Snakes

Click here for “Wildlife Damage Management Fact Sheet Series–Snakes” from Cornell University 

Species names: 

There are 22 species that are call Wisconsin home. Four of these species are often found near homes; the Common Garter snake,  Milk snake, Gray Rat snake, and Northern Water snake. Of the 22 species that are found in Wisconsin only 2 are venomous, the Eastern Massasauga Rattlesnake and the Timber Rattlesnake. Listed below are the 22 species  

For more information and color photographs, see Cornell’s wildlife damage management fact sheet about snakes. 

Nonvenomous snakes, usually docile: 

Eastern Garter snake, Thamnophis sirtalis. Common near homes. 

Also known as the Common Garter snake 

Bulter’s Garter snake, Thamnophis butleri. Special Concern 

Plains Garter snake, Thamnophis radix. Special Concern 

Milk snake, Lampropeltis tiiangulum. Common near homes. 

Dekay’s Brown snake, Storeria dekayi 

Smooth Green snake, Opheodrys vernalis. State Endangered 

Red-bellied snake, Storeia occipitomaculata 

Northern Ring-neck snake, Diadophis punctatus edwardsii 

Common Water snake, Nerodia spedon 

Also known as the Northern Water snake 

Eastern Fox snake, Pantherophis vulpnius 

Bull snake, Pituophis catenifer. Special Concern 

Also known as the Gopher snake 

Western Ribbon Snake, Thamnophis proximus. Species of Concern 

Queen snake, Regina septemvittata. Endangered 

North American Blue Racer, Coluber constrictor. Special Concern 

Gray Rat snake, Pantherophis spiloides. Special Concern 

Eastern Hognose snake, Heterdon platyrhinos.  

Red-bellied Mud snake, Farancia abacura. Species of Concern 

Prairie Ring-necked snake, Diadophis punctatus arnyi 

Lined snake, Tropidoclonion lineatum. Special Concern 

Eastern Ribbon snake, Thamnophis sauritus. Endangered 

Western Worm snake, Carphophis vermis. Special Concern 

Venomous, defensive (found only in certain parts of the state): 

Timber Rattlesnake, Crotalus horridus. Special Concern 

Eastern Massasauga Rattlesnake, Sistrurus c. catenatus. Federally threatened and State Endangered 

How to tell a nonvenomous snake from a venomous one in Wisconsin: 

Nonvenomous snake: Venomous snake: 
Pupil: round Pupil: like a cat’s eye, vertical 
No pit between the eye and nostril Pit between the eye and nostril 
(the 3 venomous snakes in NY are all pit vipers) 
Shape of head variable, often slender Broad, triangular-shaped head 
Scales underneath the tail, toward the tip, 
are divided 
Scales underneath the tail, toward the tip, 
are undivided 

Size: 

Gray Rat snake: Up to 4 1/2 feet long. 

Garter snake: 2–4 1/2 feet, usually smaller. 

Milk snake: Up to 4 1/2 feet long. Sometimes confused for the copperhead. 

Water snake: Up to 4 1/2 feet long. 

Signs of their presence: 

Water snakes often sun themselves on boat docks. 

Milk snakes and Gray Rat snakes are frequently found in barns. 

On cool days, you may find snakes (especially the black rat snake) resting on top of the heating ducts in buildings heated with forced hot air. 

Sounds: Silent, except for the rattlesnake, which rattles, and the milk snake, which may also vibrate its tail if annoyed. 

Scat: Elongated, whitish. The scat of a Gray Rat snake may be large. 

Large shed skin (over 2 foot long): Probably from a Gray Rat snake. 

Evidence of their feeding: Hard to identify, because they swallow their prey whole. 

Garden and crop damage: None, because they are strictly carnivores. 

Building damage: None, because they use only existing holes and entryways, and don’t create others. 

Diet: 

Carnivores.  

Gray Rat snakes eat mostly small rodents and birds.  

Garter snakes eat mostly earthworms, but also slugs, amphibians, fish, crayfish, insects, small birds, other snakes, and carrion.  

Milk snakes eat rodents and other snakes.  

Water snakes eat mostly fish, also amphibians, insects, and crayfish.  

Other snakes add spiders, bird eggs, and rabbits to the menu. 

Typical activity patterns: 

Social style: Solitary, but may hibernate with other snakes, even those of different species. 

Daily activity: Mostly diurnal. Milk snakes are usually nocturnal. 

Hibernator? Yes. Snakes will often hibernate (usually from October/November to March/April) in a large group that may include snakes of different species. 

Migrates? No, but they do move to hibernating site. 

Where found: 

These 22 species of snakes have different habitats throughout Wisconsin. The 4 species that will be focused upon live in the following areas.  

