Black snakes often raise questions about their potential danger, as dark coloration can be associated with venom. This article clarifies the distinctions between harmless black-colored snakes and venomous species, along with features to help differentiate them.
Common Non-Venomous Black Snakes
Many snakes that are predominantly black are non-venomous and play an important role in their ecosystems. The Eastern Rat Snake, also known as the Black Rat Snake, is a common example found across eastern North America, growing between 3.5 and 7 feet long. These snakes have shiny black scales on their backs and a lighter-colored belly, often with a white throat and chin. They are constrictors, meaning they subdue their prey by coiling around them, and are frequently seen around buildings where they hunt rodents, amphibians, and young birds. Eastern Rat Snakes are skilled climbers and swimmers, often found in fields, woodlands, and suburban areas.
Another prevalent non-venomous species is the Eastern Racer, which can be black in adult form. These slender, fast-moving snakes typically range from 2 to 4 feet in length. Eastern Racers have smooth scales and a cream to yellow belly without markings. They are diurnal and are known for their speed, often fleeing quickly when approached. Both Eastern Rat Snakes and Eastern Racers are often mistaken for venomous snakes, but they are generally shy and will either freeze or slither away if threatened.
Venomous Snakes That Can Be Dark
While many black snakes are harmless, some venomous species can exhibit very dark or black coloration, which can lead to misidentification. The Cottonmouth, also known as the Water Moccasin, is a heavy-bodied pit viper found in the southeastern United States that can be dark olive-brown to almost black. As they age, their patterns tend to become less visible, making adult Cottonmouths appear uniformly dark. These snakes inhabit wet areas like swamps, lakes, and rivers, and are known for their defensive display of opening their mouth to reveal a white interior, giving them their name.
Copperheads, another type of pit viper common in the eastern and southeastern U.S., typically have a reddish-brown head and hourglass-shaped markings. However, their coloration can vary, with some individuals, especially juveniles, appearing darker gray or almost black, and patterns becoming obscure in very dark adults. Eastern Diamondback Rattlesnakes, the largest venomous snake in North America, usually have a brown, yellowish, or gray ground color with dark diamond patterns, but their background color can range to nearly black. Similarly, Timber Rattlesnakes can also have dark coloration and sometimes have black heads and tails.
Identifying Features for Differentiation
Distinguishing between venomous and non-venomous snakes, especially dark-colored ones, involves observing several physical characteristics. Many venomous snakes in North America, particularly pit vipers, possess a triangular or broad head shape that is distinct from their narrower neck. Conversely, most non-venomous snakes tend to have more rounded or oval heads; however, some non-venomous species can flatten their heads when threatened to mimic a triangular shape.
Another distinguishing feature is pupil shape: pit vipers typically have vertical, cat-like pupils, while most non-venomous snakes have round pupils. An exception to this rule is the venomous Coral Snake, which has round pupils. Pit vipers also possess heat-sensing pits located between their nostril and eye on each side of the head, a feature absent in non-venomous snakes. While helpful, observing this feature requires close proximity, which is not advisable.
Scale patterns can sometimes offer clues, though they are not a universal identifier for venomous versus non-venomous status across all species. Some venomous snakes, like Cottonmouths, Copperheads, and Eastern Diamondback Rattlesnakes, have keeled scales, which have a raised ridge and rough texture. Additionally, the scales on the underside of a venomous snake’s tail often appear in a single row leading to the anal plate, whereas non-venomous snakes typically have a double row of scales. However, this last feature is difficult to observe safely.
Behavioral cues can also provide some indication, but they should not be relied upon solely. Cottonmouths, for instance, often float with their entire body above the water’s surface, unlike many non-venomous water snakes that swim with only their head visible. Rattlesnakes are known for their distinct tail rattle as a warning. However, some non-venomous snakes, such as rat snakes and racers, can vibrate their tails in dry leaves to create a sound similar to a rattle. When encountering any snake, it is safest to observe from a distance and never attempt to handle or provoke it.