Northern Water Snake Nerodia sipedon. Reptile. Photograph taken by the author. Copyright © 2025 Now I Wonder. All rights reserved.

Complete Guide To The Northern Water Snake

ByChristine Species Guides

Northern Water Snake

  • Non-venomous, but bite aggressively in their own defense if blocked from escape and forced to do so.
  • Their saliva contains an anticoagulant that causes bites to bleed profusely (Behler and King 2020).

Northern Water Snake Images

How To Identify Northern Water Snakes In NC

  • Northern Water Snakes are large, heavy-bodied, aquatic snakes that can grow up to 53 inches (134.6 cm) long (Behler and King 2020).
  • Their long, thick bodies are covered in keeled scales.
  • The front part of their bodies typically have alternating red-brown and light brown bands. These bands split into alternating side blotches from their middles to their tails.
  • Their bellies are mostly yellow with a red, half-moon shape on each belly scale (Gibbons and Dorcas 2005).
  • Their pale lower jaws have multiple, dark, vertical stripes.
  • Northern Water Snakes are sexually dimorphic, with females growing larger than males on average.
    • Female Northern Water Snakes also grow faster than males.
      • In a study researching the impact of prey size on the head size of Northern Water Snakes, females grew from the starting average snout-vent length (SVL) of 184 mm (+ – 1.9 mm) to 400 mm SVL in an average of 425 days. It took the males in the study—which started out the same length as the females—an average of 643 days to reach the same size (Swartwout et al. 2020, https://doi.org/10.1655/Herpetologica-D-18-00007).
  • Northern Water Snakes live in and along ponds, lakes, swamps, marshes, canals, streams, and even man-made retention ponds.
    • Northern Water Snakes are aquatic and never found very far from their freshwater habitats. In one study of operating body temperatures of snakes in northern Virginia, a total of 67 individual snakes were observed (39) or captured (28), all of whom were found no more than 10 meters away from water (Ernst et al. 2014).

Notes On Northern Water Snakes In NC

  • Northern Water Snakes are non-venomous snakes that feed on:
    • Amphibians like Bullfrogs, Green Frogs, Squirrel Tree Frogs, and Green Tree Frogs.
    • Small fish
    • Juvenile turtles
    • Crustacheans
    • Small mammals (Behler and King 2020).
      • They actively forage for their prey and poke their heads into crevices formed by rocks and plant roots. They also sometimes trap small fish in shallow water with a body coil (Gibbons and Dorcas 2005).
      • They swallow their prey alive and whole.
  • Northern Water Snakes mate in early summer between late April and June, usually in trees and bushes that overhang water.
    • Like other snake species, female Northern Water Snakes produce and release sex pheromones to advertise readiness to mate to area males. But aquatic Northern Water Snakes can’t lay their pheromone trails down on dry land in the way of terrestrial snakes. Instead, Northern Water Snake pheromones sit on top of the water surface. Male snakes swim with their heads raised above the water surface, testing the air for pheromones with tongue flicks, then hone in on receptive females by swimming towards the more concentrated scent (Aldridge et al 2005).
    • Females are ovoviviparous and usually bear 15-30 live young in the fall (Behler and King 2020).
  • In the spring and fall, Northern Water Snakes in NC are active during the early morning and late evening. In summer, they hunt mostly at night (Gibbons and Dorcas 2005).
  • Northern Water Snakes like to bask in the sun in low-hanging trees and shrubs or on rocks but always have an easy escape route into water.
    • They are very skittish snakes that prefer to flee threats rather than face them down. However, they are notoriously bad-tempered if cornered (Martof et al. 1980) and can—and will—inflict painful bites if forced to actively defend themselves.
    • If harassed and unable to escape, these snakes will flatten their heads to make themselves appear larger and more threatening, gape their mouths, and bite readily and repeatedly in their own defense.
    • Wounds caused by Northern Water Snakes bleed for a long time, thanks to an anticoagulant in the snakes’ saliva (Behler and King 2020).

Northern Watersnake Classification

Phylum

Chordata

Class

Reptilia

Order / Suborder

Squamata / Serpentes

Family

Colubridae (Colubrid Snakes

Genus

Nerodia

Species

N. sipedon

Binomial Name

Nerodia sipedon

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Christine
Christine is the creator and author of NowIWonder.com, a website dedicated to the animals and plants that share our world, and the science that helps us understand them. Inspired by lifelong exploration and learning, Christine loves to share her knowledge with others who want to connect with wild faces and wild spaces.
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