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Key to North American Snakes, Photos: Bugs In The News

BugsInTheNews is a VIEWER-PARTICIPANT WEBSITE. This article by Jerry Cates, first published on 17 April 2012, is a revised and updated version of a previous article originally published in 2002. It was last revised on 8 July 2012. © Bugsinthenews Vol. 13:04(03).
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Let’s start with the basics…

So, you’ve found what you think is a snake and you want to know what kind it is. But what distinguishes snakes from lizards, skinks, and other, similar-appearing reptiles? If you are not completely sure it is (or isn’t) a snake, the first order of business is to learn what makes snakes unique among their reptilian brethren. Taxonomically, snakes are vertebrate reptilian animals in the order Squamata and the suborder Serpentes. That is, snakes and other reptiles are members of the

  • Phylum Chordata: animals that have, at some point in their life cycle, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail.
  • Subphylum Vertebrata: chordate animals with backbones and spinal columns;
  • Class Reptilia: vertebrate animals that breathe air, lay shelled eggs (or, less often, give live birth), and have skins that are covered in scales and/or scutes.

Living reptiles are grouped, today, in four distinct orders. The order Crocodilia, which includes the crocodiles, gavials, caimans and alligators, is together represented by 23 extant species, none of them snakes. The order Sphenodontia, once quite diverse, is now confined to the tuataras of New Zealand, of which but two species remain; no snakes here, either. The order Testudines, which contains the turtles, terrapins, and tortoises, is represented by as many as 300 species, but no snakes. Finally, the order Squamata, consisting of lizards, snakes, and worm lizards, is represented by a staggering total of 9,150 species. Squamates are grouped together because they share a number of outward features that often cause them to be mistaken for one another. Of the 9,150 squamate species presently recognized, about 2,900 species are snakes, divided into fifteen families and 456 genera.

  • Order Squamata: reptiles whose skins bear horny scales or shields, and who possess movable quadrate bones that enable them to move the upper jaw separately from the bones of the braincase;
  • Suborder Serpentes: elongated, legless, carnivorous reptiles without eyelids and external ears. In North America, only four families of snakes, with a total of 127 species, are represented. These are the Leptotyphlopidae family (2 N.A. species of slender blind snakes), the Boidae family (2 N.A. species of boa constrictors, native to the west coast of the U.S. and Mexico), the Colubridae family (102 N.A. species of so-called “typical” snakes, all of which are, at least in North America, either non-venomous or with mildly toxic salivas that pose little or no danger to humans), the Elapidae family (3 N.A. species of coral snakes, and one N.A. species of sea snake, all of which are highly venomous), and the Viperidae family (18 N.A. species of moccasins and rattlesnakes, all in the infraorder Crotalinae — the pit vipers — and all of which are highly venomous). Let’s just say you’ll never see these guys on any photo Christmas cards or greeting cards.

Let’s now use the above facts to systematically establish whether or not the animal you are wondering about is — or is not — a snake:

First Question — IS IT A SNAKE?

1. Is the animal’s body covered with small, dry scales?

YES: Go to 2... NO: It’s NOT a snake.

2. Does it have legs?

YES: It’s NOT a snake... NO: Go to 3.

3. Does the animal have moveable eyelids?

YES: It’s NOT a snake… NO: Go to 4.

4. Does it have external ear openings?

YES: It’s NOT a snake… NO: Go to 5.

5. Does it have fins?

YES: It’s NOT a snake… NO: Go to 6.

6. Is the lower jaw separated into a right and left jawbone joined–at the chin–by a flexible ligament, rather than a single, rigid, lower jaw that does not allow movement between the right and left halves? And, does the animal have numerous ribs, rather than only a few pairs of ribs?

YES: The animal IS a snake… NO: It’s NOT a snake.

When people call me about a snake they’ve found, and it has been established that it is, without doubt, a snake, their most urgent question is “Is it venomous?” Our second key answers that question.

Next Question — IS IT VENOMOUS?

The vast majority of our North American snakes are non-venomous, and among those that are technically venomous, many — such as garters, hog-nosed snakes, and similar species —- are only considered venomous with respect to their prey, and are not dangerously venomous with respect to humans. The following key has one purpose — to enable you to determine with minimal clues if a native North American snake you can see from a distance is or is not venomous. Some of the questions have notes attached to them (or linked to other web pages) to give you added information to clarify the question. Read the notes carefully to make sure your answer is appropriate.

