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, is a nonvenomous
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of
snake Snakes are elongated limbless reptiles of the suborder Serpentes (). Cladistically squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales much like other members of the group. Many species of snakes have s ...
in the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Colubridae Colubridae (, commonly known as colubrids , from , 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest fossil species of the family date back to the Late Eocene epoch, with earlier origins suspected. C ...
. The species is native to central
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
. No
subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...
are recognized as valid. Its color variations include the
Texas rat snake The Texas rat snake (''Pantherophis obsoletus lindheimeri)'' is a subspecies of the black rat snake, a nonvenomous colubrid. It is found in the United States, primarily within the state of Texas, but its range extends into Louisiana, Arkansas and ...
.''Pantherophis obsoletus''
The Reptile Database. www.reptile-database.org.
Along with other snakes of the eastern United States, like the
eastern indigo snake The eastern indigo snake (''Drymarchon couperi'') is a species of large, non-venomous snake in the Family (biology), family Colubridae. Native to the southeastern United States, it is the longest native snake species in the country. Taxonomy ...
(''Drymarchon couperi)'' and the
eastern racer The eastern racer, or North American racer (''Coluber constrictor''), is a species of nonvenomous snake in the Family (biology), family Colubridae. The species is Endemism, endemic to North America and Central America. Eleven subspecies, includin ...
(''Coluber constrictor''), it is called “black snake”.


Geographic range

''P. obsoletus'' is found west of the
Mississippi River The Mississippi River is the main stem, primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri River, Missouri. From its traditional source of Lake Ita ...
, from eastern and southern
Iowa Iowa ( ) is a U.S. state, state in the upper Midwestern United States, Midwestern region of the United States. It borders the Mississippi River to the east and the Missouri River and Big Sioux River to the west; Wisconsin to the northeast, Ill ...
southward through
Missouri Missouri (''see #Etymology and pronunciation, pronunciation'') is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Ranking List of U.S. states and territories by area, 21st in land area, it border ...
and
Arkansas Arkansas ( ) is a landlocked state in the West South Central region of the Southern United States. It borders Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, Texas to the southwest, and Oklahoma ...
to western
Louisiana Louisiana ( ; ; ) is a state in the Deep South and South Central regions of the United States. It borders Texas to the west, Arkansas to the north, and Mississippi to the east. Of the 50 U.S. states, it ranks 31st in area and 25 ...
, westward to eastern
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
, northward through
Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...
and eastern
Kansas Kansas ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named a ...
to southeastern
Nebraska Nebraska ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Ka ...
. Aside from the usual variety that is black or has patches of black on a lighter background, color variations include the
Texas rat snake The Texas rat snake (''Pantherophis obsoletus lindheimeri)'' is a subspecies of the black rat snake, a nonvenomous colubrid. It is found in the United States, primarily within the state of Texas, but its range extends into Louisiana, Arkansas and ...
, 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 Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
''
Pantherophis ''Pantherophis'' is a genus of nonvenomous colubrid snakes endemic to central and eastern regions of North America. It consists of the North American ratsnakes, the fox snake, foxsnakes, and the cornsnakes. The genus, which contains 10 recognize ...
'' 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. 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 Copperhead may refer to: Snakes * ''Agkistrodon contortrix'', or eastern copperhead, a venomous pit viper species found in parts of North America * '' Agkistrodon laticinctus'', or broad-banded copperhead, a pit viper species found in the southe ...
and
timber rattlesnake The timber rattlesnake (''Crotalus horridus''), also known Common name, commonly as the canebrake rattlesnake and the banded rattlesnake,Albert Hazen WWright AH, species:Anna Allen WWright AA (1957). ''Handbook of Snakes of the United States a ...
s. 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 ''P. obsoletus'' can become quite large, with a reported typical total length (including tail) of .Species profile: Minnesota DNR
Dnr.state.mn.us. Retrieved on 2012-12-19.
It is the largest snake found in
Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
. The record total length is , making it (officially) the longest snake in
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
. Unofficially, indigo snakes (genus ''
Drymarchon ''Drymarchon'' is a genus of large non-venomous colubrid snakes, commonly known as indigo snakes or cribos, found in the Southeastern United States, Mexico, Central America, and South America. Description Indigo snakes are large, robust snakes. ...
'') are known to exceed it, and one wild-caught pine snake ('' Pituophis melanoleucus''), with a portion of its tail missing, measured . The body mass of ''P. obsoletus'' 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 ''Pantherophis vulpinus'', Common name, commonly known as the foxsnake or the eastern fox snake,species:Brian I. Crother, Crother BI (editor) (2008). ''Scientific and Standard English Names of Amphibians and Reptiles of North America North of M ...
'', ''
P. ramspotti ''Pantherophis ramspotti'', commonly known as the western fox snake, is a species of rat snake in the family Colubridae. The species is native to the upper Midwestern United States, west of the Mississippi River. It is nonvenomous. Etymology Th ...
'', 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 for ''P. 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. 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) . (''Elaphe obsoleta obsoleta'', pp. 230–234, Figure 72 + Map 24 on p. 235).


