Pantherophis obsoletus
Pantherophis obsoletus – also known as the western rat snake, black rat snake, pilot black snake, or simply black snake – is a non-venomous species of Colubridae found in central North America. No subspecies are currently recognized. Its color variations include the Texas ratsnake. Along with other snakes of the eastern United States, like the eastern indigo snake ("Drymarchon couperi") or the eastern racer ("Coluber constrictor"), it is called 'black snake'. Geographic range. "Pantherophis 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. Aside from the usual variety that is black or has patches of black on a lighter background, color variations include the Texas rat snake, a brown-to-black variant, often with tinges of orange or red, that can be found in southern Oklahoma, Texas, and Louisiana. Habitat. Rat snakes 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. During winter it hibernates in shared dens, often with copperheads and timber rattlesnakes. This association gave rise to one of its common names, pilot black snake, and the superstition that this nonvenomous species led the venomous ones to the den. Description. Adults of "Pantherophis obsoletus" can become quite large, with a reported typical total length (including tail) of . They are the largest snake found in Canada. The record total length is , 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 . The body mass of this rat snake can range up to in adults, although most adults are on the smaller end of this scale, per herpetology research sites, with weights most commonly between . Juveniles are strongly patterned with brown blotches on a gray background (like miniature fox snakes: "P. gloydi", "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. Common names. Other common names include: black chicken snake, black coluber, chicken snake, mountain black snake, mountain pilot snake, pilot, rat snake, rusty black snake, scaly black snake, cow snake, "schwartze Schlange", sleepy John, and white-throated racer. Behavior. When not fully grown, rat snakes are subject to predation by many animals, including other snakes. Once they attain maturity, they are readily preyed on by mammalian carnivores (including the American mink, which weighs no more  than an adult rat snake) and large birds of prey (especially red-tailed hawks). When startled, they may freeze and wrinkle themselves into a series of kinks. If they feel further threatened, they may flee quickly or tail vibrate (potentially a form of mimicry, which makes them sound like rattlesnakes). They are also capable of producing a foul-smelling musk, which they will release onto predators if picked up. They spread the musk with their tails in hopes of deterring the threat. When cornered or provoked, black snakes are known to stand their ground and can become aggressive. Counterattacks on  large birds of prey, often committed by large snakes in excess of in length, have resulted in violent prolonged struggles. Utilizing its infamous agility and the great strength of its muscular coils, the black rat snake is sometimes able to overwhelm and kill formidable avian predators such as red-tailed hawks, great horned owls and red-shouldered hawks, though in many cases the bird is able to kill the snake and both combatants may even die. Feeding. This species 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 they can no longer circulate blood and die of profound hypotension, before eating them. Though they will often consume mice, voles, and rats, western rat snakes are far from specialists at this kind of prey and will readily consume any small vertebrate they can catch. Other prey opportunistically eaten by this species can include other snakes (including both those of their own and other species), frogs, lizards, 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 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. Several rat snake repelling methods have been offered to those putting up martin houses, but most are mixed in success. Reproduction. 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 , cloaca. The mating lasts a few minutes to a few hours. After five weeks, the female lays about 12 to 20 eggs, which are long by wide. The eggs hatch about 65 to 70 days later in late August to early October. The hatchlings are in total length, and they look like miniature fox snakes. Taxonomy. This species has previously been placed (and is still placed by many) in the genus "Elaphe", as "Elaphe obsoleta". However, Utiger et al. found that "Elaphe" is broadly construed as paraphyletic, and placed this species in the genus "Pantherophis". In addition, because "Pantherophis" is  masculine, the specific epithet becomes the masculine "obsoletus". The split of "Pantherophis" from "Elaphe" has been further confirmed by additional phylogenetic studies. In 2001, Burbrink suggested this species be divided into three species based on geographic patterns of mitochondrial DNA diversity. He assigned new common names and resurrected old scientific names, resulting in the following combinations: eastern ratsnake ("Elaphe alleghaniensis", now "Pantherophis alleghaniensis"), central ratsnake ("Elaphe spiloides", now "Pantherophis spiloides"), and western rat snake ("Elaphe obsoleta", now "Pantherophis obsoletus"). However, these three species are not morphologically distinct and overlap in all examined morphological characters. More recent investigations have indicated "P.  alleghaniensis" and "P. spiloides" interbreed freely in Ontario. In 2008, Collins and Taggart resurrected the genus "Scotophis" for Burbrink's three taxa ("i.e.", "Scotophis alleghaniensis", "Scotophis spiloides", and "Scotophis obsoletus") in response to the findings of Burbrink and Lawson, 2007. The justification for this nomenclatural change has been removed by more recent research. In captivity. Western rat snakes are available captive-bred in the United States pet trade, and they have been bred for mutations such as leucistic, albino, and scaleless. However, they are not as popular as other colubrids such as corn snakes, kingsnakes, milksnakes, and hognose snakes. Opinions  vary on western rat snakes' disposition, but captive-bred individuals are reported to be more docile than their wild counterparts. With appropriate care, this species may be expected to live 15 years in captivity, and possibly more.