Pit Vipers At Harmony Hill
Though the calendar has now been flipped to the month of March and spring is right around the corner, in South Carolina it has been warming considerably and the signs of that annual rebirth have been popping up everywhere. Days are getting longer, but cooler temperatures are apt to come back to South Carolina perhaps once more before mid-April. Birds have begun their annual migrations north, but the warmth that has been around the last month has been sufficient to get snakes active. Being exothermic, or cold-blooded as I was taught in elementary school, snakes take environmental warmth and warm themselves to activate processes such as locomotion and digestion.
As we discussed in our last visit, there are 38 species of snakes in South Carolina, with only six of those being venomous. Now, there are many that refer to venomous snakes as poisonous, whereas you will hear me only refer to them as being venomous. There is a clear distinction between the two terms, from a biological and scientific point of view. The difference is found in the way a creature delivers toxins, be it actively through a specialized anatomical apparatus or passively through indirect means. Venomous animals, such as some species of snakes, spiders, bees and wasps use fangs and stingers to deliver toxins via injection. Poisonous animals, such as some species of frogs, toads, butterflies and moths are only harmful if eaten or touched. As each of the six species of venomous snakes found here actively delivers toxins through modified teeth known as fangs, they are venomous and not poisonous. Why don’t we start out with a look at some of our venomous snakes?
Five of our venomous snakes belong to a group known as pit vipers. An amazing group, the pit vipers have evolved an incredible ability that has made them the ultimate survivor and predator, especially under the cover of night. As their name implies, members of the Viperidae family, such as Pygmy Rattlesnakes, Canebrake Rattlesnakes, Eastern Diamondback Rattlesnakes, Eastern Cottonmouths and Copperheads, have pits located on their faces between the nostrils and eyes, usually located below either of those facial features. These pits are highly evolved heat sensing organs that serve a number of uses. Being sensitive enough to determine changes in temperature gradients of as little as 1/1000th of a degree, the pits add another dimension of “vision” to the snake and allow it to “see” temperatures more accurately than most heat sensing cameras used by first responders.
Being able to see specific hot and cool changes upon the landscape allows members of the Viperidae family to not only see endothermic prey cloaked in darkness or camouflaged by cryptic colors, but also to find cool places during the heat of the day and warm places on cool nights. While doing snake research years ago at Carolina Sandhills NWR, one of the criteria I would look at when I captured a live snake laying in the road was the surface temperature of the asphalt versus the air temperature at time of capture. Overwhelmingly, we found their ability to detect the warmth of the asphalt roads inside the protected boundaries of the refuge gave them a chance to actively use them as warming surfaces.
Pit vipers also have the most evolved dentition found in the serpent world. They have solenoglyphous dentition. In ancient Greek, “solenas” was the word for tube or pipe and “glypho” referred to a carved work. When the two Greek words are combined to describe dentition, it literally means, “having teeth like tubes”; which perfectly describes fangs designed like hypodermic needles. Viperidae snakes here have independently movable front fangs that are markedly longer than any of their other teeth. In some cases these fangs are about half the length of the snake’s head, which isn’t a problem as they can open their mouths nearly 180 degrees. Viperidae actively inject venom by compressing muscles surrounding specialized venom storage cavities, called lumens. Though their hemotoxic venom isn’t as potent as the neurotoxic venom of the Coral Snake, they are capable of manufacturing and injecting much more in a single bite than a Coral Snake ever could. (More on that beautiful snake when next we gather this week!)
Our smallest pit viper is the Pygmy Rattlesnake (Sistrurus milliarius). You will sometimes see it also spelled “Pigmy”. The scientific name means “Having the nature of a rattle and resembling millet”, referencing the tiny rattle (which is often nearly impossible to hear) and the cryptic coloration that can resemble grains of millet on its back. See the photo I took of a Pygmy 14 years ago to see the “individual grain pattern”. A very old Pygmy Rattlesnake can max out at a length of just shy of 2’, but the average length is between 10”-15”.
During the spring and summer of 2007, I captured and studied 111 Pygmy Rattlesnakes while conducting research. I found a Pygmy Rattlesnake which was 21” long and it was, by far, the largest Pygmy I’ve ever seen. They also come in a wide variety of colors; but, the pattern tends to stay the same, regardless of the overall color. (Side note, they are also pretty common in Florida. You may have seen a few down there.)
Pygmy Rattlesnakes are considered a much older species than the other rattlesnakes in South Carolina (or North America, for that fact). Their venom is weaker than their pit viper relatives and their head scales more closely resemble some nonvenomous snakes. And, with such a small rattle, the general consensus among biologists is that Pygmy Rattlesnakes predate the other pit vipers by several thousand years.
Our next largest rattlesnake is the Canebrake, or Timber, Rattlesnake. They are the same species (Crotalus horridus); but, are referred to as Canebrake Rattlesnakes in most of the Sandhill and Coastal Plain areas of South Carolina. When you get into the Piedmont and Mountain areas of the state, the snake is called Timber Rattlesnake. Their scientific name means “Horrible castanet”, which is both funny and sad. They do have a type of castanet on the end of their tail, but I would argue they aren’t horrible at all!
