Colorado has four different rattlesnake species. According to Tina Jackson, who is the Species Conservation Coordinator at Colorado Parks & Wildlife, the only venomous snakes in the Centennial State are rattlesnakes. See
From the standpoint of dangerous snakes that have the ability to do harm to humans, she is correct. However, there are 6 more venomous snake species living in Colorado that are not rattlesnakes. While these snakes are not dangerous to humans, they are venomous non the less. Their venom helps them to subdue their prey.
Colorado is also home to 5 species of garter snakes. Garter snakes are a gray area because, until recently, we believed that they were non-venomous. However, in the early 2,000s, scientists discovered that garter snake saliva contains a mild neurotoxic venom. However, garter snakes are incapable of seriously injuring humans. Their teeth are too small to break the skin in most instances. Also, the most serious complication from garter snake human envenomation is some localized irritation to the skin.
Colorado is also home to the Western Hognose snake. Like with garter snakes, although the western hognose snake is not dangerous to humans, it is a rear-fanged snake and is mildly venomous.
Colorado snakes that imitate venomous snakes
There are a handful of species of snakes in Colorado that imitate coral snakes, such as the king snake and milk snake. However, they are non-venomous.
Also, the Great Basin gopher snake resembles a rattlesnake in coloration, and they will flatten out their heads and vibrate their tails when they are threatened to more closely resemble a rattlesnake. However, these snakes are non-venomous. what’s more, Great Basin gopher snakes actually prey on rattlesnakes sometimes.
Northeastern and southeastern Colorado are home to the northern water snake (Nerodia sipedon). Northern water snakes are sometimes mistaken for venomous cottonmouths. However, they are not venomous. Although northern water snakes are not venomous, their saliva does contain an anticoagulant. This could potentially make the bite area from one of these snakes difficult to heal.
The garter snake species that live in Colorado are the following.
- Common garter snake ( Thamnophis sirtalis)
- Blackneck garter snake ( Thamnophis cyrtopsis)
- Western Ribbon Snake ( Thamnophis proximus)
- Plains Garter Snake ( Thamnophis radix)
- Western Terrestrial Garter Snake ( Thamnophis elegans)
Common Garter Snake (Thamnophis sirtalis)
The common garter snake, which is sometimes called the red-sided garter snake, is distributed throughout most of North America. Interestingly, these snakes come in a wide range of colors, which includes green, blue, yellow, gold, red, orange, brown, and black. What’s more, they grow up to about 4 ft long. However, most stay smaller than that. Most of them have vertical stripes that are yellow to brown over a darker background. Common garter snakes are known to secrete a foul-smelling fluid from postanal glands when handled.
Black-necked Garter Snake – (Thamnophis cyrtopsis)
The black-necked garter snake is native to the southwestern United States, Mexico, and Guatemala. These snakes are olive-colored with contrasting lateral stripes. They have a stripe down the center of their back that is typically more vivid orange or yellow the closer it extends towards their head. They also have a whiteish or cream-colored stripe on each side. Additionally, they have black neck patches on either side of the dorsal stripe at the back of their head, which is bluish-grey. They also have black stripes which surround the cream-colored scales on their upper and lower jaws. The largest black-necked garter snakes are up to 42 inches long.
Western Ribbon Snake ( Thamnophis proximus)
The western ribbon snake is a sub-species of garter snake that is endemic to the western United States, Mexico, and Central America. In Colorado, the western ribbon snake is only located in a very small area in the southeastern portion of the state.
Plains Garter Snake ((Thamnophis radix)
The Plains Garter snake is a garter snake sub-species that is endemic to the central United States, from Texas north to Canada. They are mainly greyish green in color with a distinctive yellow stripe that stretches from their head to their tail. Plains Garter snakes live from Colorado’s front range east through the remainder of the state.
Western Terrestrial Garter Snake – (Thamnophis elegans)
The Western terrestrial garter snake inhabits western North America. It is a very phenotypically variable species. Most of them have a white, yellow, or light orange stripe along their top, along with two stripes of the same color, one on each side. Most of the time, they have red or black spots between their dorsal stripe and their side stripes. Due to their variability, these snakes even pose a problem for experienced herpetologists to identify at times. There are both coastal and inland varieties of this species. Obviously, the ones in Colorado are of the inland variety. Their diet is semi-aquatic and includes frogs, frog and toad larvae, leeches, and fish, along with terrestrial prey such as rodents, small reptiles, and insects.
