Description: Adults of P. obsoletus can become quite large, with a reported typical total length (including tail) of 3 ft 6 in to 6 feet. It is the largest snake found in Canada. The record total length is 8 ft 5 inches, making it (officially) the longest snake in North America. Unofficially, indigo snakes (genus Drymarchon) are known to exceed it, and one wild-caught pine snake (Pituophis melanoleucus), with a portion of its tail missing, measured 111 inches. The body mass of P. obsoletus can range up to 1.1 to 4.9 lbs. in adults, although most adults are on the smaller end of this scale, per herpetology research sites, with weights most commonly between 1.7 and 2.2 lbs.

Juveniles are strongly patterned with brown blotches on a gray background (like miniature fox snakes: P. ramspotti and P. vulpinus). Darkening occurs rapidly as they grow. Adults are glossy black above with white lips, chin, and throat. Sometimes traces of the "obsolete" juvenile pattern are still discernible in the skin between the scales, especially when stretched after a heavy meal.

Habitat: Rat snakes of the genus Pantherophis are diurnally-active and live in a variety of habitats; some overlap each other. They have adapted to a variety of habitats, including bayou, prairie, and rock outcrops, but they seem to have a particular preference for wooded areas, especially oak trees. Rat snakes are excellent climbers and spend a significant amount of their time in trees. The black rat snake is also a competent swimmer.

Range: P. obsoletus is found west of the Mississippi River, from eastern and southern Iowa southward through Missouri and Arkansas to western Louisiana, westward to eastern Texas, northward through Oklahoma and eastern Kansas to southeastern Nebraska.

Found in these States: AR | IA | KS | LA | MN | MO | NE | OK | TX

Diet: P. obsoletus is a constrictor, meaning it squeezes its prey to the point of cardiovascular collapse due to obstructive shock, coiling around small animals and tightening its grip until the prey can no longer circulate blood and dies of profound hypotension, before being eaten. Though it will often consume mice, voles, and rats, the western rat snake is far from a specialist at this kind of prey and will readily consume any small vertebrate it can catch. Other prey opportunistically eaten by this species can include other snakes (including both those of its own and other species), frogs, lizards, moles, chipmunks, squirrels, juvenile rabbits, juvenile opossums, songbirds, and bird eggs. One snake was observed to consume an entire clutch of mallard eggs. Cavity-nesting bird species are seemingly especially prevalent in this snake's diet. The western rat snake has been noted as perhaps the top predator at purple martin colonies as a single large snake will readily consume a number of eggs, hatchlings, and adults each summer.

Reproduction: In P. obsoletus mating takes place in late May and early June. The male snake wraps its tail around the female with their vents nearly touching. The male then everts one of its sex organs, a hemipenis, into the female sex organ, the cloaca. The mating lasts a few minutes to a few hours. After five weeks, the female lays about 12 to 20 eggs, which are 1.4 to 2.4 inches long by 0.79 to 1.04 inch wide. The eggs hatch about 65 to 70 days later in late August to early October. The hatchlings are 11 to 16 inches in total length, and they look like miniature fox snakes.

Status: Listed as Least Concern in view of its wide distribution, tolerance of a degree of habitat modification, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.

Taxonomy: