There are six venomous snakes in Missouri. Among these are four rattlesnake species, a cottonmouth, and a copperhead. Despite their menacing reputations, these snakes are important to the ecosystems in which they live. They are crucial to maintaining ecological balance because they help keep rodent populations in check.
Each of these snakes poses potential risks to humans. In fact, an average of 234 people are bitten by Missouri’s venomous snakes each year. Learning about these dangerous reptiles’ appearance, behavior, and habitats can help you navigate the Show Me State’s outdoors safely.
In this guide, you’ll learn how to recognize these snakes, their behaviors, and their habitats across Missouri. Whether you’re a hiker, camper, or simply curious about local wildlife, this comprehensive resource will equip you with the knowledge to stay safe and informed.
Pit Vipers: The Venomous Masters of Infrared Detection
Rattlesnakes, Copperheads, and Cottonmouths are among the members of the Crotalinae subfamily of the Viperidae family of venomous snakes, 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 serve as a check to 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 | It is one of the most common venomous snakes in Missouri. Found throughout the state. |
Taxonomy of Missouri’s Eastern Copperhead Snakes
Copperhead snakes are found across Missouri and are now recognized as a single species: the Eastern Copperhead (Agkistrodon contortrix).
In the past, these 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 Missouri?
The Eastern Copperhead is the most common venomous snake in Missouri. They are found statewide, with the exception of the northern border.
These snakes are found in rocky wooded areas and river bottoms. Copperheads occasionally make their way into urban areas as they follow waterways. They reside where leaf and plant debris or tall grass provide cover for them to hide.
Eastern Copperhead Behavior
Copperheads are dangerous because 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. Their camouflage helps them blend in with leaf litter and other ground debris.
When they feel threatened, 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 Copperheads Eat?
Copperhead snakes are opportunistic feeders. They eat insects, spiders, frogs, small animals, birds, and other reptiles.
How Dangerous Are Copperheads?
A Copperhead can bite and inject venom from the time 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. Prompt medical attention increases the chance of a good 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.
Northern Cottonmouth (Agkistrodon piscivorus)
Common names for the Northern Cottonmouth are water moccasins and stump-tailed moccasins.
What Do Northern Cottonmouths Look Like?
| Coloration | *Adults: Dark brown to black body with minimal markings. *Inside of the mouth: White, giving them the name “cottonmouth.” *Juveniles: More defined patterns, resembling a copperhead with darker bands that widen toward the belly and narrow along the back. *Inside is pale pink to white, visible during their defensive open-mouthed pose (origin of the name “cottonmouth”). |
| Body Shape | *Stout, muscular snakes. |
| Size | *These snakes grow up to 3 feet (0.91 m) in length. |
| Behaviors | *Cottonmouths arc their heads upward and display an open-mouthed pose when agitated. This exposes the white interior of their mouth. This is a warning to back off or suffer the consequences. *Interestingly, they can hold their breath underwater for up to an hour while hunting for prey. |
| Distinctive Features | *Pupils are cat-like and elliptical, appearing as narrow slits during the day. At night, pupils appear round. |
| Conservation Status | * Common within their range in Missouri. |
Where Do Northern Cottonmouths Live in Missouri?
The southern Ozarks and the wetlands of Southeast Missouri are home to these snakes. They spend most of their time near swamps, marshes, rivers, and lakes.
What Do Northern Cottonmouths Eat?
These snakes prey on fish, freshwater crustaceans, amphibians, small rodents, and other reptiles. Cottonmouths sometimes congregate around drying wetland pools to feed on any trapped fish.
How Dangerous Are Northern Cottonmouths?
Northern Cottonmouth venom is cytotoxic. This means it destroys body tissue. Northern Cottonmouth bites sometimes lead to the amputation of limbs. On rare occasions, Northern Cottonmouth envenomation leads to death.
Rattlesnakes in Missouri
Missouri is home to the following rattlesnake species:
- Timber Rattlesnake (Crotalus horridus)
- Western Pygmy Rattlesnake (Sistrurus miliarius streckeri)
- Eastern Massasauga Rattlesnake (Sistrurus catenatus)
- Western Massasauga Rattlesnakes (Sistrurus tergeminus)
What Missouri rattlesnakes have in common with most other rattlesnake species is their rattle.
- Most rattlesnakes have a rattle at the end of their tail, 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 rattling or buzzing sound.
- Not all rattlesnakes rattle before they strike. Sometimes, they lose their rattles due to injury, and sometimes, they choose not to rattle.
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.
| 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 | It is one of the most common venomous snakes in Missouri. |
Where Do Timber Rattlesnakes Live in Missouri?
The Timber Rattlesnake is the most common venomous snake in Missouri. They are found throughout the state. Timber Rattlers live in various habitats. These include wooded areas, swamps, farm fields, and river floodplains.
What Do Timber Rattlesnakes Eat?
