School Integrated Pest Management (IPM) for Rats and Mice

Publication Number 444-512, Posted June 2003

Important Note

Introduction

Biology and Identification

Rats

1. Norway rats will generally build their nests in subterranean or ground level locations. Roof rats, in keeping with their name, prefer to nest in elevated areas, including trees and rain gutters.
2. Rats require water on a daily basis.
3. Rats can travel several hundred feet from the nest to forage for food and water.
4. Rats feed on a wide variety of food sources including trash, fruits, vegetables, meats, insects, grains, pet food, tree bark, and plant material.
5. Some rats can pass through openings as small as 3/4 inch in diameter.
6. Rats can jump vertically at least 24 inches and horizontally at least four feet.
7. Rats can dive and swim underwater for as long as 30 seconds. Therefore, they can crawl up to and swim through the water trap of toilets and drains.
8. Rats chew on everything, including wood, metal, glass, plastic, and stone, in order to help keep their large front teeth sharp and shortened.
9. Rats are very wary of new items in their environment.

Mice

1. Mice can get all of their moisture from their food if a ready water source is not available.
2. Mice search their entire home range daily to check for any changes to their environment.
3. The home range of a mouse is usually no more than 33 feet from its nest.
4. Mice may nest within appliances, in wall and floor voids, in false ceilings, behind counters, and within other similarly protected areas. If they are living outdoors, they prefer to nest in thickly vegetated or covered areas, such as in woodpiles, rock piles, or leaf litter.
5. Mice can jump upward at least 12 inches from the ground.
6. Mice can fit through openings as small as 1/4 inch in diameter.
7. Mice chew on everything, including wood, metal, glass, plastic, and stone, in order to help keep their large front teeth sharp and shortened.
8. Mice are good swimmers but seldom dive below surfaces.
9. Mice are very curious and will explore new items in their environment.

In general, rats and mice share many similar characteristics. Understanding these features is a very important aspect of rodent control. The following list gives some of these basic attributes:

1. Rats and mice usually search for food at night. If you happen to see a rodent during the day, it might mean there is a lack of food or the rodent population is high.
2. Mice and rats can run up almost any vertical surface including cinder blocks, wood, sheet metal, metal pipes, and cables.
3. Rodents prefer to travel along edges, using their whiskers as guides. Examples of edges include along the wall/floor junction, beside the foundation of a structure, or along pipes, utility wires, or rafters. Rodents are very wary of open spaces and will seldom cross uncovered areas.
4. Rats and mice have poor vision but powerful senses of smell, touch, hearing, and taste.
5. Rats and mice have very short generation times and can, therefore, populate a structure in a short period of time.

Prevention

• Store food (including pet food and grains) in glass, metal, or thick plastic containers with tight fitting lids.
• Promptly and thoroughly clean up any spilled food materials.
• Designate certain places within the school as areas for eating. Help students, teachers, and administrators understand the importance of only eating in these areas.
• Garbage is often the main source of food for rats and mice. Keep all trash receptacles tightly covered and empty them often. Plastic trash bags will not keep rodents out so remove trash daily.
• Remove any ready water sources. Fix leaking pipes, faucets, or irrigation systems. Also, if possible, remove standing water found in ditches, depressions, or other similar situations.
• Remove fallen fruits and nuts from any outside trees.
• Trim trees, bushes, grass, vines, or any other plants at least 12 to 18 inches away from the structure.
• Seal any holes and cracks within the siding of the building that can be used by rats or mice to gain access into the structure. In a rodent management program, the best materials to use when sealing large holes and cracks include 1/4-inch hardware cloth, 19-gauge or thicker sheet metal, plaster, or mortar. Smaller holes can be sealed using caulk or copper wool. Remember to look for holes in the building at every height, not only in the first three feet above the ground. Rats and mice will also enter a structure via the eaves, the roof, the attic vents, and where pipes and wires penetrate the walls and roof.
• Weather strip around doors and windows and if possible, use raised metal doorsills.
• Seal air conditioning units well. These units provide warmth, a nesting site, and a ready source of water.
• Repair broken sewer pipes. Rats will dig into and use broken sewer pipes as an entryway into a structure.
• Cap drains with perforated caps that are firmly attached to the floor.
• Clean up storage areas and other cluttered spaces, thus reducing nesting sites and protected places where rodents feel comfortable moving around.
• Remove woodpiles, rock piles, and any other outdoor heaps of materials that may provide nesting sites for rats or mice.

Monitoring and Inspection

1. Remember that you are trying to find five main things: nesting areas, food sources, water sources, access points, and signs of rodent activity.
2. Search piles of trash, clutter, or debris for rodent nests.
3. Inspect for feces and urine. Use Figure 2 to identify the source of a fecal pellet.
4. Inspect for rub marks or other indications of activity. Since rodents pass over the same spot within their territory over and over again, they leave behind rub marks where body oils and dirt collect.
5. Look for holes and cracks through which rodents can pass both inside and outside.
6. If you feel rodents may infest an area, lightly dust the edges of the area with chalk dust or talcum powder. After a period of time, return and look for footprints and drag lines (made by tails) that indicate rodent traffic.
7. Inspect at night when rodents are most active. Use a powerful flashlight and watch for movement. Listen for gnawing sounds, squeaking, and rodent movement.
8. Temporarily close suspected holes and entryways with dirt, paper, or aluminum foil. After a few days, return to see if the material was removed or chewed through.

