Pantherophis obsoletus
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Pantherophis obsoletus, also known commonly as the western rat snake, black rat snake, pilot black snake, or simply black snake,<ref name=b1/> is a nonvenomous species of snake in the family Colubridae. The species is native to central North America west of the Mississippi River. No subspecies are recognized as being valid.<ref name="ITIS">{{#if:174177 | {{#invoke:template wrapper|wrap|_template=cite web|_exclude=id,ID,taxon
| url = https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=174177 | title = Elaphe obsoleta | publisher = Integrated Taxonomic Information System }}
| Template:Citation error }}</ref> Its color variations include the Texas rat snake.<ref name="RDB">Pantherophis obsoletus, The Reptile Database. www.reptile-database.org.</ref> Along with other snakes of the eastern United States, like the eastern indigo snake (Drymarchon couperi) and 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.<ref>Powell R, Conant R, Collins JT (2016). Peterson Field Guide to Reptiles and Amphibians of Eastern and Central North America, Fourth Edition. Boston and New York: Houghton Mifflin Harcourt. xiv + 494 pp. Template:ISBN. (Pantherophis obsoletus, p. 388 + Figure 161 on p. 334 + Plate 36 on p. 335 + Map on p. 385 + Figure 180 on p. 386).</ref>
Aside from the usual variety that is black or has patches of black on a lighter background, color variations include the Texas rat snake, which is 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 of the genus Pantherophis are primarily 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. They can also adjust their waking schedules in different habitats and exhibit facultative nocturnal behaviors.<ref>DeGregorio, Brett A., Jinelle H. Sperry, Daniel P. Valente, and Patrick J. Weatherhead. 2014. "Facultative Nocturnal Behaviour in Snakes: Experimental Examination of Why and How with Ratsnakes ( Elaphe Obsoleta) and Racers ( Coluber Constrictor)." Canadian Journal of Zoology 92 (3): 229–37. doi:10.1139/cjz-2013-0255.</ref> These 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, they hibernate in shared dens, often with copperheads and timber rattlesnakes. When found in homes, they are often in groups. 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 Template:Convert.<ref>Eastern Ratsnake Template:Webarchive, Herps of Texas</ref><ref name=DNR>Species profile: Minnesota DNR. Dnr.state.mn.us. Retrieved on 2012-12-19.</ref> It is the largest snake found in Canada. The record total length is Template:Convert,<ref>Conant R, Bridges W (1939). What Snake Is That? A Field Guide to the Snakes of the United States East of the Rocky Mountains. (with 108 drawings by Edmond Malnate). New York and London: D. Appleton-Century. Frontispiece map + viii + 163 pp. + Plates A–C, 1–32. (Elaphe obsoleta obsoleta, pp. 56–58 + Plate 8, Figure 23).</ref> making it (officially) the longest snake in North America.<ref name=DNR/> 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 Template:Convert.Template:Citation needed The body mass of P. obsoletus can range up to Template:Convert in adults, although most adults are on the smaller end of this scale, per herpetology research sites, with weights most commonly between Template:Convert.<ref>Found in Gaston county NC 8-21-19 species over 14' in length. Pantherophis obsoletus obsoletus (Say, 1823). Reptilia.forumpro.fr. Retrieved on 2012-12-19.</ref><ref>Black Rat Snake Info Template:Webarchive. Qrg.northwestern.edu. Retrieved on 2012-12-19.</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
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.<ref name=b2/><ref>Conant R (1975). A Field Guide to Reptiles and Amphibians of Eastern and Central North America, Second Edition. Boston: Houghton Mifflin. xviii + 429 pp. + Plates 1–48. Template:ISBN (paperback). (Elaphe obsoleta obsoleta, pp. 193–194 + Plate 28 + Map 149).</ref>
Common names
Other common names for Pantherophis obsoletus include gray rat snake, black chicken snake, black coluber, chicken snake, mountain black snake, mountain pilot snake, pilot, rat snake, rusty black snake, scaly black snake, cow snake, sleepy John, and white-throated racer.<ref name=b1>Wright AH, Wright AA (1957). Handbook of Snakes of the United States and Canada. Ithaca and London: Comstock. 1,105 pp. (in 2 volumes) (Seventh printing, 1985) Template:ISBN. (Elaphe obsoleta obsoleta, pp. 230–234, Figure 72 + Map 24 on p. 235).</ref>
Behavior
