Living near water often brings us into contact with various types of snakes, and it’s natural to be concerned about distinguishing between harmless and venomous species. Among the snakes found in and around water, the Water Moccasin, also known as the Cottonmouth (Agkistrodon piscivorus), is a venomous snake that often gets confused with harmless watersnakes (Nerodia genus). Misidentification can lead to unnecessary fear and, sadly, the killing of non-venomous snakes that play vital roles in our ecosystem. Being able to confidently identify a Water Moccasin from a harmless watersnake is crucial for both your peace of mind and the conservation of these often misunderstood creatures. This guide will provide you with clear visual cues to differentiate between these two types of snakes, empowering you to safely coexist with wildlife near water.
| Harmless Watersnake | Venomous Water Moccasin | |
|---|---|---|
| Habitat Preference | YES, commonly found near water | YES, commonly found near water |
| Body Build | SLENDER and lean | HEAVY and thick |
| Body Coloration | Dark, frequently with bands or patterns | Dark, frequently with bands or patterns |
| Scale Texture | Keeled (ridged), giving a rough appearance | Keeled (ridged), giving a rough appearance |
| Head Shape | Narrow or FLATTENED appearance | Broad, BLOCKY, and triangular |
| Neck Definition | Neck NOT distinct from the head | Distinct NECK, narrower than the head |
| Facial Markings | May have dark markings, but not always a clear eyestripe | Often has a noticeable dark facial band or eyestripe |
| Pupil Shape | ROUND pupils | VERTICAL, cat-like pupils |
| Facial Pits | Lacks heat-sensing pits | Possesses heat-sensing pits between nostril and eye |
Important Note: While this guide helps distinguish between watersnakes and Water Moccasins, remember that even non-venomous snakes can bite if they feel threatened. The safest approach to any snake is to observe it from a distance and allow it to go on its way. They are a natural part of the environment and contribute to ecological balance.
Key Differences to Tell Watersnakes and Water Moccasins Apart
When trying to identify a snake near water, focus on these primary physical characteristics: body size and shape, and head and neck features. These are the most reliable visual cues for quick and safe identification.
1. Body Size and Shape: Is It Bulky or Slender?
The overall body build is a significant indicator. Water Moccasins are known for their heavy, thick bodies relative to their length, and they possess short, stout tails. In contrast, harmless watersnakes have more slender bodies and longer, thinner tails for the same length.
Thick, Heavy Body: Characteristic of a Water Moccasin
Venomous Water Moccasins exhibit a distinctly robust body shape. Even younger moccasins will appear quite thick. Their tails are noticeably shorter and thicker compared to watersnakes. Mature adults can become very dark, sometimes almost entirely black, which can obscure patterns but not their bulky build.
A young Water Moccasin demonstrates the characteristic thick body and short, stout tail of venomous cottonmouths. The blocky head shape is also apparent. Adult Water Moccasins often darken considerably with age. (Image provided by a concerned individual who unfortunately killed the snake before identification. It’s crucial to remember that approaching or handling snakes increases the risk of bites. Leaving them undisturbed is always the safest course of action.)
Long, Slender Body: Typical of a Harmless Watersnake
Non-venomous watersnakes, along with many other harmless snake species, display a more slender body form. Their bodies are proportionally thinner for their length, and their tails are noticeably longer and more tapered.
This Brown Watersnake clearly shows the slender body and long, thin tail typical of harmless watersnakes. Note also the narrower head shape in comparison to the Water Moccasin.
Flattened Body: A Defensive Tactic, Not a Body Type
It’s important to note that harmless watersnakes may flatten their bodies and heads when they feel threatened. This defensive behavior can make them appear larger and more intimidating. However, even when flattened, a watersnake’s body will still appear more slender for its length than a Water Moccasin’s, and their tail will remain long and thin.
This Banded Watersnake is flattening its body and neck as a defensive posture. Even when flattened, the body remains slender relative to its length, and the tail is still long and thin, distinguishing it from the naturally thick body of a Water Moccasin.
2. Head and Neck Size and Shape: Blocky vs. Slender
The shape and size of the head, and the distinctness of the neck, are other vital clues in differentiating these snakes. Water Moccasins have large, blocky, triangular heads that are clearly wider than their necks. Harmless watersnakes have more slender heads that blend smoothly into their bodies, with no distinct neck.
Large, Blocky Head and Distinct Neck: Hallmarks of a Water Moccasin
Water Moccasins possess a distinctly large, blocky head that is significantly wider than their neck. This gives them a somewhat triangular or diamond-shaped head when viewed from above. The neck is noticeably constricted right behind the broad head.
A Water Moccasin’s thick, blocky head shape is clearly visible in this image. The neck is also distinctly narrower than the head. (Again, this photo was taken after the snake was killed unnecessarily. Observing from a safe distance is always recommended).
Even juvenile Water Moccasins exhibit the characteristic wide, blocky head and a well-defined neck that is narrower than the head. This feature is present from a young age. (This photo also illustrates an instance where a snake was killed before identification. Remember, snakes are best left alone).
Slender Head and Indistinct Neck: Typical of Watersnakes
Harmless watersnakes have heads that are slender and more elongated. Their heads are not as wide or blocky as a Water Moccasin’s, and their heads tend to blend smoothly into their bodies without a clearly defined neck.
This Banded Watersnake demonstrates a slender, elongated head that seamlessly transitions into the body, lacking a noticeable neck constriction.
This Green Watersnake also shows the typical slender head shape of watersnakes, with no distinct neck separating the head from the body.
Flattened Head: Defensive Posture, Not True Head Shape
Similar to body flattening, harmless watersnakes may flatten their heads defensively, making them appear somewhat triangular. However, even when flattened, the head will still look flattened rather than truly thick and blocky, and the neck will not be distinctly narrower than the head. The overall head shape will remain more elongated than a Water Moccasin’s.
This Banded Watersnake is flattening its head in defense, giving it a more triangular appearance. However, note that the head still appears flattened rather than thick and blocky, and the neck remains almost as wide as the head, unlike the distinct neck of a Water Moccasin.
By focusing on body thickness, head shape, and neck definition, you can become more adept at distinguishing between harmless watersnakes and venomous Water Moccasins. Remember to always observe snakes from a safe distance and avoid handling them. Coexistence and respect for wildlife are key to a healthy environment.
