Reptiles of North Carolina
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NC Records

Plestiodon anthracinus - Coal Skink


Photo: Tom Ward
Photo: Tom Ward
Taxonomy
Class: Reptilia Order: Squamata Family: Scincidae Subfamily: Scincinae Synonym: Eumeces anthracinus
Taxonomic Comments: One of thirteen species in this genus currently recognized in North America (SSAR, 2017); four occur in North Carolina
Species Comments: Two subspecies have been described: P. a. anthracinus, the Northern Coal Skink, and P. a. pluvialis, the Southern Coal Skink (Smith and Smith, 1952; SSAR, 2017). These can be distinguished by differences in in the number of scale rows (Smith and Smith, 1952), but, as discussed by Palmer and Braswell (1995), populations in North Carolina appear to be intermediate in these characters. Ecologically, however, our populations appear to be confined to cool, montane habitats that are similar to those occupied northward by the Northern Coal Skink. The Southern Coal Skink, in marked contrast, occupies a wide range of warmer, low elevation habitats, occurring as far south as the Gulf Coast and extending westward into Texas, Oklahoma, and Kansas.

The subspecies were not considered valid by Brandley et al. (2012), though this study did not include samples from both presumed clades.
Identification
Description: This species can be identified as a skink by its smooth, polished scales and relatively short legs. Species in this genus can be highly similar to one another in coloration and pattern and photographs can be used to identify them only when specific parts of the body are shown in detail.
Field Marks: Coal Skinks differ in pattern from other members of this genus by having only four pale stripes instead of the five found in the others. The dorsal surface is an unmarked tan or darker brown, bordered laterally with a narrow pale stripe that is followed below by a wide band of blackish-brown and then by another narrow pale stripe. Little Brown Skinks are somewhat similar in coloration, but lack the narrow pale stripes separating the tan dorsal surface from the darker brown lateral band. Juveniles in our populations are similar to the adults in pattern and color but have blue or purplish-blue tails (Palmer and Braswell, 1995). In the Southern Coal Skink, juveniles are often blackish and lack the pale stripes found in the adults. Males of this species develop a reddish color on the sides of their heads during the breeding season, but their heads are only slightly wider than those of the females, unlike the much more marked widening seen in males of the other species in this genus.
Morphological Features: This species has a single postmental scale on the underside of the head, compared to two in the other members of this genus (see Figure 39 in Palmer and Braswell, 1995). This is the smallest member of this genus in North Carolina and the only one where males appear to be smaller than females (Hotchkin et al., 2001). Maximum head-body length in NC: 2.0" (50.7mm), males; 2.4" (60mm), females (Palmer and Braswell, 1995). Adults may be as much as an inch shorter than Common or Southeastern Five-lined Skinks and 3 inches shorter in comparison to Broad-headed Skinks. They are, conversely, larger than Little Brown Skinks with body lengths as much as 0.5" longer.
Technical Reference: Smith and Smith (1952); Palmer and Braswell (1995)
Field Guide Descriptions: Beane et al. (2010)
Online Photos:    Google   iNaturalist   GBIF
Observation Methods: This secretive, semi-fossorial species is rarely observed on the surface but can be found by overturning rocks. Drift fence sampling, such as used by Hotchkin et al. (2001) appears to offer the best way of finding this species. Cover board surveys are also likely to be productive.
Distribution in North Carolina
Distribution Comments: Almost all North Carolina records for this species come from the mountains; Palmer and Braswell (1995) mention only a single record from Wilkes County in the Piedmont province. A population studied by Hotchkin et al. (2001) at Lake Demorest in northeast Georgia -- presumably closely related to populations in southwestern North Carolina -- is located in the Piedmont at about 1,348' in elevation. The range in the North Carolina mountains appears to be divided into two or three separate areas, with the one in the southern mountains the most extensive. This pattern of disjunction characterizes the distribution of this species more generally, with large gaps between most areas that are occupied by both the northern and southern subspecies.
