Yellow-Bellied Watersnake Vs Cottonmouth

Written by Brandi Allred
Published: March 14, 2022
Image Credit /Shutterstock.com
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Think You Know Snakes?

In the southeastern United States, there are two species of snake that are commonly mistaken for one another. These are the cottonmouth, also known as the water moccasin, and the yellow-bellied watersnake, also known as the plain-belly watersnake. Each species has distinct characteristics marking it apart from the other, yet they’re often confused with one another and, unfortunately, killed by snake-fearing humans. No matter which species you’re looking at, both are important parts of their native ecosystems, and should not be killed unless absolutely necessary. 

The yellow-bellied watersnake (Nerodia erythrogaster) occupies many of the same habitats as the water moccasin (Agkistrodon piscivorus), yet the two behave in very different ways. They also hunt different creatures, and only one of them has a mouth complete with two long, hollow fangs capable of delivering dangerous venom.

Here, we’ll learn all about the differences and similarities between cottonmouths and yellowbelly watersnakes, starting with their looks. Then, we’ll compare their habitats, behaviors, and unique diets. Finally, we’ll take a look at which species is more dangerous, and what you should do if bitten by either type of snake.

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The Key Difference Between a Yellow-Bellied Watersnake and Cottonmouth

Yellow Bellied Watersnake vs Cottonmouth
Cottonmouths are venomous while yellow-bellied watersnakes are not.

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The key difference between cottonmouths and yellow-bellied snakes is that cottonmouths are venomous. In addition, the two have very different appearances. Yellow-bellied snakes are true to their name, and lack the distinctive banding of cottonmouths. Yellow-bellied snakes are also more likely to flee if a human startles them. Let’s dive into their main differences one by one.

Yellow-Bellied Watersnake Vs Cottonmouth: Appearance

Beginning with their looks, both the yellow-bellied watersnake and cottonmouth have medium to large, heavy bodies. Water moccasins grow a little bigger, up to five feet on average, while yellowbellies generally top out around four feet. Both species have thick bodies, but cottonmouths have bigger heads. Further, cottonmouths are pit vipers, with heat-sensing pits located just behind their nostrils. Yellowbellies, on the other hand, cannot sense heat, and lack pits.

Plain-Bellied Water Snake - Yellow Belly Water Snake
Yellow-bellied watersnakes have dark bodies with pale bellies

/Shutterstock.com

Still looking at the head, one of the biggest differences between the two species is the shape of the pupil; cottonmouths have an elliptical pupil, while yellow-bellied watersnakes have round pupils. But perhaps the most obvious difference between the two lies in the adult coloring. As their name suggests, yellowbellies have yellow to white undersides with solid gray to black bodies. Water moccasins, on the other hand, range from yellow-brown to brown-black, and have distinct darker bands encircling their bodies. 

For both species, young snakes have lighter coloring and more obvious markings. This is especially apparent in yellow-bellied watersnakes. Juvenile yellowbellies are pale gray-orange with dark brown splotches.

Yellow-Bellied Watersnake Vs Cottonmouth: Habitat

Regionally, water moccasins and yellow-bellied watersnakes can be found in all the same places. They’re common throughout Florida and the southeastern United States as far north as Virginia and as far west as eastern Texas. Both species prefer lowlands, and neither occurs too far from freshwater.

Being semi-aquatic snakes, both cottonmouths and yellowbellies live, and hunt, near sources of water like ponds, streams, marshes, lakes, and wetlands. Yellow-bellied watersnakes shy away from fast-moving water, and are more likely to be found near sources of slow-moving or even stagnant water. Both species bask in the sun near the water’s edge or drape their bodies over branches overhanging the water.

Yellow-Bellied Watersnake Vs Cottonmouth: Behavior

Both cottonmouths and yellowbellies are ovoviviparous species. This means that, rather than laying eggs, females actually incubate the eggs inside their bodies until they hatch. Then, they give birth to live young. Cottonmouths have between 1-20 young per birth, while yellow-bellied watersnakes can have up to 55 snakelings at once. The larger the female yellowbelly, the more young she produces.

Side view of a Cottonmouth snake, ready to strike. The snake has a large spade-shaped head.
Cottonmouths have elliptical eyes and patterned markings on their bodies

KF2017/Shutterstock.com

When threatened, yellow-bellied watersnakes are more likely to flee than are cottonmouths. Cottonmouths will actually coil up and stand their ground by displaying the white insides of their mouths. Yellowbellies, if cornered, will not hesitate to bite, and even produce foul-smelling musk which they rub on attackers.

Yellow-Bellied Watersnake Vs Cottonmouth: Diet

Of the two species, cottonmouths have the more varied diet. They’re a big snake, and they have potent venom, which means they can eat anything they can fit into their mouths. This includes fish, turtles, birds, rodents, amphibians, and even baby alligators. Yellow-bellied watersnakes hunt almost entirely in the water or along the water’s edge; they eat crayfish, fish, salamanders, frogs, and toads. Both species have been observed waiting in ambush as well as actively seeking out prey.

Yellow-Bellied Watersnake Vs Cottonmouth: Venom

While both snakes appear fearsome, only one has venom glands. Cottonmouths are members of the pit viper family, and along with their heat-sensing capabilities, they also have hollow, venom-delivering fangs. Like rattlesnakes and copperheads, water moccasins have hemotoxic venom designed to incapacitate and kill small animals. The venom is also necrotizing, meaning that, from the moment of injection, it starts working to digest the surrounding tissue.

Plain-bellied Watersnake - Yellow-bellied Watersnake
Yellow-bellied watersnakes are far less dangerous than cottonmouths.

/Shutterstock.com

Yellow-bellies, however, have no venom. They’re considered harmless by snake standards, though you don’t want to pet them. Yellow-bellied watersnakes react violently when threatened, and may bite a person multiple times if needed.

Yellow-Bellied Watersnake Vs Cottonmouth: Which is More Dangerous?

Out of the two species, only one poses a risk to human life, and that’s the cottonmouth. Cottonmouth venom can cause serious complications, and even death, if left untreated. In the case of a bite, you should immediately move away from the snake to avoid further injury. Do not try to ice the bite, or suck out the venom. Additionally, don’t make any kind of cuts into the skin near the punctures. Instead, get to a hospital as quickly as you can. 

Water moccasin bites are very rarely fatal, but risks of complications go up exponentially if the bite is left untreated. At the hospital, medical professionals will monitor the injury for signs of envenomation; not all bites actually deliver venom. Often, when venom is injected, the area around the bite swells, and the tissue may even blacken and slough off. It’s because of their venom that cottonmouths are unquestionably more dangerous than yellow-bellied watersnakes.

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