Snakes in the Bay

Perhaps you’ve heard the scary stories. Long, sinuous serpents slithering through Chesapeake Bay, threatening paddlers, water skiers, and swimmers, triggering breathless reports of venomous water moccasins or copperheads on the hunt.

Many snakes harbor venom. Most aren’t perilous to humans. Maryland and Virginia are home to three dangerous snakes, only one of which is aquatic. The timber rattlesnake, whose bite can be fatal, is confined to forested upland areas. The widely dispersed copperhead occurs throughout the Chesapeake Bay watershed. It’s highly venomous and accounts for more snake bites in the U.S. than any other species. Like many snakes it can swim, but it’s unlikely to venture into the Bay’s open waters. 

The third dangerous snake, the truly aquatic water moccasin, is a pit viper that can also deliver a nasty bite. Big and beefy, it can reach lengths of five feet. It shows up in tidal Virginia, mostly in the state’s southeastern corner, but is not found north of the Newport News area. 

Another category of dangerous aquatic snakes bears mentioning – sea snakes. Living in tropical waters, they comprise over 50 marine species of the cobra family. Sea snakes are not innately aggressive but will bite when confronted, releasing a powerful venom, 10 times more lethal than a land cobra’s and 100 times more than a rattlesnake’s. Thousands of people fall victim every year; about three percent die. Fortunately, we don’t have to worry about them in Chesapeake Bay. Sea snakes don’t exist in the Atlantic Ocean.

So, ruling out copperheads, cottonmouths, and sea snakes, what watery reptile could be menacing Chesapeake Bay mariners? Most likely, it’s the Northern Water Snake, Nerodia sipedon sipedon. Residing in fresh and brackish water environments, they’re common around the Bay, in open waters, salt marshes, tidal creeks, fresh water tributaries, small ponds, and ditches. With their blotchy, banded, highly variable markings they may be mistaken for copperheads or cottonmouths, but their color patterns are distinctly different (OK, a frightened observer isn’t likely to be consulting a field guide). Northern Water Snakes are as large and thick as cottonmouths, but they swim differently – just under the surface, with their heads protruding above, while cottonmouths float on top of the water. 

Northern Water Snakes aren’t regarded as dangerous, but that doesn’t mean you shouldn’t be cautious. They can be aggressive when threatened by an approaching boat, swimmer, or water skier. They may bite, repeatedly, flattening and widening their head and torso like a cobra, emitting a rank, musky odor, and delivering a weak venom. Physicians don’t consider the bite “medically significant” but it’s not much fun for the victim and a bite wound can get infected. So respect these snakes and give them the wide berth they deserve.

Beyond their potentially aggressive behavior, Northern Water Snakes are fascinating creatures and important components of Chesapeake Bay. They range throughout the eastern U.S., seldom venturing far from water. They eat fish, frogs and toads, salamanders, worms and leeches, crawfish, large insects, and even turtles, birds, and mice. They gulp down their prey alive. Their predators, which they try to ward off with musk secretions, include raccoons, opossums, foxes, skunks, snapping turtles, wading birds, and other snakes. 

Like all serpents, Northern Water Snakes are air-breathers. That’s why they keep their heads above water when swimming. Still, they can stay underwater for over an hour without rising for air. They’re solitary animals in warm months but in the spring and fall will bask in the sun together, intertwining their bodies. They hibernate in winter and mate in the spring, males at age two and females a year later. Eggs incubate inside the mother, who gives birth to as many as eight dozen live offspring in mid-late summer. The young snakes are independent when born but are highly vulnerable to predators.

Northern Water Snakes may not be your favorite Bay creatures but they’re a vital part of the estuary’s ecosystem and food web. As with so many Chesapeake denizens, humans are their biggest threat. Principal dangers come from development-related habitat loss, climate change, and indiscriminate killing by people with aversions to snakes. We should swallow our squeamishness and show these Bay neighbors some love. Or, at least, let them go about their business in peace.

Henry “Hank” Parker is a scientist and writer who previously lived in Annapolis and now resides in Vermont.