Distribution Reference: Palmer and Braswell (1995); NCMNS Herpetology Collection Database (accessed 2023-01)
County Map: Clicking on a county returns the records for the species in that county.
Key Habitat Requirements
Habitat: Coal Skinks appear to be closely associated with stands of mesic hardwoods, often occurring on north-facing slopes with plentiful surface rocks and close to streams, springs, ponds or other water bodies; Coal Skinks have been observed to dive into water to escape potential predators. Open areas are also used to some extent but usually where close to forests (Palmer and Braswell, 1995; Beane et al., 2010). A recent record from the Swannanoa Mountains seems to extend the range of habitats used by this species. Several individuals were observed in a stand of dry oak-hickory woodlands located close to a ridgeline and far from the nearest creek or seep.
Environmental and Physiological Tolerances: Coal Skinks have been recorded at Wayah Bald at an elevation of over 5,000' and their range extends northward along the Appalachians to the southern edge of Lake Erie in New York state. The primarily montane and northern distribution of the Northern Coal Skink indicates that warm and dry conditions may set the lower limit of its distribution. Populations of the Southern Coal Skink, on the other hand, are located exclusively at lower elevations and in warmer climates.
Biotic Relationships: Earthworms may be an important part of the diet of this species, based on captive observations by Hoffman (1944). Palmer and Braswell (1995) also report that a captive readily ate earthworms, along with termites, ants and ant pupae. This diet seems consistent with the mesic-to-wet micro-habitats used by this species.
Life History and Autecology
Breeding and Courtship: Mating has been observed in February and March in northeast Georgia (Hotchkin et al., 2001).
Reproductive Mode: As in our other species of Plestiodon, females lay their eggs under cover and stay with their nest until hatching. Palmer and Braswell (1995) report the females will bite the fingers of would-be egg collectors, indicating that defense of their eggs against predation is an important function served by nest attendance.
Terrestrial Life History: Coal Skinks have been observed from May to October in North Carolina (Palmer and Braswell, 1995). In northeast Georgia, they are active all during the year, with an apparent peak in activity in late winter and early spring, corresponding to the mating period (Hotchkin et al., 2001).
General Ecology
Adverse Environmental Impacts
Habitat Loss: Given the association of this species with cool, mesic forests, the effects of clear-cutting may be similar to that observed in salamander populations, i.e., a drastic reduction that may take years to recover from. Some of the gaps that are observed in its current range could be due to the massive cutting of eastern forests that occurred around the turn of the 20th Century. The warmer and dryer climate that will develop as the result of climate change is likely to cause a shift in range of this species to higher areas in the mountains.
Status in North Carolina
NHP State Rank: S2
Global Rank: G5
Status in North Carolina: SR
Populations: Populations of this species occur in two widely separated parts of the mountains, appearing to show the same major biogeographic split between areas north and south of the Asheville Basin/French Broad River shown in salamanders, Trechus ground beetles, and other montane species. Within each of those areas, populations are possibly split into still smaller areas rather than occurring more continuously, which concentrations of records within just a few sites.
Status Comments: This secretive species is difficult to study and much still needs to be known about its distribution and abundance in North Carolina (and elsewhere). The pattern of wide gaps between populations, however, appears to be fairly well established. Although the causes of this pattern are unknown, it suggests that this species has suffered major environmental impacts in the past, eliminating it from previously occupied areas.
Stewardship: Populations should be protected from clear-cutting and other human activities that open up the canopy of the cool, mesic forests preferred by this species.

Photo Gallery for Plestiodon anthracinus - Coal Skink

3 photos are shown.

Recorded by: Tom Ward
Buncombe Co.
Comment: Male		Recorded by: Tom Ward
Buncombe Co.
Comment: Male
Recorded by: Tom Ward
Buncombe Co.
Comment: Recorded near a ridgeline in a fairly dry stand of montane oak-hickory forest; Male