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Plethodon metcalfi Brimley, 1912
Southern Gray-cheeked Salamander
Federal Protection: No US federal protection
State Protection: No Georgia state protection
Global Rank: G4
State Rank: S2
Element Locations Tracked in Biotics: Yes
SWAP High Priority Species (SGCN): No
Element Occurrences (EOs) in Georgia: 2
Habitat Summary for element in Georgia: Mesic, high elevational forests
The southern gray-cheeked salamander is a large woodland salamander (genus Plethodon), reaching total lengths of as much as 17.2 cm (6.8 in). Specimens of the Plethodon jordani and Plethodon glutinous complexes from northeastern Georgia exhibit considerable intraspecific variation of physical characters, especially within zones of hybridization, which may complicate the identification of certain individual salamanders. Within extreme northeastern Rabun County, P. metcalfi does not hybridize with the sympatric (overlapping geographic distributions) Southern Appalachian slimy salamander (P. teyahalee), and thus exhibits uniformly black sides and backs, pale gray chins and bellies, and lacks lateral or dorsal white markings (formerly P. jordani melaventris). Elsewhere, Georgia specimens of the southern gray-cheeked salamander possess lightly pigmented chins and dark gray bellies shading to a lighter bluish black or gray above, typically have pronounced irregular or rounded white spotting along the sides of the body and head, no dorsal markings, and occasionally possess many large irregular-shaped white markings on the under-surface between the forelimbs (formerly P. jordani rabunensis). Sexual dimorphism, typical of the genus Plethodon, has been reported for North and South Carolina populations of P. metcalfi; body lengths attained at sexual maturity average slightly larger for females compared to that of males. Individuals have between 14 – 16 costal grooves. Hatchlings and small juveniles (< 25 mm or ~1 in) are light brown to tan (matching the color of leaf litter); larger juveniles attain the same black dorsal pigmentation typical of adults and sometimes have conspicuous brassy flecking on the head and eyelids.
Within Georgia the southern gray-cheeked salamander co-occurs with three species of the slimy salamander (P. glutinous) complex with superficially similar appearances, including the Chattahoochee slimy salamander (P. chattahoochee), the Atlantic Coast slimy salamander (P. chlorobryonis), and the Southern Appalachian slimy salamander (P. teyahalee), within various portions of its distribution. Plethodon teyahalee occurring in extreme northeastern Rabun County, GA reaches maximum total lengths of 17.2 cm (6.8 in) approximating that of the southern gray-cheeked salamander, but can be distinguished from P. metcalfi and other members of the P. glutinous complex by the presence of very small white dorsal spots. Where Georgia populations of P. metcalfi and P. teyahalee are sympatric, there is no evidence of hybridization. Plethodon chattahoochee is a medium sized woodland salamander reaching total lengths of 13.2 cm (5.2 in). It also lacks dark pigmentation on the throat, and white or brassy spotting on its black back are either lacking or very reduced, however, its flanks are abundantly covered with white or yellowish spotting, contrasting it with southern gray-cheeked salamanders (that are not found in zones of hybridization). Occasionally, scant, tiny red spots are present on the upper surface of the forelimbs of this species as well. There is a wide hybrid zone where P. chlorobryonis is parapatric (geographic distributions that are partially overlapping) with P. metcalfi, making contact on the south side of Rabun Bald. Plethodon chlorobryonis reaches total lengths of 12.5 cm (~5 in), has very small, slightly brassy, white dorsal spots and abundant lateral white or yellow spotting.
The southern gray-cheeked salamander occurs in cool, mesic hardwood forests in mountainous terrain. Populations are typically associated with high elevations, but are found at the lowest elevations in the southern portion of the complex’s range (i.e., Georgia and South Carolina), where deep gorges and high annual precipitation provide suitable conditions for survival. Although these salamanders spend roughly 70 to 80% of their lives in underground burrows, they depend heavily on woody debris such as fallen logs and on an accumulation of leaf litter on the forest floor which function as refugia and as a foraging substrate.
Food items utilized by North Carolina populations include arthropods taken from the forest floor consisting of ants, millipedes, centipedes, spiders, springtails, mites, snails, and a variety of insect larvae.
