Cottonmouth

Notice the dark raccoon-like mask on the head of this Western Cottonmouth.

Western Cottonmouth

Agkistrodon piscivorus leucostoma

VENOMOUS


The Western Cottonmouth is often incorrectly referred to as a "water moccasin." Unfortunately, this incorrect name has been used for almost any dark snake found in or near water. As an example, over the decades I have documented thousands of harmless water snakes (genus Nerodia) in northern Harris County. However, I have only seen a few dozen venomous Western Cottonmouths during this time. I would venture to say that the average Harris County resident would refer to ALL of them as "water moccasins!"

Another important reason to call this snake a Western Cottonmouth is that this is the name used by all current books on the subject. You will not find "water mocassins" listed in the index of Alan Tennant's A Field Guide to Texas Snakes, my personal favorite field book for identification and information about snakes in Harris County and throughout Texas.

Now that we have the common name established, let's move on to the identification, habits and habitat of this tenacious snake. As juveniles, Western Cottonmouths are banded with lighter and darker irregular brown bands. However, these bands fade with age and growth, becoming very dark as adults. They are often almost solid black as adults. When full grown, which can be up to five feet in length, the average adult length is about three feet. The Yellowbelly Water Snake, Nerodia erythrogaster flavigaster, is also solid grayish black and is often mistaken for its venomous counterpart. However, the Western Cottonmouth has a wide dark stripe down the side of the head which resembles the mask on the face of a raccoon. This stripe often has a lighter pinstripe above it and a highly contrasting lighter area below it, neither of which are seen on the Water Snakes of our area. Also, this stripe can be seen from a good distance so that you do not have to get too close to it!

As for habitat, The Western Cottonmouth does not venture far from a permanent source of water such as a bayou or pond. In my experience they prefer natural water sources rather than chlorinated water like that found in swimming pools. There are numerous bayous and other waterways throughout Harris County which provide habitats for water-dwelling animals, so unlike the Southern Copperhead, Agkistrodon contortrix contortrix, the Western Cottonmouth is definitely more widespread although uncommon.

I would personally consider the Western Cottonmouth the most dangerous snake in our area due to its tenacious behavior, large size and venom characteristics. Southern Copperheads are more commonly seen, especially in northern Harris County (every Southern Copperhead I have documented from Harris County has been found in either Kingwood, Humble, Spring or Tomball), but their venom is significantly less toxic to humans, making them less dangerous in my opinion. And although Texas Coral Snakes are the most venomous snake in our area, they are not aggressive unless harmed or handled, making bites from this species extremely rare.

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