There are A LOT of snakes in Colorado!
And what’s interesting is that they are all incredibly unique and have adapted to fill many habitats and niches.
You’ll see that the snakes that live in Colorado are very different from each other.
For example, some species are venomous, while others use constriction to immobilize their prey. Or the fact that certain snakes are rarely seen because they spend most of their time underground, but others are comfortable living EXTREMELY close to humans.
Today, you’re going to learn about the 14 types of snakes in Colorado!
#1. Prairie Rattlesnake
- Crotalus viridis
- Adults typically range between 3.3 and 5 feet in length.
- Coloration is highly variable and can be greenish-gray, olive green, greenish-brown, light brown, or yellow. All variations have dark blotches on the body that turn into rings near the tail.
- Broad triangular head, elliptical pupils, heat-sensing pits between the eyes and nostrils, and a tail rattle.
These venomous snakes can be found in Colorado in open prairies, grasslands, semi-desert shrublands, and forested environments. They can even be found at elevations up to 9500 feet!
The Prairie Rattlesnake hibernates during the winter, often in communal dens. These dens are typically rock crevices, caves, or old mammal burrows. Individual snakes return to the same den each winter and migrate up to seven miles to their hunting grounds in the spring.
When they feel threatened, these snakes freeze to use their camouflage to avoid detection. They may also quietly crawl away to cover. If approached, they may coil and rattle their tail as a warning before striking. Their potent venom has both hemotoxic and neurotoxic properties, and although rare, can be fatal to an adult human.
Prairie Rattlesnakes are listed on the ICUN Red List as a species of least concern. However, they are considered threatened and declining in parts of their range. In addition, they have faced pressure from habitat fragmentation and hunting.
#2. Western Massasauga
- Sistrurus tergeminus
- Adults range from 14 to 36 inches in length.
- Coloration is gray to light brown with dark brown blotches on the back.
- Thick body, large triangular head, heat-sensing pits between the eyes and nostrils, elliptical pupils.
- Being rattlesnakes, look for the rattle at the end of their tail.
The Western Massasauga is a rattlesnake and one of the smallest venomous snakes in the country! They primarily inhabit grassland habitats but can also be found in open sagebrush prairie, rocky hillsides, prairie hillsides, open wetlands, and grassy wetlands.
Western Massasauga Range Map
These snakes are secretive and not often seen in Colorado.
When detected, they often freeze rather than rattle. However, when they do rattle, Western Massasaugas make a distinctive sound. Their rattle is significantly higher pitched than larger rattlesnakes and has earned this small snake the nickname “buzz tail.”
Though their venom is highly potent, the small quantity they deliver makes their bites much less likely to be fatal in humans compared to larger venomous snakes. However, you still need to respect them as their venom is hemotoxic and will cause localized swelling, extreme pain, and necrosis. Medical attention should be sought immediately if bitten!
#3. Northern Watersnake
- Nerodia sipedon sipedon
- Adults range from 24 to 55 inches in length.
- Coloration is pale grey to dark brown with reddish-brown to black bands.
- Large adults become darker with age and appear almost plain black or dark brown.
- Females tend to be larger than males, and coloration is most vivid in juvenile and wet individuals.
This species is the largest snake you will see in the water in Colorado!
Northern Watersnakes prefer slow-moving or standing water like ponds, lakes, vernal pools, marshes, and slow-moving rivers and streams. They’re most often seen basking on rocks or logs in or near the water.
Northern Watersnake Range Map (Yellow area below)
Credit: Virginia Herpetological Society
These snakes primarily feed on fish and amphibians by hunting along the water’s edge and shallow water during the day. They grab their prey and quickly swallow while it’s still alive!
While non-venomous, they can deliver a painful bite!
Their saliva contains a mild anticoagulant that can cause bites to bleed, making the injury appear worse. These important defense mechanisms help water snakes survive predators such as raccoons, snapping turtles, foxes, opossums, other snakes, and birds of prey.
#4. Red-sided Garter Snake
- Thamnophis proximus parietalis
- Normally dark green to black, but color varies.
