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Desmognathus fuscusDusky Salamander(Also: Northern Dusky Salamander)

By Hannah Edwards

Geographic Range

Northern dusky salamanders occur from southern New Brunswick and Quebec, along the East Coast to North Carolina, and west to Ohio, southern Indiana, Kentucky, and Tennessee. Over most of their range, dusky salamanders are common in appropriate habitat. Their distribution in the southern Appalachian Mountains is sporadic. Desmognathus fuscus recently included three subspecies, which continued the range to the Gulf Coast. Most authorities now consider these to be separate species. See "Other Comments" below for further information. A breeding population of Desmognathus fuscus has been found at one site in eastern Michigan; whether this population is introduced or a natural relict has not yet been determined. (Bartlett and Bartlett, 2006; Bonnett, 2002; Conant and Collins, 1998; Harding, 1997; Petranka, 1998)

Habitat

Northern dusky salamanders prefer wooded or partially wooded moist habitats with running or trickling sources of water. Most often, they are found under flat rocks or logs near rocky or hillside streams or seeps, or in the moist, misty habitat near waterfalls. They may go into the water to find cover under rocks or substrate if disturbed. If the stream substrate does not freeze, they can remain active year-round. In extremely cold conditions, they will burrow under gravel until they are below the frostline. Dusky salamanders can survive at a variety of altitudes, ranging from sea level to high in the Appalachian Mountains. In the Great Smoky Mountains they are uncommon over 1200 m in elevation. (Bartlett and Bartlett, 2006; Conant and Collins, 1998; Harding, 1997; Hulse, et al., 2001; Petranka, 1998)

  • Aquatic Biomes
  • rivers and streams
  • Range elevation
    0 to 1200 m
    0.00 to 3937.01 ft

Physical Description

Desmognathus fuscus is a small but robust salamander with 14 costal grooves, and hind limbs that are larger than the front limbs. They have a keeled (knife-like) tail that is less than half the body length. The upper body varies from brown or reddish brown to gray or olive, with slightly darker markings on the top and sides. The base of the tail is typically olive, yellow, or bright chestnut (a bit lighter than the body). The belly is whitish with some dark speckles. Adults are 6.4 to 14.2 cm (2.5-5.6 in) in length. Males are typically longer than females. The average length for a male D. fuscus is 9.4 cm, and the average length for a female is 8.6 cm. Desmognathus fuscus is in the family Plethodontidae, and thus is lungless. They “breathe” via oxygen absorption through the skin and membranous tissue in the mouth and throat. Also, members of this family have a naso-labial groove, which may aid in smelling, which is important when finding prey and identifying potential mates. (Bartlett and Bartlett, 2006; Bishop, 1941; Conant and Collins, 1998; Harding, 1997; Hulse, et al., 2001; Petranka, 1998)

  • Sexual Dimorphism
  • male larger
  • Range length
    6.4 to 14.2 cm
    2.52 to 5.59 in
  • Average length
    9.4 (male), 8.6 (female) cm
    in

Development

Upon hatching, dusky salamander larvae are about 1.6 cm (0.6 in) long and have well-developed limbs. The larvae may stay with their mother for several days or even weeks before going to the water. Because they are aquatic, they have gills, which are small and white. However they can survive in moist terrestrial environments for some time if required, and terrestrial metamorphosis may be possible. After spending 7 to 11 months in the water they undergo metamorphosis (in the spring or summer after hatching). Newly transformed salamanders are 2.8 to 4.4 cm (1.1 to 1.7 in.) long. (Bishop, 1941; Harding, 1997; Hom, 1987; Hulse, et al., 2001; Petranka, 1998)

Reproduction

Dusky salamanders, like most members of the Order Caudata, reproduce with a unique form of internal fertilization. The male deposits a jellylike, sperm-capped glob (called a spermatophore) onto the ground. The female then climbs over the cylindrical or cone-shaped spermatophore and the sperm is allowed to enter her vent. The sperm is stored in her cloaca until breeding. Because courtship occurs both in the spring and in the fall, the sperm may be stored for either a very short period or for a length of many months. (Harding, 1997; Petranka, 1998)

