Amphibians of North Carolina

Scientific Name:	Common Name:		Family (Alpha):

NC Records
Plethodontidae Members:
Desmognathus monticola - Seal Salamander

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Taxonomy

Class: Amphibia

Order: Caudata

Family: Plethodontidae

Subfamily: Plethodontinae


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. Beamer and Lamb (2020) documented three clades within populations that are currently recognized as the Seal Salamander (D. monticola). These include a group in northern Georgia, southeastern Tennessee, and as a disjunct in southwestern Alabama (Clade A), a relatively homogeneous and widespread group that extends from western North Carolina throughout the northern portion of the range to Pennsylvania (Clade B), and a third group in east-central Alabama (Clade C). Pyron et al. (2023) conducted additional molecular and morphometric analyses using a variety of speciation and biogeographic models and concluded that only two species should be recognized. These are Clade B (D. monticola, sensu stricto) that occurs from northern Georgia throughout all of western North Carolina to Pennsylvania, and the remaining populations (D. cheaha sp. nov.) that are found from northwestern Georgia to southwestern Alabama. The two species are estimated to have been diverging for 1-2 million years. They meet in northern Georgia where there is a narrow hybrid zone with introgression of genes in both directions.
Species Comments:

Identification

Description: The Seal Salamander is a relatively large Desmognathus with a tail that is rounded on the anterior third and laterally-compressed and keeled on the posterior two-thirds. The dorsum often has reticulate, mottled, or wormy dark brown to blackish markings on a light brown or grayish background (Petranka 1998). In many populations the wormy markings and dark mottling are absent or greatly reduced. The venter is whitish in young animals and whitish to light gray in older individuals. The belly lacks any conspicuous mottling as seen in some Desmognathus species, and a single line of white spots often occurs along each side between the legs. The toe tips have cornified friction pads and are usually darker than the remainder of the toe. Adult males have enlarged premaxillary teeth, a mental gland on the chin, and papillose cloacal lips. The maximum adult size of males tends to slightly exceed that of the females. Adults vary from 7.5-15 cm TL and there are 14 costal grooves (Petranka 1998).

The hatchlings average about 11-12 mm SVL and the larvae have 4-5 pairs of light dorsal spots between the limbs. The toe tips of older larvae usually have black cornifications. Young juveniles have four or five pairs of chestnut-colored spots that become fused and invaded by darker pigment with age.

Online Photos: Google iNaturalist

Observation Methods: The adults can be observed at night foraging in and along the margins of streams.

AmphibiaWeb Account

Distribution in North Carolina

Distribution Comments: The Seal Salamander is primarily found in the Appalachian Mountains from southwestern Pennsylvania, western Maryland, West Virginia, eastern Kentucky, and western Virginia southward to northern Georgia. Populations in North Carolina are widespread in the Blue Ridge Mountains and Escarpment, and at a few scattered locales to the east (Beane et al. 2010).
County Map: Clicking on a county returns the records for the species in that county.


GBIF Global Distribution

Key Habitat Requirements

Habitat: This is a semi-terrestrial species that is most commonly found in or adjoining small to moderate-sized, rocky streams and their associated seepages. They tend to be restricted to streams with well aerated, cool water (Petranka 1998). Although populations range in elevation as high as 1555 m, they are most abundant at elevations < 1219-1372 m (Hairston 1949, Organ 1961a). In mesic forests at relatively high elevations, the juveniles and adults often reside in burrows in stream banks and avoids the stream proper where members of the D. quadramaculatus complex live (Hairston 1949, 1986, Organ 1961a). At low elevations, individuals are commonly found beneath rocks and other cover directly in the streambed and may not spatially segregated from members of the D. quadramaculatus complex. The juveniles and adults sometimes forage away from streams or stream banks, but in North
Carolina are rarely found more than 5 meters from a stream bank (Petranka and Smith, 2005).