Timber rattlers prey on small mammals such as mice, rats, squirrels, and chipmunks. They also eat small birds, other reptiles, and amphibians.
How Dangerous Are Timber Rattlesnakes?
Timber Rattlesnakes are among the most dangerous in the United States. This is due to their long fangs and high venom yield. 1% to 10% of untreated Timber Rattlesnake bites result in a fatality.
Fortunately, 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.
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Western Pygmy Rattlesnake (Sistrurus miliarius streckeri)
Other common names for this snake are Ground Rattlesnake and Pygmy Rattlesnake.
What Do Western Pygmy Rattlesnake Look Like?
| Size | *Small, slender-tailed snake with a tiny rattle. *Length: 16 to 25 inches (41 to 64 cm). *Average length: 21.1 inches (54 cm). |
| Coloration and Markings | *Body: Light grayish brown with dark-colored blotches that form crossbars along the top and sides. *Stripe: Rust-colored vertical stripe on the back (may be absent in some individuals). *Belly: Cream-colored, often mottled. *Face: Distinct dark stripe from the corner of the mouth to the eye. |
| Rattle and Sound | *A tiny rattle produces a faint, grasshopper-like buzz. *Sound can only be heard from a few feet away. |
| Conservation Status | *Common within their range in Missouri. |
Where Do Western Pygmy Rattlesnakes Live in Missouri?
Western Pygmy Rattlesnakes live in southwest and south-central Missouri. They prefer sandhills, mixed forests, and floodplains near aquatic environments. They are rarely found in extremely dry habitats.
How Dangerous Are Western Pygmy Rattlesnakes?
Western Pygmy rattlesnakes have cytotoxic venom. By definition, cytotoxic venom destroys the body’s cells. This venom disrupts blood flow and prevents clotting with its digestive enzymes. Luckily, these snakes produce a small venom yield. A bite from a pygmy rattlesnake is unlikely to be fatal. However, any bite victim should still receive prompt medical attention.
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 sizeable solid blotch. |
| Head | *A dark stripe on each side of their face and across their eye. |
| Conservation Status | *The Missouri Department of Conservation has listed the Eastern Massasauga Rattlesnake as endangered. It may be extirpated. |
Where Do Eastern Massasauga Rattlesnakes Live in Missouri?
Eastern Massasaugas live in eastern Missouri. They live in forested swamplands, marshy grasslands, lake edges, wet prairies, and woodlands.
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.
Western Massasauga Rattlesnakes (Sistrurus tergeminus)
What Do Western Massasauga Rattlesnakes Look Like?
| Size | *Adults range from 14 to 36 inches (36 cm to 91cm) long. |
| Coloration | *Their base color is light gray. *Younger snakes are paler than adults. |
| 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. |
| Face | They have a dark stripe on each side of their face and across their eye. |
| Conservation Status | The Missouri Department of Conservation has listed the Western Massasauga Rattlesnake as endangered. |
Where Do Western Massasaugas Live in Missouri?
The Western Massasauga is listed as an endangered species in Missouri. Snakes are found in the northwestern corner of the state. They are also found in northcentral Missouri. Western massasaugas live in wet prairies with grasses and sedges. They take refuge in crayfish burrows to escape predators and harsh weather.
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.
Missouri’s Venomous Snakes in Winter: Insights into Brumation
During winter, Missouri’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 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 for den sites because these areas receive more sunlight, providing additional warmth during winter.
This natural adaptation allows Missouri’s venomous snakes to survive the winter and re-emerge when temperatures rise.
Wildlife Code of Missouri
All native snakes are protected in the state of Missouri. According to the Wildlife Code of Missouri, lizards, snakes, and turtles are nongame. So, there is no designated hunting season for these animals, and it is unlawful to harm or kill them.
However, there is a practical exception to this rule. When a venomous snake is a direct threat to people, it is permissible to take action.
Avoiding Snake Bite
In Missouri, copperheads are responsible for the majority of venomous snake bites. These snakes rely on their excellent camouflage to stay hidden. They often remain perfectly still to avoid detection. If you’re walking in the woods and unknowingly get too close, a copperhead might not move, hoping you’ll pass by. Many bites happen when someone accidentally steps on the snake. 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:
- Severe pain
- Discoloration in the area of the bite.
- Swelling in the location 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 help.
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 doctor.
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 as soon as 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
In conclusion, Missouri has six species of venomous snakes. These snakes, including the Eastern Copperhead, Northern Cottonmouth, and four rattlesnake species, play vital roles in controlling prey populations and maintaining ecological balance. However, they also pose potential dangers to humans due to their venomous bites. Understanding their behaviors, habitats, and appearances allows people to coexist more safely with these reptiles. Awareness, proper precautions, and respect for their role in the ecosystem are key to minimizing risks and appreciating the diversity of Missouri wildlife.
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