Amphibians of North Carolina

Scientific Name:	Common Name:		Family (Alpha):

Proteidae Members:
Necturus punctatus - Dwarf Waterdog

Taxonomy

Class: Amphibia

Order: Caudata

Family: Proteidae


Taxonomic Comments: No subspecies are currently recognized. Ashton et al. (1980) and Guttman et al. (1990) found that N. punctatus is genetically distinct from other Necturus is the Southeast and is most closely related to N. lewisi. The spotted morph of N. punctatus from the Pee Dee drainage is indistinguishable from the unspotted morph from the Neuse River drainage and appears to be conspecific with other N. punctatus populations.
Species Comments:

Identification

Description: As the name implies, the Dwarf Waterdog is the smallest of our three Necturus species. Individuals retain their bushy gills throughout life and have only four toes on each hindfoot rather than five, which is the case for most salamander species. The adults have a slender build, a depressed, blunt snout, and vary from 11.5-19 cm TL. Most are uniformly slate gray to brown above, and often with fine lighter flecking. Most populations throughout the range lack dark spots, but populations in the Cape Fear and Lumber River systems have a spotted morph that has small dark spots that are most prevalent on the tail (Beane et al. 2010, Martof et al. 1980, Dundee 1998). The venter of both spotted and unspotted morphs is typically pale and lacks spots. However, in the Chowan and Roanoke River drainages in the northeastern section of North Carolina, the venter is sometimes dark. The tail length comprises about 38% of the total length on average and the caudal fin is well-developed and strongly compressed laterally (Dundee 1998). Sexually active males have a swollen cloaca and two enlarged cloacal papillae that point backwards. Mature males and females are similar in average SVL, but females have proportionately longer tails than males (Meffe and Sheldon 1987). In areas of North Carolina where this species is found with the Neuse River Waterdog (N. lewisi), it can be distinguished by its small size, more slender and cylindrical body, unspotted venter, and relatively small spots that are about the size of the eyes (Beane et al. 2010).

The hatchlings and small larvae are uniformly brown above. The tail fin is slightly mottled, and the venter is bluish white. Coloration gradually shifts from brown to gray as larvae reach 40-50 mm SVL (Folkerts 1971).

Online Photos: Google iNaturalist

Observation Methods: Individuals are most easily collected by dipnetting through leaf beds or other bottom debris, particularly during the cooler months of the year.

AmphibiaWeb Account

Distribution in North Carolina

Distribution Comments: The Dwarf Waterdog inhabits small and medium sized streams from the Chowan River in southeastern Virginia to the Ocmulgee-Altamaha River system in central and southern Georgia. This species occurs primarily in the Atlantic Coastal Plain, but occurs sporadically in the lower Piedmont.
Distribution Reference: Beane et al. 2010, Dundee 1998, Petranka 1998
County Map: Clicking on a county returns the records for the species in that county.


GBIF Global Distribution

Key Habitat Requirements

Habitat: The Dwarf Waterdog is strictly aquatic and is most commonly found in smaller streams. Specimens have primarily been collected from deeper sections of streams that are sluggish and have accumulations of mud, silt, and leaves (Folkerts 1971, Meffe and Sheldon 1987). The juveniles often burrow into the silty bottoms of streams, while the juveniles and adults often congregate in leaf beds during the winter months. This species is rare or absent from the mainstream of the Neuse and Tar rivers where N. lewisi prevails (Braswell and Ashton 1985). However, it occurs in many of the smaller tributaries where N. lewisi is less frequently encountered.

Biotic Relationships: The natural predators of N. punctatus have not been identified, but undoubtedly include fishes and other aquatic predators.

See also Habitat Account for Coastal Plain Still and Sluggish Waters

Life History and Autecology

Breeding and Courtship: Courtship behavior has not been described for this species. Mating probably occurs in winter, followed by oviposition from March-May (Meffe and Sheldon 1987). A gravid female collected on 12 April in South Carolina had 33 ovarian eggs that averaged 4.2 mm in diameter (Folkerts 1971). Other females collected at the same time had already oviposited. Meffe and Sheldon (1987) collected a single female on 20 February with enlarged ovarian eggs that averaged 4 mm. Specimens taken during the autumn in South Carolina contained 15-55 mature ova, and the number of ova was positively correlated with female SVL. Most individuals contained 20-40 mature ova.

Reproductive Mode: The nests have not been discovered. Females presumably attach their eggs singly to the undersides of logs, rocks or other debris as is the case with all other Necturus species (Petranka 1998).

Aquatic Life History: Many aspects of the natural history of the juvenile and adult stages are poorly documented (Petranka 1998). The larvae live in both shallow and deep waters (Brimley 1924) and sometimes burrow in silt deposits in quiet pools (Martof et al. 1980). The adults are active during the winter, but appear to be relatively inactive during the hotter summer months of the year. They often congregate in leaf beds in relatively quiet water in winter (Brimley 1924, Martof et al. 1980) and appear to feed outside of cover mostly at night (Sollenberger 2013).

The Dwarf Waterdog appears to be a gape-limited, opportunistic, generalist predator. Individuals incorporates larger prey into the diet as they grow and their gape widens. Braswell and Ashton (1985) reported that ostracods, blackflies, ceratopogonids, and dytiscid beetles were the most numerically important prey in 14 immature N. punctatus that they examined from North Carolina. Other prey that were taken included oligochaetes, cladocerans, copepods, isopods, amphipods, mayflies, caddisflies, and flies. Larger prey such as isopods and caddisflies were more important in the diets of adults, but many other prey were eaten. These included snails, clams, pseudoscorpions, amphipods, centipedes, mayflies, stoneflies, dobsonflies, true flies, hymenopterans, and lepidopteran larvae. Folkerts (1971) found millipedes, caddisfly larvae, fly larvae, amphipods, and oligochaetes in six immature specimens that were collected in South Carolina in March and April. Of these, earthworms were the most important food item. Nine of 20 adults had empty stomachs, which suggests that the adults feed little during the breeding season. In South Carolina 54% of specimens examined by Meffe and Sheldon (1987) also had empty digestive tracts. Prey in the remaining specimens included earthworms, mayflies, chironomids, salamanders, crayfish, plant material, and unidentified insects (Petranka 1998).

Sollenberger (2013) found that the use of leaf packs during the cooler months of the year varied among size cohorts in the South Fork of the Edisto River in South Carolina. Small numbers of adults were found in leaf packs from November through January, but not from February through April. Immature individuals (< 35 mm) did not reach peak density until the end of April, while intermediate sizes peaked in February and were not present in the final sample in April. The mean SVL of the smallest size cohort increased from 22.9 mm in mid-November to 30.6 mm by the end of April, while mean mass increased from 0.22 g to 0.74 g over the same period. The use of leaf packs during the cooler months paralleled a corresponding peak in invertebrate densities in leaf packs at the same time, suggesting that individuals use these primarily as winter foraging sites. Increased stream discharge rates also appeared to trigger movements into leaf packs.

Most individuals mature sexually when 65-70 mm SVL or larger (Hecht 1958). In a South Carolina study all specimens < 60 mm SVL were juveniles, while those > 75 mm SVL were adults (Meffe and Sheldon 1987). The smallest mature males and females in a sample taken by Folkerts (1971) were 84 and 81 mm SVL, and a size-frequency analysis suggests that most individuals mature during their fifth year of life.

General Ecology

Population Ecology: We have much to learn about the population biology of this species. We know very little, for example, about the sizes of local populations, mechanisms that set limits on local population size, and gene flow between populations.

Community Ecology: In their extensive survey of Necturus in the Neuse or Tar River system, Braswell and Ashton (1985) collected N. punctatus at 54 sites. It was found to be sympatric with N. lewisi at 19 sites, but no N. punctatus were found in the mainstream of the Neuse or Tar rivers. These two species co-occur together near the Fall Line Zone and could potentially compete for food resources given their strong overlap in diet. Large N. lewisi may also prey on small N. punctatus. Ashton (1985) introduced two adults and two subadult N. punctatus into a tank with an adult N. lewisi to observe interspecific interactions. The two subadult N. punctatus were immediately eaten and the adults were viciously attacked by the resident N. lewisi. The bites were directed to the head and gills of the intruder and resulted in deep lacerations that became infected and were fatal.

Adverse Environmental Impacts

Status in North Carolina

NHP State Rank: S5

Global Rank: G5

Environmental Threats: This species appears to be most threatened by increased sediment loads and the general degradation of streams due to urbanization, agricultural activities, industrial and commercial development, land clearing, and infrastructure development.

Status Comments: Braswell and Ashton (1985) collected N. punctatus at 54 of 361 sites sampled in North Carolina and concluded that viable populations occur in most areas of the range. A comprehensive survey has not been conducted since then, and it is uncertain if this species has declined in parallel with the decline of N. lewisi in North Carolina.

Stewardship: Viable populations are best maintained by having relatively unimpaired streams, along with adjoining floodplain forest that provide adequate inputs of leaf litter to support invertebrates and provide cover for the juveniles and adults.

Photo Gallery for Necturus punctatus - Dwarf Waterdog		10 photos are shown.
	Recorded by: Hartness,B Moore Co.	Recorded by: Hartness,B Moore Co.
	Recorded by: Scott Bolick Richmond Co.	Recorded by: Scott Bolick Richmond Co.
	Recorded by: Scott Bolick Richmond Co.	Recorded by: Scott Bolick Richmond Co.
	Recorded by: C. Helms, S. Hartley Moore Co.	Recorded by: P.Hart, S.Lambiase Harnett Co.
	Recorded by: J. Corbett, K. Thompson Cumberland Co.	Recorded by: J. Fields Cumberland Co.

Necturus punctatus - Dwarf Waterdog

Photo Gallery for Necturus punctatus - Dwarf Waterdog

10 photos are shown.