Black Ratsnake

Elaphe obsoleta obsoleta

Common Names: Alleghany black snake; black chicken snake; black Coluber; black pilot snake; black rat snake; black racer; black snake, blue racer; chicken snake; mountain black snake; mountain pilot snake; pilot; racer; rat snake; rusty black snake; rusty black snake; scaly black snake; Schwartze schlange; sleepy John; white-throated racer.

Table of Contents

A Monograph of the Colubrid Snakes of the Genus Elaphe Fitzinger, Klaus-Dieter Schultz (with contributions by Andre Entzeroth), Koeltz Scientific Books, Czech Republic, 1996.

Taxonomic History

Coluber obsoletus Say (in James), 1823: 140.
Coluber alleghaniesis Holbrook, 1842: 111, Pl. 20-Type locality: Summit of Blue Ridge in Virginia and highlands of the Hudson.
Scotophis alleghaniensis Baird & Girard, 1853: 73. Scotophis confinis Baird & Girard, 1853:76-Type locality: Anderson, South Carolina.
Scotophis laetus Baird & Girard, 1853:77-Type locality: "Red River", Arkansas (fide Dowling 1951b).
Elaphis holbrookii Dumeril, Bibron & Dumeril, 1854: 272-Type locality: Charlestown, Indiana.
Elaphis alleghaniensis, Jan & Sordelli, 1867: 4, Liv. 24, Pl. 2 (err).
Coluber obsoletus obsoletus, Yarrow, 1882: 102 (partimlocalities: Pennsylvania, Kansas, Missouri, Georgia, Illinois, North Carolina, Maryland, Indiana and Virginia).
Elaphis obsoletus, Garman, 1883: 54.
Elaphis obsoletus var. alleghaniensis, Garman, 1883: 54.
Elaphis obsoletus var. obsoletus, Garman, H., 1892: 292.
Elaphis obsoletus var. lindheimeri, Garman, H., 1892: 290.
Pantherophis alleghaniensis, Garman, S., 1892:108.
Coluber confinis, Cope, 1892: 632.
Elaphe obsoletus, Dunn, 1915: 6.
Callopeltis obsoletus, Medsger, 1919: 28.
Elaphe obsoleta obsoleta, Stejneger & Barbour, 1923: 91.
Elaphe obsoleta, Neill, 1947: 207.

These references can be found in:
A Monograph of the Colubrid Snakes of the Genus Elaphe .Fitzinger, Klaus-Dieter Schultz (with contributions by Andre Entzeroth), Koeltz Scientific Books, Czech Republic, 1996.

Type Locality

"On the Missouri River from the vicinity of Isla au Vache (Cow Island) to Council Bluff". Restricted to the vicinity of Cow Island, near Leavenworth, Leavenworth County, Kansas (Dowling 1951a).
No data exists on the presence of the holotype.


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Species Description

The longest recorded Elaphe obsoleta obsoleta specimen was 256 cm(Ernst & Barbour 1989), though normal specimens range from 120-160 cm. "The elongate head of moderate size is only slightly set off from the neck. The snout is rounded and is two to two and a half times as long as the eye diameter. The ventral keels are well developed. Laterally, the snake is slightly compressed which leads to a cross section which is a little higher than wide. Adult E. obsoleta are highly variable with regard to their colouration and pattern.
Scutellation-Two, very rarely 3 postoculars; 2+3 or 2+4 temporals; 1 preocular; 8, more rarely 7 or 9 supralabials, of which the 4th and 5th touch the eye; 10 to 13, rarely 9 or 14 infralabials; lateral rows of dorsals smooth, vertebral rows keeled; the scale formula is highly variable: 27-25-27-25-23-21-19-25-23-25-23-21-19-17, or 27-25-27-29-27-25-23-21-19; anal plate divided. Elaphe obsoleta obsoleta is, in contrast to common belief, not always a uniformly black snake, instead it is highly variable regarding colouration and pattern. The dorsal ground colour of adult speimens may be dark brown to glossy deep black. The interstitial skin often has white, yellow, or even reddish areas, which are partially or fairly easily visible. Many adult specimens, even from northern populations, still hae remains of the juvenile pattern which, due to their dark areas, are recognisable as 28 to 39 large saddle blotches and smaller lateral blotches. Other individuals may appear uniform glossy black, without any indications of a lighter interstitial skin between the dorsal scales. The top of the head is always dark brown or black, even in specimens with a partially visible dorsal pattern. The supralabials, the underside of the head and throat region are usually distinctly set off in white. Some specimens may have an indistinct dark postocular stripe. The venter(sic) is white to cream and marked with grey, brown or black indistinct marks or, clearly defined rectangular blotches in a chessboard pattern. In very dark individuals these blotches may become more dense towards the mid-body and the posterior third of the ventral surface may eventually be uniformly black, that of the iris dark grey to almost black. in contrast, juveniles have a light grey ground colour with the back, and the tail being marked with dark brown saddle blotches bordered with black. Smaller and oval lateral blotches of corresponding colour form the pattern on the flanks. Th eneck is patterned with two dark brown bands, which are connected to the first saddle blotch. The top of the head is greyish and speckled with small irreglarly arranged black streaks and dots. The prefrontals are crossed by a dark brown to black band, which continues as postocular stripe behind the eyes and ends at the angles of the mouth. The iris is light grey. With increasing growth the dorsal colouration darkens and eventually obliterates the blotched pattern. The time at which the colour change is finalised varies with the individual. Some specimens may have been dark at a total length of 70 cm. Albinos have occasionally been recorded in the wild. Distinctive characteristics: black or blackish brown, bery large, angulate bellied (arboreal) snakes. If spots are present they are more or less indistinct and indistinctly outlined with white. Interspaces between the faintly keeled scales are white. Posterior belly slate gray; throat, chin, and labials white."

