Animal Diversity Web

Ge­o­graphic Range

Dwarf wa­ter­dogs (Nec­turus punc­ta­tus) are lo­cated in the Pied­mont re­gion of the Ap­palachian High­lands, and more com­monly in the south­ern At­lantic Coastal Plain in the east­ern United States. They are found in rivers and streams through­out east­ern Geor­gia and reach as far north as Vir­ginia. The west­ern­most bound­ary of their ge­o­graphic range ex­tends into the broad low­lands of the Tri­as­sic Basin in North Car­olina. Dwarf wa­ter­dogs are pre­sent in the Chesa­peake Bay re­gion, but only in south­east­ern Vir­ginia. (Du­ell­man and Sweet, 1999; Dunn, 1918; Hardy Jr., 1972; Martof, et al., 1980)

• Biogeographic Regions
• nearctic
  • native

Habi­tat

Op­ti­mal habi­tat for dwarf wa­ter­dogs con­sists of silt-bot­tomed stream pools with leafy cover. They are also found in open sandy areas and pre­fer slow-mov­ing water over areas with high flow rates. (Jen­son, et al., 2008)

• Habitat Regions
• freshwater

• Terrestrial Biomes
• mountains

• Aquatic Biomes
• rivers and streams

Phys­i­cal De­scrip­tion

Dwarf wa­ter­dogs are the small­est of all water dog species. Adults range in head to tail length from 11.5 to 15.9 mm. For com­par­i­son, adult black war­rior wa­ter­dogs typ­i­cally range in size from 175 and 200 mm. Fe­males gen­er­ally have longer tails than males of the same body length, how­ever, males and fe­males of a given body length are typ­i­cally the same mass. Dwarf wa­ter­dogs are slate-gray or brown with small, scat­tered pale spots. The dor­sum tends to be dark, while the ven­ter is often pale in color. In gen­eral, wa­ter­dogs have red ex­ter­nal gills that pro­trude from both sides of the or­gan­ism’s head. (Bart, et al., 1997; Co­nant and Collins, 1998; Lan­noo, 2005; Martof, et al., 1980; Meffe and Shel­don, 1987)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry

• Sexual Dimorphism
• female larger

De­vel­op­ment

Dwarf wa­ter­dogs do not un­dergo meta­mor­pho­sis and lar­vae are con­sid­ered adults once their re­pro­duc­tive sys­tem has fully ma­tured. The lar­val stage lasts for a min­i­mum of 2 years. The small­est re­ported larva was only 28 mm long. As lar­vae, their bod­ies are uni­formly brown in color. Ju­ve­niles are often found in more shal­low water than adults and com­monly occur in bun­dles of leaves. Like lar­vae, ju­ve­niles are brown, but de­velop a bluish white color along the ven­ter. Dwarf wa­ter­dogs be­come sex­u­ally ma­ture by 5 years of age, and when fully ma­ture, they range in length from 26 to 116 mm. (Lan­noo, 2005; Will­son, et al., 1999)

• Development - Life Cycle
• metamorphosis

Re­pro­duc­tion

There is no in­for­ma­tion avail­able re­gard­ing the mat­ing sys­tem of dwarf wa­ter­dogs.

Lit­tle is know of the re­pro­duc­tive be­hav­ior of dwarf wa­ter­dogs, how­ever, other wa­ter­dog species re­pro­duce aquat­i­cally. The larger a dwarf wa­ter­dog, the greater the num­ber of oocytes in the ovaries, which con­tain yolked and un­y­olked oocytes dur­ing mid-au­tumn. Most preg­nant fe­males carry 15 to 55 eggs. Av­er­age egg di­am­e­ter has been re­ported as 4 and 4.2 mm and may de­pend on the num­ber of eggs being car­ried. Prior to mat­ing, which oc­curs dur­ing win­ter, male testes be­come large, firm, and yel­low with dark pig­men­ta­tion. De­spite gen­der, in­di­vid­u­als reach re­pro­duc­tive ma­tu­rity by age 5 or when they be­come 65 to 70 mm in head-body length. Al­though no nests have been dis­cov­ered, it is thought that dwarf wa­ters at­tach their eggs to the un­der­side of logs and other ob­jects in the water. (Folk­erts, 1971; Lan­noo, 2005; Meffe and Shel­don, 1987)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual

• Breeding season

  Dwarf waterdogs breed during winter.

• Range number of offspring

  15 to 55

• Average age at sexual or reproductive maturity (female)

  5 years

• Average age at sexual or reproductive maturity (male)

  5 years

There is no in­for­ma­tion avail­able re­gard­ing parental care in dwarf wa­ter­dogs.

