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.

Pit Vipers: The Venomous Masters of Infrared Detection

Rattlesnakes, Copperheads, and Cottonmouths are among the most well-known members of the venomous Crotalinae subfamily, also referred to as pit vipers. These snakes are equipped with unique adaptations that make them exceptional hunters.

What Makes Pit Vipers Unique?

Infrared-Sensing Pits:
A defining feature of pit vipers is the deep facial pit between their nostril and the eye on each side of their head. These specialized infrared-detecting organs allow pit vipers to sense heat emitted by prey. This adaptation enables them to:
- Detect body heat from up to 1 meter away.
- Strike prey with pinpoint accuracy, even in complete darkness.
Triangular Heads and Vertical Pupils:
- Head Shape: Pit vipers are recognized by their distinct triangular-shaped heads, which house their venom glands.
- Eyes: They have vertical elliptical-shaped pupils.
Venomous Fangs:
Pit vipers have hollow fangs connected to venom glands. These fangs fold back against the roof of their mouth when not in use.

Ecological Importance

Pit vipers play a crucial role in maintaining ecosystem balance by controlling rodent populations. Despite their fearsome reputation, these snakes are vital to the health of many habitats.

Eastern Copperhead (Agkistrodon contortrix)

The Eastern Copperhead is a pit viper native to the eastern United States.

What Do Eastern Copperheads Look Like?

Size	*Adults range from 20 to 37 inches (50 to 95 cm) in length.
Coloration	Reddish-tan to grayish-tan bodies. Overlaid with dark brown, hourglass-shaped markings. *Heads are dark coppery brown, giving them the name “Copperhead.”
Body Shape	Stout and heavy-bodied snakes. As with all pitvipers, their heads are triangular and appear oversized in relation to their necks.
Conservation Status:	*Endangered Species in Iowa

Taxonomy of Iowa’s Eastern Copperhead Snakes

Copperhead snakes which are found in southeastern Iowa are now recognized as the Eastern Copperhead (Agkistrodon contortrix).

In the past, Copperhead snakes were classified into different subspecies, including the Northern Copperhead, Southern Copperhead, and Osage Copperhead. However, recent DNA studies revealed minimal genetic differences between them. As a result, these subspecies were combined into a single taxonomic group under the Eastern Copperhead name.

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.

How Dangerous are Eastern 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.

Rattlesnakes of Iowa

Rattlesnakes are pit vipers. See the description of pit vipers above.

What Iowa’s rattlesnakes have in common with most other rattlesnake species is their rattle.

Most rattlesnakes have a rattle at their tail’s end, comprised of hollow, loosely interlocked keratinous scales.
Normally, a rattlesnake adds a new segment to its rattle each time it sheds its skin.
An agitated rattlesnake rapidly vibrates its tail, causing the segments of its rattle to vibrate together, creating a buzzing or rattling sound.
Not all Iowa’s rattlesnakes rattle before they strike. Sometimes, they lose their rattles due to injury, and sometimes, they choose not to rattle.

Western Massasauga Rattlesnakes (Sistrurus tergeminus)

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.

Size	*Adult Western Massasaugas average 17 to 39 1/2 inches (43 to 100 cm) long.
Coloration	A row of large, rounded, dark brown spots run down their spine. They have three smaller rows of spots down each side. *Sometimes, the larger dorsal spots connect with the side spots, forming a large solid blotch.
Dorsal Spots	A row of large, rounded, dark brown spots run down their spine. They have three smaller rows of spots down each side. *In some cases, the larger dorsal spots connect with the side spots, forming a large solid blotch.
Head	*A dark stripe on each side of their face and across their eye.
Conservation Status	*Endangered Species in Iowa

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.

Eastern Massasauga Rattlesnakes (Sistrurus catenatus)

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

Size	*Adult Eastern Massasaugas average 22 to 30 inches (55 to 75cm) long.
Coloration	Their base color is light grey. Some melanistic snakes are almost entirely black in color.
Dorsal Spots	A row of large, rounded, blackish-brown spots run down their spine. They have three smaller rows of spots down each side. *In some cases, the larger dorsal spots connect with the side spots, forming a large solid blotch.
Head	*A dark stripe on each side of their face and across their eye.
Conservation Status	*Endangered Species in Iowa

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.