- Three yellow stripes; one down the back and one down each side.
- As the name suggests, red or orange bars run along their sides between the yellow stripes.
- Subspecies of the Common Garter Snake.
Like other garter snakes, they are habitat generalists. Look for them in Colorado everywhere, including forests, shrublands, wetlands, fields, and rocky areas. Their favorite foods include frogs, earthworms, and leeches! YUM! 🙂
In some areas, after emerging from hibernation, there are not enough females for all the males. In these cases, “mating frenzies” occur, and dozens and dozens of these snakes can be found together.
To survive colder months, Red-sided Garter Snakes have to hibernate BELOW the frost line. Depending on the area they are located in, it can be hard to find suitable locations. So the few adequate hibernation dens can shelter hundreds, even thousands, of snakes! To see an example, watch the video below:
#5. Terrestrial Garter Snake
- Thamnophis elegans
- Adults range from 18 to 41 inches in length.
- Most adults have three yellow, light orange, or white stripes; one down their back and two down their sides.
- Coloration is widely variable. Individuals may be brownish or greenish. Some have red and black spots between the stripes, and occasionally all black individuals are found.
This snake can be difficult to identify in Colorado!
Even trained herpetologists have issues! Its coloration varies widely, and there are believed to be 6 subspecies, although scientists still debate this.
Terrestrial Garter Snakes occupy various habitats, including both grasslands and forests. They can even be found in mountainous areas up to 13,000 feet above sea level. As the name suggests, they’re primarily found on land. But interestingly, these garter snakes are great swimmers!
This species is the only garter snake in Colorado with a tendency to constrict prey! Most garter snakes grab their prey quickly and just swallow, rubbing their prey against the ground if necessary.
Terrestrial Garter Snakes aren’t aggressive or dangerous, but they do possess mildly venomous saliva! It can cause a muscle infection or even kill some muscle tissue. Most bites on humans just cause pain and some swelling.
#6. Plains Garter Snake
- Thamnophis radix
- Adults average 36 inches in length.
- Coloration is gray-green with a distinctive orange stripe down the back and a greenish-yellow stripe down each side.
- Distinct light yellow spots on the very top of the head!
Plains Garter Snakes are almost always found in eastern Colorado in prairies and grasslands near freshwater sources. They have a fairly large population and adapt well to human-modified landscapes. You may spot them near abandoned buildings, trash heaps, or vacant lots.
This species is considered one of the most cold-tolerant of all snakes! In fact, they will even come out of hibernation on warmer winter days.
Plains Garter Snakes feed primarily on earthworms, slugs, and small amphibians. However, they have also been observed preying on small mammals and birds, including the Eastern Meadowlark and Bank Swallow.
#7. Black-necked Garter Snake
- Western Black-necked Garter Snakes are dark olive with an orange-yellow stripe down the back and a yellow to white stripe down each side. It can be up to 42 inches long.
- Eastern Black-necked Garter Snakes are smaller and only grow up to 20 inches in length. They have a checkered pattern of black and yellow on their body, between their three stripes.
- Both subspecies have a gray head, contrasting strongly with the body. In addition, there is a dark blotch on each side of the neck.
This species is found in many habitats, including desert scrub, plains, arid grasslands, and pine-oak woodlands. They’re almost always associated with water sources such as streams, ciénegas, and cattle tanks.
There are two subspecies of this snake: the Western AND Eastern. They look different (see photo above), but they also behave uniquely. The Western subspecies (Thamnophis cyrtopsis cyrtopsis) are water snakes and most often found in the water. The Eastern (Thamnophis cyrtopsis ocellatus) subspecies prefers to live on DRY LAND very close to water.
The Black-necked Garter Snake’s preferred prey is frogs, toads, and tadpoles, including poisonous species like the Sonoran Desert Toad. However, they have been known to feed on a wide range of other prey, including earthworms, skinks, salamanders, crustaceans, and birds.
#8. Speckled Kingsnake
- Lampropeltis holbrooki
- Adults are typically 36 to 48 inches in length.