First, though, here are some preliminary questions to get some of the more common snake species out of the way:

i. — Is the snake about the size of, or perhaps slightly larger than an earthworm, with the same or slightly darker color of an earthworm, a head that is indistinguishable from the body, a tiny mouth that periodically displays a small, flicking tongue, and small dark eyespots where the eyes would be normally expected?

YES : This is a blind snake, and it is harmless. Blind snakes in the Typhlopidae (introduced) and Leptytophlopidae (native to N.A.) families are relatively common within their range (the extreme southern end of Florida for Typhlopidae; the southern states of the U.S. and all of Mexico, for Leptotyphlopidae), but because they are fossorial, and spend most of their time in underground burrows, we rarely see them.

ii. — Is the snake bright green above, without any markings on its body, with a pale yellowish belly, and a slender head with prominent eyes that have distinct, round pupils?

YES : This is a green snake and all N.A. species are harmless. Green snakes found in North America have no markings on their bodies (i.e., no stripes, blotches, saddles, spots, etc.). For example, only two species of unmarked Texas snakes are bright green in color. One, the smooth western green snake (Liochlorophis vernalis blanchardi), is common in the northeastern United States but is rare in Texas and is usually found only along the gulf coast. The other is the rough green snake (Opheodrys aestivus), which is relatively common in Texas, and is found everywhere except in the panhandle, the far western portions of the state, and the southern tip. Both of these snakes feed on insects and small frogs, lizards and geckos, and are beneficial.

iii. — If you did not observe the snake when it was alive, and are now seeing it — for the first time — in its postmortem state, is its body bright blue in color, without any markings, and its belly pale yellowish in color, with a slender head having prominent eyes with distinct, round pupils?

YES : Green snakes native to North America (see ii, above) turn blue at death.

iv. — Does the snake have a triangular, arrowhead shaped head, with prominent jaws and a narrower neck, a rounded rather than an angular head, with large prominent eyes having distinctly round pupils?

YES : These characteristics describe, in general, all the non- venomous rat and water snakes found in North America. Contrary to popular belief, the presence of a triangular (arrowhead shaped) head does not automatically mean a snake is venomous — although, of course, the venom glands of the venomous pit vipers tend to make their heads remarkably triangular, too. Rat and water snakes throughout North America prey on rats and toads that cannot be swallowed unless the snake has wide, articulating jaws. These jaws give the snake’s head a definite triangular shape. If you see a native North American snake with a triangular head whose eyes have round pupils the snake is non- venomous. Most North American snakes with cat’s eye pupils are venomous, but a number of important exceptions to this rule exist.

v. — Does the snake have an upturned nose, with a pointed tip? And/or does this snake expand its neck and throat laterally — into a broad hood — when it is disturbed or threatened?

YES — It is a hog -nosed snake, and while technically venomous (its saliva is mildly toxic to its prey) it is not dangerously venomous with respect to humans. No other North American snakes have these two unmistakable physical features in combination. The hognose is stout-bodied and often — but not always — has colorful blotches or saddles arranged laterally (side to side) across its back. It feeds primarily on amphibians — mostly toads and frogs — but will also eat other snakes, lizards, and eggs of birds that nest on the ground.

vi. — Does the snake have a long, smooth, slender body with distinct, colorful, lengthwise, unbroken stripes that stretch from its neck to its tail?

YES — It is not venomous. No native North American snake that has a smooth, slender body and is marked with distinct, narrow, lengthwise stripes is venomous. Garter, ribbon, whip, and lined snakes have a narrow, well-defined spinal stripe plus a lateral stripe on each side that is muted in some species. Patch-nosed snakes have a broad spinal stripe bordered by a darker stripe and a lighter lateral stripe on each side. Brown snakes have a somewhat less distinct spinal stripe and a small head. All are non-venomous, though some will bite if provoked. NOTE: garter snakes (all of which are non-venomous) have keeled scales that give their bodies a rough, rather than smooth, appearance, especially when the snake is mature; the garter’s colorful, narrow, unbroken spinal stripe, stretching from head to tail, is not replicated by any of our venomous snakes, whose markings tend to consist of bands, blotches, saddles, and diamonds.

vii. — Is the snake less than 12 inches in length, without any kind of banding, and with a head smaller than or no wider than its neck, eyes with round pupils, and an upper body that is colored tan, brown, olive, reddish, yellowish, or orangish, with a contrasting belly whose background color contrasts starkly with the upper body?

YES — it is probably not venomous. Sorry, but we have to be slightly wishy-washy here, because of the possibility that the snake you are dealing with is an atypical coral snake. All native North American snakes that are venomous — with the exception of our coral snakes — have heads noticeably wider than their necks. Typically, our coral snakes have bands of bright red, bright yellow (or, for the Arizona or Western coral snake, yellowish, creme, or yellowish white), and dark black that go all the way around the body. But coral snakes, like all our other snakes, sometimes undergo a genetic mutation that renders them all-black (melanistic), or all yellowish-white with muted bands and a belly that is not markedly lighter than the upper body (amelanistic or albino). For that reason, you must be cautious when dealing with a small all-black, or light-yellow lightly banded, small-headed snake — such a snake should always be considered a venomous coral snake until proved otherwise by a competent herpetologist.

The risks associated with making a mistake with an atypical coral snake bears elucidation. Because the strength of the coral snake’s venom rivals or exceeds that of every other venomous snake found in North America, you don’t want to take chances. Don’t believe the myth that it has to chew on you to get its venom into your body. Though their fangs are short, they are sharp and the snake’s muscular jaws can sink them into your skin quickly.

Most keys to venomous snakes tell you that our coral snakes have bands of black, yellow and red that completely encircle its body, and that — except for the Arizona or Western coral snake of Arizona, New Mexico, and northern Mexico — the yellow bands are narrower than the red and black bands, and that the red and yellow bands touch each other.

That’s fine if the snake you are examining is a typical specimen, but albinos (with an absence, or a deficiency, of pigmentation) occur once in every 10,000 to 40,000 of its offspring. In an albino Texas coral snake the bands may be missing altogether, or the black bands may be gray or missing while the yellow and red bands may be normal or muted. Melanistic all-black specimens have also been found near the Texas cities of San Antonio and Victoria.

—– This key is purposely arranged to lead you through an identification process that helps you to properly identify a venomous snake whether its coloration is typical or not. That is relatively easy with the pit-vipers, but impossible with the Texas coral snake. For this reason we suggest to all who come across snakes in the wild that, if the snake you find cannot be positively identified immediately, and the snake is either (A) lightly colored or without coloration or (B) totally black in color, ALWAYS treat it as a venomous coral snake until you can positively identify its species.

—– For persons who think about using these keys for snakes found outside of North America, we have a one-word suggestion: DON’T! These keys are for snakes within North America ONLY. Coral snakes found in Central and South America do not follow the pattern of banding found in North American coral snakes. If you use these keys to attempt to determine if a South American snake (or a snake anywhere south of the U.S. border, for that matter) is or is not venomous, you might conclude that a highly venomous coral snake is non-venomous! The consequences of that mistake could be fatal!

Now — on to the core of the identification key…

1. Are there rattles at the end of the snake’s tail?

Notes:

A. This question is about rattles, NOT about whether or not the snake VIBRATES the tip of its tail. Many species of snakes, venomous and non-venomous, with or without rattles, vibrate the tips of their tails when agitated. The sound of a vibrating tail in dry leaves can be moderately loud. If the snake vibrates its tail but has no rattles, the answer to this question is NO. If it DOES have one or more rattles at the tip of its tail, that fact will usually be obvious to the naked eye, the sound of the rattle will be quite loud even when the snake is obviously not vibrating its tail in dry leaves.

B. Rattles can be LOST. It is not unusual for a snake that normally has rattles at the tip of its tail to lose the tip (and its rattles) in an accident or as the result of an encounter with a predator, so the fact that a rattle is not present is not proof, by itself, that the snake is not a rattlesnake. Other questions provided in this key will still confirm that the snake is venomous, even if it is a rattlesnake that has lost its rattles.

C. Answerable from a distance. This question CAN ALMOST ALWAYS be answered without getting within striking distance of the snake. Sometimes, as when the snake has tucked its tail under its body and for some reason is not moving it at the moment, it is not immediately possible to answer this question. When that happens, WAIT. Patience is a virtue under most circumstances and this is an important example. When the snake moves or repositions itself you should be able to see its tail. In the meantime, without getting too close for safety, continue with the rest of the key.

YES: This IS a RATTLESNAKE, and IS dangerously venomous. All snakes with rattles at the end of their tails are venomous, without exception…

NO: Go to 2.

2. Does the snake have a pit, i.e., a distinct, noticeable depression, between its nostril and its eye, on the side of its head?

Notes:

A. This question is appropriate, in most cases, only if the snake is dead and can be examined closely, as this question is NOT answerable from a DISTANCE. Live snakes cannot easily be examined in this manner, and you should not try to do so unless you already know the snake is not venomous.

