Nerodia sipedon - (Linnaeus, 1758)
Northern Watersnake
Other English Common Names: Northern Water Snake, northern watersnake
Synonym(s): Natrix sipedon
Taxonomic Status: Accepted
Related ITIS Name(s): Nerodia sipedon (Linnaeus, 1758) (TSN 174251)
French Common Names: couleuvre d'eau
Unique Identifier: ELEMENT_GLOBAL.2.105253
Element Code: ARADB22060
Informal Taxonomy: Animals, Vertebrates - Reptiles - Snakes
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Reptilia Squamata Colubridae Nerodia
Genus Size: C - Small genus (6-20 species)
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Concept Reference
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Concept Reference: Collins, J. T. 1990. Standard common and current scientific names for North American amphibians and reptiles. 3rd ed. Society for the Study of Amphibians and Reptiles. Herpetological Circular No. 19. 41 pp.
Concept Reference Code: B90COL01NAUS
Name Used in Concept Reference: Nerodia sipedon
Taxonomic Comments: Formerly included in genus Natrix.
Conservation Status
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NatureServe Status

Global Status: G5
Global Status Last Reviewed: 02Feb2016
Global Status Last Changed: 30Oct1996
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G5 - Secure
Nation: United States
National Status: N5 (05Oct1996)
Nation: Canada
National Status: N5 (02Feb2016)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (S5), Arkansas (S5), Colorado (S4), Connecticut (S5), Delaware (S5), District of Columbia (S4), Florida (SNR), Georgia (S5), Illinois (SNR), Indiana (SNR), Iowa (S5), Kansas (S5), Kentucky (S5), Louisiana (S4), Maine (S5), Maryland (S5), Massachusetts (S5), Michigan (S5), Minnesota (S4), Mississippi (S5), Missouri (SNR), Nebraska (S5), New Hampshire (S5), New Jersey (S5), New York (S5), North Carolina (S5), Ohio (SNR), Oklahoma (S4), Pennsylvania (S5), Rhode Island (S5), South Carolina (SNR), South Dakota (S1), Tennessee (S5), Texas (S1), Vermont (S3), Virginia (S5), West Virginia (S5), Wisconsin (S4)
Canada Ontario (S5), Quebec (S3)

Other Statuses

Implied Status under the Committee on the Status of Endangered Wildlife in Canada (COSEWIC):PS:SC,NAR
Comments on COSEWIC: The Lake Erie Watersnake is Special Concern and the Northern Watersnake is Not at Risk.
IUCN Red List Category: LC - Least concern

NatureServe Global Conservation Status Factors

Range Extent: 200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Range Extent Comments: The large range encompasses most of the eastern United States and a relatively small portion of adjacent southeastern Canada, from Maine, southern Quebec, and southern Ontario to Minnesota, extreme southern South Dakota, and eastern Colorado, and south to extreme northern Texas, southern Louisiana, the Florida panhandle, western South Carolina, and North Carolina, at elevations from sea level to around 1,675 meters (5,500 feet) (Conant and Collins 1991, Hammerson 1999, Ernst and Ernst 2003, Stebbins 2003, Gibbons and Dorcas 2004).

Area of Occupancy: >12,500 4-km2 grid cells
Area of Occupancy Comments:  

Number of Occurrences: > 300
Number of Occurrences Comments: This species is represented by a very large number of occurrences (subpopulations).

Population Size: >1,000,000 individuals
Population Size Comments: Adult population size is unknown but probably exceeds 1,000,000. This snake is abundant in most areas of its range.

Number of Occurrences with Good Viability/Integrity: Very many (>125)

Overall Threat Impact: Low
Overall Threat Impact Comments: No major threats are known. This snake tolerates a good deal of habitat alteration.

Short-term Trend: Relatively Stable (<=10% change)
Short-term Trend Comments: Extent of occurrence, area of occupancy, number of subpopulations, and population size probably are relatively stable.

Long-term Trend: Decline of <30% to increase of 25%

Other NatureServe Conservation Status Information

Distribution
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Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) The large range encompasses most of the eastern United States and a relatively small portion of adjacent southeastern Canada, from Maine, southern Quebec, and southern Ontario to Minnesota, extreme southern South Dakota, and eastern Colorado, and south to extreme northern Texas, southern Louisiana, the Florida panhandle, western South Carolina, and North Carolina, at elevations from sea level to around 1,675 meters (5,500 feet) (Conant and Collins 1991, Hammerson 1999, Ernst and Ernst 2003, Stebbins 2003, Gibbons and Dorcas 2004).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AL, AR, CO, CT, DC, DE, FL, GA, IA, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, NC, NE, NH, NJ, NY, OH, OK, PA, RI, SC, SD, TN, TX, VA, VT, WI, WV
Canada ON, QC

Range Map
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted.

