Disjunct Populations of the Cottonmouth Water Moccasin (Agkistrodus piscivorus)

When I first started reading about disjunct populations of the cottonmouth, I thought they might be interesting examples of populations isolated due to climate-influenced habitat change, but I later learned that most of them have become isolated because man has altered the surrounding environment, rendering it unsuitable for the snakes to survive.  Horizon-to-horizon cotton and corn fields eliminated habitat for intervening populations over 100 years ago in some areas and even more recently in others.

Older adult cottonmouth.  The adults turn so black, it’s difficult to see their markings.

Young cottonmouth killing a northern watersnake.  Note the brown striping which is so colorful compared to the older individual above.

Cottonmouths are a semi-aquatic snake that forages in swamps and lowlands, but in regions where frosts occur during winter, they need adjacent forested uplands where they can den in rocks, fallen logs, and rotted tree trunks.  A disjunct population of cottonmouths exists at Fosters Bend (a notable locality of which I discuss in more detail below).  Fosters Bend is an oxbow lake bordering an intact forest in northwest Georgia.  Dr. Charles Wharton believes the population of cottonmouths became isolated here because the surrounding land was cleared for agriculture.  Other disjunct populations on the periphery of cottonmouth range were Livingston County, Missouri where they were extirpated in 1987, and Montgomery County, Kansas where they were extirpated in 1993.  A genetically isolated population still occurs on Seahorse Key in Florida, but this population is isolated by sea water.

The Agkistrodus genus is part of the pit viper family of snakes.  DNA analysis suggests copperheads (Agkistrodus contortrix) evolved first, probably before the Pleistocene began. Cottonmouths evolved from copperheads that began foraging in swamps rather than dry upland forests. The speciation was likely a result of a differentiation of habitat preference.  The cantil (Agkistrodus bislineatus) then evolved from cottonmouths that expanded their range into Mexico.  Pleistocene cottonmouth fossils (just 4 vertebrae) were excavated from the Isle of Hope site in Chatham County, Georgia. Fossil skeletel remains of copperheads were found in Kingston Saltpeter Cave, Bartow County, Georgia.  Both species have a long history in Georgia, probably dating back at least 2 million years.  Reptile evolution is particularly slow.

Cottonmouth range map color-coded to depict subspecies.  The blue region is populated by the eastern cottonmouth, A. p. piscivorus.  The Florida cottonmouth A.p. conanti inhabits the red region.  The green region is inhabited by the western cottonmouth, A.p. leucostoma.  The gray area has intermediates between all 3 subspecies.

A copperhead.  Copperheads inhabit dry upland forests, while cottonmouths live in the lowlands.  Cottonmouths probably evolved from copperheads that began foraging in lowland swamps.

Pit vipers sense their prey with the pits located near their nostrils.  The pits detect changes in temperature–both warm-blooded and cold blooded prey have body temperatures that differ from the surrounding environment.  Cottonmouth poison is of the tissue destroying kind.  After they strike cottonmouths hang on to small prey such as mice and frogs which might escape before croaking (forgive the pun), but will release larger animals to avoid injury while the animal struggles.

Cottonmouths feed on small mammals, birds, birds’ eggs, baby alligators, fish, other snakes including other cottonmouths, snails, insects, and carrion.  Algae is often accidentally injested.  They are known for congregating around shrinking water holes where they can easily catch concentrated and trapped fish.  On Seahorse Key cottonmouths specialize in feeding upon dead fish dropped or vomited by wading birds.

Cottonmouths sometimes eat king snakes, and vice-versa–it depends on the size of the snake.  Smaller cottonmouths can occasionally repel larger king snakes with body blows, using their head to punch the bigger snake and knock it away repeatedly.  They also exude a musky odor when threatened.  Other natural enemies include alligators, great blue herons, indigo snakes, and largemouth bass.  Cottonmouths return the favor and prey on fledgling herons and trapped bass.  There’s a cycle of unwitting revenge in the swamp theater, depending on the age and size of the players.  Mites can infest and kill cottonmouths, and almost all are plagued with tapeworms from living on a diet of raw fish. 

During winter animosity between cottonmouths and other snakes disappear, and they will nest communally.

I’ve only seen a wild cottonmouth on one occasion.  The snake was a large fat adult, resting on a bank next to Woodbridge Lake in Evans, Georgia.  Young cottonmouths have brown stripes but older ones turn so black that the markings become less visible.  The individual I saw was completely black.  Studies show cottonmouths are not aggressive snakes.  About the only way a person can get bitten is if they step on or handle the snake.  Doctors treat the tissue-destroying venom with Crofab antivenom.  Marlin Perkins, the late zookeeper of Wild Kingdom fame, wrote that the only good thing about getting bitten by a poisonous snake was enjoying a complete recovery, once the antivenom treatment worked.

