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ID-ing Snakes In The Garden - Cottonmouth

16 years ago

Continuing with the Snake ID series. Below is my original post on how to tell a cottonmouth or water moccasin from any ol' brownish looking water snake you might run across. There are several harmless water snakes that often get misidentified.) The post below is long, but if you read it and look closely at the pictures, I'll bet you will be able to tell if you are dealing with a venomous cottonmouth or not. Hope it helps some of you!



The Cottonmouth, Agkistrodon piscivorus, has 3 subspecies, but we are going to concentrate on the FLORIDA cottonmouth, Agkistrodon piscivorus conanti. (Oh, boy...we get our OWN state subspecies! YAY...I think?) All comments, descriptions, etc, that follow will apply specifically to OUR cottonmouth, though the other subspecies are somewhat similar.

Let's start with some general info. Cottonmouths are large, heavy-bodied water snakes that primarily eat fish. (Hence the "piscivorus" portion of their Latin name.) Naturally, if fish make up most of your diet, you need to live near water, and cottonmouths do. Their favorite habitats include swamps, lakes, rivers, irrigation ditches, canals and most any sluggish body of water, though they CAN be found in clearer, faster moving streams once in awhile. But generally, the dark, slow moving streams and lakes in Florida are their favorite places.

If you live on waterfront property, or back up to a canal, you may very easily find yourself confronting a basking cottonmouth one day when you go to mow your lawn, or fish from your dock. If you don't live near water, it is still a good idea to recognize these snakes, since you are bound to be AROUND a lake or stream at some point or other.

Cottonmouths, like most pit vipers, are live bearers and the females give birth to 1 to 15 babies at a time. The young range in size from 7" to 13" at birth, and they arrive fully loaded with venom and ready to bite. Their venom is haemotoxic, and is very complex. It works on the blood tissues, and causes exceptionally nasty wounds. It is designed for killing prey and starting the digestive processes on the animal even before the snake has swallowed it. Snakes are very vulnerable right after they eat. They can't move very fast with a whole rat or rabbit inside them, so before their stomach acid even begins to digest the animal, the poison has started to break it down from inside, speeding up the entire process. And that's just what it does to the tissue surrounding a bite begins to eat away at it and cause ulceration. You do NOT want to get bitten by a pit viper. So I hope these photos and comments will help you make a positive ID and keep you safe!

The coloring of the baby moccasins is very different from the adults. They are born with a strikingly colorful pattern of bands and markings that gradually darken and fade as the snake ages. Adults are often nearly completely black. But because the snake goes through so many colorations as it ages, it is difficult to identify them by color or markings alone. (No little rhymes to recite and poor Jack isn't even mentioned at all!) So, we have to go by a couple of other field marks, in addition to head & body shape, and behavior. And in Florida, we have one sure-fire identifier that really clenches it.

Let's start with some photos of young snakes and work our way up through some color variations, and I will show you the marking that remains consistent throughout.

Here is a young cottonmouth, coiled up, ready for action. Notice his beautiful splotchy markings, intended no doubt to provide camoflage for him as he is lying in leaf litter or other debris.

Here is another very young moccasin. In this odd pose, you can just barely see that he has a yellow tail tip. This is only found on very young cottonmouths, and it is believed they twitch this tail tip in the water as a lure for small fish or other critters. Heavy bodies, even at this stage, and wedge shaped heads that are wider than the necks are good clues that we are looking at vipers here.'s my secret weapon for the ID of cottonmouths... each of these has a very dark brown or black stripe that runs the length of the cheek through the eye to the back of the head. (Hereinafter we will cleverly refer to this as the "cheek stripe.") This wide, dark stripe, usually set off by cream colored areas above and below it, is visible in ALL colorations of the FLORIDA moccasin. It doesn't always show up in the other subspecies, I'm afraid, but for US, it is diagnostic.

In this second image, you can also see two dark marks on the front of the moccasins nose that run downward towards its mouth. These are also very good field marks...trouble is, you almost half to be eyeball to eyeball with the snake to see them, so I'm gonna focus on that cheek stripe, as it stands out nicely, even from several feet away.