B. If the answer to this question is definitely YES, the snake is definitely venomous. The pit makes the snake a pit viper. All pit vipers are venomous. However, you may have trouble seeing the pit, or, even more likely, the head of the snake may have been crushed or dismembered so that the presence of a pit cannot be confirmed. If such is the case, answer the question as a NO, and proceed from there. The key will attempt to help you identify the snake as venomous or non-venomous even if you don’t have the snake’s head to look at.

YES: This IS a Pit Viper, and IS dangerously venomous. All snakes with pits between their nostrils and eyes are venomous, without exception… Go to 6 to identify the species of venomous pit viper more precisely…

NO: Go to 3.

3. Does the snake have red, yellow (or yellowish-white), and black bands on its body?

*Note: the color must be yellow or yellowish white, not gray or brightly white… But keep in mind that you may be examining an ATYPICAL CORAL SNAKE (which is venomous) whose bands are not as distinct as with a typical specimen…

YES: Go to 4…

NO: If you cannot examine the head of the snake under study, go to 8. If you CAN examine the snake’s head WITHOUT HANDLING IT, and (1) the snake does not have red, yellow and black bands on its body, (2) is not an atypical coral snake, (3) does not have rattles on its tail, (4) and does not have a pit between the nostril and the eye, the snake is not venomous.

4. Do the red, yellow or yellowish-white and black bands completely encircle its body? Note: to determine the answer to this question, you will have to examine the snake’s belly; the answer is “yes” only if the band completely encircles the snake’s body without breaking at the belly.

YES: If the snake was found east of New Mexico, go to 5.1; if it was found west of Texas, go to 5.2…

NO: the snake is a species in the colubrid genus Lampropeltis and is not venomous.

Important Note: If the answer to 4 is NO, and the answer to 5 is YES, you may have an atypical TEXAS CORAL SNAKE (which is venomous) whose bands are not as distinct as in the typical specimen…

5. 1. For snakes found from Florida to Texas ONLY: are the yellow or yellowish-white bands narrower than the red and black bands, with the yellow and red bands touching each other? Note: remember the saying “Red touch black, friend of Jack; red touch yellow, kill a fellow…”

YES: If the snake was found east of the Mississippi, it is an EASTERN CORAL SNAKE (Micrurus fulvius), and IS dangerously venomous; if the snake was found west of the Mississippi, it is a TEXAS CORAL SNAKE (Micrurus tener), and IS dangerously venomous…

NO: Go back to 1 and start over, AS YOU GOT HERE BY MISTAKE. The only North American snakes found from Florida to Texas with bands of yellow, black and red, whose bands completely encircle the body and whose yellow and red bands touch, are the venomous eastern and Texas Coral Snakes…

5.2. For snakes found west of Texas, in New Mexico and Arizona ONLY: are the yellow or yellowish-white bands about as wide as the red and black bands, with the yellow or yellowish-white bands touching the red bands?

YES: the snake is an ARIZONA (WESTERN) CORAL SNAKE (Micruroides eyryxanthus), and IS dangerously venomous…

NO: Go back to 1 and start over, AS YOU GOT HERE BY MISTAKE. The only North American snake found west of Texas with banding of yellow or yellowish-white, black and red, whose bands completely encircle the body and whose yellow or yellowish-white and red bands touch, is the venomous Arizona or western coral snake…

6. Does it have cat’s eyes, with vertical pupils?

YES: Go to 7…

NO: Sorry, but you got here by mistake. All pit vipers have cat’s eyes with vertical pupils. It is suggested that you go back to 1 and start over if the snake you are examining has an intact head. If the snake you are examining does not have an intact head, go to 8…

7. Are the scales under the tail, immediately following the anal plate, arranged in a single row? This is the same question as 8, but you got here only because you were able to examine the head of your snake.

YES: Go to 9…

NO: Sorry, but you got here by mistake. All pit vipers have single ventral scales immediately past the anal plate, though they are paired near the tip of the tail. It is suggested that you go back to 1 and start over…

8. Are the scales under the tail, immediately following the anal plate, arranged in a single row? This is the same question as 7, but you got here only because you were unable to examine the head of your snake.

YES: This is A. a COPPERHEAD or COTTONMOUTH, and IS venomous or B. a RATTLESNAKE THAT HAS LOST ITS RATTLES TO ACCIDENT OR COMBAT and IS venomous, or C. possibly a non-venomous Texas Longnose Snake, Rhinocheilus lecontei tessellatus (an uncommon snake, found in the western half of the state).