- Coloration is shiny black with small yellow, yellowish-green, or white specks, one in the center of almost every dorsal scale though the pattern of the speckles varies by individual.
- The underside is white or yellow with clusters of black checkers and is sometimes more black than white.
The Speckled Kingsnake’s unique appearance resulted in the nickname “salt and pepper snake.” Look for them in fields along the forest’s edge, prairies, grasslands, stream valleys, pastures, and roadside ditches.
Speckled Kingsnake Range Map
These snakes are rather secretive and hard to find in southeast Colorado!
In addition, they’re primarily nocturnal. As a result, they’re most frequently spotted crossing roadways in the morning or evening.
Like other kingsnakes, this species is a constrictor, which means they use their coils to asphyxiate their prey before consuming it. They feed on a wide variety of prey, including rodents, birds, bird eggs, reptiles, reptile eggs, frogs, and other snakes, including venomous species. SEE THE VIDEO BELOW! 🙂
Speckled Kingsnakes are generally quite docile and are often kept as pets. However, if disturbed, they may shake their tail, release a foul-smelling musk, and strike if grabbed. Sadly this species is considered threatened in parts of their range.
#9. Western Milksnake
- Lampropeltis gentilis
- Adults typically range from 15 to 34 inches in length.
- Coloration is whitish, black, and reddish or orange bands, with the reddish-orange bands being bordered by black.
- The snout is blackish and sometimes features white flecking, and the underside may have extensions of the bands or be more whitish.
Western Milksnakes are found in Colorado in open sagebrush, grasslands and are occasionally seen in suburban areas. They’re a secretive species frequently found under objects like rocks, logs, boards, and other debris.
Western Milksnake Range Map
Because of their coloration, they are often confused with venomous coral snakes. But luckily, there’s an easy way to tell the difference. Just remember this rhyme:
“If red touches yellow, you’re a dead fellow; if red touches black, you’re all right, Jack.”
These snakes aren’t picky about food and feed on small mammals, birds, bird eggs, other snakes, lizards, reptile eggs, and occasionally, worms and insects. They actively hunt down their prey and use their coils to constrict the life out of them.
Though they’re usually docile when handled, Western Milksnakes do exhibit strong defensive behaviors when disturbed. You can expect them to vibrate their tail (like a rattlesnake), and they may even rear up and strike!
#10. Great Plains Ratsnake
- Pantherophis emoryi
- Adults range from 36 to 60 inches long.
- Coloration is light gray or tan with dark gray, brown, or green-gray blotching down its back.
- A spear-shaped mark on the head and stripes on the sides of the head that meet to form a point between the eyes.
- Also sometimes called Emory’s Ratsnake, Brown Ratsnake, or Chicken Snake.
Great Plains Ratsnakes are found in Colorado in open woodlands, rocky, wooded hillsides, semi-arid regions, and agricultural areas. Being nocturnal, they are hard to find and spend most of their days in old mammal burrows or under rocks, logs, boards, and other cover objects.
This species prefers to prey on rodents but may also consume small birds, lizards, and frogs. They are also known to eat bats and are sometimes found near caves hunting them! Like other rat snakes, they’re constrictors and use their strong coils to suffocate prey before eating it.
When disturbed, the Great Plains Ratsnake curls up and vibrate its tail which sounds remarkably like a rattlesnake when done in dry leaf litter. Though they’re considered non-aggressive and docile, they may strike if grabbed.
#11. Smooth Greensnake
- Opheodrys vernalis
- Adults are SLENDER and typically range from 14 to 20 inches in length.
- Coloration is uniformly light green with a yellow or white underside and a red tongue with a black tip.
- Juveniles may be olive-green, blue-gray, or even brown until they shed their skin for the first time.
Also called Grass Snakes, these bright green snakes can be found in marshes, meadows, pastures, savannas, open woods, and along stream and lake edges. They prefer moist areas near permanent water sources.
