Animal Diversity Web

Ge­o­graphic Range

North­ern water snakes are found in south­ern On­tario and the north­east­ern United States from Ne­braska and Kansas in the west to the At­lantic coast and as far south as North Car­olina and south­ern Mis­souri. (Hard­ing, 1997)

• Biogeographic Regions
• nearctic
  • native

Habi­tat

North­ern water snakes uti­lize many dif­fer­ent aquatic habi­tats, such as: rivers, streams, sloughs, lakes, ponds, bogs, marshes, and im­pound­ments. They pre­fer open areas that pro­vide many spots for them to bask in the sun and rel­a­tively still wa­ters. They may move onto land, es­pe­cially the ju­ve­niles, but they never go to far from the aquatic en­vi­ron­ment. When they are not bask­ing or search­ing for prey items they can be found be­neath flat rocks, logs, boards or other types of cover. North­ern water snakes are the most com­mon snakes near water sources through­out north­east­ern North Amer­ica. (Hard­ing, 1997)

• Habitat Regions
• temperate
• freshwater

• Terrestrial Biomes
• taiga
• savanna or grassland
• forest

• Aquatic Biomes
• lakes and ponds
• rivers and streams

• Wetlands
• marsh
• swamp
• bog

• Other Habitat Features
• riparian

Phys­i­cal De­scrip­tion

These are dark-col­ored snakes, brown­ish, tan or gray­ish in ap­pear­ance. The back and sides have a se­ries of square blotches al­ter­nat­ing with each other that may merge to form bands. Adult snakes can ap­pear solid brown or black, es­pe­cially when dry. The belly is usu­ally white, yel­low­ish, or orangish with dark half-moon-shaped black edges. Ju­ve­niles have red­dish brown sad­dles on a tan, brown, or gray back­ground. Males are usu­ally smaller than fe­males. (Behler and King, 1979; Hard­ing, 1997; Jor­dan, 1929; Tyn­ing, 1990)

Scales are keeled and the anal plate is di­vided, with 21-25 scales at mid­body.

North­ern water snakes are medium to large snakes, rang­ing from 61 to 140 cm. They range from 19 to 27.3 cm at birth.

• Other Physical Features
• heterothermic

• Sexual Dimorphism
• female larger

• Range length

  61 to 140 cm

  24.02 to 55.12 in

Re­pro­duc­tion

• Mating System
• polygynous

Male north­ern water snakes are able to re­pro­duce when they are 21 months old. Fe­male snakes begin to breed when they are three years old and pro­duce a sin­gle lit­ter each year. Most re­pro­duc­tion oc­curs while in or near their hi­ber­na­tion sites be­tween mid-April and mid-June. Tem­per­a­ture and lat­i­tude may cause vari­a­tion in these times. (Bau­man and Met­ter, 1977)

Dur­ing breed­ing, a male comes along side a fe­male and rubs his chin along her back, oc­ca­sion­ally giv­ing a spas­modic jerk. He then twines his tail around hers and brings the cloa­cal open­ings into con­tact. Usu­ally only one male cop­u­lates with a sin­gle fe­male; on oc­ca­sion there may be two. (Hard­ing, 1997; Tyn­ing, 1990)

Ges­ta­tion can last any­where from 3 to 5 months. Young snakes are born alive (not laid as eggs) from July to Sep­tem­ber. The lit­ter ranges in size from 4 to 99 off­spring. Larger fe­males tend to have larger lit­ters.

• Key Reproductive Features
• iteroparous
• seasonal breeding
• sexual
• fertilization
• ovoviviparous

• Breeding interval

  Northern water snakes mate once yearly

• Breeding season

  April to June

• Range number of offspring

  4 to 99

• Range gestation period

  3 to 5 months

• Average age at sexual or reproductive maturity (female)

  3 years

• Average age at sexual or reproductive maturity (female)
  Sex: female

  730 days

  AnAge

• Average age at sexual or reproductive maturity (male)

  21 months

• Average age at sexual or reproductive maturity (male)
  Sex: male

  730 days

  AnAge

Fe­male north­ern water snakes nur­ture and pro­tect their young be­fore they are born. Young water snakes be­come in­de­pen­dent at birth, and are ca­pa­ble of hunt­ing and car­ing for them­selves.

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

Lifes­pan/Longevity

North­ern water snakes have been known to live up to 9 years and 7 months in cap­tiv­ity. Their lifes­pan in the wild is un­known.

• Range lifespan
  Status: captivity

  115 (high) months

• Average lifespan
  Status: captivity

  9.6 years

  AnAge

Be­hav­ior

North­ern water snakes are only so­cial dur­ing the fall and spring after over­win­ter­ing. They can be found in groups at bask­ing sites coiled to­gether. For the most part they are soli­tary an­i­mals, es­pe­cially in the warmer months. It is quite com­mon to find north­ern water snakes sun­ning them­selves dur­ing the warm part of days. They can be found on over­hang­ing branches, walk­ways, beaver lodges, dried cat­tail stems, and many shal­low areas in the water.)