The tails of large eastern Plethodon species, including those of the P. jordani complex, produce slimy secretions that are noxious and function as a deterrent to predators. Nonetheless, the Appalachian woodland salamander is occasionally preyed upon by a variety of predators, including birds, snakes, small mammals, and other salamander species. Studies have suggested that populations of members of the P. jordani complex exhibiting aposematic coloration (e.g., red pigmentation) are noxious to potential predators, while all black populations (P. metcalfi) seem to be only slightly noxious or not at all despite the presence of gland secretions (perhaps producing a smaller volume of noxious secretions).
The burrows inhabited by P. metcalfi, which are typically former rodent or insect burrows, or rotten root channels, are usually about 1 in (2.54 cm) in diameter and have been found to extend as far as 10 – 12 ft (3 - 3.6 m) deep. Members of the P. jordani complex are known to regularly forage above the forest floor by climbing plants and tree trunks; adults have been collected on trunks and low branches of shrubs up to 3.5 ft (1 m) from the ground and juveniles from the leaves of herbs to a height of 1 ft (0.3 m). Salamanders of the P. jordani complex are considerably more abundant and individual home ranges smaller (one individual for every 12.5 ft2 [1.16 m2]), where found in sympatry with members of the P. gluntinous complex (one individual for every 46.3 ft2 [1.16 m2]), with home ranges from 123 ft2 (11.4 m2) to 18.3 ft2 (1.7 m2) depending on age and sex. Appalachian woodland salamanders remain in subsurface retreats during the day and generally restrict their surface activity to moist forest floor microhabitats, emerging at night to forage on invertebrates within the leaf litter during rainy weather or when relative humidity is high. Individuals forage from burrow entrances when conditions are dry. Georgia populations often remain active on the ground surface throughout the winter months except during periods of freezing weather. These salamanders take refuge within subterranean burrows, where they do not feed, when the forest floor is dry or when temperatures are unfavorable.
Courtship of members of the P. jordani complex has been observed in the field from mid-July through early October, and usually occurs at night between dusk and dawn. Eggs of this complex have never been found in the wild; however, based on the presence or absence of gravid females in samples, as well as the condition of ovarian eggs of dissected specimens sampled, females presumably lay eggs within deep subterranean recesses in May. Sexually mature males develop prominent, saucer-shaped mental glands on the chin and cloacal papillae during breeding season. Some females reach sexual maturity during the summer three years after having been laid as eggs. It is estimated that about 25% of females mate and lay eggs when four and five years old. Females that are six years old and older appear to lay eggs in alternate years. Through the comparison of average numbers of ovarian eggs in gravid females to the average clutch of Florida P. glutinous, the average number of eggs with a clutch of the smallest sexually mature female of the P. jordani complex is estimated to be composed of approximately 10 eggs. Typical of the genus Plethodon, embryos undergo direct development within the egg, hatching as gilled larvae and metamorphosing into miniaturized versions of adults a few days after hatching. Since the smallest specimens of this complex have been collected in May, and because the eggs of most plethodontids require two months or more to hatch, it is thought that the newly hatched young remain below ground for approximately 10 months.
Adult specimens can be found by turning coarse woody debris on the forest floor during the day and by searching the forest floor at night. Surveys focused on researching the relative interaction of P. metcalfi and P. chattahoochee, including range boundaries of each of these species relative to each other, the extent to which these species are sympatric (overlapping geographic distribution), syntopic (occupying the same microhabitats), or allotopic (occupying different microhabitats), and the extent to which these species hybridize to the southwest of Rabun Bald, are needed to more broadly understand the ecology and distribution of these salamanders, and to document additional occurrences of southern gray-cheeked salamanders in Georgia.
The range of the Jordan’s salamander (P. jordani) complex is subdivided into some 22 geographically isolated populations. Genetic comparison of salamander populations within this complex has identified seven distinct species within different mountain ranges of the Southern Appalachians in parts of Virginia, Tennessee, Georgia, and both North and South Carolina. Two of these species (i.e., P. metcalfi & P. shermani) are known from Georgia.
