Wednesday, August 23, 2017

Northern Watersnake

A Northern Watersnake basks in an Arlington, Virginia pond.

     The Northern Watersnake (Nerodia sipedon sipedon) may well be the most misidentified snake in the East. Due to its living in close proximity to water, large size, variable coloration, ability to flatten its heads to appear triangular, and what some consider a feisty nature, many people confuse it for the venomous Water Moccasin (Cottonmouth) snake. This despite cottonmouths actually not living in the DC area, being limited to Southern Virginia at most. 

A Northern Watersnake eating an American Eel it has dragged out of the water. Not the dark bands thickest along the top of the body.

     Northern Watersnakes are thick-bodied snakes, up to 55 inches in length (though most are 2-3 feet on average). They can have a wide range of color, and the tannins and mud in the water may also stain them. Most however have dark bands across their back that are wider than the light colored bands along their bodies. The dark bands narrow along their sides and thicken along the top of their backs. These bands tend to turn into blotches by the time they reach their tails. The bands also fade as they grow older, becoming difficult to see on the oldest and largest specimens. These snakes also have crescent-shaped marks along their bellies, but that is obviously not an easy thing to see.

Note the crescent-shaped marks along the belly of this watersnake. The tail is almost completely dark underneath.

     Watersnakes (all one word is the scientifically accepted way of spelling the name) are quite common, being found in every county in Virginia and almost all the DC area. They are almost always found in close proximity to water. They can swim completely submerged, which differs from many other types of snakes.

Juvenile Northern Watersnakes are more boldly patterned than adults. Note that the dark bands are wider than the light colored ones and that they are widest at the top of the back. This youngster is swimming submerged underwater. 

     Northern (also called Common) Watersnakes are diurnal, being most active during the day. They feed primarily on fish and amphibians, which are swallowed alive. They will however sometimes pull their prey out of the water and eat it after it has died, particularly if it is putting up a good struggle. They're also one of the few snakes who will eat carrion. Here is a video taken during our Arlington Bioblitz of a watersnake that has wrestled an eel out of the water to eat: 

     Because fish and amphibians are so slippery, watersnakes have very long and pointy teeth, pointing backwards to help hold on to prey. They also have a mild anticoagulant in their saliva. Since they will bite defensively, this can make a bite look scary, though the watersnake really can't do any real harm. The vast majority of the time they try and flee. If captured or cornered, they will flatten out to look bigger, hiss, strike, musk, and even discharge feces, so it's best if they're left alone. Some people report being attacked by them, but what has often happened is that the snake is trying to get to a burrow that the person is in front of, or trying to get aboard what they think is an island when it's someone canoe. They really just want to get somewhere and a person happens to be in the way. This unfortunately adds to the misconception that they're dangerous or aggressive however. 
     Female watersnakes are larger than males, sometimes twice the size. If you see a large one, it is almost certainly a female. This size difference allows them to be able to produce more young. From 6-70 (though 20 is more typical) young are born alive from eggs retained within the mother's body, often from August through October. The largest females produce the most young. Males are attracted to females, finding them by searching for pheromone trails. This sometimes result in "mating balls" of one large female surrounded by 2 or more suitors. If nothing happens to them (lots of things such as herons, raccoons, large fish, snapping turtles, foxes, and mink will eat them, specially when young), they can live up to 9 years and 7 months.
     Though these snakes can appear dangerous, they really just want to be left alone. They're fascinating creatures who are important predators in our waterways, when not serving as prey themselves to other wildlife. Here's one last look at one as it swims away, trying to avoid any confrontation: