Minnesota Non-Venomous Snakes
Few animals are more disliked or misunderstood than snakes. Most are beneficial because of the rodents and insects they eat, and most species found in the U.S. are non-venomous. When snakes enter homes or are seen around buildings, they usually frighten people, who then want them removed immediately. Snake control can be a very time consuming problem which generally requires action by the property owner, but many people are unwilling or untrained to capture and remove snakes.
Several snake control methods can be used to discourage snakes from frequenting an area, prevent them from entering buildings, and to safely capture individual snakes that have strayed indoors. There may be extreme situations of heavy infestations, particularly of venomous species, that are best handled by qualified individuals, such as the professionals at Critter Control.
One reason that many people become frightened when they find a snake is because snakes are difficult to correctly identify (ID). There are many good reference books available to help recognize snakes, but all too often the snake is killed before it is identified. Of the 116 species of snakes found in the United States, only 19 are dangerous, including 15 rattlesnakes, two moccasins (copperhead and cottonmouth), and two coral snakes. Coral snakes are in the Family Elapidae. All the others belong to the viper family (Viperidae) and the "pit viper" subfamily (Crotalinae). There are three ways to tell pit vipers (rattlesnakes, copperheads, and cottonmouths) from all nonvenomous snakes in the United States. Pit vipers have the following:
- A deep pit between the eye and the nostril.
- The pupil (black part of the eye) is vertically elliptical; in bright light it may be almost a vertical line.
- The scales on the underside of the tail go all the way across. In some cases, the very tip of the tail may have two rows. All nonvenomous snakes native to the U .S. have two rows of scales on the underside of the tail from the vent (anus) to the tip.
Coral snakes have round pupils and their head is not dis- tinctly wider than their neck, nor V-shaped. In the U.S., coral snakes are ringed with red, yellow and black; the red and yellow rings always touch, and the tip of the head (snout) is black. The coral snake's markings can be easily confused with nonvenomous species, such as King Snakes, but the following ditty can help ID native coral snakes: "Red on yellow, kill a fellow; red on black, fiend of Jack."
Snakes are closely related to lizards. They live in a wide variety of habitats including forests, swamps, grasslands, deserts and both fresh and salt water. Some are active at night, others during the day. Snakes are predators and eat a wide variety of animals, including rodents, insects, birds' eggs, and young birds. King and Indigo Snakes eat other snakes. Some small snakes feed on earthworms, slugs, and salamanders. Water snakes eat frogs, fish, and tadpoles. Racers, Coluber spp., may advance forward until challenged, but most U.S. snakes do not move toward, charge, or attack people. They will usually crawl away to find cover and react only when cornered. Depending on the species and circumstances, a nonvenomous snake may react in one of several ways when threatened: it may lay on its back and play dead, hiss, open its mouth in a threatening manner, coil and strike, or bite (nonvenomous snakes have several rows of short recurved teeth).
Snakes are cold-blooded and must move to a suitable sur- rounding environment to regulate their body temperature. They can't survive extreme summer heat for more than 10 - 20 minutes and are rarely found in the open. They hibernate in the winter and may also be inactive periodically during hot summer weather. They spend most of their time resting in cool, damp, dark hidden areas. Snakes, like all reptiles, will sun themselves on warm spring days.
Snake activity is seasonal, and they are most active in the spring. They hibernate in many different places either singly or in large groups. Dens can be located by searching places where they are likely to sun themselves before hibernating in the fall, or when dispersing from den sites in the spring. Most snakes can breed when they are two to three years old. Females may produce dozens of young in a single brood. Snakes usually reproduce by laying eggs, but some hatch their eggs inside the female's body and the young are born alive. Young snakes can take care of themselves almost immediately. They do not breed inside houses, but have been known to lay eggs or bear live young in or under foundations. Minimizing shelter and food sources will make such an area much less attractive. When inspecting property with potential snake infestations, follow these precautions:
- Wear protective clothing (i.e., long, loose pants, outside high-top leather boots, heavy socks, leather gloves, long-sleeved shirt and/ or coveralls).
- Do not approach within striking range (usually about 1/3 of the snake's body length) while attempting to identify, kill, or capture snakes, until you are property trained and equipped.
- Do not put your hands or feet in places that you cannot see. Look before you move or sit.
- Non-venomous snakes have a round eye pupil and have no pit between the eye and the nostril.
- When in crawl spaces or similar enclosed areas that might be infested, maintain communication with another person.
- If you are bitten, move away to avoid multiple bites (even nonvenomous snake bites can hurt and may become infected).
