Diamondback Water Snake: Habitat, Diet, and Identification Tips

Key Tips

• Diamondback water snakes are nonvenomous and native to the Mississippi River Basin and surrounding areas in North America and the eastern regions of Mexico.
• Often confused with cottonmouths, diamondback water snakes are nonvenomous.
• All water snakes give birth to babies, they do not lay eggs.
• Diamondback water snakes can even give birth without mating.

What is a Diamondback Water Snake 

Diamondback water snakes are one species out of the 10 or so in the Nerodia genus. They’re closely related to the semiaquatic garter snakes, but much thicker-bodied and extremely defensive. But even though they pack a mouthful of razor-sharp teeth, diamondback water snakes are nonvenomous. 

Native to the United States and the eastern coast of Mexico, diamondback water snakes are the biggest water snake species.

Habitat: Where to Find a Diamondback Water Snake

These fish and frog eaters are never far from water. Diamondback water snakes are nearly always in or near a permanent water source where they can find food — strongly preferring slow-moving water like lakes, rivers, and swamps. These snakes are most common along the Mississippi River Valley and surrounding areas, but their range spreads east and west from the river. They also live in Mexico, where they inhabit many lakes and rivers along eastern coasts as far south as Tabasco. 

These snakes spend much of their time in the water, and that’s where many people find them. However, diamondback water snakes are often found dangling over the water, waiting for a meal. Like all reptiles, they bask on anything warm and sunny, like rocks and tree stumps — slipping quickly into the water at the first sign of danger.

There is a small population of introduced diamondback water snakes in Lafayette Reservoir of Contra Costa County, California. Experts believe these are the result of released pets. 

Diet & Behavior: What Do Diamondback Water Snakes Eat 

That these snakes live in and around the water makes sense when you understand their favorite food is fish. But diamondback water snakes eat more than fish — they also eat various amphibians like frogs and salamanders.

When threatened, diamondback water snakes flatten their heads and hiss — which quickly escalates to repeated biting attempts. You do not want one of these snakes to bite you. They aren’t venomous, but it hurts! On top of that, their saliva contains an anticoagulant that will keep you bleeding for a few minutes.

This species hunts during the day and hangs from branches with just their heads underwater, waiting to ambush their prey. Diamondback water snakes also hunt actively through slow-moving water, in rocky, marshy areas. 

During the cooler months, diamondback water snakes find a cozy place to sleep until the weather warms in the spring.

Diamondback Water Snakes: Babies and Reproduction

Although you may see baby diamondback water snakes, you will never see an egg. 

This species does not lay eggs, instead after the female mates she holds the young inside while they develop, giving birth to them when they’re ready. Diamondback water snakes mate in the spring and give birth to babies (also called neonates) in late summer and early fall. 

Many snakes do this, including most vipers, pit vipers like rattlesnakes, and garter snakes. Scientists don’t know why some reptile species decided that laying eggs wasn’t the way to go. However, they do know that it gives those young a better survival chance. Egg-laying reptiles often lose eggs to predators and sometimes simple accidents, so this makes sense. 

There is even evidence that mothers support the developing snakes with nutrients — making carrying them internally even more valuable to the babies. Some snakes and this species is one, also have the ability to reproduce without mating — it’s called facultative parthenogenesis. 

How to Identify a Diamondback Water Snake 

These snakes have a weighty feel to them. Diamondback water snakes are stocky and usually around three to four feet long, although the record length was five feet, nine inches. Their heads are triangular with vertical bars along their lips and their eyes are located higher on their head — giving them a sort of “derpy” look. As far as eyes, they have round pupils. But, generally speaking, if you have to look at a snake’s eyes to tell whether it is venomous, you are too close and missing a few identification factors. 

Diamondback water snakes have keeled scales and a diamond pattern which gives them their name. Some people describe it as having a “chainlink fence” appearance. Although their pattern is gorgeous, it fades as they age, sometimes becoming nearly black — except for their bellies which are light-colored with crescent-shaped markings. 

The three subspecies are only marginally different visually, but here they are: 

• Nerodia rhombifer rhombifer: The nominate subspecies, these snakes are found in the U.S. These water snakes have strong crescent-shaped belly markings and paler dorsal markings.
• N. r. blanchardi and N. r. werleri: These subspecies are found only in Mexico. Their belly markings are paler and dorsal markings are stronger.

Identification Tips

Most water snakes get confused with venomous cottonmouths from time to time. It’s pretty common, especially if you are unfamiliar with snakes or, they just scare you. That’s okay! We are here to help with a few handy tips to help you figure out whether you saw a water snake or a cottonmouth.

Eyes, head shape, and facial markings. If you ever heard the wive’s tale that all venomous snakes have vertical, cat-eye-shaped pupils, this is where it came from. That story originated in people trying to differentiate between cottonmouths and water snakes! Of course, we know that not all venomous snakes have cat-eye pupils, just take a look at a coral snake — their pupils are round. 

A cottonmouth has cat-eye pupils, many have a dark stripe behind the eye, and all have an extra scale over each eye. Their heads are harshly angular, with large venom glands in the cheeks. These snakes look angry — like somebody swiped the last of their coffee. It’s because of that extra scale over their eye. Also, if you’re close enough to see their pupil shape, backing up is a good idea. 

Water snakes have dark bars or thin vertical lines along their lips. They also have round pupils and eyes set higher on the head. They look “derpy.” If you have ever seen a photo, you know what we mean!

Neck and body thickness. Cottonmouths have very thin necks and stout bodies that end in a very thin tail. 

Water snakes have thicker necks compared to cottonmouths. Their bodies are also thinner overall.

Behavior. Cottonmouths generally warn you by gaping their mouth at you. If a snake does this, back away slowly. Venomous snakes don’t usually want to bite. Venom is resource-intensive and takes time to rebuild, so not envenoming every threat is a smarter move for them.

Diamondback water snakes won’t warn you. They’ll first try escaping, if that doesn’t work, they just bite. Repeatedly. These snakes are also notorious for musking — defecating on you and secreting a noxious substance at the same time. 

Color and Pattern. This item is deliberately at the bottom of the list — it is for those moments where it’s hard to see the head.

Young cottonmouths have bright patterns with pixelated chocolate kiss-shaped markings over a lighter brownish color. Their tails are bright yellow or green and they are pretty easy to spot. Mature cottonmouths often lose the pattern and become very dark. You might see traces of their pattern along their lower edges, near their belly, but sometimes it’s invisible. Yet, you may still be able to spot their unusually thin tail.

The same holds true with young diamondback water snakes. Their juvenile pattern is very bright and obvious — chainlink markings are easily seen. As they mature, their bodies darken and hide the markings.

The photo featured at the top of this post is © Seth LaGrange/Shutterstock.com