Courtship in dusky salamanders occurs near streams in both spring and fall. Mating occurs on land. A male will approach a female while doing a "butterfly walk," rotating his front limbs similar to a swimmer doing a butterfly stroke. He will wag his tail and nudge the female with his snout in order to identify and stimulate her. Then the male will vigorously press his chin onto the female’s back and arch his body. With a quick snap, he will straighten his body. The snap is so violent that the male may be thrown 5 to 10 cm away from the female. Over time, he will repeat this activity, slowly moving until he is under the female’s head. He reaches back snaps at the female's dorsum or neck, and drags his teeth across her dorsum in order to vaccinate her with pheromone secretions that will make her receptive. Next, the female will straddle his tail, while touching her chin to the base of his tail to facilitate courtship with skin secretions. Usually, the salamanders will remain in this position for some time. Then the male will produce a spermatophore to be picked up by the female via her vent. Sometimes the male places the spermatophore directly onto her cloacal opening. (Gibbs, et al., 2007; Harding, 1997; Hom, 1987; Hulse, et al., 2001; Petranka, 1998)

In summer, females produce 12 to 51 eggs, which are deposited under rocks, logs, mosses or debris near water in the summer. Larger females (based on snout-to-vent length) typically produce larger numbers of eggs. Females stay with the eggs until they hatch, after 40 to 80 days. In most successful nest sites, 70% or more of the eggs will hatch. After two or three years, males will be reproductively mature. For females, three or four years are required. (Bishop, 1941; Harding, 1997; Hom, 1987; Hulse, et al., 2001; Petranka, 1998)

  • Breeding interval
    Dusky salamanders can breed twice yearly, but likely only one clutch per female is produced each year.
  • Breeding season
    Dusky salamanders mate both in the spring and the fall, but fertilization can be delayed and eggs are laid in summer.
  • Range number of offspring
    12 to 51
  • Average number of offspring
    28.6
  • Range time to hatching
    50 to 80 days
  • Range time to independence
    0 to 3 weeks
  • Range age at sexual or reproductive maturity (female)
    3 to 4 years
  • Range age at sexual or reproductive maturity (male)
    2 to 3 years

Females attend to the eggs from deposition to hatching, leaving the nest infrequently at night to feed. Brooding females will aggressively defend their clutch from predators. In one study, brooding female D. f. fuscus returned to their nests after being displaced as much as 32 meters. In the rare occurrences that females did not attend to their clutch, high mortality (often 100%) due to predation or invasion of the eggs by fungal hyphae was observed. (Bishop, 1941; Gibbs, et al., 2007; Harding, 1997; Hom, 1987; Hulse, et al., 2001; Petranka, 1998)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • protecting
      • female

Lifespan/Longevity

No specific information is available on longevity in this species. Related salamander species can be relatively long lived (i.e. several years to a decade or more) for such small animals. (Petranka, 1998)

Behavior

Dusky salamanders are mainly active nocturnally. At night, they will leave the log or rock that gives them protection during the day to find food along a steam or waterway. On moist evenings, salamanders are active from dusk to dawn. While mostly terrestrial, dusky salamanders can sometimes climb up vegetation or rock faces. These salamanders can be active throughout the year if in a spring or spring-fed habitat, but often are inactive in winter. They are generally solitary except during courtship and mating, and larval brooding. (Bishop, 1941; Gibbs, et al., 2007; Hulse, et al., 2001; Petranka, 1998)

  • Range territory size
    1.4 to 114 m^2

Home Range

Adult dusky salamanders have a small home range, and an individual may move only a couple of meters over a period of several months. The actual size of the home range varies between localities and geographic range, ranging from 1.4 square meters to 114 square meters. (Bishop, 1941; Gibbs, et al., 2007; Hulse, et al., 2001; Petranka, 1998)

