''Pantherophis obsoletus'', also known
commonly as the western rat snake, black rat snake, pilot black snake, or simply black snake,
[ is a nonvenomous ]species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of snake
Snakes are elongated, Limbless vertebrate, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Ma ...
in the family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
Colubridae
Colubridae (, commonly known as colubrids , from la, coluber, 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest species of the family date back to the Oligocene epoch. Colubrid snakes are found on ever ...
. The species is native to central North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. There are no subspecies
In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...
that are recognized as being 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 an ...
.[''Pantherophis obsoletus''](_blank)
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 Colubridae. Native to the southeastern region of the United States, it is the longest native snake species in North America.
Taxonomy an ...
(''Drymarchon couperi)'' and the eastern racer
The eastern racer (''Coluber constrictor'') is a species of nonvenomous snake in the family Colubridae. The species is endemic to North America and Central America. Eleven subspecies, including the nominotypical subspecies, are recognized, which ...
(''Coluber constrictor''), it is called “black snake”.
Geographic range
''P. obsoletus'' is found west of the Mississippi River
The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it f ...
, from eastern and southern Iowa
Iowa () is a state in the Midwestern region of the United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wisconsin to the northeast, Illinois to the ...
southward through Missouri
Missouri 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 is bordered by eight states (tied for the most with Tennessee ...
and Arkansas
Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the Osage ...
to western Louisiana
Louisiana , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is borde ...
, westward to eastern Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
, northward through Oklahoma
Oklahoma (; Choctaw language, Choctaw: ; chr, ᎣᎧᎳᎰᎹ, ''Okalahoma'' ) is a U.S. state, state in the South Central United States, South Central region of the United States, bordered by Texas on the south and west, Kansas on the nor ...
and eastern Kansas
Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the ...
to southeastern Nebraska
Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the southwe ...
.
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 an ...
, 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 ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
''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 foxsnakes, and the cornsnakes. The genus, which contains 10 recognized spec ...
'' 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 rattlesnake
The timber rattlesnake, canebrake rattlesnake, or banded rattlesnake (''Crotalus horridus'') Wright AH, Wright AA (1957). ''Handbook of Snakes of the United States and Canada''. Ithaca and London: Comstock Publishing Associates, a division of ...
s. 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 ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
. The record total length is , making it (officially) the longest snake in North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
.[ Unofficially, indigo snakes (genus '']Drymarchon
''Drymarchon'' is a genus of large nonvenomous colubrid snakes, commonly known as indigo snakes or cribos, found in the Southeastern United States, Central America, and South America. Reaching or more in length, they are among the world's larges ...
'') are known to exceed it, and one wild-caught pine snake (''Pituophis melanoleucus
''Pituophis melanoleucus'', commonly known as the pine snake, is a species of nonvenomous snake in the family Colubridae. The species is endemic to the southeastern United States. Three subspecies are currently recognized as being valid.
Taxon ...
''), 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'', '' 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 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, ''schwartze Schlange'', 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 mustelid native to North America, though human intervention has expanded its range to many parts of Europe, Asia and South America. Because of range expansion, the American mink i ...
, which weighs no more than an adult rat snake) and large birds of prey
Birds of prey or predatory birds, also known as raptors, are hypercarnivorous bird species that actively hunt and feed on other vertebrates (mainly mammals, reptiles and other smaller birds). In addition to speed and strength, these predators ...
(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 with ...
s).[Eastern Ratsnake. ''Pantherophis alleghaniensis''](_blank)
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 (potentially 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. Often, mimicry f ...
, which makes them sound like rattlesnake
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 anim ...
s). 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 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 with ...
s, great horned owl
The great horned owl (''Bubo virginianus''), also known as the tiger owl (originally derived from early naturalists' description as the "winged tiger" or "tiger of the air"), or the hoot owl, is a large owl native to the Americas. It is an extrem ...
s 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 and both combatants may even die.
Feeding
''P. obsoletus'' is a constrictor, meaning it squeezes its prey
Predation is a biological interaction where 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 kill the ...
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
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 low-c ...
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'' (bandicoot ...
s, 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 snake
Snakes are elongated, Limbless vertebrate, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Ma ...
s (including both those of its own and other species), frog
A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...
s, lizard
Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...
s, mole
Mole (or Molé) may refer to:
Animals
* Mole (animal) or "true mole", mammals in the family Talpidae, found in Eurasia and North America
* Golden moles, southern African mammals in the family Chrysochloridae, similar to but unrelated to Talpida ...
s, chipmunk
Chipmunks are small, striped rodents of the family Sciuridae. Chipmunks are found in North America, with the exception of the Siberian chipmunk which is found primarily in Asia.
Taxonomy and systematics
Chipmunks may be classified either as ...
s, squirrel
Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrels. Squ ...
s, juvenile rabbit
Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (which also contains the hares) of the order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' includes the European rabbit speci ...
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 93 species in 18 genera. Opossums originated in South America and entered North ...
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 500 ...
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, and 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 s ...
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
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
A hemipenis (plural hemipenes) is one of a pair of intromittent organs of male squamates (snakes, lizards and worm lizards). Hemipenes are usually held inverted within the body, and are everted for reproduction via erectile tissue, much like tha ...
, into the female sex organ, the cloaca
In animal anatomy, a cloaca ( ), plural cloacae ( or ), is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles and birds, a ...
. 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 a ...
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
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...
, and placed this species in the genus ''Pantherophis''. In addition, because ''Pantherophis'' is masculine, the specific epithet
In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...
becomes the masculine ''obsoletus''.[''Elaphe obsoleta''](_blank)
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 the following combinations: eastern ratsnake (''Elaphe alleghaniensis'', now ''Pantherophis alleghaniensis
''Pantherophis alleghaniensis'', commonly called the eastern rat snake, is a species of nonvenomous snake in the family Colubridae. The species is endemic to North America.
Common names
Additional common names for ''P. alleghaniensis'' incl ...
''), central ratsnake (''Elaphe spiloides'', now ''Pantherophis spiloides
The gray ratsnake or gray rat snake (''Pantherophis spiloides''), also commonly known as the central ratsnake, chicken snake, midland ratsnake, or pilot black snake, is a species of nonvenomous snake in the genus '' Pantherophis'' in the subfami ...
''), 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 September 19 ...
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 the 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 ' ...
, albino
Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and pink or blue eyes. Individuals with the condition are referred to as albino.
Varied use and interpretation of the term ...
, 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 is a common English language surname and given name:
*James (name), the typically masculine first name James
* James (surname), various people with the last name James
James or James City may also refer to:
People
* King James (disambiguat ...
(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
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