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Elaphe obsoleta obsoleta is found throughout the eastern half of the United States and a small area of Canada (see Range Map.) Due to problematic nomenclature, it is extremely difficult to precisely define the borders of the E. o. obsoleta range. "In the northwest it occurs along the Mississippi approximately to the area of Lake Pepin in Minnesota. The northernmost population of the United States occur on the central eastern shore of Laake Michigan. The regions surrounding lower Lake Champlain in Vermont and the extreme southwest of Rhode Island represent the northeastern borders of the range. The eastern border is formed by the east-coast of the United States up to te area of the Albemarle Sound in North Carolina. From there, the eastern range limit reaches slightly into the hinterland and then southwards along the eastern buttresses of the Appalachian Mountains to the central parts of Georgia. The southern border crosses the Cumberland Plateau from Georgia and extends aloing the Tennessee and Wabash Valley in Indiana, E. o. obsoleta intrudes to the south over the Ozark Plateau and through the areas west of the Mississippi. The Red River eventually represents the southeastern distribution limit of the uninterrupted range. The westernmost records were made in central Kansas, southeastern Nebraska and southern Iowa."

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Reproductive Behavior

Wild Elaphe obsoleta obsoleta reach maturity in the fourth year of life "when the males measure just under 90 cm in total length. Eggs are laid in the period from late May to August with the juveniles hatching in July to September. Clutches found in the wild usually contain 10 to 20 eggs, although those of 30 or even 44 eggs have on occasion been recorded. Collective laying sites are not unusual for this species. Communal cluthes have been found. During the mating season vigorous combat can be observed amongst the males. The rivals encompass one another each trying to press their opponents head to the ground, they do not hesitate to bite each other. During the actual courtship activities the female is held by the male with a mating bite. Depending on the date of mating, the 5 to 20 eggs are laid after a gestation period of 60 to 80 days in June or July. Larger clutches of 25 to 30 eggs are not unusual. Mor of an exception is the production of two clutches in one year. At an incubation temperature of 25 to 29 degrees celsius, the juveniles hatch after 50 to 76 days. the hatchlings measure 30-45 cm, and are vigorous and good feeders."

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Feeding Mechanism and Diet

Elaphe obsoleta is normally a slow moving snake and when encountered in the open field, it often 'freezes', drawing up the body into a series of kinks. When alarmed, it sometimes surprises its adversary in a dramatic defensive response. This behaivor is often referred to as being remarkably aggressive… Elaphe obsoleta is an excellent swimmer and often tries to escape into a nearby water where it can dive to avoid a potential predator. Furthermore, it may remain submerged for more than an hour. The perfered diet of adult Elaphe obsoleta are warm blooded prey such as mice, rats and birds. The entire prey spectrum however includes small rabbits, squirrels, prairie dogs, woodchucks, weasels, young opossums, bird eggs, lizards, frogs and invertebrates. It has also been known to eat lizard eggs, other snakes, and bats.
Ratsnakes have been known to feed with preferance for local prey. In experiments, snakes that were fed mice over an eight-month period showed enhanced responses to rat odors and dimished responses to those of domestic chickens.

