Plate 1. Abandoned Ozark barnyard, Taney County, Missouri.
by Joshua Heston
Night falls. The air is warm in the darkness. Overgrown meadows and abandoned farmyards come alive, first with insects, then vermin. Mice. Voles. Shrews. Rats. All hurrying to eat, to store, to prepare for the onrushing winter that — deep within their genetic memory — they know is coming.
In the darkness, something else moves as well.
Near-silent in the weeds, a hunter moves forward, tongue-flicking, testing the air. A copperhead slithers over rock and around branch. Soon, it will strike. And feed. The venomous snakes of Missouri are patient, fearsome predators.
Copperheads & Cottonmouths
by Ben Dalton, graduate student researcher, Missouri State University Biology
The Ozarks are home to several species of venomous snakes — including the copperhead, cottonmouth, pygmy rattlesnake, timber rattlesnake and further north in Missouri, the massasauga. These snakes are venomous, not poisonous.
Poison is a toxin found in the skin of an animal (usually a defense against being eaten). Venom can be used for defense but is most often used by predators to incapacitate prey. In short, poison is dangerous when eaten. Venom is dangerous when injected into the blood.
Although snakes try to avoid human contact, we tend to encounter these unique animals on certain occasions. You will find snakes where you can find their prey. Most venomous snakes feed on small mammals so areas like old barns and overgrown fields will attract copperheads and rattlesnakes. Reptiles are most active in mid-morning (after they have time to bask in the sun and heat up) and again in late-afternoon. On hot summer days, snakes take refuge underground or in the shade to avoid over-heating.
Copperheads and cottonmouths are the most common venomous snakes in the Ozarks though both species are found elsewhere. The copperhead thrives throughout the south and east while the cottonmouth is found across the South (and most people identify the Ozarks with the South). Consequently, these two species are iconic to the Ozark Mountain Plateau.
While copperheads and cottonmouths look very different, they are closely related, sharing the genus Agkistrodon — meaning “fish hook” in Latin, referring to the shape of their fangs.
Copperheads are named for their rusty coloration which helps them blend into the leaf litter of the forest floor. Copperheads are edge specialists. They make use of the transition from forest to clearing to move in and out, hunting or taking refuge from predators. These edges could be a roadside, field or simply the gap from a fallen tree. However, snakes will have a home range they patrol with regularity (and this range may take them through areas from deep forests to backyards).
How often these snakes eat depend on the size of the prey they consume. Anecdotally, some friends of mine feed their juvenile snakes one to two “pinky” mice each week. Extrapolating from that, an adult copperhead could need one to two adult mice per week (or if were able to catch something larger, less food). When snakes eat, they typically remain inactive for a period of time until they have digested their meal and are ready to begin foraging again. It takes a lot of energy to digest an animal several times the snakes’ girth. Additionally, the extra weight and bulk makes the snake vulnerable to predators.
Both species kill by envenomation (injecting venom into the blood stream). One misconception about venomous snakes is that every bite injects venom. In reality, less than half of venomous snake bites inject venom (though this varies by species). The bite of the copperhead is not as potent as the cottonmouth and is rarely lethal to anything larger than a house cat (though it can still be very painful).
Copperheads typically wait for their prey to become irresponsive before ingestion. Snakes are unique in their method of feeding. Their jaw and many additional bones in their skull are extremely flexible and stretches out of place to encompass prey many times larger than the mouth’s normal size.
Both copperheads and cottonmouths are solitary animals, coming together only to breed. The distance maintained between animals is usually driven by food availability, making it possible for several snakes to share a relatively small area if the bounty is good enough.
I know it sounds cliché but these snakes are more afraid of you than you are of them. From a behavioral standpoint, they do not want to tussle with a larger creature because they 1) could get eaten, 2) may have to flee and waste energy that could be spent hunting, 3) they may have to defend themselves and expend energy by using venom, and 4) they may have to fight and possibly be injured (directly impact their ability to catch food or attract mates).
There is no winning solution for a snake to attack a human and it is silly to think they might have some reason to do so.
Copperheads may migrate but I doubt the distance is meaningful to their “patrol area.” Migrations are driven by season, food availability and winter den area. While there are records of copperheads congregating around certain cedar trees in the Ozarks, I would investigate prey abundance and habitat structure before jumping to other conclusions.
Cottonmouths — named from their characteristic defensive gaping posture which displays the white inside of their mouths — are common throughout the southern United States, typically near still bodies of water such as marshes or lakes. Here in Missouri they are also found near cold, rocky streams. I would look for cottonmouths around any body of water in the Ozarks. Their primary food source is fish (the species name piscivorus means “fish-eater”).
Ozark streams provide particularly attractive habitat. However, you will see cottonmouths around large lakes. I wouldn’t expect a snake to swim out into a large body of water but rather stay close to the edge where it can better hunt and thermo-regulate. There was a study done on cottonmouth foraging behavior revealing that male cottonmouths actually foraged far distances from water (one to two miles) if rodents were easily available. Females and juvenile cottonmouths tended to stay closer to the water.
Of the two species, cottonmouths have more potent venom. Snakes control when they inject venom and I’m pretty sure they have control over how much they inject. In this way, a snake that catches a larger animal can apply a larger dose of venom (and inversely not waste venom on a smaller animal). Cottonmouth venom is not as toxic as that of the timber rattler but more so than that of the copperhead. There is antivenin available at most hospitals.
The effectiveness of sucking out the venom after a snakebite is a common misconception. Once injected, the venom is nearly impossible to remove by sucking. Restricting blood flow to the bitten area increases the potency of the venom in that area. If the venom is designed to dissolve tissue (and you concentrate the venom in your arm through restriction), the venom will dissolve your arm tissue much faster than if it ran its course. It is imperative to remain calm (so you do not expedite the venom delivery through your body) and seek help.
Bites are painful. The area will swell and become inflamed and discolored. If left untreated, muscle and bone damage occur as the venom takes its course. Google “copperhead bites” if you are feeling stalwart. Nausea is a common side effect. Allergic reactions may also occur and can cause severe effects.
Skin-shedding is based on growth (which in turn is based on food availability). A well-fed snake may shed once a month or more. Age of the animal is also a factor. Snakes do some pretty cool behaviors pre-shed (the formal term is ecdysis). It takes additional energy to create a new layer of skin (and additional energy to climb out of the old skin), Thus, snakes heat themselves up before and during shedding to facilitate this behavior. In the picture above, I photographed the cottonmouth shedding its skin, giving the eyes a much darker color than normally observed.
It is best we learn to understand and appreciate this unique animals — a crucial part of the Ozark ecosystem and the world around us.
Originally published July 29, 2013
Copperheads and Cottonmouths: State of the Ozarks
PLATE 1 (rural Taney County, October 25, 2011), PLATES 4 & 5 (Bull Shoals Lake, Drury-Mincy Conservation Area, Taney County, Missouri, July 11, 2009), by Joshua Heston. StateoftheOzarks Archive. PLATES 2, 3, 6, 7, 8, courtesy of Ben Dalton.