Cottonmouths are generally not found in Indiana. While historical records indicate a rare presence, particularly in southwestern Indiana, they are state endangered and likely no longer occur here. The common perception of encountering these venomous snakes often stems from confusion with other aquatic species.
Understanding the Cottonmouth’s Natural Range
The cottonmouth (Agkistrodon piscivorus), also known as the water moccasin, primarily spans the southeastern United States. This includes areas from Virginia to Florida, west to central Texas, and north into southern Illinois. Indiana lies at the northern edge of this range, making their presence exceptional. Cottonmouths are semi-aquatic snakes, preferring wetland environments like swamps, marshes, and slow-moving streams. Their ecological requirements, such as specific climate and habitat, limit their northern expansion.
Commonly Confused Snakes in Indiana
Many Indiana snakes are mistaken for cottonmouths due to their aquatic habits and defensive behaviors. The Northern Watersnake (Nerodia sipedon) is the most common source of misidentification. These non-venomous snakes are widespread in Indiana’s waterways, including ponds, lakes, and streams.
Northern Watersnakes exhibit variable coloration, from pale gray to dark brown with bands that become less distinct in older individuals. When threatened, they may flatten their heads, strike defensively, and release a foul-smelling musk, leading to misidentification. The Eastern Hognose Snake (Heterodon platirhinos) is also confused, known for flattening its head and neck, hissing, and playing dead.
Key Differences for Identification
Distinguishing cottonmouths from species like the Northern Watersnake involves several key features. Cottonmouths have a triangular, broad head distinct from their narrower neck. Northern Watersnakes have a more oval head that blends smoothly into their body, lacking this distinction.
Another indicator is pupil shape. Cottonmouths, as pit vipers, have vertical, cat-like pupils. Northern Watersnakes have round pupils. Cottonmouths also possess heat-sensing facial pits between their eyes and nostrils, a characteristic absent in Northern Watersnakes.
Coloration and pattern also offer clues. Adult cottonmouths are often dark, from olive to black, with banding sometimes fading to a uniform dark appearance. Younger cottonmouths display more vibrant patterns and a yellow or greenish tail tip. Northern Watersnakes exhibit a wide range of colors and patterns, often with bolder bands or blotches.
Behavioral differences are informative. When threatened, a cottonmouth may display its “cotton-white” mouth by opening it wide to reveal the pale interior. While cottonmouths may stand their ground, they often prefer to escape. Northern Watersnakes are more likely to flee but will bite and release musk if cornered. Cottonmouths often swim with their bodies largely on the surface, while watersnakes typically swim with only their heads visible above water.