The Most Snake-Infested Swamps in America

Submerged beneath stagnant waters, or slithering amidst fescue-strewn shorelines, snakes take to swamps like bees to honey. With millions of acres of cumulative wetlands, the United States has no shortage of such biodiverse water bodies—especially in its southern reaches. The following six are some of the most snake-infested stateside swamps. Let's tour their murky domains and meet the standout serpents residing in each.

Big Cypress Swamp: Florida

When pondering the swamps of southern Florida, one may initially picture the vast, vital, and notorious Everglades. However, much of the Everglades is technically a flooded out prairie system. It is the adjacent Big Cypress Swamp that piques our selective intrigue. Established on October 11th, 1974 (making it the nation's first national preserve), Big Cypress National Preserve comprises 729,000 acres of freshwater swamps, cypress forests, and some water-logged prairies of its own that sprawl toward the Gulf of America (Mexico) from the western flank of Everglades National Park. The ecosystem benefits from similar, federally-designated protections as its neighbor, but allows for more public and private operations (i.e. hunting and resource extraction).

Even though the National Park Service compartmentalizes the Sunshine State's southern reaches, its resident snakes know no such boundaries. This means that the infamous invasive python problem that plagues the Everglades also encroaches on Big Cypress Swamp. The Burmese python (Python molurus bivittatus) found its way into the wilderness of southern Florida (and beyond) because of a combination of accidental and intentional releases of captive individuals. Because the swamps and Everglades mimic the beneficial aspects of its Southeast Asian environment but lack any of the corresponding challenges, these 6-10-foot (but as large as 18-20) constrictor snakes quickly became the area's apex predator. It is estimated that there are hundreds of thousands of pythons lurking in these waters - putting pressure not only on the other top predators, such as the American alligator and Florida panther (who have to compete for the same food sources), but also the 26 smaller snake species that are native to Big Cypress.

Congaree National Park: South Carolina

South Carolina's Congaree National Park is where snake-swarmed swamps meet neck-cranking forest canopies. Here, just a half-hour drive from Columbia, America's largest (intact) old-growth bottomland hardwood forest rises triumphantly above the floodplain of both the Congaree and Wateree Rivers. In fact, this portion of the Palmetto State is home to the tallest known tree from 15 different species! Such accolades have garnered Congaree not only its national park status, but the coveted Wilderness designation ( the highest protective measures afforded by the federal government) for 21,700 acres of its 27,700-acre total purview. Further still, in 1983, UNESCO christened the Congaree Biosphere Reserve.

The swampy, nutrient-rich foundation that is responsible for so many champion trees also supports a wide variety of wildlife, such as the slithering reptiles in question. Congaree National Park is home to 21 species of snakes, including three venomous varieties. In terms of the latter, listen for the warning buzz of the timber rattlesnake (Crotalus horridus), look for the dark, hour-glass blotches of the copperhead (Agkistrodon contortrix), and of course, given the watery domain, be mindful of the semi-aquatic, fish-eating cottonmouth (Agkistrodon piscivorus), aka "water moccasin." If you choose to explore Congaree by canoe or kayak, you might spot this hefty-bodied viper swimming on top of the swamp.

With all of that said, please don't avoid this overlooked sanctuary (one of the least-visited national parks in the country, actually) because of snake concerns. Congaree National Park maintains a 2.6-mile boardwalk loop, which allows visitors to explore without any fuss, muck, or safety concerns.

Great Dismal Swamp: Virginia/North Carolina

The Great Dismal Swamp is shared between southeastern Virginia and northeastern North Carolina. Its namesake National Wildlife Refuge transcends state lines to protect nearly 113,000 acres, an admirable purview if not for the fact that this valuable Coastal Plain habitat used to exceed one million acres. Nonetheless, according to the U.S. Fish & Wildlife Service, the Great Dismal Swamp "...contains some of the most important wildlife habitat in the mid-Atlantic region." Its robust species list consists of 47 or so mammals, 200 birds (native and migratory), 96 distinct butterflies, 56 types of turtles, lizards, salamanders, frogs, and toads, and such arboreal residents as the (now-familiar) bald cypress and globally rare Atlantic white cedar.

Like Congaree National Park, Great Dismal Swamp NWR is home to 21 species of snakes, and, like Congaree, the same three venomous species once again make an appearance: the timber (aka canebrake) rattlesnake, copperhead, and cottonmouth. As one might suspect in a sizeable swamp, a healthy array of watersnakes are also present, including the common watersnake (Nerodia sipedon), brown watersnake (Nerodia taxispilota), and plain-bellied watersnake (Nerodia erythrogaster)—all excellent swimmers, all heavy-bodied, all feasters of fish, and all ultimately harmless when left to their own devices.