They are a beautiful tan or beige color, with dark chevrons down the length of their body. There is also a rust-colored line that runs along the spine of the snake. If you’ve seen them in the forest or in a field, you know how quickly they can disappear into the leaf litter or vegetation. There was a 3’ Canebrake Rattlesnake that would often hang out near one of the mist nets at a bird banding station I operated and, even with me knowing to be vigilant and have my awareness high, that snake would often be very near without me seeing it until I was close to it. (Thankfully, it was a very well-behaved snake, and it knew I wasn’t a threat.)
Our last, and largest, rattlesnake is the Eastern Diamondback Rattlesnake (Crotalus adamanteus). With a common name like that and a scientific name meaning “castanet with diamonds)”, it goes without saying the large diamonds on the snake are the identifying feature. Unlike their western counterpart, the Eastern Diamondback does not have a black-and-white striped tail before the rattles. (This gives the Western Diamondback Rattlesnake the colloquial name “coon tail rattler” in much of its range)
Eastern Diamondback Rattlesnakes are big. There is no other way to put it. It is not uncommon for a mature Eastern Diamondback to reach 6’ in length. The last time I checked, the largest measured was 8’ long. It is also not out of the question for these snakes to weigh in at 8-10 pounds. They are big snakes! And, like the Pygmy Rattlesnake, they are quite common in the palmetto and pine forests of Florida.
The genus, Agkistrodon, contains both the Copperhead and Eastern Cottonmouth. The genus name translates to “tooth like a fishhook” and implies the large fangs are, in fact, curved in shape. Let’s look at our last two pit vipers…
The Copperhead (Agkistrodon contortrix) is, in my estimation, the most common venomous snake found in the lower piedmont area. They are most often found in drier, more upland areas from their cousin, the Cottonmouth. In fact, their family relation and that tendency has led to their colloquial name of “Upland Cottonmouth”.
True to their common name, they are a beautiful copper color overall, with darker hourglasses wrapping around their width. One quick aside, there are “northern” and “southern” subpopulations and the way to tell them apart is that “northern” Copperheads have spots between their hourglasses, while the “southern” Copperhead is cleanly colored in just copper and hourglasses. Where their ranges overlap and they interbreed, there will be intermediates with a nominal number of spots accompanying their hourglasses.
Copperheads are able to make their smelly musk into an aerosol and can spray it around themselves and towards a threat. I learned this lesson the hard way while doing the snake research at Carolina Sandhills NWR in 2007. I had a new Jeep Grand Cherokee and stopped in the road to catch a Copperhead in the middle of Wildlife Drive, only to have it spray a fine and invisible aerosol of musk at me. I was not at all affected, but the musk got into the air conditioning filter and vent of my Jeep and there were a couple years afterwards where you could smell hints of that musk after turning on the air conditioner for the first time in the spring. Lesson learned!
Like its cousin, the Cottonmouth, young Copperheads are born with lime green tails that they use as bait to lure in prey. They will hide under leaf litter or vegetation and wiggle their lime green tails out in the open, attracting everything from frogs and toads to worms that they hope to dine upon
Finally, in our long lesson on the pit vipers of SC is the Eastern Cottonmouth, or Water Moccasin. Their scientific name of (Agkistrodon piscivorus) and means “fish devourer with fishhook tooth”. They are, without any competition, our most aquatic venomous snake in the Harmony Hill area. They love to be in and around slow-moving water, like creeks and swamps. While they can be found around ponds, they don’t tend to like large water and aren’t found around lakes that often. They can also be found in dry areas, but that is when they are moving from one aquatic area to another.
Harmony Hill is on the very northern edge of the range of this species. They will eat anything that will fit in their mouths and I do mean ANYTHING that will fit in their mouths. While they make a very good living eating fish, they will eat very young turtles, alligators, mammals, birds and other snakes. While doing the snake research, I captured a couple of Eastern Cottonmouths with large, circular scars on their sides (about the size of a dime). I was confused as to what may have caused the scars, particularly since they were somewhat the same size and found on separate snakes. I posed the question to a herpetologist friend who said it was likely the result of catfish barbs that were poked through the snake, from the inside… a last gasp of survival from a catfish being devoured by the snake.
This species has the reputation of being aggressive and, to hear my grandmother tell it, they would all but follow you home and set your house on fire. She told me tale after tale of Eastern Cottonmouths chasing people to bite them. Turns out, she wasn’t exactly right. Cottonmouths will stand their ground and don’t retreat like other snakes. They will gape their mouths open, showing that cottony white mouth and even reinforce it with a hiss. However, they don’t chase, and they don’t readily bite. The vast majority of bites are in response to being harassed or when people are trying to kill them.
I’d like to point out that situation appears to be a common thread among many snake bites from the species we’ve learned about today. They don’t actively seek to bite humans and most snake bites are the result of the snake defending itself.