See also Habitat Account for Montane Perennial Creeks and Small Streams

Life History and Autecology

Breeding and Courtship: The breeding season is poorly documented, but mating likely occurs both in the spring and from late-summer through early autumn (Petranka 1998). The adults engage in a stereotypic tail-straddle walk that is similar for all Desmognathus species (Organ 1961a, Brock and Verrell 1994). As summarized by Petranka (1998) a male will often 'butterfly' when approaching a female, which involves making circular strokes of the front limbs that resembles the butterfly stroke of swimmers. The male may also stroke the neck and head of the female with his forearms. The male eventually initiates a new phase of courtship that involves rubbing his head along the female's head. The male eventually slides his body under the female's chin and undulates his tail. Once the female's head is positioned on the dorsal surface of the base of the tail, the male may curve his body backwards towards the female's neck or dorsum and pull or snap with the teeth to scratch the female's skin. This action transfers mental gland secretions into the female's circulatory system and can also occur when a male is positioned alongside a female (Petranka 1998).

The pair eventually engages in a tail-straddle walk in which the male laterally undulates his tail and slides under the female's head until her chin rests on the dorsal base of the tail. The male moves forward in a straight line while undulating his tail laterally and the female follows as she straddles his tail. Eventually the male increases the intensity of tail undulating and deposits a spermatophore. He then leads the female forward and she picks up the sperm cap in her cloaca while laterally undulating her pelvic region. Courting males are often aggressive towards each other and will attack and bite potential competitors that could interfere with courtship.

Reproductive Mode: After mating, the females attach their eggs in decaying logs and leaf packs, or to the undersides of tree roots, stones and rocks. The oviposition sites are typically in running water or sites such as streambanks with dripping wet substrates (Organ 1961a, Petranka 1998, Pope 1924). Females typically attach their eggs singly to a support structure such as a rock to form a tight monolayer. They have also been observed to deposit them in loose groups that may be 2-3 egg layers thick. Each egg is attached by an elastic stalk so that the movements of the attending female or water current rocks the egg back and forth and facilitates aeration.

Eggs in early developmental stages have been found from mid-June to early August (Petranka 1998). Nesting records for North Carolina include two nests with 21 and 30 eggs in early embryonic stages in late July and early August (Pope 1924), and two clutches with ova that averaged 4.1 mm in diameter on 16 July. The latter clutches were buried in rock, gravel, and mud in the bed of a small stream (Bruce 1990). The number of eggs per nest varied from 16-39 and averaged 27 in southwestern Virginia populations that were studied by Organ (1961a). Eggs in these populations were in early developmental stages in June and close to hatching in early September. Hatchlings first appear in September, which suggests an incubation period of about 2 months.

The number of mature ova in specimens examined by Tilley (1968) from the southern Appalachians varied from 16-40, averaged 27, and was independent of female SVL, while the number of ova in two populations from western North Carolina averaged 24 and 29 (Bruce 1995, Bruce and Hairston 1990). SVL was positively correlated with number of ovarian eggs at one site, but not at the second.

Aquatic Life History: The larval period is relatively short compared to that of members of the D. quadramaculatus complex. Hatchlings first appear in late summer or early fall then overwinter. The larvae resume growing with the spring warm-up and transform during the early to mid-summer months when around 14–16 mm SVL (Petranka 1998). Organ (1961a) collected hatchlings in September and recently transformed larvae in June and July, which suggests a larval period of 10-11 months. Juterbock (1984) estimated a larval period to be 8-9 months in Kentucky populations, with transformation occurring in May and June. The larvae presumably prey on an array of small invertebrates such as midge larvae, but little data is available on their diet.

Terrestrial Life History: After metamorphosing the juveniles and adults reside in or near streams and seepages. Individuals live beneath cover objects, in old root channels, or in burrows in stream banks and emerge shortly after dark to forage. Invertebrates are the dietary mainstay, but they may also eat small salamanders (Brandon and Huheey 1971, Hairston 1986, Shealy 1975). At night individuals either sit with their bodies partially extended from their burrow entrances waiting for prey, or actively move about in search of prey. Adults in the southern Appalachians sometimes climb 1-2 m above ground on tree trunks on rainy nights (Petranka 1998).

The juveniles and adults are gape-limited predators that feed on both aquatic and terrestrial invertebrates, including stoneflies, caddisflies, true bugs, lepidopterans, beetles, flies, wasps, millipedes, and earthworms (Krzysik 1979, Petranka 1998). Hairston (1949) noted that individuals in North Carolina populations feed mostly on terrestrial insects. Individuals will often move temporarily out of streams and onto streambanks or the forest floor after heavy rains, and may even climb tree trunks for a meter or more to forage.