I don’t understand why people keep reptiles as pets.  Reptiles form no bonds with people.  The part of the brain involved with emotion does not exist in reptiles or any vertebrate less advanced than a bird.

Fosters Bend

Here’s a spot that may be worth exploring, if it hasn’t been developed since Dr. Wharton described it 30 years ago.

Photo of Fosters Bend in Floyd County near the border between Alabama and Georgia.  It’s from The Natural Environments of Georgia by Dr. Charles Wharton.

Fosters Bend is a Coosa River oxbow lake located in Floyd County in northwestern Georgia.  He found a floodplain hardwood forest with species more characteristic of the coastal plain than of the surrounding mountains of north Georgia.  One end of the lake has a forest of tupelo.  A forest of willow oak, water oak, overcup oak, hickory, and persimmon grows in a dried out oxbow.  The natural levee between the oxbow and the Coosa River has a diverse forest of sycamore, silver maple, willow, mulberry, basswood, and several species of oaks.  Archaic and woodland Indians sites occur here as well.

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21 Responses to “Disjunct Populations of the Cottonmouth Water Moccasin (Agkistrodus piscivorus)”

  1. jamesrobertsmith Says:

    I see watersnakes quite often. They do get mistaken for moccasins. I have rarely seen a water moccasin. Not sure why, but I’m glad I haven’t. I don’t hate them, of course, but I’d rather not run into one when hiking or swimming or kayaking.

    I think copperheads are as common now as they ever way. Maybe even more so. I see them everywhere I hike, except for the highest parts of the Appalachians…above 4500 feet or so. I have encountered one rattlesnake at high elevations–right at 4500 feet on Hughes Ridge in the Great Smoky Mountains National Park. He was a monster, too, but very torpid because it was so cool. My wife and I also encountered a rattlesnake at 4200 feet on Unaka Mountain on the Tennessee/NC border (north of the Smokies). He/she buzzed at us and hid. The buzz was hard to hear because some of the rattles had broken off and it didn’t have much in the way of a rattle to warn us–maybe three buttons. This particular rattlesnake was the blackest one I’ve ever seen–probably because it lived so high and needed to absorb as much heat as possible.

  2. jamesrobertsmith Says:

    Ever “were”, rather.

  3. markgelbart Says:

    I’ve read that water snakes are supposed to resemble cottonmouths, but I don’t think they look similar at all…at least not to me–I’ve been studying field guides since I was 7.

    The overall population of copperheads is much reduced. Urban areas and sprawl make for poor copperhead habitat. Their numbers are probably pretty stable in rural areas though.

    Don’t worry about editing comments. Life is too short. I knew what you meant.

  4. jamesrobertsmith Says:

    If you ever get a chance to walk around Fernbank Forest at the old Fernbank Science Center in Atlanta (not the newer Fernbank Museum of Natural History) watch for copperheads. The forest is a gorgeous example of a preserved Piedmont forest in a relatively undisturbed state with many impressive trees. But the copperhead population is prodigious. You genuinely have to be careful in there.

    The most copperheads I have ever seen in a single location was at Trout Pond, the only natural lake in West Virginia. It formed from a collapsed cave and has a lot of fish. It also has more copperheads than any place I’ve seen. Everywhere we looked they were lying in the sun or under shrubs or coiled up by the lake. Every few feet you could see a copperhead. One guy was fishing while we were there and he wasn’t worried. He told us just to watch our step.

    I hiked around the lake (it’s a small one), but my wife went back to the truck.

  5. markgelbart Says:

    Fernbank Forest is on my list. I just hate to have to go through Atlanta to get there.

  6. Mark L. Says:

    “I don’t understand why people keep reptiles as pets. Reptiles form no bonds with people. The part of the brain involved with emotion does not exist in reptiles or any vertebrate less advanced than a bird.”
    Um. Because they are cool? Honestly, they do form bonds, but don’t get caught up in the ‘mamby-pamby-land’ of human emotions and anthropomorphism. They show you how life is-without garnishings, beauty salons, and houses. ‘Cold hard killers’ or incredibly effecient members of an ecosystem (pick one). They are what they are, without a valence attached to them.

  7. markgelbart Says:

    Do you have reptilian pets? If so, what kind?