NO: Go to 9…

9. Is the tip of the tail intact?

YES: Go to 10…

NO: This is A. a COPPERHEAD or COTTONMOUTH, and IS VENOMOUS or B. a RATTLESNAKE THAT HAS LOST ITS RATTLES TO ACCIDENT OR COMBAT and IS venomous, or C. possibly a non-venomous Texas Longnose Snake, Rhinocheilus lecontei tessellatus (an uncommon snake, found in the western half of the state).

10. The remainder of this identification key for venomous snakes (presently under construction) will require you to examine the snake’s head, and other parts of its body, carefully. WARNING: Attempting to do this with a live venomous snake may result in serious injury or death. Attempting to do this with a dead venomous snake, even if the head has been severed, can also result in injury or death if the fangs penetrate your skin and the venom glands constrict.

PHOTOGRAPHING SNAKES IN THE WILD

Of course, it is best to let the serpents you find in the wild alone, unmolested (following the old naturalist’s dictum “Leave nothing but tracks, take nothing but photographs“). If you do this, and decide to take photos of a live snake in its natural habitat, you should first be sober. If you are under the influence of drugs or alcohol, you have no business getting anywhere near a snake. Most of the snake bites recorded each year involve inebriated persons. If you’ve been drinking, put the camera away and go in the opposite direction of the snake.

Let me add one more suggestion regarding snakes and alcohol: if you are stone sober, and encounter a snake that you feel needs to be dealt with, don’t automatically ask for help from the nearest individual you see. First make sure that person is also sober and mentally competent. Several years ago, in a town in Central Texas, a woman found a large western diamond-backed rattlesnake in her yard. She immediately yelled for her neighbor, who was standing in his yard, to come and help. She didn’t realize until too late that he had been drinking, and was in no condition to deal with the snake properly. He ambled over, reached down, and grabbed it at mid-body. You can guess what happened next. Though rushed to the Emergency Room, he later died from the effects of the bite…

Besides being sober, you should also be properly dressed. Flip-flops, tennis shoes, or hiking boots that only cover the ankle are all totally inadequate footwear in snake country. Leather boots with 12-inch-or-better uppers are a good start, but wearing denim trousers — over your boots — that extend down to the ankle are an important plus. Don’t tuck your jeans inside your boot, because they won’t tuck all the way down to the ankle. In addition, wear thick woolen hiking socks that will add extra thickness to the protective lining around your foot, ankle, and lower leg. The denim and woolen socks serve to soak up the venom of a snake bite that penetrates your boot’s leather, preventing it from entering the bite channel in your flesh (pit-viper fangs eject venom from a slit in the anterior surface of the fang, not from the fang tip, so even if the fang punctures the skin, if it is surrounded by leather, denim, and woolen socks, much of the venom will be ejected external of the bite wound and soaked up by the socks).

In case you think these suggestions a bit overblown, remember that the snake you are photographing may not be the only snake in your vicinity, and many a photographer has been bitten by a second snake they didn’t notice. That’s why you should never back up while taking photos of snakes (or anything else, for that matter) in the wild: instead, turn around, survey the area you are retreating into carefully, then walk forward into that area while making sure nothing is in your path; then, and only then, turn around and take the photo. Don’t squat down to take photos of snakes in the wild without first making sure there are no snakes nearby that you had not previously noticed. If you are in dense forest or brush land, it may be impossible to do a good survey of the ground nearby, in which case you should carefully and gingerly move to a spot that can properly be surveyed. Don’t risk a snakebite on the tuckus…

If you or someone else are forced by circumstances to take a snake’s life, a thorough examination of its body is usually possible without having to handle it. Don’t touch the snake. The best way is to take postmortem photographs while positioning the body using a stick (so you don’t have to place one of your body parts in harm’s way). The trick is to know what to photograph.

Generally, you should photograph the following portions of a deceased snake for later analysis:

(1). The snake’s entire body, one with the snake on its belly, and one with the snake on its back.

Then, while the snake is on its belly:

—– take at least four closeup photos of the head: one frontally, one of the top of the head, one laterally showing the side of the face from the neck to the tip of the nose, and one that focuses on the eye, showing details of the scales surrounding the eye and of the pupil.

—– take closeups of the snake’s upper body at mid-body, laterally and from above.

—– take closeups of its tail, laterally and from above.

Next, while the snake is on its back:

—– take at least three more closeup photos of the head: one frontally, one of the underchin, and one laterally showing the scales of the lower jaw

—– take closeups of the snake’s belly at mid-body laterally and from above.

—– take closeups of its tail, including its anal vent, and the scale pattern extending from the vent to the tip of the tail.

