The bullsnake (Pituophis catenifer sayi) is a large, non-venomous constrictor snake found across a wide range of North America, particularly in the central and western United States. Its size and bold color patterns often lead to misidentification with venomous species. Understanding the bullsnake’s distinct visual features is necessary for accurate identification. This guide provides a detailed look at the physical characteristics that define the bullsnake.
Overall Size and Muscular Build
Bullsnakes are among the largest native snakes in the United States, exhibiting a robust and muscular physique as adults. They commonly reach an average length of four to six feet, though exceptional specimens have been documented extending over eight feet long. This substantial length and significant girth contribute to the snake’s heavy-bodied form.
The species is notably thick for a non-venomous snake, sometimes weighing between two to three pounds, with larger individuals reaching nearly ten pounds. This bulk is characteristic of a powerful constrictor.
Coloration and Distinctive Blotching Pattern
The base coloration of the bullsnake is highly variable, providing effective camouflage across its wide distribution. The ground color typically ranges from pale straw or yellow to tan or light brown. This light background is prominently marked by a series of dark blotches running along the length of the back.
These dorsal markings are usually dark brown, reddish-brown, or black. Near the head, the blotches are rectangular or square-shaped, becoming more rounded and transitioning into dark bands near the tail. Lighter areas between the main blotches often feature smaller, secondary spots or speckled patterns along the sides.
The underside is generally pale yellow or cream-colored. This pale belly is typically marked with scattered black or dark brown markings, often forming a checkered or mottled pattern. The combination of the light ground color and the bold dorsal blotches creates the visual signature of the species.
Head Shape and Identifying Scale Features
The head of the bullsnake is relatively small and narrow compared to its thick body. The most defining characteristic is the pointed snout, formed by an enlarged rostral scale at the tip of the nose. This specialized, protruding scale is taller than it is wide and functions like a shovel, assisting the bullsnake in its burrowing activities.
The scales covering the bullsnake’s body are heavily keeled, meaning each scale possesses a ridge running down its center. This feature gives the snake a rough, matte texture, unlike the smooth, glossy appearance of many other non-venomous snakes. The snake’s eyes feature round pupils, distinguishing it from the slit pupils of native pit vipers. A dark line or band often extends from the eye toward the jaw, completing the characteristic facial markings.
Differentiating from Venomous Lookalikes
The bullsnake’s color pattern and large size frequently cause confusion with venomous pit vipers, such as rattlesnakes, which share its habitat. The most reliable visual distinction lies at the end of the tail: the bullsnake’s tail tapers smoothly to a point, completely lacking the rattle segments found on an adult rattlesnake. Even juvenile rattlesnakes possess a single button or segment that is absent on the bullsnake.
Pit vipers possess vertical, cat-like pupils and feature a specialized heat-sensing pit located between the eye and the nostril, a structure the bullsnake lacks. The bullsnake also has a narrower head that blends more seamlessly into its neck, contrasting with the distinctively triangular, broad head of most pit vipers.