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  • Carrie Gardner

Venomous Snakes in the United States

Updated: Sep 19


Since we are now officially getting into venomous territory, it’s time for a friendly discussion on an all too common problem when it comes to these creatures. Though they are commonly referred to as “poisonous”, they are really not.

Poisonous animals are passive in how they introduce toxins. Amphibians, for example, will cover their bodies with poisonous secretions. If an animal tries to eat them, they will get the poison in their mouths and, hopefully, spit it out. If a human picks it up, the skin may become irritated, but it where it will do the most damage is when the eyes, nose, or mouth are touched, since that introduces it to the system.

Venomous animals bite or sting to envenomate. They don’t need to wait until they are touched (and hope the toxin is introduced to the mucous membranes around the face,) they can actively defend themselves. If you touch a rattlesnake, you won’t get poisoned, you will be envenomated. There are a couple of snakes that are both, but they aren't found in the United States.

I realize that it's not a matter of life and death with whether or not a snake is poisonous or venomous. But it's a major pet peeve for people who are into snakes and has caused many "discussions" on Facebook groups.

There are two types of venomous snakes in the United States - pit vipers and coral snakes. We can further break down the pit vipers into copperheads, water moccasins (or cottonmouths), common rattlesnakes, and ground rattlesnakes.

Pit vipers have a large pit in their faces roughly between the nostrils and eyes. These pits are highly sensitive heat sensing pits that give them an infrared image much like an infrared camera. Since they hunt primarily at night, They are ambush predators that hang out next to rodent trails. The heat signature off their prey allows the snake enough time to strike. The envenomated animal is allowed to continue on. In a few minutes, the snake goes after it, using the scent of its venom to follow. Dinner has already passed on and the snake’s venom is already working on digesting.

Studies have been done that demonstrates the snake can accurately hunt even with their eyes covered without any hesitation. When that was reversed with the heat pits covered, it took them much longer. All snakes are blessed with a spectacular sense of smell. They catch air molecules with their tongue (forked to receive molecules on both sides,) which is why it’s always flicking in and out. Eventually, the snake with the pits covered were able to catch the mouse with smell. Studies have shown that they can tell a difference in temperature as small as 3/1000s of a degree.

Most pythons and boas also have heat pits, except theirs are located have on their upper lips -(called labial pits) and they are nowhere near as sensitive.


Pit vipers are heavy-bodied snakes with a reluctance to share their venom with anyone but their dinners. The largest rattlesnake in the country is the Eastern diamondback rattlesnake.

A lot of websites rate venomous snakes on their aggressiveness. I personally have a problem with that. If you were to do a search on snakes that chase people on YouTube, you would see a bunch of videos showing "extremely aggressive" water moccasins. In fact, it's a huge myth that they chase people. Herpetologists and experts all agree, however, that they don't give chase. People also get confused between "aggressive" behavior and "defensive" behavior. Aggressive is when an animal comes after you for no reason. Defensive is when they feel they're being threatened and are protecting themselves. Snakes are like other animals and they have their own personalities with their own limitations and reactions to stress.

Besides the pit vipers, we have three species of coral snakes, found mostly in the southern states.

According to Venom Byte - Venomous Snakes by State, Arizona has the most species of venomous snakes, at 19. Click on the link to find out how many your state has! If you’re in Florida...you can just read the next page - where I get descriptive.

Because all but the coral snakes are pit vipers in the United States, the same antivenin is used to treat all viper bites - CroFab. Released in 2000, it is derived from sheep using the venom of the eastern diamondback, western diamondback, Mojave rattlesnake, copperhead, and cottonmouth snakes. In 95% of those treated, there was a clinical response in less than an hour. While it costs about $100.00 - $400.00 a vial in Mexico (they recognize that snakebites are a public health concern,) in the U.S., the suppliers charge $2,300 - $2,800 to hospitals. Hospitals then hike it up to anywhere from $14,000 - $20,000 per vial. They say that they charge that much as a way to open up negotiation with insurance companies. If a patient doesn’t have insurance or has a high deductible, they are pretty much screwed. So, if you see a snake, walk away and go spend the $100,000.00 that you would’ve had to pay a hospital for treatment on something fun! *Late 2019, a new antivenin was released that is less expensive and stays in the body longer. Anavip was approved for the use on rattlesnakes only, though. A vial costs $1,200 a piece but I'm not sure how many are required.

