Common Name: Ring-necked snake, ring snake, baby king snake, red-belly snake, yellow-belly ring snake – Even though the ring around the neck may be interrupted, obscured, or absent altogether, it is the most distinctive feature.
Scientific Name: Diadophis punctatus – The genus name is recognizable as a combination of the Latin word diadema, meaning “royal headband” (a diadem is a crown in English) and ophis, the Greek word for snake. The species name is from the Latin punctum, meaning point. In scientific names, it is used to indicate having small points or dots of color (punctate means “marked with dots or tiny spots” in English). A series of black dots extends along the underbelly.
Potpourri: There are at least twelve subspecies of ring-necked snake, some of which don’t even have the characteristic ring around the collar. The designation subspecies is assigned when there is a difference in morphology, frequently only in coloration but inclusive of other variations in form or structure, usually resulting from geographic separation. Since subspecies are the same species, they can successfully interbreed but do so only if collocated in captivity. Geographic hybridization of snakes is not unusual, although twelve subspecies is outside the norm. The ring-necked snake’s neck ring can be yellow, cream, or orange, the underbelly can be red, yellow or orange, and the back can be gray, olive, brown, or black. Since none of these variants likely contribute to enhanced survival, random genetic variation amplified by inbreeding of isolated populations must be the main factor. The many subspecies result from a diaspora of the shared ancestral ring-necked snake that ranged across North America from Nova Scotia to the Florida Keys, west to the Pacific Coast, and south to Mexico. [1]
Ring-necked snakes are members of Colubridae, by far the largest family of the suborder Serpentes to which all snakes belong. Latin includes several words for snake, a likely result of the long-standing animus toward snakes only enhanced by the biblical account of Satan tempting Eve in the Garden of Eden. In addition to coluber, serpens names the suborder, vipera names the pit viper family Viperidae, and anguis is a genus of lizards called slow worms that have lost all vestiges of legs. The range and diversity of colubrids, which comprise three quarters of all snakes in North America and the majority across the globe, was long thought to have been due to a dearth of research on snakes. Those snakes that did not fall into another, more obvious category like constrictors or vipers, were placed in Colubridae by default. However, most recent research using DNA associations has found that colubrids are monophyletic, evolving from a single ancestor. [2] This means that the evolution of the legless body plan that separated the snakes from the lizards must have been enormously successful ― that they took over a new ecological niche. The emergence of colubrids in the Oligocene Epoch about 40 million years ago just after the mammals expanded in range and numbers in the Eocene provides a logical hypothesis. Rodents living in holes breeding large populations of edible protein provided a resource nonpareil. Slithering, hole-diving lizards that lost their legs to become snakes were perfectly suited to exploit the resource. The Cenozoic Era is often called the Age on Mammals. “If the criterion were to be the most rapid adaptive radiation, the latter half of the Cenozoic would have to be called the Age of Snakes.” [3]
Ring-necked snakes are not rodent eaters. With an average length of twenty inches, mice are too large for their undersized maws. Like all snakes, they are obligate carnivores, ingesting their prey whole usually headfirst, down the gullet to the stomach for digestion ― a writhing esophagus. The brutal efficiency of the down the hatch method is impressive. A two-kilogram snake can ingest and digest prey weighing one kilogram. Black rat snakes range from five to eight feet in length … their name and girth reflect a penchant for the large rodents that they consume. Just as larger snakes evolved in perfecting mammal predation, smaller snake variants broke away genetically to exploit alternative food resource niches. Ring-necked snakes expanded across North America by consuming whatever they could find including insects, small lizards, earthworms, and amphibians. Five ring-necked snakes from George Washington National Forest were dissected in 1939 to reveal a diet that was 80 percent salamanders, 15 percent ants, and 5 percent other insects. This may explain why ring-necked snakes are considered the most common snake in Shenandoah National Park … it is well known as an epicenter of salamander diversity. [4] A preference for salamanders extends northward to Pennsylvania, where a more recent study of 58 northern ring-necked snakes (D. p. edwardsii) found that their primary food was plethodontids, lungless salamanders. [5] Salamanders are masters of concealment with cryptic colors and concealed hideaways under rocks … finding them is challenging. Ring-necked snakes employ chemical sensors as vectors to seek them out. They don’t need to be successful too often, since each meal results in a gain of one gram for every three grams consumed. One or two salamanders a month is plenty for the cold-blooded. [6]
Since snakes lacked bodily appendages for tearing and clawing, the mouth became essential as a weapon with only constricting body coils as backup. Trying to pin down a struggling if hapless victim to position them for swallowing without the restraining benefit of clasping limbs is surely daunting if even possible. It is also not without some danger to the predator, as rats are vicious when cornered. Some snakes evolved muscular bodies, using brute force to literally choke the life out of their prey. Others randomly mutated to produce chemicals in glands surrounding the oral cavity that assisted in some degree toward prey immobilization. In extreme cases, these concoctions are deadly, injected with the fangs that project from the front of the mouths of vipers. Snake venom is a complex of up to 100 proteins that is stored in venom glands that can take several days to replenish once the supply is exhausted. Since the means to kill is vital to viper survival, venom is meted out with care, apropos to prey size and injected through ducts in piercing front teeth at high pressure. This allows for the real possibility that multiple strikes may be needed to land a coup de grâce bite.[7] The ring-necked snake is one of many colubrid snakes that are called rear-fanged. Rather than delivering a thrusting, two-tooth attack like their viperous cousins, they deliver a smaller dose of less potent venom. Limited research has been done on the composition of colubrid venoms, but it has been demonstrated that some affect only birds and lizards with little to no effect on rodents. This supports the general hypothesis that the mutation that led to snakes producing the proteins from which venom is concocted occurred only once and that protein synthesis over time based on types of the prey encountered resulted in specialization. However, the complexity of venom glands and the great diversity of venom composition suggest multiple introductions by different clades. Speculation is the handmaid of scientific study.
