycosis is a disease produced by the chytrid fungus Batrachochytrium
dendrobatidis, which is the only parasitic chytrid which targets vertebrates (Daszak et al.,
2000). The fungi can be found in aquatic habitats and moist soil where it degrades
22
cellulose, chitin, and keratin (Daszak et al., 2000). In amphibians, it is hypothesized that
the parasite uses the keratin found in the skins of salamanders as a nutrient, causing skin
lesions which ultimately lead to death caused by a combination of the impairment of
cutaneous respiration and osmoregulation and the systematic absorption of the fungal
toxin (Daszak et al., 2000). Ranaviral diseases are a genus of diseases in the family of
Iridoviruses which plague fish, amphibians, and reptiles (Daszak et al., 2000). In frogs
and toads, these diseases cause systematic infections of the liver, kidneys, and digestive
tract, followed by death in the larval and metamorph stages of development of these
amphibians (Daszak et al., 2000). Salamanders exposed to these ranaviral diseases often
experience complications resulting from secondary bacterial infections which ultimately
lead to death from epidermal and visceral hemorrhaging (Daszak et al., 2000).
Each of these factors has its own individual and specific effects on amphibian
populations. But collectively, the decline of amphibian populations worldwide may have
a vast effect on the world’s ecosystems. Amphibians are of great ecological importance
and serve as a keystone and a bio-indicator organism (Marks, 2006). As a keystone
organism, they play an integral part in the food web of ecosystems by serving as prey and
predator. They consume insects and other primary consumers and are in turn consumed
by tertiary consumers, thereby, serving as a vital link in the food web. As a keystone
organism, they also serve as a regulatory predator. By consuming significant quantities
of prey organisms, they limit populations of many pest organisms. Amphibians are also
important energy links in terrestrial and aquatic habitats (Marks, 2006). Because they
consume and are consumed by organisms from both types of environments, they link
23
these environments. For these reasons alone, the mass loss of amphibians from any
ecosystem would have detrimental effects (Marks, 2006). As a bio-indicator species,
amphibians are often used as tool for the bio-assessment of an ecosystem (Marks, 2006).
Due to their vulnerability to environmental factors and changes, their presence, absence,
or abundance can often accurately gauge the health of an environment.
Alabama is the home of many species of amphibians and is ranked third in the
overall amphibian and reptile richness in the United States (Moriarty, 1997). In 2006,
there were seventy-four species of amphibians in Alabama, eight of which are protected
by the state of Alabama and one of which is also federally protected (Mirarchi, 2004). Of
these seventy-four amphibians, forty-four are salamanders (Mirarchi, 2004) and
currently, eight species are of moderate conservation concern and nine are of high
conservation concern (Mirarchi, 2004). Though the number of species of concern does
not seem high now, early prevention is the key to success in conservation. It is easier to
maintain high populations than to re-populate and bring species back from the brink of
extinction. In this regard, it is essential to take the necessary measures to prevent species
and population numbers from declining to unhealthy levels.
Description of Common Salamander Species in the Study Area
Spotted Salamander (Ambystoma maculatum)
Spotted salamanders can be found in most of the eastern region of the United
States (Petranka, 1998). As adults, they prefer mature deciduous forests but can be found
in mixed and/or coniferous forests if the environment is moist enough (Anderson, 1967;
24
Lang, 1972; Beane and Gaul, 1991). They are occasionally found in open habitats but
prefer habitats near forests edges. Spotted salamanders are subterraneous, often using the
burrows or tunnels of other animals, but can also be found beneath leaf litter and fallen
logs (Petranka, 1998). To breed, spotted salamanders require fishless, temporary pools.
They usually begin migrating to pools in late December and their breeding season
normally lasts into early Spring (Nyman, 1987). Females can lay several egg masses
which are attached to submerged vegetation. Egg gestation ranges from three to eight
weeks and after hatching their larval stage is usually two to three months (Nyman, 1987).
Larval Spotted salamanders conceal themselves underneath leaf litter and submerged
vegetation at the bottom of pools and feed on brachiopod crustaceans and other small
arthropods (Nyman, 1987). As they increase in size, they begin to take larger prey such
as larger insects, frog tadpoles, and even other salamander larvae (Petranka, 1998). Adult
salamanders will also feed upon earthworms, slugs, snails, and spiders (Petranka, 1998).
Marbled Salamander (Ambystoma opacum)
The Marbled salamander differs from other Ambystomid species in several ways.
They are fall breeders, they lay their eggs terrestrially, and they guard their eggs
(Nussbaum, 1985; Nussbaum, 1987; Noble and Brady, 1933). Adults begin to mate in
late Summer and the season can extend into early November in southern states (Petranka,
1998). After mating, a female will find a depression within or at the edge of a desiccated
temporary pool and lay her eggs in a clutch beneath vegetation, logs, and other debris
(Noble and Brady, 1933). The female will then tend to and defend her eggs until the pool
begins to fill and the eggs are submerged (Petranka, 1998). The larval period can be as
25
short as two months in southern climates but can be as long as eight to nine months in
northern areas (Doody, 1996). Once mature, adult Marbled salamanders spend the
majority of their life underground and under leaf litter. They also enlarge and use the
burrows of other animals and may even share burrows with others of their species
(Semlitsch, 1983). As young larvae, they consume small arthropods and zooplankton
(Petranka, 1998). As they grow, they become a major predator of other larval
salamanders but also prey up larger arthropods, worms, and even caterpillars that may
fall into pools (Petranka, 1998). Marbled salamanders prefer mature deciduous forests
but can also be found in mixed hardwood and pine stands, floodplains, and uplands
(Parmelee, 1993; Petranka, 1998)
Mole Salamander (Ambystoma talpoideum)
The range of Mole salamanders encompasses most of the Costal Plain of the
southeastern region of the United States with isolated populations in Alabama,
Tennessee, Illinois, and several other states (Garland and Lannoo, 2005). These animals
prefer cooler weather during breeding and migrations occur primarily between December
and March and are most intense during periods of heavy, sustained rain (Allen, 1932;
Carr, 1940; Gentry, 1955; Shoop, 1960; Mount, 1975; Hardy and Raymond, 1980; Walls
and Altig, 1986; Trauth et al., 1993; Trauth et al., 1995). Mole salamanders will breed in
a range of fishless wetlands but prefer shallow, heavily vegetated, temporary pools
(Garland, 2002). Females lay eggs in clusters on small twigs and other submerged
vegetation (Shoop, 1960). After hatching, the length of their larval stage varies but
generally ranges between three and four months (Dodd, 2004). But some populations of
26
Mole salamanders which breed in habitats which do not completely dry every year can be
paedomorphic and over winter in pools while retaining larval characteristics but still
becoming sexually mature (Scott, 1993). During their aquatic period, larvae seek refuge
under leaf litter, vegetation, and other submerged debris and primarily feed on
zooplankton (Anderson and Williamson, 1974). As they grow, they join adults in feeding
on larger aquatic invertebrates and may even cannibalize the eggs and larvae of other
Ambystomid species (Garland 2002; McAllister and Trauth, 1996). As terrestrial adults,
Mole salamanders are mainly subterraneous and usually only surface to forage for
invertebrates on moist, rainy nights.
Four-toed Salamander (Hemidactylium scutatum)
Four-toed salamanders can be found as far north as Maine, as far west as
Wisconsin, and as far south as Alabama, though populations seem to be more isolated in
the southern and western portions of its range (Behler, 1996). Four-toed salamanders
prefer undisturbed habitat in close proximity to suitable breeding habitat (Center for
Reptile and Amphibian Conservation and Management, 2008a). They can be found in
mature hardwood forests as well as coniferous forests and females will usually nest in
pools that are near and not necessarily directly adjacent to forest (Blanchard, 1923;
Wood, 1955). The actual mating in this species occurs in terrestrial habitats during the
Fall months and only the females actually migrate to pools in the Spring. Females will
nest along the banks of pools in sphagnum moss, sedges, grasses, and rotting logs (Wood,
1955; Harris and Gill, 1980). Four-toed salamanders nest solitarily or communally and
construct nests so that as larvae hatch, they can fall directly into the water. Females that
27
nest solitarily will lay and tend to only her eggs (Harris and Gill 1980). A communal nest
will usually consist of one female tending to the eggs of several other females who have
laid eggs and deserted them (Harris and Gill, 1980). Upon hatching, Four-toed
salamanders only have a larval period of three to six weeks (Blanchard, 1923). Adults
and larvae feed on mostly small arthropods and larvae will also prey on aquatic
crustaceans (Bishop, 1919).
Red-spotted Newt (Notophthalmus v. viridescens)
The range of the Red-spotted newt encompasses most of the eastern United
States. Adults inhabit both permanent and semi-permanent wetlands in upland and
bottomland areas (Bishop, 1943; Schwartz and Duellman, 1952; Bellis, 1968; Gates and
Thompson, 1982; Petranka, 1998). Red-spotted newts have a complex life cycle which
includes an aquatic egg and larval stage, a terrestrial juvenile stage (efts), and an aquatic
adult stage (Center for Reptile and Amphibian Conservation and Management, 2008b).
Migration periods vary depending on location for this species but usually occur during
rainy periods (Stein, 1938; Hurlbert, 1969) with efts breeding for the first time and
breeding adults entering the pools around the same time (Hurlbert, 1970). Females lay
eggs singly as opposed to in a clutch. The larval period also varies depending on
location. Larvae prefer shallower water than adults and will seek refuge at the bottom of
pools (Chadwick, 1950; Ashton, 1977). Both adult and larvae feed primarily on
arthropods and larvae will often cannibalize smaller individuals (Harris, 1987).
Terrestrial juveniles prefer moist wooded uplands and will sometime venture into open
areas (Center for Reptile and Amphibian Conservation and Managementb). Aquatic
28
adults prefer open, sunny areas with excessive emergent and submerged vegetation
(Schwartz and Duellman, 1952; Gates and Thompson, 1982) but will migrate onto land
when waters become too shallow.
29
METHODOLOGY
Study Site
I conducted the study at the James D. Martin Skyline Wildlife Management Area
(WMA) and the Walls of Jericho Forever Wild property on the southern extent of
Cumberland Plateau in Jackson County, Alabama. The Skyline WMA is 10,914 ha in
area (DCNR, 2006) and is currently used for recreation by the public and by researchers
from Alabama A&M University, the Tennessee Valley Authority and other government
organizations. The Walls of Jericho Forever Wild tract was formerly a property of the
Nature Conservancy and consists of 8,682 ha that are spread over northern Alabama and
southern Tennessee and was purchased by the Alabama State Lands Division in early
2004 (Nature Conservancy, 2006). Overall, the landscape is composed of primarily
deciduous forests with common species including: Sweetgum (Liqiudambar styraciflua),
Yellow Poplar (Liriodendron tulipifera), Hickory (Carya spp.), Maple (Acer spp.), and
Oak (Quercus spp.) species and a few Pine (Pinus spp.) species. The areas immediately
surrounding most of the artificial study pools are used for hunting, hiking, and horseback
riding. Most of the natural pools are located away from areas with hunting activities,
though some are located near gravel roads and trails used for recreation.
30
Figure 3.1. James D. Martin Skyline Wildlife Management Area and Forever Wild
Property located in the northern Jackson County, Alabama.
31
Study Pool Selection
To perform a baseline inventory of salamander usage of the pools in the study
area, I selected twenty vernal pools, ten natural and ten artificial, to monitor biophysical
parameters and salamander activity through monthly and bi-weekly surveys. The twenty
pools were selected from twenty-seven previously identified pools (Chan 2008) and
several other pools identified by the current land manager (Frank Allen, ALDCNR,
personal communication). These pools are representative of the vernal pools in the area
that could be accessed and monitored with the resources available for this study. The age
of most artificial pools in this study ranged from five to eight years, except Poplar Man 1
(11 years) and Poplar Spring 1 (12 years).
