(Photographed at Snake Road, April, 2023)

Diamond-backed Watersnake

Scientific Name: Nerodia rhombifer

Average Length: 30–48 inches (76–122 cm)

Maximum Length: About 69 inches (175 cm)

Status at Snake Road: Rare

Venomous? No

Description

The Diamond-backed Watersnake is one of the four watersnakes (nerodia) frequently encountered snakes at Snake Road. Its name comes from the dark, diamond-shaped pattern that runs along its back, though this pattern often becomes less distinct as the snake ages. Adults can appear nearly solid olive, brown, or black from a distance.

The body is thick and muscular with strongly keeled scales that give the snake a rough, matte appearance. The belly is typically yellowish with dark half-moon or checkerboard markings. Like all watersnakes, it has round pupils and a relatively narrow head, although adults often flatten their heads when threatened, making them appear more triangular than they actually are.

Behavior

Diamond-backed Watersnakes spend much of their time in or near water. Excellent swimmers, they are frequently seen basking on logs, branches, rocks, or along the edge of the road before quickly retreating into the water when approached.

Although they have a reputation for being defensive if captured, wild individuals almost always prefer to flee. If cornered or handled, they may flatten their bodies, strike repeatedly, and release a strong-smelling musk.

They feed primarily on fish and amphibians, using their speed in the water to capture prey.

Habitat

At Snake Road, Diamond-backed Watersnakes are most often associated with the wetlands, ditches, flooded woods, and cypress sloughs on the west side of the road. During migration, they frequently cross the road while moving between aquatic habitats and upland wintering sites in the limestone bluffs.

Where You're Most Likely to See One

Diamond-backed Watersnakes can be found almost anywhere along Snake Road, but they are especially common near standing water, flooded ditches, and the swampy western edge of the road. They are active throughout both the spring and fall migrations and are among the species visitors are most likely to encounter.

Commonly Confused With

Plain-bellied Watersnake (Nerodia erythrogaster)

Perhaps the easiest watersnake to confuse with a Diamond-backed Watersnake. Both are heavy-bodied and often occur in the same wetlands. Plain-bellied Watersnakes, however, have a much more uniform appearance with little to no dorsal pattern as adults. As their name suggests, the belly is usually plain yellow, orange, or cream-colored without the dark checkerboard or half-moon markings typical of Diamond-backed Watersnakes.

Mississippi Green Watersnake (Nerodia cyclopion)

Mississippi Green Watersnakes are another large, aquatic species found along Snake Road. Adults are often olive-green or brown with faint or nearly invisible markings, making them resemble older Diamond-backed Watersnakes. Mississippi Greens typically have a more uniformly colored back, a narrower head, and distinctive dark vertical bars on the lips. Their eyes also tend to sit noticeably higher on the head—an adaptation for spending much of their time in the water.

Common Watersnake (Nerodia sipedon)

Juvenile and subadult Diamond-backed Watersnakes are sometimes mistaken for Common Watersnakes because both have bold dark blotches and keeled scales. Common Watersnakes generally have alternating crossbands that transition into blotches toward the tail, while Diamond-backed Watersnakes usually display a more chain-like or diamond-shaped pattern running down the back. At Snake Road, Diamond-backed Watersnakes also tend to be noticeably heavier-bodied as adults.

When in doubt, give any snake plenty of space and admire it from a distance.

Fun Fact

Diamond-backed Watersnakes are among the largest watersnakes in North America and are capable of catching surprisingly large fish. Despite their intimidating appearance, they are completely nonvenomous and play an important role in maintaining healthy wetland ecosystems by helping control fish and amphibian populations.

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