The western ratsnake (Pantherophis obsoletus), also called black rat snake, pilot black snake, or simply black snake, is a nonvenomous colubrid species found in North America.
The black rat snake is found throughout the eastern and central United States. In Canada, it is found in southern Ontario. It is found in the northeast United States, in particular New Jersey (northern), New York (eastern), and Vermont (southern).
It prefers heavily wooded areas and is known for having excellent climbing ability, including the ability to climb the trunk of large mature trees without the aid of branches. The black rat snake is a competent swimmer, but usually uses this ability only to travel to additional hunting territory. During winter, it hibernates in dens, often with copperheads and timber rattlesnakes. This association gave rise to the common name, pilot black snake, and the superstition that this nonvenomous species led the venomous ones to the den.
Adults can become quite large and are known to reach up to eight feet, being the largest snake found in Canada. The record length is 101 inches (2.6 m), making it (officially) the longest snake in North America. Unofficially, indigo snakes (Drymarchon couperi) are known to exceed them, and one wild-caught pine snake (Pituophis melanoleucus), with a portion of its tail missing, measured 111 inches (2.8 m).
This species is a constrictor, meaning it suffocates its prey, coiling around small animals and tightening its grip until they can no longer draw breath, before eating them. Though they do consume mice and rats, black rat snakes will also hunt other snakes, frogs, lizards, chipmunks, squirrels, juvenile rabbits, juvenile opossums, song birds, and bird eggs. 