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Identification Key to Texas Snakes by Jerry Cates, EntomoBiotics Inc. Urgent Note: I need digital images of poisonous snakes you have photographed. Please e-mail them to me at jcates@austin.rr.com ... |
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Texas herpetologists have identified 72 separate species and subspecies of snakes native to the state, 15 of which (i.e., 21% of the total) pose a danger to man. These 15 species/subspecies are grouped into two families and four genera. Click on this link to see a list of poisonous Texas snakes. Now you are ready to follow the key to determine if the snake you are studying is venomous. This key has one purpose -- to enable you to determine with minimal clues if a snake is venomous or not. 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, some preliminary questions to get some of the more common snake species out of the way: i. -- Is the snake bright green above, without any markings on its body, with a pale yellowish belly, and with prominent eyes that have distinct, round pupils? YES -- Green snakes found in Texas that have no markings on their bodies (i.e., no stripes, blotches, saddles, spots, etc.) are non-poisonous. 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. ii. -- Does the snake have a triangular head, with prominent jaws and a narrower neck, with large scales on its head -- all the way from its jaws to the tip of its nose, with prominent eyes that have distinctly round pupils, and a body that is more shiny than dull? YES -- These characteristics describe, in general, all the non-poisonous rat and water snakes found in Texas. Contrary to popular belief, the presence of a triangular (arrowhead shaped) head does not automatically mean a snake is poisonous -- although, of course, the venom glands of the poisonous pit vipers tend to make their heads remarkably triangular, too. Rat and water snakes in Texas 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 Texas snake with a triangular head whose eyes have round pupils the snake is non-poisonous. Most Texas snakes with cat's eye pupils are poisonous, but there are a number of important exceptions to this rule. iii. -- Does the snake have an upturned nose, with a pointed tip? YES -- It is a hognose (in the genus Heterodon, four species of which are found in Texas), and is non-poisonous. No other Texas snake has this unmistakable physical feature. 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. iv. -- Does the snake have a long, smooth body with distinct, colorful, lengthwise, unbroken stripes that stretch from its neck to its tail? YES -- It is not poisonous. No Texas snake that has a smooth body and is marked with distinct, lengthwise stripes is poisonous. Garter, ribbon, whip, and lined snakes have a well-defined spinal stripe plus a lateral stripe on each side that is muted in some species. Patch-nosed snakes have a distinct 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-poisonous, though some will bite if provoked. Now -- on to the core of the identification key... 1. Are there rattles at the end of the snake's tail? Notes... YES: This IS a RATTLESNAKE, and IS POISONOUS. 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... YES: This IS a Pit Viper, and IS POISONOUS. All snakes with pits between their nostrils and eyes are venomous, without exception... Go to 6 to identify the species of poisonous pit viper more precisely... NO: Go to 3. 3. Does the snake have red, yellow*, and black bands on its body? *Note: the color must be yellow, not gray or white... But keep in mind that you may be examining an atypical TEXAS CORAL SNAKE (which is POISONOUS) 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, and (1) the snake does not have red, yellow and black bands on its body, (2) is not an atypical TEXAS 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 probably not venomous (BUT see our disclaimer at the end of this key, below). 4. Do the red, yellow 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: Go to 5... NO: If the answer to 5, below, is also NO, this snake should be identified further (suspect the Mexican Milk Snake, Lampropeltis triangulum annulalata). 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 POISONOUS) whose bands are not as distinct as in the typical specimen... 5. Are the yellow 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: The snake is a TEXAS CORAL SNAKE, and IS POISONOUS... NO: Go back to 4. The only Texas snake with banding of yellow, black and red, whose bands completely encircle the body and whose yellow and red bands touch, is the poisonous Texas 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 POISONOUS or B. a RATTLESNAKE THAT HAS LOST ITS RATTLES TO ACCIDENT OR COMBAT and IS POISONOUS, 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 POISONOUS, 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 the identification key for poisonous snakes that follows (when it is finished) will require you to examine the snake's head carefully. WARNING: Attempting to do this with a live poisonous 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. This portion of the identification key is still under construction, and -- when completed -- will enable you to correctly identify the species of poisonous snake you are studying. 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. 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 jcates@austin.rr.com. Click Here to go to: Texas Snakes ... Bugsinthenews |
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