Water moccasins, also known as cottonmouths, are venomous snakes found throughout the southeastern United States. While they possess venom that can cause harm, bites to humans are relatively uncommon and typically occur when the snake feels threatened or is provoked. These snakes are semi-aquatic, comfortable both in water and on land, and their presence in wetland habitats often leads to encounters with people. Understanding their characteristics and behaviors is important for safely coexisting with them.
Identifying Water Moccasins
Water moccasins are heavy-bodied snakes, growing to an average length of 2 to 4 feet, though some can be larger. Their coloration varies, ranging from dark brown or black to olive, or even banded brown or yellow. A distinguishing feature is their broad, triangular head, noticeably wider than their neck. They also have a dark stripe through the eye and a deep heat-sensing pit between their eye and nostril. When viewed from above, a cottonmouth’s eyes are often not visible due to an overhanging brow ridge.
A key identification behavior is their defensive display, where they open their mouths wide to reveal a strikingly white interior, earning them the name “cottonmouth.” Unlike many other snakes, water moccasins swim with most of their body riding on the surface of the water, with their head elevated. They are frequently found in wet areas like swamps, marshes, ponds, lakes, and streams, but can also be seen on land, basking on logs or branches near the water’s edge. Juvenile cottonmouths often exhibit more distinct patterns and possess a bright yellow tail tip, which they use to attract prey.
The Nature of Their Danger
The danger associated with water moccasins stems from their venom, which is primarily hemotoxic. This venom affects blood cells and tissues, leading to a range of symptoms at the bite site. Common symptoms include immediate and severe pain, rapid swelling, discoloration, and bruising. The venom can also cause tissue damage and, in severe cases, necrosis.
Beyond localized effects, a bite can also lead to systemic symptoms such as nausea, vomiting, weakness, difficulty breathing, and a drop in blood pressure. While water moccasin bites are serious and require immediate medical attention, they are rarely fatal to humans, especially with prompt and proper treatment. Some bites, known as “dry bites,” may not involve venom injection, resulting in milder symptoms. However, treat all suspected venomous snake bites as medical emergencies.
Encountering and Responding to Water Moccasins
Minimizing the risk of encountering water moccasins involves being aware of their preferred habitats and exercising caution. When in areas known to harbor these snakes, such as swamps, marshes, or near bodies of water, wear appropriate footwear and clothing. Observe your surroundings and avoid placing hands or feet in areas where you cannot see, such as dense underbrush or submerged logs.
If you encounter a water moccasin, give it space and avoid provoking it. Do not attempt to handle, capture, or kill the snake, as this greatly increases the risk of a bite. Water moccasins often display warning behaviors, such as coiling or opening their white mouths, before striking. If a bite occurs, seek immediate medical attention by calling emergency services.
While waiting for medical help, keep the bitten area still and, if possible, lower than the heart. Remove any jewelry or constricting clothing from the affected limb before swelling begins. Gently wash the bite wound with soap and water and cover it with a clean, dry dressing. Avoid these actions, as they are not effective and can cause further harm:
Applying a tourniquet.
Cutting the wound.
Trying to suck out venom.
Applying ice.
Distinguishing from Harmless Look-Alikes
Many non-venomous water snakes are frequently mistaken for water moccasins, leading to unnecessary fear. Non-venomous water snakes, such as common water snakes, have more slender heads that are not distinctly wider than their necks. Their pupils are round, unlike the vertical, cat-like pupils of water moccasins.
When swimming, non-venomous water snakes often submerge most of their bodies, with only their heads visible above the surface. This contrasts with water moccasins, which float with most of their body on top of the water. While some non-venomous water snakes may flatten their heads when threatened to appear more formidable, their flattened head still looks less blocky and thick compared to a cottonmouth’s naturally broad head. Water snakes typically flee quickly when disturbed, unlike water moccasins, which may hold their ground and display their white mouth as a warning. Recognizing these differences can prevent misidentification and promote safer interactions with both venomous and non-venomous snake species.