Communication and Perception

It is thought that the nasolabial groove (characteristic of members of the family Plethodontidae) aids in smelling prey items as well as potential mates. Chemical odors may be transported along the groove and into the mouth, where the vomeronasal organ can transfer the information to the salamander's brain. Also, glands (like the mental gland, located on the chin) are used to communicate with mates when courting. The male will vigorously rub his chin onto the female, as well as bite her, in order to provide her with pheromone secretions until she becomes fully receptive. If a brooding female is returning to her nest after feeding at night, she can recognize which clutch is hers by using chemical cues. Dusky salamanders may bite a threatening predator. Also, a male may attack a another male that is courting a female. (Harding, 1997; Petranka, 1998)

Food Habits

Dusky salamanders are carnivorous, and eat small invertebrates (both terrestrial and aquatic) including earthworms, slugs, snails, crustaceans, spiders, mites, flies and fly larvae, ants, beetles and beetle larvae, centipedes, moths, and mayflies. Dusky salamander larvae eat crustaceans, insect larvae, copepods, and mites. The diet is fairly nonspecific, and they tend to eat whatever is in abundance. Dusky salamander larvae or small juveniles are occasionally eaten by large adults. (Bishop, 1941; Harding, 1997; Hulse, et al., 2001; Petranka, 1998)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms

Predation

Dusky salamanders have a number of predators, including raccoons (Procyon lotor), birds, striped skunks (Mephitis mephitis), shrews (family Soricidae), water snakes (Nerodia species), garter snakes (Thamnophis species), spring salamanders (Gyrinophilus porphyriticus) and red salamanders (Pseudotriton ruber). It has been suggested that predation may impact reproductive success to the point that it restricts the abundance of dusky salamanders in parts of their range from Tennessee to Virginia. Dusky salamander skin is only mildly toxic, so they must rely on other defensive techniques. Dusky salamanders can move with great agility, and are good jumpers. They also have slippery skins which makes grasping by predators difficult. They may actually bite a predator. Like many of the plethodontid salamanders, they can drop their tails when attacked in order to distract the predator enough to make a quick escape. The tail will grow back later, though it may look slightly different than the original. Tail dropping is fairly common in northern dusky salamanders; approximately 50% of adults have missing (recently dropped) or regrown tails. (Bartlett and Bartlett, 2006; Bishop, 1941; Gibbs, et al., 2007; Harding, 1997; Hom, 1987; Hulse, et al., 2001; Petranka, 1998)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Dusky salamanders are second and third order consumers that eat a wide variety of small terrestrial and aquatic invertebrates. They are opportunists and will eat whatever is available in high abundance. Dusky salamanders are prey to a number of animal species representing many vertebrate (and perhaps some invertebrate) groups, including mammals, snakes, birds, and larger amphibians. Desmognathus fuscus often shares its habitat with other species of the genus Desmognathus, and other plethodontid salamanders. It appears that niche partitioning occurs, and animals of the different Desmognathus species have a broader habitat preference in areas of overlap than in areas that the species do not overlap. Other species that have been found to coexist with D. fuscus are seal salamanders (D. monticola), Allegheny Mountain dusky salamanders (D. ochrophaeus), southern dusky salamanders (D. auriculatus), and northern two-lined salamanders (Eurycea bislineata). (Bartlett and Bartlett, 2006; Bishop, 1941; Harding, 1997; Hulse, et al., 2001; Petranka, 1998)

Economic Importance for Humans: Positive

In the southeastern United States, salamanders in the genera Desmognathus, Gyrinophilus, and Pseudotriton are collected and sold as fishing bait for largemouth bass (Micropterus salmoides) and other sport fish. In bait shops, you can find them labeled as "spring salamanders" or, as often, "spring lizards." The lungless (plethodontid) salamanders (including Desmognathus) are important in nutrient cycles in the forest ecosystem, which undoubtedly helps maintain the health of forest resources. (Bartlett and Bartlett, 2006; Bonett, et al., 2007; Harding, 1997; Petranka, 1998)

Economic Importance for Humans: Negative

There are no known adverse effects of Desmognathus fuscus on humans.