Ring-necked snakes produce venom in two glands named for the French zoologist who first noted them during a snake dissection. The full biological function of Duvernoy’s gland is not yet known, although it is certainly for some type of trophic (nutrition related) purpose. There are multiple glands located around a snake’s oral cavity that are necessary to carry out the incongruous process of swallowing oddly shaped objects that can be twice the size of the hole they go into. Lubrication is necessary to slide the jaws slowly forward and digestive enzymes need to start immediately in breaking down skin and muscle tissue. Of course, it helps to kill the prey first. Duvernoy’s glands are located directly behind the eye near the top of the skull and drain through ducts into grooves in posterior maxillary teeth, the so-called rear fangs, homologous to the venom glands of vipers. However, rather than the lighting strike stab of vipers, ring-necked snakes use partial constriction to hold their prey while they bite down, injecting venom through multiple puncture wounds.[8] There is ample evidence that ring-necked snake venom is effective. In one experiment, garter snakes were injected with the oral secretions extracted from ring-necked snakes. They all died withing three hours. [9] Humans are not immune. A researcher was handling a ring-necked snake to take a picture when it bit him on the finger. The sharp, sting-like pain was immediate, followed within minutes by swelling of the finger that spread to the entire hand. Over the next 24 hours, redness spread down the finger from the puncture wound which persisted for the next three days. [10] There are about 700 rear-fanged colubrid snakes that produce some kind of venom which means that these so-called “harmless snakes” are not (harmless).
Ring-necked snakes occupy an elevated position in the food chain, but they do have predators. In addition to a variety of other snakes, raccoons, opossums, skunks, owls, and black bears all routinely prey on ring-necked snakes. If juveniles are included, the predator list extends to toads, shrews, and even large spiders and centipedes. Since females lay no more than ten eggs a year with no parental care thereafter, an attrition rate of about ninety percent is nature’s expectation. However, ring-necked snakes are relatively successful in spite of their small size, as evidenced by their widespread radiation across the continent and their relative density in wooded habitats. They are found frequently in communal groups with up to nine individuals. [11] The higher-than-expected survival rate can be attributed to several behaviors employed to ward off predators. The most notable is turning upside down in a writhing corkscrew movement, an eye-catching display of brightly colored red or orange belly scales. The use of bright colors as deterrent is called aposematism, the opposite of camouflage in that it intentionally draws attention rather than conceals. It is typically employed by otherwise defenseless animals that have poisonous secretions like monarch butterflies and red eft juvenile newts. The aposematic use of reds and oranges is intended to deter birds as they have full color vision whereas mammals see only blues and greens (primates are the only exception). Since ring-necked snakes lack poisonous secretions and since most of their predators are mammals and can’t see red anyway, the “colorful corkscrew” defense cannot be aposematic. It is more likely a surprise maneuver meant to throw an assailant off balance, retreating in the face of an uncertain threat. Some of the less colorful ringneck subspecies also play dead and emit mephitic odors as deterrents, relying on the near universal (vultures excepted) aversion to a rotting and possibly toxic meal.