To assess the effectiveness of the artificial pools as amphibian breeding habitat, I
selected six pools, three artificial and three natural, for intensive monitoring based on two
criteria. The first was the surrounding environment. The artificial pools are all situated
with food plots parallel to one bank, a dam at one end, and bordered by forest on the two
remaining banks. The natural pools are all surrounded by forest and situated at least 100
m from any clear cuts, agricultural development, or paved roads. The second criterion
was the size of the pools, measured as the surface area (m2) and perimeter (m) at the
maximum fullness. Pools of similar size (See Table 4.3 and 4.4) were selected to reduce
possible confounding data due to variation in pool size.
32
Figure 3.2. Vernal pool locations in the Skyline WMA and Forever Wild Property in
Jackson County, Alabama.
33
Water Chemistry and Environmental Variables
I conducted bi-weekly surveys as long as pools retained water, which was
primarily between November and June. I measured water conditions (dissolved oxygen,
conductivity, pH, and salinity), air temperature and relative humidity, and soil
temperature at all twenty pools. I had no specific time of day in which I carried out
surveys though most were completed in the morning and early afternoon of survey days.
Dissolved Oxygen (mg/L) was measured using an EcoSense DO 200 Dissolved
Oxygen/Temperature meter (YSI Incorporated, Yellow Springs, OH). Salinity (ppm),
conductivity (µS), and water temperature (ºC) were measured using an ExStix II
pH/Conductivity meter (ExTech Instruments, Waltham, MO). pH was measured using a
pH10 pH & Temperature Pen (YSI Incorporated, Yellow Springs, OH). Each aquatic
measurement was taken at one point in the pool, chosen haphazardly, one time per survey
and there was no specific spot used at any pool for measurement taking. The cord and
probe used for dissolved oxygen (DO) allowed measurements to be taken approximately
four meters from shore so measurements were taken between the shore and that distance.
Salinity, conductivity, water temperature and pH were taken up to one meter from shore
depending on the depth of the pool at that time. Soil temperature (ºC) was measured at a
random point four to five inches below the surface during monthly surveys using a Taylor
Soil thermometer. Relative humidity (%) and air temperature was recorded using a
Digital Min/Max Thermohygrometer (Oakton Instruments, Vernon Hills, Illinois).
Other vernal pool features including pool characteristics (perimeter, area, depth,
and distance to forest edge) and microhabitat variables (percent coverage of canopy,
34
aquatic plants, floating leaves, submerged and emergent vegetation, leaf litter, downed
logs, and rocks) were measured on a monthly basis. These variables were selected based
on earlier studies of their importance to pool breeding amphibians (see literature review).
The perimeter and area of pools were measured via a walk of the outer edge of the pool
with a Garmin Etrex Legend C GPS unit (Garmin International Inc., Olathe, Kansas).
Elevation and the universal transverse mercator (UTM) coordinate of each pool location
was also taken using a Garmin GPS unit. Distance to forest edge was measured using a
one hundred meter measuring tape. A pool was classified as being within a forest if it
was within one meter of intact, mature forest on all sides. Depth, drying, and filling rates
were determined monthly by placing a metrically delineated PVC pipe in the deepest
accessible area of the pool and approximating the water level. Using ocular estimation,
the density (percent coverage) of vegetation in and around the pools was observed and a
class rating was recorded during the monthly visual survey of each pool via a walk of the
pool perimeter. Vegetation inside of pools was not identified, but instead, grouped into
several microhabitat categories. Based on their presence or absence, I rated canopy
cover, aquatic vegetation, floating leaves, submerged and emergent vegetation, leaf litter,
downed logs, and rocks on a scale of one to five with ratings increasing in increments of
20%. A score of one represented the lowest possible percentage of coverage and a score
of five represented the highest possible percentage. Aquatic vegetation was classified as
plants which require water to survive (i.e. algae) and would not be present or alive during
the dry seasons. Submerged and emergent vegetation were classified as land plants
35
which would be present and alive during the dry seasons and though they may have
remained during the wet season, were not necessarily alive.
Monitoring Salamanders
Drift Fences
Drift fences were erected at the six selected pools to monitor the traffic of
amphibians to and from these pools. At the artificial pools, one fence was placed parallel
to the forest, one parallel to the food plot, one parallel to the dammed shore, and one on
the remaining bank, which was also forested. At natural pools, using midpoint of the
pool as the origin, one fence was placed on the north, south, east and west face of the
pool. Each fence was installed approximately three meters from the high water mark at
each pool and provided 45- to 49% coverage; i.e. 45- to 49% of the pool was encircled by
drift fence. The drift fences I used were pre-assembled with wooden stakes in increments
of six meters apart. When pounded in to the ground, each fence was approximately one
meter in height. Nineteen-liter white plastic buckets were placed at both ends and on
either side of the drift fence as pitfall traps. With the exception of one smaller pool
(Albert Man 3) where each fence had three pitfall traps, there were four pitfall traps at
each fence. In traps located at the ends of the fence, Plexiglas was used to divide the
pitfall trap. This allowed me to determine the direction animals were traveling at the time
of capture.
36
Figure 3.3. Schematic for the set-up of drift fences at an artificial pool.
37
Figure 3.4. Schematic for the set-up of drift fences at natural pool.
38
Pitfall traps were placed by excavating a hole, positioning a bucket in that hole, filling in
any extra space with soil, and leveling the rim of the bucket flush with the ground
surface.
Drift fences were opened during breeding seasons from early-September to
December to sample fall and winter breeding species and from January until pools were
completely dry to sample spring breeding and emerging individuals. Drift fences were
also opened during the summer months during rain events to track the movement of
salamander metamorphs between breeding seasons.
Traps were opened one day prior to each forecasted rain event and checked daily
to sample peak salamander movements and avoid trapping when there was little to no
salamander movement. Traps were left open an additional day during wet conditions to
maximize captures. Because the study concentrated on semi-aquatic salamanders, the
capture of other amphibians was noted only. The direction of travel, species, sex (when
possible), body mass, snout-vent length (SVL), tail length and approximate
developmental stage (larvae, metamorph, emergent, or adult) of each captured
salamander was recorded. Direction of travel was determined based upon the side of the
fence the animal was captured. Animals were weighed to the nearest tenth of a gram
using a hand held scale (Ohaus Model HH 120D, Pine Brook, NJ) and length was
measured to the nearest tenth of a millimeter using a plastic dial caliper (Swiss Precision,
Switzerland). Approximate developmental stage was based upon an examination of the
animal or reference to a taxonomic key when needed. After measurement, animals were
released on the opposite side of the drift fence from their capture point.
39
Most semi-aquatic salamanders only use vernal pools for breeding and spend
most of their lives in the surrounding forests, making it difficult to determine which
species are present outside of the breeding season. Drift fences allowed me to catalog
species and quantify the individuals in a species using the pools for breeding and in turn
identify which species reside in that area year-round.
Minnow Traps
Minnow traps facilitated the monitoring of larval salamander presence and
development in the pools. Animals swam into the nets to seek refuge allowing me to
track the progress of developing salamanders. Weekly, four to eight minnow traps were
placed at random points throughout the pools with drift fence arrays. The number of
traps used in each pool was dependent on the area (m2) of the pool at that time. The
species, SVL, tail length, weight, and approximate stage of development of each animal
was recorded. The minnow trap data provided an estimation of the length of their larval
stage and their growth rates via their physical condition (length and weight) at the time of
capture. I attempted to determine if the development of larval salamanders was affected
by the pool’s status as artificial or natural and if water quality (e.g. pH and DO) had any
effects on salamander development and if the presence of aquatic vegetation played a role
in salamander development.
Visual Survey
Visual surveys were conducted at all twenty study pools. Biweekly visual
surveys of pools were used to count egg masses. Egg-laying is an important stage in a
salamander’s life cycle, and the number of masses in a pool can be an important indicator
40
of a population’s breeding success. The absence of egg masses or large numbers of
unsuccessful egg masses or high levels of larval mortality not directly related to pool
drying could indicate that an environment is conducive to egg-laying but not to the
healthy development of salamanders and such habitat may be ‘sink’ or a trap in which the
reproductive effort of individuals is wasted. Again by comparing the survey results at
artificial and natural pools, I attempted to determine the effectiveness of artificial pools as
breeding habitat for various salamander species.
Data Analysis
Species diversity between artificial and natural pools was calculated using the
Shannon-Wiener diversity index. Species diversity within pools was calculated using
Simpson’s Index. Morisita’s Index of Similarity (Programs for Ecological Methodology,
2nd Ed. © 2003) was used to evaluate the similarities of salamander communities among
vernal pools. Species richness and relative abundance were calculated using individual
capture numbers. I used multivariate analysis of variance (MANOVA) (SPSS 10.0 for
Windows © 1989-1999) to test the differences in salamander community variables and
habitat features between natural and artificial pools. When the MANOVA was
significant, the analysis of variance (ANOVA) (SPSS 10.0 for Windows © 1989-1999)
was used to determine which variable was the source of significance. Using MANOVA
allowed me to control potential inflation of the Type I error rate caused by the use of
many variables. I visually examined the univariate normality and equal variance between
the two types of pools, and found most variables tended to be normally distributed and
41
their variances were similar. Relationships between richness and abundance of breeding
salamanders and habitat and water quality variables were examined with correlation
analysis. Canonical Correspondence Analysis (CCA) (PCORD 5.0 © 1995-2005) was
used to evaluate the relationship between species and various environmental parameters
and habitat variables. CCA is a reciprocal averaging eigenanalysis method that uses
multiple regression on the environmental matrix to constrain the ordination. The
objective is to find ordination axes that maximally reveal the joint structure of the two
matrices (Jongman et al., 1987). CCA assumes unimodality of species responses,
linearity of environmental effects, and the orthogonality (lack of correlation) of the
underlying gradients. CCA in PCORD is most efficient for testing the hypothesis of no
linear relationship between species and environmental variables and the relationship
among sites or species (Jeri Peck, Penn State University, personal communication). All
tests for significant differences were performed at α = 0.05 level.
42
RESULTS
Characteristics of Natural and Artificial Pools
Overall, biophysical features of natural pools differed from that of artificial pools
(MANOVA Pillai’s Trace= 0.820, F= 6.28, p= 0.003) based on the 20 pools sampled
(Table 4.1). Distance to the edge of forest (p= 0.01), elevation (p = 0.001), pool depth
(p= 0.002), and pH (p< 0.001) were significantly different between natural and artificial
pools. Artificial pools tended to be located at a lower elevation, were deeper, and had a
higher pH than natural pools. Although the artificial pools, on average, tended to be
larger (1,450 m2 and 216 m) than natural pools (1,094 m2 and 204 m) measured by
maximum pool area and maximum perimeter, respectively, the difference was not
significant because of large variations within each category (Table 4.1). The conductivity
(p= 0.58) and mean water temperature (p= 0.88) were also not different between the two
pool types. Dissolved oxygen and salinity were measured intermittently throughout the
study, but due to faulty equipment, measurements were not used in the final analysis.
I began surveying pools in early January 2007. Several pools, three artificial and
two natural were already retaining water. The remaining natural and artificial pools
inundated around the same period of time. Overall, most pools began retaining water in
February. There were two natural pools, Letson Point 3 and Tate Cove, which did not
43
Table 4.1. Comparisons of biophysical features (mean ± SD) of artificial and natural
vernal pools at the James D. Martin Skyline Wildlife Management Area and the Walls of
Jericho Forever Wild property on the southern extent of Cumberland Plateau in Jackson
County, Alabama. MANOVA Pillai’s Trace= 0.82, F= 6.28, Hypothesis df= 8, Error df=
11, p= 0.003.
