Snakes often evoke fear due to the potential danger of venomous species. Distinguishing venomous from nonvenomous snakes is important for human safety and reptile conservation. Accurate identification helps prevent harm to both humans and snakes, fostering coexistence.
Key Anatomical Markers
One common characteristic often associated with venomous snakes, particularly pit vipers, is a triangular or spade-shaped head. This shape appears broader than their neck due to venom glands located behind the eyes. Nonvenomous snakes typically have a more rounded head that blends smoothly with their body, though some can flatten their heads when threatened, mimicking a triangular shape.
Another distinguishing feature for many venomous snakes in North America is the shape of their pupils. Most venomous snakes, excluding the coral snake, possess elliptical or slit-like pupils, similar to a cat’s eye, especially in bright light. Conversely, nonvenomous snakes generally have round pupils. This feature, while generally reliable, requires close observation, which can be risky.
Pit vipers, a group of venomous snakes including rattlesnakes, copperheads, and cottonmouths, have specialized heat-sensing pits. These pits are located between their eye and nostril on each side of the head. They allow the snake to detect infrared radiation, or heat, emitted by warm-blooded prey, even in complete darkness. The absence of these visible pits indicates a nonvenomous snake.
Identifying Specific Venomous Species
Beyond general anatomical markers, certain venomous snakes have unique features that aid in their identification. Rattlesnakes are readily recognized by the segmented rattle at the end of their tail, which they use to produce a buzzing sound as a warning. While not all rattlesnakes rattle before striking, this distinctive tail appendage is a reliable indicator.
Coral snakes, unlike pit vipers, have a distinctive banding pattern of red, yellow, and black. A well-known rhyme, “red on yellow, kill a fellow” or “red touches yellow, kills a fellow,” helps distinguish them from nonvenomous mimics like king snakes, which have “red on black, venom lack.” This rhyme applies specifically to coral snakes in the United States and should not be relied upon in other regions due to variations in snake patterns.
Other venomous snakes, such as copperheads and cottonmouths, also exhibit distinguishing patterns and behaviors. Copperheads typically have a copper or reddish-brown coloration with hourglass-shaped markings that are often lighter brown or tan. These hourglass patterns are widest on the sides and narrowest along the spine. Cottonmouths, also known as water moccasins, are often dark-bodied with broad heads and, when threatened, may display the white interior of their mouth, giving them their name. Juvenile cottonmouths often have bright yellow tail tips.
Unreliable Identification Methods
Relying solely on coloration and pattern for snake identification can lead to dangerous errors. Many nonvenomous snakes exhibit patterns and colors similar to venomous species, serving as a form of mimicry. Coloration can also vary significantly even within the same species depending on age, region, and individual variation, making it an inconsistent identifier.
A snake’s size or aggression is not an indicator of its venomous nature. Both large and small snakes can be venomous. Nonvenomous snakes may also exhibit defensive behaviors like striking or flattening their heads if threatened. Assuming a snake is harmless based on these factors can be a misjudgment.
Myths about swimming ability or habitat type also prove unreliable for identification. Many nonvenomous snakes are excellent swimmers, and snakes, both venomous and nonvenomous, can be found in a variety of habitats, including aquatic environments. For example, while cottonmouths are semi-aquatic, nonvenomous water snakes are also commonly found near water.
Bite marks are not a practical method for preemptive identification. While fangs indicate a venomous snake after a bite, relying on this for identification before an incident is unsafe. Bite mark identification is useful for medical treatment, not for avoiding encounters.
Prioritizing Safety
When encountering a snake, prioritize safety and maintain a respectful distance. If a snake’s identity is uncertain, assume it is venomous. This cautious approach minimizes bite risk.
Leaving the snake undisturbed is the best course of action. Most snake bites occur when people attempt to handle or kill snakes. Giving the snake ample space allows it to move away naturally.
If a snake is found in an undesirable location, such as inside a home, contact local animal control, wildlife experts, or professional snake removal services. Do not attempt to remove the snake yourself, as this increases bite risk. Never pick up a snake, even if it appears dead, as they can still strike.