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Lifestyle (micro and macro habitat)

Elaphe obsoleta obsoleta is a typical species of montane and lowland deciduous forested areas, particularly the rocky hillsides of open woodlands, with a vertical distribution range from sea-level to 1200 m. It often frequents the moist oak and oak hickory wooded areas near streams, rivers or lakes, as well the xeric pine uplands (Fitch, 1963). Weatherhead and Charland (1985) remarked that particularly during the bird breeding season, E. o. obsoleta has a preference for fields or the ecotone between fields and deciduous forests... All subspecies of E. obsoleta are mainly diurnal with activity peaks in the early morning and the late afternoon. During the warmer periods of the year they will change their main activity to the evening hours. It is frequently called the most arboreal of our northeastern snakes. Some 25 or more writers mention this habit. Twenty-four or more ascribe it to trees. Its climbing ability is recorded about barns, houses, granaries, schoolhouses, farm yards. It climbs to high places- an attic, a bat roost, cupola of a barn, top of a 30 ft grapevine, very highest point in cage, high in trees. On the ground it is under rocks, under decaying logs, in ledges, in hollow logs, on fallen logs, along fence rows, in stumps, in dry stone stream beds, in fallen saplings, or in fallen logs. Several have ascribed it to hilly, rocky, or scrubby mountainous sections. Many place it in woods, oak-hickory woods, heavy oak woods, moist woodlands, heavest forests, bottomland forests. The snakes usually hibernate from October or November to March or April. Preferred hibernacula are deep caves, stone quarries, hollow tree trunks or old abandoned building. Hibernation aggregations are frequently formed often with the presence of snakes of other genera being tolerated. (length increases with northern geography; species in florida are active year round.)

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Conservation Information

This species is common in Connecticut, and is not included in a list of endangered or threatened species by the Connecticut Department of Environmental Protection ( )

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Range Map

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Griswold, B. & J. G. Walls (1994):Rat Snakes. -Reptile Amphibian Magazine, Pottsville, (6).

Klemens, M. W. (1983: Geographic distribution: Elaphe obsoleta obsoleta(Black Rat Snake). -Herpetology Review, Athens, 14.

Landreth, H. F. (1972):Physiological responses of Elaphe obsoleta and Pituophis melanoleucus to lowered ambient temperatures. -Herpetologica, Lawrence, 28.

Langhammer, J. (1961): The vocal pouch: Report about Elaphe obsoleta. -Bull. Philad. Herp. Soc., 10(4).

Lieb, C. S. (1971): A study of the variation in Elaphe obsoleta of Texas. -Texas Acad. Sci. Coll., 26(1).

Lillywhite, H. B. & R. A. Ackerman (1984): Hydrostatic pressure, shell compliance and permeability to water vapor in flexible-shelled eggs of the colubrid snake Elaphe obsoleta. -Persp. Vert. Sci., The Hague, 3.

Lynch, J. D. (1966): Communal egg laying in the Pilot Blacksnake, Elaphe obsoleta obsoleta. -Herpetologica, Lawrence, 22(4).

Meshaka, W. E., S. E. Trauth & C. Files (1988): Life history notes: Elaphe obsoleta (Black Rat Snake)-Antipredator behavior. -Herp. Review, Athens, 19(4).

Mitchell, J. C., C. A. Pague & D. L. Early (1982): Life history notes: Elaphe obsoleta (Black Rat Snake)-Autophagy. -Herp. Review, Athens, 13(2).

Morris, M. A. (1984): Life history notes: Elaphe obsoleta (Black Rat Snake)-Autophagy. -Herp. Review, Athens, 15(1).

Myer, J. S. & A. P. Kowell (1971): Loss and subsequent recovery of body weight in water-deprived snakes (Elaphe obsoleta obsoleta). -J. Comp. Physiol., Washington D.C., 75 (1).

Netting, M.G. (1927): A note on the egg-laying of Elaphe obsoleta obsoleta (Say). -Copeia, Ann Arbor.

