Colorado Garden Snakes: Identifying the Most Common Snakes in Your Garden

Prairie Rattlesnake

Written by Gail Baker Nelson

Updated: March 31, 2023

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Colorado’s stunning mountain vistas and activities make it a paradise for outdoorsy types. After exploring its many sights, you can finish a day of action with a soak in one of its many hot springs.

At least two dozen snake species call the state home, but you’re only likely to encounter a few in your garden. However, knowing which snakes are dangerous and which aren’t is sometimes difficult. To help, we’ve gathered the snakes you’re most likely to find under your azaleas and start with the venomous danger noodles.

The best advice you’ll ever receive about snakes is this: don’t touch them. There’s nothing worse than thinking it’s a bull snake and spending the next few days in the hospital after you discovered it was a rattlesnake.

1. Rattlesnakes (Crotalus sp.)

Midget Faded Rattlesnake showing rattle

Midget-faded rattlesnakes aren’t aggressive and try to hide before biting.

©Rusty Dodson/

Knowing how to tell the difference between a venomous and a nonvenomous snake is as important as knowing whether or not you can eat the plant you brought home. The state only has three venomous snakes, and they’re all rattlesnakes.

With such a unique warning system, it’s a wonder that anyone gets bit, right? Well, rattlesnakes don’t always rattle. Sometimes they don’t have time to rattle, but it’s also possible that it’s a juvenile snake, or that the snake thought its camouflage was so perfect that it would remain unseen.

Many scientists think rattlesnakes’ rattles evolved to help warn away the giant bison that once roamed North America. The snakes aren’t very fast, and hopefully, the sound alerts the bison to go around the snake instead of stomping on it. The rattle gives rattlesnakes their name. While the urban legend says that they get a new rattle for every year of their lives, that’s just a myth. Rattlesnakes get a new rattle link every time they shed, and if they’re eating well, that could be several times per year.

Pit vipers, like rattlesnakes, have some of the most advanced snake weaponry available in nature. Their fangs, which are a marvel of natural engineering, stay folded up in their mouths unless they need them. These natural hypodermic needles are attached to large venom glands. The fangs inject venom deeply into a victim, making the idea of sucking out the venom useless. Depending on the species, a pit viper can inject a massive venom dose – or none. Estimates indicate that 25-50% of all bites are dry.

The thing about having huge venom glands in its cheeks is that it gives the rattlesnake a big, triangular head, but they have relatively thin necks. It makes the snakes a bit easier to identify. Rattlesnakes have a fairly stout body-to-length ratio when compared with their nonvenomous neighbors – another identifying factor.

Types of Rattlesnakes in Colorado

Fortunately, there are only three rattlesnake species in colorado, and you’re likely to run into one across your yard.

Of the three, you’re most likely to encounter the prairie rattlesnake. It’s by far the most widespread of Colorado’s rattlesnakes, causing a fair number of bites every year. Rattlesnakes aren’t overly fond of being near people and typically avoid encounters wherever possible.

Prairie rattlesnakes are also called western rattlesnakes. This species is widespread across the prairie states from Canada to Mexico. It grows up to about five feet long and has dark blotches on its back that gradually become rings near the tail. The base color varies from light to dark tan, and they have dark strings that cross through their eyes diagonally toward the jaw.

Rattlesnakes (and pit vipers in general) have an expression that says, ”I live on the wrong side of the bed,” caused by an extra scale over their eyes. These snakes are primarily nocturnal but can be encountered during the day when temperatures are more comfortable.

2. Bull Snake (Pituophis catenifer sayi)

When threatened, the Bullsnake rears up in an S-shape, hisses and vibrates its tail to mimic the venomous rattlesnake.

When threatened, the bullsnake rears up in an S-shape, hisses, and vibrates its tail to mimic the venomous rattlesnake.


This nonvenomous snake is widespread across eastern Colorado, and most of North America from Colorado eastward. Its range extends from southern Canada to parts of Mexico. Bull snakes are also called gopher snakes, which scientifically speaking, they’re subspecies of.

The bull snake is one of the most common snakes you’ll encounter in eastern Colorado and is often mistaken for rattlesnakes. They usually measure four to six feet long but can reach eight feet. Heavier bull snakes can weigh nearly 10 pounds, but they are still not as big around as rattlesnakes.

Like many colubrid snakes, bullsnakes rattle their tails in leaves. The prevailing wisdom was that they are mimicking rattlesnakes. However, colubrids in Africa that have never seen a rattlesnake also exhibit this behavior, so that’s probably not the case. When threatened, bull snakes rear up to make themselves look as big as possible. Part of their defensive tactic is to strike and back away, hissing loudly all the while; they can also flatten their head to resemble a rattlesnake.

Their base color varies from yellow to gray or brown with darker blotches on their backs; sides have spotted patterns that extend most of the body length. Bull snakes’ blotching turns to a band as it reaches the tail, leading to many misidentifications. In addition, these snakes are highly variable in the wild many varieties have been found, including white and albino. However, unlike rattlesnakes, bull snakes have vertical bars along their lip scales and round pupils.

Identifying this one correctly can be a challenge, as they have similar coloration and tail banding to that of rattlesnakes. Bull snakes are more often misidentified as rattlesnakes than not. However, their head isn’t as big, and of course, they don’t have a rattle. Bull snakes are most likely found in open grasslands and prairies, but our yards and gardens with lovely cover plants are equally attractive. These snakes eat nearly anything they can overpower, and consume all types of small mammals like mice, rats, squirrels, and rabbits. They’re also excellent climbers and can devour a bird’s nestlings in less than 15 minutes.

