Pennsylvania is home to 21 or 22 native snake species inhabiting its varied landscapes. The vast majority of these snakes are harmless and perform a significant function within the state’s natural ecosystems. These animals help regulate populations of rodents and insects, contributing to local ecological balance.
The Wide Variety of Non-Venomous Snakes
The majority of snakes encountered in the Commonwealth are non-venomous, totaling 18 species. Among the most widespread is the Eastern Garter Snake, a slender species recognized by its three distinct longitudinal stripes, which are often yellow or white. Garter snakes are highly adaptable, commonly found in suburban gardens, fields, and woodlands throughout the state.
The Eastern Milk Snake is another commonly encountered species, often mistakenly identified as a venomous copperhead due to its coloration. This snake features a light gray or tan body marked with reddish-brown or brownish blotches outlined in black. A reliable identification feature is the Milk Snake’s belly, which displays a distinct black and white checkerboard pattern.
The Black Rat Snake, also known as the Eastern Rat Snake, is one of Pennsylvania’s largest snakes, sometimes exceeding six feet in length. As a powerful constrictor, this large, typically black snake controls rodent populations around farms and homes. Their climbing ability is noteworthy, as they frequently ascend trees and structures in search of bird nests and rodents.
Northern Water Snakes are frequently spotted near rivers, ponds, and marshes, where they actively hunt fish and amphibians. They are heavy-bodied and often display dark brown or black crossbands, especially when young, which can lead to misidentification as the venomous cottonmouth, a species not native to Pennsylvania. When threatened, the Northern Water Snake will flatten its head and strike defensively, though it is not venomous.
Identifying Pennsylvania’s Venomous Species
Pennsylvania is home to only three venomous species, all of which are pit vipers: the Northern Copperhead, the Timber Rattlesnake, and the Eastern Massasauga. All three share common physical characteristics, including a heat-sensing pit located between the eye and nostril and a vertically elliptical pupil resembling a cat’s eye. Non-venomous snakes lack this facial pit and possess round pupils.
The Northern Copperhead is the most commonly reported venomous snake in the state, identifiable by its copper-colored head and distinctive hourglass-shaped crossbands on a lighter body. These bands are narrowest across the snake’s back and widen on the sides, often described as resembling Hershey’s Kisses. Copperheads remain motionless or retreat when approached, biting only if threatened.
The Timber Rattlesnake is the largest venomous species, known for the segmented rattle on the end of its tail. This snake appears in two color phases: a yellow phase with dark crossbands, and a darker, almost black phase with a velvety appearance. Although they possess a potent venom, Timber Rattlesnakes are non-aggressive and often use their rattle as a warning before striking.
The Eastern Massasauga is the smallest and rarest of the state’s venomous snakes, found only in isolated wetland areas in western Pennsylvania. This species features a gray or tan body with large, dark brown blotches running down the back and smaller blotches along the sides. Its rattle is much smaller and produces a sound often described as a faint buzz, making it less easily heard than the Timber Rattlesnake’s warning.
Geographic Range and Habitat Preferences
The distribution of Pennsylvania’s snakes is closely tied to the state’s diverse topography and ecological zones. Timber Rattlesnakes primarily inhabit the rocky, mountainous ridges and forested areas of the Appalachian regions, utilizing rock crevices for hibernation. The Northern Copperhead also favors rocky hillsides, wooded slopes, and abandoned foundations, showing a wide distribution across the southern two-thirds of the state.
The rare Eastern Massasauga is unique in its habitat preference, residing almost exclusively in the marshy floodplains, bogs, and wet prairies of the western counties. Non-venomous species like the Northern Water Snake and the various Ribbon Snakes are concentrated around the state’s extensive network of lakes, rivers, and streams. Common species such as the Garter Snake and Eastern Milk Snake thrive in varied habitats, including forests, agricultural fields, and suburban backyards.