  8. Mark L Says:

    Have? now, 3 kinds of turtles, and sometimes 2 rat snakes…they stay under the house for the winter and fix my chipmunk problem in spring and summer. I’ve had bearded dragons and iguanas also and a bunch of pet birds. Several frog species and crabs also. For a while, I would actually call the humane society to see what animals they need a home for that week….always an adventure.

  9. jamesrobertsmith Says:

    My son has a couple of snakes. And two young box “turtles”. The box turtles are actually pretty friendly and seem to show what I would describe as personality if I were to witness the same behavior in a mammal pet. I have a friend who has owned a large iguana for many years now, and he seems to think the iguana feels affection toward him. Who am I to say otherwise?

    There are some YouTube videos of large tortoises also displaying some pretty canny behavior that I would never have suspected from a reptile. There’s also a funny video there of a big tortoise showing the resident Great Dane dog that he is boss of the bedding where the dog is. It’s pretty funny stuff.

  10. Bill Thompson Says:

    I have never been a snake fan to the point that I want to handle them. I have never been bitten, although I have trompped around in the woods all my life. I believe it is wrong to kill any snake because of how they improve the quality of our lives. I am amazed at how tame some snakes appear to be. In the few instances where I have handled them (hog-nose, green snake, and garter snakes), only once did I have one try to bite and it grabbed my shirt-sleve, then never tried to bite after it got calmed down. I have never been very comfortable handling them, so as I have gotten older, I just don’t bother them.

    Having lived in Southern Indiana as a youth, I once saw a baby Copperhead that a friend of mine brought from his property that he said had a small infestation. This was in the area below Lake Monroe between Bedford and Bloomington. There was a story about a young boy who lived in the neighborhood and nearly died when he was repeatedly bitten by baby Copperheads when he somehow got into the nest and mistakenly thought they were fishing worms.

    I grew up in the SE corner of Indiana within view of the Ohio River. I never saw a Copperhead. They were there because there were accounts over the years (rarely) of people being bitten and the snakes being ID’d by wildlife experts.

    Some people in that area swore there were Water Moccasins there, It is possible, but I think they were Northern Watersnakes (not a particularly friendly snake). In this area I saw a lot of large Blacksnakes. A friend of mine swears there is a 14” Blacksnake that lives in the woods near his home. It has been seen multiple times and even run over by a car. My friend’s brother and him were in the car at the time. He said, ”when we hit it, it was like hitting a speedbump and it just sllithered away.” He has seen it since.

    I recently moved to the Montgomery, Alabama area and was told there was a little bit of everything here and some areas are thick with snakes. We have state forest behind the house that I would like to explore, but am a bit concerned because of what I had heard and my not knowing the territory. The area is within a mile of the Coosa River and has several small creeks and quite a few ravines. The forested area is fairly thick. Looks like snake country to me.

    The next door neighbor said that he fished a Water Moccasin out of his pool a couple years ago. I thought I’d just get a pair of boots and carry a large stick with me, so as to let them know I was in the vicinity.

    Once I had a blacksnake whip me with his tail once when I was briskly walking to one of my favorite fishing spots in Southern Indiana. I laughed. My girlfriend screamed! I just don’t see or hear as well as I did when I was younger, nor can I sniff out a snake as one of my friends claims to be able to do.

    My lifelong work was as an appraiser. I lived in Colorado for 26 years. I frequently had to do work in rocky foothill areas of the Rocky Mountains west and northwest of Denver. I never positively ID’d a ‘Rattler, but I saw a couple dead ones and in some instances, was very concerned about running into one. I once had a homeowner that said his property was ”thick” with rattlesnakes. This was in the foothills approximately 25 northwest of Fort Collins, CO.

    My wife and I fished in some of the Colorado streams and never encountered any rattlesnakes, but typically when I encounter a snake, its when I am not thinking about encountering a snake at all!

    Once when I was a kid, I spent a summer in the woods near Springfield, Mo in an area with a small lake. I believe I may have seen a Water Moccasin there, but not absolutely sure.

    Nor sure about these either, but I believe I saw a Pigmy Rattler near Ruskin, Florida and may have seen a Moccasin on a gravel road just about a 100 yards from the Chattahooche River, near Roswell, Georgia.

  11. Roberta Allen Says:

    My husband and I were sitting in low river chairs on the bank of Current River today in the Mo Ozarks. Having a great time watching the floaters when all of a sudden a large, thick black snake come under our chairs…. We jumped up and the snake went into the deep water and disappreared. Needless to say, we were terrified as a local man was bitten by a copperhead this week on the river and died. (He had underlying heart issues and died in transit. They were camping in a romote location and he was bitten on the thumb while trying to move the snake out of a tent. Bit him on the thumb, coded on the way to the hospital.

