True sea snakes are not native or established residents of the Gulf of Mexico. While extremely rare occurrences of a specific sea snake species might occur as vagrants, they do not form stable, breeding populations. Most snake sightings in the Gulf are likely misidentifications of local water snake species well-adapted to coastal and brackish environments.
Understanding True Sea Snakes
True sea snakes are reptiles highly adapted to a fully marine existence, spending most or all of their lives in oceanic waters. They possess distinctive physical traits, including paddle-like, flattened tails and laterally compressed bodies that aid in swimming. Many species also have specialized salt-excreting glands and dorsally located nostrils, allowing them to breathe efficiently at the surface. Their fangs are small and fixed.
These marine reptiles primarily inhabit the warm coastal waters of the Indo-Pacific region, spanning from the Indian Ocean to the western Pacific Ocean. The absence of true sea snakes in the Atlantic Ocean, including the Gulf of Mexico, is attributed to several geographical and climatic barriers. Cold currents off the Cape of Good Hope in South Africa prevent their eastward dispersal from the Indo-Pacific. Furthermore, the Isthmus of Panama formed a land bridge, separating the Pacific and Atlantic Oceans before modern sea snake species evolved. While the Yellow-bellied sea snake (Pelamis platurus) has a wide distribution across the tropical Indo-Pacific and can drift into eastern Pacific waters, its appearance in the Gulf of Mexico would be an isolated event.
Snakes Found in Gulf Waters
The snakes most commonly encountered in or near Gulf of Mexico waters are not true sea snakes but native species adapted to freshwater, brackish, or coastal saltwater habitats. Various species of water snakes from the genus Nerodia are prevalent. The Saltmarsh snake (Nerodia clarkii), for example, is a nonvenomous species found along the tidal salt marshes and brackish estuaries of the Gulf Coast from Texas to Florida. These snakes tolerate saltwater but do not possess specialized salt glands like true sea snakes.
Other Nerodia species, such as the Common Watersnake (Nerodia sipedon), are found in freshwater environments but may venture into brackish areas. These snakes are often mistaken for venomous species due to their appearance or behavior. Cottonmouths (Agkistrodon piscivorus), also known as water moccasins, are venomous snakes that inhabit slow-moving freshwater and brackish marshes throughout the southeastern United States, including the Gulf states. Cottonmouths are strong swimmers and can colonize islands off both the Atlantic and Gulf coasts.
Identifying Snakes in the Gulf
Distinguishing between true sea snakes and local water snakes in the Gulf requires observing key physical characteristics. True sea snakes have paddle-like, flattened tails, which are vertically compressed for propulsion through water. Their bodies are laterally compressed, and they have small or absent belly scales, making them cumbersome on land.
In contrast, local Nerodia water snakes have rounder bodies and tapered tails, similar to terrestrial snakes. These nonvenomous snakes have keeled scales and round pupils. Cottonmouths, a venomous species, have a thick, heavy body with a short, abruptly tapering tail. Their heads are large, blocky, and distinctly wider than their necks, with vertical, cat-like pupils. Juvenile cottonmouths can also exhibit a bright yellow or yellowish-green tail tip.
What to Do if You Encounter a Snake
Encountering any snake in or near Gulf waters warrants caution and respect. Maintain a safe distance and observe the animal from afar. Never attempt to handle, provoke, or harm a snake, as most bites occur when humans interact with them.
If in a boat, steer clear of the snake’s path. If on shore, calmly back away, allowing the snake space to retreat.
Should a bite occur, treat it as a medical emergency. Immediately call emergency services, such as 911, and remain calm. Keep the bitten area still and, if possible, below the heart. Remove any jewelry or tight clothing from the affected limb to accommodate potential swelling. Gently wash the bite wound with soap and water.
Avoid common misconceptions like cutting the wound, attempting to suck out venom, or applying a tourniquet or ice, as these actions can worsen the situation. Seek immediate medical attention, even if you believe the snake was nonvenomous, as there is always a risk of infection.