Juvenile  (photo by Adam Mann)	Adult (photo by Mizuki Takahashi)

Natural History

Description:

The Black Ratsnake is one of the most common snakes found in West Virginia.  It is considered to be the state’s largest serpent.  Individuals normally reach an adult size of 4 to 6 feet; however, specimens have been known to exceed 8 feet in length.  In cross section, the bodies of ratsnakes are not round, but instead resemble a loaf of bread.  The dorsal scales are weakly keeled, while the lateral scales are smooth.  Anal plate is divided.

Adults: The bodies of adults are generally black on the dorsal side.  Red, yellow, or white areas of skin appear between the scales, often showing evidence of the blotched pattern characteristic of juveniles (Conant and Collins, 1998).  The ventral side is bright white in the throat and neck region, yielding to mottled black and white checkers along the midbelly.  Posteriorly, the ventral scutes are uniformly black.

Juveniles: Juveniles exhibit a strong pattern consisting of 28 to 40 dark brown or black dorsal blotches on a uniformly gray background (Mitchell, 1994).  The venter is checkered black and white.  There is also a distinct brown or black stripe on each side of the head, extending from the eye to the posterior jaw.  Normally, the pattern begins to become obscure and darken in individuals over 2.5 feet, but can be retained much longer.

Similar Species:

Black Ratsnakes are often confused with Northern Black Racers (Coluber c. constrictor), Black Kingsnakes (Lampropeltis g. nigra), Cornsnakes (Elaphe g. guttata), Eastern Milksnakes (Lampropeltis t. triangulum), and sometimes Northern Copperheads (Agkistrodon contortrix mokasen).  Racers are uniformly black (except under the chin) with smooth scales on the dorsal side.  They are generally more slender and are round in cross section.  Kingsnakes have smooth scales and single anal plates.  They also possess white or yellowish flecks bordering the lower sides of the dorsum, which sometimes form indistinct chains around the body.   Most confusion in Black Ratsnake identification is due to the juvenile pattern.   Juvenile racers have a blotched pattern on the body, but have a black tail.  Cornsnakes have a pattern consisting of red and orange blotches, which is retained into adulthood.  Milksnakes have a red and white pattern, but have smooth scales and a single anal plate.   Copperheads have a banded pattern that is wider on the side than the top, and juveniles have yellow tails.

Habitat and Habits:

Black Ratsnakes are generally woodland dwellers, but are often found in a variety of habitats such as swamp borders, river flood plains, rocky hillsides, mountain ledges, and open fields (Green and Pauley, 1987).  They are often found in more developed areas, residing in houses, yards, and farm buildings where they obtain food.

Black ratsnakes are powerful constrictors.  They are semi-arboreal in nature and are often seen climbing trees to take shelter in hollowed cavities and to search for food.  They feed almost exclusively on warm-blooded prey such as mice, rats, shrews, voles, squirrels, chipmunks, rabbits, and birds.  They have been known to raid bird nests and devour the eggs.  Juveniles have been seen eating small amphibians and lizards as well.   Black Ratsnakes are chiefly diurnal, but also remain active at night during hot summer months.

The behavior of Black Ratsnakes is unpredictable.  Most are aggressive when cornered or captured.  They often vibrate their tails in leaf litter, making some believe that they are venomous rattlesnakes, ultimately leading to their demise.   However, some individuals are quite docile and show no objection to being handled.  

Reproduction:

Mating occurs in late April, May or early June.  One clutch of 4 to 25 eggs is laid in rotten logs, decaying leaf litter, sawdust piles, or fallen hollow trees during late June or July.  The eggs are white and oblong, averaging less than 2 inches in diameter.  Incubation takes approximately two months.  Hatching occurs from late August into October, with young measuring 11 to 16 inches in length.  Sexual maturity is reached after 4 years of age.

Distribution

Black Ratsnakes are very common in West Virginia and are found statewide.  They have been observed from the lowest elevations up to 3,760 feet (Green and Pauley, 1987).

Status

 The Black Ratsnake is extremely common and prolific.  Thus, it is not listed as rare, threatened or endangered on the state or federal level.

Interesting Facts

1)  Black Ratsnakes are more commonly known in WV as “blacksnakes,” a name that probably groups them together with Northern Black Racers and Black Kingsnakes.

2)  Black Ratsnakes are sometimes called “pilot snakes” because of their hibernative association with venomous species.  It is believed that they pilot the other snakes to the safety of the den.  This is untrue, of course.

3)  It is believed that Black Ratsnakes interbreed with copperheads, producing a venomous ratsnake.  This is not possible.  Most likely, the confusion arose due to the juvenile pattern of Black Ratsnakes superficially resembling copperhead juveniles.

*Taxonomic Changes

The scientific classification of the Black Ratsnake is currently in dispute.  With further investigation, the name is likely to change to an entirely separate genus, species, or both.

Recent publications by Frank T. Burbrink (see below) have determined that the Black Ratsnake has evolved from separate evolutionary lineages and can no longer be classified under a single species name.  Instead, it must be considered one of three separate species (Elaphe obsoleta, E. spiloides or E. alleghaniensis) based on geographic distribution throughout the eastern United States.

A new publication by Urs Utiger in the Russian Journal of Herpetology has determined that Old and New World ratsnakes are phylogenetically different, requiring a change in genus (Utiger et al, 2002).  The proposed genus name for New World Ratsnakes is Pantherophis, which is resurrected from a previous taxonomic synonym.  This is very similar to the change from Natrix to Nerodia several years ago for North American watersnakes.

References

Burbrink, F. T., R. Lawson, and J. B. Slowinski.  2000.  Mitochondrial DNA   phylogeography of the North American rat snake (Elaphe obsoleta): a critique of the subspecies concept.  Evolution 54: 2107-2114.

Burbrink, F. T.  2001.  Systematics of the Eastern Ratsnake Complex (Elaphe obsoleta).  Herpetological Monographs 15: 1-53.

Conant, Roger, and Joseph Collins.  1998.  A Field Guide to Reptiles and Amphibians: Eastern/Central North America.  New York: Houghton Mifflin Company.

Green, N. Bayard, and Thomas K. Pauley.  1987.  Amphibians and Reptiles in West Virginia.  Pittsburgh: University of Pittsburgh Press.

Mitchell, Joseph C.  1994.  The Reptiles of Virginia.  Washington, DC: Smithsonian Institution Press.

Utiger, U., N. Helfenberger, B. Schatti, C. Schmidt, M. Ruf, and V. Ziswiler.  2002.  Molecular Systematics and Phylogeny of Old and New World Ratsnakes, Elaphe AUCT., and related genera (Reptilia, Squamata, Colubridae).  Russian J. Herpetol. 9(2): 105-124.

Page created by Adam Mann
Last Updated - February 2003
Questions or comments on the web site?  Email Dr. Thomas K. Pauley at pauley@marshall.edu