Friday, August 01, 2008

Three Types of Poisonous Snakes in VA and MD


Copperhead Photo by John White


Timber Rattlesnake Photo by John White



Cottonmouth Photo by John White



The copperhead is the only poisonous snake found across all of Maryland and Virginia. Though its bite is almost never fatal to humans, it can be (rarely) fatal to a terrier who is likely to be bit several times if it finds one in a hedgerow or prowling for mice near a barn.

The good news is that copperheads are not quite as common as some people believe -- most snakes believed to be copperheads are misidentified. Nonvenomous snakes that look a bit like copper heads include eastern milk snake and the northern water snake, but these snakes have round pupils while a copperhead and other poisonous snakes have yes with vertically slit, elliptically-shaped pupils.

Cottonmouths are rarely found far from water and generally only in very swampy parts of the most extreme southern parts of Virginia. Just because you see a large black snake swimming does not mean it is a cottonmouth -- it it much more likely to be a black rat snake.

The timber rattlesnake, or canebreak rattlesnake has a wide variety of color forms (see pictures), but is generally found only in the western parts of Virginia and Maryland, generally in the mountains near rocks and ledges.  As the "canebreak" moniker suggests, however, they are very infrequently found on the coastal plains.
.

20 comments:

Anonymous said...

Interesting article. One thing though - the Copperhead is not a rattlesnake. In fact Copperheads, Agkistrodon contortrix, are a different genus than the Crotalus spp. that includes most common rattlesnakes or the Sistrurus spp. that comprise the ground rattlesnakes, pigmy rattlesnakes and massasaugas. It is more closely related to the cotton mouth or water moccasin, Agkistrodon piscivorus.

The genus Crotalus and Sistrurus are related at the family level as pit vipers or Crotalidae.

bs

PBurns said...

Thanks Bill. You are, of course right. By the time I get to the captions, I am less focused on thinking at than coding sometimes. Make the pictures line up!

P

Chas S. Clifton said...

Eastern rattlesnakes must be more polite. The Arizona specimans that bit Erec Toso and me both struck--and then rattled.

PBurns said...

Actually Chas, you are right that western snakes are less polite. Odd but true according to the literature. Here in small rural and remote parts of Appalachia we still have some "snake handler" religions that routinely drape themselves with rattlesnakes. Not too much of that out West! People get bit, of course, and some die, but there are fewer strikes that you would imagine. Are snakes temperaments different from one species to another? Maybe. My own theory is that it is simply cooler here in the East, and so snakes are more mellow most of the time, and that includes Western Diamondbacks brought East. And, of course, our rattlesnakes are a lot rarer and are almost always found only in very rocky areas. That said, as you note, a snake WILL strike without warning, and not all rattlesnakes have working rattles (they can lose them pretty easily).

So what happened afer you were bit? Skin necrosis? Swelling? Blue language followed by pain and more blue language?

P

Chas S. Clifton said...

I spent two nights in the hospital, summarized here.

If you have to be snakebit, a Tucson hospital is the place to be.

bubbasmom said...

Ummm. Probably nit-picky semantics here, but snakes are venomous, not poisonous. They produce a toxic substance rather than actually themselves being a substance that is harmful.

PBurns said...

Not only nitpicky -- also wrong. Look it up -- it's a question of set and subsets as well as specificity.

"Venom" really only refers to how a substance is administered, and does not speak to toxicity. Since almost all snakes have venom (even such harmless constrictors as black rat snakes), to talk of "venomous snakes" is to talk of almost all snakes.

Poisonous snakes, however, refers to a very small set of snakes. And what these snakes administer (through a variety of slightly different means) is poison. If it is injected by a snake it poison, and if it is administered by a syringe it is poison, and if it is sprayed into the eyes it is poison. The poisons all work by different means, but they all "cause injury, illness, or death by chemical means" and so "poison" is the right word. Venomous is not.

P.

PBurns said...

Glad you didn't "cowboy up" on that one, Chas. Bet you never drive by a root man again, though!

P

PBurns said...

.

Bubba's Mom, look up Colubridae. As Toxin Review notes at http://www.informaworld.com/smpp/content~content=a786926095~db=toxi~order=page, "[Colubridae are] a family of snakes that comprise more than fifty percent of all living snakes. As their fangs are located in the rear of the mouth, they are generally considered non poisonous. In the first part of this review, cases of envenomation by about fifteen kinds of colubridae are described. Notable clinical symptoms are edema, pain, blood coagulation and in some cases respiratory arrest."