DISCLAIMER: Snakes, like other animals, are not always easy to identify. Coloration, head shape, and for that matter any of the other physical characteristics of the animal, may be so atypical in the specimen you are examining that a precise identification will be difficult to make. Furthermore, the experience of the investigator, plus that person’s native powers of observation, etc., affect his or her ability to use the kind of key presented here. Don’t rely on this key alone to ascertain whether or not a snake you are examining is venomous. Check the snake with at least two other sources before you make a full determination one way or the other.

IDENTIFICATION TO SPECIES LEVEL

OK, we’ve come to the place where we know, one way or another, if the snake we are dealing with is either venomous or not. Now let’s dig deeper and ascertain just what species we are dealing with. Part of the difficulty in putting together a dichotomous key to the 127 species of North American snakes has to do with how intimate the key assumes you are with the snake you are examining. Most keys assume you have the snake in captivity, or that it is dead and you are able to examine its carcass without worrying if it will bite or not.

Most of the time, however, neither of those situations applies. Most people happen to see a snake in their yard and want to know what kind it is without getting too close. Many take fuzzy, out-of-focus, or long-distance photos of a snake they see and want to use that, alone, to get an idea of the snake’s identity. Or, after someone else describes a snake they saw, they’d like to use that limited information to learn more about the kind of snake that person encountered. Even fuzzy photographs work amazingly well, much of the time, provided we are willing to study them carefully and use them diligently in what may be termed minimal-cue technique. Unfortunately, though, memory alone isn’t very reliable. Our minds tend to play tricks on us, especially when recalling a visual sighting of something we associated with a shocking, frightening experience. Don’t try to rely on memory to describe to yourself or another precisely what a snake you saw for only a moment looked like.

But photographs are excellent, and the better the photos, the better the chance you will be able to use them to identify the snake you saw in the wild. Minimal-cue technique works on the theory that the visual, superficial features presented by a snake, even in a poor-quality image, can provide enough information to allow us to identify its genus, and sometimes even its species. Some herpetologists could argue that that isn’t true, because many–if not most–snake species exhibit a wide range of markings, colors, sizes, and shapes. Adult markings, colors, and sometimes even shapes, differ from juvenile ones. Those same “experts” will often argue that you cannot determine the sex of a snake by merely looking at its external features, but — in fact — many species exhibit noticeably different characteristics for the male than for the female, if you know what to look for (it differs by species). Minimal-cue technique does work, but like sexing from external cues, you have to know what to home on in with your examination.

Furthermore, minimal cue technique is needed. Minute anatomical features are, to be sure, essential parts of a complete identity picture, especially if you must distinguish with absolute certainty, for example, between a juvenile black-necked garter snake and an adult red-striped ribbon snake. But, what if you don’t have all the minutiae at your disposal? What if all you saw was one small section of the snake’s body, with the head and tail obscured from view? Is all hope lost? Aren’t keys supposed to help the average guy or gal on the trail who can’t — or won’t — study the snake they saw up close and personal? This key, at least, is supposed to do that, because, for most of us, minimal-cue technique is an absolute must. In fact, most of us use it (or more often, misuse it) already, and the result, for the snake, is often disastrous.

Not long ago, a good friend of mine pointed out a poisonous cottonmouth he saw while we were hiking along a small creek in northwest Austin. It turned out to be a blotched water snake. Should we assume that every dark-colored snake we see in or next to the water is a cottonmouth? Is every terrestrial snake with orange or copper-like markings automatically a copperhead? Is every banded snake with red, black, and yellow markings a coral snake? And are all snakes that vibrate their tails rattlesnakes? Are snakes with triangular heads always poisonous? Are all snakes that coil up and strike at you when cornered “dangerous”? The answer to each of these questions is no, as parts of this key have already established. With a little extra attention, using minimal-cue technique, most of us can distinguish between poisonous and non-poisonous snakes. This key is an attempt at achieving that goal.

The key presented here, when used properly, can help you get some idea of a snake’s identity with minimal cues. Keep in mind, though, that there are risks involved. Misidentifying a snake can result in a dangerous, life-threatening, even fatal snakebite. If, but only if, you act on the mistaken assumption that a snake you think isn’t poisonous turns out to be, and you get too close or you pick it up, really bad things can happen. Where is the most serious error in this picture? Not in making a tentative identification that turned out to be wrong, but in acting on that tentative identification by placing yourself at risk based upon it.

Please don’t make that mistake!