Artificial
Natural
Variable
(n=10)
(n=10)
F
P
Distance to
forest (m)
0 ± 0.0
7.86
0.012*
6.6± 7.4
Maximum
perimeter(m)
215.7 ± 203.4
204.0 ± 130.3
0.02
0.880
2
Area (m )
1450.5 ± 1015.5
1093.9 ± 715.4
0.82
0.376
Maximum
depth (m)
1.3 ± 0.4
13.54 0.002*
2.3 ± 0.8
pH
4.9 ± 0.3
19.54 0.000*
5.8 ± 0.6
Conductivity (µS)
21.7 ± 19.3
25.4 ± 7.2
0.31
0.584
Mean water
temperature (ºC)
14.9± 1.9
14.8 ± 1.0
0.02
0.883
Elevation (m)
1696.9 ± 44.9
14.98 0.001*
1766.8 ± 35.3
44
Table 4.2. Comparisons of biophysical features (mean ± SD) of artificial and natural
vernal pools selected for intensive drift fence trapping at the James D. Martin Skyline
Wildlife Management Area and the Walls of Jericho Forever Wild property on the
southern extent of Cumberland Plateau in Jackson County, Alabama. MANOVA Pillai's
Trace= 0.97, F= 8.82, Hypothesis df= 4, Error df= 1 , p= 0.25.
Artificial
Natural
Variable
(n=3)
(n=3)
F
P
Distance to
forest (m)
6.3 ± 6.0
0 ± 0.0
3.31
0.143
Maximum
perimeter (m)
183.7 ± 123.0
156.7 ± 78.0
0.10
0.764
2
Area (m )
1748 ± 1427.9
1035.7 ± 897.5
0.54
0.505
Maximum
depth (m)
1.1 ± 0.2
13.64
0.021*
2.7 ± 0.7
pH
4.9 ± 0.4
12.07
0.026*
5.7 ± 0.2
Conductivity (µS)
25.8 ± 2.3
19.5 ± 5.0
3.93
0.118
Mean water
temperature (ºC)
15.3 ± 2.3
14.6 ± 0.5
0.24
0.647
Elevation (m)
1723 ± 20.4
27.66
0.006*
1796.3 ± 12.9
45
become inundated until March. Water levels varied throughout the first season but I did
not observe any pools completely dried and refilled. Some pools receded to the point
where depth markers were no longer submerged and depth had to be determined via
ocular estimation. Pools began to lose water in May and most natural pools were dry by
June. Hiking Trail was the only natural pool to retain water past June and fully dried in
August. Artificial pools, however, retained water further into the summer months. Only
Albert Man 2 and Albert Man 3 were fully dry by June, followed by Horse Trail 1, which
dried in July. The remaining artificial pools, with the exception of Albert Man and
Letson Point 2, became desiccated in August. Albert Man and Letson Point 2 retained
water until the second season of trapping and while levels receded, they never completely
dried.
Pools began to fill again as early as November 2007. The only natural pool to
begin filling in 2007 was Albert Parker 1. Artificial pools Albert Man 2, Albert Man 3,
Poplar Man 3 and Poplar Spring 1 also began filling in November. All remaining pools,
natural and artificial began filling in January and February. Pools dried earlier during the
second season than the first season. Most natural pools and three artificial pools were dry
by May 2008. Letson Point 3 retained water until June and Tate Cove and Hiking Trail
held water until July. With the exception of Albert Man 2, Albert Man 3, and Ollie,
artificial pools also held water until July. At the close of my second survey season,
Letson Point 2 and Albert Man were still inundated.
46
5/8/08
3/8/08
1/8/08
11/8/07
9/8/07
7/8/07
5/8/07
3/8/07
Hydroperiods of Natural Pools
1/8/07
Depth (m)
4
3.5
3
2.5
2
1.5
1
0.5
0
Time (Months)
Albert Parker 1
Letson Point 1
Albert Parker 2
Letson Point 3
Hiking Trail
Poplar Spring 2
Horse Trail 2
Sign
Horse Trail 3
Tate Cove
Figure 4.1. Hydroperiod of natural vernal pools in Jackson County, Alabama between
January 2007 and July 2008.
Hydroperiods of Artificial Pools
5/8/08
3/8/08
1/8/08
11/8/07
9/8/07
7/8/07
5/8/07
1
0.5
0
3/8/07
3
2.5
2
1.5
1/8/07
Depth (m)
4
3.5
Time (Months)
Albert Man
Albert Man 2
Albert Man 3
Albert Man 4
Horse Trail 1
Letson Point 2
Ollie
Poplar Man 1
Poplar Man 3
Poplar Spring 1
Figure 4.2. Hydroperiod of artificial vernal pools in Jackson County, Alabama between
January 2007 and July 2008.
47
Natural and artificial pools were similar in their tree species composition.
Species commonly observed within the immediate area surrounding both types of pools
include: Red Maple (Acer rubrum), Sweet Gum (Liquidambar styraciflua), Black Gum
(Nyssa sylvatica), Yellow Poplar (Liriodendron tulipifera), Loblolly Pine (Pinus taeda),
and several Hickory (Carya) and Oak (Quercus) species. There was a significant
difference in overall vegetative cover between natural and artificial pools (Pillai’s Trace=
0.83, F= 6.64, p= 0.003). When an ANOVA was conducted to examine the significance
of each category, submerged vegetation, canopy cover, floating leaves, leaf litter, and the
amount of rocks were all significantly different between natural and artificial pools.
Artificial pools had significantly more submerged vegetation (p= 0.015) and rocks (p=
0.025), while natural pools had significantly more tree canopy cover (p= 0.004) over and
leaf litter (p< 0.001) within them. But when the categories of vegetation were compared
at the six fenced pools, as with the environmental conditions, there was no significant
difference between natural and artificial pools (Pillai’s Trace= 0.67, F= 0.50, p= 0.77).
48
Table 4.3. Comparison of microhabitat variables (percent coverage) (mean ± SD)
between natural and artificial vernal pools in Jackson County, Alabama. MANOVA
Pillai’s Trace= 0.83, F= 6.64, Hypothesis df= 8, Error df= 11, p= 0.003.
Artificial
Natural
Mean ± SD
Mean ± SD
Variable
(n=10)
(n=10)
F
p
Aquatic
vegetation
1.6 ± 0.7
1.6 ± 1.0
0.00
1.000
Submerged
vegetation
1.4 ± 0.7
7.31
0.015*
2.5 ± 1.1
Emergent
vegetation
2.0 ± 0.7
2.5 ± 1.1
1.55
0.229
Downed trees
and logs
1.6 ± 0.7
1.3 ± 0.5
1.25
0.279
Rocks
1.0 ± 0.0
6.00
0.025*
1.4 ± 0.5
Canopy cover
1.0 ± 0.0
11.25
0.004*
2.0 ± 0.9
Floating
leaves
1.0 ± 0.0
3.86
0.065
1.3 ± 0.5
Leaf litter on
pool floor
2.2 ± 1.1
60.83
0.000*
5.0 ± 0.0
49
Table 4.4. Comparison of microhabitat variables (percent coverage) (mean ± 1 SD)
between natural and artificial vernal pools selected for intensive drift fence trapping in
Jackson County, Alabama. MANOVA Pillai’s Trace= 0.667, F = 0.500, Hypothesis df
=4, Error df=1, p=0.770.
Artificial
Natural
Variable
(n=3)
(n=3)
F
p
Aquatic
vegetation
1.3 ± 0.6
1.7 ± 1.2
0.20
0.678
Submerged
vegetation
2.3 ± 1.5
2.0 ± 1.0
0.10
0.768
Emergent
vegetation
2.0 ± 1.0
2.0 ± 0.0
0.00
1.000
Downed trees
and logs
1.3 ± 0.6
1.0 ± 0.0
1.00
0.374
Rocks
1.3 ± 0.6
1.3 ± 0.6
0.00
1.000
Canopy cover
1.3 ± 0.6
1.3 ± 0.6
0.00
1.000
Floating
leaves
1.0 ± 0.0
1.3 ± 0.5
1.00
0.374
Leaf litter on
pool floor
3.0 ± 2.0
4.0 ± 1.7
0.43
0.548
50
Table 4.5. Description of twenty vernal pools at the James D. Martin Skyline Wildlife Management Area and the Walls of
Jericho Forever Wild property on the southern extent of Cumberland Plateau in Jackson County, Alabama.
51
Pool
Albert Man
Albert Man 2
Albert Man 3*
Albert Man 4
Horse Trail 1*
Letson Point 2*
Ollie
Poplar Man 1
Poplar Man 3
Poplar Spring 1*
Albert Parker 1
Albert Parker 2*
Hiking Trail*
Horse Trail 2
Horse Trail 3
Letson Point 1
Letson Point 3*
Poplar Spring 2
Sign
Tate Cove
* Fenced Pools
Age of
Pool
(Years)
7.5
6
7.5
7.5
Unknown
Unknown
5
11
7
12
Unknown
Unknown
Unknown
Unknown
Unknown
Unknown
Unknown
Unknown
Unknown
Unknown
Origin
Artificial
Artificial
Artificial
Artificial
Artificial
Artificial
Artificial
Artificial
Artificial
Artificial
Natural
Natural
Natural
Natural
Natural
Natural
Natural
Natural
Natural
Natural
Latitude
Longitude
34.837994
34.845505
34.845204
34.848137
34.962752
34.92529
34.86394
34.888293
34.880351
34.863968
34.849233
34.849817
34.85349
34.964183
34.962968
34.930936
34.925957
34.897475
34.98405
34.940067
-86.144851
-86.136498
-86.144674
-86.14156
-86.089296
-86.055383
-86.102954
-86.140755
-86.133015
-86.130812
-86.144333
-86.145767
-86.13073
-86.088486
-86.087404
-86.056741
-86.05425
-86.13894
-86.069533
-86.083417
51
Elevation
(m)
494
494
518
515
527
533
516
524
525
527
522
549
551
530
542
540
543
542
547
521
Distance Maximum
to forest Perimeter Maximum Maximum
Area (m2) Depth (m)
(m)
(m)
5
739
1552
1.2
4
46
158
0.9
7
60
257
2.1
5
45
170
2.4
0
209
2112
2.3
24
161
1656
2.6
15
244
2531
2.8
3
193
1763
2.4
3
154
1203
2.5
0
306
3103
3.5
0
124
617
2.0
0
87
432
0.9
0
241
2067
1.0
0
193
1206
1.4
0
255
1546
0.6
0
241
890
0.9
0
142
608
1.3
0
134
521
1.8
0
93
578
1.4
0
530
2474
1.3
Table 4.6. Average (Mean ± SD) water conditions at twenty vernal pools at the James D. Martin Skyline Wildlife Management
Area and the Walls of Jericho Forever Wild property on the southern extent of Cumberland Plateau in Jackson County,
Alabama.