Habitat: 
Gray Rat snake— rough forested terrain with outcroppings and fields near woods. They can often get into barns or other areas that are home to rodents. 
Garter snake—wide variety of moist areas, woodlands, pond edges, grassy areas, forest edges, marshes, or hedgerows. 
Milk snake—found in a variety of habitats including grassy areas, farmland, forests, rocky hillsides, and river bottoms.  
Common Water snake—rivers, brooks, wet meadows, ponds, and swamps, preferably still or slow-moving water, in areas with overhanging branches and rocks (for cover and basking). Common near dams and bridges. Often times they can be found sunning on boat docks.  
Eastern rat, garter, and milk snakes will follow their prey into barns and houses, usually in basements but sometimes attics. That’s especially true for the Eastern Rat snake, because it’s an excellent climber. Most snakes prefer sunny areas where rock or wood piles and other debris provide cool, shaded hiding places. They move from sunny to shady areas to regulate their body temperatures. 

Territory and home range:  

Not generally territorial, but snakes are faithful to den sites (“hibernacula”) in their home range. They’ll reuse these sites from year to year and are sometimes found in large numbers. This makes them vulnerable to habitat destruction and persecution. 

Breeding habits: 

Pair bonding style: Polygamous. 

Mating dates: Gray Rat: May–June. Garter: first few warm days after emerging from hibernation, usually mid-March–May, then mates again in the fall before entering hibernation. Milk snake: June. Water snake mates in April–May and again in the early fall. 

Egg-layers: Gray Rat and milk snakes lay eggs in loose soil, decaying wood, or sawdust or manure piles. Black rat snakes lay their eggs from May through early July. Milk snakes lay theirs in mid-June–July. 

Live young: Garter and Northern Water snakes. 

Birthing/eggs hatch dates: Garter snakes give birth July-early September. Northern Water snakes give birth in August-early October. The eggs of the black rat snake hatch between July and September, those of the Milk snake from late August-October. 

Clutch size: Black rat snake: average 14 (6–24). Garter: av. 14–40 (3–85). Milk snake: av. 13 (6–24). Northern water snake: av. 20–40 (10–76). 

Weaning dates: Young are able to fend for themselves at birth or upon hatching. 

Common nuisance situations: 

Time of year: Spring through fall. 

Snakes don’t damage buildings or eat crops. They only enter buildings through existing holes, cracks or “doors” (such as an open window). Some people are afraid of snakes. Others welcome them, because some snakes eat mice and rats and help to control those pest populations. Remember, however, that if a snake can get into a home, so can other creatures. 

What are they doing? 

These snakes sometimes hibernate in buildings, especially the basements of old houses with stone foundations. They usually enter houses through torn screens, open basement windows, cracks in the foundation, or through gaps next to pipe and cable entrances. 

They follow prey (mice, insects) into cellars, crawl spaces, attics, barns, sheds, garages. They may also be found in wood piles and debris, in heavily mulched gardens, and under shrubs, tarps or planks. They seek cool, damp, dark places. 

Their presence may frighten or annoy people. Several species, including the garter snake, may emit a foul and musky smell when handled. 

Disease risks: salmonellosis (food poisoning). 

Injury risks: nonvenomous snakes have tiny teeth. They leave a faint, U-shaped bite mark. Their bites rarely hurt much or cause problems, with the exception of the Common Water snake, which is known for its nasty bite. Few people encounter Wisconsin’s venomous snakes, and fewer still are bitten—and even then, the bites are rarely fatal. A bite from one of Wisconsin’s venomous snakes (Copperhead, Cottonmouth, Massasauga Rattlesnake, or Timber Rattlesnake) will swell, hurt, and turn black and blue. Children and the elderly are at greatest risk for a severe reaction. If bitten, remain calm and get medical help. Do not use a commercial snake bite kit; they tend to do more harm than good. 

De-bunking myths about snakes: 

If bitten by a venomous snake, do NOT try to suck out the poison. Do not slice the wound. Get medical help. 

Snakes don’t dig. They can’t make holes. 

The milk snake and northern water snake (both non-venomous) are often confused for the copperhead or the water moccasin (both venomous). 

Legal status in Wisconsin: 

Protected. Under Federal and State protections. A permit is required to kill certain species. 

Best practices 

Deter Certain Food Sources:  

Take away attractants for mice and other rodents 

Keep grains, pet food, and bird seed in secure containers 

Set mouse traps and insect traps within the building Exclude insects and mice from your buildings. 

Reduce the amount of mulch in your garden and around trees and shrubs  

Remove Areas of Shelter: 

Mow closely around the building. 

Weed whack in areas the mower cannot get to 

Remove brush and rock piles near the building 

Stack wood away from the building 

Don’t plant right next to the foundation, thus taking away cover for snakes and many pests. 

