Amphibians of North Carolina
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Plethodontidae Members:
NC Records

Plethodon serratus - Southern Red-backed Salamander

Taxonomy
Class: Amphibia Order: Caudata Family: Plethodontidae Subfamily: Plethodontinae
Taxonomic Comments: Populations of a wide-ranging and geographically variable small Plethodon with a reddish dorsal stripe were traditionally thought to comprise a single polytypic species, the Red-backed Salamander (P. cinereus), with three recognized subspecies. Highton and Webster (1976) and Highton and Larson (1979) analyzed protein variation and found that two of the southern forms (P. c. serratus, P. c. polycentratus) differed substantially from a wide-ranging northern form (P. c. cinereus). They documented fixed allelic differences for five loci, and recognized the southern forms as a separate species, P. serratus.

Plethodon serratus consisting of populations that are found in four widely disjunct regions that include the southern Appalachian Mountains and Georgia Piedmont, the Ozark Plateau of southeastern Missouri, the Ouachita Mountains of southeastern Oklahoma and west-central Arkansas, and the Southern Tertiary Uplands of central Louisiana. These geographically isolated groups differ in color patterning, the modal number of costal grooves, and the frequency of striped versus unstriped morphs (Highton and Larson 1979, Petranka 1998). Newman and Austin (2015) provided evidence that P. serratus originated in the Appalachian Mountains and subsequently expanded southward and westward across the Coastal Plains during the cooler glacial periods. This species has probably undergone several periods of range expansion and contraction during the Pleistocene and is currently in a contraction phase.

A molecular analysis by Thesing et al. (2016) revealed five geographically distinct lineages within P. serratus that were distributed across the four geographic isolates. These included two parapatric groups in the Ouachita Mountains that did not form a monophyletic group, with one being more closely related to Louisiana populations. In a related study Newman and Austin (2016) used a different set of genetic evidence -- next-generation sequencing technology using ultraconserved elements -- and found seven major genetic lineages. They recommended that all be treated as distinct species. If Plethodon serratus (sensu lato) is eventually split into numerous species, our southern Appalachian population will be given a different name since the type specimen was the Interior Highlands. Here we continue to recognize a single, geographically variable species, with the understanding that additional taxonomic changes may occur in the future.
Species Comments:
Identification
Description: The Southern Red-backed Salamander is a small Plethodon with a rounded tail that comprises about 50% of the total length. Both striped and unstriped color morphs occur in some populations (Petranka 1998). The striped morph has a dark brown dorsal ground color with a red or orangish red stripe that extends from the head to the tail tip. The dorsal stripe is serrated along the back in populations in the Ouachita Mountains and Louisiana, but tends to be straight-edged or weakly serrate in populations elsewhere, including North Carolina. The unstriped morph is brown above and usually has small amounts of red spotting on the back, sides, and belly. The sides of both morphs are brown and have varying amounts of white spotting, while the belly is mottled black and white and sometimes has small amounts of red pigment near the limb insertions (Petranka 1998). The unstriped morph is rare in North Carolina and most populations contain only striped individuals (Beane et al. 2010).