52
Pool
Albert Man
Albert Man 2
Albert Man 3*
Albert Man 4
Horse Trail 1*
Letson Point 2*
Ollie
Poplar Man 1
Poplar Man 3
Poplar Spring 1*
Albert Parker 1
Albert Parker 2*
Hiking Trail*
Horse Trail 2
Horse Trail 3
Letson Point 1
Letson Point 3*
Poplar Spring 2
Sign
Tate Cove
*Fenced Pool
Origin
Artificial
Artificial
Artificial
Artificial
Artificial
Artificial
Artificial
Artificial
Artificial
Artificial
Natural
Natural
Natural
Natural
Natural
Natural
Natural
Natural
Natural
Natural
Mean pH
5.8 ± .35
5.3 ± .43
5.5 ± .30
5.6 ± .35
5.5 ± .42
6.2 ± .53
7.3 ± .66
5.2 ± .39
6.0 ± .47
5.8 ± .41
5.1 ± .32
4.5 ± .27
5.2 ± .41
4.8 ± .34
5.1 ± .37
4.7 ± .35
5.0 ± .45
4.6 ± .25
4.4 ± .22
5.3 ± .38
Mean Conductivity (µS)
13.6 ± 5.02
11.7 ± 4.37
18.2 ± 14.03
11.7 ± 5.53
17.7 ± 4.03
12.7 ± 3.15
75.5 ± 24.91
13.2 ± 3.09
17.9 ± 9.25
25.2 ± 13.22
15.3 ± 4.96
25.8 ± 17.58
28.1 ± 9.71
22.7 ± 3.52
19.0 ± 5.70
23.6 ± 7.90
23.5 ± 9.87
38.7 ± 29.38
35.8 ± 17.44
21.2 ± 5.03
52
Mean H20 Temp (ºC)
15.0 ± 6.49
13.1 ± 3.35
12.7 ± 5.16
15.8 ± 7.36
14.3 ± 5.99
18.1 ± 7.40
15.2 ± 6.79
15.3 ± 5.99
12.2 ± 5.49
17.0 ± 7.90
13.1 ± 5.46
14.4 ± 5.62
14.3 ± 5.42
14.7 ± 3.71
16.5 ± 5.41
16.6 ± 5.11
15.2 ± 6.03
14.7 ± 3.63
13.9 ± 5.17
14.8 ± 6.77
Species Richness and Abundance
There were fifty-eight successful trap nights where individuals were captured.
Over this course of time, a total of 8850 captures from nine species were encountered in
either pitfall or minnow traps. Of those captures, 2627 individuals were adults captured
traveling into pools and 2854 individuals were adults captured exiting pools. Of the
remaining 1085 adult individuals, 836 were captured in minnow traps and there were 249
whose direction of travel was not clear. Emergents were either captured leaving the
pools or their direction of travel was unclear but it is assumed that they were also leaving
the pools. Of the 1459 captured, 656 were clearly exiting the pool. Metamorphs
numbered 825 and were only captured in minnow traps. Ninety-seven percent of the
individuals I captured in traps were alive. Three percent of individuals were lost to
predation and desiccation.
The most abundant and commonly encountered species were the spotted, mole,
and marbled salamanders (42.7%, 23.0%, and 22.7% of total captures respectively)
(Table 4.7). Red-spotted newts and Four-toed salamanders were a common occurrence at
Poplar Spring 1 pools but were not very abundant across the entire study area (9.1% and
2.0%, respectively). Several terrestrial species were also observed (Zig-zag, Green, Red,
and Slimy salamanders) but were not frequently encountered. Overall, species were most
abundant between February and May in both 2007 and 2008 at both natural and artificial
pools (Figures 4.3 and 4.4). Hiking Trail consistently had the most captures in 2007 and
2008 for natural pools. Horse/Letson had the highest abundance of salamanders in 2007
but Poplar Spring1 had the highest abundance in 2008 among artificial pools. The total
53
Table 4.7. Species richness and relative abundance of drift fence and minnow trap
captures between February 2007 and July 2008 (8,850 total captures).
Species
Scientific Name
Common Name
Total Proportion
Code
AMMA Ambystoma maculatum
Spotted salamander
3776
42.0
AMOP Ambystoma opacum
Marbled salamander
2040
23.0
AMTA Ambystoma talpoideum
Mole salamander
2006
22.0
NOVI
Red-spotted newt
806
9.0
Notophthalmus v.
viridescens
HESC Hemidactylium scutatum
Four-toed salamander
180
2.0
PLDO Plethodon d. dorsalis
Zig-zag salamander
34
<1
ANAE Aneides aeneus
Green salamander
5
<1
PSRU
Red salamander
2
Pseudotriton ruber
<1
PLGL
Slimy salamander
1
Plethodon glutinosis
<1
54
Captures Per Month at Natural Pools
1500
1000
Jun-08
Apr-08
Feb-08
Dec-07
Oct-07
Apr-07
Feb-07
0
Aug-07
500
Jun-07
Total Captured
2000
Time (Months)
Albert Parker 2
Hiking Trail
Letson Point 3
Figure 4.3. Total salamander captures per month between February 2007 and July 2008 at
fenced natural pools in Jackson County, Alabama.
.
Captures Per Month at Artificial Pools
1500
1000
Jun-08
Apr-08
Feb-08
Dec-07
Oct-07
Apr-07
Feb-07
0
Aug-07
500
Jun-07
Total Captured
2000
Time (Months)
Albert Man 3
Horse/Letson
Poplar Spring 1
Figure 4.4. Total salamander captures per month between February 2007 and July 2008 at
fenced artificial pools in Jackson County, Alabama.
55
number of captures of encountered species, excluding Green, Red, Zig-zag, and Slimy
salamanders because of their extremely low presence, were compared using a MANOVA
and based on the total abundance of commonly encountered semi-aquatic species (Redspotted newts, Spotted, Mole, Marbled, and Four-toed salamanders), there was no
significant difference between natural and artificial pools (Pillai's Trace= 1.00, F= 48.11,
p= 0.11) (Table 4.8). To account for the possibility of individuals being counted twice
when captured in drift fences, analyses were performed on totals excluding the captures
of adult leaving pools. When these totals were compared in a MANOVA there was still
no significant difference between natural and artificial pools (Pillai's Trace= 0.58, F=
0.35, p= 0.83) (Table 4.9).
Adults were the most commonly captured life stage, accounting for 74.2% of the
total captures. Emergents accounted for 16.5% of captures and metamorphs accounted
for 9.3% of captures. With the exception of one, most species demonstrated the pattern
of adults representing the largest proportion of individuals captured. In the Marbled
salamander, the emergent life stage was the most commonly encountered, accounting for
1335 of the species’ 2040 captures. Metamorph captures also accounted for more
captures than adults in this species with 542 of the total captures. Adults only
represented 6.9% of captures, with 140 individuals in this species.
56
Table 4.8. Comparisons of total captures (mean ± SD) at artificial and natural vernal
pools at the James D. Martin Skyline Wildlife Management Area and the Walls of
Jericho Forever Wild property on the southern extent of Cumberland Plateau in Jackson
County, Alabama. MANOVA Pillai’s Trace= 1.00, F= 48.11, Hypothesis df= 4, Error df
=1, p=0.11.
Artificial
Natural
Species
(n=3)
(n=3)
F
P
Total Captures
(All Species)
1024.0 ± 943.0
1927.0 ± 1605.0
0.70
0.448
Spotted salamander
160.0 ± 142.0
1100.0 ± 1215.0
1.77
0.254
Mole salamander
273.7 ± 233.0
395.0 ± 283.0
0.33
0.597
Red-spotted newt
210.0 ± 336.0
58.0 ± 52.0
0.60
0.482
Four-toed
salamander
44.0 ± 38.0
17.0 ± 14.0
1.40
0.303
Marbled
salamander
335.0 ± 479.0
345.0 ± 98.0
0.00
0.972
Table 4.9. Comparisons of individual captures (total captures excluding adults traveling
out) (mean ± SD) at artificial and natural vernal pools at the James D. Martin Skyline
Wildlife Management Area and the Walls of Jericho Forever Wild property on the
southern extent of Cumberland Plateau in Jackson County, Alabama. MANOVA Pillai's
Trace= 0.58, F= 0.35, Hypothesis df= 4, Error df= 1, p=0.83.
Artificial
Natural
Species
(n=3)
(n=3)
F
P
Total Captures
(All Species)
697.0 ± 847.0
1184.0 ± 834.0
0.50
0.112
Spotted salamander
47.0 ± 37.0
614.0 ± 674.0
2.12
0.346
Mole salamander
90.0 ± 92.0
206.0 ± 56.0
3.48
0.465
Red-spotted newt
205.0 ± 330.0
33.0 ± 53.0
0.79
0.164
Four-toed
salamander
26.0 ± 27.0
9.0 ± 7.0
1.14
0.221
Marbled
salamander
329.0 ± 472.0
322.0 ± 97.0
0.00
0.981
57
58
Table 4.10. Adults (traveling in and out) captured by drift fences and minnow traps at intensively studied vernal pools in
Jackson County, Alabama between February 2007 and July 2008.
ADULTS (IN)
Origin
AMMA AMTA PLDO ANAE NOVI HESC PSRU PLGL AMOP TOTAL
Albert Man 3
Artificial
4
5
0
0
0
2
0
0
1
12
Horse/ Letson
Artificial
65
81
0
0
0
21
0
1
2
170
Poplar Spring 1
Artificial
72
70
0
0
5
53
0
0
11
211
Albert Parker 2
Natural
30
19
0
2
0
15
0
0
12
78
Hiking Trail
Natural
1345
224
5
0
0
2
0
0
6
1582
Letson Point 3
Natural
451
88
0
0
1
10
0
0
24
574
Total
1967
487
5
2
6
103
0
1
56
2627
ADULTS (OUT) Origin
AMMA AMTA PLDO ANAE NOVI HESC PSRU PLGL AMOP TOTAL
Albert Man 3
Artificial
5
39
0
0
0
6
0
0
0
50
Horse/ Letson
Artificial
143
312
2
0
1
20
2
0
2
482
Poplar Spring 1
Artificial
102
186
0
0
5
28
0
0
14
335
Albert Parker 2
Natural
35
39
0
3
0
16
0
0
17
110
Hiking Trail
Natural
966
443
25
0
5
1
0
0
15
1455
Letson Point 3
Natural
332
47
1
0
3
6
0
0
33
422
Total
1583
1066
28
3
14
77
2
0
81
2854
ADULT
(MINNOW)
Origin
AMMA AMTA PLDO ANAE NOVI HESC PSRU PLGL AMOP TOTAL
Albert Man 3
Artificial
0
1
0
0
0
0
0
0
0
1
Horse/Letson
Artificial
0
8
0
0
21
0
0
0
0
29
Poplar Spring 1
Artificial
0
5
0
0
562
0
0
0
0
567
Albert Parker 2
Natural
0
16
0
0
0
0
0
0
0
16
Hiking Trail
Natural
6
29
0
0
93
0
0
0
0
128
Letson Point 3
Natural
6
29
0
0
60
0
0
0
0
95
Total
12
88
0
0
736
0
0
0
0
836
58
59
Table 4.11. Emergent and metamorph drift fence and minnow trap captures at intensively studied vernal pools in Jackson
County, Alabama between February 2007 and July 2008.
EMERGENTS
AMMA AMTA PLDO ANAE NOVI HESC PSRU PLGL AMOP TOTAL
Albert Man 3
Artificial
0
0
0
0
1
0
0
0
47
48
Horse/Letson
Artificial
0
64
0
0
2
0
0
0
44
39
Poplar Spring 1
Artificial
0
0
0
0
3
2
0
0
741
746
Albert Parker 2
Natural
0
0
0
0
1
0
0
0
111
112
Letson Point 3
Natural
0
26
0
0
0
0
0
0
130
156
Hiking Trail
Natural
0
5
0
0
0
0
0
0
282
287
Total
0
95
0
0
7
2
0
0
1355
1459
METAMORPHS
AMMA AMTA PLDO ANAE NOVI HESC PSRU PLGL AMOP TOTAL
Albert Man 3
Artificial
0
0
0
0
2
0
0
0
20
22
Horse/Letson
Artificial
2
44
0
0
2
0
0
0
0
48
Poplar Spring 1
Artificial
1
2
0
0
15
0
0
0
122
140
Albert Parker 2
Natural
2
179
0
0
1
0
0
0
88
270
Letson Point 3
Natural
0
19
0
0
6
0
0
0
203
228
Hiking Trail
Natural
1
5
0
0
2
0
0
0
109
117
Total
6
249
0
0
28
0
0
0
542
825
59
Species Diversity
Species richness and relative abundance calculations were used to examine
species diversity within and between natural and artificial pools. I used both the
Shannon-Wiener Index and the Simpson’s Diversity Index to examine the species
compositions at fenced pools. The Shannon-Wiener Index takes into account the number
of species and the evenness of their abundances (Krebs, 1989). Higher numbers signify a
more diverse group, where as, lower numbers indicate fewer species or an uneven
distributions of species caused by large gaps in species numbers or rare species (Krebs,
1999). Simpson’s Index (1-D) characterizes species diversity as the probability that two
randomly selected individuals will be of the same species (Simpson, 1949). In this index,
a value of one represents infinite diversity and a value closer to zero represents low
species diversity (Krebs, 1999).
