Common Name: Corn Snake, Red rat snake, Red corn snake, Pine snake, Chicken snake – Corn may refer to habitat, as they frequent corn fields in search of rodents. Corn may also refer to appearance, as the alternating light and dark scales on the bottom, belly, or ventral side, resemble Indian corn with its similar contrast of light and dark kernels.
Scientific Name: Pantherophis guttata – The generic name means panther-snake (ophis) in Greek. The etymology of panther is not well established. Panthera is the genus of large cats (tigers, lions, leopards, and jaguars) that probably is from the Sanskrit word for tiger, pundarika. Panther widely applied to large cats that have a black coat for night stealth (i.e. black panther).[1] Its use in this case is likely due to the more common and prevalent black rat snake, also a member of the genus. The Latin word guttatim means “drop by drop” and may suggest a dappled pattern. [2] Formerly known as Elaphe guttata, the genus Elaphe has been reorganized in recent years due to DNA inconsistency but is still in wide usage in field guides. [3] Elaphe is Greek for deerskin, which may be due to tan color similarities.
Potpourri: Corn snakes are closely related to the more common black rat snakes and share many behavioral characteristics, especially a preference for rodents as repast. The alternative common name red rat snake is a measure of close association. Geographically, corn snakes inhabit only the warmer, southern regions of eastern North America, suggesting a preference for agricultural meadowlands where corn is common whereas their black cousins venture northward into New England. As with most snakes, the color and arrangement of scales are the main distinguishing feature. Corn snakes, though quite variable in hue with angular blotches that can range from red to brown to dark gray, are nonetheless distinct from the uniformly black scales of the black rat snake. [4] Since every aspect of an animals appearance and behavior must have arisen according to environmental factors as a matter of survival as a species, there must be a causal explanation for the color scheme.
Snakes comprise a physiologically consistent group of the class Reptilia in the suborder appropriately named Serpentes. Three lineages of reptiles emerged from the Permian extinction about 250 million years ago, when approximately 90 percent of all species were wiped out, most likely due to massive lava outflows incident to the formation of the supercontinent Pangaea. Two lineages survived through the succeeding Mesozoic era; the dominant dinosaurs of which birds are the only vestige; and the scaled reptiles which gave rise to lizards and then snakes. While the current, Cenozoic (post Pangaea) era is widely known as the age of mammals, it could equally be considered the age of birds, if numbers are more important, or the age of snakes if rapid adaptive radiation was the key criterion. More than 90 percent of all reptiles living today are lizards or snakes, of which snakes are the vast majority with 2700 species on all continents except Antarctica. [5] Recent phylogenetic research has revealed through DNA associations that the ancestral rat snake arose in tropical Asia in the Eocene Epoch and crossed over the Beringian Land Bridge to North America in the Miocene about 25 million years ago, following the rodents that became their defining source of sustenance.[6]
The adaptive radiation of snakes to occupy new habitat niches precipitated changes in diet, behavior, and appearance as a matter of evolutionary mutations for survival. It is clear from the fossil record and from the presence of vestigial pelvic girdle and hind limb bones in some snakes that they evolved from four legged lizards. Legless reptiles are testimony to the irrefutable progression of Darwin’s evolution. Amphibians that first emerged from the oceans with fins needed legs for locomotion and scaly skin to maintain body fluids to continue as terrestrial reptiles. The success of snakes was necessarily advanced by the loss of quadrupedal capability. The most compelling rationale for this extreme retrogression is rodent burrows. Legs and feet get in the way when slithering down a rabbit hole to access its inhabitants. There was never going to be a case where a cold-blooded snake would chase down a warm-blooded mouse in the open, regardless of the ultimate outcome of Aesop’s tortoise and hare. Cornering rodents in their dens was the impetus and proto snakes with smaller legs were successful in survival, passing their genes down to their eventually legless progeny.[7]
The color scheme of corn rat snakes is also with purpose. For some animals, notably birds, colors are in many cases a matter of mate choice. This cannot be the case with reptiles with no visible distinction between the sexes save perhaps size. What is important is blending into the surrounding environment. If an animal is subject to predation, and most are, then being difficult to find is a survival asset. Snakes are subject to predation by carnivores like foxes, bobcats, and raccoons in addition to birds of prey like hawks. However, an equal and opposite reason for rat snake camouflage is stealth for predation. The black rat snake stands out, literally. Among the greens and dappled hues of the forest floor, jet black is hardly stealthy. Arguably, black confers stealth at night and this surely plays a role as black snakes hunt at night in summer and frequently climb trees in search of songbirds and squirrels. Corn snakes not so much, mostly lurking in underbrush like cornstalks in search of prey. While a limited data point, two corn snakes were eviscerated in Virginia in 1939 to reveal the remains of a field mouse, a skink lizard, and a wood-boring beetle. [8] The variable colors of corn snakes in darker blotches on a lighter background are not unlike those of other snakes like copperheads and timber rattlesnakes in addition to the nearly identical milk snake. It must be concluded that snake color pattern is not all that important as a survival attribute and color variability is therefore not constrained by it.
