Shovel-nosed Salamander, Shovelnose Salamander
© 2011 Todd Pierson (1 of 24)
Country distribution from AmphibiaWeb's database: United States
Desmognathus marmoratus (Moore, 1899)
Carlos D. Camp1
1. Historical versus Current Distribution. Shovel-nosed salamanders (Desmognathus marmoratus) are found from southwestern Virginia southwest through eastern Tennessee, western North Carolina, and extreme northwestern South Carolina and into northern Georgia at elevations from 300–1,680 m (Petranka, 1998). Drainage patterns, and consequentially rate of stream flow, rather than elevation, apparently limit distribution (Martof, 1962b). Populations are scattered, especially at the northeastern and southwestern extremes of the range. Shovel-nosed salamanders commonly were collected and sold as fish bait in Georgia during the mid-twentieth century (Martof, 1962b), and bait dealers have introduced shovel-nosed salamanders into areas outside their historical range (Martof, 1962b). A survey of bait shops in the Appalachian region of Georgia during 1997–'98 showed that this species currently is not important to the bait industry in that state (Jensen and Waters, 1999).
Martof (1962b) noted the absence of shovel-nosed salamanders in streams that have been heavily silted. He also noted the enigmatic absence of this species in apparently favorable habitats in Georgia stream systems (e.g., Hiwassee, Ocoee, and Nottely rivers) to the west of its distribution. A newly discovered, dark-ventered desmognathine that is similar in size to shovel-nosed salamanders occurs in streams of the Nottely River system (Camp et al., 2000, 2002). The recently found form is presumably a member of the marmoratus–quadramaculatus clade (sensu Titus and Larson, 1996) within the genus Desmognathus (Camp et al., 2002). Competitive exclusion between the two, while possible, seems unlikely because the newly discovered form is semi-aquatic, occupying habitats similar to black-bellied salamanders (D. quadramaculatus); shovel-nosed salamanders are nearly (see below) completely aquatic (Camp et al., 2002). Stream capture apparently has influenced the distributional history of shovel-nosed salamanders (Martof, 1962b; Voss et al., 1995).
2. Historical versus Current Abundance. Petranka (1998) noted that shovel-nosed salamanders generally are common in second- and third-order streams at elevations below 1,220 m. Shovel-nosed salamanders are nearly (see below) completely aquatic (Hairston, 1949; Martof, 1962b) and are most abundant in rapids and riffles where densities can be > 6 animals/m2 (Martof, 1962b). Populations have been shown to be vulnerable to low pHs and heavy metal contamination (Mathews and Morgan, 1982).
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. This species is not known to migrate. Martof (1962b) suggested that females may breed every other year. The bienniality of female oogenic cycles in other desmognathines has been questioned, however (Tilley, 1968, 1977; Tilley and Tinkle, 1968).
ii. Breeding habitat. Mating presumably occurs in habitat that is favored for other activities, i.e., riffle areas of streams (Martof, 1962b). Mating behavior has not been described.
i. Egg deposition sites. Females oviposit and attend their clutches in late spring and summer. Eggs are laid on the undersides of large rocks in fast-flowing streams (Pope, 1924). Eggs are attached singly or in tight clusters of 2–4 eggs. Martof (1962b) found that clutches are deposited in the main currents of streams in an average depth of 20 cm (range = 8–36 cm).
ii. Clutch size. Mean clutch size varies among populations. Clutch size, which varies positively with female body size, ranges from 20–65, and eggs average 4.1 mm in diameter (Martof, 1962b). Incubation times have been estimated to be 10–12 wk, so that eggs hatch from mid August to mid September; hatchlings measure about 11 mm SVL (Martof, 1962b).
i. Length of larval stage. In western North Carolina, Bruce (1985a) determined larval period to be 3 yr, whereas Martof (1962b) estimated a larval period of 10–20 mo in Georgia. One of Martof’s (1962b) larval samples, however, exhibited three distinct size classes, similar to Bruce’s (1985a) data. Both workers found maximum larval size to be similar (38 mm SVL), although Martof (1962b) found newly metamorphosed animals as small as 25 mm SVL.
ii. Larval requirements.