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?

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

Also see: Wild Cats in Iowa – Krebs Creek

Timber Rattlesnake (Crotalus horridus)

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.

What Do Timber Rattlesnakes Look Like?

Size	Average length: 36 to 60 inches (0.91 to 1.52 m). Rare cases reported: Up to 7 feet (2.13 m).
Coloration	General base color: Yellowish-brown to grey-brown. Chevron pattern: Dark brown to black chevrons on their back and sides against a lighter base color. Back stripe: Rusty to reddish stripe running down their back. Tail color: Dark brown or black.
Melanistic Variation	Some timber rattlesnakes exhibit a dark, melanistic color morph. These snakes can appear almost entirely black. *The tail is darker than the rest of the body in this morph.
Behaviors	These snakes are excellent climbers. In fact, timber rattlers have been found in trees at heights of more than 80 feet. The 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.
Conservation Status	*They are the most prominent venomous snake in Iowa.

Where Do Timber Rattlesnakes Live in Iowa?

Timber Rattlesnakes live along the Mississippi River and some areas in the southern third of the state. 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.

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.

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

Prairie Rattlesnake (Crotalus viridis)

What Do Prairie Rattlesnakes Look Like?

Size	Adults typically measure about 3.3 feet (100 cm) in length. The longest recorded specimen was just under 5 feet (151.5 cm) long.
Coloration	*Their base color varies and can be tan, olive green, or brown.
Dorsal Spots	*Brown blotches with darker borders are present on their bodies.
Head	They have a triangular-shaped head with pit sensory organs on either side. A light stripe runs diagonally from the back of each eye to the jaw. *Another stripe extends diagonally from below the eye to the corner of the mouth
Behavior	*Primarily ground-dwelling but occasionally climbs shrubs, bushes, or trees.
Conservation Status	They are an endangered species in Iowa. The Iowa DNR classifies them as a species of greatest conservation need.

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.

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.

Iowa’s Venomous Snakes in Winter: Insights into Brumation

During winter, Iowa’s snakes, like all reptiles, enter a dormant state called brumation—a hibernation-like period. Because snakes are ectothermic (cold-blooded) and cannot regulate their body temperature internally, they slow their metabolism and become inactive during the colder months.

Brumation Habits

Solo vs. Communal Brumation: Some snakes brumate alone, while others gather in communal dens. For example, Eastern Copperheads and Timber Rattlesnakes often share dens, which may house up to 60 snakes.
Mixed-Species Dens: Interestingly, these dens can include non-venomous species. It’s not uncommon to find Black Rat Snakes or Eastern Black Racers sheltering alongside venomous snakes.

Regional Variations

Snakes may only seek shelter in warmer areas on the coldest winter days. They might not enter full brumation due to milder conditions.

Where Snakes Spend Winter

Snakes seek out protected spots to brumate, such as:

Rock crevices
Hollow logs
Fissures on rocky hillsides

They often choose south-facing slopes because these areas receive more sunlight, providing additional warmth during winter.

This natural adaptation allows Iowa’s venomous snakes to survive the winter and re-emerge when temperatures rise.

Avoiding Snake Bite

Many bites happen when someone accidentally steps on or near the snake. With rattlesnakes, you might hear a rattle that tells you that you’re getting too close, but then again, you might not. To stay safe in snake habitats, always watch where you step and where you place your hands.

Another common cause of snake bite is attempts to capture or kill a snake. Remember, venomous snakes can strike instantly, delivering a potentially life-threatening bite. The safest approach is to keep a safe distance and leave them alone.

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.

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.

Conclusion

Iowa’s venomous snakes play a critical role in the state’s ecosystems despite their intimidating reputation. Understanding their habitats, behaviors, and ecological importance not only fosters appreciation for these species but also promotes safety for those venturing into snake-prone areas. By following precautions, respecting their space, and knowing how to respond in the rare event of a bite, you can safely enjoy Iowa’s natural beauty while contributing to the conservation of these remarkable reptiles. Stay informed, stay alert, and coexist harmoniously with Iowa’s wildlife.