Description: A small but sturdy salamander, the upper body of the northern dusky salamander varies in colour from reddish-brown to gray or olive, with a white or grey underside. The body is sparsely covered with dark spots or mottling concentrated on the sides. It also has a light dorsal stripe or two dark stripes that continue on to the first part of the tail. Juvenile colouring consists of five to eight pairs of dorsal spots or blotches located between the front and hind legs. Older individuals tend to be uniformly dark brown or black. As with all dusky salamander species, both juveniles and adults have a pale single stripe outlined in black that extends from the eye and runs diagonally to the rear of the jaw. Additionally, both have 14 costal grooves, larger hind limbs than forelimbs, and a keeled (knife-like) tail that is triangular in cross-section and compressed laterally at the base. The tail is less than half its body length and is normally lighter in colour in comparison to the body. Adults attain lengths of up to 14 cm, with the average length of adult males and females being 9.4 cm and 8.6 cm, respectively. Being from the family Plethodontidae, the northern dusky salamander is lungless. It absorbs oxygen through the skin and membranous tissue located in the mouth and throat. The dusky salamander also has a naso-labial groove, which aids olfaction, and thus the ability to search out mates and prey through smell.
Habitat: In the northern extent of their range, the northern dusky salamander inhabits saturated soil near springs, seepages, and small tributaries of small headwater streams otherwise known as the riparian zone. Habitat quality is optimal in undisturbed watersheds and where water is running or trickling and there is an abundance of forest cover The forest cover serves to keep the water cool and well oxygenated, and maintains moisture and temperature at levels necessary for salamander survival. In the south, the northern dusky salamander can be found in upland streams as well as floodplains, sloughs and muddy sites.
Range: This species is native to North America, and occurs throughout central-eastern regions of Canada and the United States, from southern New Brunswick , southeastern Quebec and southern Ontario south to South Carolina. Populations south of this range are now thought to belong to other, previously-synonymized species such as D. conanti. An isolated breeding population exists in eastern Michigan; however, it is not known whether this population is natural or was introduced.
Diet: The northern dusky salamander is considered to be feeding generalist, with its diet based on food availability. Stream salamanders are known to be significant predators. This is namely because they are dominant vertebrates within headwater riparian forest ecosystems, with a biomass greater than that reported for fish, birds or small mammals. The species is carnivorous and consumes a variety of aquatic and terrestrial invertebrates. Larvae feed predominantly on aquatic invertebrates (such as copepods, other crustaceans and insect larvae), as well as mites, whereas the adult diet consists of 60 to 85% of terrestrial invertebrates, including arthropods (such as crustaceans, spiders, mites, flies and fly larvae, ants, beetles and beetle larvae, centipedes, moths and mayflies), snails, slugs and earthworms. When prey is in excess, the northern dusky salamander does typically have a preference for the larger and fleshier terrestrial invertebrates, such as earthworms. The aquatic portion of the adult's diet is habitat specific and commensurate with the seasonal abundance and diversity of invertebrates.
Reproduction: Due to their lack of mobility, some populations of dusky salamander are genetically distinct. Breeding is terrestrial and occurs annually in spring or fall and includes elaborate courtship rituals. Adult males have papillose cloacal lips and a small mental gland. These glandular tissues become enlarged when sexually active. Female individuals lack a mental gland and have folded cloacal lips. For reproduction, the male applies the snout, cheeks and mental gland to the snout of the female, who usually responds by picking up the spermatophore. Fecundity increases with body size.
Females normally deposit between 10 and 30 eggs under logs, moss or rocks located streamside where soil is saturated with water. Clutch size has been known to vary geographically and can be as large as forty-five, or as few as eight. Females remain with their eggs for an incubation period of six to ten weeks (45 to 60 days) in order to protect them from desiccation and predation . The larvae are predominantly aquatic and approximately 1.5 cm in length upon hatching. The larvae then metamorphose into semi-terrestrial adults, with juvenile salamanders being 2.8 to 4.4 cm in length. Their biphasic life cycle includes an aquatic state of seven to 16 months, followed by a semi-terrestrial adult stage. The northern dusky salamander attains sexual maturity at approximately three to four years of age. Life expectancy is 10 to 15 years.
Status: Listed as Least Concern in view of the large extent of occurrence, large number of subpopulations and locations, and large population size.
Taxonomy: NOTE: Desmognathus fuscus will be split into Desmognathus conanti, Desmognathus fuscus, Desmognathus campi, Desmognathus catahoula, Desmognathus tilleyi, Desmognathus anicetus, Desmognathus bairdi, and Desmognathus lycos.
Disclaimer: ITIS taxonomy is based on the latest scientific consensus available, and is provided as a general reference source for interested parties. However, it is not a legal authority for statutory or regulatory purposes. While every effort has been made to provide the most reliable and up-to-date information available, ultimate legal requirements with respect to species are contained in provisions of treaties to which the United States is a party, wildlife statutes, regulations, and any applicable notices that have been published in the Federal Register. For further information on U.S. legal requirements with respect to protected taxa, please contact the U.S. Fish and Wildlife Service.
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