Venomous Snakes


Venomous snakes play an important role in the Big Thicket’s ecosystem by consuming rodents, insects, and other small animals, including other snakes!

Respect snakes by giving them plenty of room—at least 10 feet, to be safe—and they will usually leave you alone. Remember, snakes do not view humans as prey, but they will attack if they feel threatened, usually when you’re too close. If you are bitten by a venomous snake, seek medical attention immediately.

Read more about our non-venomous snakes. Our park species list page has a complete list of snakes and other species found in the Big Thicket.

cottonmouth snake showing its cotton-colored mouth
Cottonmouths get their name from their open-mouth warning display.

Photo: USFWS, Jesus Moreno

Cottonmouth (Water Moccasin)

Agkistrodon piscivorus

Cottonmouths, also called water moccasins, are found throughout the southeastern United States. They can range from about two to four feet in length, but females are typically smaller.

Cottonmouths belong to a group of snakes called pit vipers. Pit vipers get their name from the pits found between their eyes and nostrils, which act as heat sensors and help them hunt by detecting heat from other animals. They are frequently a dark solid color ranging from black to dark brown, but younger snakes can have blotches that range from dark brown to yellow as well. Cottonmouths can appear very similar to other dark, solidly colored snakes such as water snakes. They are most easily differentiated by their large triangular head. However, if you are close enough to a cottonmouth to clearly identify the triangular shape of its head you should back up and give it some space! These snakes are most frequently observed near water and are excellent swimmers.

Cottonmouth venom is very potent, and if you are bitten you should seek medical attention immediately. However, cottonmouths will usually try to warn people of their presence before they bite so cottonmouth bites are not very common. The name cottonmouth refers to the white coloration inside their mouths, which contrasts sharply with their dark bodies. When threatened, water moccasins open their mouths wide to ward off predators.

Female cottonmouths give birth to litters that average about 5-10 snakes, but can be much larger. Cottonmouths do not stay with their young after they are born, but young are self sufficient when they are born and are able to find their own food. Because they are such strong swimmers, water moccasins will eat more fish than most snakes. They also eat frogs and small mammals.

coiled timber rattlesnake among pine needles
Coiled timber rattlesnake

NPS Photo

Timber Rattlesnake

Crotalus horridus

Timber rattlesnakes are found throughout the Eastern United States, and are one of the most widespread venomous snakes in North America. They consume many types of small animals such as rodents, birds, lizards, and frogs.

Timber rattlesnakes can grow between 3 and 5 feet long as adults, though longer individuals have been recorded. They are pit vipers, which get their name from the pits found between their eyes and nostrils. These pits act as heat sensors and help them hunt by detecting heat from other animals. Timber rattlesnakes’ coloration can vary from yellowish brown to gray, but they have dark V or M shaped crossbars that run down the length of their body.

Like other rattlesnakes, they generally try to warn predators away by shaking their tail to make a rattling noise before biting someone. The low number of timber rattlesnake bites each year can be attributed to this rattling behavior and the fact that timber rattlesnakes are not aggressive. However, they are larger than most venomous snakes, have larger fangs, and a higher venom load. So when they do bite humans it can be serious, and if you are bitten you should seek medical attention.

Timber rattlesnakes do not produce litters every year, but instead have litters every 2-3 years. These litters can range in size from 5 to 20 snakes and are born live. Baby snakes will remain near the mother for about a week but the mother does not take care of them during this time.

a black/yellow/red coral snake in the leaves on the forest floor
Texas coral snakes prefer to eat other snakes.

NPS Photo / Andrew Bennett

Texas Coral Snake

Micrurus tener

Texas coral snakes are brightly colored and easily identifiable. They have alternating bands that run the length of their body that follow the pattern red, yellow, black, yellow. There are other species of snakes with similar coloration, but only coral snakes have coloration patterns where red and yellow bands touch. This is the reason for the popular rhyme “red on black, friend of jack, red on yellow, kills a fellow.” One reason there are other snakes with such similar coloration patterns is because the bright coloration of the coral snakes warns predators that it is very dangerous and they should stay away. By mimicking those bright colors, harmless snakes may scare away predators who don’t look too close!