Least Toxic Control Methods

As a side note, several companies manufacture and advertise repellant sound devices for rodents. The Federal Trade Commission ruled these devices are ineffective at controlling rats and mice.

Below are some of the most effective and least toxic methods available for rodent control.

Physical Removal

Snap traps make use of a trigger-induced killing mechanism. Upon being triggered by the presence of a rodent feeding on bait, the mechanism instantly snaps shut onto the mouse or rat, killing the individual. There are different sizes of traps, larger ones for rats and smaller ones for mice. This type of trap is the most effective type of trap for use in dusty locations.

Live capture traps are available, but leave the unpleasant job of killing the rodents to you. These traps may or may not utilize bait to attract the rodents.

Glue boards are also an option. These are helpful in that they not only trap rodents but also can retain rodent hairs and fecal pellets of escaped rodents, allowing you to monitor the presence of rodents. Glue boards do not kill mice or rats so inspect them often in order to prevent unnecessary suffering of trapped individuals. Glue boards should be fastened to a base with nails or wire in order to prevent partially trapped individuals from dragging the traps away.

The following points will help your trapping program be more effective:

• Always place traps flush against edges since rodents follow edges as they move from place to place.
• Place traps near active holes and cracks and near clutter and other protected areas where rodents may frequent.
• Place traps near fecal pellets and rodent urine.
• Place traps near gnaw marks, rub marks, or other signs of rodent activity.
• Secure all traps so partially caught individuals cannot drag the trap to an unknown location.
• You may wish to bait your trap with food or nest material. Examples of effective food baits include hot dog, peanut butter, bacon, nuts, or sugary substances such as gumdrops or raisins. Cotton may be used as an effective nest material bait.
• As for the number of traps to use, there is not a definite number. Usually the more traps you can safely set, the better. Place traps wherever you find activity and try placing traps every three to four feet along a wall. Concentrate traps in one area at a time. After the area has been cleared of rodents, move on to the next area.
• One of the most important things to remember about traps is when first placed they are foreign objects to the rodents. Rats and mice will treat foreign objects differently. Rats are wary of unfamiliar objects while mice are more curious. Therefore, depending on the rodent species, trapping may be instantly effective or may require patience.
• Whenever removing live or dead rodents, wear gloves to protect yourself from harmful microorganisms.

Chemical Management

There are several important negative aspects to using rodent poisons. Rodenticides have been overused in some areas. Because of this overuse, some mouse and rat populations have developed resistance to the toxicants. In addition, the use of rodenticide can be dangerous. Rodents can pick up the toxic baits and move them to other areas of the school. Baits can end up in cafeteria food, in student lockers, and in wide-open areas where curious students may pick them up and handle them. Therefore, rodenticides should only be used to handle emergency situations where rodents are out of control and other management techniques are insufficient.

Baits should not be used indoors. Intoxicated rodents that are disoriented may inadvertently wander into public areas. Imagine a school administrator having to deal with a dying rodent that has emerged into a school cafeteria. Additionally, rodents that have been baited indoors often die in hidden, difficult-to-reach areas. The result is a dead, decaying, malodorous body that cannot be removed. The dead body also attracts new pests like flies and other insects.

The following suggestions will make the use of toxic baits more effective and safe:

• Only use rodenticides outdoors.
• Place all rodenticides in locked, tamper resistant bait stations and secure all bait stations so they are immovable.
• Since rodents often move and hide their food, some forms of baits may be safer to use. Water baits and secured blocks of paraffin bait cannot be removed and stored by rodents.
• Use baits over long holidays when students are absent from the building.
• For rats, bait stations should be placed about 15 to 30 feet apart. For mice, they should be placed about six to eight feet apart.
• Place baits along the edges of walls, near rodent entryways, and in areas where known rodent traffic exists.
• Remember to have patience since rats must become accustomed to changes in their environment. It may take a few days until the rats feel comfortable trying the baits.
• Frequently monitor the amount of bait consumed. Replenish any missing bait until management goals have been reached.
• Remember to always wear gloves when handling any sick or dead rodents.

Record Keeping

Acknowlegments

BIRC, P O Box 7414, Berkley, CA 94707; http://www.birc.org

INTEGRATED PEST MANAGEMENT (IPM) TECHNIQUES
The Four-Step Plan

• Prevention
• Monitoring and Inspection
• Least Toxic
  Control Methods
• Record Keeping

	Norway Rat	Roof Rat	House Mouse
Scientific name	Rattus norvegicus	Rattus rattus	Mus musculus
Other common names	Brown, wharf, or sewer rat	Black, ship, or house rat
Adult weight	3 to 21 ounces	3 to 12 ounces	1/2 ounce
Snout	Blunt	Pointed	Pointed
Ears	Small and thick with short hairs	Large and thin without hair	Large, some hair
Tail coloration	Dark above, pale underneath	All dark	All dark
Fur	Brown with black; shaggy	Light brown, gray to black, smooth	Light brown to gray
Droppings	Capsule-shaped, pointed	Pointed and curved	Rod-shaped and pointed
Food requirement	1 ounce per day	1 ounce per day	1/10 ounce per day
Water source	Free water	Free water	Water from food; also need free water if dependant on a diet that is dry or high in protein
Climbing ability	Can climb	Active climber	Good climber
Nest locations	Mainly in burrows	Walls, attics, trees	Near/in stored material
Swimming ability	Excellent	Can swim	Can swim

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