    My question is: Do they have a smell before you see them? I noticed some smell 15 to 20 minutes before this happened. We jumped out of the water immediately. Could he turned on us?

    • markgelbart Says:

      Reportedly, cottonmouths and copperheads both have musk glands near their cloaca. They emit the smell when they’re alarmed.

      • Bill Thompson Says:

        I never see a snake when I am looking for one or on the defensive. Its always when I am not thinking about seeing one. Hard to say what that was. From what I have seen, mostly heard, is that if it looks more like a blacksnake, but if it is a Cottonmouth, then it is probably and older one.

        That area that had the recent Colorado wildfire near Ft. Collins is an area that is notorius for being thick with ‘rattlers. The foothill areas up to about 7000 ft are one of a rattlesnakes preferred areas.

        I have never been expert enough to notice of any snake emits an odor, but if the experts say so, I am positive they are right about that. I have heard that people smell a black snake when one is nearby.

  12. Julie Jacques Says:

    Saw a western cottonmouth in far northeastern Tennessee (White Pine). Your map does not show this snake anywhere in Tennessee. Should I report this to the local wildlife officer? Please contact me at docjacques@charter.net

  13. Sweetfury Says:

    Snakes are one of natures inhabitants and some seem to be on the decline while others are abundant. I grew up during my early teen years in Trimble County Kentucky. Located right on the Ohio river across from Madison IN. Copperheads are by far the most abundant snake. We had an old cistern on our property that housed multitudes of copperheads. As they matured it seemed their favorite place to make home was in the downstairs of the old school building in which our family lived. Over the years repeated flooding had made the downstairs unlivable. The brick structure however had survived and only the upstairs was used as a residence for the family. Being one block away from the river I spent a lot of time there fishing. I also learned that copperheads were not the only snakes in the area. Water snakes are plentiful and those guys had an attitude when they got to close to me or vise versa. I would say they were more aggressive in some ways than the copperheads. Rumor had it that the dreaded cotton mouth had made it to the area and despite the warnings which I heeded, I never saw one that I could say without doubt was a cotton mouth. I was one who went by head shape and the presence of pits when possible but I wasn’t going over there to introduce myself. Most of the time the markings told the tale. For a girl I did pretty good, but my preteen years in Blocher Indiana were spent picking up any snake that caught my fancy and I had no idea what they were. A stern lecture and an education in snake identification were quickly forthcoming. They said it was for my own good but I figure they just didn’t like me bringing my latest find up to them to show off. For the last few years I haven’t seen many snakes. What I have seen are mostly the brown water snakes when fishing. In the last 10 years I have seen one black snake (black indigo in Florida), one rattlesnake at the first rest stop on the north bound side after crossing into Georgia from Florida, and several garter snakes. This site makes for some good reading and hopefully more people will contribute their opinions and stories. Thanks everyone!

  14. Duffy Bishop Says:

    We live in a new development two miles outside of St. Augustine,Florida & when we moved in, found two water moccasins in the pond out back of our house. We Watched them everyday from five feet away for a few months. Winter came & they left. Now with Spring arrived we’ve seen them again in the water & reeds. They have not been aggressive & we keep our distance & walk cautiously through our wooded yard. Our living room & screened porch are maybe ten feet including sloped bank to the water. Watching the wildlife is amazing. I found this site because today I watched a Great Blue Heron strike & kill an adolescent (from the more colorful markings) three foot long Water Moccasin. The head was large viper shape & clamped in the birds beak until dead. The Heron took the snake into the bank bushes & began eating it. I was shocked because I didn’t think anything could eat the poisonous snake.

  15. Ronnie Says:

    I think flooding in the last few years have moved cotton mouths where they haven’t been in a lot of years streams and rivers are the interstate for these snakes I haven’t proved it yet but southeast ky should have cotton mouth snakes

  16. My 500th Post | GeorgiaBeforePeople Says:

    […] https://markgelbart.wordpress.com/2012/03/04/disjunct-populations-of-the-cottonmouth-water-moccasin-… […]

  17. J.R.McElroy Says:

    Just killed an about 7′ cottonmouth today here in NE Louisiana in my yard it was an old one almost couldn’t see the bands but the belly gave it away its head was a good 2 plus inches long and a good inch plus wide , about 3 yrs ago we had multiple cooper heads slither across the yard while i was mowing, been here 10+ yrs and have seen 7 different types of snakes.

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