PIT VIPERS IN AMERICA

Even those who have lived in America’s metropolitan areas all their life are aware of, or know something about poisonous snakes. As of this writing there are thirty-one recognized species and seventy sub-species of rattlesnakes that are currently classified. In the United States, Arizona holds the record for the most diverse number of rattlesnakes in the lower forty-eight states. The literature reports seventeen different rattlesnakes are known to exist in Arizona. Other than the mountain peaks above 11,000 feet in California and 9,000 feet in other parts of the lower forty eight states, the only areas of America where you are unlikely to find a rattlesnake are northern and eastern Maine, northeastern Wisconsin, upper Michigan, northern Minnesota, northeastern North Dakota, the north west coastal area of Oregon and western Washington. I have spent considerable time in the northern and central Adirondacks of New York and the only snake I saw there was a Ribbon Garter. If rattlesnakes exist in the Adirondacks, the population must be quite low.

This article will discuss a few of the more common poisonous snakes you might encounter in various regions of the United States, and provide some information about each of them.

Rattlesnakes, Copperheads and Cottonmouth snakes are venomous pit vipers which have a heat sensitive pit on either side of the head that is larger than their nostrils. Their young are born alive. They have a triangular head and vertical pupils. A few researchers have tried to classify the aggressiveness of various species, and there are measured differences in the toxicity within the numerous species and subspecies. But, there are many possible variables if you are bitten by any of the poisonous snakes. The poison of some species is more toxic than others. The size, and therefore, the quantity of poison delivered would be a factor. Perhaps the snake utilized its poison prior to your being bitten, and the quantity of toxin you receive might be less. Some “bites” can be delivered without the snake opening its mouth, and no poison is injected. The best advice is to treat every bite as potentially dangerous.

Perhaps the most dangerous rattlesnake in North America is the Western diamondback rattlesnake (Crotalus atrox), because more people are bitten by this snake than all other poisonous snakes combined in the United States. The primary reason for this is the population density of diamondback rattlers is significant, and it inhabits a large area of America’s southwest. It is prevalent in most of Mexico, large areas of Arizona, New Mexico, most of Texas, southern Kansas and southern Colorado, and western Oklahoma. The Western Diamondback can reach a length of eighty-nine inches, and weigh as much as fifteen pounds. It is almost as large as our country’s largest rattlesnake, the Eastern Diamondback (C. adamanteus), and size is important as it relates to the amount of poison that could be delivered in a bite. However, ounce for ounce, the Western Diamondback’s venom is more potent than the Eastern Diamondback’s.

Timber rattlesnakes (C. horridus horridus) are common in the state where I grew up and attended school in Pennsylvania. In certain areas of the state the population is quite high especially from the southwest Alleghany Mountains through the north central and western areas of the state to the counties along the northern border. Likewise, there are areas of Pennsylvania where the population is exceptionally low or completely displaced due to development, agriculture displacement and other limiting conditions. The Timber rattlesnake can be as large as six feet in length, but the average size varies from three to four and half feet for adults. This short tempered snake’s bite causes rapid swelling, a large bruise and hemorrhaging in the area of the bite. Fatal bites are possible from Timber rattlesnakes without proper medical attention. The largest I have measured was fifty-four inches. Though I have never been bitten by a venomous snake, I had two close calls in “Penn’s Woods” with Timber rattlesnakes, and one from a Copperhead (Agkistrodon contortrix mokasen). This pit viper inhabits much of Pennsylvania, and is of the same Genus as the Cottonmouth, which does not inhabit the state, but is found to the south in the coastal plains of Virginia and throughout many of the southern states.

Where I now live in north western Wyoming and during my time in western North Dakota, I have only encountered Crotalus viridis viridis, the Prairie rattlesnake, a sage colored pit viper (viridus is Latin for “green”), which rarely reaches 5 feet in length. The majority range from two to three and half feet in length. The Prairie rattlesnake’s poison is composed mostly of myotoxin, which rapidly destroys muscle cells and causes paralysis. The toxin is designed to incapacitate small prey quickly so it does not escape. The Prairie rattlesnake is not to be trifled with as its venom is unusually potent and rivals that of the Timber rattlesnake in spite of its small size.

There are four subspecies of Copperheads in the United States. The Northern copperhead (A, contortrix mokasen), which has been identified in Massachusetts, Pennsylvania, Central Illinois, south to the higher elevations in Mississippi, and northern Georgia, and west to the Mississippi River. The Osage copperhead (A. contortrix contortrix) occurs west of the Mississippi River, in extreme southeastern Iowa, northern and central Missouri into extreme southeastern Nebraska, eastern Kansas, and extreme northeastern Oklahoma. The Southern copperhead inhabits the lower Mississippi Valley to southern Illinois and in the southern Coastal Plain from extreme southeastern Virginia to Texas though it is not in Florida. The Broad-banded copperhead inhabits the Great Plains to central Texas.

Most rattlesnakes are readily identified by the rattle on their tail. Pit vipers are born alive, and rattlesnakes are born with a rounded pre-button on their tail. Young poisonous snakes are equipped to deliver a poisonous bite at birth. Research has shown that the small amount of toxin a baby Prairie rattlesnake can deliver is three times more potent than that of the adult. The number of rattles are not related to the age of the snake, but are related to the number of times the snake sheds its skin each year. The frequency of shedding of the skin depends on how much the snake eats and is growing, and in most instances they shed from two to four times a year.

I have no personal experience with the Cottonmouth (Agkistrodon piscivorus “fish eater”), and that is just a matter of dumb luck, because I could have had a bad experience with this nocturnal snake when I went swimming alone at night in a swamp pond in South Carolina after enduring the heat and humidity of hiking an especially hot July day in a wooded South Carolina swamp. It was one of the many fun things you do in Boot Camp. Some of the advantageous of youth are being young, dumb and the belief you are immune or invincible. Luckily for me most of those traits didn’t carry over to my advanced years. The Cottonmouth length can go to four feet, but the record length is slightly over six feet. It is our largest pit viper without a rattle. This snake often displays its white “cotton colored” mouth to warn off intruders. Interestingly, young Cottonmouth’s coloration closely resembles that of the Copperhead. Speaking of coloration during a herpetology exam I came across three specimens of snakes that were distinctly different colors. All had the classic hour glass-shaped markings of a Copperhead, however the predominant color of one specimen was brown, another was almost orange or pink, and the third was extremely dark, almost black. But, all the specimens had a keeled scale. That is, a center ridge on each scale near the anal plate rather than a smooth scale without the ridge. That signifies the specimen is a poisonous snake, and without a rattle, it had to be the only non-rattle poisonous snake found in Pennsylvania; the Copperhead. The point the professor was driving home was “do not depend on color alone.” All three different colored specimens were A. contortrix mokasen, the Northern Copperhead.

All the pit vipers are poisonous. As for the few discussed here the Western diamondback is likely the most toxic of America’s rattlesnakes, the Eastern diamondback next principally because of its size and the potential amount of venom it could deliver, the Prairie rattlesnake and the Timber rattlesnake would rank third. However, studies indicate that toxicity is highly variable even among snakes of the same species.

On average there are approximately 7,000 people that suffer a poisonous snake bite each year. Forty-four percent of those bites occurred accidently, but fifty-five percent of the bites resulted from the victim’s handling the snakes. Approximately 0.2 % of all snakebite victims die each year, and most of those received no medical attention.

You could encounter many different types of rattlesnakes than the few listed here. Your chances are high for that to occur if you live or hike extensively in Arizona.

This entry was posted on 29. August 2008 at 02:05 and is filed under Natural History Series. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response or trackback from your own site.