There may not be another animal on the planet that receives as much unfounded descriptions of aggression and viciousness as the cottonmouth (Agkistrodon piscivorus). It seems that almost everyone in the south has some type of cottonmouth story, whether a first-hand account or a story passed along by a family member or friend. The one consistent thing that these stories almost always have is a complete disregard for the realities of animal behavior. Terrified by their fearsome reputation, observers attribute almost any behavior a cottonmouth makes as “aggression” and a strong desire to bite anyone who comes near. However, a careful consideration of animal behavior, the published literature on cottonmouth interactions with humans, and my first-hand experience as a herpetologist all indicate that the aggressive cottonmouth is no more than a myth.
Cottonmouths (colloquially known as water moccasins) are pit vipers that can occasionally reach lengths of approximately 6 feet, although most individuals are much smaller. The species name piscivorus indicates their fondness for fish, but cottonmouths will also eat a wide variety of other prey items, including amphibians, birds, insects, and other snakes. They are primarily aquatic in nature but can easily move over land between water bodies and are often observed basking above the water. Locally abundant in many places throughout their range, cottonmouths generally prefer swamps, backwaters, and smaller creeks and streams. They are sometimes observed along larger rivers but observations from along the Altamaha in Georgia indicate that large rivers with expansive floodplains are not their preferred habitat (Stevenson and Chandler 2017). Cottonmouths come in a variety of colors and patterns but typically have dark bands along the dorsal surface (these fade in some individuals). Juvenile cottonmouths have a bright yellowish or greenish tail that they use to lure prey within striking distance. The best identifying feature for cottonmouths is the dark stripe that runs from the back of the eye to the corner of the jaw. Water snakes lack this distinctive feature.
Cottonmouths get their common name from their strikingly white mouth. When threatened, their characteristic defensive behavior is to hold their mouth open, displaying the white lining in hopes that it will scare away potential predators. This display can often be startling and some snakes make quick, jerky movements when performing it. However, this is a classic example of an animal indicating that you are in its space and that the preferred outcome is for you to move away without further interaction. In fact, a study of cottonmouths by Gibbons and Dorcas (2002) revealed that cottonmouths rarely bite in self-defense. None of cottonmouths tested offered to bite when researchers stood beside them and less than 20% tried to bite when physically stepped on. Furthermore, even when picked up by the researchers, only 36% of individuals attempted to bite. The most common behaviors displayed by cottonmouths during interactions with people are gaping, attempting to escape, and/or vibrating their tails (Gibbons and Dorcas 2002).
Despite these examples of relatively benign defensive behaviors, cottonmouths maintain a reputation of being ‘aggressive’ or ‘mean’. Many people will tell you of cottonmouths ‘chasing’ people that get to close, implying that the goal of this behavior is ultimately to bite people. These descriptions of cottonmouths as aggressive animals that frequently chase people demonstrate a fundamental misunderstanding of animal behavior and are perpetuated by purposeful exaggerations making snake encounters seem more exciting or dangerous than they really were. It’s not as good of a story if the snake just crawled away.
This does not mean that reports of cottonmouths moving towards people are completely fictitious. In fact, when given few options for escape, cottonmouths tend to move in the direction of the closest cover, regardless of whether or not there is a person in the way. Sometimes this movement is accompanied by a raised head in an additional attempt to convince intruders to get out of the way (Means 2010). However, these behaviors can scarcely be described as aggression or chasing, and cottonmouths exhibiting this behavior will crawl over boots, between legs, or around people with little to no interest in actually biting a person (plenty of videos now exist of this behavior). In reality, people are many times larger than even the biggest cottonmouth, and venom is energetically costly to produce. The best strategy for these animals is to escape a potentially deadly encounter with a potential predator.
The general perception of cottonmouths as aggressive is so widespread that it translates into two additional fallacies of basic snake biology. First, the average person is likely to describe any snake observed near the water as a cottonmouth, regardless of how similar in appearance it is. I recently identified an Eastern Hognose Snake in someone’s pool on facebook, but the majority of commenters were convinced it was a cottonmouth. This is not a rare phenomenon, and it can be difficult to convince people that many other species of snakes can be found in or near the water. Countless water snakes have met an unfortunate end for being identified as cottonmouths. Second, people will swear that cottonmouths occur well outside of their documented range. While interning for Georgia Department of Natural Resources in northern GA, I was approached by a local who adamantly believed he had cottonmouths in the creek behind his house. Never mind that we were many miles north of the closest recorded observation.
I have interacted with dozens of cottonmouths while working in the field in both Georgia and Florida. Many of these individuals were handled while collecting snake fungal disease samples. In almost every case, cottonmouths prove to be the easiest and calmest venomous snake in the southeast to work with. Many individuals will not even perform the classic cottonmouth defensive displays as described above. Instead they flee to the nearest hiding spot. I have never experienced anything in the field that remotely approaches the wild stories spread about cottonmouths on a daily basis. My most notable encounter is having multiple snakes surrounding me as they made their way into a spadefoot toad breeding party for a nice meal. Even in this case, the snakes had no interest in me, and one step to the side allowed the snake to carry on searching for food without me interrupting.
So what should you do if you encounter a cottonmouth (or any venomous snake really)? The first thing to do is to take a step backward and appreciate that you are likely invading its space (not the other way around). If a snake moves toward you, move to one side and let it go where it wants to go. By far, the most dangerous thing that you can do when encountering a cottonmouth is to interact with it by attempting to handle or kill it. The majority of venomous snake bites in the U.S. are illegitimate (i.e., they occur after someone has already seen the snake and is interacting with it in some way instead of moving away). Snake bites from unseen snakes are rare in this country. If you see a cottonmouth in the wild, be calm and realize that you are much larger than it, and it perceives you as a potential predator that has invaded its space. Cottonmouths are not out to get you, are not aggressive, will not chase you, and ultimately would like to be left alone.
Gibbons, J. W., and M. E. Dorcas. 2002. Defensive Behavior of Cottonmouths (Agkistrodon piscivorus) toward Humans. Copeia 2002:195–198.
Means, D. B. 2010. Blocked-flight aggressive behavior in snakes. IRCF Reptiles & Amphibians 17:76–78.
Stevenson, D. J., and H. C. Chandler. 2017. The herpetofauna of conservation lands along the Altamaha River, Georgia. Southeastern Naturalist 16:261–282.