While members of the P. glutinous complex are continuously distributed throughout the Southern Appalachians, they are absent at higher elevations within some P. jordani complex isolates (outside of Georgia), and there are varying amounts of elevational overlap between the two complexes. However, the extent to which this elevational exclusion occurs in Georgia is not clear. While some authors have suggested a pattern of contiguous allopatry (geographic ranges not overlapping) between these complexes, there is evidence of extensive hybridization within some populations, necessarily indicating that species distributions overlap at least within these areas. One notable example includes the contact of ranges of P. metcalfi and P. chlorobryonis in the vicinity of Rabun Bald, south of which there exists a wide hybrid zone; within this zone on and southwest of Rabun Bald at elevations above 2000 ft (610 m), some 85% of P. metcalfi specimens possess lateral white spotting (“rabunensis”). On and northeast of Rabun Bald, specimens occasionally exhibit brassy dorsal spotting. However, for most populations within the range of P. metcalfi hybridization with other species appears to be rare or absent, evidenced by the species’ range-wide tendency to be uniformly gray to bluish black above, lacking spotting or flecking pigmentation (“melaventris”). Within Georgia, for salamanders resembling P. metcalfi hybrids the incidence of darkly pigmented bellies decreases southwesterly and the incidence of lateral white spotting decreases northerly. The distribution of the southern gray-cheeked salamander may extend as far west as Brasstown Bald southeastern Union County, but the full geographic extent of P. metcalfi hybridization with P. chattahoochee is not fully known.
Numerous studies have documented detrimental short-term effects of forest management on populations of plethodontid salamanders, including those of the P. jordani complex. Timber harvesting (i.e., clearcutting, selective logging, or thinning) is responsible for the elimination or reduction of canopy shading of the forest floor, reduction of forest floor leaf litter depth and moisture, reduction in the availability of forest floor invertebrate prey, increased soil-surface temperatures, and reduced soil-surface moisture. However, prescribed burning of hardwood forest stands has been found to have no negative impacts on salamanders of the genus Plethodon despite short-term reductions in forest leaf litter depths and moisture.
Because of its restricted range-wide distribution and its somewhat peripheral distribution within Georgia, the southern gray-cheeked salamander is a species of conservation concern in Georgia. Populations of P. metcalfi found in Georgia occur largely on federal lands (Chattahoochee National Forest), which conveys some level of protection, and are thought to be secure.
As is characteristic of woodland salamanders (genus Plethodon), southern gray-cheeked salamanders remain within a terrestrial environment, not requiring bodies of water for reproduction; instead of water bodies, eggs are laid in moist microhabitats (e.g, subsurface cavities) and larvae exhibit direct development terrestrially. As a result, woodland salamanders can exist in habitats of smaller size than many other amphibian species. However, forest management that conserves areas with closed-canopy forests within the greater landscape mosaic are necessary to maintain healthy populations of these salamanders.
Ash, A. N., R. C. Bruce, J. Castanet, and H. Francillon-Vieillot. 2003. Population parameters of Plethodon metcalfi on a 10-year-old clearcut and in nearby forest in the Southern Blue Ridge Mountains. Journal of Herpetology 37(2): 445-452.
Brimley, C. S. 1912. Notes on the salamanders of the North Carolina mountains with descriptions of two new forms. Proceedings of the Biological Society of Washington 25: 135-140.
Hairston, N. G. 1950. Intergradation in Appalachian salamanders of the genus Plethodon. Copeia 1950: 262-273.
Hairston, N. G. and C. H. Pope. 1948. Geographic variation and speciation in Appalachian salamanders (Plethodon jordani group). Evolution 2: 266-278.
Highton, R. and R. B. Peabody. 2000. Geographic protein variation and speciation in salamanders of the Plethodon jordani and Plethodon glutinosus complexes in the Southern Appalachian Mountains with the description of four new species. Pp. 31-93, In: Bruce, R. C., R. G. Jaeger, and L. D. Houck, eds. The Biology of Plethodontid Salamanders. New York: Kluwer Academic/Plenum Publishers. 485pp.
Highton, R., G. C. Maha, and L. R. Maxson. 1989. Part 1. Geographic protein variation. Pp. 1-78, In: R. Highton. Biochemical evolution in the slimy salamanders of the Plethodon glutinosus complex in the eastern United States. Illinois Biological Monographs 57. 152pp.
Highton, R. and S. A. Henry. 1970. Evolutionary interactions between species of North American salamanders of the genus Plethodon: Part 1. Genetic and ecological relationships of Plethodon jordani and P. glutinosus in the Southern Appalachian Mountains. Evolutionary Biology 4: 211-241.
Martof, B. and R. L. Humphries. 1955. Observations on some amphibians from Georgia. Copeia 1955(3): 245-248.
Mittleman, M. B. 1951. American Caudata. VII. Two new salamanders of the genus Plethodon. Herpetologica 7: 105-112.
Thomas M. Floyd
T. Floyd, March 2023: original account