North­ern water snakes can be found dur­ing the day or at night, but are more ac­tive dur­ing the day­light hours. Be­cause of their pref­er­ence for aquatic habi­tats they are com­monly mis­taken for ven­omous water moc­casins, Agk­istrodon pis­civ­o­rous. North­ern water snakes are not ven­omous but they are ag­gres­sive and should al­ways be treated with care and re­spect. (Tyn­ing, 1990)

• Key Behaviors
• diurnal
• hibernation
• solitary

Com­mu­ni­ca­tion and Per­cep­tion

North­ern water snakes prob­a­bly com­mu­ni­cate with each other pri­mar­ily through touch and smell. They also use their sense of sight and de­tec­tion of vi­bra­tions to lo­cate prey.

• Communication Channels
• tactile
• chemical

• Other Communication Modes
• pheromones

• Perception Channels
• visual
• tactile
• vibrations
• chemical

Food Habits

North­ern water snakes are car­ni­vores and scav­engers. They eat a va­ri­ety of prey items, in­clud­ing am­phib­ians (adults and tad­poles), fish (alive or dead), cray­fish, large in­sects, leeches, other snakes, tur­tles, birds, and small mam­mals such as white-footed mice. They have been known to herd schools of fish or tad­poles to the edge of bod­ies of water where they can prey upon many at one time. North­ern water snakes hunt both dur­ing the day and at night. They are not con­stric­tors, they sim­ply swal­low their prey alive. (Tyn­ing, 1990)

• Primary Diet
• carnivore
  • eats terrestrial vertebrates

• Animal Foods
• birds
• mammals
• amphibians
• reptiles
• fish
• carrion
• insects
• terrestrial non-insect arthropods
• aquatic crustaceans

Pre­da­tion

North­ern water snakes often es­cape preda­tors by swim­ming off across a body of water or by div­ing below the sur­face, where they an­chor them­selves to veg­e­ta­tion or logs. They usu­ally re­main sub­merged for about 5 min­utes but are ca­pa­ble of re­main­ing below water for an hour and a half.

When con­fronted, north­ern water snakes flat­ten their bod­ies and jaws and begin to strike and bite fe­ro­ciously. They also re­lease a foul-smelling musk and may defe­cate to dis­cour­age preda­tors. When ex­tremely ag­i­tated they will also re­gur­gi­tate their last meal. North­ern water snakes are preyed on by large snakes, such as milk snakes and rac­ers, and by rac­coons, skunks, and foxes.

• Known Predators

  • large snakes (Serpentes)
  • raccoons (Procyon lotor)
  • skunks (Mephitinae)
  • foxes (Canidae)

Ecosys­tem Roles

North­ern water snakes con­trol the pop­u­la­tions of their pri­mary prey, in­clud­ing fish, am­phib­ians, and other rep­tiles.

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Con­trary to pop­u­lar be­lief, north­ern water snakes are quite ben­e­fi­cial to fish pop­u­la­tions. They feed on dis­eased and dying fish and help to con­trol areas where over­pop­u­la­tion may exist and could stunt fish growth. This may ac­tu­ally help the sport fish­ing in­dus­try. (Hard­ing, 1997)

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

North­ern water snakes could po­ten­tially be a prob­lem for fish hatch­eries and fish farms. (Hard­ing, 1997)

Con­ser­va­tion Sta­tus

North­ern water snakes are abun­dant through­out their range.

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Other Com­ments

Snakes of this species are often killed by peo­ple who are afraid of them, and con­fuse them with ven­omous species, such as rat­tlesnakes. North­ern water snakes will bite if you bother them, but they are not ven­omous.

Con­trib­u­tors

Al­li­son Poor (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Mer­ritt Gillil­land (au­thor), Michi­gan State Uni­ver­sity, James Hard­ing (ed­i­tor), Michi­gan State Uni­ver­sity.

Ref­er­ences

Bau­man, M., D. Met­ter. 1977. Re­pro­duc­tive cycle of the north­ern water snake, Nero­dia sipedon (Rep­tilia, Ser­pentes, Col­u­bri­dae). Jour­nal of Her­petol­ogy, 11(1): 51-59.

Behler, J., F. King. 1979. The Audubon So­ci­ety Field Guide to North Amer­i­can Rep­tiles and Am­phib­ians. New York: Al­fred A. Knoph, Inc..

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

Jor­dan, D. 1929. Man­ual of the Ver­te­brate An­i­mals. New York: World Book Com­pany.

Tyn­ing, T. 1990. Stokes Na­ture Guides: A guide to Am­phib­ians and Rep­tiles. Boston, MA: Lit­tle, Brown and Com­pany.