The Water Moccasin, or Cottonmouth (Agkistrodon piscivorus), is a semi-aquatic pit viper found throughout the wetlands and waterways of the southeastern United States. This venomous snake often generates fear due to its reputation for aggression. Understanding the true nature of this reptile, particularly its defensive actions, is crucial for safely coexisting within its natural habitat. Many popular misconceptions about this snake stem from misinterpretations of its defensive displays.
The Myth of Aggressive Pursuit
The persistent story that the Water Moccasin will aggressively pursue or “chase” a person is not supported by scientific observation. Like nearly all snake species, the Cottonmouth is fundamentally non-confrontational and primarily concerned with self-preservation. Its instinctual response to a perceived threat is to escape and retreat into the nearest available cover, which often means moving toward the water.
Any instance where a snake appears to be moving toward a person is usually a misinterpretation of its flight path. If a person is inadvertently blocking the snake’s intended route to safety, such as a log pile or water’s edge, the snake may move in that direction, creating the illusion of a chase.
When cornered or unable to retreat, the Cottonmouth will adopt a highly visible defensive posture as a last resort. This display includes coiling its body and opening its mouth wide to expose the stark, white interior, which gives the snake its common name. This gaping behavior is a clear warning signal meant to deter a threat without expending venom, which is biologically costly to produce. Field studies confirm that Cottonmouths prefer intimidation over confrontation; true aggression, defined as unprovoked, intentional pursuit, is not a behavior exhibited by this species.
Distinguishing the Cottonmouth
A major contributing factor to the fear and aggressive reputation of the Cottonmouth is its frequent misidentification with harmless water snakes, particularly the Northern Water Snake (Nerodia sipedon). The Cottonmouth possesses several distinct physical characteristics that help differentiate it from non-venomous species. As a pit viper, it has a heavy, stout body and a noticeably triangular-shaped head, which is broad at the base due to the venom glands located behind the eyes.
The snake also features a prominent brow ridge, or supraocular scale, above each eye, which partially overhangs the eye and gives the snake a somewhat obscured appearance. Cottonmouths have vertical, elliptical pupils, similar to a cat’s eye, and possess a heat-sensing pit located between the eye and the nostril.
When swimming, the Cottonmouth holds its entire body largely afloat on the surface of the water. Non-venomous water snakes swim with only their head and a small portion of their back exposed.
Safe Procedures During an Encounter
Encountering a Cottonmouth requires maintaining distance and awareness of its natural defensive space. If you see one, the most important action is to remain calm and slowly increase the distance between yourself and the snake. A minimum of six feet of distance is generally recommended for safety.
Never attempt to harass, capture, or move the snake, even if it is in an inconvenient location, as this is when defensive strikes are most likely to occur. Be especially careful when stepping over logs, lifting debris, or moving through dense vegetation near water, as these are common basking or hiding spots.
Wearing thick, high boots in wetland areas offers a layer of protection against accidental bites. If a bite does occur, immediately call emergency services and keep the affected limb immobilized and below the level of the heart to help slow the spread of venom until medical aid arrives.