Western Ratsnake

Media
Photo of a western ratsnake curled up in grasses under a fence.
Scientific Name
Pantherophis obsoletus
Family
Colubridae (nonvenomous snakes) in the order Squamata (lizards and snakes)
Description

Often called the "black snake," the western ratsnake is one of our state's largest and most familiar snakes. Generally shiny black, but some individuals show dark brown blotches. The skin between the scales along the sides may be red. The upper lip, chin, and lower part of the neck are usually white. The belly is white, mottled with gray, or it may be checkered with black. Young are light gray or tan, with distinct dark brown or black blotches on the back and sides; a black band passes between the eyes and angles down toward the mouth. After a year or two of growth, the color normally changes to a more uniform black.

Similar species: The closely related gray ratsnake (P. spiloides) occurs in southeast Missouri and hybridizes with the western ratsnake there. The gray ratsnake's adult coloration resembles the juvenile pattern of western ratsnakes: gray with dark blotches on back and sides, with a dark band passing through the eyes and angling down toward the mouth.

Common Name Synonyms
Black Snake
Black Rat Snake
Black Ratsnake
Texas Ratsnake
Size

Length: 42 to 72 inches (3½ to 6 feet).

Where To Find
Western Ratsnake Distribution Map

Statewide. It may intergrade (hybridize) with the gray ratsnake (Pantherophis spiloides) in the southeastern corner. There is some evidence that this species is being replaced by the gray ratsnake in our Bootheel counties.

Western ratsnakes live in a wide variety of habitats: rocky, wooded hillsides, wooded areas along streams and rivers (especially in former prairie and savanna areas of the state), and in or near farm buildings. They take shelter in brushpiles, hollow trees, farm buildings, and old houses where mice are plenty. They are excellent climbers and often bask in trees. They overwinter in mammal burrows, rock outcrops, old rock quarries, and other places, including rotted stumps or root systems of dead trees.

Western ratsnakes eat a variety of rodents, small rabbits, bats, bird eggs, small birds, and, on occasion, lizards. Prey is killed by constriction. They are excellent climbers and often climb trees to raid bird nests (including bluebird boxes) for eggs and young. Young western ratsnakes eat frogs, lizards, and insects.

Common. This species was long known as the black rat snake, and many know it simply as "black snake." Recent research has led scientists to reclassify this species in relation to its relatives, so its name has changed accordingly. Herpetologists, like ornithologists, carefully apply common names that correspond exactly to the scientific names. When scientific names change, the common names usually change, too.

Life Cycle

This species is active in early April through early November. In spring, early summer, and autumn, they hunt in the daytime; in hot weather, they are nocturnal. Courtship and mating is usually in spring but also occurs in summer and fall. Eggs, usually 6–30, are laid in June or early July in rotten stumps or logs, sawdust piles, or under rocks. Eggs hatch in autumn.

Only someone who has dealt with a mouse or rat problem can truly appreciate this natural, nonvenomous hunter of rodents. These snakes reduce damage to crops and stored grain by rodents without the use of deadly poisons. This far outweighs the occasional theft of a few hens' eggs or baby chickens.

As a predator, this snake helps keep populations of other animals, especially rodents, in check. Although it can defend itself by trying to bite, by vibrating its tail ominously, and by smearing a stinky musk on attackers, this snake often becomes food for hawks and other predators.

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About Reptiles and Amphibians in Missouri
Missouri’s herptiles comprise 43 amphibians and 75 reptiles. Amphibians, including salamanders, toads, and frogs, are vertebrate animals that spend at least part of their life cycle in water. They usually have moist skin, lack scales or claws, and are ectothermal (cold-blooded), so they do not produce their own body heat the way birds and mammals do. Reptiles, including turtles, lizards, and snakes, are also vertebrates, and most are ectothermal, but unlike amphibians, reptiles have dry skin with scales, the ones with legs have claws, and they do not have to live part of their lives in water.