Lifes­pan/Longevity

Only lim­ited in­for­ma­tion on the lifes­pan of dwarf wa­ter­dogs ex­ists. A sin­gle spec­i­men cap­tured in the wild and taken to the Cincin­nati Zoo lived for 5 years and 8 months. Be­cause they reach sex­ual ma­tu­rity at 5 years of age, dwarf wa­ter­dogs likely live for more than 10 years. How­ever, no in­for­ma­tion ex­ists to con­firm this. (Folk­erts, 1971; Lan­noo, 2005)

Be­hav­ior

Lit­tle in­for­ma­tion is avail­able con­cern­ing the gen­eral be­hav­ior of dwarf wa­ter­dogs. Nu­mer­ous dwarf wa­ter­dogs are com­monly found in­hab­it­ing a sin­gle area, sug­gest­ing these an­i­mals are not ter­ri­to­r­ial. They do not hi­ber­nate, re­main­ing ac­tive even dur­ing the win­ter­time. In order to min­i­mize the ef­fects of cold dur­ing win­ter, dwarf wa­ter­dogs often heap to­gether in leaf lit­ter. (Lan­noo, 2005)

• Key Behaviors
• motile

Home Range

The av­er­age home range size of dwarf wa­ter­dogs is cur­rently un­known. Black war­rior wa­ter­dogs in the Grand River of north­east­ern Ohio have an av­er­age home range of 136.1 square me­ters dur­ing the sum­mer. How­ever, this is the largest of wa­ter­dog species and thus, it likely has a larger home range than do dwarf wa­ter­dogs. (Lan­noo, 2005)

Com­mu­ni­ca­tion and Per­cep­tion

There is no in­for­ma­tion avail­able con­cern­ing com­mu­ni­ca­tion and per­cep­tion in dwarf wa­ter­dogs. (Folk­erts, 1971; Lan­noo, 2005)

Food Habits

Dwarf wa­ter­dogs are preda­tory and com­monly con­sume gas­tropods, pele­cy­pods, oligochaetes, arach­nids, isopods, clado­cer­ans, os­tra­cods, cope­pods, am­phipods, chilopods, and a va­ri­ety of in­sects. In ad­di­tion, adults often com­sume an­nelids, cray­fish , and even other sala­man­ders, sug­gest­ing they may be can­ni­bal­is­tic. Young have been known to eat an­nelids, am­phi­pod, mil­li­pedes, and in­sects and their lar­vae. Ev­i­dence sug­gests that males re­duce, or even dis­con­tinue feed­ing ac­tiv­ity dur­ing the breed­ing sea­son, though lar­vae are thought to feed through­out the en­tire year. (Braswell and Ash­ton Jr., 1985; Folk­erts, 1971; Meffe and Shel­don, 1987)

• Primary Diet
• carnivore
  • insectivore
  • eats non-insect arthropods

• Animal Foods
• amphibians
• fish
• insects
• terrestrial non-insect arthropods
• terrestrial worms

Pre­da­tion

Al­though no ev­i­dence ex­ists sug­gest­ing preda­tors spe­cific to this species, dwarf wa­ter­dogs likely fall prey to preda­ceous or­gan­isms in­hab­it­ing the same areas. Po­ten­tial preda­tors in­clude aquatic in­sects and snakes, cray­fish, and large sala­man­ders. Al­though no ev­i­dence ex­ists re­gard­ing anti-preda­tory be­hav­ior in dwarf wa­ter­dogs, they likely hide from po­ten­tial threats in the soft sub­strate. Their col­oration cam­ou­flages them from po­ten­tial preda­tors and likely helps re­duce risk of pre­da­tion. (Lan­noo, 2005)

• Anti-predator Adaptations
• cryptic

Ecosys­tem Roles

Dwarf wa­ter­dogs prey upon the aquatic lar­vae of nu­mer­ous arthro­pods, which may help con­trol in­sect pests through­out its ge­o­graphic range. Al­though par­a­sites spe­cific to this species are not known, the gills and skin of con­gener­ics have proven to be prime habi­tat for a num­ber of dif­fer­ent endo and ec­topar­a­sites, such as trema­todes. Pro­teochep­halids in­habit the in­testines of cer­tain wa­ter­dog species. (Lan­noo, 2005; Tobey, 1985)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Recre­ational fish­er­men com­monly use wa­ter­dogs as bait for large­mouth bass and cat­fish. (Lan­noo, 2005)

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no known ad­verse ef­fects of dwarf wa­ter­dogs on hu­mans.

Con­ser­va­tion Sta­tus

Al­though dwarf wa­ter­dogs are clas­si­fied as a species of least con­cern on the IUCN's Red List of Threat­ened Species, cur­rent pop­u­la­tion trends are un­known and thus, po­ten­tial threats to their per­sis­tence are dif­fi­cult to pre­dict. Dwarf wa­ter­dogs occur in sev­eral pro­tected areas through­out their ge­o­graphic range. (Lan­noo, 2005; Tobey, 1985)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

Con­trib­u­tors

Lind­sey Hughes (au­thor), Rad­ford Uni­ver­sity, Gre­gory Za­gursky (ed­i­tor), Rad­ford Uni­ver­sity, John Berini (ed­i­tor), An­i­mal Di­ver­sity Web Staff.

