Amphibians of North Carolina
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Desmognathus aureatus (Martof, 1956) - Southern Shovel-nosed Salamander


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Taxonomy
Class: Amphibia Order: Caudata Family: Plethodontidae Subfamily: Plethodontinae Author: (Martof, 1956)
Taxonomic Comments: Members of the genus Desmognathus are commonly known as dusky salamanders because of their overall dark brown or dusky ground color. Like many plethodontid salamanders, they have proven to be a taxonomically challenging group that contains several species complexes. Kozak et al. (2005) documented 35 major lineages in the eastern US, even though only 22 species were formally recognized by taxonomists in 2021. This suggests that there are numerous cryptic species that remain to be described. A more recent comprehensive molecular survey of populations in the eastern US by Beamer and Lamb (2020) indicate that at least 45 major lineages or clades are present.

Herpetologists have traditionally recognized the Shovel-nosed Salamander (D. marmaratus) as a species that closely resembles the Black-bellied Salamander (D. quadramaculatus) in being a relatively large Desmognathus with a stocky build, keeled and laterally compressed tail, cornified toe-tips and two rows of light spots that are usually present along each side of the body. If differs from the Black-bellied Salamander in having internal nares that form slits rather than round pores, in the coloration and patterning on the venter of adults, and in the profile of the head. Recent molecular studies by Beamer and Lamb (2020), as well as several previous studies, have shown that these two species are not monophyletic. Instead, populations of both species are interspersed within a strongly supported clade that contains all populations of D. quadramaculatus, D. marmoratus, and a third species, D. folkertsi. This major clade contains two subclades, including one that includes all D. quadramaculatus populations sampled south of the Pigeon River, as well as all D. marmoratus populations sampled in the Apalachicola and Savannah River drainages. The second subclade includes all populations of D. quadramaculatus sampled from east of the Tuckasegee River drainage basin (with one exception) as well as all populations of D. marmoratus sampled outside the Apalachicola and Savannah River drainages. In some cases populations of D. quadramaculatus are more similar genetically to D. marmoratus than to other D. quadramaculatus populations. Collectively, the research by Beamer and Lamb (2020) and others indicates the presence of a species complex that involves all three currently recognized species. After conducting additional molecular and morphometric studies, Pyron and Beamer (2022) recognized five species within the Black-bellied Salamander complex. These include a previously recognized species D. folkertsi, and four new species (D. amphileucus, D. gvnigeusgwotli, D. kanawha and D. mavrokoilius) that replace what was traditionally known as D. quadramaculatus and certain populations of D. marmoratus.

