Non-Chemical Rat Control

The most important factor to consider when controlling Norway rats is population control. Killing individual rats is not enough; the idea is to control the entire population of rats in a given area, lest "new" rats move into treated areas as quickly as the "old" rats are exterminated.

Area-wide rat population control begins with taking actions to make an area less able to support a rat population, such as:

• Reducing the amount of food and water available by implementing proper sanitation and waste management procedures. This may involve outreach to businesses and residents in which the importance of proper sanitation to effective rodent control is emphasized.
• Reducing harborage by cleaning up refuse and debris in rat-infested areas.
• Utilizing non-chemical control methods such as exclusion to keep rats from entering buildings and other sensitive areas. The National Park Service has an excellent manual for rodent exclusion, which can be downloaded here. (Adobe Acrobat Reader required.)

• Continued monitoring to evaluate the ongoing effectiveness of the rodent control program.

Trapping Rats

Trapping offers several advantages over chemical control methods:

• Trapping avoids the use of toxic pesticides and any associated risks to children, non-target animals, and the environment.
• Trapping, if done properly, can quickly reduce rat populations.
• Traps prevent rodents from dying in walls, ceilings, crawl spaces, and other inaccessible places where there rotting carcasses would create a health hazard.

Types of Rat Traps

The following are some of the more popular and effective of the many rat traps available.

Cheap, effective, and easy to use, snap traps are still among the most popular rat traps around. For best results, snap traps should be "pre-baited" without setting the bail for several days; and then when the rats have overcome their initial fear and have begun to take the bait, re-bait them and set them all on the same evening.

Snap traps should be set with the trigger end in the rats' travel paths, and only in areas inaccessible to children, pets, and non-target animals. Peanut butter, gumdrop candies, bread dough, and salami have all been used effectively as baits.

Snap traps are available at most hardware stores.

Rat glue traps are another popular non-chemical rat control device. They are considered somewhat safer than snap traps, which can cause serious injuries to human fingers and toes if accidentally touched.

Glue boards work only in dry, relatively clean areas. A rat with wet feet can walk right across a glue board without getting stuck.

Rats that get stuck to the traps may not die for quite some time after getting stuck, which many people find cruel. In addition, if the rat is still alive when you check the trap, then you will have to kill it yourself. If this makes you squeamish, or if you feel glue boards are inhumane, then don't use glueboards.

Electrocution rat traps are a newer, cleaner, and more humane way to non-chemically control rats.

The traps are baited with a suitable bait (peanut butter, cheese, oats, salami, nesting materials, etc.) and placed in the rats' travel paths. When a rat enters the trap, it immediately receives a lethal electric shock.

Live traps usually trap animals unharmed so they can be released elsewhere (although sometimes the animals may injure themselves trying to get out of the traps). Unlike the other traps on this page, live traps can also be used outdoors and pose little risk to non-target animals, who can simply be released if they are caught.

In some areas, live-trapping of rats and/or releasing trapped rats may be illegal due to their being considered a public health threat; so check with your local authorities first.

Tips for Using Rat Traps

Whatever traps you choose, the following tips will help improve the chances of a successful outcome:

• Know the rats' travel paths. You can usually find this out by looking for footprints, tail prints, gnawing, or faint greasy rubmarks along vertical surfaces. If in doubt, place a light dusting of corn starch or flour on the floor in areas where rat activity is suspected, and then look for footprints and tail prints the next day.
• Choose appropriate baits. Rats will generally choose baits that are supplementing dietary needs that are not being met elsewhere. So try a few different baits and see which one they like. Some baits that have been used successfully include peanut butter, smelly cheese, gumdrops, oat cereal, salami, bacon, raisins, and dough balls.
• Set enough traps. Most rat traps are only able to catch one rat at a time, so make sure to set enough traps based on your estimate of the population size.

