You might be surprised to learn that South Dakota’s grasslands harbor only one truly green snake species, despite occasional sightings of greenish-colored serpents across the state. While prairie landscapes stretch endlessly in every direction, the bright emerald reptiles you encounter represent just a small fraction of South Dakota’s 16 snake species.
Understanding which snakes display green coloration helps you identify these harmless creatures during your outdoor adventures, whether you’re hiking through meadows, exploring the Black Hills, or simply maintaining your backyard garden.
This guide walks you through the genuinely green snake native to South Dakota and introduces you to two garter snake species that sometimes appear greenish depending on lighting conditions and individual variation.
You’ll learn distinctive identification features, preferred habitats, and where these snakes typically spend their time throughout the state.
Green Snakes in South Dakota
Smooth Green Snake
The smooth green snake, scientifically known as Opheodrys vernalis, stands as South Dakota’s only snake with uniformly bright green coloration from head to tail.
This slender, non-venomous species measures between 12 and 22 inches in length and earns its name from the smooth texture of its scales, which lack the ridges found on many other snake species.
You’ll recognize this snake immediately by its brilliant emerald upper body contrasting sharply with a whitish or pale yellow belly. The coloration serves as exceptional camouflage among grasses and vegetation, making these snakes remarkably difficult to spot even when they’re right in front of you.
Interestingly, the green appearance results from a combination of yellow and blue pigments in the skin, and upon death, the snake’s color shifts from green to blue as the yellow pigment degrades.
Where to Find Them
Smooth green snakes in South Dakota occupy three distinct, isolated ranges rather than occurring continuously across the state. You’ll find populations in the Black Hills region of western South Dakota, extreme northeastern counties near the North Dakota border, and a small area in extreme southeastern South Dakota.
Recent observations have expanded their recognized distribution, with sightings reported in Corson, Edmunds, and McPherson counties suggesting additional populations along the northern border.
These snakes prefer moist grassy areas in wet meadows, prairies, and woodlands, though they’ve also adapted to residential and suburban environments.
Look for them under logs, rocks, or within thick green vegetation where they hunt for their preferred prey. They’re most active during warmer months and retreat to mammal burrows or invertebrate tunnels for winter hibernation, often sharing these spaces communally with other small snake species.
Key Insight: The smooth green snake is monitored by the South Dakota Natural Heritage Program due to its isolated populations. If you observe one, consider reporting your sighting to South Dakota Game, Fish and Parks to help track these populations.
Behavior and Diet
Unlike constricting snakes that squeeze their prey, smooth green snakes feed primarily on small invertebrates including crickets, grasshoppers, caterpillars, spiders, and earthworms.
They strike quickly and swallow their prey alive. Occasionally, you might observe them eating snails, slugs, beetles, or even small frogs.
These snakes are among the most docile species you’ll encounter in South Dakota. They rarely bite when handled, and even when they do, their small mouths typically fail to break human skin. Their primary defense mechanism relies entirely on camouflage and quick escape into dense vegetation rather than aggressive behavior.
Pro Tip: Smooth green snakes become active in spring after emerging from hibernation, with breeding occurring shortly afterward. Females lay 3 to 11 eggs in late July or August, typically within organic material like decaying logs. The eggs hatch within about a month due to extended retention in the female’s body before laying.
Western Garter Snake
The western garter snake, also called the terrestrial garter snake or wandering garter snake (Thamnophis elegans vagrans), represents one of three garter snake species found in South Dakota.
While not truly green, many individuals display a dull brown to greenish coloration that can appear green under certain lighting conditions, leading to confusion with the smooth green snake.
This medium-sized non-venomous snake typically grows between 18 and 30 inches in length with a robust body and distinctly large head separated from the neck.
You’ll notice the upper lip, chin, and throat are white or yellow, and the eyes are moderately large with round pupils. The defining characteristic includes three longitudinal stripes running the length of the body, though the ground color varies considerably between individuals.
Where to Find Them
Western garter snakes in South Dakota occupy two separate geographic ranges. One population inhabits the northwestern edge of the state near the Montana and North Dakota borders, while another thrives in the western Black Hills region. These snakes demonstrate habitat flexibility, occurring in forests, shrublands, wetlands, fields, and rocky areas.
Unlike the smooth green snake’s preference for moist grasslands, western garter snakes adapt to various environments and often appear near water sources.
They’re active, quick-moving snakes that typically retreat to thick grass or brush when encountered. However, if cornered or grasped, they will bite in defense and may release a foul-smelling musk from glands near the base of their tail.
Common Mistake: Don’t confuse the racer (Coluber constrictor) with garter snakes. Racers are gray-green to bluish-green and significantly faster, earning their common name. They also grow larger, reaching 30 to 50 inches, and prefer more open terrain than garter snakes.
