Q. In a recent column you said bushmasters are the largest pit vipers in the world. I was told pit vipers have vertical pupils, which is one way to determine if a snake is venomous. However, you included a photo of one taken by your grandson that clearly had round pupils. Are bushmasters different from other pit vipers?
A. No, but like other pit vipers (which include cottonmouths, rattlesnakes and copperheads) their pupils dilate in the dark and become rounded. That photo was taken at night in a tropical jungle when the snake’s pupils were fully dilated. The shape of the pupil is not a surefire way to classify whether a snake is venomous. It is true that most (but not all) harmless U.S. species have round pupils. However, to confound the issue further, nonvenomous pythons and boas have elliptical pupils whereas venomous cobras and coral snakes have permanently round pupils. On a dark night, when their pupils are fully dilated all snakes have round eyes.
Q. I found a large snake in my garage when I went to get in my car this afternoon! I think it is a rat snake. The attached photo shows lumps extending down its whole body. Is it so “crinkly” because it has just eaten? I don’t want to kill it but, unfortunately, when I used my rake to try to get it out of the garage, it went behind the bricks in the corner and now I can’t find it. Also, do snakes look for a cool spot this time of year or was it just looking for a quiet spot to digest whatever it had just eaten?
A. That is a harmless rat snake. But the bumpy body from head to tail is not because it has eaten. That is a behavior called kinking, a not fully explained behavior of rat snakes. Some herpetologists consider kinking a response to feeling threatened. Others have reported it occurring without apparent provocation. It is excellent camouflage in the woods because it makes the snake resemble a stick—not so effective on a garage floor. The snake in your garage may have been looking for food (rats, mice, birds) and will probably leave when it gets a meal or cannot find one. But it might find a shady garage more comfortable than many other outdoor habitats. If it decides to stay you will have no problem with rodents this summer.
Q. I heard recently that someone in North Carolina found a completely dark, almost black, copperhead without the standard orange and copper banding that is that snake’s trademark. If this is valid, can the same be true for other venomous snakes, like rattlesnakes and cottonmouths? And how am I supposed to know if a snake in the woods is dangerous?
A. What you have heard is true. Many snakes, as well as other animals, can display a wide genetic variation in color pattern, sometimes making it difficult to use standardized descriptions for identification. Melanism, in which a surplus of dark pigment results in an individual snake being almost black, is extremely rare in copperheads, although harmless racers, hognose snakes and rat snakes are often solid black. Nonetheless, unless you are very familiar with snakes, my recommendation to anyone encountering a snake anywhere in the country is to enjoy watching it from a few feet away. Do not try to catch it or kill it. Enough native snakes in the southern half of the country are venomous to make caution the byword. The rule should be “never interact with a snake because you think you know what species it isn’t; only interact when you know for certain what species it is—and that it is harmless.”
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