Mistaken identity in the natural world can be perilous, especially when a harmless creature evolves to resemble a dangerous one in a process called Batesian mimicry. Several non-venomous snakes have developed physical appearances and behaviors that closely mirror the rattlesnake, a highly venomous pit viper. This evolutionary deception provides protection for the harmless mimic but creates a common identification challenge for humans encountering them. Learning to differentiate between the dangerous model and its imitators is paramount for safety and for protecting the harmless snakes that are often killed out of fear. The differences are often subtle, requiring attention to specific physical characteristics and defensive actions.
Defining Characteristics of Rattlesnakes
Rattlesnakes are classified as pit vipers and are identifiable by several distinct features. The most defining characteristic is the segmented rattle, a keratinous structure at the tail tip that produces a distinctive buzzing sound when vibrated. This warning device is composed of interlocking segments, with a new segment added each time the snake sheds its skin. Rattlesnakes possess a wide, distinctly triangular head, caused by the large venom glands located behind the eyes. They have vertical, slit-like pupils and are equipped with a pair of heat-sensing facial pits located between the eye and the nostril. These pits allow them to detect the infrared heat signature of warm-blooded prey in total darkness.
The Most Common Rattlesnake Mimics
The species most frequently confused with rattlesnakes across North America is the Gopher Snake (Pituophis catenifer). These snakes, including regional subspecies like Bullsnakes or Pine Snakes, share a habitat with rattlesnakes throughout much of the western and central United States. Gopher snakes are large, powerful constrictors that are entirely non-venomous and play a beneficial role in rodent control. Their coloration and patterning are the main sources of confusion, as they often display a background color overlaid with a series of dark blotches. These blotches can resemble the diamond or hexagonal patterns found on many rattlesnake species. Occupying similar arid environments, their earthy tones allow them to blend into the same backgrounds, furthering the visual deception.
Physical Differences Between Real and Fake
The most reliable way to distinguish a true rattlesnake from a mimic involves examining the tail end. A rattlesnake, even a juvenile, will have a tail that ends abruptly in a segmented rattle or at least a single keratin “button” if it has not yet shed its skin. Conversely, the Gopher Snake’s tail is long and slender, tapering to a fine, pointed tip with no specialized sound-producing structure. A second difference is the shape of the head in a relaxed state. Rattlesnakes have a broad, heavy, and distinctly triangular head that is noticeably wider than their neck, accommodating their venom glands. In contrast, the Gopher Snake has a narrower, more rounded head that is only marginally wider than its neck, though it can intentionally flatten this area when threatened. When observed closely, the pupils also offer a clear distinction; rattlesnakes have elliptical, vertical pupils, while Gopher Snakes possess round pupils.
Behavioral Mimicry and Defensive Tactics
Beyond physical appearance, Gopher Snakes employ a remarkable series of defensive actions designed to imitate the rattlesnake’s warning display. When startled, a Gopher Snake will often coil its body into a defensive posture, similar to a rattlesnake preparing to strike. It then takes the visual mimicry further by flattening its head and neck, momentarily distorting its shape to appear more triangular and intimidating. The most convincing form of mimicry is acoustic, where the Gopher Snake vibrates its tail rapidly. Although it lacks a rattle, when the pointed tail tip is thrashed against dry grass, leaves, or other debris, the resulting sound can be surprisingly similar to the authentic buzzing rattle. This behavior is accompanied by a forceful hiss, which can sound like the explosive exhalation of a cornered viper.