Cottonmouth vs Water Snake

[Ravnos]

This one comes up all the time, especially with people who happen to be walking along a lake, or near a stream and see a snake. As the rule around here goes, if it is in or near the water, it must be a water moccasin, if it is in your yard it must be a rattlesnake or a copperhead. 9 times out of 10, neither are true. Non-venomous snakes far outnumber the venomous ones, venomous generally snakes do not like to be in areas where people frequent. Not to mention, when people slaughter harmless snakes, they could be removing competition and inviting venomous ones in. Most non-venomous snakes have a much higher metabolism than venomous ones, and thus eat much more - removing their food source is the best way to make snakes go away. The vast majority of snakes slaughtered out of fear are completely harmless. I know there are a few of us from Central TX here, cottonmouths do range in southern Travis county - and are found in Lake Travis and its tributaries - like Onion Creek and Town Lake, but I have never seen one in the northern area, like Walnut Creek, Bull Creek, or Brushy Creek. Cottonmouths have -never- been recorded in Williamson county. If you find one there, let me know, I can get our names in a scientific paper. :)

Anyway, to the point. The 'water moccasin' is a term that is generally given to pretty much any snake in the water, it does not refer to any specific species. The species generally in question are water snakes (Nerodia sp.) and the Cottonmouth (Agkistrodon piscivorus ssp.).

Water snakes are very common, found throughout the US in pretty much every body of water you could think of, from small streams to lakes. They eat fish, amphibians, sometimes rodents - pretty much anything they can catch. They are fast on land, and fast in the water - excellent swimmers, they will even dive under water and disappear in the murk. They are often seen on the banks, sometimes in low hanging tree branches, basking. When they are approached, they drop into the water and disappear. They are fairly thin bodied, with round pupils and usually a recognizable pattern. There are numerous species of water snake, 8 or 9 in Texas alone. They are defensive, and won't hesitate to bite if handled - they will also readily release a nasty smelling musk.

http://www.austinherpsociety.org/photos/t-colubrids/blotched_water27.jpg
Adult Blotched Water Snake (Nerodia erythrogaster transversa) from Travis county, TX.

http://www.austinherpsociety.org/photos/t-colubrids/blotched_water7.jpg
Juvenile Blotched Water Snake (Nerodia erythrogaster transversa) - note the pattern difference.

http://www.austinherpsociety.org/photos/t-colubrids/diamondback_water15.jpg
Adult Diamondback Water Snake (Nerodia rhombifer) from Travis county, TX.

http://www.austinherpsociety.org/photos/t-colubrids/diamondback_water3.jpg
Juvenile Diamondback Water Snake (Nerodia rhombifer) from Travis county, TX.

[Ravnos]

Cottonmouths are actually quite a bit different, once you take the time to look at them. They have much larger, broader heads, their bodies are wider and more stocky. They have elliptical pupils instead of round, not that many people want to get close enough to see that. Another distinguishing feature of the cottonmouth is the lateral stripe under the eye - see pics below. They eat the same things as water snakes, and inhabit more or less the same habitats - only they prefer more quiet areas away from people, while water snakes will be just about anywhere there is food.

There are several subspecies of cottonmouth, seperated by locale. In Texas is the smallest, the Western Cottonmouth (Agkistrodon piscivorus leucostoma). There are also Eastern and a Florida Cottonmouths - all structured basically the same, just different size and sometimes their patterning can be a little different.

If you saw my copperhead post, which I don't think anyone did from the lack of reads - you may recognize the genus name Agkistrodon. Copperheads and cottonmouths are closely related, baby cottonmouths even have the bright green tip to the tail to use as a lure. As babies their pattern is much more distinct, and they darken up - some to almost black, as they get to adulthood.

http://www.austinherpsociety.org/photos/venomous/fruitoftheloom17.jpg
Western Cottonmouth (Agkistrodon piscivorus leucostoma) from near Houston.

http://www.austinherpsociety.org/photos/t-agkist/cottonmouth18.jpg
Classic thread posture, you can see how they got their name.
http://www.austinherpsociety.org/photos/t-agkist/cottonmouth11.jpg
Classic resting position, notice head elevated - another useful, but not sure fire, way of telling cottonmouths from water snakes.

Rav

[cirratx]

I live near Lake Ray Hubbard...In my area it is much too 'busy' for cottonmouth's (in my opinion). In the 9 years I've lived here and been near and to the lake, I have never seen one...
Now, up in AR, the pond on the land a cousin has is a different story...it is private, has lots of fish and bugs (turtles compete with the snakes too)...it is not uncommon to find not only water snakes but the cottonmouth. We are careful when we take the kids down to fish, and due to the number of snakes that are in the area we don't swim in the pond as we did as kids.
It's interesting to watch them.

[Ravnos]

According to the range maps I have, cottonmouths haven't been recorded in Rockwall county, but they have in every county around it - seems that they are probably there too just no one has taken the time to find one. :)

Cottonmouths aren't generally offensive, they just want to get away from people - but sometimes its just better to be safe than sorry.

Rav

[Chrisanne]

I've seen Cottonmouths in a small pond near my aunts house in AR too.... there were at least a dozen of them. EWWWWWWW

I think I'll just steer clear of them all thank.

[Ravnos]

Juvenile cottonmouths look quite a bit different than adults:
http://www.austinherpsociety.org/photos/t-agkist/juv_cottonmouth.jpg

In Mexico, they have a very similar species known as the Cantil. They get to about the same size, but are generally more striking in coloration:
http://www.austinherpsociety.org/photos/venomous/cantil5.jpg