From a taxonomic standpoint, Jones et al. (2006) conducted additional mitochondrial studies that built upon the work of Kozak et al. (2005) and others, and concluded that there were three groups of shovel-nosed salamanders that might merit species recognition. However, they did not formally recognize these due to certain unresolved phylogenetic issues. In a French work, Dubois and Raffaëlli (2012) did elect to formally recognized three species as D. aureatus, D. melanius, and D. marmoratus) based on Jones et al.'s (2006) and others work, but their taxonomic changes were not widely adopted by North American herpetologists. In the most recent work, Pyron and Beamer (2023) provide a comprehensive review of the literature, correct a nomenclatural error by Dubois and Raffaëlli (2012), and provide a systematic revision of three species of shovel-nosed salamanders that are currently recognized. All three occur in North Carolina and include, 1) D. aureatus (Martof, 1956) that occurs in northeastern Georgia, northwestern South Carolina, and small portions of the nearby border regions of North Carolina, 2) D. intermedius (Pope, 1928) that occurs in the Blue Ridge of western North Carolina and eastern Tennessee, and appears to be restricted to the Tennessee drainages of major rivers in the central and southern Blue Ridge of North Carolina, and 3) D. marmoratus (Moore, 1899) from northeast of the Pigeon River in North Carolina to northeastern Tennessee and southwestern Virginia. These three species do not represent a natural group as previously thought, but instead exhibit convergent phenotypes across multiple species, potentially driven by ancient episodes of adaptive introgression between ancestral lineages. Although there are some morphometric differences between species that are best determined using museum specimens, the three species are best identified by using their geographic ranges (see range map above) and the site where a specimen was observed.
Species Comments:
Identification
Description: This is our most distinctive and smallest shovel-nosed salamander, with a snout-vent-length of 34–73 mm (Pyron and Beamer, 2023). The adults lack vomerine teeth and have an overall olive-green to light brownish-olive dorsal color that is overlain with five to six large light dorsal spots on each side between the limbs (Martof, 1956a). The spots are separated by irregularly shaped blackish-brown patches, and usually have bright yellow centers. They continue onto the tail where they are somewhat brighter and tend to converge. Dark reticulations are present on the limbs and on the dorsal surface of the head. The snout is usually darker than the body, the soles of the feet are dark, and the tips of the toes are black. The two ventrolateral rows of light spots that are seen on most of our large stream-dwelling Desmognathus species are inconspicuous or absent. The ventrolateral surfaces of the tail are suffused with yellowish pigment, and the venter is primarily a deep neutral gray with a large whitish central area between the forelimbs that extends about two-thirds the distance to the vent. Martof (1962) noted that populations in northern Georgia sometimes have an unusual color morph that is whitish yellow to bright canary yellow. Some have a piebald pattern of dark pigment scattered over the body, but mostly on the distal part of the tail and on the tip of the snout. The males of this species are larger on average, have enlarged maxillary teeth, papillate cloacae (smooth in females), and an inconspicuous mental gland (Martof 1962, Petranka 1998).
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AmphibiaWeb Account
Distribution in North Carolina
Distribution Comments: This species is a southern Appalachian endemic that is restricted to the Blue Ridge Mountains of northeastern Georgia, northwestern South Carolina, and small portions of the nearby border regions of North Carolina. It can be found in headwater streams of the Chattahoochee, Chattooga, and Tallulah River drainages (Pyron and Beamer, 2023).
County Map: Clicking on a county returns the records for the species in that county.
GBIF Global Distribution
Key Habitat Requirements
Habitat: The Southern Shovel-nosed Salamander is an almost entirely aquatic species that prefers cool, well oxygenated streams at elevations of approximately 400–1100 m (1312-3,610'; Pyron and Beamer, 2023). It is almost always found in water, and is generally more common in second and third-order streams. The adults reach their highest densities in small to medium-sized streams with broken rocks and loose gravel, but local populations can also be found in headwater streams with gentle gradients (Martof 1962, Petranka 1998). Shallow riffle areas in streams that have angular rocks, loose gravel, and moderate to fast flowing water provide ideal microhabitats for the juveniles and adults.
Biotic Relationships: Martof (1962) noted that trout and other fishes are major predators of the larvae, subadults, and adults. Several species of large salamanders also eat the larvae and older individuals, including cannibalistic conspecifics, D. amphileucus, Gyrinophilus porphyriticus and Cryptobranchus alleganiensis,. Other known predators include water snakes (Nerodia sipedon; Regina septemvittata), raccoons, crayfishes, dytiscid beetles, various water bugs, and other aquatic insects.

Martof (1962) made an interesting observation pertaining to food chains at the Coleman River where he captured a Common Watersnake (Nerodia sipedon) that was in the process of swallowing a 215 mm Brook Trout. In the pharynx of the dying trout was a dead D. aureatus which measured 118 mm in total length. In its stomach was another D. aureatus, which in turn had consumed two mayfly nymphs, two caddisfly larvae, one stone fly nymph, one black fly larva, and one small parasitic round worm.
Life History and Autecology
Reproductive Mode: Martof (1962) dissected a large sample of females (N = 158) from Jarrard's Creek in North Georgia and found that females reach maturity when 55-59 mm SVL. The number of mature ova in specimens from several populations in northern Georgia was positively correlated with female SVL, with reported average clutch sizes of 42.5 eggs (range 31-65) from Jarrard's Creek (N = 21), 39.6 eggs (30-48) from the Coleman River (N = 7), and 39.5 eggs (34-45) from Reed Creek (N = 8).

