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Ambystoma tigrinum (Green, 1825)
Eastern Tiger Salamander
Federal Protection: No US federal protection
State Protection: No Georgia state protection
Global Rank: G5
State Rank: S3S4
Element Locations Tracked in Biotics: Yes
SWAP 2015 Species of Greatest Conservation Need (SGCN): Yes
SWAP 2025 Species of Greatest Conservation Need (SGCN): Yes
2025 SGCN Priority Tier: Moderate Conservation Concern
Element Occurrences (EOs) in Georgia: 83
Habitat Summary for element in Georgia: Isolated wetlands for breeding; variety of open, upland habitats; CP-sandhills, oldfields, dry pine savanna
Eastern tiger salamanders are the largest terrestrial salamanders in eastern North America (18-21 cm or 7-8.25 inches total length). This salamander species is characteristically colored with irregularly shaped and spaced yellow to beige blotches, that are often elongated and extend far down the sides of the body with a black to dark brown background; these function as a disruptive camouflage pattern (breaking up the body’s outline). The belly is an olive-yellow color. Adults have conspicuously broad heads and relatively small eyes. Hatchlings (13-17 mm or ~0.5 inches in total length) have paired blotches along the back and unpigmented bellies. Larvae have large, rounded heads, blunt snouts, and bushy gills. Older larvae are dull green to a dusky color on the back and sides often with black spots and a white belly. Juvenile salamanders acquire adult coloration around one month after metamorphic transformation is complete.
Georgia is home to six “mole” salamander species (genus Ambystoma) including the eastern tiger salamander which is sympatric with (overlapping geographic distribution), but not always syntopic with (occupying the same microhabitats) all other sister species (i.e., reticulated flatwoods, A. bishopi; frosted flatwoods, A. cingulatum; spotted, A. maculatum; marbled, A. opacum; mole, A. talpoideum). None of these species, except perhaps the spotted salamander could be easily confused with the tiger salamander. Spots of A. maculatum that are usually vivid orange and yellow, may instead sometimes be pale white in color. However, in contrast to the tiger salamander’s irregular blotches, the spots of the spotted salamander form irregular rows, occur only on the back, and the belly is gray. Though all ambystomatid larvae have a similar body form, no other species has such a relatively broad head compared to tiger salamander larvae (as viewed from above). Further, of those mole salamander larvae native to Georgia, the chin and/or throat of both marbled and the mole salamanders are pigmented, whereas chins and throats of the frosted and reticulated flatwoods, spotted, and tiger salamanders are without pigment. Larval of both flatwoods salamander species possess prominent, dark lateral stripes setting them apart from tiger salamander larvae and tiger and spotted salamander larvae can be differentiated by the spotted salamander larvae’s rounded toes and the flattened toes of the tiger salamander larvae.
Tiger salamanders are tolerant of agriculture and can successfully utilize farm ponds, road-side ditches, quarry ponds, etc. that do not dry down, but not if these impoundments are stocked with predatory fish. This species tends to be associated with open woodlands and open fields rather than with upland forests. Exclusion of fire from the landscape within both the Coastal Plain and elsewhere in Georgia has undoubtedly reduced the amount of the landscape that is currently suitable for this species. Besides the typical need for fishless wetland basins to successfully reproduce, suitable wetlands must be within a matrix of adjacent suitable upland habitat. Adults actively excavate their own burrows, but are only able to successfully do so within deep friable (i.e., easily crumbled, loose) soils, which is consequently a characteristic of upland habitats where this salamander is found. Though active on the surface during rainy nights, adults spend the majority of their lives within mammal burrows or burrows of their own construction which can be fairly shallow to as deep as 6 feet (2 m) and as long as 12 feet (4 m).
Relatively little is documented regarding the diet of adult eastern tiger salamanders, but it is known that they consume insects, worms, and snails. Non-breeding adults often forage on aquatic insects and tadpoles within the water column of fishless ponds – their light-colored bellies function as countershading camouflage allowing individuals to blend into sunlight coming from the water’s surface and avoid alerting potential prey. Tiger salamander larvae are generalist, gape-limited predators of aquatic organisms (i.e., prey that they consume is limited only by the size of their mouth). They prey on a variety of invertebrates including zooplankton, daphnia, worms, aquatic insect larvae and adults, mollusks, and crayfish. They also prey on frog and toad tadpoles, small fish, and other salamander larvae.