Atchafalaya River Basin: Louisiana

More on million-acre swamps, Louisiana's Atchafalaya River Basin (and peripheral watershed) is America's largest surviving river swamp and the largest floodplain swamp on the continent. Holding a 15-mile-wide path over the course of 140 miles from the small town of Simmesport down to the Gulf of America (Mexico), this exceptional basin, with the help of the Atchafalaya National Wildlife Refuge, Atchafalaya National Heritage Area, and multiple wildlife management areas, preserves a wealth of flora and fauna. Amidst the swamps, bottomland hardwoods (the most extensive such contiguous forest in North America), oxbow lakes, bayous, exist upwards of 400 species of birds (thanks to Atchafalaya being part of the Mississippi Flyway), 100+ species of fish, mammals ranging from black bears to beavers, and 65 species of amphibians and reptiles.

In terms of the latter, boaters, hunters, anglers, bird-watchers, and paddlers would do well to watch out for the American alligator (Louisiana's official state reptile), but also cottonmouth and copperhead snakes, all of whom are pretty common in this part of "Cajun Country." Less common but still noteworthy venomous snakes are the timber rattlesnake (which we've met in multiple other swamps thus far) and the pygmy rattlesnake (Sistrurus miliarius). This short but relatively thick pit-viper likes to hang around the basin's western edge. Non-venomous but (visually) striking snakes in the region include the speckled kingsnake (Lampropeltis holbrooki), the black ratsnake (Pantherophis obsoletus), the North American racer (Coluber constrictor), and the ring-necked snake (Diadophis punctatus).

Caddo Lake: Texas/Louisiana

Caddo Lake has a lot going for it. It is one of Texas' few natural lakes (though it is shared with Louisiana), it is the largest natural freshwater lake in the southern U.S. (i.e. 25,400-acres, but even more depending on dam-regulated water levels), it boasts the largest cypress forest in the world, its watershed hosts the greatest variety of native aquatic wildlife in Texas, it is one of 27 American wetlands protected by the international Ramsar treaty, and as per the 2024 sci-fi movie by the same name, its fringes harbor mysterious time portals (just kidding). Accolades aside, this extension of the Big Cypress Bayou leaves a unique visual impression, thanks to the knees (i.e., root systems that peak above the water) and beards (i.e., Spanish moss tendrils) of its plentiful bald cypress trees.

Seeing as Texas possesses the most snake species/subspecies of any state (i.e., at least 105), it is no surprise that a diverse array of serpents have found their way to the shallow, swampy waters of Caddo Lake. In addition to the usual cast of cottonmouths, copperheads, and rattlesnakes, a number of nonvenomous swimmers and burrowers reside here. The diamondback watersnake (Nerodia rhombifer) (not to be confused with the diamondback rattlesnake), the Mississippi green watersnake (Nerodia cyclopion), and the plain-bellied and banded watersnakes (whom we've met previously) rule the aquatic domain. Conversely, the smooth earthsnake (Virginia valeriae) and rough earthsnake (Virginia striatula) are small, plain, and secretive cousins who prefer to remain under logs, rocks, and leaves until darkness. Finally, one of the most curious-looking creatures in Caddo Lake has to be the eastern hognose snake (Heterodon platirhinos), thanks to its broad head and upturned snout.

Four Hole Swamp: South Carolina

Whereas the preceding swamps are readily accessible to the public (thanks to national/state parks and the like), South Carolina's Four Hole Swamp lacks the same large-scale recreation areas. There aren't even any developed access points to the region. While this may weed out the casual crowd, adventurous paddlers and anglers are made all the merrier to have an untouched sanctuary. Four Hole Swamp represents a blackwater tributary to the Edisto River. Here, various channels lead through stands of virgin bald cypress and tupelo gum trees - some in excess of 1,200 years old! The Francis Beidler Forest (an Audubon Society project) protects these ancient trees and offers guided canoe tours to visitors with advanced reservations. Despite the lack of large-scale developments, the Audubon Center does maintain a Congaree-esque boardwalk, as well as a small tower at Goodson Lake, for anyone looking to get a dry overview of the swamp (or, again, rise above the serpents).

Speaking of which, at least 20 species of snakes have been documented in and around Four Hole Swamp. The most common is the non-venomous brown watersnake (Nerodia taxispilota), which is often confused with the venomous cottonmouth (also present in this swamp). The key distinguishing trait is, unfortunately, not shown until the snakes are aggravated. Upon rearing its fangs, the latter exposes white flesh inside its mouth (hence the name, cottonmouth). Another harmless, identity-bending serpent found in this isolated swamp is the greenish ratsnake - a cross between the black ratsnake (Pantherophis obsoletus) and yellow ratsnake (Patherophis alleghaniensis). If you attend one of the Audubon Society's Second Saturday events, you may even get to meet Lucy, the tame greenish ratsnake.

Parting Thoughts

The United States possesses millions of acres of wetlands. These historically undervalued ecosystems provide natural flood relief, water filtration for major rivers, homes for vulnerable vegetation, and, of course, entire food chains' worth of mammals, birds, fish, and reptiles. Humans may not be inherently equipped to traverse these boggy terrains, but limbless serpents move masterfully through the muck, placid waters, and detritus. So if you're set on seeing some snakes this season, seek out one of these six snake-infested swamps.