Prevent Them from Entering Building: 

Seal all openings that are larger than 1/4″ with mortar, expanding foam, cooper mesh (Stuf-Fit®), 1/4″ hardware cloth, or sheet metal. 

Fences may keep them out. Use 1/4″ hardware cloth. The fence should be 3 ft. high, buried 1 ft. deep, with the bottom edge bent outward into a “L”-shaped shelf that sticks out at a 90° angle to prevent the snakes from slipping under the fence.  

Fences are more likely to work well around a small area. Otherwise, high maintenance needs may make this impractical, because some snakes would be able to travel through chipmunk tunnels that pass under a fence. 

Although snakes cannot create holes, they will use holes that were made by rodents and other animals. To prevent the problem from happening again, you may need to identify the maker of the holes and exclude them, too. 

Trapping strategies: 

Direct capture methods and live traps for non-venomous snakes

Pick them up, wearing heavy leather gloves for protection. Support the snake’s entire body to keep it calm. Hold snakes behind the head, to keep them from biting you. 

With care, snakes can also be captured with a “snake stick,” which is a catchpole modified for snakes. A forked stick can also be used (carefully!) to pin down a snake. 

Do not press too hard as you can cause internal damage 

They can be scooped into a garbage can using a scoop or shovel. 

To live trap water snakes, add a brick-sized piece of Styrofoam to a minnow trap (so the trap will float, allowing the snake to surface for air). Bait with about a half-dozen minnows. Attach a rope to the trap for easy retrieval, then float it in near the shoreline. 

If the snakes can’t be found, you can lure them to a spot where they can be easily captured. Place piles of damp towels or burlap sacks on the floor, near the walls. Cover the pile with a dry burlap bag to keep it moist. In a few days, return to the pile during the middle of the day, when the snakes are most likely to be there. Scoop up the pile with a large shovel, put it into a large garbage can, and carry it outside. 

Several variations on the above technique: Use a board or a piece of plywood instead of the pile of towels or burlap sacks. Place some decomposing grass clippings on top of the board, which should be 1″ off the ground. Dead mice or mouse droppings placed underneath the board will help to attract snakes. Check every few days. This technique works well with garter snakes and black rat snakes, but is not as effective with water snakes. 

Create a reptile tube trap, based on a technique suggested by HSUS animal capture consultant, Dave Pauli. Inside this trap, the temperature should be just right for the snake—more appealing than the surrounding area. The trap is a piece of thin-walled PVC tubing that’s 2–3 ft. long. Drill a few 1/8″ air holes along the length of the tube. Cap one end. In cold weather, place a disposable hand warmer, battery-operated electric sock, or heating pad in the far end of the tube, along with some soft cotton rags. If you have fresh rodent droppings, you may want to toss a few in there, too. (In hot weather, substitute an ice pack or cold, wet rag for the heat source.) Then drill a 1″ hole into a cap and use it to cover the other end of the tube. Although the snakes can leave the trap, they usually stay inside because it’s more comfortable for them. You can install a one- way valve by affixing a 1 1/2″ stiff plastic circle over the inside of the cap. The snake can push its way in, but can’t leave easily. (This trap also works with other reptiles, such as lizards.) 

Glue boards designed for mice will also catch smaller snakes. You may be able to release the snake unharmed by pouring a little bit of cooking oil onto it. However, some biologists believe the oil harms the snakes. 

Venomous snakes: 

Only experienced snake-handlers should capture venomous snakes. They’re often handled using a catchpole and then transferred into a sturdy container. 

Using a one-way door to exclude snakes from a building: 

Technique developed by wildlife consultant William Bridgeland. Roll aluminum insect screening into a tube, then attach it over the entry hole, which is usually found in the foundation. Angle the tube up slightly, and flatten its outer end a bit. Leave the tube in place for at least two weeks while snakes are active (summer). Don’t substitute another material for the insect screening. Snakes may use scent to find their entry holes. Insect screening scatters odors, which would make it harder for the snakes to locate the entry hole, but other materials might retain their scent and direct the snakes back to the opening. If they find the opening, they may be able to get back inside. 

Preferred killing methods: 

First, discuss the situation with your customer. Is it really necessary to kill the snake? Try all methods of removal and exclusion.  

If no method delivers positive results 

Shooting, using bird shot (target the head) 

Stunning and decapitation 

Control Methods that don’t work particularly well, or aren’t legal in Wisconsin: 

Spray “Ortho Snake B Gon” on your lawn every 30 days  

Set up predator decoys, specially birds of prey, in areas snakes frequent 

For information on pesticides follow the link, https://datcp.wi.gov/Pages/Programs_Services/PesticidesProducts.aspx