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The ringneck snake or ring-necked snake (Diadophis punctatus) is a colubrid snake species. It is found throughout much of the United States, central Mexico, and south eastern Canada, R.C., 2003. Western Reptiles and Amphibians. Third edition. Houghton Mifflin, Boston, Massachusetts, USA. Ring-necked snakes are secretive, nocturnal snakes that are rarely seen during the day time. They are slightly venomous but their non-aggressive nature and small rear-facing fangs pose little threat to humans who wish to handle them. They are best known for their unique defense posture of curling up their tails exposing their bright red-orange posterior, ventral surface when threatened. Ring-necked snakes are believed to be fairly abundant throughout most of their range though no scientific evaluation supports this theory. Scientific research is lacking for the ring-necked snake and more in-depth investigations are greatly needed, R.P., K. Staniland, R.T. Mason. (2007) Experimental evidence that oral secretions of Northwestern Ring-necked Snakes (Diadophis punctatus occidentalis) are toxic to their prey. Toxicon 50:810–815.]</ref>. It is the only species within the genus Diadophis, and currently fourteen subspecies are identified, but many herpetologists question the morphologically-based classifications.
Ring-necked snakes are fairly similar in morphology throughout much of their distribution. Dorsal coloration is solid olive, brown, bluish gray to black, broken only by a distinct yellow, red, or yellow-orange neck band. There are a few populations in New Mexico, Utah, and other distinct locations that do not have the distinctive neck band. Additionally individuals may have a reduced or partially colored neck band that is hard to distinguish; coloration may also be more of a cream color rather than bright orange or red. Head coloration tends to be slightly darker than the rest of the body with tendencies to be blacker than grey or olive. Ventrally the snakes’ exhibit a yellow-orange to red coloration broken by crescent shaped black spots along the margins. Sometimes individuals lack the distinct ventral coloration but typically retain the black spotting. Rarely do individuals lack both the ventral or neck band coloration so use of those two characteristics are the most simple way to distinguish the species. Size also varies across the species distribution. Typically adults range from 25 to 38 cm, except for D. punctatus regalis which measures 38 to 46 cm. First year juvenile snakes are typically about 20 cm and grow about 2 to 5 cm a year depending on the developmental stage or resource availability. Ring-necked snakes also have smooth scales with 15-17 scale rows at mid body. Males typically have small tubercles on their scales just anterior to the vent which are usually absent in females.
Ring-necked snakes are fairly common throughout much of the United States extending into Southeastern Canada and central Mexico. Eastern populations cover the entire eastern seaboard from the Gulf of Saint Lawrence continuous through the gulf coast of north Texas. Distribution moves inland into northern Minnesota continuing diagonally through the US to include all of Iowa, eastern Nebraska, and most of Kansas. In the western US the distribution is significantly less continuous, with spotty distinct population segments through most of the Pacific Northwest. Populations extend from south-central Washington continuing along the extreme west coast into Mexico. Population segments extend inland into western Idaho, through southern Nevada, into central Utah, and continuing south through Arizona and central Mexico.
Ring-necked snakes occur in a wide variety of habitats. Preference seems to be determined by areas with abundant cover and denning locations spaces. Northern and western species are found within open woodlands near rocky hillsides, or in wetter environments with abundant cover or woody debris. Southern species exist primarily within riparian and wet environments, especially in more arid habitats. Stebbins (2003) identified the species as a snake of moist habitats, identifying that moist soil conditions were the preferred substrate. Ring-necked snakes are also not found above an elevation of 2200 meters. In northern regions, dens are also important in identifying suitable ring-necked snake habitat. Dens are usually shared communally, and are identifiable by an existent subsurface crevasse or hole that is deep enough to prevent freezing temperatures. Since it is a woodland reptile, it can commonly also be found under wood or scraps. Because of the hot weather, they tend to make holes and burrow or they decide to hide under rocks or any suitable material. They are normally found in flatland forests.
The diet of the ring-necked snake consists primarily of smaller salamanders, lizards, frogs, earthworms, and some juvenile snakes of other species. The frequency at which prey species are chosen is dependent on their availability within the habitat. Ring-necked snakes use a combination of constriction and envenomation to secure their prey. The snakes do not have a true venom gland, but they do have an analogous structure called the Duvernoy’s gland derived from the same tissue. Most subspecies are rear-fanged with the last maxillary teeth on both sides of the upper jaw being longer and channeled; the notable exception is D. punctatus edwardsii which is fangless. The venom is produced in the Duvernoy's gland located directly behind the eye. It then drains out of an opening at the rear of the maxillary tooth. Ring-necked snakes strike and secure the prey using constriction. They then maneuver their mouths forward ensuring that the maxillary tooth punctures the skin allowing the venom to enter the prey's tissue. Ring-necked snakes are rarely aggressive to larger predators suggesting that their venom evolved as a feeding strategy rather than a defense strategy. Rather than try to bite a predator the snake winds up its tail into a corkscrew exposing the brightly colored belly.
Ring-necked snakes are primarily nocturnal or highly crepuscular, though some diurnal activity has been observed. Individuals are sometimes found during the day, especially on cloudy days, sunning themselves to gain heat. Yet, most individuals lie directly under surface objects that are warmed in the sun and use conduction with that object to gain heat. Even though ring-necked snakes are highly secretive, they do display some social structure; but the exact social hierarchies have never been evaluated. Many populations have been identified to have large colonies of more than 100 individuals, and some reports identify that some smaller colonies occupy the same microhabitats.
Ring-necked snakes usually mate in the spring. However, in some subspecies mating occurs in the fall, and delayed implantation occurs. Females attract males by secreting pheromones from their skin. Once the male finds a female he starts by rubbing his closed mouth along the female’s body. Then the male bites the female around her neck ring maneuvering to align their bodies so sperm can be inserted into the female’s vent. Females lay their eggs in loose aerated soils under a rock or in a rotted log. Three to ten eggs are deposited in early summer and hatch in August or September. The egg is elongate with a white color contrasted by yellow ends. When hatched, juveniles are precocial and fend for themselves without parental care.
- Diadophis punctatus acricus (Paulson, 1966) — Key ringneck snake
- Diadophis punctatus amabilis (Baird & Girard, 1853) — Pacific ringneck snake
- Diadophis punctatus anthonyi (Van Denburgh & Slevin, 1942) — Todos Santos Island ringneck snake
- Diadophis punctatus arnyi Kennicott, 1859 — prairie ringneck snake
- Diadophis punctatus dugesii (Villada, 1875) — Michoacan ringneck snake
- Diadophis punctatus edwardsii (Merrem, 1820) — Northern ringneck snake
- Diadophis punctatus modestus (Bocourt, 1866) — San Bernardino ringneck snake
- Diadophis punctatus occidentalis (Blanchard, 1923) — Northwestern ringneck snake
- Diadophis punctatus pulchellus (Baird & Girard, 1853) — coralbelly ringneck snake
- Diadophis punctatus punctatus (Linnaeus, 1766) — Southern ringneck snake
- Diadophis punctatus regalis Baird & Girard, 1853 — regal ringneck snake
- Diadophis punctatus similis (Blanchard, 1923) — San Diego ringneck snake
- Diadophis punctatus stictogenys (Cope, 1860) — Mississippi ringneck snake
- Diadophis punctatus vandenburghii (Blanchard, 1923) — Monterey ringneck snake