Black Rat Snake

Common Name: Black Rat Snake, Pilot Snake, Chicken Snake, Black Snake, Mountain Black Snake – The dorsal scales are predominantly black absent any multi-hued blotches or stripes; the species is noted for its consumption of small mammals, which would include rats if there were any in its habitat areas.

Scientific Name: Pantherophis alleghaniensis – Panther is a term that is recognized as black in color from its use to designate the melanistic variants of the Panthera genus of large cats (a black leopard or jaguar is called a panther); ophis is the Greek word for snake. This species of rat snake was first identified in the Allegheny Mountains, a somewhat anachronistic name for the westernmost uplands of the Appalachian Mountains. Known sometimes more frequently as Elaphe obsoleta or Coluber obsoletus due to current taxonomic uncertainty.

Potpourri: The black rat snake is the largest and probably the most frequently encountered snake in the Appalachian region. Although the actual record length is subject to fabulist exaggeration, numerous reports of over 8 feet have been documented and 5-6 feet is not uncommon. The insidious serpent of the Garden of Eden casts a pall on all snakes and the prevailing ophidiophobia that they evoke would not normally bode well for the black rat snake’s survival in the anthropocentric world; its sinister hue and hulking size do not commend it. However, its non-aggressive mannerisms in combination with its control of the otherwise unwieldy rodent population make it one of the most popular of all snakes, a synanthrope that many farmers encourage in barns and attics for “rat patrol.”

Rat snakes comprise several closely related genera of about 50 species recently categorized according to DNA analysis from the original single genus Elaphe that have a global northern hemisphere presence. In general, they are characterized by their prey, consisting primarily of small mammals and occasionally birds all of which they kill by constriction. They are generally large, a necessary adaptation for sufficient musculature to affect expiration of their prey, non-venomous, there being no reason to produce a poison to kill something that is already dead, and non-aggressive in human interactions. They inhabit woodlands and congregate in areas with high rodent populations, like farm buildings and fields. While the black rat snake predominates in the northeast and mid-Atlantic states, there is a yellow variant further south, an orange variant in Florida, and a brown variant in Texas.

The black rat snake is a consummate predator in a home range area of about 25 hectares with occasional forays of over a kilometer. The hunt is nearly perpetual, as a field mouse provides only about 30 calories to the 20 calorie a day trophic needs of the snake. In addition to their stealth and strength in terrestrial rodent questing, black rat snakes are arboreal and can ascend even smooth-barked trees in search of avian prey; the alternative sobriquet chicken snake accounts for a penchant for chicks and eggs to the chagrin of the fostering farmer. According to Linzey and Clifford in Snakes of Virginia, a survey of the stomach contents of 85 black rat snakes conducted in 1939 revealed a prey distribution of one third mice, one third birds with a balance of squirrels, rabbits, and shrews. However, with a modicum of irony, prey becomes predator; black rat snakes are prey to large raptors, notably red-shouldered hawks and great horned owls in addition to a variety of mammalian carnivores; they provide about 2,000 calories, a substantial carnivore feast. Defensive measures are therefore necessary and include tail vibrations, presumably to mimic the venomous rattlesnakes, and the emission of a mephitic aroma as an allomone deterrent. But the most curious adaptation is passive, freezing in a loosely spiraled stance with distinct body kinks. This is not analogous to the coiled stance of the rattlesnake, as black rat snakes do not strike, but must be visual in effect – perhaps the rugosity conveys an un-snake like appearance to avoid detection.

Melanism is common in animal adaptations and mutations ranging from flitting swallowtail butterflies to “black panther” leopards and jaguars. Black affords nocturnal stealth for predators and crypsis for prey. Conversely, black contrasts starkly with background tans and greens in the bright sun of diurnal expedition; a black snake is hard to miss along the trail. For the black rat snake, body temperature control is a factor, and hunting at night is a summer only proposition. In spring and fall, cooler temperatures mandate daytime hunting with the concomitant risk of detection. All things considered, black must be an acceptable option, as there are a number of black snakes and melanistic mutations of some snakes that are not normally black such as the king snake and hognose snake. The black racer (Coluber constrictor) is an example. It is nearly identical in appearance to the black rat snake down to the detail of the white area on the underside of the jaw; the two are frequently confused. The differences are subtle: the black racer has a round cross section and dull all black scales; the black rat snake has a “bread loaf” cross section and shiny black scales with some white edges. In spite of the species name constrictor, the black racer eats its prey live without crushing the life out of it a priori. They are racers in the sense that they are fast snakes, reaching speeds of up to 4 miles per hour, a fast walking pace but hardly a sprint.

The life cycle behaviors of black rat snakes are significantly affected by seasonal temperature variations, the phenology of cold bloodedness. The winter den is called a hibernaculum and is frequently shared with other snakes, notably copperheads (Agkistrodon contortrix) and timber rattlesnakes (Crotalus horridus); the writhing mass can include hundreds of individuals, a dystopian nightmare of the first order. In that snakes are cold-blooded so that there is no body heat effect and solitary in nature and nurture, these ophidian conclaves are something of a mystery. Folklore becomes fact in the absence of science and snake dens are no exception. The common name pilot snake is attributed to the notion that the black rat snake leads other snakes to its winter den as a Palladium against the elements, an altruistic cross-species behavior that belies all aspects of reptilian antisocial mannerisms. As a measure of the rationality of the pilot snake trope, it is also widely held that a dead black rat snake draped over a fence railing will bring rain; if this is the case, then the gods must be crazy.

Black rat snakes emerge from the winter group den in the spring and seek out a mate by mid-May to early June, a necessary and sufficient exception to their summer solitude. Smell is the primary sensory organ for snakes and pheromones accordingly play a central role in colocation. On trysting, the male and female snakes lie in coital consummation for several hours. In that speciation is the exchange of genes in interbreeding to produce fertile offspring in perpetuity, evolution has favored sometimes elaborate physiologies to this end. Many reptiles including black rat snakes are endowed with two penises, each known logically as a hemipenis; only one is used at a time. And that is not all. According to Schilthuizen in Nature’s Nether Regions each penis is “a fascinatingly beautiful bouquet of red and deep purple grooved, multitoothed spikes, like a clutch of medieval halberds.” The reason for the “double halberd” penis is a matter of current scientific research and a number of plausible hypotheses have emerged. The predominant theory may be called “lock and key” – the complexity of the genitalia may act to establish species relationships according to form, fit and function (if the glove won’t fit you can’t convict). A rival theory promotes the spikes as stays, prolonging the sexual encounter to promote fertilization. The dual penis arrangement is perplexing in its own right, and a theory (not without a hint of anthropocentric guile) called cryptic female choice is proffered in explanation. Many female reptiles (and other animals including black bears) have the ability to control implantation in order to select the most beneficial mate (while it is unclear what a female snake may be looking for, strength and stamina are likely candidates). The dual penis, each with its own separate testis, would allow for multiple inseminations to promote male “reproductive rights.” Regardless of whatever sexual intrigues may have occurred, about five weeks later the female lays about a dozen eggs which emerge about eight weeks later as foot long hatchlings – and life goes on.