Range Map Compilers: NatureServe, 2005


U.S. Distribution by County Help
State County Name (FIPS Code)
NC Beaufort (37013), Carteret (37031), Currituck (37053), Dare (37055), Hyde (37095), Pamlico (37137)
OH Erie (39043), Ottawa (39123)
OK Adair (40001), Muskogee (40101)
SD Bon Homme (46009)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
03 Albemarle (03010205)+, Pamlico (03020104)+, Pamlico Sound (03020105)+, Lower Neuse (03020204)+, White Oak River (03020301)+
04 Cedar-Portage (04100010)+, Sandusky (04100011)+
10 Lewis and Clark Lake (10170101)+
11 Dirty-Greenleaf (11110102)+, Robert S. Kerr Reservoir (11110104)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Help
General Description: Front part of body crossbanded, rear part crossbanded or blotched; pattern sometimes obscure, especially in large individuals; belly often with red or orange blotches; upper scales keeled, with a pair of minute pits near the tip of each scale; anal scale divided; more than two scales between eye and nostril; maximum total length around 150 cm. The end of the tail not uncommonly is missing. Mature male: knobbed keels on dorsal scales near vent. Newborn: average generally 16-19 cm snout-vent length. Source: Hammerson (1999).
Reproduction Comments: Courtship and mating occur in spring (generally late April to early June. Reproductive females give birth to up to several dozen young usually from August to October in the north, primarily in July or August in the southern part of the range. Females sexually mature in 2-3 years (Vogt 1981). Females may not breed every year.
Ecology Comments: Movements may exhibit great individual variation; in Wisconsin, individuals moved over an area of > 15 hectares (usually much less) during spring-summer (Tiebout and Cary 1987).

If captured by hand, northern water snakes may release voluminous fluid from the vent, including the malodorous secretions from the cloacal sacs, and they usually bite, often drawing blood with the sharp teeth. Adults have high endurance and may expend considerable energy in fleeing or defending themselves.

Habitat Type: Freshwater
Non-Migrant: Y
Locally Migrant: N
Long Distance Migrant: N
Estuarine Habitat(s): Bay/sound, Herbaceous wetland, River mouth/tidal river
Riverine Habitat(s): BIG RIVER, CREEK, Low gradient, MEDIUM RIVER, Moderate gradient, SPRING/SPRING BROOK
Lacustrine Habitat(s): Shallow water
Palustrine Habitat(s): FORESTED WETLAND, HERBACEOUS WETLAND, Riparian, SCRUB-SHRUB WETLAND
Special Habitat Factors: Burrowing in or using soil, Fallen log/debris
Habitat Comments: Habitats include creeks, rivers, canals, lakes, oxbows, ponds, reservoirs, marshes, bogs, and swamps. This snake usually inhabits freshwater but also occurs in brackish and saltwater habitats in some areas (Ernst and Ernst 2003, Gibbons and Dorcas 2004). It frequents sunny areas, especially piles of flood-deposited debris, logs, or rocks, at the water's edge. Hibernation sites often are in burrows, among rocks, or in deep crevices, at the water's edge or in uplands near water.
Adult Food Habits: Carnivore, Piscivore
Immature Food Habits: Carnivore, Piscivore
Food Comments: Feed opportunistically on fishes and amphibians; sometimes eats invertebrates and small mammals.
Adult Phenology: Circadian, Hibernates/aestivates
Immature Phenology: Circadian, Hibernates/aestivates
Phenology Comments: Northern water snakes are inactive during cold winter months in the north, where most activity occurs from March-April through October.
Length: 135 centimeters
Economic Attributes Not yet assessed
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Management Summary Not yet assessed
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Population/Occurrence Delineation
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Group Name: Medium And Large Colubrid Snakes

