Venomous Snakes of Iowa

There are five venomous snake species in the state of Iowa. Four of these are rattlesnakes. The fifth one is the Eastern Copperhead. In this article, we’ll list and describe each of these snakes. We’ll also tell you where you’ll most likely find them in the Hawkeye State.

Western Massasauga(Sistrurus catenatus tergeminus )

Eastern Massasauga(Sistrurus catenatus catenatus)

Eastern Copperhead (Agkistrodon contortrix)

Timber Rattlesnake(Crotalus horridus)

Prairie Rattlesnake (Crotalus viridis)

Pit Vipers

Rattlesnakes, Cottonmouths, and Copperheads belong to the venomous viperidae or pit viper family. Pit vipers have a heat-sensitive pit between the nostril and eye on both sides of the head. These pits are actually specialized organs that detect infrared radiation from prey animals. Pit organs enable pit vipers to strike their prey precisely, even in the dark. They are also able to detect body heat from about 1 meter away.

These snakes also have a triangular-shaped head attached to a relatively thin neck. Furthermore, the pupils of the eyes are vertical elliptical slits. This is a defining characteristic because a nonvenomous snake generally has round pupils.

Pit vipers have hollow fangs connected to venom glands. They use their fangs to inject venom into their prey. This venom immobilizes the prey, making it easier for the snake to consume. They primarily consume small mammals, reptiles, amphibians, and small birds. These snakes play an important role in maintaining balance in rodent populations.

Western Massasauga Rattlesnakes

Scientific Name:	Sistrurus tergeminus
Description:	Adult Western Massasaugas range between 17 to 39 1/2 inches (43 to 100 cm) long. Their body is light grey with dark brown blotches.
Habitat:	Open grassland areas and rocky hillsides.
Conservation Status:	Endangered Species in Iowa

Western massasaugas are divided into two subspecies. These are the prairie massasauga and the desert massasauga. It is the Prairie Massasauga that is found in Iowa. Adults grow between 17 and 39 1/2 inches (43 and 100 cm) long. Their body is a light gray with dark brown blotches. They also have a dark stripe on each side of their face and across their eye.

Where Do Western Massasaugas Live in Iowa?

If Western massasaugas still exist in Iowa, they are very rare. They are on the endangered species list. Any population of them will be in the southwestern corner of the state. The last recorded sighting was in 1984 in Mills County. Before that, there were three recorded sightings in 1941. These were also in southwestern counties.

How Dangerous Are Western Massasauga Rattlesnakes?

The venom of the Massasauga rattlesnake is cytotoxic. Cytotoxic venom destroys body tissue. Moreover, digestive enzymes in cytotoxic venom disrupt blood flow and prevent clotting. Massasauga bites to humans are rare. However, they do occur.

There are two documented deaths in Ontario from Eastern Massasauga envenomation. In each case, the victim did not receive antivenom in time. Source

Eastern Massasauga Rattlesnakes

Scientific Name:	Sistrurus catenatus
Description:	Adult Eastern Massasaugas range between 22 to 30 inches (55 to 75cm) long. Their body is light grey with dark brown blotches.
Habitat:	Swampy or marshy areas near lakes or streams.
Conservation Status:	Endangered Species in Iowa

The Eastern Massasauga rattlesnake grows to a length between 22 to 30 inches (55 to 75cm). Their body is a light gray with dark brown blotches. They also have a dark stripe on each side of their face and across their eye.  Some melanistic snakes are almost entirely black in color.

Massasaugas have a high-pitched rattle sound, which is different from other rattlesnakes. This is why they have the nickname Buzztail.

Where Do Eastern Massasauga Rattlesnakes Live in Iowa?

Eastern Massasaugas are an endangered species in Iowa. The most recent recorded sightings of this snake were in 2023. These were in Bremer and Muscatine Counties. This is in eastern Iowa. Source

What Do Eastern Massasauga Rattlesnakes Eat?

Eastern Massasaugas prey on smaller rodents such as mice and voles. They also eat frogs, toads, and small snakes.

How Dangerous Are Eastern Massasauga Rattlesnakes?

The venom of the Massasauga rattlesnake is cytotoxic. Cytotoxic venom destroys body tissue. Moreover, digestive enzymes in cytotoxic venom disrupt blood flow and prevent clotting. Massasauga bites to humans are rare. However, they do occur.

There are two documented deaths in Ontario from Eastern Massasauga envenomations. In each case, the victim did not receive antivenom in time. Source

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Also see: Wild Cats in Iowa – Krebs Creek

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Eastern Copperhead

Scientific Name:	Agkistrodon contortrix
Description:	Adult copperheads are 20 to 37 inches (50 to 95 cm) long. Their bodies are coppery brown overlayed with dark brown hourglass blotches.
Habitat:	Deciduous forests, river bottoms, and rocky wooded hillsides.
Conservation Status:	Endangered Species in Iowa

The Eastern Copperhead is a pit viper native to the eastern and mid-western United States.