Detecting, localizing, overpowering, and killing prey for food is a matter of snake survival. Sensory perception is therefore central to snake hunting success. Vision, hearing, and smell all play a role. Taste does not play a role, as snakes need no sensors to sample food swallowed whole and headfirst. The unblinking, lidless eyes of snakes are sinister and effective. Short range vision of corn rat snakes is good even under the low light conditions of darkness. Since snakes lack mammalian middle ears, connective eustachian tubes, and eardrums (tympana), they are relatively insensitive to airborne noise. However, sound induced ground vibrations are detected by conduction through the solid bones of the skeleton, allowing for initial detection of activity but lacking any directional specificity. Smell is the most important corn rat snake sense [9], enhanced by employing the tongue as an air sampling appendage. The twisting, forked tongue is an equally sinister snake attribute. Chemical molecules in the air that convey smell are sampled by the flickering tongue and deposited into two small ducts in the top of the mouth cavity. This repository is the vomeronasal, or Jacobson’s organ, which sends scent data to the brain for interpretation as food, foe, or friendly mate.[10] When a corn rat snake is encountered on the trail, it will first feel footsteps, localize with beady-eyed vision, and conduct a full evaluation with smells sampled lingually. It will respond according to instincts tempered by experience.
A corn rat snake’s reaction to its encounters with other animals depends on how its brain interprets what its sensory suite detects. According to the analogous mammalian amygdala, sometimes referred to as the reptilian brain, reactions include fight, flight, fear, and, if you happen to be a corn snake of the opposite gender, sex. The mnemonic used by neuroscientist students for these functions is “the 4 F’s” of the amygdala, substituting carnal knowledge fornication. If a threat is perceived and an escape route is open, corn snakes take flight and slither to safety. Laboratory testing has demonstrated that corn snakes are adept at finding an escape route based on spatial awareness and learning when confronted with multiple options. Fleeing to leaf litter bowers is a practiced strategy. [11] If cornered, corn rat snakes will fight, taking up a defensive, coiled, readiness to strike posture, bobbing and weaving to confront the threat. Corn rat snakes also vigorously shake their tails like rattlesnakes when threatened, lacking only the noise-making rattle. While the reason for this evolutionary trait is unknown, it is speculated that it is defensive, presenting a confusing tableau of a double-ended body to a potential predator. It is a relatively common trait among members of the Colubrid snake family. However, if fear is not a factor according to the sensory profile and there are prospects for a meal or a mate, escape changes to engage.