A MANOVA was conducted on pool diversity index scores to determine if there
was a significant difference in the species diversity at pools. The species diversity was
not different between in natural and artificial pools (Pillai's Trace= 0.82, F= 1.14, p=
0.60) (Table 4.12 and 4.13). When each index was compared in a separate ANOVA
there was still no significant difference. This was also the case when only adults
traveling out of pools were excluded (Pillai's Trace= 0.56, F= 0.32, p= 0.85) (Table 4.13).
60
Table 4.12. Diversity indices of the fenced natural and artificial pools using total
captures. MANOVA Pillai's Trace= 0.82, F= 1.14, Hypothesis df= 4 Error df= 1, p=
0.60.
Shannon-Wiener
Pool
Origin
Index
Simpson's Index
Albert Man 3
Artificial
1.146
0.615
Horse/Letson
Artificial
1.049
0.586
Poplar Spring 1
Artificial
1.335
0.690
Mean ± SD
1.2 ± 0.15
0.6 ± 0.05
Albert Parker 2
Natural
1.192
0.646
Hiking Trail
Natural
0.983
0.517
Letson Point 3
Natural
1.161
0.621
Mean ± SD
1.1 ± 0.1
0.6 ± 0.07
F
0.37
0.51
P
0.576
0.517
Table 4.13. Diversity indices of the fenced natural and artificial pools using only adults
traveling into pools, emergent, and metamorph captures. MANOVA Pillai's Trace= 0.56,
F= 0.32, Hypothesis df= 4, Error df= 1, p= 0.85.
Shannon-Wiener
Pool
Origin
Index
Simpson's Index
Albert Man 3
Artificial
0.709
0.319
Horse/Letson
Artificial
1.130
0.586
Poplar Spring 1
Artificial
1.095
0.595
Mean ± SD
1.0 ± 0.23
0.5 ± 0.16
Albert Parker 2
Natural
1.055
0.595
Hiking Trail
Natural
1.028
0.539
Letson Point 3
Natural
1.226
0.663
Mean ± SD
1.1 ± .11
0.6 ± 0.06
F
0.71
1.04
P
0.447
0.366
61
Spatial Distribution and Temporal Patterns
Red-spotted newts, Spotted, Mole, Marbled and Four-toed salamanders were
present at all six of the fenced pools (Figure 4.10). Zig-zag salamanders were only
present in one artificial (Horse/Letson) pool and in two natural (Hiking Trail and Letson
Point 3) pools. Red, Green, and Slimy salamanders were present at only one of the
fenced pools. Red and Slimy salamanders were captured only at Horse/Letson and Green
salamanders were captured only at the natural pool Albert Parker 2. Hiking Trail had the
most captures at a natural pool, as well as among all the pools, with 3709 total. Poplar
Spring 1 had the most captures of the artificial pools with 2012 total and the least amount
of captures occurred at the artificial pool Albert Man 3.
During the first field season, which began on February 2007, most pools had a
minimum of one species observed after the first trap night. Red-spotted Newt were only
captured on one occasion and that was after the first trap night and Red Salamanders
were also only captured on one occasion. Zig-zag Salamanders were not captured until
early March 2007. Additionally, Mole Salamanders were not seen until March at Albert
Man 3 and Four-toed Salamanders were not seen until March at Albert Man 3 or Hiking
Trail. Marbled Salamanders were only observed in May at three (Albert Man 3, Poplar
Springs 1, and Letson Point 3) of the five pools at which they were present. All species,
with the exception of those seen on only one date, were observed in at least one pool until
early to mid April. Spotted, Zig-zag, Green, and Four-toed Salamanders were the first
species to stop coming into the pools. Marbled and Mole salamanders were the only
62
species to persist into May in several pools (Horse Trail 1, Hiking Trail, and Albert
Parker 2).
63
Captures by Pool
2500
2000
AMMA
64
Total Captured
AMTA
PLDO
1500
ANAE
NOVI
HESC
1000
PSRU
PLGL
AMOP
500
0
Artificial
Artificial
Artificial
Natural
Natural
Natural
Albert Man 3
Horse/Letson
Poplar Spring 1
Albert Parker 2
Hiking Trail
Letson Point 3
Fenced Pools
Figure 4.5. Drift fence and minnow trap captures by pool in Jackson County, Alabama. Includes total adult,
emergent, and metamorph captures.
64
The second trap season began in October of 2007. Red-spotted Newts and
Marbled Salamanders were the only species seen at all but one pool in the month of
October (Letson Point 2 and Letson Point 3, respectively). Mole Salamanders occurred
at Poplar Spring 1 during October and proceeded to appear in one pool at a time through
the month of March as opposed to simultaneously at several pools in a short period of
time. Spotted Salamanders appeared in Letson Point 3 in November but did not start
moving into any other pools until January and were not present at Albert Man 3 at all
during the second season. Zig-zag salamanders were observed in two different pools
during two different months, November in Hiking Trail and April in Letson Point 3.
Four-toed salamanders did not move into pools until January and February and were
completely absent from Albert Man 3 and Letson Point 2 during the second season. With
the exception of Spotted Salamanders, which were last seen in May, all species accounted
for in the second season were present in at least one pool until July 2008. Marbled
Salamanders persisted in the greatest number of pools for the longest amount of time with
individuals being present in three (Albert Man 2, Letson Point 2, and Letson Point 3) out
six pools until June.
65
Spotted Salamander Adult Captures
Total Captures
2500
2000
1500
1000
500
Jun-08
Apr-08
Feb-08
Dec-07
Oct-07
Aug-07
Jun-07
Apr-07
Feb-07
0
Time (Months)
Adults at Natural Pools
Adults at Artificial Pools
Figure 4.6. Total captures of Spotted Salamanders at natural (n= 3) and artificial pools
(n= 3) in Jackson County, Alabama.
66
Jun-08
Apr-08
Feb-08
Dec-07
Oct-07
Aug-07
Jun-07
Apr-07
Feb-07
Total Captures
Marbled Salamander Adult Captures
800
700
600
500
400
300
200
100
0
Time (Months)
Adults at Artificial Pools
Jun-08
Apr-08
Feb-08
Dec-07
Oct-07
Aug-07
Jun-07
Marbled Salamander Metamorph Captures
Apr-07
800
700
600
500
400
300
200
100
0
Feb-07
Total Captures
Adults at Natural Pools
Time (Months)
Metamorphs at Natural Pools
Metamorphs at Artificial Pools
Figure 4.7. Total captures of Marbled Salamander at natural (n = 3) and artificial pools (n
= 3) in Jackson County, Alabama.
67
Jun-08
Apr-08
Feb-08
Dec-07
Oct-07
Aug-07
Jun-07
Apr-07
Feb-07
Total Captures
Marbled Salamander Emergent Captures
800
700
600
500
400
300
200
100
0
Time (Months)
Emergents at Natural Pools
Emergents at Artificial Pools
Figure 4.7 continued. Total captures of Marbled Salamander at natural (n = 3) and
artificial pools (n = 3) in Jackson County, Alabama.
68
Four-toed Salamander Adult Captures
70
Total Captures
60
50
40
30
20
10
Jun-08
Apr-08
Feb-08
Dec-07
Oct-07
Aug-07
Jun-07
Apr-07
Feb-07
0
Time (Months)
Adults at Natural Pools
Adults at Artificial Pools
Figure 4.7. Total captures of Four-toed Salamander at natural (n = 3) and artificial pools
(n = 3) in Jackson County, Alabama.
69
Red-spotted Newt Adult Captures
Total Captures
250
200
150
100
50
Jun-08
Apr-08
Feb-08
Dec-07
Oct-07
Aug-07
Jun-07
Apr-07
Feb-07
0
Time (Months)
Adults at Natural Pools
Red-spotted Newt Emergent Captures
250
Total Captures
Adults at Artificial Pools
200
150
100
50
Jun-08
Apr-08
Feb-08
Dec-07
Oct-07
Aug-07
Jun-07
Apr-07
Feb-07
0
Time (Months)
Emergents at Natural Pools
Emergents at Artificial Pools
Figure 4.9. Total captures of Red-spotted Newt at natural (n = 3) and artificial pools (n =
3) in Jackson County, Alabama.
70
Jun-08
Apr-08
Feb-08
Dec-07
Oct-07
Aug-07
Jun-07
Apr-07
Feb-07
Total Captures
Mole Salamander Adult Captures
500
450
400
350
300
250
200
150
100
50
0
Time (Months)
Adults at Artificial Pools
Jun-08
Apr-08
Feb-08
Dec-07
Oct-07
Aug-07
Jun-07
Apr-07
Mole Salamander Metamorph Captures
500
450
400
350
300
250
200
150
100
50
0
Feb-07
Total Captures
Adults at Natural Pools
Time (Months)
Metamorphs at Natural Pools
Metamorphs at Artificial Pools
Figure 4.10. Total captures of Mole Salamanders at natural (n = 3) and artificial pools (n
= 3) in Jackson County, Alabama.
71
Jun-08
Apr-08
Feb-08
Dec-07
Oct-07
Aug-07
Jun-07
Apr-07
Feb-07
Total Captures
Mole Salamander Emergent Captures
500
450
400
350
300
250
200
150
100
50
0
Time (Months)
Emergents at Natural Pools
Emergents at Artificial Pools
Figure 4.10. continued. Total captures of Mole Salamanders at natural (n = 3) and
artificial pools (n = 3) in Jackson County, Alabama.
72
Community Similarities
Similarities in community composition among the six intensively trapped pools
were compared using the Morisita’s Index of Similarity. Individuals captured in natural
versus artificial ponds were further compared using their average SVL, tail length, and
weight in a MANOVA. Calculated values for Morisita’s index range from zero to one,
where a score of one indicates complete community similarity. This index also takes
abundance into consideration, so communities with the same species but in different
proportions will have a score lower than one (Morisita, 1959). Each fenced natural or
artificial pool was compared against each of the other five fenced pools. Scores were
then grouped and averaged based on the comparisons of pools within themselves (natural
pools versus other natural pools and artificial pools versus other artificial pools). Scores
were also grouped and averaged based on the comparisons of natural pools versus
artificial pools. Each group of averaged scores for Morisita’s index was compared using a
MANOVA (Table 4.14 and 4.15). There was no significant difference when scores were
compared together or separately or when adult traveling out of pools were excluded
(Pillai's Trace= 0.82, F= 1.14, p= 0.60 and Pillai's Trace= 0.56, F= 0.32, p= 0.85,
respectively).
MANOVAs were run comparing the average SVL, tail length, and weight of
individuals of each species captured at natural pools to those captured at artificial pools.