Use Class: Not applicable
Minimum Criteria for an Occurrence: Occurrences are based on evidence of historical presence, or current and likely recurring presence, at a given location. Such evidence minimally includes collection or reliable observation and documentation of one or more individuals (including eggs) in or near appropriate habitat where the species is presumed to be established and breeding.
Separation Barriers: Busy highway or highway with obstructions such that snakes rarely if ever cross successfully; major river, lake, pond, or deep marsh (this barrier pertains only to upland species and does not apply to aquatic or wetland snakes); densely urbanized area dominated by buildings and pavement.
Separation Distance for Unsuitable Habitat: 1 km
Separation Distance for Suitable Habitat: 10 km
Separation Justification: Available information on movements of colubrid snakes is limited to a small minority of species. These data indicate that nearly all species have home ranges smaller or much smaller than 25 ha (e.g., less than 3 ha, Pituophis catenifer in California, Rodriguez-Robles 2003), with some up to about 75 ha (Heterodon platirhinos, average 50 ha, Plummer and Mills 2000), and the largest up to 225 ha in the biggest colubrids (Drymarchon, summer mean 50-100 ha, USFWS 1998).

Radiotelemetry data for Pantherophis indicate that residents of hibernacula that are 1-2 km apart (with suitable intervening habitat) probably interbreed (Prior et al. 1997, Blouin-Demers and Weatherhead 2002). However, "evidence of genetic structure even over short distances (e.g., 2-20 km) implies that gene flow among rat snake populations can be easily disrupted" (Prior et al. 1997). Loughheed et al. (1999) found evidence of substantial genetic exchange among local hibernacula (< 6 km apart), but gene flow over distances of 10s of km appears to be substantially less. Based on extensive radio-tracking data, Blouin-Demers and Weatherhead (2002) found that home range size of Pantherophis averaged 18.5 ha and ranged up to 93 ha; based on the most mobile individuals, Pantherophis from hibernacula up to 8 km apart can come together for mating. Pantherophis and probably other colubrids exhibit high fidelity to hibernacula and shift even to nearby sites only rarely (Prior et al. 2001).

Many of the several studies that report small home ranges for colubrids did not employ methods (e.g., radio telemetry) suitable for detecting full annual or multi-annual home range size, dispersal, or other long-distance movements, so these may have yielded underestimates of home ranges or activity areas.

At least some colubrids, including medium-sized species such as garter snakes, not uncommonly move between areas up to a few kilometers apart, and several species make extensive movements of up to several kilometers, so separation distances of 1-2 km for suitable habitat are too small for medium-sized and large colubrids.

A separation distance of 10 km for suitable habitat was selected as most appropriate for snakes assigned to this Specs Group because it seems generally unlikely that two locations separated by less than 10 km of suitable habitat would represent distinct occurrences.

For the purposes of these occurrence specifications, upland habitat is regarded as unsuitable habitat for aquatic and wetland snakes. For upland snakes, shallow or patchy wetlands are treated as unsuitable habitat whereas large deepwater habitats (subjective determination) are barriers.

Inferred Minimum Extent of Habitat Use (when actual extent is unknown): .5 km
Date: 12Feb2013
Author: Hammerson, G.
Notes: Separation distance for suitable habitat was changed from 5 km to 10 km based on comments from Dale Jackson (12 Feb 2013).
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 28Jan2010
NatureServe Conservation Status Factors Author: Hammerson, G.
Element Ecology & Life History Edition Date: 28Jan2010
Element Ecology & Life History Author(s): Hammerson, G.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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"Data provided by NatureServe in collaboration with Bruce Patterson, Wes Sechrest, Marcelo Tognelli, Gerardo Ceballos, The Nature Conservancy-Migratory Bird Program, Conservation International-CABS, World Wildlife Fund-US, and Environment Canada-WILDSPACE."

Citation for Amphibian Range Maps of the Western Hemisphere:
IUCN, Conservation International, and NatureServe. 2004. Global Amphibian Assessment. IUCN, Conservation International, and NatureServe, Washington, DC and Arlington, Virginia, USA.

Acknowledgement Statement for Amphibian Range Maps of the Western Hemisphere:
"Data developed as part of the Global Amphibian Assessment and provided by IUCN-World Conservation Union, Conservation International and NatureServe."

NOTE: Full metadata for the Bird Range Maps of North America is available at:
http://www.natureserve.org/library/birdDistributionmapsmetadatav1.pdf.

Full metadata for the Mammal Range Maps of North America is available at:
http://www.natureserve.org/library/mammalsDistributionmetadatav1.pdf.

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