The juveniles grow slowly and require several years to reach sexual maturity. Bruce (1990) found the mean size of 1, 2, 3, and > 4-year olds in a western North Carolina population to be 16.7, 28.9, 40.4, and 55.3 mm SVL, respectively. Organ (1961a) estimated that males become sexually mature when 3.5-years old, while females become mature when 4.5-years old, and first reproduce the following year when 5-years old. Males and females in western North Carolina populations first reproduce when 4-5 and 5-6 years old, respectively, and when 46-48 and 52-53 mm SVL (Bruce 1989, 1990, 1995). Data for other populations indicate that males and females first become sexually mature when > 41 and > 47 mm SVL (Petranka 1998).

Organ (1961a) noted that age-specific survivorship is fairly constant in transformed males throughout life, but tends to increase slightly as females become sexually mature. The mean annual survival rate is about 50% during the early years of life for males and immature females. The annual rate of survival of brooding females is only 30%. These estimates assume that females breed biennielly. In contrast with Organ's findings, Tilley (1968) found that age-specific survivorship tends to decrease with age in western North Carolina populations. Annual survival of 50-60% is required to maintain stable numbers of females in a study population in North Carolina (Bruce 1995).

Seal Salamanders have small home ranges and rarely move long distances. Hardin et al. (1969) estimated the average home range to be 8.4 m2 compared to only 0.07-0.45 m2 for populations studied by Kleeberger (1984, 1985). The adults appear to be territorial and will readily defend cover sites and burrows from both male and female conspecific intruders (Keen and Sharp 1984). Individuals of different sizes often segregate, with adults preferring larger cover objects than juveniles. This may reflect both ontogenetic shifts in the size of cover objects preferred, as well as the active avoidance of larger individuals by smaller conspecifics (Colley et al. 1989).

These and other salamanders can reach high densities in fish-free sections of streams and play important ecological roles as top predators. Kleeberger (1984, 1985) estimated densities to be 0.72-1.4 individuals/ m2 in optimal habitats in a study stream in western North Carolina and provided experimental evidence that cover objects are limiting and are a potential source of competition. Data provided by Bruce (1995) suggest densities in the order of 2.5-3.5 animals/m2 in optimal stream habitats.

General Ecology

Community Ecology: Hairston (1986) experimentally lowered densities of D. ocoee and D. monticola on study plots in the Nantahala Mountains to determine if competition or predation is the major organizing force in a Desmognathus community comprised mostly of D. ocoee, D. monticola, and D. amphileucus. When D. ocoee was removed from plots, the abundance of D. monticola and D. amphileucus decreased relative to control plots. Removal of D. monticola results in an increase in D. ocoee. Desmognathus ocoee also shifted its distribution towards streams when larger congeners decreased in numbers. Hairston (1986) concluded that predation, rather than competition, is the major force that has driven the evolution of body size and habitat preference in the genus.

Adverse Environmental Impacts

Status in North Carolina

NHP State Rank: S5

Global Rank: G5

Photo Gallery for Desmognathus monticola - Seal Salamander		18 photos are shown.
	Recorded by: B. Bockhahn Macon Co.	Recorded by: B. Bockhahn, J. Thomson Macon Co.
	Recorded by: B. Bockhahn, J. Thomson Macon Co.	Recorded by: K. Williams Surry Co.
	Recorded by: M. Mabe, R. Spainhour, A. Shaffer, K. Messick, A. McDevitt Surry Co.	Recorded by: B. Bockhahn Macon Co.
	Recorded by: B. Bockhahn, J. Thomson Buncombe Co.	Recorded by: B. Bockhahn, J. Thomson Buncombe Co.
	Recorded by: K. Bischof Transylvania Co.	Recorded by: K. Bischof Transylvania Co.
	Recorded by: tom ward Buncombe Co.	Recorded by: K. Bischof Transylvania Co.
	Recorded by: tom ward Buncombe Co.	Recorded by: Jim Petranka Macon Co. Comment: A clutch of eggs on the underside of a rock.
	Recorded by: Steve Hall, Harry LeGrand, and Ed Schwartzman Cherokee Co.	Recorded by: Jim Petranka Buncombe Co.
	Recorded by: Owen McConnell Graham Co.	Recorded by: Owen McConnell Graham Co. Comment: A young juvenile.

Desmognathus monticola - Seal Salamander

Photo Gallery for Desmognathus monticola - Seal Salamander

18 photos are shown.