There is currently problems with producing coral snake antivenin. Tampa General Hospital is in close contact with the FDA and Wyeth/Pfizer to remedy the situation, and my understanding is that they are once again manufacturing antivenin. Here is more information: Coral Snake Antivenin Information.

And finally...the list! I've included the scientific binomial or trinomial names. Every animal and plant are identified by a Latin name, my fellow Homo sapiens because common names can apply to more than one species. It comes in handy when you want an exact identification.

Pit Vipers

Copperheads

Broad-Banded Copperhead -Agkistrodon contortrix laticinctus

Northern Copperhead - Agkistrodon contortrix mokasen

Osage Copperhead - Agkistrodon contortrix phaeogaster

Southern Copperhead - Agkistrodon contortrix contortrix

Trans-Pecos Copperhead - Agkistrodon contortrix pictigaster

Cottonmouths

Eastern Cottonmouth - Agkistrodon piscivorus piscivorus

Florida Cottonmouth - Agkistrodon piscivorus conanti

Western Cottonmouth - Agkistrodon piscivorus leucostoma

Rattlesnakes

Animas Ridgenose Rattlesnake - Crotalus willardi obscurus

Arizona Black Rattlesnake - Crotalus oreganus cerberus

Arizona Ridgenose Rattlesnake - Crotalus willardi willardi

Banded Rock Rattlesnake - Crotalus lepidus klauberi

Colorado Desert Sidewinder - Crotalus cerastes laterorepens

Eastern Diamondback Rattlesnake - Crotalus adamanteus

Grand Canyon Rattlesnake - Crotalus oreganus abyssus

Great Basin Rattlesnake - Crotalus oreganus lutosus

Hopi Rattlesnake - Crotalus viridis nuntius

Midget Faded Rattlesnake - Crotalus oreganus concolor

Mojave Desert Sidewinder - Crotalus cerastes cerastes

Mojave Rattlesnake - Crotalus scutulatus

Mottled Rock Rattlesnake - Crotalus lepidus lepidus

Northern Black-tailed Rattlesnake - Crotalus molossus molossus

Northern Pacific Rattlesnake - Crotalus oreganus oreganus

Panamint Speckled Rattlesnake - Crotalus mitchellii stephensi

Prairie Rattlesnake - Crotalus viridis viridis

Red Diamond Rattlesnake - Crotalus ruber

Sonoran Desert Sidewinder - Crotalus cerastes cercobombus

Southern Pacific Rattlesnake - Crotalus oreganus helleri

Southwestern Speckled Rattlesnake - Crotalus mitchellii pyrrhus

Tiger Rattlesnake - Crotalus tigris

Timber Rattlesnake - Crotalus horridus

Canebrake Rattlesnake - Crotalus horridus atricaudatus

Western Diamondback Rattlesnake - Crotalus atrox

Western Twin Spotted Rattlesnake - Crotalus pricei pricei


Ground Rattlesnakes

Western Massasauga - Sistrurus catenatus tergeminus

Eastern Massasauga - Sistrurus catenatus catenatus

Desert Massasauga - Sistrurus catenatus edwardsii

Dusky Pygmy Rattlesnake - Sistrurus miliarius barbouri

Carolina Pygmy Rattlesnake - Sistrurus miliarius miliarius

Western Pygmy Rattlesnake - Sistrurus miliarius streckeri

Elapids

Coral Snakes

Arizona Coral Snake - Micruroides euryxanthus euryxanthus

Eastern Coral Snake - Micrurus fulvius (pictured below)

Texas Coral Snake - Micrurus tener


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