Western terrestrial garter snakes live throughout Colorado, with the exception of the northeastern corner of the state.
Western Hognose Snake (Heterodon nasicus)
The western hognose snake, which is also known as the blow snake, the bluffer, or the faux viper, is a relatively short and stout-bodied snake. Their color pattern is variable, but most subspecies of this snake resemble a rattlesnake in coloration.
These snakes derive their common name from an upturned nose scale that gives their snout a long, hoglike appearance. As discussed earlier, although these snakes are not dangerous to humans, they are mildly venomous.
Western Hognose snakes in Colorado, live from the front range eastward. There is also an isolated population of these snakes in northwestern Colorado, in Moffat County.
There are four species of rattlesnakes in the U.S. state of Colorado. They are listed below:
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- Prairie Rattlesnake (Crotalus viridis viridis)
- Midget-faded Rattlesnake (Crotalus concolor)
- Desert Massasauga (Sistrurus catenatus edwardsii)
- Western Massasauga (Sistrurus catenatus tergeminus)
Rattlesnakes are pit vipers. which means that they have triangular shaped heads and heat-sensing pit organs, which are located below and slightly in front of each eye. They also have vertical elliptical pupils, which make their eyes look similar to cat’s eyes.
In general, rattlesnakes have tan to dark olive-green skin that is mottled over with a darker brown color pattern.
The first thing people think about with regard to Rattlesnakes is their tails. When they are disturbed, they vibrate their tails. This makes a buzzing or rattling-type sound. Sometimes rattlers strike without rattling. Sometimes their rattles fall off. You must be aware of where you are placing your hands, walking, running, or sitting down. If you hear a rattling noise, do not move until you spot where it’s coming from. Otherwise, you may accidentally move into the snake, allowing it to strike you.
If you are going to be hiking in rattlesnake country, it would be a good idea to wear snake boots or snake gaiters to protect your ankles from being bitten by a snake.
Around 200 people in Colorado suffer rattlesnake bites each year. See The vast majority of these are non-life threatening, due to most victims having access to prompt medical treatment. Sometimes though, even with medical treatment and anti-venom, rattlesnake bite victims die from their injuries.
The most recent fatal rattlesnake bite in Colorado occurred in 2022 when a 6-year-old boy was bitten southeast of Fort Carson, Colorado.
Prior to that, a 31-year-old man was bitten by a rattlesnake and fatally envenomated while hiking near Golden, Colorado.
The Prairie Rattlesnake grows anywhere from 3ft to 5ft long. They are tan-colored with varying colors of brown blotches covering their bodies. They have a distinguishing triangle-shaped head with pit sensory organs on either side. A light stripe runs diagonally from the back of its eye to its jaw, and another strip runs diagonally from below its eye to the corner of its mouth. Prairie Rattlesnakes are mostly ground snakes, but they occasionally climb into shrubs, bushes, or trees. Prairie Rattlesnake bites are both hemotoxic and neurotoxic.
The Prairie Rattlesnake is found throughout Colorado. Look for them in open prairies, semi-desert shrubland, open grasslands, sandhills, piñon-juniper forests, riparian zones, and woodland habitats up to 9,500 ft in elevation. See They may take up residence in prairie dog towns and live in appropriated prairie dog burrows.
Adult prairie rattlesnakes primarily feed on small mammals such as mice, rats, and prairie dogs. They also feed on lizards, small snakes, eggs, birds, and carrion.
A Prairie Rattlesnake bite’s signs and symptoms include extreme pain, blistering, swelling, nausea, and vomiting. The venom can impair blood coagulation and break down the red blood cells, leading to tissue necrosis, shock, and rarely multiple organ damage. Source
Midget-faded rattlesnakes are cream, brownish-grey, or a straw-like color. They are found in extreme west-central Colorado. This species is actually a subspecies of the western rattlesnake. They can grow to 20-30 inches in length. Males are usually longer and bigger than females. Rocky areas that have many places to hide are a normal habitat for the midget faded rattlesnake. This species bite can inject you with neurotoxic venom.
Other names for this snake are the Faded Rattlesnake and Yellow Rattlesnake.
