Controlling Norway Rats
Rodent control is more than putting out bait or traps, and by following the five basic steps included here, greater success will be achieved at keeping homes and businesses free of rats:
Inspecting the Premises for Rodents
A good inspection of your premises and proper identification of the rodent involved is important to control these pests. Some of the common signs of a rat infestation include:
- Rodent sounds – Listen for gnawing, scratching or high-pitch squeaks, particularly at night when rats are most active.
- Gnaw marks - Rats love to gnaw; look for evidence of gnaw holes in bags or boxes of food and piles of sawdust where they've gnawed wood or shredded paper which is often used for nesting materials.
- Burrows - Check for holes anywhere a rat can find shelter: near bird feeders, earth banks, sewers, along walls, and under rubbish, concrete slabs, building foundations, dog houses, woodpiles, fence rows, or piles of debris.
- Droppings – Look for small, round feces. Rat droppings tend to be from 3/4 to one inch in length, whereas mouse droppings are smaller, averaging ½ inch. One rat produces 20 to 50 droppings a day.
- Other signs of rodents – Look for tracks evident in dusty areas, grease marks, and urine stains and odors which are often missed by the casual observer but are signs looked for by pest control professionals.
Identifying Rodents and Pests
Rats or mice? Rodents are opportunistic feeders - they eat what's available and tend to eat most of their food in one sitting. Here are some helpful physical characteristics to identify Norway rats, roof rats and the common house mouse:
- Norway Rat Weight - 7-18 ounces. Overall length is 12-16 inches long including the tail which is shorter than its body. Large, robust appearance.
- Fur - Coarse and shaggy, gray-brown to red-brown with lighter colored belly.
- Reproduction - Averages 6-12 young per litter; 3-6 litters per year. Reaches sexual maturity in 2-3 months.
- Nesting Habits - Will burrow 3-4 feet into the ground within 100-150 feet of their food and water supply in areas with harborage.
- Behavioral Characteristics: Being familiar with the many behaviors rodents exhibit will help determine a prevention program best suited to eliminate an infestation:
- Rats are very cautious and nocturnal, usually feeding right after dark and again before dawn, activity during the day indicates a heavy infestation.
- They have four front incisors that grow six inches a year; therefore, they must gnaw constantly and are capable of gnawing through wood, plaster, plastic, lead pipe, aluminum, cinder block, porous concrete, adobe brick, metal conduit, soft rubber, cardboard, paper and cloth materials.
- Can gain entrance through any hole larger than a half inch in diameter.
- Can reach upward 18 inches and can jump 3 feet vertically and 4 feet horizontally from a flat surface. Can fall 50 feet without serious injury.
- Can climb bricks, trees, vines, horizontal or vertical wires, or other rough exteriors that provide footholds.
- Can climb the outside of a vertical pipe up to 3 inches in diameter and any pipe size that is within 3 inches of a wall or support. Can climb inside of vertical pipes from 1 to 4 inches in diameter.
- Can tread water for three days and can swim in open water up to one-half mile against swift currents, through floor drains and toilet bowel traps.
- Can only see for several feet and are colorblind, but their senses of smell, taste, hearing, and touch are acute.
- Can contaminate food supplies and spread disease, having been associated with infectious jaundice, Bubonic plague, and typhus and are responsible for more human illness and deaths than any other mammal. They can carry as many as 35 diseases that can affect humans and livestock.
Keeping the Premises Clean
Sanitation or maintaining a clean environment outside your home or other buildings is important for controlling rodents for two reasons. First, tidy premises are unattractive to rodents because they provide little or no food, water or harborage. Rodents do not stay long in places where there is no food, water or shelter. Second, if rodents are a problem, taking away their food makes them more likely to accept bait if bait is placed where rodents will find it.
- Store dog food, bird seed and other attractive food in sealed containers. Remember that pet food left in a dish is a source of food for rats and mice.
- Regularly clean up spilled bird seed from bird feeders which are major sources of food for rodents.
- Keep garbage, litter and debris in sealed containers, picking up any loose food scraps lying around garbage cans.
- Keep water sources to a minimum. Be aware that bird baths, decorative fountains, drain spouts and ponds are sources of water for rodents.
