Snakes of Wisconsin

By Mike Reiter, Polk County Naturalist

Garter Snake
Garter Snake

     Wisconsin has a total of 22 snake species with some quite common like the Common Garter Snake and others listed as threatened like the Butler’s Garter Snake or endangered like the Northern Ribbon Snake. Only two of the twenty-two are poisonous and both are rattlesnakes and quite rare. All the snakes are beneficial and help control nuisance insects and rodents. Many people fear snakes but their overall presence is by far, beneficial to humans.

     Snakes are reptiles and belong to the same class as lizards and turtles. They also have a backbone and are vertebrates as are mammals and birds. Unlike birds and mammals, however, they are cold blooded and they body temperature is that of their surroundings. They cannot internally regulate their body temperature but rely on warming or cooling themselves getting heat form the ground, air, or direct sunlight. On a cool day they can be seen at times on a blacktop path or driveway “catching” rays that make them more active.

     In the winter snakes hibernate below the frost line for up to half the year. Some species like garter snakes, seek companionship and large numbers can group together in crevice or underground chamber called a hibernaculum. 

     A snakes tongue is forked, and flicks in and out as it tests the surroundings for taste, smell and even sound. It is a fantastic sensory organ and not a “stinger”! Snakes will mate in the spring and some lay eggs while others give birth to live young from eggs which are carried and incubated inside the mom. As a snake grows it will shed its skin as another new skin will form below the old one. Depending on species and amount of food intake, this can occur several times a summer.

     The two poisonous snakes in Wisconsin are the larger timber rattler which can reach up to 4.5 feet long and the smaller massasauga or swamp rattler which is restricted to low, swampy areas. Both species are quite rare. The massasauga rattlesnake overwinters in crawfish holes and keeps his body temperature above freezing in the water as it keeps its head above the water level. What is a real dilemma to this rare reptile is that the area dams drop the water levels in the lowland areas in the winter to prepare for spring floods. This leaves the hibernating snakes high and dry and they will then freeze to death. Rattlesnakes had a bounty on them at one time but that was removed in 1975. Just like all living things, snakes also have a very viable place in the natural order of things.

     While some folks think snakes make good pets, wild snakes should be left in the wild to do the thing they do best, which is control unwanted pests such as insects and rodents. All snakes are carnivores, eating animals exclusively. They also, at times, will be eaten by other animals, adding to their place in the food pyramid.

     Besides the two rattlers listed earlier (Timber and Massasauga) other Wisconsin reptiles include Northern Water Snake, Queen Snake, Eastern Garter Snake, Eastern Plains Garter Snake, Northern Ribbon Snake, Western Ribbon Snake, Butler’s Garter Snake, Chicago Garter Snake, Northern Ringneck Snake, Prairie Ringneck Snake, Blue Racer, Smooth Green Snake, Brown or Dekay’s Snake, Northern Red-bellied Snake, Western Fox Snake, Black Rat Snake, Eastern Hognose Snake, Bullsnake, Eastern Milk Snake and finally, Western Worm Snake.

     Most snake species are declining at a rapid pace. 18% are considered endangered, 5% threatened, 32 are of special concern and 45% having experienced moderate declines. We need to keep a close eye on our reptilian partners to insure their survival into the future.