Identification Features
| Feature | Smooth Green Snake | Western Garter Snake | Plains Garter Snake |
|---|---|---|---|
| True Color | Bright, uniform green | Brown to greenish | Gray-green with greenish tint |
| Size Range | 12-22 inches | 18-30 inches | 15-34 inches |
| Stripe Pattern | No stripes | Three yellow/greenish stripes | Orange back stripe, greenish-yellow side stripes |
| Scale Texture | Smooth, no ridges | Keeled (ridged) scales | Keeled (ridged) scales |
| Head Shape | Small, narrow | Large, distinct from neck | Moderate, distinct from neck |
| Habitat | Moist meadows, prairies | Varied: forests to rocky areas | Prairies, grasslands near water |
Plains Garter Snake
The plains garter snake (Thamnophis radix) ranks as South Dakota’s most widespread snake species, found in every county across the state. While primarily gray-green or light brown to black in ground color, some individuals display an olive green surface color that makes them appear greenish, particularly in certain lighting conditions.
This non-venomous snake measures between 15 and 34 inches in length and features distinctive coloration that sets it apart from other species. You’ll observe a prominent orange or bright yellow stripe running down the center of the back, flanked by greenish-yellow stripes along each side.
Two alternating rows of black spots appear between these stripes, standing out especially well on individuals with the olive green ground color. The very top of the head displays distinct light yellow spots, serving as an excellent field identification characteristic.
Where to Find Them
Plains garter snakes inhabit prairies and grasslands almost exclusively, showing a strong preference for areas near freshwater sources such as streams, ponds, wetlands, and marshes.
Their abundant population and adaptability to human-modified landscapes means you might spot them near abandoned buildings, trash heaps, or vacant lots throughout both rural and suburban South Dakota.
These snakes demonstrate remarkable cold tolerance, ranking among the most cold-hardy snake species in North America. They’ll even emerge from hibernation on warmer winter days when temperatures rise sufficiently, a behavior uncommon among reptiles at this latitude.
During winter, they seek shelter below the frost line, often congregating in communal dens that may house dozens or even hundreds of individuals.
Important Note: All three garter snake species in South Dakota are non-venomous and considered docile compared to many other snake species. They rarely bite unless directly threatened, and their small teeth pose minimal risk to humans.
Diet and Behavior
Plains garter snakes feed primarily on earthworms, slugs, and small amphibians, though they’ve adapted to take advantage of available prey. Researchers have documented them preying on small mammals and even birds, including species like the Eastern Meadowlark and Bank Swallow.
They’re active foragers that hunt during daylight hours, using both visual cues and scent detection through their forked tongues.
When you encounter a plains garter snake, it will typically attempt to flee first. If escape proves impossible, the snake may flatten its body to appear larger, release musk, and strike defensively.
These defensive strikes rarely result in actual bites, serving mainly as warnings. The species is considered more docile than other garter snakes, making it relatively safe to observe from a respectful distance.
Distinguishing True Green from Greenish Snakes
The most reliable way to identify whether you’ve encountered South Dakota’s only true green snake or a greenish-colored garter snake involves examining several key characteristics beyond just color.
Color alone can mislead you, especially in varying light conditions or with juvenile snakes that may display different patterns than adults.
Color Uniformity and Pattern
The smooth green snake displays completely uniform bright green coloration across its entire upper body, head, and tail with no stripes, spots, or other markings. The green appears consistent in all lighting conditions.
In contrast, both western and plains garter snakes feature prominent longitudinal stripes running the length of their bodies, even when the ground color appears greenish. These stripes remain visible regardless of the viewing angle or light.
Body Size and Proportion
Smooth green snakes maintain a slender, delicate build throughout their entire length with a small, narrow head barely distinct from the neck.
Garter snakes, particularly the plains garter snake, display a more robust, thicker body with a head that’s noticeably wider than the neck. This difference in body proportion becomes apparent even at a distance.
Scale Texture
Running your hand gently along the snake’s body (if you can safely capture and handle it) reveals the smooth green snake’s namesake smooth scales, which feel almost silky.
Garter snakes possess keeled scales with a raised ridge running down the center of each scale, creating a rougher texture. You can often observe this texture difference visually as well, with garter snakes appearing less glossy than smooth green snakes.
Pro Tip: If you’re uncertain about identification, photograph the snake from multiple angles including a clear shot of the head and upper body. The combination of uniform green color, smooth scales, lack of stripes, and slender build definitively identifies the smooth green snake.
Safety Considerations and Conservation
South Dakota hosts only one venomous snake species: the prairie rattlesnake (Crotalus viridis). Neither the smooth green snake nor any garter snake species poses a venomous threat to humans.
The greatest risk when encountering these harmless snakes comes from misidentification and unnecessary fear leading to harm to the snake rather than danger to the person.
Handling Precautions
While these species are non-venomous, you should still exercise caution when encountering any snake in the wild. Smooth green snakes rarely bite and typically cannot break human skin even when they attempt to defend themselves.