Adult males are the same size or slightly smaller than females, but typically have longer tails. Males in breeding condition have noticeably swollen cloacae and accentuated keeled tails. Immigration to breeding wetlands typically occurs 2-8 weeks earlier for males (November-February) than for females and males tend to outnumber females by as much as 5:1 within breeding congregations suggesting that females do not necessarily emigrate to breeding ponds, nor breed annually. Eggs (averaging of 40-60 in number) are laid in clusters on aquatic substrates such as emergent vegetation. Eggs hatch within 20-50 days depending on water temperature. Neoteny (a condition in which sexual maturity is attained while retaining larval characteristics [i.e., gills, pronounced tail fin, etc.] without typical metamorphic transformation into a terrestrial form) is not known to occur in Georgia populations of the tiger salamander. Eastern tiger salamander larvae grow faster than all other ambystomatid larvae and quickly become the top aquatic predator within any given breeding wetland. Growth rate, length of the larval period, size at the time of transformation, and duration of metamorphosis vary with water temperature, larval salamander density, availability of prey, presence of competitors, and wetland hydroperiod. Therefore, the timing of larval transformation and juvenile wetland emigration ranges widely from April-September.
Considering that the presence of tiger salamanders outside of the Coastal Plain in Georgia was not documented before 2009, much additional survey work needs to be conducted in the western part of the state including portions of the Piedmont, Pine Mountain Ridges, Ridge and Valley, and Cumberland Plateau (particularly areas underlaid by limestone strata with friable sandy or loamy soils). Since adults can reliably be captured only during migration to and from breeding ponds and encountering an adult (or metamorphosed juvenile) is strictly by chance, surveys should focus on the identification of suitable breeding wetlands (that are in proximity to intact upland habitats) accompanied by area-constrained and/or time-constrained searches for larvae within the water column of these wetland basins (with dip nets) during the appropriate time of the year (January-March). Suitable wetlands typically will only be filled with water for a portion of the year (and lack connectivity to larger bodies of water) or be fish-free. The identification of potential isolated ephemeral wetlands may be accentuated by GIS analysis of LiDAR data to detect subtle differences in topography (including depression basins) within the aforementioned regions. Suitable habitat for the species may occur and the species may well have thus far gone undetected within government landholdings including wildlife management areas and U.S. Forest Service ownership within northwestern Georgia.
Before the latest taxonomic division of the tiger salamander complex (with six recognized subspecies), the tiger salamander was the widest distributed salamander species, ranging throughout much of temperate North America. Genetics research published in the mid-1990s, demonstrated that the California tiger salamander (A. californiense) was a unique species and all other sister subspecies were more appropriately grouped as subspecies of the western tiger salamander (A. mavortium). No subspecies of the eastern tiger salamander are currently recognized. Even so, under current taxonomic designations, the range of the eastern tiger salamander (A. tigrinum) is currently the widest ranging salamander species in North America. Though the eastern tiger salamander was long known to range throughout much of neighboring Alabama, until recently within Georgia, this species was thought to be confined to the Coastal Plain. Since 2009 the tiger salamander has been documented from Georgia’s Cumberland Plateau and Ridge and Valley physiographic provinces as well.