So what about the namesake neck ring? With all of the aforementioned machinations to ward off predation, why would a conspicuous and contrasting bright yellow ring adorn the otherwise cryptic gray-brown of the dorsal surface? It is undeniably an adaptive mutation that must have had purpose that led to its spread and retention in the diverse populations. Group identification and sexual selection are both implicated by behavior. The neck ring could then serve as a clear “friend or foe” visual indication to promote group cohesion. Ring-necked snakes are very sociable, sometimes living in colonies with up to one hundred individuals. A number of larger snakes that are similarly colored but without the ring prey on ring-necked snakes. The benefit that they gain by living in communes is speculative, but it must be related to enhanced survival comparable to birds in flocks and fish in schools. Larger groups also provide more opportunities for opposite sexes to meet and mate enhancing sexual selection. The neck ring could also function as a colorful beacon of sexual fitness. Male ring-necked snakes are attracted to females releasing fertility pheromones. While only a small number of sightings of ring-necked snakes mating have been recorded, males have been observed rubbing their closed mouths over the female body followed by biting around the neck ring just before copulation. [12] Foreplay is what some sociable animals do. Sociable snakes?
Lastly we return to the subject of subspecies and zoology. What is the purpose of having over twelve ring-necked snake subspecies? They differ in morphology attributable to the geographical radiation of the species. Many are distinguished by the number and distribution of black dots that adorn the underbelly. The black dot configuration may have some physiological function but it is unclear what that might be.[13] The relative rarity of an individual subspecies would not correlate to endangerment because the overarching concern of species extinction is the loss to the biological gene pool. Subspecies can mate with each other to reproduce the baseline DNA codon protein programming of the species. All domestic dogs are Canis familiaris. They range in size and shape from Great Dane to Chihuahua, and aside from the acrobatics that may be required, they could mate and produce offspring that would be some combination of the two. Using the rules applied to snakes, all dog breeds would all be separate subspecies. And what about Homo sapiens? When Carolinus Linnaeus introduced the binomial name for humans in the tenth edition of Systema Naturae in 1758, he identified four varieties: Europaeus, Asiaticus, Africanus, and Americanus. These were the original subspecies that became the foundation for the current racial distinctions [14]. The idea of subspecies is not an altogether helpful concept sociologically. It is not unreasonable to question its usefulness to biology.
References:
1. Behler, J. and King, F. National Audubon Society Field Guide to North American Reptiles and Amphibians, Alfred A. Knopf, New York, 1979, pp 589-679.
2. Zheng, Y., Wiens, J. “Combining phylogenomic and super matrix approaches, and a time-calibrated phylogeny for squamate reptiles (lizards and snakes) based on 52 genes and 4162 species” Molecular Phylogenetics and Evolution 8 October 2015. http://www.wienslab.com/Publications_files/Zheng_Wiens_2015b_MPE.pdf
3. Starr, C. and Taggart, R. Biology, Wadsworth Publishing, Belmont, California, 1989, p 585.
4. Linzey, D. and Clifford, M. Snakes of Virginia, University Press of Virginia, Charlottesville, Virginia, 1981, pp73-77.
5. Cathro, Andrew and Lindquist, Erik 2016. Diadophis punctatus edwardsii (Northern Ring-necked Snake) Diet. Herpetological Review 47 (4): 681
6. Henderson, R. “Feeding Behavior, Digestion, and Water Requirements of Diadophis punctatus arnyi Kennicott”. Herpetologica. 1970, Volume 26 Number 4 pp 520–526.
7. Kardong, K. Colubrid snakes and Duvernoy’s “Venom” Glands .Journal of Toxicology: Toxin Reviews. 6 December 2002, Vol. 21 No. 1 pp 1–15.
8. Mackessy, S. and Saviola, A. “Understanding Biological Roles of Venoms Among the Caenophidia: The Importance of Rear-Fanged Snakes” Integrative and Comparative Biology. 1 November 2016 Volume 56 Number 5 pp 1004–1021.
9. O’Donnell, R. et al. “Experimental evidence that oral secretions of northwestern ring-necked snakes (Diadophis punctatus occidentalis) are toxic to their prey”. Toxicon. November 2007, Volume 50 No. 6 pp 810–815.
10. Brock, T. & Camp, C. Diadophis punctatus edwardsii (Northern Ring-necked Snake) Envenomation. Herpetological Review 2018 Volume 49 Number 2 pp 340-341.
11. Blanchard, F. et al “The Eastern Ring-Neck Snake (Diadophis punctatus edwardsii) in Northern Michigan”. Journal of Herpetology. 15 November 1979 Volume 13 No. 4 p 377.
12. Yung, J. Diadophis punctatus University of Michigan Museum of Zoology https://animaldiversity.org/accounts/Diadophis_punctatus/
13. http://reptile-database.reptarium.cz/species?genus=Diadophis&species=punctatus
14. Graves, J. and Goodman, A. Racism, Not Race, Columbia University Press, New York, 2022. Pp 3-4.
Hiker's Notebook 