a. Food. Larvae feed on aquatic invertebrates. From an analysis of stomach contents, Martof and Scott (1957) reported that larvae fed on aquatic insects represented by five different orders (Plecoptera, Ephemeroptera, Trichoptera, Diptera, Coleoptera).
b. Cover. Larvae inhabit interstices of rock and gravel on the bottoms of streams (Bruce, 1985a). Small larvae can be under collected in samples and may be more secretive in inter-gravel spaces. Bruce (1985a) noted that larvae readily burrow into aquarium gravel when placed into artificial tanks.
iii. Larval polymorphisms. Larvae of this species are not known to exhibit distinct polymorphisms.
iv. Features of metamorphosis. In western North Carolina, larvae reach a maximum size of 37–38 mm SVL (Bruce, 1985a); at a Georgia site, larvae reach a maximum size of 30–36 mm (Martof, 1962b). In other populations, larvae are smaller, with average sizes at metamorphosis between 26 and 33 mm SVL (Petranka, 1998).
v. Post-metamorphic migrations. This species is not known to migrate.
vi. Neoteny. Occasionally, larvae with enlarged gonads have been found (Martof, 1962b). All individuals exhibit the neotenic retention of lateral line pores (sensu Hilton, 1947).
D. Juvenile Habitat. Following metamorphosis, juveniles remain in streams, where their habitat resembles that of adults (Martof, 1962b).
E. Adult Habitat. Shovel-nosed salamanders inhabit cool, well-oxygenated, second- and third-order streams or low gradient first-order streams (Pope and Hairston, 1947; Martof, 1962b). Adults inhabit shallow waters in areas with rocks, loose gravel, and moderate- to fast-flowing water (Petranka, 1998). There is a greater density of salamanders in rapids and riffles than in pools. This may have to do with a physiological need to constantly flush the water next to the skin for aeration purposes. Booth and Feder (1991) showed that, because of the differential diffusion of oxygen, a thin, hypoxic zone develops around the skins of plethodontids in quiet water. Captive shovel-nosed salamanders have been observed to climb into air and rest on the sides of plastic bags when left in cool, quiet water for 12–24 hr (C.D.C., personal observations). Both males and females are found under cover objects during the day and emerge to feed at night (Martof, 1962b). Southerland (1986f) presented evidence that they may be able to climb onto land during rainy weather. One of us (S.G.T.) observed an individual during the daytime on a branch about 10 cm above flowing water of Mill Creek, Blount County, Tennessee. Bishop (1943) stated that Leurognathus marmorata intermedia (sic) sometimes occurs on land, but he did not provide corroborative evidence.
F. Home Range Size. Unknown.
G. Territories. Preliminary observations of laboratory-based, staged encounters suggest that individuals may not be aggressive toward conspecifics (Jaeger and Forester, 1993).
H. Aestivation/Avoiding Dessication. Unlikely. Martof (1962b) found individuals that were active throughout most of the year (April–November).
I. Seasonal Migrations. Shovel-nosed salamanders are not known to migrate.
J. Torpor (Hibernation). Unknown. However, Martof and Scott (1957) reported collecting individuals with stomachs full of food in the early spring.
K. Interspecific Associations/Exclusions. Shovel-nosed salamanders often coexist with black-bellied salamanders (D. quadramaculatus). Individuals of the latter species are not fully aquatic and are often associated with the banks of streams where shovel-nosed salamanders are found (Martof, 1962b). In addition, black-bellied salamanders usually rest or forage with a large part of their body out of the water (Camp and Lee, 1996; Mills, 1996). Therefore, contact between the two species may not be frequent. Preliminary observations of laboratory-based, staged encounters suggest that shovel-nosed salamanders may not be aggressive toward black-bellied salamanders (Jaeger and Forester, 1993). Because of their unique habitat, shovel-nosed salamanders are more likely to compete with small fishes that have similar niche characteristics (e.g., sculpins [Cottus spp.]; Greenberg and Holtzman, 1987) than with other species of salamanders.
Shovel-nosed salamanders share habitats with larval members of the two-lined salamander (Eurycea bislineata) complex, and Martof and Scott (1957) reported a shovel-nosed salamander that had eaten a larval two-lined salamander. Female two-lined salamanders often nest in riffle areas of streams (Petranka, 1998; C.D.C., personal observations). Any interactions between adult two-lined and shovel-nosed salamanders may be seasonal and related to the timing of nesting by two-lined salamanders.