Black rats snakes are Colubridae and like most Colubridae have small amounts of poison than slide down grooves in their back teeth. The poison is emitted by the ectopterygoid gland. The poison is not efficiently delivered and generally causes mammals no problems, but does work (at least a bit) on frogs. Considered fully, this means a black rat snake is not so different from most others snakes which do not have enough poison to kill a human. In fact, most of the "highly poisonous" snakes that Steve Irwin used to make a big to-do about handling ("Top Ten Most Poisonous Snakes in the World!!!!), were completely harmless to him even if he had been bitten multiple times. The reason for this is simple: Snake toxicity is determined by the effect of the toxin on MICE, not on humans. On humans, eight of those "top 10" snakes" Steve was playing with could not have had any real impact. In fact, though Irwin liked to make a big to-do about all the poisonous snakes in Australia, the truth is that more people are killed by falling off horses in Australia than are killed by all those "highly poisonous snakes"!

You will notice you never saw Steve Irwin playing clever hand-catch games with a Mojave rattler. That's a snake that WILL kill you, and it's not very big and so it is very difficult to play games with. Irwin was a showman, but he was not stupid. He knew how to sell a story, for sure. And he knew snakes. And he knew when to leave off the part about "not fatal to human, but deadly to mice." Or frogs.

P.

anne said...

Hi! It's fairly common in the Cabin John area (near Potomac, Maryland, along the river) to speak of water moccasins being seen locally. I was taught that this is a local term for a different, non-poisonous type of snake, not actual water moccasins. Have you heard of this, and do you know what kind of snake the locals are referring to? Thanks.

PBurns said...

Yes -- I live about a mile away, and anyone calling them a water moccasin is simply wrong. A bit like calling a dog a hyena.

The large black swimming snakes you see are common black rat snakes which can get pretty big and are very arboreal and water-loving as well. They den along the stone cliffs along the Virginia palisades, and mostly eat mice and rats, frogs and nesting birds and their eggs. After winter denning in the cliffs or in rotten logs and tree trunks, they will often climb trees looking for birds, and drop out of a tree and into the water to swim to a new location.

See >> http://terriermandotcom.blogspot.com/2005/03/black-rat-snakes.html

and

>> http://terriermandotcom.blogspot.com/2007/07/black-rat-snake-on-one-of-farms.html

Patrick

PBurns said...

Mike has left a new comment on your post "Four Types of Poisonous Snakes in VA and MD":

"On humans, eight of those top 10 snakes Steve was playing with could not have had any real impact."

I don't see how you can say that. Eight of the ten? As I recall, the coastal taipan, brown snake, and several varieties of tiger snakes appeared on the program and all are not only well-documented killers of human beings but I've never heard of someone surviving a bite without antivenom.

Steve Irwin was a showman but unless the snakes were defanged, his handling of snakes was dangerous. I have seem him handle "to some degree" a rattlesnake in your area of the country. I wish I could remember that better.

PBurns said...

Mike, there are millions of snakes in Australia, and the snakes detailed here bite thousands a year. Snake fatality (from all types) averages 1.6 people a year as compared to 21 people a year from horseback riding. Bottom line: most of what you have read about Australian snakes is pure nonsense. See this post: "Steve Irwin Was a Big Fat Liar" at http://terriermandotcom.blogspot.com/2008/08/steve-irwin-was-big-fat-liar.html

P.

Anonymous said...

Snakes kill over 100,000 people a year around the world. It's likely the no. 1 killer of humans is the saw-scale adder, which you have mentioned. The name applies not just to a species but an entire genus. This isn't due to its overwhelming toxicity but results from several factors. Saw-scales are common in the Middle East, India and dry areas of Africa and possess an aggressive disposition but the overwhelming reason for the large number of deaths from their bites is that antivenom is not available in the majority of the areas it inhabits. Unavailability of antivenom is the reason for over 95% of the deaths from snakebites.

Australia's taipan, death adder, eastern brown, tiger snake, and common brown are all considered by herpetologists to be at least on par with the small scale as far as lethality to humans from envenomation. However, Australia averages only about one death annually from their bites principally because of the ready availability of antivenom. Another factor is that when a European civilization moves in, a snakes' habitat is destroyed. The venomous bite causing the most emergency room visits isn't from a snake but from the red dot spider which takes to civilization better.
What exactly do you mean by nonsense? If the Australian snakes were attacking as many people as the snakes in Asia and there were no antivenom, I would expect an even higher death total. On another subject, what's up with the red foxes being hit by cars? I've only seen one fox killed by an automobile in my life. Also, what's the story behind the raccoon the woman is holding? Do you have a pet raccoon?