Eastern Copperhead snakes have reddish-tan to grayish-tan bodies. Their bodies are overlaid with hourglass-shaped dark brown markings. Their triangular heads are proportionately large. The color of their head is dark coppery brown. This gives them the name “Copperhead.”

Copperheads are stout heavy-bodied snakes. Adult copperheads are 20 to 37 inches (50 to 95 cm) long.

Where Do Eastern Copperheads Live in Iowa?

The Eastern Copperhead is an endangered species in the Hawkeye State. In fact, they are the rarest snakes in Iowa, according to the Iowa Division of Natural Resources. But a few have been spotted in the southeastern Iowa in Davis, Lee, and Van Buren counties.

Eastern Copperhead Behavior

Copperheads have excellent camouflage coloration. It helps them blend in with leaf litter and other ground debris. Furthermore, they use camouflage as their number one defense mechanism. In other words, these snakes choose to lie perfectly still rather than flee most of the time.

For defensive behavior, they occasionally mimic the tail vibration of a rattlesnake. But, in most cases, they choose to lie perfectly still.

Most copperhead bites on humans occur when the person steps on or near the snake.

What Do Eastern Copperheads Eat?

Copperheads prey on a variety of species. Their menu includes small rodents, amphibians, small birds, snakes, lizards, and large insects.

Winter Dormancy

Snakes do not tolerate the cold weather in the winter months very well. They are ectotherms, which means they cannot regulate their body temperature internally. Physiologically, ectotherms cannot hibernate. Yet, they go into a state of suspended animation called brumation for up to 6 months out of the year.

Copperheads winter underneath rocks, in hollow logs, and in fissures on rocky hillsides. An individual might brumate alone in some parts of their range. But copperheads tend to be social. In some areas, they congregate together in a communal den with other snakes.

In hilly terrain, south-facing slopes capture more radiant warmth from the sun. So, that is where these den sites are generally located. Rock ledges with deep cracks are likely denning sites.

The other snakes they den with are not necessarily just copperheads. Sometimes, they share their dens with other types of snakes. You may find a Timber Rattler, or Western Black Rat Snake, sharing the same den with copperheads. These wintertime dens may hold up to 60 snakes.

How Dangerous are Copperheads?

A Copperhead can bite and inject venom when they are newly born. Like most pit vipers, they have hemotoxic venom. 

Most copperhead bites are not life-threatening. On the other hand, any bite from this snake is a medical emergency and should be treated as such. If a copperhead bite victim gets medical help fast, they have a better chance of a positive outcome.

Copperhead bites can cause intense pain, shock, and swelling. Their bites also have the potential to cause blood in urine, tissue damage, and kidney failure.

An interesting study has found that Copperhead venom contains a protein called contortrostatin. Contortrostatin has been found to stop the growth of cancer cells in mice.

Timber Rattlesnake

Scientific Name:	Crotalus horridus
Description:	Adult Timber Rattlesnakes grow between 36 and 60 inches (.91 to 1.52m) long. Their bodies are yellowish-brown with a dark chevron pattern. They also have a rusty stripe down their backs. Their tails are dark brown or black.
Habitat:	Timber Rattlesnakes prefer wooded areas and hillsides with rocky outcroppings.
Conservation Status:	They are the most prominent venomous snake in Iowa.

Timber Rattler and Canebrake Rattlesnake are both common names for the Timber Rattlesnake. Generally, in higher-elevation habitats, they are called Timber Rattlesnakes. On the coastal plain, though, they’re called Canebrake Rattlesnakes.

The average Timber Rattlesnake grows between 36 and 60 inches (.91 to 1.52m) long. However, there have been reports of them growing up to 7 feet (2.13m) long. See

These snakes vary in color. Their general base coloration is a yellowish-brown to grey-brown, though. They have a dark brown to black chevron pattern on their back and sides against a lighter base color. Moreover, they have a rusty to reddish stripe down their backs. They have a dark brown or black tail with a tan rattle on the end. There are also melanistic timber rattlers. These are dark and sometimes almost entirely black. In the dark color morph of these snakes, the tail is also darker than the rest of the snake’s body.

Where Do Timber Rattlesnakes Live in Iowa?

The Timber Rattlesnake is the most common type of venomous snake in Iowa. These snakes are found in central and southeastern Iowa. They also live along the Mississippi River. They’re also one of two venomous snake species that live in the vicinity of Des Moines. True to their name, Timber Rattlesnakes prefer wooded areas. They also live on hillsides with rocky outcroppings.

What Do Timber Rattlesnakes Eat?

Timber rattlers prey on small mammals such as mice, rats, squirrels, chipmunks, and bats. They also eat small birds, other reptiles, and amphibians.