3. Great Basin Gopher Snake (Pituophis catenifer deserticola)

gopher snake

Great basin gopher snakes are nonvenomous.

©Matt Jeppson/

Just like its close cousin, the bull snake, great basin gopher snakes are nonvenomous and common in western Colorado. Because they’re subspecies, they look very similar. Great basin gopher snakes have dark brown or black dorsal blotches connected to each other by narrow lines. Their heads are pointed with a creamy color with small irregular blotches. These snakes can grow to nearly six feet but typically average four and a half feet long.

Great basin gopher snakes occur in grasslands, deserts, woodlands, and riparian areas. They’re terrific swimmers and climbers, giving them the flexibility to move around and follow their prey. Like the bull snake, these snakes are very dramatic in their defensive behavior. They puff up their bodies, hiss loudly, and strike aggressively. They’re not quite as easy to confuse with rattlesnakes, but it happens.

4. Eastern Yellow-Bellied Racer (Coluber constrictor flaviventris)

A large and colorful Eastern Yellow-bellied Racer snake, Coluber constrictor flaviventris, coiled defensively with a large meal in its belly.

Eastern yellow-bellied racers are active hunters.

©Matt Jeppson/

Chances are, the only part of a racer you’ll see is its tail as it heads for the hills. These harmless snakes are fast, and we’re not surprised that their common name involves the word ”racer.” They prefer grassland habitats but will happily cruise through your garden on the lookout for anything to eat.

Like all snakes, they’re carnivores but aren’t picky about what type of critter they eat. Warm-blooded, cold-blooded, arthropod – you get the picture. The size of the prey they consume is primarily dependent upon the snake’s size, so the larger the snake, the larger the prey item.

Racers of all types are widespread and inhabit at least 40 states. While these snakes can be active most of the day, they reduce their active time to mid-morning and early afternoon during the hottest part of the summer. Eastern yellow-bellied racers are active hunters, and sometimes ”periscope” up to see over the grasses and rocks in the habitat.

The eastern yellow-bellied racer occurs throughout most of eastern Colorado and is a long, thin snake with a smallish head and large eyes. Juveniles have blotches that fade as they mature, becoming a solid color with a lighter-colored belly. Their dorsal color is typically olive or brown with a yellow to creamy-yellow colored belly, and they’ll grow up to about five feet long.

5. Garter Snakes (Thamnophis species and subspecies)

A common garter snake slithering in grass

All garter snakes have keeled scales, which means they have a ridge down the center.


These snakes are probably the most widespread group of snakes in North America. Garter snakes are small to medium-sized, rarely exceeding four feet in length. Until a few years ago, scientists believed that garter snakes weren’t venomous. However, they discovered that garter snakes and a few other species have small amounts of mildly venomous saliva and no effective delivery system. In prey animals, they bite and then have to let venom drip down into the wound. It’s harmless to people but sometimes causes local irritation.

Colorado has five garter snakes, and you can look at each snake and know that it’s a garter snake. Yet, each has differences that make them beautiful.

  • The common garter snake (Thamnophis sirtalis)
  • Black-necked garter snake (Thamnophis cyrtopsis)
  • Western ribbon snake (Thamnophis proximus)
  • Western terrestrial garter snake (Thamnophis elegans)
  • Plains garter snake (Thamnophis radix)

Of the five, you’re most likely to encounter the western terrestrial garter snake. This species usually has a dorsal stripe that’s yellow, light orange, or white, with matching stripes on each side of its body. Some have red or black spots between the stripes, but the species varies widely across the region.

Other Reptiles Found in Colorado

Colorado is home to a variety of lizards such as the Eastern collared lizard, diploid checkered whiptail, Roundtail horned lizard, and Many-lined skink. Skinks, in particular, resemble typical lizards, but they are characterized by their lack of neck and short limbs.

There are a total of 54 reptile species found in Colorado, including 5 turtles, 19 lizards, and 30 snakes. Among these species, some of the most noteworthy ones include the Colorado checkered whiptail and the Massasauga rattlesnake.

Here is a short list of other reptiles found in colorado:

Other Snakes

With over two dozen snake species, we can’t cover them all in one post. Here are a few others you may encounter:

  • Hognose snakes (Heterodon genus)
  • Speckled king snakes (Lampropeltis )
  • Common Kingsnake (Lampropeltis getula)
  • Variable ground snakes (Sonora semiannulata)
  • Lined snakes (Tropidochlonion lineatum)
  • Night snakes (Hypsiglena torquata jani)
  • Glossy snakes (Arizona elegans)
  • Great Plains rat snakes (Pantherophis emoryi)

Keeping Snakes Out of Your Garden

Snakes are found anywhere there is prey available. If you have a large yard or your property backs up against an undeveloped area, there are probably rodents and other prey. Some people prefer to not find snakes in their gardens, and if that’s you, there’s hope.

Keeping the majority of snakes out of your garden means you need to remove the hiding places for both the snakes and the prey. Rodents love hiding in wood and brush piles, and under leaf litter. Commercial snake repellant is available, but some experts say that it isn’t effective and simply removing hiding places is ideal.

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About the Author

Gail Baker Nelson is a writer at A-Z Animals where she focuses on reptiles and dogs. Gail has been writing for over a decade and uses her experience training her dogs and keeping toads, lizards, and snakes in her work. A resident of Texas, Gail loves working with her three dogs and caring for her cat, and pet ball python.

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