The adaptations necessary and sufficient for snakes, obligate carnivores, to subdue their quarry without the benefit of arms and legs to hold and pummel or teeth to impale and tear is testimony to the consequential driving force of evolution. Poisonous snakes engage in chemical warfare, injecting toxins with fangs to immobilize prey. The constrictors, like corn rat snakes, employ brute force. The widespread use of constriction among snakes suggests that it probably was an early adaptation, arising in the Paleocene Epoch, contributing to the rapid radiation of constrictor snakes to new habits. [12] An evaluation of prey handling complexity comparing constrictors with jaw holding and body pinning practiced by other species revealed the simplicity and effectiveness of the former. It is surmised that the constriction method evolved to subdue “vigorously struggling prey” which may have been necessitated to successfully catch and kill rodents. Constrictors mastered the physics of muscular compression. [13]
And then there is the matter of mating, which begins with sensory perception of a potential partner of the same species. Since snakes are solitary and mostly hidden from view over wide-ranging habitats, the importance of pheromones in mate localization cannot be understated. The search for a mate begins in early spring, and, if successful, results in the deposition by the female of up to 30 eggs in a secluded location chosen with enough heat (82 °F is ideal) and humidity to promote incubation. As with almost all reptiles, there is no parental support and protection. The eggs must remain undiscovered by predators for over 60 days when they hatch out as foot-long juveniles. In the three years that it takes to reach full size; many are lost to the gene pool due mostly to either becoming prey or due to the inability to find prey. [14] For corn rat snake population stability, one male and one female must, on average, survive, meet, and mate from each clutch of eggs. In the native habitat in the southeastern United States, corn rat snakes hold their own, in spite of being killed by humans, many of whom wrongfully fear all snakes. For those who like snakes, corn rat snakes make good pets, as they are docile and do not object to being handled. This has led to corn rat snakes becoming an invasive species in many of the islands of the Caribbean as they have been imported and escaped to a predator free habitat. [15]
References:
1. Webster’s Third New International Dictionary of the English Language, Unabridged, G. C. Merriam Company, Chicago, 1971, p 1632
2. Simpson, D. Cassell’s Latin Dictionary, Wiley Publishing, New York, 1968, p 211.
3. Crother, B. “Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding” Society for the Study of Amphibians and Reptiles Herpetological Circular. 2012 Volume 39: pp 1–68
4. Behler, J. and King, F. National Audubon Society Field Guide to North American Reptiles and Amphibians, Alfred A Knopf, New York, 1979, pp 604-607
5. Starr, C. and Taggart, R. Biology 5th Edition, Wadsworth Publishing Company, Belmont, California, 1989, pp 580-585.
6. Burbrink F. and Lawson, R “How and when did Old World rat snakes disperse into the New World?”. Molecular Phylogenetics and Evolution. 27 September 2006 Volume 43 Number 1pp 173–189.
7. Title, O. et al “The macroevolutionary singularity of snakes” Science, 22 February 2024, Volume 383 Number 6685. pp 918-923.
8. Linzey, D. and Clifford, M. Snakes of Virginia, University of Virginia Press, Charlottesville, Virginia, 1981, pp 96-102
9. Saviola, A et al “Chemosensory responses to chemical and visual stimuli in five species of colubrid snakes”. Acta Herpetologica. 19 April 2012 Volume 7 Number 1 pp 91–103
10. Dowling, H. “Reptilia” Encyclopedia Brittanica, Macropedia, University of Chicago, Illinois, 1974. Volume 15 pp 725-739.
11. Holtzman, D. et al “Spatial learning of an escape task by young corn snakes, Elaphe guttata guttata“. Animal Behavior. January 1999 Volume 57 Number 1 pp 51–60.
12. Greene, H. and Burghardt, G. “Behavior and Phylogeny: Constriction in Ancient and Modern Snakes”, Science 7 April 1978. Volume 200 Number 4337.
13. Saviola, A. and Bealor, M. “Behavioral complexity and prey-handling ability in snakes: gauging the benefits of constriction”. Behavior. 30 May 2007 Volume 144 Number 8 pp 907–929.
14. Smithsonian Zoo. Eastern corn snake | Smithsonian’s National Zoo and Conservation Biology Institute 15. Commonwealth Agricultural Bureaux International. (CABI) database https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.84655
Hiker's Notebook 