The next photo is of a larger moccasin...still showing a lot of color, but not as much pattern as the younger snakes. I'm not totally sure this is a FLORIDA moccasin, as I can't see the side of the head very clearly, but this is typical of many youngish snakes, and I wanted to show you this image for 2 other reasons. First of all, the snake is gaping, exposing the very pale lining of his mouth in the behavior which gives him the name "cottonmouth." I have never seen another snake do this consistently, though that may be my limited experience. But cottonmouths DO. If there is one lying in your path, the chances are very good he will begin this display as soon as he senses your approach. It is his way of alerting you to his presence and announcing that HE doesn't intend to move, so YOU better, if you know what's good for you. (Unlike most snakes, cottonmouths do not tend to hurry away at your approach. That's why I think of them as being SO dangerous. They just lie there like great scaly lumps and gape at you, hoping you will see them and not step on them.)

The second interesting thing about this photo is how clearly it demonstrates that snakes DO have tails. They are NOT "all tail" like some people have asked me in the past. On slender snakes, it is often hard to tell from the TOP where the snake's tail begins, but cottonmouths are so thick through the body and then taper so quickly at the tail that you can really see it. A general heavy shape and short tail are good indicators that you need to take a closer look to be sure what you are dealing with.

Another young snake, much darker in color, resting on a palmetto frond, and gaping away in his "DANGER, I'M A BAD BOY TO MESS WITH mode." You can't see his cheek stripes from this position, but I guarantee you they are there, and you CAN see his "COTTON" mouth, another SURE sign.

This is an older snake, beginning to darken up quite a bit, with some pattern still visible, but obviously on his way to becoming the near black of the big boys. BUT...take a look at that head. See it? YEP, that CHEEK STRIPE is clearly visible, and totally diagnostic.

Another large moccasin, with cheek stripes you can just see from this angle, but he IS gaping nicely, and announcing quite loudly, "I'M A COTTONMOUTH. Don't TREAD on ME." Look how dark his coloring is and how faint the pattern has become. See why you can't go by color alone?

A nice, FAT one crawling away, so it is hard to see his head, but alerted by his general size and width, one should be looking closely enough to see that yes, the CHEEK STRIPES are there, though it isn't a good angle to spot them. However, this is NOT a bad angle to be viewing a cottonmouth from, as he is LEAVING. And that's probably a GOOD thing.

Now for some shots of them in the water. Here is a wonderful view of a really dark adult, swimming ON TOP OF THE WATER. This is an example of a diagnostic BEHAVIOR. Other water snakes swim underwater or with just their heads above water. The cottonmouth swims with his entire body gliding on the surface of the water. This image also shows what we mean by the wedge shaped head which is wider than the neck. Other water snakes do not have heads shaped like this,though I wouldn't try to go by that in identifying a snake, as it is often hard to tell at a glance.

A wonderful photo of a younger, still patterned moccasin that should leave no doubt in your mind as to what it is...first of all, you can clearly see THE CHEEK STRIPE. And secondly, it is swimming with its entire body on the surface of the water. Both of those are dead giveaways.

Another head shot of a still-patterned snake, just to give you another look at that diagnostic CHEEK STRIPE.

These two pictures show some interesting behavior...this large moccasin found a puddle filled with mad toms (wee little catfish) and was FEASTING on them. He totally ignored the photographer and gorged himself. In the first shot, you can see his head sticking out of the water. It was so shallow that he was really crawling rather than swimming. (NOTE CHEEK STRIPE, PLEASE). In the second shot, he is busily swallowing one of the little fish. You can see he is almost black, but that cheek stripe shows just as well as it did when he was young and fully patterned.

And finally, just to show you what happens if you need to have a moccasin removed from your property. I like this shot because it gives you a good idea of how big and truly HEAVY these snakes are. And you can see the short tail clearly...AND...guess what else? Aw, come on...say it! You KNOW you wanna! YES!! You can still see that CHEEK STRIPE.

Okay, that wraps up the basic ID on the cottonmouth. I know it was long, but you really need to see a lot of examples on this guy. His coloring is just too variable to expect each snake to look the same way, but I hope you have learned that there are some things that are always diagnostic. Now you can relax when that harmless brown water snake crawls up on your dock!


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