PBurns said...

Mike, this blog is sourced, indexed, and comes with a search engine.

I mention this because I am very busy, and do not chit-chat much and I expect people to research at least a little bit before they type.

Australia, for the record, is mostly barren, and the reason there are so few snake fatalities is that the snakes of Australia are NOT very poisonous. Antivenin is not around if you are bit at a sheep station in the outback -- you just get better for the most part. A lighting strike is far more likely to kill you in Australia than a snake bite.

For the record, the first antivenin developed in Australia was in 1931 for the Tiger Snake, and other antivenin were devoped between 1955 and 1962, but they did not change snake bite mortality much, as it was never high even before antivenin, with horses and honey bees ALWAYS killing more people than snakes. See >> http://www.snakebiteinitiative.org/node/69

As for snake venom toxicity, please see the previous post I sent you to ("Steve Irwin is a Big Fat Liar" and click on the links to read a genuine Australian herpetologist on this. Snake venom is not all the same, and most of it is specifically designed to kill small rodents and frogs, not larger mammals.

As for adders, I was raised in North Africa and know the snake pretty well. It is not that it is that poisonous -- it is that is bites anything that moves within striking distance. It is a very reactive snake.

As for fox, if you do not see dead fox on the road, you are not in an area with very many fox, or you are no very observant. Fox are frequent car victims, as Rudyard Kipling noted in his poem "The Fox Medidates," which you can find on this blog by using the search engine. Fox frequently dine on road kill, and though most fox get out of the way in time, not all do. With about one fox per square mile, the casualty right is pretty steady (though lower than for racoon which can have far higher densities depending on habitat and food sources).

If you want to know about raccoon, use the search engine on this blog and on the main site, and you will learn quite a lot.

P

Anonymous said...

Thanks for the reply. I had read the Steve Irwin post but failed to grasp just how poorly you think the LD50 relates to humans. Apparently, you think a mojave rattler is more deadly to humans than a taipan. I will check out the links and hopefully post back again sometime in the future. I appreciate how busy you are and wasn't attempting to initiate a back and forth conversation. Take care.

Rolan Grant said...

A Canebreak and Timber rattler are one in the same.... the species is called Canebreak further south however, it is the species Timber rattler.

PBurns said...

Thanks for that! Corrected, updated, and smoothed a bit.

MCP2461 said...

Some needed corrections to your posts so the general public at large are not confused ...

The timber rattlesnake, copperhead and the cottonmouth (slang term for the moccasin) are all venomous ... not poisonous. As you pointed out, there are no native moccasins in the state of Maryland. They're are southern snakes found in warmer, wet environments.

The dark brown/gray patterned snakes you see swimming in waterways further north are generally NOT black snakes (black racers or black rat snakes in common terms) These are common non-venomous, semi-aquatic water snakes. However, the water snakes can be very aggressive and will strike when they feel threatened or around their nesting area. They have an anticoagulant in their saliva that makes the wound bleed extensively until treated. And, yes ... the bite hurts.

For the record, timber rattlesnakes are certainly less aggressive then their relatives in the southwest, but their venom is just as deadly. Aside from shutting the body down over time, their venom also breaks down tissue. As stated, copperhead bites are usually non-fatal, but can be if left untreated.

I cannot elaborate further on the moccasin, because I have not studied them extensively, nor dealt with them in the wild. I have -- and still do -- work in the field with all 27 species and sub-species of snakes that are indigenous to Maryland, including the only two venomous snakes: the copperhead and timber rattlesnake.

PBurns said...

ALL snakes are venomous to some extent, and that term means very little, though there is always someone quite sure they are scoring very important semantic points in this arena. :)

The question is what kind of venom, how much, and for what species is it directed? A snake that harms people is not a just a 'venomous' snake (almost all snakes have venom); it is a poisonous snake. Poisonous encompasses venom, but also suggests that the venom is present in large enough doses to harm or kill.

In this geographic area, water snakes fall, I think, into two easy-to- identify groups: The various brown and mottled brown (banded) species, and the red-bellied water snake, which has a very orange undercarriage and jaw. Neither is all black. Racers and Rat snakes often hangout at creek side looking for small prey, and they readily take to the water for escape.