L. Age/Size at Reproductive Maturity. Adult males range 50–73 mm SVL, with males reaching sizes that average 6–13% larger than that attained by adult females (Martof, 1962b). The largest specimen (78 mm SVL) reported by Martof (1962b), however, was a female. Females mature at 55–59 mm SVL (Martof, 1962b). Maturation may occur at 4–5 yr (Tilley and Bernardo, 1993).
M. Longevity. Unknown. Other desmognathines are known to live for at least 13 yr (Castanet et al., 1996).
N. Feeding Behavior. Generally, adults feed on aquatic and stream-associated terrestrial invertebrates, especially insects (Martof, 1962b). Stomach contents showed prey items to include snails, crayfish, and insects such as ephemeropterans, trichopterans, dipterans, hymenopterans, and coleopterans (Martof and Scott, 1957). Martof and Scott (1957) found the remains of salamanders in 3 of nearly 200 stomachs examined. The two sets of remains that could be identified were a two-lined salamander larva and a conspecific larva.
Underwater observations indicate that shovel-nosed salamanders often lie under stones with their heads sticking out in an alert manner (Martof, 1962b). This suggests that at least some of these salamanders may use an ambush foraging strategy. Other individuals have been observed to leave cover objects and move along the stream bottom to forage, especially at night (Martof, 1962b). Observations of similar behaviors have been made of sculpins, small predaceous fishes that occupy the same riffle-type habitats as shovel-nosed salamanders (Greenberg and Holtzman, 1987).
O. Predators. Shovel-nosed salamanders live in streams with predaceous fish (e.g., Cottidae, Cyprinidae, and Salmonidae). Much of the habitat occupied by these salamanders is also prime habitat for trout (Salmonidae), and stock trout (Onchorhynchus mykiss and Salmo trutta) are often released in these streams by fish and wildlife agencies. Martof (1962b) reported a case of predation of a shovel-nosed salamander by a native brook trout (Salvelinus fontinalis). Water snakes (Nerodia sipedon), which readily feed on desmognathines (C.D.C., personal observations), may be common along streams containing shovel-nosed salamanders. In a confined laboratory situation, large stone fly (Acroneuria sp.) nymphs attacked small shovel-nosed salamander larvae (Mathews, 1982). Shovel-nosed salamanders occasionally are cannibalistic (Martof, 1962b).
P. Anti-Predator Mechanisms. Individuals tend to take shelter under rocks on stream bottoms and leave them to forage at night (Martof, 1962b). When disturbed by humans, adults move slowly away or swim away for a short distance (Martof, 1962b).
Q. Diseases. Unknown.
R. Parasites. Goater et al. (1987) reported four species of mature nematodes in a survey of 50 shovel-nosed salamanders from southwestern North Carolina. These four species were Capillaria inequalis, Thelandros magnavulvaris, Omeia papillocauda, and Falcaustra plethodontis. They demonstrated that this nearly completely aquatic species of salamander harbors a less diverse helminth fauna than semi-aquatic congeners. Goater (2000) found no leeches on 50 shovel-nosed salamanders surveyed. He did, however, find trypanosomes, flagellates that live in the bloodstream and presumably introduced by the leech Oligobdella biannulata, in 4 of 17 surveyed salamanders.
4. Conservation. Shovel-nosed salamanders depend heavily on flowing streams having rocky substrates with abundant interstices. They are vulnerable, therefore, to the degradation of these habitats. Shovel-nosed salamanders are largely absent from streams that have been heavily silted (Martof, 1962) and have been eliminated from many areas due to the impoundment of streams (Petranka, 1998). Because of the dependence of this species on aquatic insects, pollution or other degrading factors that affect insect populations may also affect populations of shovel-nosed salamanders through the loss of potential food resources. Shovel-nosed salamanders are vulnerable to pollution that results in high acidity and contamination of streams by heavy metals (Mathews and Morgan, 1982). Shovel-nosed salamanders were exploited as fish bait in some areas during the mid-twentieth century (Martof, 1962). However, a recent survey of bait shops in northern Georgia showed that this species is no longer important to the bait industry of that state (Jensen and Waters, 1999).
1Carlos D. Camp
2Stephen G. Tilley
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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