- Clear away outside debris/clutter. Trim vegetation that provides protective cover for rodents such as brush piles, overgrown shrubbery and vines, or wood piles leaving a clean perimeter.
- Rats not only eat food, but also contaminate it with their urine and feces. Proper sanitation and storage of food help prevent contamination of food sources by rodents. Similar principles of sanitation apply to indoor areas: in food areas where you've seen signs of rodents, remove the food.
- Keep cupboards clean; wipe up spilled food and store loose food in sealed containers whenever possible. Clean food particles from under stove and refrigerator.
Clean Up Droppings
Rodent droppings can carry the Hantavirus. This can be transmitted when droppings become friable (dry enough for fragments to become airborne) and the particles are inhaled. This can happen when handling droppings, dead rodents or their nesting materials. Although this disease is rare, it is fatal; therefore, precautions should be taken when dealing with droppings and other rodent debris.
- Use rubber gloves.
- Use paper towels to wipe up moistened droppings and/or urine marks and dispose of them in a sealed plastic bag.
- Dampen any nesting materials or dead rodents with disinfectant and dispose of them in the same manner.
Prevent Rodent Entry
Even if you purchase the most effective rodent control products, you will not get lasting control if additional rodents can enter your premises from the outside. Mice can enter through an opening about the size of a dime, while a rat can crawl through an opening only the size of a quarter. Take steps to keep them out.
Rat Proofing a Structure
- Repair torn screens, fix or replace broken or missing windows, and fix non-functioning doors that can provide easy entry for rodents.
- Plug up holes, cracks and gaps in walls and foundation with coarse steel wool, galvanized sheet metal or heavy-gauge hardware cloth.
- Weather strip doors leading from the garage into the house.
- Seal openings around pipes, drain spouts, and vents. Rodents can chew through virtually anything. Sealing up likely areas of entry, such as cracked concrete, will deter them. Rats and mice can scurry indoors undetected when doors are left open, even for short periods of time. The most effective form of rodent management in structures is "rat proofing"; fixing a building so that there are no easy paths for the rats to enter.
- Cover floor drains with mesh.
Selecting and Placing Control Products
It may be necessary to use some form of rodent control product to actively eradicate the rodent pest problem. Not all infestations are alike; therefore, rodent control products are made in a variety of designs. Products include rodenticides, which are available in various bait forms; bait stations, glue boards and glue traps; and mechanical traps. When properly selected and applied in a safe manner, these devices provide positive results in controlling rats and mice.
General Baiting Strategies to Control Rats
Baiting should begin as soon as you've noticed a problem in order to prevent it from growing.
- Generally place bait close together in areas where you notice rodent activity - for mice, every 8 to 10 feet; for rats, every 10 to 30 feet. It's critical to place bait within the rodent's home range. Rats usually travel 100 to 150 feet within their home range, while mice venture only 10 to 30 feet from their nest.
- Keep bait dry and fresh. Replace any contaminated or spoiled bait.
- When storing bait, keep it separate from other products that might give off an odor that would affect bait acceptance. Be sure to store all bait safely away from children, pets and other animals.
Using Glue Boards and Glue Traps
Glue boards and glue traps are the ideal choice if you're looking for a non-poisonous rodent control product. These glue-covered traps capture rats and mice as they scurry from one point to another. They are especially effective in food areas or other locations where the use of poison is undesirable or prohibited. This type of control device is used only inside buildings.
Using Mechanical Traps
Mechanical traps are ideal to use whenever you want to avoid using poisons. Many manufacturers make mechanical traps for heavy-duty, long-lasting use. This type of control device can be used both inside and outside buildings.
Using Tamper Resistant Bait Stations
Placing bait in tamper-resistant bait stations will greatly improve your rodent control efforts. Bait needs to stay fresh and out of the elements to make it more appealing to rodents.
- Always read and follow directions for the proper use of any product.
- Keep bait away from children and pets. This includes placing the bait in areas where children and pets cannot get it, as well as storing it safely out of their reach.
- Be sure to remove unused bait after you've successfully controlled the rodent problem and baiting is no longer necessary.
- Depending on level of infestation, you may need to contact a professional.
Rodent Management Brochure (PDF)