Garter snakes can deliver a bite if threatened, though their small teeth usually cause only minor scratches. The more significant concern involves the defensive musk that garter snakes release when handled, which produces a strong, unpleasant odor that can be difficult to wash from skin and clothing.
If you choose to observe these snakes, maintain a respectful distance of several feet. Never attempt to capture, handle, or relocate snakes unless you have proper training and a valid reason to do so. Most snake encounters end peacefully when you simply give the animal space to retreat on its own.
Conservation Status
The smooth green snake’s isolated population distribution makes it a species of concern in South Dakota. The South Dakota Natural Heritage Program actively monitors populations, and observations contribute valuable data to conservation efforts.
Habitat preservation, particularly of moist meadows and prairies, plays a crucial role in maintaining viable populations of this species.
Garter snakes face fewer conservation concerns due to their adaptability and widespread distribution. However, all snake species benefit from public education that reduces unnecessary killing based on fear or misidentification.
These snakes provide valuable ecosystem services by controlling populations of insects, rodents, and other small prey animals.
Important Note: Never kill or harm snakes based solely on appearance or fear. If you encounter a snake near your home and want it removed, contact local wildlife authorities or a licensed wildlife removal specialist who can safely relocate the animal. Remember that 15 of South Dakota’s 16 snake species are completely harmless to humans.
When and Where You’re Most Likely to See Green Snakes
Understanding seasonal activity patterns and preferred microhabitats increases your chances of observing these elusive reptiles during outdoor activities. South Dakota’s harsh winters limit snake activity to approximately six months annually, with peak observation opportunities occurring during specific seasons.
Seasonal Activity Patterns
Spring emergence typically begins in April when temperatures consistently reach the 60s during daylight hours.
Smooth green snakes and garter snakes emerge from winter hibernation ready to breed, making late April through May an excellent time for observations. During this period, snakes spend more time exposed while seeking mates and warming themselves after months of dormancy.
Summer activity peaks in June through August, though snakes become more secretive during extreme heat. You’ll most likely encounter them during cooler morning and evening hours when they actively hunt for prey.
Midday observations decrease as snakes seek shade and shelter from intense summer sun, particularly during heat waves when temperatures exceed 90 degrees.
Fall activity continues through September and into October as snakes prepare for winter. They feed intensively during this period to build energy reserves for hibernation. By late October or early November, depending on weather patterns, snakes return to winter dens and remain largely inactive until spring.
Optimal Observation Locations
For smooth green snakes, focus your search efforts in the three known distribution areas: the Black Hills region, northeastern counties (particularly Corson, Edmunds, and McPherson), and the extreme southeastern corner of the state. Within these areas, concentrate on moist meadows, grassy areas near streams or ponds, and edges of woodlands where grass meets trees.
Western garter snakes appear in northwestern counties and throughout the Black Hills, favoring areas with diverse habitat structure. Look near water sources, in rocky outcrops, and along forest edges.
Plains garter snakes occur statewide, making them your most likely green-tinted snake encounter anywhere in South Dakota, especially near wetlands, prairie ponds, and irrigated agricultural areas.
Key Insight: Check under flat rocks, logs, and debris piles during cooler parts of the day. Snakes often thermoregulate by positioning themselves under objects that warm in the sun, providing heat from above while the snake remains protected from predators and excessive temperature fluctuations.
Frequently Asked Questions
No green or greenish snakes in South Dakota pose any danger to humans. The smooth green snake, western garter snake, and plains garter snake are all non-venomous species. The smooth green snake rarely bites even when handled, and garter snakes only bite defensively when they cannot escape. None of these species produce venom or cause medically significant bites.
Look for stripes first—smooth green snakes have no stripes or patterns, just uniform bright green coloration. Both garter snake species display prominent longitudinal stripes running the length of the body. Body shape also differs, with smooth green snakes being much more slender with a barely distinct head, while garter snakes have robust bodies and wider heads clearly separated from the neck.
Smooth green snakes occupy only three isolated regions in South Dakota: the Black Hills, extreme northeastern counties, and extreme southeastern areas. If you live outside these regions, any green-colored snake you encounter is likely a garter snake with greenish coloration rather than a true smooth green snake.
Simply leave it alone and allow it to move on naturally. All green and greenish snakes in South Dakota are harmless and beneficial, feeding on insects, slugs, and other small prey that many people consider pests. If the snake remains near a high-traffic area and you’re concerned, you can gently encourage it to move by using a long stick to guide it toward nearby vegetation, or contact a wildlife removal specialist for safe relocation.
Yes, all three species discussed are well-adapted to South Dakota’s harsh winters. They hibernate below the frost line in mammal burrows, rock crevices, or abandoned ant hills, often sharing these winter dens communally with other snakes. Plains garter snakes show exceptional cold tolerance and may even emerge briefly on warmer winter days.
