© 2010 Dr. Stephen G. Tilley (1 of 20)
Can you confirm these amateur observations of Desmognathus imitator?
Desmognathus imitator (Dunn, 1927)
Carlos D. Camp1
1. Historical versus Current Distribution. Imitator salamanders (Desmognathus imitator) are found in a restricted area of the Great Smoky, Plott Balsam, and Balsam mountains of eastern Tennessee and western North Carolina at elevations above 900 m (Tilley, 1985; Petranka, 1998). Their range extends from the Great Smoky Mountains to slightly east of Soco Gap on Balsam Mountain (Petranka, 1998; Tilley, 2000a). Populations inhabiting rock faces at Waterrock Knob are phenotypically distinct from populations elsewhere (Petranka, 1998; Tilley, 2000a). Tilley (2000a) noted, however, that recognition of this form as a distinct species would “obscure patterns of evolutionary diversification" indicated by allozyme data.
2. Historical versus Current Abundance. Unknown. Most populations are now protected, as the habitat of imitator salamanders lies almost entirely within the boundaries of the Great Smoky Mountains National Park and Blue Ridge Parkway.
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. Unlikely. Breeding probably occurs both in the autumn and in the spring, with ovipositing in late spring to early summer, similar to other small species of Desmognathus (Petranka, 1998). Verrell (1994a) observed the mating of individuals from Waterrock Knob from July–October in a laboratory environment.
ii. Breeding habitat. Mating presumably occurs in the same habitats where adults consistently are found, including seepage areas, wet rock faces, and forest-floor habitats (Tilley et al., 1978; Petranka, 1998).
i. Egg deposition sites. Koenings et al. (2000) found six egg clutches in saturated soil within a seepage in late June in western North Carolina. All clutches were attached to the undersides of respective rocks. One clutch was still attended by a brooding female. Five of the clutches were attached to the rock as a monolayer. The sixth clutch had eggs arranged in two layers. Two clutches were found under rocks in saturated gravel in a spring at Double Springs Gap in the Great Smoky Mountains (Swain County, North Carolina; S.G.T., personal observation).
ii. Clutch sizes. The clutches observed by Koenings et al. (2000) averaged 19 eggs/clutch (range = 13–24). Two presumed clutches of imitator salamander eggs reported by Petranka (1998) contained 23 and 30 eggs (Koenings et al., 2000).
i. Length of larval stage. Unknown. Presumed to be similar to that of Ocoee salamanders (D. ocoee; Bernardo, 2000), which is < 1 yr (Huheey and Brandon, 1973; Bruce, 1989).
ii. Larval requirements.
a. Food. Probably small, aquatic invertebrates.
b. Cover. Under rocks, leaf litter, and moss in headwater seepage areas, which may serve as nurseries for this species (Bernardo, 2000).
iii. Larval polymorphisms. Unknown.
iv. Features of metamorphosis. A series of newly metamorphosed juveniles reported by Bernardo (2000) averaged 12 mm SVL (range = 10–14).
v. Post-metamorphic migrations. Unknown. However, adults may be found under cover in the forest floor at some distance from seepages (Tilley et al., 1978).
vi. Neoteny. Unknown.
D. Juvenile Habitat. Juveniles may be abundant in headwater seeps (Bernardo, 2000).
E. Adult Habitat. Imitator salamanders are found along streamsides, on wet rock faces, and associated with the forest floor at high elevations in spruce-fir and northern hardwood forests (Tilley et al., 1978). They usually are found closer to streams than Ocoee salamanders, which they resemble and overlap in distribution. A unique population that inhabits Waterrock Knob occurs on wet rock faces above 1,650 m (Tilley, 2000a). Other rock face populations, phenotypically distinct from those on Waterrock Knob, occur along the Blue Ridge Parkway on Balsam Mountain. Koenings et al. (2000) suggested that the nesting habits of imitator salamanders may be more similar to those of semi-aquatic seal salamanders (D. monticola) than to the more closely related Ocoee salamanders.
F. Home Range Size. Unknown.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Unlikely. Active individuals have been found during summer (Tilley et al., 1978; Bernardo, 2000; Koenings et al., 2000).
I. Seasonal Migrations. Unknown.
J. Torpor (Hibernation). Unknown.
K. Interspecific Associations/Exclusions. Red-cheeked imitator salamanders are hypothesized Batesian mimics of Jordan’s salamanders (Plethodon jordani) in the Great Smoky Mountains (Petranka, 1998; Tilley, 2000a). They occur syntopically with Ocoee salamanders at higher elevations, but may exclude them from some lower elevation areas (Tilley et al., 1978; Bernardo, 2000). Imitator salamanders and Ocoee salamanders exhibit sexual isolation via a reduced willingness of individuals to mate with members of the other species (Verrell, 1989, 1990a; Verrell and Tilley, 1992). Imitator salamanders are replaced by Santeetlah dusky salamanders (D. santeetlah) on lower elevation rock faces in the Plott Balsam Mountains (Tilley, 2000a).
L. Age/Size at Reproductive Maturity. Adult males and females reach 50 and 57 mm SVL, respectively (Tilley, 1985). Bernardo (2000) reported two size classes of juveniles, one averaging 12 mm SVL and a second averaging 18 mm SVL. He noted that a juvenile growth rate of 6 mm/yr is similar to that seen in juvenile Ocoee salamanders (Tilley, 1980; Bernardo, 1994).
M. Longevity. Unknown. An individual of the similar Ocoee salamander has been aged at 10 yr (Castanet et al., 1996).
N. Feeding Behavior. Imitator salamanders take cover during the day and come out at night (Tilley et al., 1978), presumably to forage. Foods are probably similar to those of Ocoee salamanders, i.e., small invertebrates (Huheey and Brandon, 1973).
O. Predators. Unknown, but probably include ring-necked snakes (Diadophis punctatus), northern watersnakes (Nerodia sipedon), common garter snakes (Thamnophis sirtalis), larger salamanders including spring salamanders (e.g., Gyrinophilus porphyriticus), birds, and mammals. For the Batesian system to have evolved, predators would include those that find red-cheeked Jordan’s salamanders to be noxious as prey and also have the ability to detect chromatic cheek patches.
P. Anti-Predator Mechanisms. Immobility followed by flight (Dodd, 1990a). The chromatic cheek patches have been hypothesized to represent expressions of Batesian mimicry (Petranka, 1998; Tilley, 2000a).
Q. Diseases. Unknown.
R. Parasites. Unknown. Similar Ocoee salamanders harbor a fauna of helminths including nematodes, flukes, and tapeworms (Goater et al., 1987).
4. Conservation. Most of the geographic range of the imitator salamander falls within the boundaries of the Great Smoky Mountains National Park. Therefore, populations of this species are largely protected from such threats as mining and the harvesting of timber. Petranka (1998) suggested that the greatest long-term threat to this species may result from acid precipitation that may fall on high elevation sites in the Great Smoky Mountains and other areas of the southern Appalachians.
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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