Adults measurements were analyzed separately from emergent and metamorph
measurements to prevent biases between pools with a majority of captures in either age
group. Subsequently, if there was a significant difference between animal measurements
73
Table 4.14. Comparison of averaged Morisita’s Index of Similarity scores for fenced
natural and artificial pools. MANOVA Pillai’s Trace= 0.82, F= 1.14, Hypothesis df= 4,
Error df= 1, p= 0.60.
Pool
Origin
Versus Natural
Versus Artificial
Albert Man 3
Artificial
0.650
0.647
Horse/Letson
Artificial
0.618
0.727
Poplar Spring 1 Artificial
0.527
0.553
Mean ± SD
0.6 ± 0.09
0.7 ± 0.12
Albert Parker 2
Natural
0.725
0.790
Hiking Trail
Natural
0.715
0.565
Letson Point 3
Natural
0.785
0.635
Mean ± SD
0.7 ± .04
0.6 ± .06
F
3.28
0.73
P
0.144
0.441
Table 4.15. Comparison of averaged Morisita’s Index of Similarity scores for fenced
natural and artificial pools excluding adults traveling out of pools. MANOVA Pillai’s
Trace= 0.820, F= 1.14 Pillai's Trace= 0.56, F= 0.32, Hypothesis df= 4, Error df= 1,
p=0.85.
Pool
Origin
Versus Natural
Versus Artificial
Albert Man 3
Artificial
.740
.570
Horse/Letson
Artificial
.403
.325
Poplar Spring 1 Artificial
.600
.585
Mean ± SD
0.6 ± 0.17
0.5 ± 0.15
Albert Parker 2
Natural
.545
.570
Hiking Trail
Natural
.675
.657
Letson Point 3
Natural
.800
.517
Mean ± SD
0.7 ± 0.13
0.6 ± .07
F
0.57
0.88
P
0.493
0.402
74
at either type of pool, an ANOVA identified which variable caused the significant result
in the MANOVA. Several species exhibited a significant difference in average SVL, tail
length, and/or weight. Adult Mole and Zig-Zag Salamanders had no significant
differences in SVL, tail length, or weight. However, there were significant differences
among adult Spotted, Four-Toed, and Marbled Salamander body measurements between
the two types of pools (p= 0.012, p< 0.001, and p< 0.001, respectively) (Table 4.16).
Spotted Salamanders captured in natural pools had a significantly greater body mass than
Spotted salamanders captured in artificial pools (p= 0.004). Four-toed salamanders in
natural pools had a significantly longer SVL (p< 0.001) and a greater body mass (p=
0.043) when compared to measured individuals in artificial pools. And Marbled
Salamanders were significantly larger in natural pools than in artificial pools with tail
lengths (p= 0.03) and greater body mass (p= 0.016). Emergent and metamorph Spotted
Salamanders had no significant differences in measurements between natural and
artificial pools, where as, Mole and Marbled emergents and metamorphs did exhibit
significant differences between pools. Mole Salamanders were larger in artificial pools
than those in natural pools with significantly greater SVL and tail lengths, and greater
body masses in artificial pools (p< 0.001, p< 0.001, and p< 0.001, respectively). Marbled
salamanders had longer tails and greater body masses (p< 0.001 and p= 0.001,
respectively) in natural pools than in artificial pools.
75
Table 4.16. MANOVA comparing SVL, tail length, and body mass (mean ± SD)
of adults of each species captured at fenced pools.
Artificial
Natural
Variable
(n=3)
(n=3)
F
p
Spotted salamander
3.68
0.012*
SVL
87.6 ± 12.9
87.5 ± 11.3
2.44
0.896
TAIL
95.6 ± 12.2
97.1 ± 14.0
0.00
0.246
WEIGHT
17.8 ± 5.3
3.71
0.004*
19.2 ± 5.8
Mole salamander
1.03
0.381
SVL
54.2 ± 6.0
53.7 ± 5.9
0.99
0.318
TAIL
47.7 ± 6.7
47.7 ± 7.5
1.75
0.186
WEIGHT
6.9 ± 4.2
7.2 ± 10.6
0.15
0.700
Zig-zag salamander
1.81
0.162
SVL
35.2 ± 0.0
37.00 ± 5.00
0.25
0.618
TAIL
45.2 ± 0.0
35.95 ± 7.24
3.19
0.082
WEIGHT
0.9 ± 0.0
1.07 ± 0.50
0.22
0.642
Green salamander
ND
ND
SVL
No Captures (NC)
47.5 ± 3.9
ND
ND
TAIL
NC
48.1 ± 2.4
ND
ND
WEIGHT
NC
1.5 ± 0.1
ND
ND
Red-spotted newt
ND
ND
SVL
31.0 ± 0.0
NC
ND
ND
TAIL
39.0 ± 0.0
NC
ND
ND
WEIGHT
1.4 ± 0.0
NC
ND
ND
Four-toed
salamander
3.63
0.000*
SVL
36.7 ± 3.8
22.89
0.000*
39.7 ± 2.5
TAIL
45.1 ± 9.8
44.7 ± 14.9
0.06
0.808
WEIGHT
1.5 ± 0.5
4.12
0.043*
1.7 ± 0.6
Red salamander
ND
ND
SVL
Not Data (ND)
NC
ND
ND
TAIL
ND
NC
ND
ND
WEIGHT
ND
NC
ND
ND
Slimy salamander
ND
ND
SVL
72.0 ± 0.0
NC
ND
ND
TAIL
92.0 ± 0.0
NC
ND
ND
WEIGHT
12.5 ± 0.0
NC
ND
ND
Marbled salamander
13.24
0.000*
SVL
59.3 ± 8.1
61.7 ± 5.6
4.97
0.148
TAIL
39.4 ± 11.5
28.40
0.030*
44.2 ± 6.8
WEIGHT
7.1 ± 1.2
4.78
0.016*
6.3 ± 1.1
76
Table 4.17. MANOVA comparing SVL, tail length, and body mass (mean ± SD)
of emergents and metamorphs of each species captured at fenced pools.
Artificial
Natural
Variable
(n=3)
(n=3)
F
p
Spotted salamander
1.75
0.471
SVL
30.0 ± 0.0
22.0 ± 2.6
6.86
0.119
TAIL
28.0 ± 0.0
18.3 ± 3.2
6.78
0.120
WEIGHT
1.2 ± 0.0
0.5 ± 0.2
6.25
0.121
Mole salamander
142.18 0.000*
SVL
27.7 ± 8.4
264.38 0.000*
51.3 ± 4.3
TAIL
23.1 ± 5.5
274.26 0.000*
41.6 ± 5.8
WEIGHT
1.1 ± 1.1
411.83 0.000*
5.6 ± 1.1
Zig-zag salamander
ND
ND
SVL
No Captures (NC)
NC
ND
ND
TAIL
NC
NC
ND
ND
WEIGHT
NC
NC
ND
ND
Green salamander
ND
ND
SVL
NC
NC
ND
ND
TAIL
NC
NC
ND
ND
WEIGHT
NC
NC
ND
ND
Red-spotted newt
ND
ND
SVL
NC
38.0 ± 2.9
ND
ND
TAIL
NC
43.0 ± 8.5
ND
ND
WEIGHT
NC
1.9 ± 0.9
ND
ND
Four-toed
salamander
ND
ND
SVL
NC
NC
ND
ND
TAIL
NC
NC
ND
ND
WEIGHT
NC
NC
ND
ND
Red salamander
ND
ND
SVL
NC
NC
ND
ND
TAIL
NC
NC
ND
ND
WEIGHT
NC
NC
ND
ND
Slimy salamander
ND
ND
SVL
NC
NC
ND
ND
TAIL
NC
NC
ND
ND
WEIGHT
NC
NC
ND
ND
Marbled salamander
13.49 0.000*
SVL
33.2 ± 2.7
33.5 ± 3.0
0.92
0.337
TAIL
24.5 ± 4.3
28.62 0.000*
26.8 ± 3.9
WEIGHT
1.2 ± 0.3
11.99 0.001*
1.3 ± 0.3
77
Canonical Correspondence Analysis
Corresponding variables were identified using Canonical Correspondence
Analysis (CCA). CCA is only appropriate for use in PC ORD under certain conditions.
It is not useful for identifying environmental gradients, species spatial distribution among
sites, or identifying relationships between environmental gradients and community
compositions (Jongman et al., 1987). CCA instead, assumes a bell shaped relationship
between variables and species distributions and tests the hypothesis that there is no linear
relationship between these two things (Jongman et al., 1987). When these conditions are
met, CCA examines environmental factors and based on species composition and
abundance data input into matrices, assigns a weighted value to those environmental
variables based on their importance and influence on species data (Jongman et al., 1987).
Because I am exploring the relationship of species to artificial or natural pools under the
specific conditions of variables which I measured and have been shown to be related to
species and not evaluating gradients or their importance to community structure, the
weaknesses of CCA in PC ORD should not have affected my results.
In CCA 1 (Figure 4.11), the factors assessed were maximum depth, pH, area,
distance to forest edge, and origin. Pool type (origin) had to be dummy coded as 0 for
natural pools and 1 for artificial pools. I used species capture data from fenced pools in
this analysis. Approximately fifty percent of the variance in my species data is explained
by pool condition variables. Of that fifty percent, ninety-two percent is explained by
Axes One and Two. Maximum depth and pool type are represented on Axis One and the
distance to the edge of forest is represented on Axis Two. In the graphical output of
78
AMMA-Spotted Salamander
AMOP-Marbled Salamander
AMTA-Mole Salamander
HESC-Four-toed Salamander
NOVI-Red-Spotted Newt
Figure 4.11. Relationships between pool environmental features (MaxDepth= maximum
pool depth, DistancetoEdge= distance to forest edge, and Origin= pool type (natural
pools= 0, artificial pools= 1)) and salamanders captured based on canonical
correspondence analysis.
CCA, each variable represented on axes is depicted with a red arrow pointing in the
positive direction of a variable’s gradient. The importance of a variable to a species’ can
be identified by its proximity to a variables’ arrow or by drawing a perpendicular line
from a species point to a variables’ arrow. The distance from the arrowhead at which that
line intersects indicates the importance of the relationship of that variable to that species.
The closer to the arrowhead a line intersects, the stronger that relationship. According to
this diagram, Red-spotted Newts (NOVI) and Marbled Salamanders (AMOP) are
associated with deeper water and Mole Salamanders (AMTA) are associated with a
higher distance to the edge of forest. Four-toed Salamanders (HESC) seem to be
79
associated with deeper water, but also with a higher distance to forest edge and with
artificial pools. Spotted Salamanders (AMMA) appear to be strongly associated with
natural pool. Maximum area and pH are represented on a third axis but they only
represent six percent of the variation in the species data.
In CCA 2 (Figure 4.12), because pH and maximum area had little correlation with
my species data, I removed them and replaced them with conductivity and water
temperature. Again, I used the species data from the fenced pools. The overall
explanation of variance and the percentage of variance explained by the axes remained
the same but the composition of variables represented on both axes changed. In this
analysis, conductivity was represented on Axis Two along with distance to forest edge
and mean temperature was represented on Axis Three. Though Axis Two accounted for
twenty-four percent of the variation, there were no species strongly associated with
conductivity, but spotted and marbled salamanders appeared to share some association
with it. Mean temperature only represented six percent of the variation of my data.
To
examine environmental and microhabitat variables across all twenty pools I had to use
survey capture data. I divided variables by season (spring and fall) to account for
differences in microhabitat data between seasons. The CCA which had the highest
percent of variance explained with seventy-six percent, was the combination of survey
capture data and spring microhabitat variables (Figure 4.13, 4.14, and 4.15). Axis One is
composed of floating vegetation and accounts for forty-seven percent of the variation in
my species data. Rocks and aquatic vegetation are represented on Axis Two and logs are
represented on Axis Three, accounting for fourteen and eleven percent of the variation,
80
respectively. Ambystomid species and Red-spotted Newts seem to have no preference for
rocks and logs. However, both seemed to be associated with floating and aquatic
vegetation.
