Northern Dusky Salamander
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Country distribution from AmphibiaWeb's database: Canada, United States
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Desmognathus fuscus (Rafinesque, 1820)
D. Bruce Means1
1. Historical versus Current Distribution. The geographic distribution of northern dusky salamanders (Desmognathus fuscus) extends in the United States southwest from Maine, through New England, New York, and Pennsylvania to Virginia, then west to southern and eastern Ohio, southeastern Indiana, eastern Kentucky, eastern Tennessee, and western North Carolina (Petranka, 1998). Northern dusky salamanders also occur in Canada, and are found in Niagara Gorge in Ontario, in southeastern Québec, and in southern New Brunswick. The southern geographic limits of northern dusky salamanders are a poorly delineated contact zone between northern and spotted dusky salamanders (D. conanti) that extends southeast from the Cumberland River in western Kentucky to western South Carolina (see Karlin and Guttman, 1986; Petranka, 1998). Spotted dusky salamanders range from the contact zone to the southwest of the range of northern dusky salamanders, extending from extreme southern Illinois, western Kentucky, and western Tennessee into northern Georgia, Alabama, and Mississippi (Rossman, 1958; E.E. Brown, 1992; Petranka, 1998; Means, this volume). No reductions have been noted in the geographical distribution of northern dusky salamanders.
2. Historical versus Current Abundance. In eastern Kentucky and Tennessee, northern dusky salamander larvae are absent from many streams that drain coal strip mines (Gore, 1983). Throughout their New England and midwestern ranges, urbanization has extirpated many populations, but the species is wide ranging and ubiquitous in small stream valleys. There have been no studies documenting declines.
3. Life History Features.
A. Breeding. Reproduction is semi-aquatic.
i. Breeding migrations. Northern dusky salamanders commonly live within a few feet of streams or in springs and are not known to undertake extensive migrations (Bishop, 1941b). Adults mate during the fall and spring in Virginia (Organ, 1961a) and New York (Bishop, 1941b).
ii. Breeding habitat. Same as adult habitat.
i. Egg deposition sites. Eggs are attached to the undersides of rocks, logs, or other substrates in or near water (see Petranka, 1998).
Maryland salamanders lay eggs from June to early August (Danstedt, 1975) and New York salamanders from early June to late August (Wilder, 1913). In Ohio, females oviposit in the last two weeks in July and the embryos hatch from early September to mid October (Wood and Fitzmaurice, 1948; Dennis, 1962; Orr and Maple, 1978; Juterbock, 1986). Populations in eastern Kentucky and southeastern Ohio oviposit during July, and the eggs incubate for 46–61 d with a median incubation period of 47 d (Juterbock, 1986). In eastern Tennessee, females oviposit from the third week in June to the end of August, and embryos hatch from late August to mid October (Hom, 1987). In other parts of their range, eggs have been found from 28 June–5 October in Indiana (Minton, 1972, 2001); early June to early August in Maryland (Danstedt, 1975, 1979); 11 June–24 September in Massachusetts (Wilder, 1913); July–September in southwestern Pennsylvania (Krzysik, 1980a,b); and late June to mid August in Viriginia (Organ, 1961a). Females lay eggs every year in Maryland (Danstedt, 1975) and North Carolina (Spight, 1967c), but may be biennial in higher altitudes in southwestern Virginia (Organ, 1961a).
ii. Clutch size. There is variation in egg numbers, ranging from 13–34 with means ranging from 21–33 (see Petranka, 1998).
C. Larvae/Metamorphosis. Hatchlings were discovered between 17 June–1 September in Massachusetts (Wilder, 1913); in July and August in Maryland (Danstedt, 1975) and Pennsylvania (Krzysik, 1980a); in August and September in New York (Bishop, 1941b); and in mid September in Ohio (Dennis, 1962). The number of eggs/nest was 5–33 in nine nests in Massachusetts (Wilder, 1913); 22–34 in 44 nests in Pennsylvania (Pawling, 1939); and an average of 26 eggs in seven nests in Ohio (Wood and Fitzmaurice, 1948). Enlarged ovarian ova counts averaged 27 in 18 females from western North Carolina (Spight, 1967c); 21 in 17 Pennsylvania females (Hall, 1977); and 24–33 ova in females from six populations from Maryland (Danstedt, 1975). Larvae transform in late spring and early summer when 9–12 mo old in Maryland (Danstedt, 1975); in July–October when 11–14 mo old in Virginia (Organ, 1961a); and between 11 May–17 June when 8–10 mo old in Massachusetts (Wilder, 1913).
D. Juvenile Habitat. Same as for adults.
E. Adult Habitat. In New York, northern dusky salamanders are found along the margins of small wooded streams, on seepage hillsides, in shallow weed-choked streams with sandy bottoms, and in low boggy places under stones, logs, bark, and other debris on the ground (Bishop, 1941b). In Pennsylvania, they are found along wet streambanks with substrates of medium or coarse gravel and small rocks, and under logs about 15–90 cm from open water (Krzysik, 1979). In Ohio, they frequent the margins of streams, springs, leaf-littered trickles, spring banks with constantly moist soil, and the beds of ephemeral streams; preferred hiding places are under flat rocks and debris that are partially submerged in streams (Karlin and Pfingsten, 1989). Indiana northern dusky salamanders are largely restricted to hillside springs and small, rocky brooks in limestone country, but are sometimes found in river bottomlands in spring seepage areas and are often common in the mouths of caves, but not within caves (Minton, 1972, 2001). Brimley (1944) stated that in North Carolina they are salamanders of small woodland brooks, found in both streams and under rocks, logs, rubbish or other shelter close by, but never in strictly terrestrial surroundings.
F. Home Range Size. Barbour et al. (1969) reported an average home range of 48.4 m2 (25.2–114.5 m2) in 14 northern dusky salamanders found along a creek in east-central Kentucky with a sandstone bed. In strong contrast, along a small limestone stream in Ohio, Ashton (1975) calculated an average home range for 14 northern dusky salamanders of 1.4 m2 (0.1–3.6 m2). Mean activity radii were calculated for 21 Pennsylvania northern dusky salamanders from which home range can be determined (Barthalmus and Bellis, 1972). Population densities ranging between 0.43 and 1.42/m2 and biomass estimates were reported for salamanders in New Hampshire by Burton and Likens (1975b). Densities were calculated for populations at 0.8 m2 in Pennsylvania (Hall, 1977), and between 0.4 and 1.4 animals/m2 in a North Carolina stream bed (Spight, 1967c).
G. Territories. Aggressive behavior has been documented in northern dusky salamanders (Organ, 1961a), but this author speculated that aggressive behavior served as a method of sex recognition. Because of the aggressive behavior among males and high site tenacity of the species (Barthalmus and Bellis, 1969, 1972; Barthalmus and Savidge, 1974; Hom, 1987; Juterbock, 1987), territorial behavior is probably well developed, but no studies have specifically targeted this facet of its biology.
H. Aestivation/Avoiding Dessication. Aestivation is unknown, and probably does not occur. Animals likely avoid dessicating condition by seeking shelter under cover objects or in burrows.
I. Seasonal Migrations. In Ohio between 23 November–21 December, Ashton (1975) reported that salamanders moved into subterranean microhabitats that were warmer by several degrees centigrade upstream from their normal summer home.
J. Torpor (Hibernation). Ashton (1975), following the activity of five salamanders during winter in Ohio, discovered that all were active and burrowed quickly to escape through gravel and broken limestone of their winter streambed retreats when disturbed. The winter retreats were 30–50 cm below the soil surface, which was frozen to a depth of 14 cm. He concluded that at no time were northern dusky salamanders in an inactive state.
K. Interspecific Associations/Exclusions. Northern dusky salamanders have been reported in association (= locally sympatric or syntopic) with seal salamanders (Desmognathus monticola; Organ, 1961a; Krzysik, 1979; Southerland, 1986e), Allegheny Mountain dusky salamanders (D. ochrophaeus; Noble and Evans, 1932; Organ, 1961a; Stewart and Bellis, 1970; Hall, 1977; Orr and Maple, 1978; Krzysik, 1979; Karlin and Pfingsten, 1989; Holumuzki, 1980; Southerland, 1986e; Sharbel and Bonin, 1992; Sharbel et al., 1995), black-bellied salamanders (D. quadramaculatus; Organ, 1961a; Southerland, 1986e), pygmy salamanders (D. wrighti; Organ, 1961a), northern two-lined salamanders (Eurycea bislineata; Spight, 1967c; Stewart and Bellis, 1970; Holumuzki, 1980; Karlin and Pfingsten, 1989), long-tailed salamanders (E. longicauda; Karlin and Pfingsten, 1989), red salamanders (Pseudotriton ruber; Stewart and Bellis, 1970; Karlin and Pfingsten, 1989), mud salamanders (P. montanus; Spight, 1967c; Karlin and Pfingsten, 1989), spring salamanders (Gyrinophilus porphyriticus; Stewart and Bellis, 1970; Krzysik, 1979; Karlin and Pfingsten, 1989), southern ravine salamanders (Plethodon richmondi; Karlin and Pfingsten, 1989; Stewart and Bellis, 1970), northern slimy salamanders (P. glutinosus; Spight, 1967c; Karlin and Pfingsten, 1989), eastern red-backed salamanders (P. cinereus; Karlin and Pfingsten, 1989; Stewart and Bellis, 1970), and marbled salamanders (Ambystoma opacum; Spight, 1967c). Over their extensive geographical distribution, northern dusky salamanders are syntopic with more salamanders than listed above, but such associations rarely have been reported in the literature. Davic (1983) concluded that adult northern dusky salamander females were smaller because of syntopy with seal salamanders in Pennsylvania.