When not fully grown, rat snakes of the genus Pantherophis 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).<ref name="mass">Eastern Ratsnake. Pantherophis alleghaniensis. Natural Heritage Endangered Program. mass.gov</ref> 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; although this act of tail vibration is indeed a behavior that rat snakes share with rattlesnakes, it is not a form of mimicry, as researchers have observed that snakes have used this method of tail vibration as a defense mechanism against predation long before the emergence of rattlesnakes.<ref>Template:Cite journal</ref> 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.<ref>Fact Sheet at Smithsonian National Zoological Park Website Typically when found in homes, found in groups Template:Webarchive. Nationalzoo.si.edu. Retrieved on 2012-12-19.</ref> When cornered or provoked, rat 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 Template:Convert in length, have resulted in violent, prolonged struggles. Using 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 or both combatants may even die.<ref>Bent AC (1937). Life Histories of North American Birds of Prey. Part 1. Smithsonian Institution U.S. National Museum Bulletin, no. 167.</ref><ref>Bent AC (1938). Life Histories of North American Birds of Prey. Part 2. Smithsonian Institution U.S. National Museum Bulletin, no. 170.</ref>
Feeding
Pantherophis 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 often consumes mice, voles, and rats, the western rat snake is far from a specialist at this kind of prey, and readily consumes 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.<ref name=b2>Schmidt KP, Davis DD (1941). Field Book of Snakes of the United States and Canada. New York: G.P. Putnam's Sons. xiii + 365 pp. (Elaphe obsoleta obsoleta, pp. 148–150, Figure 40 + Plate 16, center, on p. 336).</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> One snake was observed to consume an entire clutch of mallard eggs.<ref name="mass"/> 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 can easily 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.<ref>Rat Snakes Template:Webarchive. Purplemartin.org. Retrieved on 2012-12-19.</ref>
Reproduction
In Pantherophis obsoletus, mating takes place in late May and early June. The male snake wraps his tail around the female with their vents nearly touching. The male then everts one of his 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 Template:Convert long by Template:Convert wide. The eggs hatch about 65 to 70 days later in late August to early October.<ref>Black snake profile at Smithsonian National Zoological Park website Template:Webarchive. Nationalzoo.si.edu. Retrieved on 2012-12-19.</ref> The hatchlings are Template:Convert in total length,<ref name=b1/> and they look like miniature fox snakes.<ref name=b2/>
Taxonomy
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The species Pantherophis obsoletus 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.<ref>Template:Cite journal</ref> In addition, because Pantherophis is masculine, the specific epithet becomes the masculine obsoletus.<ref name="CNAH">Elaphe obsoleta Template:Webarchive at The Center for North American Herpetology. Accessed 20 June 2008.</ref> The split of Pantherophis from Elaphe has been further confirmed by additional phylogenetic studies.<ref name="autogenerated2007">Template:Cite journal</ref><ref name="autogenerated1">Template:Cite journal</ref>
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 these 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.<ref>Template:Cite journal</ref> More recent investigations have indicated P. alleghaniensis and P. spiloides interbreed freely in Ontario.<ref>Template:Cite journal</ref>
In 2008, Collins and Taggart<ref>Template:Cite journal</ref> 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.<ref name="autogenerated2007"/> The justification for this nomenclatural change has been removed by more recent research.<ref name="autogenerated1"/>
In captivity
The western rat snake is available captive-bred in the United States pet trade, and it has been bred for mutations such as leucistic, albino, and scaleless. However, it is not as popular as other colubrids such as corn snakes, kingsnakes, milksnakes, and hognose snakes. Opinions vary on the western rat snake's 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.
References
Further reading
- Say T (1823). In: James E (1823). Account of an Expedition from Pittsburgh to the Rocky Mountains, Performed in the Years 1819 and '20, by Order of the Hon. J.C. Calhoun, Sec'y of War: Under the Command of Major Stephen H. Long. From the Notes of Major Long, Mr. T. Say, and other Gentlemen of the Exploring Party. Vol. I. Philadelphia: H.C. Carey and I. Lea. 503 pp. (Coluber obsoletus, new species, p. 140).
External links
- Template:NRDB species
- "Black Snakes": Identification and Ecology – University of Florida fact sheet
- Black Rat Snake, Reptiles and Amphibians of Iowa