AMMA-Spotted Salamander
AMOP-Marbled Salamander
AMTA-Mole Salamander
HESC-Four-toed Salamander
NOVI-Red-Spotted Newt
Figure 4.12. Relationships between pool environmental features (Conductivity,
MaxDepth= maximum pool depth, DistancetoEdge= distance to forest edge, and Origin=
pool type (natural pool = 0, artificial pools = 1)) and salamanders captured based on
canonical correspondence analysis.
81
Figure 4.13. Relationships between pool environmental features in spring and salamander
captures based on the first and second canonical correspondence axes
Figure 4.14. Relationships between pool environmental features in spring and salamander
captures based on the second and third canonical correspondence axes.
82
Figure 4.15. Relationships between pool environmental features in spring and salamander
captures based on the first and third canonical correspondence axes.
83
DISCUSSION
Environmental Conditions and Microhabitat Variables
Artificial pools in my study area were overall deeper and had a longer
hydroperiod than natural pools. Pool depth can sometimes be used as an indicator of pool
hydroperiod (DiMauro and Hunter, 2002) and all but two artificial pools in this study had
a maximum depth of over two meters at some point during the inundation period. Deeper
waters allowed most artificial pools to retain water, in some cases, two months longer,
than natural pools in the area. This was true in both field seasons implying that depth can
be used as an indicator of hydroperiod here in northern Alabama also. Natural pools in
the area were all located within forest and under a primarily closed canopy. But because
most were drainage areas at low points in the forested terrain, all with the exception of
one had a maximum depth well below two meters. Pool filling periods also varied among
pools. Most pools were already retaining water when I began surveying during the first
season but during my second season of study, artificial pools began filling slightly earlier
than natural pools. Although artificial pools were in the open and more susceptible to
evaporation, the canopy cover above natural pools prevented the saturation of soils at the
base of pools required for them to flood until later in the season. Forest growth
immediately surrounding pools affect soil water dynamics, where evapotranspiration
84
negates the lower evaporation rates provided by pool shading (Brooks, 2004).
Hydroperiod is often quoted as an important deciding factors in larval success (DiMauro
and Hunter, 2002; Petranka et al., 2003; Welch and MacMahon, 2005; Vasconselos and
Calhoun, 2006). Pools which dry at accelerated rates or before larvae can metamorphose
and emerge into surrounding habitat can either cause individuals to develop at a more
rapid rate or mass larval mortality (DiMauro and Hunter, 2002). Though natural pools in
this study area dried before artificial pools, they generally persisted long enough for
individuals to develop and emerge and because there were no instances of mass larval
mortality at any natural pools in the area, thus suggests that pool breeding amphibians in
my study area were able to adjust to shorter hydroperiods. Natural pools generally had
similar species compositions and community similarities to artificial pools and despite
their shorter hydroperiod, natural pools also had greater adult immigration, more egg
deposition, higher larval counts, and more emergent emigration than artificial pools,
suggesting that hydroperiod is not necessarily the top deciding factor in amphibian pool
usage in this study. Area can also be used as an indicator of hydroperiod (Dimauro and
Hunter, 2002). But in several studies, it was not consistently correlated with hydroperiod
(Calhoun et al., 2003; Vasconcelos and Calhoun, 2006). This was also the case in
Jackson County. Artificial and natural pools displayed no significant difference in
maximum area even though hydroperiod was apparently different between the two types
of pool.
Elevation and pH were significantly (p=0.010 and p=0.026, respectively) different
between natural and artificial pools but were not correlated with species composition or
85
abundance at pools. Artificial pools were at a lower elevation and less acidic than natural
pools but when compared in a CCA, neither factor contributed to much of the variance in
my species data. None of the studies I encountered looked at elevation as a factor
contributing to amphibian presence. Because artificial pools were constructed by land
managers, the differences in their elevations was likely coincidental and were a result of
the location selected by land managers. Pools maintained acidity outside of the optimum
range for most aquatic wildlife (6.6-9.0) and the significant difference in pH between
pool types was unexpected. Though the artificial pools barely averaged a pH of 6 and
natural pools averaged a pH of approximately 5, egg masses are larvae did not seem to be
affected by this. In several studies comparing temporary pools, pH in artificial and
natural pools sampled in the same area did not differ significantly (Lehtinen and
Galatowitsch 2001; Braun, 2006). Braun attributed the similarities in pH among pools to
their source of water, as her pools were primarily spring fed. Because pools in Jackson
County are primarily fed by rainfall, this could have contributed to the variations in pH.
Shallower pools undergo more fluctuations in levels of pH over the course of a day and
often rise and fall several units as air and water temperatures increase and decrease
(Keeley and Zelder, 1998). Though artificial pools were less acidic than natural pools,
natural pools had higher fluctuations (SD= 0.36) as compared to artificial pools (SD=
0.19). The lower acidity of artificial pools could also be due to the fertilization of food
plots located near them or due to the exposure of underlying materials in the basins of
pools during their construction.
86
Conductivity was close to being significantly different (p= 0.118) and was higher
in artificial pools when fenced pools were compared. But when all twenty pools were
compared, conductivity was higher in natural pools and was no longer nearly significant
(p=0.58). In both types of pools, it was below the optimum range for most aquatic life
(50-1500µS), but I did not observe any adverse effects on any egg masses or larvae I
encountered. Conductivity usually rises with drying rates as ions are concentrated as
pools dry (Keeley and Zelder, 1998), supporting the accuracy of the larger comparison.
This implies the need for a larger sample when trying to accurately characterize pool
water chemistry. Conductivity can be used as a predictor for the presence of some
amphibians in some cases (Welch and MacMahon, 2005) but in other cases, it does not
significantly differ between types of pools (Lehtinen, 2001; Petranka et al. 2003). In
Jackson County, the differences that did occur between pools were likely caused by the
differences in hydroperiod and the higher drying rates of natural pools. In addition,
conductivity was not a large contributor to variance in species data indicating that
conductivity is not a good predictor of amphibian presence in the pools in this study.
Aside from environmental causes, some variations in my water chemistry data
could have been caused by my collection methods. Though I constantly took
measurements over the course of my study, I only took one measurement at one
haphazardly chosen point in each pool during surveys. Several studies (Lehtinen, 2001;
DiMauro and Hunter, 2002; Braun, 2006) only measured water chemistry parameters
once during their surveys at one point in study pools but other studies used several
randomly chosen points in pools to take measurements (Petranka et al., 2003; Welch and
87
MacMahon, 2005). While I feel the latter of the two methods would have provided a
more accurate characterization of pools, other studies which used methods similar to my
own are common and widely accepted.
All but two artificial pools were located in a relatively open area and situated an
average of seven meters from forest on one or more banks, with the closet pool being
three meters from the nearest forested bank and the farthest pool being twenty-four
meters away from forest. All ten natural pools were surrounded by forest. The lack
significance difference in the distance to edge between natural and artificial pools from
the all pool comparison to the fenced pool comparison may be due to the smaller sample
size resulting in less statistical power and a larger sample may have been needed to detect
the difference. In the twenty pool comparison, twelve pools were within forest and four
out of the six fenced pools were within forest. Distance of pools from other pools used
by amphibians have been shown to have effects in metapopulation and colonization
studies (Lehtinen, 2001; Trenham et al., 2001; Trenham and Shaffer, 2005; Braun, 2006)
and probably may have the same effects on a smaller scale, such as in my study. I did not
measure distances between pools, but some pools were kilometers from one another, as
pools in my study were concentrated in two separate areas. However, some pools within
each of these areas were likely within hundreds of meters of each other and could indeed
have some metapopulation activity as salamanders have been known to disperse over six
hundred meters from pools (Trenham and Shaffer, 2005). Pools which are more
accessible to amphibians are exploited more (Lehtinen and Galatowitsch, 2001;
Vasconcelos and Calhoun, 2006). The greater abundance of adult salamanders which
88
migrated into natural pools than into artificial pools in my study area can likely be
attributed to this factor.
Natural pools had more leaf litter than artificial pools. This could be as a result of
the closed canopy above them and also as a result of time since their formation as leaf
litter often accumulates in the bottoms of pools over time. It is also probably this closed
canopy which prevents these pools from having a large amount of submerged vegetation.
In most pools, submerged vegetation consists of grasses which persist from the dry
season (Keeley and Zelder, 1998). This was likely true for the pools in this study.
Because most grasses prefer direct sunlight, a closed canopy is not conducive for most
grasses to grow within a forested habitat (Ham and Townsend, 1997). Artificial pools,
however, were primarily located beneath little to no canopy cover, allowing for the
growth of grasses and similar flora to be uninhibited by the lack of sunlight during the
dry season. Most artificial pools actually resembled fields during the drought phase. In
addition to dead terrestrial vegetation, aquatic vegetation was also able to grow better in
open canopied pools than at pools with more canopy cover. Aquatic vegetation such as
algae thrives in the presence on direct sunlight. In addition to algae, seeds can be blown
in by winds during the dry season and lay dormant until pool soils became water-logged
and conditions are adequate for germination. Larvae utilize vegetation, leaf litter, and
other debris in the bottoms of pools for cover and to forage (Chadwick, 1950; Anderson
and Williamson, 1974; Ashton, 1977; Nyman, 1987; Petranka, 1998). Most natural pools
possessed high levels of litter and adult salamanders were more often captured at these
pools, suggesting the higher suitability of natural pools as breeding habitat. This finding
89
also implies that conditions which favor the young of a species also favors adults. But
the only habitat factors which contributed to variance in species data were floating leaves,
aquatic vegetation, and logs, none of which were significantly different between pools.
This also could have contributed to the overall similarity in species composition and
abundance at natural and artificial pools.
The remaining microhabitat variables were similar between pool types. I feel this
is likely due to the field method I used. I only had five classes to quantify vegetation
coverage, which may have been too broad to pick up on differences in these variables.
Lehtinen (2001) used seven classes of percent cover (0%, 10%, 25%, 50%, 75%, 90%,
100%). This method or one similar to it would have likely revealed more significant
differences and possibly yielded larger differences in factors which were different with
just five classes.
Artificial Pools as Suitable Salamander Breeding Habitats
Natural pools did demonstrate a higher overall usage by salamanders. There were
more breeding adults, larvae, and emergents captured at natural pools than at artificial
pools, but as far as species richness, natural and artificial pools were fairly similar.
Relative abundance at pools varied but there were several species which dominated at
both natural and artificial pools but the community similarity indices in pools were also
fairly similar. Poplar Spring 1 had the most captures among the artificial pools, had more
adult and emergent captures than several of the natural pools. It also had a different
dominant species than the five other fenced pools. Red-spotted newts dominated and
90
Poplar Spring 1 as opposed to an Ambystomid species, one of which dominated at each of
the other fenced pools. Although Albert Parker 2 was a natural pool, it had less captures
than several artificial pools in several species and age groups. Poplar Spring 1 was one
of the two artificial pools which were surrounded by forest and it was constructed in
1996, making it the oldest artificial pool. It had an abundance of emergent and
submerged vegetation and downed logs and was the deepest of the artificial pools. The
second artificial pool, Albert Man 3 had minimal vegetation within the pool and was
bordered by forest on only one of its banks. During the first trapping season, Horse Trail
1 was the third artificial pool. It had a moderate amount of vegetation and leaf litter
within the pool and was primarily surrounded by forest. Letson Point 2 which replaced
Horse Trail 1 and was the third artificial pool during the second season had minimal
canopy cover and little to no submerged vegetation and leaf litter. Of the fenced artificial
pools, it had the most vegetation, was the closest to forested land, and was the largest in
area and perimeter. Albert Parker 2 was the shallowest and the smallest of the fenced
natural pools. Its hydroperiod was not the shortest of the fenced pools so its low number
of captures was unexpected.