Conservation Status

Dusky salamanders can be common where habitat is intact and abundant in areas such as shaded streamsides in moist woods. But they are threatened in some areas by tree removal, which exposes the area to sun, increasing the water temperature and decreasing the humidity. Pollution of waterways can also be a serious threat. The overall effects of bait collection are unknown, but this activity may certainly impact local populations, especially if collection techniques (such as rock turning) disrupt the local habitat. (Harding, 1997; Petranka, 1998)

Other Comments

Desmognathus fuscus was previously considered to be made up of three subspecies: northern dusky salamanders (D. f. fuscus), spotted dusky salamanders (D. f. conanti), and Santeetlah dusky salamanders (D.f. santeetlah). However, most authorities now consider these three to be separate species: D. fuscus, D. conanti, and D. santeetlah. The range of northern dusky salamanders is as described above. Spotted dusky salamanders range from southern Illinois and western Kentucky south to the Gulf Coast. Santeetlah dusky salamanders occur only in a small geographical area high in the Unicoi, Great Smoky, and Great Balsam mountains of North Carolina and Tennessee.

The three traditional subspecies are very similar in physical appearance, with only subtle differences. D. f. santeetlah is usually the smallest and darkest. D. f. conanti is usually the most colorful, and often has 6 to 8 pairs of gold or red spots (or single lateral lines) along the back. The pattern on D. f. conanti likely comes from the juvenile character (present in all subspecies) of a wavy band and yellowish or reddish spots along the back. Desmognathus f. fuscus varies from brown or reddish brown to gray or olive, with slightly darker markings on the top and sides. The base of the tail is typically olive, yellow, or bright chestnut (a bit lighter than the body). The belly is whitish with some dark speckles (in D. f. fuscus) or lighter speckles (in D. f. conanti). The belly of D.f. santeetlah is yellowish with dark speckles. Usually there is a light stripe from the eye to the back of the mouth. (Bartlett and Bartlett, 2006; Bonett, et al., 2007; Conant and Collins, 1998; Harding, 1997; Hulse, et al., 2001; Petranka, 1998)

Hybridization sometimes occurs between D. fuscus and a close relative, mountain dusky salamanders (Desmognathus ochrophaeus) in Pennsylvania and Ohio. Extensive interbreeding occurs between D. fuscus and D. santeetlah where their ranges overlap in the northwestern Great Smoky Mountains. (Hulse, et al., 2001; Petranka, 1998)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Hannah Edwards (author), Michigan State University, James Harding (editor, instructor), Michigan State University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynous

having more than one female as a mate at one time

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

References

Bartlett, R., P. Bartlett. 2006. Guide and Reference to the Amphibians of Eastern and Central North America (North of Mexico). Gainseville, Florida: University Press of Florida.

Bishop, S. 1941. The Salamanders of New York. Albany: New York State Museum Bulletin, No. 324.

Bonett, R., K. Kozak, D. Vieites, A. Bare, J. Wooten, S. Trauth. 2007. The importance of comparative phylogeography in diagnosing introduced species: a lesson from the seal salamander, Desmognathus monticola. BMC Ecology, 7(7): Published Online. Accessed December 05, 2008 at http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2020456.

Bonnett, R. 2002. Analysis of the contact zone between the dusky salamanders Desmognathus fuscus and Desmognathus conanti . Copeia, 2002: 344-355.

Conant, R., J. Collins. 1998. Reptiles and Amphibians: Eastern/Central North America. New York: Houghton Mifflin Company.

Gibbs, J., A. Breisch, P. Ducey, G. Johnson, J. Behler, R. Bothner. 2007. The Amphibians and Reptiles of New York State: Identification, Natural History, and Conservation. New York: Oxford University Press.

Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor, Michigan: University of Michigan Press.

Hom, C. 1987. Reproductive ecology of female dusky salamanders, Desmognathus fuscus (Plethodontidae) in the Southern Appalachians. Copeia, 1987 (3): 768-777.

Hulse, A., C. McCoy, E. Censky. 2001. Amphibians and Reptiles of Pennsylvania and the Northeast. New York: Cornell University Press.

Petranka, J. 1998. Salamanders of the United States and Canada. Washington: Smithsonian Institute Press.

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