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 The American mink (''Neogale vison'') is a semiaquatic species of Mustelidae, mustelid native to North America, though human introduction has expanded its range to many parts of Europe, Asia, and South America. Because of range expansion, the Am ...
, which weighs no more than an adult rat snake) and large
birds of prey Birds of prey or predatory birds, also known as (although not the same as) raptors, are hypercarnivorous bird species that actively predation, hunt and feed on other vertebrates (mainly mammals, reptiles and smaller birds). In addition to speed ...
(especially
red-tailed hawk The red-tailed hawk (''Buteo jamaicensis'') is a bird of prey that breeds throughout most of North America, from the interior of Alaska and northern Canada to as far south as Panama and the West Indies. It is one of the most common members of ...
s).Eastern Ratsnake. ''Pantherophis alleghaniensis''
Natural Heritage Endangered Program. mass.gov
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 Rattlesnakes are venomous snakes that form the genera '' Crotalus'' and ''Sistrurus'' of the subfamily Crotalinae (the pit vipers). All rattlesnakes are vipers. Rattlesnakes are predators that live in a wide array of habitats, hunting small an ...
, it is not a form of
mimicry In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. In the simples ...
, 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. 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. 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 hawk The red-shouldered hawk (''Buteo lineatus'') is a medium-sized buteo. Its breeding range spans eastern North America and along the coast of California and northern to northeastern-central Mexico. It is a permanent resident throughout most of its ...
s, though in many cases, the bird is able to kill the snake or both combatants may even die.


Feeding

''P. obsoletus'' is a constrictor, meaning it squeezes its
prey Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not ki ...
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 A mouse (: mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...
,
vole Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of lo ...
s, and
rat Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include '' Neotoma'' (pack rats), '' Bandicota'' (bandicoo ...
s, 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
snake Snakes are elongated limbless reptiles of the suborder Serpentes (). Cladistically squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales much like other members of the group. Many species of snakes have s ...
s (including both those of its own and other species),
frog A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough ski ...
s,
lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...
s,
mole Mole (or Molé) may refer to: Animals * Mole (animal) or "true mole" * Golden mole, southern African mammals * Marsupial mole Marsupial moles, the Notoryctidae family, are two species of highly specialized marsupial mammals that are found i ...
s,
chipmunk Chipmunks are small, striped rodents of subtribe Tamiina. Chipmunks are found in North America, with the exception of the Siberian chipmunk which is found primarily in Asia. Taxonomy and systematics Chipmunks are classified as four genera: '' ...
s,
squirrel Squirrels are members of the family Sciuridae (), a family that includes small or medium-sized rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrel ...
s, juvenile
rabbit Rabbits are small mammals in the family Leporidae (which also includes the hares), which is in the order Lagomorpha (which also includes pikas). They are familiar throughout the world as a small herbivore, a prey animal, a domesticated ...
s, juvenile
opossum Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 126 species in 18 genera. Opossums originated in South America and entered North A ...
s,
songbird A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 5,00 ...
s, and bird eggs. 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). One snake was observed to consume an entire clutch of
mallard The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa. It has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Arge ...
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 The purple martin (''Progne subis'') is a passerine bird in the swallow family Hirundinidae. It is the largest swallow in North America. Despite its name, the purple martin is not truly purple. The dark blackish-blue feathers have an iridescent ...
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.


Reproduction

In ''P. 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 A hemipenis (: hemipenes) is one of a pair of intromittent organs of male squamates (snakes and lizards). Hemipenes are usually held inverted within the body, and are everted for reproduction via erectile tissue, much like that in the human pe ...
, into the female sex organ, the
cloaca A cloaca ( ), : cloacae ( or ), or vent, is the rear orifice that serves as the only opening for the digestive (rectum), reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles, birds, cartilagin ...
. The mating lasts a few minutes to a few hours. After five weeks, the female lays about 12 to 20
egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...
s, 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 Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
, and placed this species in the genus ''Pantherophis''. In addition, because ''Pantherophis'' is masculine, the
specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...
becomes the masculine ''obsoletus''.''Elaphe obsoleta''
a
The Center for North American Herpetology
Accessed 20 June 2008.
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 these combinations: eastern ratsnake (''Elaphe alleghaniensis'', now ''
Pantherophis alleghaniensis The gray ratsnake or gray rat snake (''Pantherophis alleghaniensis''), also commonly known as the black ratsnake, central ratsnake, chicken snake, midland ratsnake, or pilot black snake, is a species of nonvenomous snake in the genus ''Pantherop ...
''), central ratsnake (''Elaphe spiloides'', now ''
Pantherophis spiloides ''Pantherophis'' is a genus of nonvenomous colubrid snakes endemic to central and eastern regions of North America. It consists of the North American ratsnakes, the foxsnakes, and the cornsnakes. The genus, which contains 10 recognized specie ...
''), 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 ''Taggart'' is a Scottish detective fiction television programme created by Glenn Chandler, who wrote many of the episodes, and made by STV Studios for the ITV network. It originally ran as the miniseries ''Killer'' from 6 until 20 Septe ...
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

The western rat snake is available captive-bred in the United States pet trade, and it has been bred for mutations such as
leucistic Leucism () is a wide variety of conditions that result in partial loss of pigmentation in an animal—causing white, pale, or patchy coloration of the skin, hair, feathers, scales, or cuticles, but not the eyes. It is occasionally spelled ''leu ...
,
albino Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and reddish pink or blue eyes. Individuals with the condition are referred to as albinos. Varied use and interpretation of ...
, 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 James may refer to: People * James (given name) * James (surname) * James (musician), aka Faruq Mahfuz Anam James, (born 1964), Bollywood musician * James, brother of Jesus * King James (disambiguation), various kings named James * Prince ...
(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

*
"Black Snakes": Identification and Ecology
– University of Florida fact sheet
Black Rat Snake
Reptiles and Amphibians of Iowa {{Taxonbar, from=Q998324 Pantherophis Rat snakes Snakes of North America Reptiles of Canada Reptiles of Ontario Fauna of the Eastern United States Reptiles of the United States Reptiles described in 1823 Taxa named by Thomas Say