Texas coral snakes are relatively shy and elusive, and as a result we do not know as much about their behavior as we do about other snakes in the area. However, we do know that they lay clutches of eggs instead of giving birth to live snakes. When young coral snakes hatch they are about seven inches long and are capable of producing the same toxic venom adults do. Coral snakes mostly consume other snakes, even other coral snakes! They will also eat small lizards. On rare occasions, they might eat small mammals.

Coral snake venom is very strong, and if you are bitten by a coral snake you need to seek medical attention. Unlike most venomous snakes in southeast Texas, a bite from a coral snake may not be very painful but this does not mean symptoms won’t appear later.

coiled copperhead snake with light brown coloration next to leaves
Copperhead snake

NPS Photo


Agkistrodon contortrix

Copperhead snakes get their name from their coloration. Both their heads and bodies are copper colored, though it can vary between a light brown color to a pinkish color. They are most easily identified by the darker hourglass shapes that can be seen running the length of their body as shown in the picture on the right.

Copperheads are venomous, and belong to a group of snakes called pit vipers. Pit vipers get their name from the pits found between their eyes and nostrils, which act as heat sensors and help them hunt by detecting heat from other animals. Copperheads can grow over 3 feet long, but are generally between 2 and 2 ½ feet long. If you encounter a copperhead while exploring the Big Thicket you should give them plenty of space as they can be territorial, and will bite if they feel threatened. If you are bitten by a copperhead you should seek medical attention, as people can have serious reactions to copperhead venom.

Copperheads are not social in the way that some animals such as wolves are, but they do occasionally interact with other copperheads. This happens most frequently during mating season, when males compete with each other for females’ attention. Copperheads give birth to live young in the fall. Litters usually are made up of about five snakes, but can be much larger! Copperheads mostly eat rodents and other small mammals but will also eat frogs and larger insects.

Copperheads brumate in winter, similar to hibernation. What's the difference? Hibernation is a dormant period that happens in animals that thermoregulate their own bodies, such as mammals. Animals that rely on their surroundings to regulate their body temperature, such as reptiles, undergo brumation.

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Brodie III, E. D., & Janzen, F. J. (1995). Experimental studies of coral snake mimicry: generalized avoidance of ringed snake patterns by free-ranging avian predators. Functional Ecology, 186-190.

Churilla, J. M. (2015). Behavioral and Physiological Evidence for Musk Gland Secretions as a Chemical Alarm Cue in the Cottonmouth, Agkistrodon Piscivorus.

Hill III, J. G., & Beaupre, S. J. (2008). Body size, growth, and reproduction in a population of Western Cottonmouths (Agkistrodon piscivorus leucostoma) in the Ozark Mountains of northwest Arkansas. Copeia, 2008(1), 105-114.

Lorch, J. M., Knowles, S., Lankton, J. S., Michell, K., Edwards, J. L., Kapfer, J. M., ... & Blehert, D. S. (2016). Snake fungal disease: an emerging threat to wild snakes. Philosophical Transactions of the Royal Society B: Biological Sciences, 371(1709), 20150457.

Martin, W. H. (2002). Life history constraints on the timber rattlesnake (Crotalus horridus) at its climatic limits. Biology of the Vipers, 285-306.

Mengak, M. T. (2009). Copperhead.

Rokyta, D. R., Wray, K. P., & Margres, M. J. (2013). The genesis of an exceptionally lethal venom in the timber rattlesnake (Crotalus horridus) revealed through comparative venom-gland transcriptomics. BMC genomics, 14(1), 1-21.

Smith, C. F., Schuett, G. W., Earley, R. L., & Schwenk, K. (2009). The spatial and reproductive ecology of the copperhead (Agkistrodon contortrix) at the northeastern extreme of its range. Herpetological Monographs, 23(1), 45-73.

Smith, C. F., Schuett, G. W., & Hoss, S. K. (2012). Reproduction in female copperhead snakes (Agkistrodon contortrix): plasma steroid profiles during gestation and post-birth periods. Zoological science, 29(4), 273-279.

Last updated: December 23, 2023

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