Northern water snakes utilize many different aquatic habitats, such as: rivers, streams, sloughs, lakes, ponds, bogs, marshes, and impoundments. They prefer open areas that provide many spots for them to bask in the sun and relatively still waters. These are dark-colored snakes, brownish, tan or grayish in appearance. The back and sides have a series of square blotches alternating with each other that may merge to form bands.Northern water snakes are only social during the fall and spring after overwintering. They can be found in groups at basking sites coiled together. For the most part they are solitary animals, especially in the warmer monthsNorthern water snakes can be found during the day or at night, but are more active during the daylight hours. Because of their preference for aquatic habitats they are commonly mistaken for venomous water moccasins, Agkistrodon piscivorous. Northern water snakes are not venomous but they are aggressive and should always be treated with care and respect.Northern water snakes are carnivores and scavengers. They eat a variety of prey items, including amphibians amphibians (adults and tadpoles), fis fish (alive or dead), crayfishcrayfish, large insectsinsects, leeches, other snakes, turtles, birds,rtbir and small mammalsmammals such as white-footed micewhite-footed micwhe. They have been known to herd schools of fish or tadpoles to the edge of bodies of water where they can prey upon many at one time.
Source: Nerodia sipedon Northern Water Snake, Animal Diversity Web, University of Michigan Museum of Zoology