Minnesota Wild Animal Management| Rodent Prevention

May 3, 2012

MN Rodent Prevention

Commercial and Farm Buildings

Store bulk foods in rodent-proof buildings, rooms, or containers whenever possible. Stack packaged food on pallets with adequate space left around and under stored articles to allow inspection for signs of rats. Drain holes in dumpsters should be fitted with a removable hardware-cloth screen, or else plugged after each cleaning.

Predators

Although cats, dogs, and other predators sometimes kill rats, they do not provide effective rodent control. They just can’t kill rats fast enough. Rats often live among cats and dogs. They use a pet’s food and water, and sometimes even their shelter.

Traps

Use traps only after you’ve taken all the sanitation steps outlined above. While rodent trapping is a very important tool in rodent control, it is no substitute for good sanitation. If you don’t control their sources of food and water, rodents will procreate faster than you can trap them. Trapping has the advantage that

  • It does not involve dangerous pesticides;
  • The user knows immediately when traps are successful;
  • Trapped rodents can be easily disposed of before becoming an odor hazard, as can happen with poisoning (i.e. rodents dying in inaccessible places around the house).

Traps are particularly effective if rodent populations are small. Snap traps, glue boards, and cage traps all work. Most traps can be used over and over. Wood-based snap traps are inexpensive, and available at most hardware stores. Most snap traps are designed for mice but larger traps designed specifically for rats are available. Purchase enough traps to make your effort short and decisive.

Traps need not be baited, just located where rodents will trip across the trigger in their normal course of travel. If you want to bait your traps use a very tiny amount of peanut butter, gumdrops, raw bacon, bologna, or vanilla extract (use a cotton swab to apply vanilla extract). Whatever you use, don’t pile it on. Do so, and you increase the chance for an insect infestation. You also increase the chance that a rodent will find a way to remove the bait without getting caught. You may also kill one rodent but feed several others. All you really want is the food smell. You can also bait with a piece of cotton ball, since rodents like to use it to build nests. Cotton has the advantage of not attracting insects.

  • Place the traps wherever you find signs of rodent activity, but preferably near walls. Traps work best when placed at right angles to a wall, with the trigger end touching the wall. This takes advantage of a rodent’s preference for travel along walls.
  • Remember also to keep your traps out of reach of pets and small children.
  • Several traps should be located in suspicious areas. Ideally, they should be moved to different locations each day, and certainly they should be moved if rodents are not being caught.
  • It may be necessary to adjust the trap trigger to insure easy release when touched by the rodent.
  • Since rats especially are shy of anything new, it may be necessary to leave a trap unset until the bait has been taken at least once, to reduce the chance for trap shyness.
  • Check your traps daily.

Another form of trap is the glue board, which has a sticky surface that holds any rodent that attempts to cross it. Locate glue boards anywhere you would other traps, but remember that glue boards are so sticky that they’ll be a problem for any children, livestock, pets or other wildlife that come in contact. Also keep in mind that dust will reduce the effectiveness of a glue board. Once caught on a glue board, a mouse will usually die from cardiac arrest. Glue boards will lose their effectiveness over time, so replace them when they are no longer sticky. As with any other trap, move your glue boards to another location if rodents are not being caught.

Electronic devices

Ultrasonic devices broadcast sound waves above the range of human hearing, but they have limited efficacy because the sound waves produced cannot penetrate solid objects, like walls. They also quickly lose intensity with distance. Because rodents quickly become accustomed to repetitive sounds, there is little evidence that sound devices will drive established rats or mice from buildings. Likewise, there is little evidence that magnetic devices or vibrators have any positive effect on rodents.

Rodenticides

Rodenticides are poisoned baits and fumigants used mainly by professionals for rodent control. Since fumigants are gases highly toxic to humans, livestock and other animals, they cannot be applied in buildings where occupants could be exposed. Rodenticides have a wide variety of active ingredients. They are registered pesticides available on the open market, but they require training and experience to apply safely and effectively. If not properly applied, these pesticides can kill or otherwise endanger children, pets, or other animals that may mistakenly eat or breathe them. We urge you not to use these materials yourself.

Hire a licensed Wild Animal Management Expert well versed in rodent control to apply them. Sometimes rodenticides work too well. It can kill a rodent before it makes it out of the house. In that case you’ll have dead rodents in inconvenient places like attics, wall cavities, crawl spaces, or behind cabinetry…stinking up your home and causing major insect and fly problems. Since rodenticides are pesticides, they also present serious storage and disposal problems.

Disposal of Rodents and Rodent Droppings

Try not to touch a dead or dying rodent, or their droppings. Fleas on the rodent will want to make you their new host. Use rubber gloves or tongs and dispose of rodents and rodent droppings by burial, incineration, or by wrapping them in a plastic bag before throwing them into a tightly covered garbage can. Injured or sick rodents should be killed (drowning is easiest) before being disposed of. Dry sweeping or vacuuming will cause dust and viruses to become airborne. Therefore,

  • sweep or vacuum rodent droppings only after you have wet the affected area with bleach water (1-2 cups of bleach for each gallon).
  • Use a spray bottle to apply the bleach water.
  • Also spray those traps that have caught rodents, and the areas where rodents have been active.

Wash your hands with soap and hot water after disposing of rodents and rodent droppings, even if you used gloves.

Measuring Success

Results cannot be measured simply by counting dead rats and mice. Abandoned burrows will be dusty and have cobwebs in the openings. When there are no fresh tracks or droppings, and live rats or mice are no longer observable, results are as good as can be expected.

Additional Resources: 

Additional information on preventing mice and rodent infestations, diseases from rodents, cleaning up after rodents, and images of rats and mice can be obtained from the Centers for Disease Control and Prevention (CDC) web site.

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