The number of costal grooves ranges from 18-21 and varies regionally. The adults range from 6.5-10.5 cm TL and females in Georgia, North Carolina, and Tennessee average 5-7% larger in SVL than males (Camp 1988). Sexually active males have swollen tissue around the nasolabial grooves and a crescent-shaped mental gland near the apex of the lower jaw. The hatchlings have proportionately shorter tails than older animals and average 12.5 mm SVL (Camp 1988). This species closely resembles the Eastern Red-backed Salamander (P. cinereus) and is best identified by geographic locality. Plethodon serratus is found south and west of the French Broad River, while P. cinereus is found east and north of the French Broad.
Online Photos:    Google   iNaturalist
Observation Methods: Individuals can be found beneath cover objects during the day during the cooler months of the year, and foraging at night during bouts of relatively warm, wet weather.
AmphibiaWeb Account
Distribution in North Carolina
Distribution Comments: The Southern Red-backed Salamander consists of four widely disjunct geographic groups that include the southern Appalachian Mountains and Georgia Piedmont, the Ozark Plateau of southeastern Missouri, the Ouachita Mountains of southeastern Oklahoma and west-central Arkansas, and the Southern Tertiary Uplands of central Louisiana. Populations in North Carolina occur west and south of the French Broad River and have been found in most of the southwestern counties west of the French Broad. These are members of an eastern isolate that ranges from southwestern North Carolina and adjoining areas of eastern Tennessee southward to west-central Georgia and northeastern Alabama.
Distribution Reference: Camp 1986, Thesing et al. 2016
County Map: Clicking on a county returns the records for the species in that county.
GBIF Global Distribution
Key Habitat Requirements
Habitat: Populations in North Carolina and other areas within the range of the eastern isolate are typically found in mesic hardwood or mixed hardwood-conifer forests. Camp (1986) reported that mature hardwood forests provide optimal habitats for this species in the Georgia Piedmont.
See also Habitat Account for General Montane Mesic Forests
Life History and Autecology
Breeding and Courtship: The adults are most active on the ground surface from the fall through the spring months and appear to restrict mating to the winter and spring months. Courtship behavior has not been described. Most of our knowledge about the life history of eastern populations is from Camp's (1988) study that focused on a population in the Georgia Piedmont, but also included data for southern Appalachian populations. He found females with spermatophores in their cloacae from February-March in the Georgia Piedmont, and during December in the southern Blue Ridge. Changes in the size of the male's testes were also consistent with a winter and spring breeding season. Herbeck and Semlitsch (2000) reported that breeding in Missouri populations also likely occurs from December through March. The sex ratios for all populations that were studies by Camp (1988) did not differ significantly from 1:1.
Reproductive Mode: Females are active on the ground surface during the cooler spring months, but move underground with the arrival of hot weather. They presumably lay their eggs in underground burrows or cavities and brood their young, but nests have not been discovered in the wild. Camp (1988) buried gravid females underground in containers, and two individuals produced clutches of five eggs each during July. The remaining females did not oviposit and resorbed their eggs. The mean number of mature ova in females from the Piedmont and Blue Ridge populations both averaged 5.5, and clutch size was independent of the female's SVL. Camp (1988) found that females in both the Piedmont and southern Appalachians reproduce annually.
Terrestrial Life History: Juveniles in the Georgia Piedmont first emerge from their underground summer retreats in late October, while adults surface a bit later in early November (Camp 1988). Individuals can be found in leaf litter and under logs and rocks from November through March where they forage on small invertebrates and seek mates. Camp and Bozeman (1981) found a variety of invertebrates in Georgia specimens. Ants and beetles were the most volumetrically important prey. Other food items included snails, annelids, mites, spiders, pseudoscorpions, millipedes, centipedes, isopods and members of several orders of insects. The adults become increasingly difficult to find in April and the juveniles disappear beneath ground by mid-May with the onset of hot weather.

The length of the juvenile stage is poorly documented, but juveniles in the eastern isolate probably reach sexual maturity about 2 years after hatching based on studies of P. serratus in Missouri (Herbeck and Semlitsch 2000) and closely related species such as P. cinereus elsewhere (Petranka 1998). Mature males that Carlos (1988) collected in the Georgia Piedmont ranged from 33-45 mm SVL, while mature females ranged from 33-47 mm SVL. Mature males and females in populations from the Blue Ridge varied from 33-39 SVL and 35-46 mm SVL, respectively.

General Ecology
Population Ecology: Mechanisms that regulate local population size are poorly documented, but Mathis et al. (1998) found that resident adults from a Missouri population showed behaviors that are consistent with being territorial. Territoriality in the field could potentially set an upper limit on local population size by limiting access to food, shelter, and mates. Camp (1999) studied an eastern population in Georgia using staged encounters and found that levels of aggression were highest during the winter months when the adults are actively foraging and seeking mates on the ground surface. Residents exhibited a distinct advantage over intruders, which also suggests that the adults are territorial. This species can be very abundant at sites that provide optimal conditions for growth and survival. Semlitch et al. (2014) estimated densities in the Ozarks of Missouri to be 0.73-1.29 animals/m2 of forest floor.
Community Ecology: Hairston (1981) experimentally reduced the densities of two large Plethodon species in plots in the southern Appalachians and found that the surface numbers of P. serratus were not altered significantly. This suggests that competition between P. serratus and large Plethodon species is minimal.
Adverse Environmental Impacts
Status in North Carolina
NHP State Rank: S4
Global Rank: G5
Environmental Threats: The conversion of hardwoods to intensively managed pine forests appears to be depleting many populations of this species in Georgia (Camp 1986). Old hardwood forests on moderate to steep relief provide optimal habitats for this species in Georgia.

Photo Gallery for Plethodon serratus - Southern Red-backed Salamander

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Recorded by: Owen McConnell
Graham Co.