Species composition at most pools, natural and artificial, was similar. There was
only one species, the Zig-zag Salamander, which was present in all of the natural pools
but absent in all but one of the artificial pools. Spotted, Mole, and Marbled Salamanders
had the highest relative abundance at most pools. Poplar Spring 1 was the only pool
whose dominant species was the Red-spotted Newt. The most apparent difference in
species diversity and community similarity between natural and artificial pools was in the
91
total number of captures at each pool type. The indices I used to compare species
diversity among pools and community similarity between natural and artificial pools not
only looked at species composition, but they also took evenness in abundance into
account. Despite the fact that natural pools had more individuals captured overall, there
was no significant difference in their species diversity or in their community structure
when compared to artificial pools (p= 0.60).
To accurately understand individual capture rates for each species, total capture
numbers at each pool were grouped by age and direction of travel. Due to the large
volume of captured individuals during peak migration periods, I was unable to mark all
individuals which presented the possibility of counting individuals more than once. To
adjust for this possibility, analyses were performed on total capture numbers and on total
capture numbers with adults traveling out of pools excluded. Though there were only
approximately two hundred more individuals captured leaving pools than entering them,
separating these totals removed over two thousand individuals from the analysis causing
a marked change in the p-value (p= 0.11 to p= 0.83) but no change in the insignificant
difference of individual captures between natural and artificial pools when adults
emigrating were removed. Without a sure way of knowing how many individuals may
have been counted twice, it is hard to speculate on which analysis is more accurate.
Excluding adults traveling out eliminates the chance of counting individual twice but it
also eliminates many individuals which were only encountered once.
The individual fitness is often indirectly measured as the function of the
morphological features (Semlitsch et al., 1988), and then linked to environmental
92
conditions for estimating habitat suitability for a given amphibian species (Dimauro and
Hunter, 2001). Though there was no significant difference in a species’ selection of a
specific pool type, conditions could still be more favorable at an individual animal level.
Source-sink model (Pulliam, 1988) measures habitat suitability in terms of demographic
parameters. Vernal pools could be sink habitats (ecological traps) if they cannot support
successful breeding of salamanders that use these pools. There are general guidelines for
habitat to be considered suitable for pond-breeding salamanders as a group, but as
individual species they each have certain preferences (see species descriptions) which I
believe are reflected the varied fitness of some species. The average SVL, tail length,
and body mass varied by species between natural and artificial pools. Of the nine species
encountered, three species were in better physical condition in natural pools in at least
one age group, one was found to be in better physical condition in artificial pools in one
age group, and the remaining species showed no difference in either pool type or were
not abundant enough to be evaluated. Adult Spotted Salamanders had significantly
greater body masses in natural pools than in artificial pools (p=0.004). Similarly, adult
Four-toed Salamanders had significantly (p= 0.002) larger body sizes and weighed more
(p= 0.043) in natural pools. This could be due to both of these species’ preference for
undisturbed habitats (Micacchion, 2002) for breeding. In my study, most of the natural
pools were in relatively undisturbed areas when compared to the artificial pools in the
study. In addition, CCA strongly associated Spotted Salamanders with natural pools and
although Four-toed Salamanders were shown as more associated with artificial pools, the
pool at which they were the most abundant was the artificial pool which most resembled
93
the natural pools. This pool was surrounded by intact forest on all banks and was the
oldest of the artificial pools whose age was known. Both the adult and
emergent/metamorph life stages of Marbled Salamanders had significantly larger tails (p=
0.03 and p< 0.001, respectively) and greater body masses (p= 0.016 and p= 0.001,
respectively) in natural pools than in artificial pools. Marbled Salamanders prefer
undisturbed forested (Micacchion, 2002) surrounding their breeding pools and this may
have contributed to individuals’ better physical condition in natural pools than in artificial
pools. Mole Salamander emergents and metamorphs had significantly larger bodies and
tails and greater body masses (p<0.000, p<0.000, and p<0.000, respectively) in artificial
pools. CCA indirectly supported their preference for artificial pools. They were strongly
associated with a farther distance to forest edge and artificial pools were significantly
further from forest edge. Mole Salamanders are facultatively paedomorphic, meaning
that in certain conditions they can retain larval characteristics as breeding adults, but also
retain the ability to go through metamorphosis (Scott, 1993). As a result of this, many
larvae postpone metamorphosis until pools begin to dry (Semlitsch, 1988). Artificial
pools in my study area tended to dry later than natural pools and therefore had larger
metamorphic individuals increasing the overall average size of the species in this study.
There was also an apparent difference in the numbers of emergents and
metamorphs I captured in several species and again, I attribute these differences to the
species ecologies of individuals. Although I captured several thousand Spotted
Salamander adults, I captured no emergents or metamorphs. This may be due to the late
migration of Spotted Salamander adults. Their numbers at both natural and artificial
94
pools peaked in March. Spotted Salamander eggs gestate for up to eight weeks and with
a two to three month larval stage, most would not emerge until late June into early July.
Their emergence likely occurred after I stopped opening pitfall traps. And because larvae
and metamorphs most often utilize the littoral zone of the pool minnow traps were not
very effective in capturing them. Mole Salamanders are similar to Spotted Salamanders
in their early spring peak of adult movement. I did capture some metamorphs and
emergents late in the season indicating I may have missed the latter part of the
emergence. Marbled Salamanders represented the majority of my emergent and
metamorph captures. This is likely due to their status as fall breeders. Adults move into
pools and lay eggs before they fill, and likely before I began trapping. Larvae and
metamorphs are often well developed by the time other species hatch and because of their
larger size, they more often move in the open outside of the leaf litter. This likely
contributed to their higher capture rates in minnow traps. Because their larval period can
be as short as two months in the southern region of the country, they often emerge sooner
resulting in a larger window for me to capture emergent individuals. Four-toed
Salamanders were the least abundant and like spotted salamanders, I only encountered
adults of the species. I attribute this to the extremely short larval period of this species
(three to six weeks). This small window combined with the rareness of my encounters
with adults largely lowered the probability of my capturing a metamorphic or emergent
individual. My focus on the use of pitfall traps during the first trap season likely
accounted for my zero adult Red-spotted Newt captures during the first season. Adult
Red-spotted Newts are primarily aquatic, though they are able to survive on land. Most
95
pitfall newt captures were of emergent Red-efts, which are the terrestrial juvenile life
stage of the Red-spotted Newt. During the 2008 trapping season, I was able to more
intensively use minnow traps and my adult newt captures rose as a result of this effort.
96
CONCLUSION AND RECOMMENDATIONS
A main key to the success of a created vernal pool as a conservation strategy is
the use of target species (Sutter and Francisco, 1998). If looking to conserve several
species or a community of amphibians, a pool must provide habitat characteristics
conducive to the breeding ecology of a group of species as opposed to being specialized
for one or two individual species. If the aim is to bring back or prevent the loss of a
specific species, then pool specialization would be the goal. In the case of pools in
Jackson County, both natural and artificial pools seemed to appeal to a range of species.
Rare species were occasionally present at certain pools, but were not abundant enough to
label any pool a specialized environment. Of the pools whose age was known, the older
pools had a statistically significant higher diversity than the younger pools. However,
artificial pools in this study could be considered as successful in providing breeding
habitat for salamanders and were colonized by the same species which utilize the natural
pools in the same area.
Given the similarities in most natural and artificial pool environments and the
subsequent similarities in community compositions at most pools in my study, the
environmental conditions and microhabitat variables of a pool, regardless of a pool’s
origin, dictated its adequacy as viable habitat. Previous studies have indicated that the
major factors in the initial colonization of artificial pools are a pool’s ability to mimic the
97
hydrology and vegetative composition of established temporary wetlands in a given area,
its proximity to other pools, the availability of other breeding habitat, and the size of
amphibian population in an area (Calhoun et al., 2003; Vasconcelos and Calhoun, 2006).
Both natural and artificial pools have to go through these initial phase and though pools
were not constructed with these guidelines in mind, some have still flourished as
amphibian habitats. This suggests the natural succession of artificial pools into suitable
habitats over time. In 2003, Petranka found that it usually takes about 3 years for a pool
to be colonized fully by the amphibians present in a given area. Poplar spring 1 had more
captures, a higher species diversity than Albert Man 3, and is at least 4 years older.
Though Albert Man 3 is beyond the 3 year colonization period, a 2006 Maine study
concluded that 3 years of study at pool is not long enough to declare a pool a success or
failure. This leaves the possibility that some pools may just need more time for species
to begin utilizing them. While most of the artificial pools in this study range from five to
eight years in age, the most successful of the artificial pools was constructed in 1996
implying that it could take over ten years for a pool to reach its full potential though most
species colonize pools within the first three years of its construction (Petranka et al.,
2003).
This type on conservation specifically addresses the problem of habitat loss.
Even though there are no published studies demonstrating declining amphibian
populations in Alabama, habitat destruction and fragmentation are a constant threat to
amphibians everywhere. In cases where amphibian populations are healthy and stable,
these same strategies can be used as preventative measures. Because artificial
98
Diversity Indices Scores
Species Diversity and Abudance at Artificial Pools
1.2
1
0.8
Shannon-Weiner
0.6
Simpson's
0.4
0.2
0
7-8 Years
Albert Man 3
(133 Captures)
Unknown
12 Years
Horse/Letson Poplar Spring 1
(927 Captures) (2012 Captures)
Artificial Pools
Figure 6.1. Diversity indices as related to the age of fenced artificial pools in Jackson
County, Alabama.
pools in Jackson County had similar environmental conditions, species diversity, and
harbored similar communities as natural pools in the area, I believe they could be
considered as mitigation sites and though their function as replacement wetlands may be
limited. Because of their similarities, I also feel that they successfully filled their
intended purpose as amphibian havens the Skyline WMA and on the Forever Wild
property. Salamanders are opportunistic breeders and will exploit any environment that
presents conditions favorable for breeding (Braun, 2006) and therefore, given the proper
construction and time, I believe artificial pools can serve as conservation strategies in
Jackson County, AL.
Based on the results from this study, I would recommend:
99
1. A long-term monitoring of vernal pool use by salamanders in the area including a
greater number of fenced study pools. Only having six out of twenty pools with
drift fences provided substantial information at those pools but limited
information on a broader scale.
2. An inventory project of the habitat surrounding artificial and natural pools to gain
an understanding of population dynamics and community structure around pools
and to pinpoint potential locations for artificial pools in the future.
3. An intensive trapping study of larval development and emergent emigration to
accurately gauge the breeding success of artificial and natural pools in Jackson
County, AL.
4. The use of aerial photos, geographic information systems (GIS), and ground
surveys to locate natural vernal pools in the area so that the may be protected.
Though artificial pools were similar to natural pools in many ways, natural pools
were still better habitats overall.
5. An investigation into which landscape and land use factors in Jackson County,
AL effect vernal pool conditions and natural pool formation and their effects
semi-aquatic salamander migrations, breeding success and metapopulation
dynamics.
6. The development of guidelines for the future construction of artificial vernal
pools in Jackson County, AL.
100
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VITA
Chelsea N. Scott is the daughter of Patricia Harvard and Roy Lee Scott. She was
born in Baltimore, Maryland on June 16, 1984. She entered the undergraduate program
at Alabama Agricultural and Mechanical University in August 2002 and earned her
Bachelor’s of Science in Biology in May 2006. She continued into the graduate program
at Alabama A&M University in the Department of Natural Resources and Environmental
Sciences with the intent of earning her Master’s of Science.
111