Females begin laying their eggs as water temperatures rise in late spring or early summer and remain with their clutches through hatching (Martof 1962, Petranka 1998). Martof (1962) noted that the females typically deposit their eggs to the undersides of relatively large stones in the main current of a stream, and usually in situations where the surface water is rippled. The depth of water over the eggs varied from 8-36 cm, and the eggs were attached close together either singly or in groups of 2-4 to the rocks. The ova averaged 4.1 mm in diameter and were surrounded by a transparent capsule which is attached by a peduncle. Each peduncle was either directly attached to the stone or to another peduncle to produce groups of 2-4 eggs. Eight clutches from Reed Creek averaged 35.4 (27-43) eggs, and 21 from Jarrard's Creek averaged 43.7 eggs (32-54). These averages were very similar to those obtained for mature ova in dissected females from the same sites. The similarity in numbers indicate that almost all eggs are fertilized in nature and that embryonic survival to hatching is very high. Martof (1962) estimated that the embryonic period last around 2.5-3.0 months, with hatching occurring from mid-August to mid-September. The hatchlings averaged around 11 mm SVL and were blacker, slimmer, and had a more spatulate tail tip when compared to the co-occurring Nantahala Black-bellied Salamander (D. amphileucus). In addition, D. aureatus has light flecks that are scattered along the entire side of the body that are not present on D. amphileucus.
Aquatic Life History: The hatchlings are weak swimmers and often wash downstream into pools with low current (Martof 1962). The larvae feed mostly on insects and are more active outside of cover at night. Larvae that were metamorphosing in three north Georgia populations varied from 12-33 mm SVL, with the smallest subadults ranging from 28-34 mm SVL. The average size at metamorphosis ranged from 30-33 mm SVL. At one of the more intensively studied sites, the metamorphs averaged 30-36 mm SVL across months and were present from May through October. Average size at metamorphosis declined seasonally in this population. Martof (1962) estimated that the larval period typically lasts from 10-20 months. Most larvae from clutches that are laid early in the year apparently metamorphose the following year, while those hatching late in the season requiring a second year of growth. The males become sexually mature when 43-50 mm SVL versus 55-59 mm SVL for females. Bruce (1985a) estimated the larval period to be about 3 years in a population in western North Carolina. The larvae grew 7-10 mm SVL per year and reached a maximum size of 37-38 mm SVL.

Desmognathus aureatus is one of the most aquatic of our Desmognathus species and rarely leaves the water. The juveniles remain in the stream proper where they occupy habitats similar to those of the adults. Both are frequently found beneath submerged stones in fast current and often rest during the day with their heads protruding from under stones. They often emerge after dark and move about, presumably in search of food and mates. Specimens are most abundant in shallow rapids and riffles where they sometimes exceed a density of 6 salamanders/m2 (Martof 1962).

The diet of the subadults and adults is primarily composed on insects. Martof and Scott (1957) found that mayflies, caddisflies, and true flies were the most important prey. Other prey included stoneflies, beetles, hymenopterans, crayfishes, mites, snails, and salamanders, including the Blue Ridge Two-lined Salamander (Eurycea bislineata) and conspecifics. The adults continue feeding through late autumn after water temperatures drop. Comparison of stomach contents with stream samples of invertebrates suggest that this species is a gape-limited, generalist, opportunistic feeder that will attempt to capture most prey it encounters. The young juveniles feed on aquatic insects like the adults, and incorporate larger prey into the diet as they grow and their gape widens. However, stoneflies with hard stone cases seem to be less preferred than soft-bodied species such as mayflies (Martof and Scott, 1957; Petranka 1998).
General Ecology
Adverse Environmental Impacts
Effects of Introduced Species/Induced Increases of Native Species: Rainbow and other non-native trout that are release by fish and game departments undoubtedly take their toll on this and other stream-dwelling salamanders.
Interactions with Humans: Martof (1962) noted that this and other large salamanders are often harvested and sold as live bait. They have been release outside of their range by anglers in Georgia.
Status in North Carolina
NHP State Rank: [S1S2]
Global Rank: GNR
Status in North Carolina: [SR]
Environmental Threats: This species has environmental requirements similar to those of trout and does best in high-quality streams that are cool, well-oxygenated and minimally silted. Timbering and development are significant threats, particularly if they results in increased sediment loads in streams. Martof (1962) noted that this species is rarely found in streams or stream sections with rounded rocks that are embedded in sediments.
Status Comments: This species is a narrow southern Appalachian endemic that is restricted to the Blue Ridge Mountains of northeastern Georgia, northwestern South Carolina, and small portions of the nearby border regions of North Carolina. Although the geographic range of this species is very limited, populations can reach high densities in high-quality streams with protected watersheds. Populations in North Carolina are in relatively protected watersheds where they prefer cool, well-oxygenated streams. They are potentially vulnerable to future climate change that results in significant stream warming.
Stewardship: This and other stream-breeding salamanders in the Blue Ridge prefer high-quality streams with minimal siltation and wide buffers of mature or old-growth hardwood forests.

Photo Gallery for Desmognathus aureatus - Southern Shovel-nosed Salamander

1 photo is shown.

Recorded by: Jim Petranka
None Co.
Comment: Range map for shovel-nosed salamanders based on genetically identified specimens (courtesy of Alex Pyron).