Though this key tries to limit those risks somewhat, it cannot eliminate them entirely. Even where the key works perfectly, you may still misunderstand something in a way that leads you to an incorrect or unwarranted conclusion. Consequently, it is imperative that you obey the following rules when using this key:

1. Never use this key, by itself, to positively identify a snake. Use another key, from a different source, to corroborate the information shown here, before reaching even a tentative conclusion.

2. Never use a tentative conclusion on the identity of a snake as justification for handling the snake or otherwise placing yourself or another at risk of a snakebite.

3. Always get another competent individual, whose reasoning powers are well known to you and others, to examine the available evidence with you. Consensus isn’t a cure-all, but it beats going alone.

4. Remember that this key applies to snakes native to North America only. It won’t work with snakes in other regions of the world.

The Minimal-Cue Key To North American Snakes

This key, which is under construction and will take several years to complete, assumes you have already made sure it is a snake, using the key “Is it a snake?” to answer that question. It also assumes you have already determined if the snake is venomous or not, using the key “Is it Venomous?”. If those assumptions are incorrect, please go to those keys first, then return to this key to delve more deeply into the identity of the snake you are investigating. Keep in mind as you use this key that it is woefully incomplete and subject to dramatic revision as time goes by. If you are interested in helping with its development, get involved. Post your comments or send me an email. All who are interested in providing assistance are invited to jump in with both feet:

Gross Anatomical Features
01. Distant observation Of Upper Body:
01a. Distinct body markings are evident……..02
01b. No body markings are obvious…………..03
02. Distinct Body Markings consisting of-
02a. -one or more lengthwise stripes………..04
02b. -side-to-side bands…………………..05
02c. -blotches, saddles, or spots…………..06
02d. -neck band only………………………07
03. No Body Markings, body is colored a-
03a. -pink or flesh-tone…………………..09
03b. -green or blue……………………….10
03c. -black or white………………………11
03d. -all other colors…………………….12
04. One or more lengthwise stripes, with a(n)-
04a. -orange, red , or green spinal stripe:
The snake is a ribbon or garter snake in the genus Thamnophis, and is both non-venomous and beneficial.
04b. -black or gray spinal stripe…………..14
04c. -black body, salmon lower side “stripe”…15
05. Side-to-side bands with bands in-
05a. -distinct yellow (or cream, or yellowish white), black, & red bands (not blotches or saddles[see note 05a, below], but true bands that stretch across the snake’s body from side to side) arranged in the following order:
(1) RED-YELLOW-BLACK — If the snake was found east of the Mississippi, it is almost certainly an eastern coral snake (Micrurus fulvius); if found west of the Mississippi, but no further west than El Paso, it is almost certainly a Texas coral snake (Micrurus tener); if the snake was found in western New Mexico or Arizona, it is most likely a western or Arizona coral snake (Euryxanthus poisonous and very dangerous. “Red touch yellow, kill a fellow”
(2) RED-BLACK-YELLOW(OR WHITISH YELLOW)–one of a number of possible milk snakes (Lampropeltis triangulum spp.). “Red touch black, friend of Jack” These are harmless, non-poisonous, even-tempered snakes with gentle dispositions. Assigning a specimen to its correct subspecies is difficult, even for experts.
NOTE 05a: The northern scarlet snake (Cemophora coccinea copei) and the Texas scarlet snake (Cemophora coccinea lineri) have spinal saddles, often with this order of coloration (sometimes yellow is replaced by gray) that may be confused with true bands. If the markings stop at the sides, do not extend beyond the sides to the belly, and are shaped more like saddles than bands, your snake is probably a scarlet snake, not a milk snake. Scarlet snakes are docile, rarely bite when provoked, and are harmless.
05b. -distinct red, black, & gray bands:
The snake is likely a Gray-Banded King Snake (Lampropeltis alterna). Like many other snakes, this species exhibits a wide variety of colorations.
05c. -distinct black and gray bands…………18
05d. -distinct red and gray bands…………..19
05e. -distinct orange, gray, & black bands…..20
05f. -distinct cream, black, & red bands…….21
05g. -distinct orange, black, & red bands……22
05h. -distinct cream & dark gray bands………23
05i. -indistinct narrow, dark & light bands….24
05j. -indistinct, broad, dark & light bands….25
06. Blotches, saddles, or spots:
06a. Large spinal blotches or saddles……….26
06b. Regularly spaced spots………………..27
06c. Irregularly spaced spots………………28
07. Neck-band Only, body otherwise unmarked:
07a. Narrow black/yellow/black neck bands……16
07b. Wide black & yellow neck band with black head…..17
12. Bright or dark green, unmarked body:
12a. Dark green…………………………..29
12b. Bright green…………………………30
29. Dark green body:
30. Blue, unmarked body:
A. If the snake is dead: Both of the two species of green snakes found in Texas, the western smooth green snake (Liochlorophis vernalis blanchardi) and the rough green snake (Opheodrys sestivus), turn blue at death. No other snake native to Texas does this.
B. If the snake is alive: The western smooth green snake (Liochlorophis vernalis blanchardi), which is rarely found in Texas and then almost always along the Texas Gulf Coast, sometimes presents with an olive-green body color, and very young specimens sometimes are bluish-gray or olive-green. The body scales are 15 mid-dorsal rows, and the anal plate is divided.
31. Dark green or dull brown body above:
Adult Mexican or eastern yellow-bellied racer. These snakes are longer than green snakes and more heavy-bodied. Juvenile racers are easily distinguished from green snakes by their boldly blotched patterns.
—NOTE: THIS KEY IS UNDER CONSTRUCTION AND IS A WORK IN PROGRESS. COME BACK FROM TIME TO TIME TO VIEW ADDITIONS… THANKS.
Note: We earnestly solicit comments from anyone who reads this material. If you have any questions about the way it is presented, or the comments provided, please contact jerry.cates@entomobiotics.com.
Once you determine that a snake is either venomous or not, the next step is to identify the precise species of snake involved, so you can learn more about its habits. The third set of keys “what is its species?” will help with that. This set of keys is under construction, and will probably take some time to get into shape.
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References to Scientific Articles, Papers and Books:
  • Cates, J. 2012. Index to North American Snake Families, Genera, & Species.
  • Conant, R., and J. T. Collins, 1998. Reptiles and Amphibians — Eastern/Central North America, Third Ed. Peterson Field Guides. Houghton Mifflin Co.
  • Gloyd, H., and R. Conant. 1990. Snakes of the Agkistrodon Complex, a Monographic Review. Society for the Study of Amphibians and Reptiles.
  • Greene, H. W., 1997. Snakes: the Evolution of Mystery in Nature. University of California Press.
  • Schulz, K-D. 1996. A Monograph of the Colubrid Snakes of the Genus Elaphe Fitzinger. Koeltz Scientific Books.
  • Tennant, A.,1998. A Field Guide to Texas Snakes, Second Ed. Gulf Publishing.
  • Werler, J. E., and J. R. Dixon. 2000. Texas Snakes. University of Texas Press.
  • Wickler, W. 1968. Mimicry in plants and animals. New York: McGraw-Hill.
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BugsInTheNews is a VIEWER-PARTICIPANT WEBSITE.Questions? Corrections? Comments? BUG ME RIGHT NOW! Telephone Jerry directly at 512-331-1111, or e-mail jerry.cates@bugsinthenews.info. You may also register, log in, and leave a detailed comment in the space provided below.