L. Age/Size at Reproductive Maturity. In New York, sexual maturity is reached when salamanders are 24–26 mo old; mating and egg laying follows 1–2 mo later (Bishop, 1941b). In Pennsylvania, age at maturity for males is 3 yr (Hall, 1977). In the Unicoi Mountains of Tennessee, males mature at approximately 2 yr and about 35 mm SVL; but females mature at 3 yr and about 40 mm SVL (Jones, 1986). In Maryland, males mature at 2 yr, females at 3 (Danstedt, 1975). At high elevation sites in Virginia, males become sexually mature at 3.5 yr and females 1 yr later, first ovipositing when 5 yr old (Organ, 1961a). Females in a Tennessee population reproduced on an annual cycle (Hom, 1987). Juterbock (1978) discussed maturity characteristics in northern dusky salamanders from Ohio and Kentucky.
M. Longevity. Snider and Bowler (1992) reported that a wild-caught adult of unknown sex lived 4 yr, 4 mo, and 11 d.
N. Feeding Behavior. Larvae in two studies were found to feed on copepods, chironomid midge larvae, plecopteran nymphs, collembolans, mites, and fingernail clams (Wilder, 1913; Burton, 1976). In the stomachs of 18 adults, Wilder (1913) found the remains of caddisflies, larval and adult dipterans, ants, spiders, beetles, sowbugs, caterpillars, earthworms, amphipods, mites, and molted skins and larvae of northern dusky salamanders. Food items identified from 53 stomachs of northern dusky salamanders from eastern Kentucky were amphipods, chilopods, orthopterans, ephemeridans, odonates, hemipterans, lepidopterans, coleopterans, hymenopterans, dipterans, spiders, and one gastropod (Barbour and Lancaster, 1946). From 83 stomachs from the White Mountains in New Hampshire, Burton (1976) reported many of the same groups plus mites, collembolans, plecopterans, thysanopterans, homopterans, trichopterans, and sphaeriid clams. In stomachs of Indiana northern dusky salamanders, Minton (1972, 2001) found beetles, lepidopteran larvae, ants, dipteran larvae, an ichneumonid wasp, and a stonefly nymph. Montague and Poinski (1976) and Wood et al. (1955) reported on brooding females that had ingested oligochaete annelids. Holumuzki (1980) reported the dietary overlap and synchronous foraging of northern dusky salamanders with two other plethodontids and showed that salamander surface activity was highly correlated with that of potential invertebrate prey. Krzysik (1979) reported niche overlap, niche width, and utilization spectra of prey volumes among Pennsylvania northern dusky salamanders and sympatric Allegheny Mountain Salamanders, seal salamanders, and spring salamanders, but did not list the prey species eaten. Krzysik (1980b) compared gut contents among brooding and non-brooding females, finding significantly more food in the latter, suggesting that brooding females do not actively forage.
O. Predators. Uhler et al. (1939) found that northern dusky salamanders were eaten by northern watersnakes (Nerodia sipedon) and common garter snakes (Thamnophis sirtalis). Black-bellied salamanders (D. quadramaculatus) were reported as predators by Noble and Evans (1932). Raccoons, skunks, opossums, and other small mammals, snakes, and birds probably eat northern dusky salamanders (Karlin and Pfingsten, 1989). Brooding females will cannibalize their own eggs and those of others (Bishop, 1941b; Baldauf, 1947; Wood and Clarke, 1955; Jones, 1986). Cannibalism by adults on larvae was reported by Wilder (1913) and Hamilton (1943).
P. Anti-Predator Mechanisms. Brooding females are hypothesized to keep egg predators away from incubating clutches (Dennis, 1962). Dusky salamanders often bite their predators (garter snakes) and autotomize their tails and flee (Whiteman and Wissinger, 1991).
Q. Diseases. No diseases have been reported.
R. Parasites. Rankin (1937) conducted an exhaustive study of the parasites of northern dusky salamanders in North Carolina, finding the following major groups in both larvae and adults: protozoans, trematodes, cestodes, nematodes, and acanthocephalans. Possible parasitism by roundworms was reported in New Hampshire northern dusky salamanders by Burton (1976).
4. Conservation. Monetary values of $0.25/specimen were assessed for northern dusky salamanders for the purpose of establishing a system to quantify the loss of native amphibians by the activities of man and to provide guidelines for financial penalties in attempts to mitigate or repair damage should population losses occur (Society for the Study of Amphibians and Reptiles Monetary Value of Amphibians Subcommittee, 1989). The absence of larvae of northern dusky salamanders from streams draining coal strip mines in eastern Kentucky and Tennessee appear to be caused by siltation and high metal concentrations (Gore, 1983). Although studies are lacking, there is little doubt that many northern dusky salamander populations have been impacted severely or extirpated in the heavily urbanized and developed areas of its range, which coincide with the most densely human populated region of the United States. Another problem has been the difficulty recognizing the southern limits of the northern dusky salamanders' range, which has been shown to overlap or abut the ranges of several cryptic species, with which it has been confused (e.g., spotted dusky salamanders, Santeetlah dusky salamanders [D. santeetlah], Allegheny Mountain salamanders, Black Mountain salamanders [D. welteri], and even southern dusky salamanders [D. auriculatus]). More studies of the evolutionary relationships of northern dusky alamanders and their relatives are sorely needed to clearly map out their geographic ranges so that studies of their population health and assessment of their conservation status can be made.
1D. Bruce Means
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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