"Does Iowa have any poisonous snakes?"

It's a question that comes up when visitors see our animal ambassador snakes, and the answer is "No."

That might not be what you expected.

You see, snakes in North American are not poisonous, they are venomous --- which means they inject a toxin rather than secreting a poison from the skin. It's rare for a snake to be both poisonous and venomous. Snakes in the genus Rhabdophis, found in Asia, are both venomous and poisonous.

Iowa does have four species of venomous snakes: Copperhead (Agkistrodon contortrix), prairie rattlesnake (Crotalus viridis), eastern massasauga (Sistrurus catenatus) and timber rattlesnake (Crotalus horridus).

Photos of Iowa's venomous snakes

Although there are no universal identifying features of venomous snakes, among Iowa's venomous snakes, there are some identifying characteristics to watch out for.

Graphic about venomous snake characteristics

A rattle on the end of the tail

Three of Iowa's four native, venomous snakes have a rattle on the end of the tail. This is a tool the snake uses as a warning to those getting too close. However, a rattlesnake may not "hear" --- through vibrations --- humans approaching, so it may not rattle. That's why people should always be aware in an area with rattlesnakes.

A rattle is composed of hollow, interlocked segments made of keratin, and the snake uses muscles to vibrate the segments against each other. This creates the tell-tale sound.

Heat-sensing pits

Sight varies greatly among snakes, with some only being able to discern fuzzy shapes and a few colors to others with clear, but not sharp, vision. The ones with clear vision can track movement but cannot tell a mouse from a vole.

During hot summer months, several Iowa snakes become nocturnal. Being active and hunting at night is far less energy expensive for the energy conservative snake. So, if so many are active at night, how do they hunt so effectively? Non-venomous snakes that switch to nocturnal activity rely on external light and their keen sense of smell to compensate for their not-so-sharp eyesight.

(Read about how snakes smell.)

However, venomous snakes have evolved to "see" very well at night. The venomous snake species of Iowa have special heat-sensing pits that sense infrared radiation --- the body heat of other animals. These pits are located on each side of the snake's head, between the eye and the mouth.

Elliptical pupils

All of the venomous snakes in Iowa have elliptical pupils, and many people think that applies to allow venomous snakes in the world. However, this isn't a hard-and-fast rule. Some highly aggressive snakes in the world have round pupils.

Fangs

Venomous snakes have fangs that are sharp, enlarged teeth along the upper jaw. They can be at the front or the back of the snake's mouth, and they are connected to venom glands. Even non-venomous snakes have teeth.

(Watch how the nature center snake's eat on our Videos page.)

Many of these signs of venomous Iowa snakes are only noticeable up close, so it is always best to be aware of where you are walking and what wildlife might be in that area. Whether a snake is venomous or not, if you're unsure, just leave it alone. A great general rule for any wildlife is, enjoy the view, but let wild be wild.

(Watch our community relations coordinator attempt to hold a snake for the first time.)

Garter snakes of Iowa

Iowa has 28 different species of snakes, including four venomous species. (Read about the venomous snakes of Iowa here.) Most people are familiar with the garter snake, a common type of non-venomous snake, which are harmless to humans. Let’s take a look at the two kinds of garter snakes that are native to Iowa: Plains…

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How a snake breathes while it eats

Just because they work for a conservation board doesn’t mean that naturalists know everything. Just last week, naturalist Ashley Hansen was feeding Rosie the corn snake when she noticed a hole open up in the snake’s mouth while it was eating a mouse — the Dickinson County Nature Center snakes are fed mice that are…

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Make a bendable snake with pipe cleaner and beads

In honor of my big day today, holding a snake for the first time (you can see the video here), we made a fun snake craft. Whether you love snakes or hate them, this craft is cute and simple. You’ll need: Pipe cleaners Beads Googly eyes Liquid glue Start  by selecting what kind of head…

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How and why snakes shed their skin

If you find a snakeskin in the wild, it’s usually inside out! When it sheds, it slithers out of its old skin, like pulling a sock off your foot, so it ends up inside out! Watch the video for more information on how and why snakes shed their skin. Check out more of our animal…

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Paper chain snake instructions

Crafts are so much more fun when the end result is actually something to play with rather than just hang on the refrigerator. This paper chain snake that can slither and wiggle is an easy and interactive craft for the snake lovers out there. And if you don’t have snake lovers, call it a caterpillar…

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Ssssomething totally awesssome: Create a sssnake wrist cuff

Since this week’s blog post was about how snakes slither, I thought it only appropriate that this week’s craft also be snake related. I will pretty much guarantee that after you make this fun wrist cuff that your child will not take it off for the entire day. Or at least the next five minutes,…

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Creepy but cool: How snakes can move without legs

Besides their forked tongues, probably the main thing that creeps people out about snakes is their ability to move without legs or feet. (The reason a snake sticks out its tongue, and why it’s forked.) I have to say, before I started working at the Dickinson County Nature Center, back when I was still petrified…

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Feeding the nature center snakes

The naturalists make sure to wash their hands after handling the mice before picking up the snakes. They don’t want the snakes to associate people with food or being let out of their enclosures with food either so that they don’t expect to be fed every time the enclosure door is opened.