3 comments to Key to North American Snakes, Photos: Bugs In The News

  • Pat

    Hello,

    We saw a snake in our yard today (Northeast TX rural land). Your key stops short of my being able to identify it. It was probably a little bit longer than 2 feet. It was black all over with tiny little white “dots” or “slits” all over it…very uniform like a window screen would be. It was about 1″ thick. It’s head was the same…all the snake looked the same. It did not appear to be poisonous. Head was smooth…not sticking out on sides. Didn’t see its eyes, but I did take a picture of it. It just sat there until my husband moved a stick close to its tail, and it slithered off to hide under some wood in a pile.

    Any idea what kind it is? My husband thought it might be a type of king snake.

    Thanks!

  • most likely a speckled (common)king snake. often large, up to 6+ft yellowish spots on scales, ROUND PUPIL OF EYE, no pit between nose and eye, yellowish belly. Often exhibits ‘rattling’ of tail attempting to intimidate predators, but no rattles present

  • Sherry Farnham

    Thank you for the info. I live in a developing area of Georgetown & many neighbors seem to believe the only good snake is a dead snake. I’ve sent several people to your site because they could at least be informed before they start killing. I recently found a fold out brochure at a local store & bought one for my grandchildren since we spend time outside turning over rocks in search of interesting bugs, scorpions, &/or snakes. We don’t kill any of them, we look & leave them or let them leave. They took the brochure to Tenn when they moved. I haven’t been able to locate anymore of the laminated brochure/pamphlet I purchased & the new Texans need something they can look at & read, before they kill a lot of natural inhabitants.
    Is there a site that has pictures of common non-venomous snakes? I could print off a few copies on my color printer & hand them out to the flower gardeners
    that seem hell bent to kill anything that slithers. Thanks, Sherry

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