The greatest threat to existing eastern tiger salamander populations is the alternation of wetlands through forestry or agriculture. Both hydrologically intact ephemeral depressional wetlands and suitable, adjacent upland habitats are required to support the life history of ambystomid salamanders. Altered hydrology, in association with fire exclusion from wetland basins, allows growth of woody vegetation and eventual canopy closure. A relatively open canopy and ample sunlight is necessary to maintain grasses, sedges, and other herbaceous plants in the wetland basin supporting a healthy aquatic invertebrate prey base. Shaded wetlands accumulate organic matter which can decrease the pH of the water column. Wetlands in such condition are avoided by adult tiger salamanders as breeding sites. Habitat loss has effectively isolated remaining populations of tiger salamanders on the landscape. Though tiger salamanders can successfully breed in permanent wetland basins such as farm ponds, the introduction of predatory fish reduces or eliminates tiger salamander populations. Fortunately, laboratory experiments have concluded that ambystomid salamanders are resistant to and are considered to be non-carriers of salamander chytrid fungus (Batrachochytrium salamandrivorans) [or Bsal]. Additionally, proteins found in skin secretions have been found to inhibit the growth of amphibian chytrid fungus (Batrachochytrium dendrobatidis) [or Bd].
| Threat 1 | Threat 2 | Threat 3 | |
|---|---|---|---|
| General Threat | Natural system modifications | Natural system modifications | Agriculture & aquaculture |
| Specific Threat | Other ecosystem modifications | Fire & fire suppression | Livestock farming & ranching |
In Georgia, the eastern tiger salamander is known to occur on military installations (i.e., Ft. Benning, Ft. Gordon, Ft. Stewart), wildlife management areas and conservation lands (e.g., Alapaha River WMA, Chickasawhattchee WMA, Di-Lane WMA, Mayhaw WMA, Pine Log WMA, Sandhills WMA, Ichauway Plantation) and within regions on the landscape of high conservation value (e.g., Tallahassee Hills, Valdosta Limesink Region). Properties supporting this species that are not currently in public ownership, particularly within areas outside of Georgia’s Coastal Plain containing isolated wetlands confirmed to be breeding ponds for this salamander, should be targeted for protection (e.g., establishment of conservation easements, property purchase, etc.). Following the discovery of occurrences outside of Georgia’s Coastal Plain in 2009 and again in 2013, the deficiency in information relative to the species’ conservation status and statewide distribution, particularly outside of the Coastal Plain, was recognized; the species was added to the list of High Priority Species within the 2015 revision of Georgia’s Wildlife Action Plan.
It is thought that eastern and western lineages of the tiger salamander were isolated between 0.75 and 2.1 million years ago. Ancestry of today’s tiger salamander populations was dictated by post-glacial colonization from these two lineages. It is postulated that the barrier to gene flow between eastern and western lineages was the Apalachicola River basin, yet genetic analysis shows that populations in the western Georgia Coastal Plain (i.e., Chattahoochee County) are surprisingly more closely related to populations from the Florida Panhandle (i.e., the western clade) than populations in the eastern Georgia Coastal Plain (i.e., the eastern clade). To improve understanding of the distributional history of the tiger salamander, tissue samples should be collected from populations from different regions of Georgia (including various locations from the eastern and western Coastal Plain, and from northwestern Georgia), and comparative genetic analyses conducted. If tiger salamander populations from northwestern Georgia prove to be more closely related to populations from Alabama’s Ridge and Valley it may very well indicate that tiger salamanders never inhabited the intervening area between Georgia’s Ridge and Valley and Coastal Plain (i.e., Georgia’s western Piedmont) which would inform conservation of the species going forward.
The establishment of long-term land conservation (i.e., conservation easements) aimed at protecting breeding ponds and the surrounding uplands known to harbor tiger salamanders within the Ridge and Valley should be pursued. Known populations of the tiger salamanders in Georgia’s Ridge and Valley should be monitored periodically to confirm the species’ continued presence and to determine possible changes in abundance over time at each site. Further concerted survey effort within the predicted range in Georgia, particularly within western Georgia outside of the Coastal Plain is suggested to determine the full extent of the species distribution, abundance, conservation status, and needed management actions for specific populations.
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Semlitsch, R. D. 1983. Structure and dynamics of two breeding populations of the eastern tiger salamander, Ambystoma tigrinum. Copeia 1983(3): 608-616.
Shaffer, H. B. and M. L. McKnight. 1996. The polytypic species revisited: genetic differentiation and molecular phylogenetics of the tiger salamander Ambystom tigrinum (Amphibia: Caudata) complex. Evolution 50(1): 417-433.
Thomas M. Floyd
T. Floyd, February 2023: original account
