Common Watersnake
Nerodia sipedon
Description
The Common Watersnake is one of North America's most widespread aquatic snakes, yet it is surprisingly uncommon at Snake Road. Among the species we've classified as 'rare' at Snake Road, this is the one most likely to be upgraded to Extremely Rare. Adults are typically brown, gray, or reddish-brown with a series of dark crossbands near the neck that transition into alternating blotches farther down the body. Older individuals often become so dark that the pattern is difficult to see, especially when wet.
Like other watersnakes, the Common Watersnake has strongly keeled scales, a heavy body, and round pupils. The belly is usually light-colored with dark half-moon markings or irregular reddish blotches.
Although widespread throughout Illinois, this species is encountered far less often at Snake Road than the Diamond-backed, Mississippi Green, or Plain-bellied Watersnakes.
Behavior
Common Watersnakes are active predators that feed on fish, frogs, salamanders, and other aquatic animals. They are excellent swimmers and readily dive beneath the water when disturbed.
If cornered or handled, they can be highly defensive, flattening the body, striking repeatedly, and releasing a strong-smelling musk. Like all watersnakes, they are completely nonvenomous despite their intimidating behavior.
Habitat
Elsewhere in Illinois, Common Watersnakes inhabit nearly every type of permanent water, including ponds, lakes, rivers, marshes, and streams. Around Snake Road, however, they appear to be much less common than other Nerodia species. Most records come from wetlands and roadside ditches associated with the swamp west of the road and nearest the southern gate.
Where You're Most Likely to See One
A Common Watersnake is most likely to be encountered near the swamp or roadside ditches during the spring or fall migrations. Most visitors who see a watersnake at Snake Road are actually observing a Diamond-backed, Mississippi Green, or Plain-bellied Watersnake instead.
Commonly Confused With
Diamond-backed Watersnake
Nerodia rhombiferThis is the species most often mistaken for the Common Watersnake at Snake Road. Diamond-backed Watersnakes are generally larger and have a distinctive chain-like pattern that forms dark diamond shapes across the back. Common Watersnakes instead have crossbands near the neck that transition into alternating side blotches toward the tail.
- Dark crossbands near the neck
- Alternating blotches farther down the body
- No continuous chain-like dorsal pattern
- Usually smaller overall
- Heavily marked belly
- Distinctive chain-like body pattern
- Dark diamond shapes across the back
- Generally larger and heavier-bodied
- Pattern remains more consistent along the body
- Commonly encountered at Snake Road
Mississippi Green Watersnake
Nerodia cyclopionBoth species can appear dark olive or brown and are frequently found around water. Mississippi Green Watersnakes usually have a more uniform appearance, larger eyes set higher on the head, and less distinct body patterning than Common Watersnakes.
- Usually shows crossbands and alternating blotches
- Eyes positioned more conventionally on the head
- Pattern may remain visible on younger adults
- Marked belly with half-moons or blotches
- Brown, gray, or reddish-brown coloration
- More uniform olive or brown appearance
- Larger eyes positioned higher on the head
- Body pattern is usually less distinct
- Often appears broadly dark and unpatterned
- Strongly associated with swamp habitat
Plain-bellied Watersnake
Nerodia erythrogasterAdult Plain-bellied Watersnakes are often nearly patternless, lacking the bold crossbands and blotches typical of the Common Watersnake. Their plain yellow, orange, or reddish underside also contrasts with the heavily marked belly of the Common Watersnake.
- Crossbands and alternating body blotches
- Belly marked with half-moons or reddish blotches
- Pattern often visible in younger individuals
- Usually brown, gray, or reddish-brown
- Rarely encountered at Snake Road
- Adults are often nearly patternless
- Plain yellow, orange, or reddish underside
- No heavily marked belly
- Body may appear uniformly dark
- More frequently encountered at Snake Road
