Monday, November 4, 2013

5 Ways How to Tell the Difference Between Cottonmouths (Water Moccasins) and Copperheads

     Cottonmouths, Agkistrodon piscivorus, and Copperheads, Agkistrodon contortrix, are venomous snakes that are closely related and frequently encountered in the United States. Because these two species may seem similar at first glance, they are often confused for one another. I first noticed this trend on Twitter; if you follow me there then you already know that I am frequently there helping people identify snakes (whether they like it or not), for example:

    Here are my top five tips for determining whether the snake you found is a Cottonmouth or a Copperhead. I’m assuming that you already know it is one of these species (here is some help getting you to that point).

1. Cottonmouths have white mouths.

            Cottonmouths don’t want to bite you unless they really they have to. That’s why they’ve come up with some impressive defensive displays. The point of these defensive displays is to scare off predators before a bite is necessary. Fortunately, one of the most common displays offers a great opportunity for differentiating Cottonmouths from Copperheads. When threatened, Cottonmouths will often open up their mouths widely and show off their namesake-white mouth (they're called Cottonmouths for a reason, after all). Copperheads can open their mouths too, but they do so less often and their mouths are more pinkish. Cottonmouths don’t always open their mouths either, so we can’t always use this feature to tell them apart.

2. The color and patterning of a Cottonmouth’s body is different than that of Copperheads.

            A recent commenter on this blog described adults Copperheads as being the color of chocolate milk with a chocolate kiss pattern. I think that’s a great analogy. Most Copperheads are indeed this color with a brown hourglass-banding pattern. It is important to note though, some Copperheads may appear a little more brown or a little more orange, depending on the individual and where it is found.

            Adult Cottonmouths, on the other hand, often appear almost black or dark brown, much different than adult Copperheads. However, some Cottonmouths are not so dark that you can’t make out a pattern. Cottonmouth patterns are superficially similar to that of Copperheads, but the hourglass bands of a Cottonmouth are not as precise as those of Copperheads: they are messy, the lines are blurred, and sometimes there are other shapes thrown in there as well. In general, Cottonmouths become darker over time, obscuring their patterns. And, this brings up an important point.

            Baby Cottonmouths are as strikingly and vividly patterned as Copperheads, they do not become dark and lose their pattern until later in life. Just because the patterns on a baby Agkistrodon are clear does not mean it is a Copperhead. This is where it's important to see if the hourglasses are messy or not. Again, Copperhead bands are relatively crisp, Cottonmouth bands are not. That said, in some regions Copperhead markings can get kind of messy, check out Kentucky animals, for example.

            Despite what you might hear elsewhere, both Cottonmouths and Copperheads have a bright yellow or green tail tip when they are babies (they use it to lure in prey) so the presence of this bright tail tip cannot be used to differentiate between the species.

Cottonmouth (top)
 Copperhead (bottom)
3. Cottonmouths have a dark band on their face that runs through their eye.

            Copperheads do not (see comparison on right).

4. In many parts of the country, you can find Cottonmouths or Copperheads, but not both.

            In many parts of the Southeast and Midwest of the United States, both Cottonmouths and Copperheads can be found, in general. However, there are lots of places where only one occurs. For example, Cottonmouths can be found throughout all of Florida, but Copperheads are only in a bit of the panhandle. On the other hand, Copperheads are crawling around much of the northeastern United States, but if you are traveling up the East Coast you’ll see your last Cottonmouths in Virginia. I suggest you take a look at the range maps for Cottonmouths and Copperheads so you can determine whether you can rule out one or both of these species when trying to identify a snake around your home.

5. Copperheads and Cottonmouths are usually found in different habitats.

            Cottonmouths mostly use wet and/or swampy areas while Copperheads prefer more upland and forested habitats. This isn’t a hard and fast rule though, so it should be used together with the other tips provided here. Cottonmouths may migrate out of their swamps when they dry up, and I’ve seen Cottonmouths suddenly appear in new wetlands formed by recent rains (they showed up to feast on breeding amphibians and would have had to travel across long stretches of pine forest to get there). I’ve never seen a Copperhead in the water though; my guess is that it’s a relatively rare occurrence.

Okay, let's put your knowledge to the test. 
Try identifying each of these five snakes
(without reading the comments first!). 
Make sure to number your answers 1-5.

     Do you have some tips for telling Cottonmouths from Copperheads (or have you heard some tips that don't work)? Share them below.    

     All of the photographs that appear in this blog post appear courtesy of Aubrey Heupel and Matt Greene of Fingerprince Prints Photography.

Related Posts:

Catching Cottonmouths in Tuskegee National Forest
View the Entire Cottonmouth Myth Series

Want to Learn More? Check Out These Scientific Articles:

X. Glaudus, K.M. Andrews, J.D. Willson, & J.W. Gibbons (2007). Migration patterns in a population of cottonmouths (Agkistrodon piscivorus) inhabiting an isolated wetland Journal of Zoology, 121, 119-124 DOI: 10.1111/j.1469-7998.2006.00232.x

E.A. Eskew, J.D. Willson, & C.T. Winne (2009). Ambush site selection and ontogenetic shifts in foraging strategy in a semi‐aquatic pit viper, the Eastern cottonmouth Journal of Zoology, 277, 179-186 DOI: 10.1111/j.1469-7998.2008.00527.x

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