Northern Water Snake

Nerodia sipedon sipedon
Friday, June 24, 2011

Northern Water Snake

The Northern Water Snake is the only large water snake in most northeastern states. It has a large array of color morphs; however, the most common colorations are dark dorsal markings, which may appear to be alternating square blotches or merge into bands near the head. When N. sipedon are young, the markings tend to be very distinct. However, as they age, the markings become less vivid and the entire coloration darkens until the snake may appear to be a uniform brown or black. Northern water snakes’ bellies are typically white, yellowish, or orangish. Although at birth they sometimes measure only 19 cm (7 in), they can grow to be 140 cm long (over 4 ½ feet).

Northern water snakes can be found on the banks of virtually any body of water within their range. While they generally prefer still water such as ponds, lakes, and marshes, they can also be found along the edge of rivers and streams. Although their lifestyle is based upon their aquatic environment, they also spend time basking on the shore or sheltered under rocks or logs on land. During the fall and in the spring, water snakes tend to behave socially, basking in groups during the warmer part of the day. However, at other times of year they are mostly independent organisms, and typically bask, hunt, and overwinter by themselves.

Although male water snakes can begin to breed when they are just under two years old, female snakes are not able to bear litters until their third spring. After water snakes emerge from overwintering, they mate in April-June, depending upon the temperature and latitude. Female water snakes gestate for three to five months, and bear their litters in late summer or early fall. Females may bear litters of anywhere from 4 to 99 live young, which become independent at birth.

Both young and old water snakes can find myriad prey items in a typical body of water. They feed on tadpoles, frogs, fish, insects, crayfish, leeches, other snakes, and turtles. They also occasionally extend their diet to include birds and small mammals. Water snakes probably hunt mostly by their sense of sight and by detecting vibrations from their prey. They consume their prey by swallowing it whole when they catch it. One notable example of their hunting abilities was discovered last summer at MLBS, when a large water snake was found rendered immobile by attempting to swallow a still-struggling bullfrog much larger than its own head.

Water snakes, while nonvenomous, are aggressive and will not hesitate to bite if they feel threatened. However, their more common recourse to threat is to disappear under the water, where they can remain for up to 90 minutes without coming up for air.

Water snakes are present across most of the northeastern US, as far west as Nebraska and as far south as North Carolina. This specimen was captured under a snakeboard by the Field Methods class. It is a juvenile, and was in the process of shedding when it was captured. Last night, it finished shedding in captivity, leaving a full-length snake skin behind it.    

Article by Hazel Galloway