Ref­er­ences

Bart, H., M. Bai­ley, Jr., R. Ash­ton, P. Moler. 1997. Tax­o­nomic and Nomen­clat­ural Sta­tus of the Upper Black War­rior River Wa­ter­dog. Jour­nal of Her­petol­ogy, 31 (2): 192-201. Ac­cessed Jan­u­ary 29, 2011 at http://​www.​jstor.​org/​stable/​1565387.

Braswell, A., R. Ash­ton Jr.. 1985. Dis­tri­b­u­tion, ecol­ogy, and feed­ing habits of Nec­turus lewisi. Brim­leyana, 10: 13-35.

Co­nant, R., J. Collins. 1998. Field Guide to Rep­tiles and Am­phib­ians. New York, New York: Houghton Mif­flin Har­court.

Du­ell­man, W., S. Sweet. 1999. Dis­tri­b­u­tion pat­terns of am­phib­ians in the Nearc­tic re­gion of North Amer­ica. Bal­ti­more, Mary­land: John Hop­kins Uni­ver­sity Press.

Dunn, E. 1918. The Col­lec­tion of Am­phibia Cau­data of the Mu­seum of Com­par­a­tive Zo­ol­ogy. Bul­letin of the Mu­seum of Com­par­a­tive Zo­ol­ogy at Har­vard Col­lege, 62: 443-472.

Folk­erts, G. 1971. Notes on South Car­olina Sala­man­ders. Jour­nal of the El­isha Mitchell Sci­en­tific So­ci­ety, 87: 206-208.

Gunter, G., W. Brode. 1964. Nec­turus in the State of Mis­sis­sippi with Notes on Ad­ja­cent Areas. Her­peto­log­ica, 20 (2): 114-126. Ac­cessed Feb­ru­ary 01, 2011 at http://​www.​jstor.​org/​stable/​pdfplus/​3890579.​pdf.

Hardy Jr., J. 1972. Am­phib­ians of the Chesa­peake Bay Re­gion. Chesa­peake Sci­ence, 13: S123-S128.

In­di­viglio, F. 2010. Newts and sala­man­ders: every­thing about se­lec­tion, care, nu­tri­tion, dis­eases, breed­ing, and be­hav­ior. Haup­pauge, New York: Bar­ron's Ed­u­ca­tional Se­ries.

Jen­son, J., C. Camp, W. Gib­bons. 2008. Am­phib­ians and Rep­tiles of Geor­gia. Athens, Geor­gia: The Uni­ver­sity of Geor­gia Press.

Lan­noo, M. 2005. Am­phib­ian de­clines: the con­ser­va­tion sta­tus of United States species. Berke­ley, Cal­i­for­nia: Uni­ver­sity of Cal­i­for­nia Press.

Martof, B., W. Palmer, J. Bai­ley, J. Har­ri­son III. 1980. Am­phib­ians and Rep­tiles of the Car­oli­nas and Vir­ginia. Chapel Hill, North Car­olina: The Uni­ver­sity of North Car­olina Press.

Meffe, G., A. Shel­don. 1987. Habi­tat Use by Dwarf Wa­ter­dogs (Nec­turus punc­ta­tus) in South Car­olina Streams, with Life His­tory Notes. Her­peto­log­ica, 43 (4): 490-496. Ac­cessed Jan­u­ary 28, 2011 at http://​www.​jstor.​org/​stable/​3892150.

Neill, W. 1948. Hi­ber­na­tion of Am­phib­ians and Rep­tiles in Rich­mon County, Geor­gia. Her­peto­log­ica, 4 (3): 107-114. Ac­cessed Feb­ru­ary 01, 2011 at http://​www.​jstor.​org/​stable/​pdfplus/​27669570.​pdf?​acceptTC=true.

Palmer, W., A. Braswell. 1995. Retiles of North Car­olina. Chapel Hill, North Car­olina: Chapel Hill Uni­ver­sity of North Car­olina Press.

Scott, D., B. Metts, W. Gib­bons. 2003. Sea­sonal Wet­lands and Golf Courses. Golf Course Man­age­ment, 2003: 85-89. Ac­cessed Feb­ru­ary 01, 2011 at http://​archive.​lib.​msu.​edu/​tic/​gcman/​article/​2003nov85.​pdf.

Sher­man, C. 1943. A Hand­book of Sala­man­ders. The Sala­man­ders of the United States, of Canada, and of Lower Cal­i­for­nia.. Ithaca, New York: Com­stock Pub­lish­ing Com­pany.

Tobey, F. 1985. Vir­ginia's Am­phib­ians and Rep­tiles: A Dis­tri­b­u­tional Sur­vey. Pur­cel­lville, VA: Mr. Print.

Vitt, L., J. Cald­well. 2009. Her­petol­ogy. Mary­land Heights, Mis­souri: Aca­d­e­mic Press.

Will­son, J., Y. Ko­rnilev, W. An­der­son, G. Con­nette, E. Eskew. 1999. "Dwarf Wa­ter­dog Nec­turus Punc­ta­tus" (On-line). Herps of North Car­olina. Ac­cessed April 28, 2011 at http://​www.​herpsofnc.​org/​herps_​of_​nc/​salamanders/​Necpun/​Nec_​pun.​html.