These snakes are excellent climbers. In fact, researchers have found timber rattlers in trees at heights of more than 80 feet. Source

Experts have proven that timber rattlesnakes help control Lyme disease. This is because as they consume rodents, they’re also consuming ticks. A timber rattler will consume 2,500 to 4,500 ticks per year, depending on the location. See

Winter Dormancy

As we discussed in the section on copperheads, snakes brumate in the winter. Brumation is a reptile’s version of hibernation.

Timber Rattlesnakes make wintertime dens in sheltered spots. They den underneath rocks and logs, as well as in fissures in rocky hillsides. An individual Timber Rattler might brumate alone in some parts of their range. But in other areas, they congregate in dens with other snakes through the winter.

Dens are usually placed on slopes facing south because they get more warmth from the sun. They don’t always share their dens only with Timber Rattlers. Sometimes, they share their dens with other species of snakes. These might include Copperheads, Black Rat Snakes. These wintertime dens may hold up to 60 snakes.

How Dangerous Are Timber Rattlesnakes?

Timber Rattlesnakes are among the most dangerous snakes in North America. This is due to their long fangs and high venom yield. 1% to 10% of untreated Timber Rattlesnake bites result in a fatality.

The good news is that Timber Rattlesnakes are relatively docile. They will only choose to bite defensively as a last resort. Also, 40% to 60% of the time, they produce dry bites. In other words, although their fangs penetrate the body, they do not inject any venom. Source

These snakes produce hemotoxic venom. Timber Rattlesnake bites sometimes cause serious complications. These include shock, seizures, coma, internal bleeding, and deep tissue damage. Source

Prairie Rattlesnake

Scientific Name:	Crotalus viridis
Description:	Adult Prairie Rattlesnakes average 3.3 feet (100 cm) in length. They are tan-colored with varying colors of brown blotches covering their bodies.
Habitat:	Look for Prairie rattlesnakes in open prairies, grasslands, and forested areas.
Conservation Status:	They are an endangered species in Iowa. The Iowa DNR classifies them as a species of greatest conservation need.

Adult Prairie rattlesnakes average around 3.3 feet (100 cm) in length. The longest recorded specimen measured just under 5 feet (151.5 cm) 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 the eye to the jaw. Another strip runs diagonally from below the eye to the corner of the mouth.

Where Do Prairie Rattlesnakes Live in Iowa?

Prairie Rattlesnakes are on the endangered species list in Iowa. They live in western Iowa along the Missouri River. The last recorded sighting was in the Loess Hills in western Plymouth County in 2017. Source

Prairie Rattlesnake Behavior

Prairie rattlesnakes are mostly ground snakes. But they occasionally climb into shrubs, bushes, or trees.

Prairie Rattlesnakes brumate in communal dens. But their hunting grounds extend as far as seven miles from their dens in the summertime. In the warmer months, prairie rattlers might shelter in old mammal burrows. But in the fall, they will return to their communal dens.

How Dangerous Are Prairie Rattlesnakes?

Prairie rattlesnake venom is a mix of hemotoxins and myotoxins. Furthermore, according to some literature, it also has neurotoxins.

Prairie rattlesnake bites can have serious effects. The venom can cause severe pain. It may also induce shock, making the victim feel weak and disoriented. Swelling, blistering, and inflammation can occur at the bite site. Their venom can also damage red blood cells and impair blood clotting. In severe cases, the bite may result in severe tissue damage. There is also a risk of harm to internal organs. Source

Symptoms of Venomous Snake Bites

Some of the symptoms you may experience when a venomous snake bites you 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 or someone you are with has suffered a venomous snakebite, time is of the essence. Because the sooner a victim receives antivenom, the less chance the venom in their body has to cause harm. In other words, it is important to seek immediate medical treatment.

Do not attempt to kill the snake for identification purposes. This gives the snake a chance to bite you again. 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.

First Aid for Snake Bite Victims

• Remain calm and limit your movements. Do not run. If you must hike back to a vehicle, do it calmly and deliberately. Put as little stress on your heart as possible.
• Keep the area of the snake bite below the heart level and never above the heart level. Keeping the bite below the heart level will reduce the venom’s flow. However, holding the bite above your heart level will increase the venom’s flow.

• Remove all constricting items such as bracelets, watches, or rings before swelling occurs.
• Remember that using a cold compress on a venomous snake bite is not advisable. The cold may cause the local blood vessels to constrict and spread the venom faster.
• You can wash the affected area like any other wound with soap and water.
• You may cover the bite area with a moist dressing to reduce the swelling.

• Get medical attention as soon as possible. Call the hospital to tell them a venomous snake has bitten you. So they can have antivenom ready to give you when you arrive.
• A person whom a venomous snake has bitten may go into shock. If this happens, lay them flat and cover them with a blanket.

Dressing for Snake Country

• High-top leather boots and long pants are both wise ideas.
• Also, wear loose-fitting denim. If there’s a gap before the snake’s fangs touch your skin, your chances of being envenomated are lower.
• In the absence of high-top leather boots, some people wear snake gaiters.