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Nettle
Lake Amphibian Restoration
Conservation Plan
Amphibians were censured at Nettle
Lake from May 9, 1995 through October 31, 1996. Species
presence was determined by visual sightings; five species
comprised this list. Only anurans (frogs or toads) were
sighted by this technique. However, most species of
salamanders require different sorts of sampling regimes
because of their fossorial lifestyles, such as removal of
leaf litter and systematic searching of quadrates by turning
over logs and rocks used as refuge. Thus, the results of
this survey do not mean that salamanders are not present at
Nettle Lake. More censuring, using techniques appropriate to
salamanders, is recommended to determine their status at
this site.
Ohio has a relatively diverse
amphibian fauna, consisting of 24 species of salamanders and
14 species of frogs and toads. Of these, five are designated
state-endangered, and two are designated of special
interest. Most of these listed species are highly localized,
and only historically found in one or a few counties.
However, the endangered Blue-spotted salamander
is found in extreme northwestern Ohio, quite possibly at
Nettle Lake. This species is seldom seen out of its breeding
season as it disperses into wooded areas and burrows under
rocks, into rotting stumps and logs, mats of moss and
vegetative debris, or in loose soil. In Maine, pools
selected for breeding are semi permanent with overhanging
bushes and grass, sphagnum moss margins, or leafy bottoms.
Sites are most often in or near deciduous or mixed forest,
and water depth is seldom more than 30-40 cm. The census
techniques most likely to determine the status of the
blue-spotted at Nettle Lake would be night driving, a
specific type of line transect method, during warm, rainy
April nights or systematic searches of vernal pools.
Another species probably occurring at Nettle Lake, although
not detected in the Survey, is the Redback
salamander. This species is the most ubiquitous
salamander throughout the greater part of its range,
although it is generally confined to forested areas. This
species is found throughout Ohio, and is most often seen in
spring beneath rocks and logs. Thus, further censuring, at
the appropriate time of year, is necessary to determine its
status at Nettle Lake.
Five anuran species were found at
Nettle Lake, ranging from most widespread generalist in the
country, the American toad, to a specialist rarely seen on
the ground, the Grey
Tree
frog.
The American
Toad is
cosmopolitan in its habitat requirements, can be found
anywhere from urban backyards to remote woodlands after they
disperse from breeding sites. This species seems to be
highly adaptable to environmental conditions. The Northern leopard frog,
also known as the “meadow frog,” is semi terrestrial,
but does require permanent bodies water such as streams to
over winter in. Although not state-listed, there are
indications that this species has declined in its range due
to over harvest - this is the species most often used for
dissection in high school biology. 
The Green frog is the most
abundant and widely distributed frog in Ohio. It seldom
ventures far from water and can typically be found on shores
and banks of ponds, lakes, and streams. The Bullfrog
is the most aggressively carnivorous of
these species. Its primary habitat requirement is permanent
water with abundant emergent and shoreline vegetation;
increased shoreline development for homes and recreation has
likely decreased its habitat at Nettle Lake and other
sites.
The Grey Tree frog
is the most specialized of the five species documented in
the Survey. It is seen rarely on ground, but perches on tree
and shrub branches. Its color provides excellent camouflage,
and it is hard to observe even when one hears its
vocalization at close range. It inhabits forested areas near
shallow water, and breeding sites are variable and include
both permanent water and temporary pools or swamps. As
stated above, the Blue-spotted salamander
is the most likely endangered species present at Nettle
Lake, but more censuring is required to determine its
status.
Regionally, the two most devastating
effects on amphibians have undoubtedly been conversion of
original forests (The Great Black Swamp) to agriculture, and
loss of wetlands. The combined practices of agriculture,
from regular plowing, pesticide and fertilizer applications,
and highly mechanical harvesting, create inhospitable
habitat for adult and juvenile amphibians during their
terrestrial stages, whether that be foraging in the summer,
or hibernating in the winter. The best solution for
amphibians on these sites would be to let vegetation
regenerate in areas as large as possible, to restore the
original plant community. For many reasons, obviously this
is unrealistic. Perhaps a workable compromise might be to
survey vernal pools and other potential breeding areas in
the spring (warm rainy nights would be best), and determine
which wetlands are being used by which species for breeding
purposes. Terrestrial habitat could then be restored around,
or very near, to pools that are used significantly.
 The use of agrochemicals is
potentially devastating to amphibians, because their highly
permeable skin. Pesticide sprays, including DDT, which was
produced in enormous quantities from 1940’s onward, have
received most the attention. Preliminary evidence suggests
that natural ponds exposed to run-off from fertilizers
contain concentrations of nitrate ions that are especially
toxic to anuran larvae. Moreover, fertilizer use often
occurs with the worst possible timing, during adult
migration to breeding ponds.
Direct killing of amphibians by humans for food or bait, or
over collecting have negatively affected amphibians in
certain parts of their range. Of the species detected in the
Biological Survey, the Bullfrog
and the Leopard frog are the two
probably most affected by these practices in Ohio.
Accidental mortality as happens on roads when
amphibians are migrating to and from their breeding sites
can be substantial; mortality estimates in the common toad
in Europe, range anywhere from 4-50% of adults, depending
upon the volume of traffic. Various solutions to this
obvious problem of human-caused mortality have ranged from
volunteers carrying animals across roads, to permanent
underpasses with drift fences to direct migrating
individuals under roads as has been done in Massachusetts
and Florida.
Based on these observations, the
following recommendations are for restoring amphibian
populations to Nettle Lake. Further censuring is needed.
Censuring is required to establish the  presence or absence
of the Blue spotted
Salamander, a state-endangered species, and the Redback Salamander
or possibly other salamander species. Also, it is important
to note that the Biological Survey just recorded a
particular species as present - this says nothing about its
relative abundance. Certainly practices around Nettle Lake
in the last several decades have been detrimental to
amphibians. Agriculture and associated land-use practices
and shoreline development that have accompanied the building
of homes around the lake have been the most important
human-caused perturbations. It might be worth considering a
survey on the abundance of various amphibians. Various
methods could be used, including aural surveys of
vocalizations of mates anurans on breeding grounds. This
type of information would not only give information on the
relative abundance of individuals, but also the extent to
which specific wetlands are used.
When important breeding sites are
identified at Nettle Lake, specific recommendations would be
to limit pesticide and fertilizer use in these areas at  the
time when individuals are migrating to or from them. Native
vegetation could be restored around and adjacent to the most
important sites. Mortality during migration could be
controlled - this would not be hard to do with a few hearty
enthusiastic individuals, as migration for many species is
generally limited to a few warm rainy spring nights.
Depending on the numbers of amphibians migrating,
consideration might be given to establishing permanent
tunnels under roads at a few high-traffic sites.
Critical in this plan, though, is
protection of clustered breeding sites. A study in Sweden
indicated that the probability of extinction of amphibian
populations increased with obvious factors, such as pond
destruction. However, factors such as distance from nearest
site with breeding individuals, and connectivity of breeding
habitat patches was also critical. This is known as
meta-population dynamics, ponds are habitat patches that are
sometimes occupied, and sometimes not. Many local
populations are not self-sustaining, but depend upon
individuals immigrating from adjacent sites. In a state that
has lost so much of its original wetlands as Ohio,
conserving amphibians ultimately means conserving as many
remaining wetlands as possible.
Amphibians observed during Nettle Lake Biological Survey,
May 9, 1995-October 31, 1996
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continue reading about amphibians, and what we can do
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