Smooth Greensnake Range Map
They prey almost exclusively on insects and spiders and don’t use constriction; instead quickly striking and swallowing their prey alive.
Smooth Greensnakes hibernate during the winter in Colorado, seeking shelter in old mammal burrows and abandoned anthills. They often hibernate communally with other small snakes. They emerge in the spring, typically in April, and are active until October.
Smooth Greensnakes rely on their EXCELLENT camouflage to avoid predators. They’re also agile and can flee quickly if they must.
- Pituophis catenifer sayi
- Adults are large and typically range from 4 to 6 feet in length.
- Coloration is yellow, beige, or light brown with large brown, black, or reddish blotching on the back and three sets of small blotches on the sides.
- Blotches may appear like bands near the end of the tail, and the underside is yellowish with black spots.
Bullsnakes are often seen in eastern Colorado in areas with high rodent populations.
So they’re common in places like prairie dog towns. But you can also find them in fields, grasslands, forest edges, savannas, and brushlands with sandy soils.
Bullsnakes are fast and can actively pursue prey in loose soil. They even use their prominent rostral (nose scale) to dig! Once they’ve captured their prey, they use their strong body to coil around and constrict their prey.
Despite being nonvenomous, these snakes act aggressively toward any threats. They often lift the front half of their body, hiss, and lunge at their attacker until they feel they can retreat.
Interestingly, their hissing can sound like a rattle! (see below!)
To accomplish this, the snake forces air through an extension of the windpipe, which has a piece of cartilage called an epiglottis that flaps back and forth, sounding very similar to a rattlesnake.
#13. Plains Hog-nosed Snake
- Heterodon nasicus
- Adults range from 15 to 39 inches in length.
- Coloration is varying shades of brown with darker brown blotches on the back, two alternating rows of smaller dark spots down the sides, and large longitudinal blotches on the sides of the neck.
- Enlarged rostral (nose) scale.
The Plains Hog-nosed Snake strongly prefers open sandy or gravelly habitats. They’re excellent burrowers and also use old animal burrows for hibernation and protection from hot temperatures.
These snakes are best-known for their impressive displays when disturbed!
When initially confronted, Plains Hog-nosed Snakes typically remain motionless or hide their head under their coils. They may also try to bury themselves or escape into a burrow.
However, if they’re further disturbed, they’ll spread their jaws and neck like a cobra and puff up their bodies. They may also hiss loudly and deliver false strikes with a closed mouth.
If these intimidating displays fail, the Plains Hog-nosed Snake will then twist as though they’re in pain, roll over on their back and play dead. They’ll be limp, open mouthed, and will remain this way even if picked up. They may also bleed from the mouth and cloaca, expel musk and fecal matter, and regurgitate recently eaten food.
If I saw one of these snakes do this display, I’d definitely leave it alone! But, unfortunately, they’re sometimes killed by people who are frightened by their cobra-like posture.
#14. Midget Faded Rattlesnake
- Crotalus oreganus
- Adult size varies widely over their range, with the largest individuals being 6 feet in length.
- Coloration is tan, yellow, and rarely pinkish. Faint oval blotches.
- Triangular head, heat-sensing pits between the eyes and nostrils, dark stripe with white borders that runs from the eye towards the jaw.
- Midget Faded Rattlesnakes are subspecies of the Western Rattlesnake.
This venomous snake, which is a subspecies of the Western Rattlesnake, can be found in western Colorado. They can be found in mountainous areas, woodlands, and grasslands. They also often occur in close proximity to humans.
Midget Faded Rattlesnakes may be active during the day or night and are often curled, waiting to ambush a variety of prey. They’ll feed on small mammals, birds, reptiles, and amphibians. They may also eat bird eggs, and young snakes often feed on insects.
Like other rattlesnakes, this species gives birth to live young. Healthy, sexually mature females can give birth to litters of up to 25 babies!
Do you need additional help identifying snakes in Colorado?
Try this field guide!
Which of these SNAKES have you seen before in Colorado?
Leave a comment below!
Also, if you enjoy this article, make sure to check out these other guides!