Nijof, E. (1984): Breeding results: Elaphe obsoleta obsoleta. -Litteratura Serpentium, Utrecht, 4(1)

Pelt, J. Van (1983): Breeding results: Elaphe obsoleta obsoleta. -Litteratura Serpentium, Utrecht, 3(1)

Tuck, R. G., Jr., M. K. Klinkiewicz & K. C. Ferris (1971): Notes on Pilot Blacksnake (Elaphe obsoleta obsoleta) eggs and hatchlings. -Bulletin of Marlyand Herpetological Society, Baltimore, 7 (4).

Sexton, O.J., N. Shannon & S. Shannon (1976): Late season hatching success of Elaphe o. obsoleta. -Herp. Review, Athens, 7(4).

Stickel, L. F., W. H. Stickel & F. C. Schmid (1980): Ecology of a Maryland population of Black Rat Snakes (Elaphe obsoleta obsoleta). -Amer. Midland Natur., Notre Dame, 103 (1).

Weatherhead, P. J. (1989): Temporal and thermal aspects of hibernation of Black Rat Snakes (Elaphe obsoleta) in Ontario. -Canadian J. Zool., 67.

Weatherhead, P.J. & M. B. Charland (1985): Habitat selection in an Ontario population of the snake, Elaphe obsoleta. -J. Herp., Athens, 19 (1). Brothers, D. R. (1994): Elaphe obsoleta (Rat Snake) Reproduction. -Herpetology Review, Athens, 25 (3).

Weatherhead, P. J. & D. J. Hoysak (1989): Spatial and activity patterns of Black Rat Snakes (Elaphe obsoleta) from radiotelemetry and recapture data. -Canadian J. Zool., 67.

"*" materials were derived or quoted from:
A Monograph of the Colubrid Snakes of the Genus Elaphe Fitzinger, Klaus-Dieter Schultz (with contributions by Andre Entzeroth), Koeltz Scientific Books, Czech Republic, 1996.

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Useful Links gives a comprehensive, thorough examination of Elaphe obsoleta obsoleta including geography, physical characteristics, natural history, behavior, habitat, and conservation information. An extremely informative source for students. contains some interesting information, including pictures of feeding and material about lifestyle. gives some interesting pictures, as well as range maps for Wisconsin. gives valuable information about the Black Ratsnake in the northeast (Massachusetts.) Materials include common myths about the snake, as well as its link in the foodchain. contains information about the species in Texas (including range maps and interesting pictures demonstrating differentiation in coloration with respect to geography.) links to a paper addressing behavior patterns in free-ranging Black Ratsnakes. Useful to students interested in behavior.

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List of Museums with Specimens

Department of Herpetology
California Academy of Sciences
Golden Gate Park, San Francisco
CA 94118-4599

Section of Amphibians and Reptiles
Carnegie Museum of Natural History
4400 Forbes Avenue
Pittsburgh, PA 15213

Division of Herpetology
Museum of Natural History
University of Kansas
Lawrence, KS 66045-2454

Museum of Natural Sciences
119 Foster Hall
Louisiana State University
Baton Rouge, LA 70803

Museum of Vertebrate Zoology
3101 Valley Life Sciences Bldg.
University of California
Berkeley, CA 94720

Department of Ichthyology and Herpetology
Royal Ontario Museum
100 Queen's Park
Toronto, Ontario
M5S 2C6 Canada

Texas Cooperative Wildlife Collection
Department of Wildlife and Fisheries Sciences
Texas A&M University College Station
TX 77843-2258

Herpetology Division
Texas Memorial Museum
University of Texas
Austin, TX 78712

Department of Ecology & Evolutionary Biology
University of Arizona
Tucson AZ 85721-1501

EPO Biology, Campus Box 334
University of Colorado
Boulder, CO 80309-0334

Museum of Natural History
Biological Sciences Building
University of Georgia
Athens, GA 30602

Division of Reptiles and Amphibians
Museum of Zoology
University of Michigan
1109 Geddes Avenue
Ann Arbor, MI 48109

Division of Amphibians and Reptiles
National Museum of Natural History
Smithsonian Institution
Washington D.C. 20560

Department of Biology
UTA Box 19498
University of Texas at Arlington
Arlington, TX 76019

Department of Biological Science
University of Texas at El Paso
El Paso, TX 79968

Vertebrate Zoology Division
Peabody Museum of Natural History
Yale University
P. O. Box 208118
New Haven, CT 06520-8118

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