A Midget-faded Rattlesnake has one of the most potent venoms in North America. See Its presynaptic neurotoxic bite’s signs and symptoms include extreme pain, blistering, swelling, nausea, and vomiting. The venom can impair blood coagulation and break down the red blood cells, leading to tissue necrosis, shock, and rarely multiple organ damage. Source
In Colorado, Midget faded rattlers live in the west-central portion of the state, in the Green River formation. This area comprises Moffat, Rio Blanco, Mesa, Garfield, Delta, and Montrose Counties.
Desert Massasauga rattlesnakes are smaller snakes that reach a body length of 21 inches. They have a pale gray body with dark brown blotches. They also have a dark stripe that goes from the side of the head and across the eye. This snake is given the nickname “buzztale” for its high-pitched rattle sound, which is different from other rattlesnakes. These snakes are found in the sandy areas of southeastern Colorado.
The venom of the Desert Massasauga rattlesnake is cytotoxic venom that destroys tissue. The cytotoxic venom contains digestive enzymes that disrupt blood flow and prevent blood from clotting. A bite to a human is rare. Most bites occur after someone deliberately handles them or accidentally steps on one. In Ontario, Canada, there are two cases of people dying from a not properly treated bite because the specific antivenom is not easily acquired.
In the Colorado Desert, Massasauga Rattlesnakes live in the arid grasslands in the southeastern part of the state. See
The Western Massasauga rattlesnake grows to a length between 14 – 36 inches. Their body is a light gray with dark brown blotches. They are similar to the Desert Massasauga but lighter in color. They also have a dark stripe that goes from the side of their face and across the eye. These snakes are found in the sandy terrain of southeastern Colorado.
It is given the nickname “buzztale” for its high-pitched rattle sound, which is different from other rattlesnakes.
The venom of the Western Massasauga rattlesnake is cytotoxic venom that destroys tissue. The cytotoxic venom contains digestive enzymes that disrupt blood flow and prevent blood from clotting. A bite to a human is rare. Most bites occur after someone deliberately handles them or accidentally steps on one. In Ontario, Canada, there are two cases of people dying from a not properly treated bite because the specific antivenom is not easily acquired.
In Colorado, Western Massasauga rattlesnakes live in Lincoln, Cheyenne, El Paso, Pueblo, Crowley, Kiowa, Otero, Las Animas, Prowers, Baca, and Bent Counties.
Symptoms of Venomous Snake Bites
Some of the symptoms you may experience when you suffer a venomous snake bite include:
- Discoloration in the area of the bite.
- Swelling in the area of the bite.
- Loss of muscle coordination.
- Tingling sensation in the area of the bite.
- Feeling nauseous.
- Having a faster heartbeat or rapid pulse.
What Should You Do If You Are Bitten?
If you think you or someone that you know or encounter has been bitten by a rattlesnake, time is precious because of the effects that the venom causes on the human body. It is important to seek medical attention immediately if you suspect that a rattlesnake or other venomous snake bit you. Take these first aid steps in the case that a rattlesnake or other venomous snake has bitten you or someone around you:
- Remain calm and limit your movements. Do not run. If you must hike back to a vehicle, do it in a calm, deliberate manner. Put as little stress on your heart as possible.
- Keep the area of the snake bite below the heart level and never above heart level. Keeping the bite below the heart level will reduce the venom’s flow while holding the bite above your heart level will increase the venom’s flow.
- Since the snake bite will swell, it is advised to remove all constricting items such as bracelets, watches, or rings because the area will most likely begin swelling.
- You can wash the bite area like you would any other wound with soap and water.
- You may cover the bite area with a moist dressing to reduce the swelling and some of the discomfort you or the person that has been bitten may be feeling.
- Get medical attention as soon as possible. If you or someone has a phone, call the hospital or ambulance to tell them a venomous snake may have bitten you so they can have the anti-venom ready to give you as soon as you arrive.
A person who a venomous snake has bitten may go into shock. If this happens, you should lay them flat and cover them with a blanket.
Many times after someone has been bitten by a poisonous snake; they will attempt to kill it to take it in to be identified. This is rarely a good idea. It’s potentially a good way to get bit again. Remember, a dead snake can still bite you. Also, consider, that severed snakeheads can still bite and envenomate and often do. If you have a phone, take a picture of the offending reptile. Otherwise, get started on your way to the nearest hospital.