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The reason a snake sticks out its tongue

Why do snakes stick out their tongues at you? Have you ever seen this? You’ve been looking at one of the snake animal ambassadors at the nature center, and one of them sticks out her black tongue and flicks it around. She is smelling you! The snake’s tongue has a fork on the end of…

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23 Comments

  1. Suez on July 13, 2020 at 8:44 pm

    Lived in Iowa for 69 years, never knew we had anything more than timber rattlers up north around Sumner Ia. Never heard of Copperheads in Ia.
    Wow! Never to old to learn.



  2. Larry T. Wilson on May 22, 2020 at 7:20 pm

    Thanks for the very informative article. Hopefully more folks will become appreciative of their benefits. Good job.



  3. […] 4.) Of the 28 species of snakes in Iowa, five are venomous: Prairie Rattlesnake, Timber Rattlesnake, Eastern Massasauga, Western Massasauga, and Copperheads. Learn more about identifying these four species here. […]



  4. Carlos on April 16, 2020 at 1:01 pm

    Are there venomous snakes in Jackson County Maquoketa area?



    • kiley on April 17, 2020 at 8:36 am

      I would check with your local conservation board!



    • Carl on May 1, 2020 at 8:29 pm

      Yes. Timber rattlers especially along the Mississippi and Maquoketa Rivers like at Pictured Rocks or Indian Bluffs. They are not common



      • Jason on July 17, 2020 at 7:58 pm

        Although you may not think they are that common. I have a differing opinion. In Madison County we see 5-10 timber rattlesnakes a year. Our dogs have been bit a few times over the years.



  5. Terri on January 29, 2020 at 11:52 pm

    I see from the comments there are a lotof people concerned about snakes.
    Clearly, I am not alone.
    Right now I live in western Washington where there are no venomous snakes. Don’t think we can afford to retire here. I’m scared to go anywhere with venomous snakes. 😉



    • Don on April 8, 2020 at 5:08 pm

      Have lived in Iowa since 1968. Never seen anything more than garter snakes and 1 bull snake. Venomous snakes live in very specific habitat.



      • Bear on May 3, 2020 at 2:00 pm

        I had a log home to the north east of Anamosa. Found a small timber rattler in the yard. So they are in Jones Co.



    • Andrew on April 22, 2020 at 12:22 pm

      Why? Just walk with caution and leave them be. They are more afraid of you than you are of it.



  6. Michelle on September 22, 2019 at 4:43 pm

    What about water moccasins and cotton mouths



    • kiley on September 23, 2019 at 10:46 am

      Water moccasins, otherwise known as cottonmouths, are not typically found in Iowa. They are not considered an “Iowa snake.”



  7. Maryann Ressler on July 27, 2019 at 9:28 am

    I was told that there is no venomous
    s snakes in Iowa. Apparently that’s not true. Are there any venomous
    snakes in Cerro gordo county?



    • kiley on July 29, 2019 at 8:12 am

      These types of snakes are not very widespread in Iowa. The timber rattlesnake has been found in eastern and southern Iowa. The massasauga was found in a couple of state marshes. The prairie rattlesnake has been seen in the northern portions of the Loess Hills, rarely, and the copperhead can be seen in a small area in southeastern Iowa.



  8. Lisa Guadagnoli on May 9, 2019 at 12:49 am

    are they going to pursue a individual and attack?



    • kiley on May 9, 2019 at 8:03 am

      Definitely not — if you leave them alone, they will leave you alone. Wild animals just want you to leave them be.



  9. Thelma Morris on April 20, 2019 at 4:21 pm

    Can garter snakes become aggressive? I had one strike out at me today. The snake had yellow stripes down the length of it’s body. I think the body was green but my husband thought it was brownish.
    Thanks



    • kiley on April 22, 2019 at 8:07 am

      Most garter snakes are docile, but some may try to bite or lash out in self-defense. It may have felt threatened.



  10. Mr. Curious on September 26, 2018 at 6:37 pm

    Where in Iowa do these snakesive, are they in Dickinson County?



    • kiley on September 27, 2018 at 8:59 am

      These types of snakes are not very widespread in Iowa. The timber rattlesnake has been found in eastern and southern Iowa. The massasauga was found in a couple of state marshes. The prairie rattlesnake has been seen in the northern portions of the Loess Hills, rarely, and the copperhead can be seen in a small area in southeastern Iowa.



  11. Tim on September 26, 2018 at 11:15 am

    Great information! Are these snakes in every county of Iowa?



    • kiley on September 27, 2018 at 8:59 am

      These types of snakes are not very widespread in Iowa. The timber rattlesnake has been found in eastern and southern Iowa. The massasauga was found in a couple of state marshes. The prairie rattlesnake has been seen in the northern portions of the Loess Hills, rarely, and the copperhead can be seen in a small area in southeastern Iowa.