Most snakes (especially venomous ones) are not considered threatened or endangered, but they are important in their local ecosystems, and should not be killed unnecessarily. Only 12 species found in the U.S. are on the Endangered Species List. Since some are dangerous, and nearly all are feared by most people, there is often little support for their protection, except in national parks and preserves. However, some federal, and many state and local laws may restrict the choices of "acceptable" control methods. Contact the appropriate Natural Resources or Fish and Wildlife Department for legal and preferred control procedures, and to obtain any special permits needed.
Habitat modification and physical exclusion (as with many other pests) are the most effective long-term methods for discouraging snakes from frequenting areas around buildings. The snakes may be feeding on rodents. The customer should be made aware that even a dramatic reduction in the rodent population in an area will not immediately reduce the number of snakes, since they can go without food for a long time (sometimes for months).
The following recommendations can be useful to property owners and managers for snake control:
- Keep grass and adjacent fields trimmed, drainage ditches and vacant lots mowed. Keep fence lines, parking lots, and railroad beds weed-free.
- Remove or store firewood, lumber, rock piles, pallets and old equipment 12-18 inches off the ground and away from buildings.
- Eliminate trash, garbage, brush and rock piles in the area and remove debris from under porches and crawl spaces. Remove driftwood, logs, and brush along ponds, and other waterways.
- Store boxes, containers and portable equipment 12-18 inches off the floor in sheds, carports, garages, basements, and crawl spaces.
The 'rodent-proofing' techniques listed below can also be used for snake control and snake removal strategies.
- Seal holes in foundation/walls around pipes, conduits or electrical lines with concrete, with 1/4 inch mesh galvanized screen (hardware cloth), or sheet metal.
- Screen all vents, louvers, windows, exhaust fans and chimneys.
- Install a steel-plate across the entire width of the bottom of the outside of every door to reduce the clearance to less than 1/4 inch. Seal cracks in foundation walls and around chimneys.
For play areas or locations with a heavy infestation of venomous snakes, a PMP could exclude them by installing a drift fence 18-36 inches high, using galvanized 1/4-inch mesh screen hardware cloth. Bury the bottom edge 4-6 inches in the ground. Put the fence posts on the inside of the fence and make sure the gate fits snugly. Sloping the fence outward (from vertical) at a 30-degree angle may be more effective but more difficult to install.
Live snake trapping is a snake control method that is used with V-shaped fences and at den entrances. Drift fences direct the snakes to a wire mesh funnel trap. Funnel traps of 1/4-inch mesh hardware-clothe can be 6 feet long, 2 feet wide, and 11 inches high, with an inward facing funnel entrance at one or both ends. The trap is constructed with a locking lid on top of the cage to remove the captured animals. Another type of funnel trap can be made by rolling a 3 by 4 foot piece of 1/4 inch mesh hardware cloth into a cylinder about one foot in diameter and 4 feet long.
Some snakes such as rattlesnakes, may congregate in large numbers in old rodent dens. Traps used at den entrances should be about 40 inches long, 32 inches wide and 16 inches high. The trap should have a 4-5 inch diameter opening 2 inches above the floor of the trap, with a long flexible sleeve to cover the end of a chute that is inserted into the main den entrance. The sleeve can be made of heavy cloth, plastic, bird netting, or other material with a drawstring or duct-tape closure. The 2-3 foot chute can be a 4 x 4 inch wooden open-ended box, or a piece of white PVC pipe. All other den openings must be sealed.
Capturing Snakes Indoors
Once a snake is in a building, it may be very difficult to find. While looking for the snake you should try to determine how it got into the house (through vents, holes, etc). Use a stick or pole to check clothing on the floor and blankets on the bed for the hidden snake, then remove clothing from the room. If the snake can’t be found try trapping it.
- Close door vents and put tape over the registers.
- Place a 4 by 4 foot cloth or folded sheet next to a wall and loosely tape the edges to the floor with masking tape.
- Place a large wadded-up damp towel on the center of the sheet next to the wall. Cover the damp towel with a dry bath towel.
- Close the door(s) to the room where the snake was last seen and seal the gap under the door with a folded towel.
- Return the following day and remove the blanket taped to the floor by lifting all four corners at once, starting with the two corners farthest from the wall. Place the bundle in a garbage bag.
- Dump the bag's contents outside in an open area. Using a stick or pole to separate, lift and shake out the individual towels, etc.
Rat-sized glue boards can be used to capture snakes. Attach several glue boards to a larger board or piece of cardboard and place this along a wall along which you have seen signs of its passing (alternating curved marks in the dust, snake droppings, etc.). Any snake which is caught on a glue board can be released by applying vegetable oil (while wearing heavy gloves, of course) to loosen the glue. There are one or two similar devices commercially available.
There are no toxicants or fumigants which are legal for snake control. There are commercially available snake repellents, but their effectiveness is variable and should always be used in conjunction with a more comprehensive Integrated Pest Management plan, such as the snake control and snake removal services available from Critter Control.
Reprinted from the National Pest Management Association (2000)