Chemical Rat Control (Poisoning)

Note: Setting poisons for rats is a hazardous activity that is best left to professionals. The following information is presented for informational purposes only. Always be sure to read and follow all label instructions when using any pesticide product. Baiting should be looked upon as an adjunct to exclusion and trapping, not as a replacement for non-chemical measures.

Disadvantages of Using Rodenticides

Controlling rats by with rodenticides has a number of disadvantages:

• Poison baits designed to exterminate rats are often toxic in varying degrees to humans and other animals. Although the amount of rodenticide that would be needed to kill a larger animal is usually more than that needed to kill a rat, nonetheless many domestic pets and other non-target animals, and occasionally humans, are accidentally poisoned by rodenticides every year.
• Some (but not all) rodenticides exhibit secondary toxicity, which means that the poisoned rat may itself be toxic to other animals. If another animal (like a dog or cat) eats the poisoned rat or its carcass, that animal in turn may be poisoned by the rodenticide remaining in the rat's body.
• Because it may take several days for a rat to die after eating most rodenticides, poisoned rats can die inside wall voids or other inaccessible structural elements of a building. Aside from the stench (which can be overpowering and may last for several weeks), rat carcasses serve as a breeding medium for flies and other pests.
• Displaced ectoparasites like fleas, ticks, and mites will often seek new hosts when the rat they were parasitizing dies. Many of these parasites are vectors of potentially serious diseases.

Advantages to Using Rodenticides

When used properly, rodenticide baits have several advantages as part of an effective rat control program. For example:

• Rodenticide baits enable effective control of even large rat populations where trapping would be impractical.
• Using weather-resistant baits in tamper-resistant bait stations provides longer-term, wide-area control with minimal maintenance.
• Rodenticide baits in tamer-resistant bait stations can be used outdoors, whereas few rat traps are suitable for outdoor use.

Professional exterminators usually use rodenticides primarily in rat-prone exterior areas, or inside buildings whose construction is such that dead rodents are unlikely to be trapped in inaccessible areas.

Proper Use and Placement of Rat Poisons

The single most important part of using rodenticides is to make them inaccessible to children, pets, or non-target animals. The best way to do this is to use tamper-resistant bait stations.

Using bait stations not only reduces risk; it can increase effectiveness. Rodents are prey animals whose lives depend on avoiding predators. Bait stations provide a protected, enclosed place in which rodents feel more secure -- and in which they are more likely to eat a lethal dosage of bait. Rats are also finicky and won't readily eat spoiled food. Bait stations help keep the rodenticide fresh and palatable.

Bait Station Placement

The placement of bait stations is similar to that of traps. The stations are secured in place along rat travel paths. The rodenticide bait is then secured inside the station, and the station closed and locked.

Bait stations installed inside buildings may be secured using screws, nails, or construction adhesive. Exterior bait stations can be secured by attaching them the exterior walls of a building, or they can be secured to the ground using stakes, lag anchors, or earth anchors. All bait stations must be sufficiently secured that a child or domestic animal cannot move, shake, or open them.

Exterior bait stations are typically mounted along exterior walls of buildings, along fence lines, along wharfs and piers, and in other rat-prone areas adjacent to structures. They can also be anchored to the ground adjacent to rodent burrows, hidden in ground cover near shrubbery, under sheds, and in garbage storage areas. They should not be used in areas frequented by children or in places likely to be flooded.

Rodenticide Baits

Almost all of the rodenticides available to unlicensed individuals are anticoagulants. These baits are widely considered to be the less hazardous than other types of rat poisons because they are slow-acting and because they are more easily antidoted in the event of accidental ingestion.

Paraffinized anticoagulant baits come in a variety of shapes and sizes to fit popular bait stations. Baits sealed in paraffin are more weather resistant than grain or meal baits, less likely to be tracked by rodents through sensitive areas, and may actually be better accepted by rats because they provide something for them to gnaw on.

Whatever bait is used poisoning should be looked upon as only a small part of an overall rat control program. Sanitation, harborage reduction, and exclusion are the real keys to long-lasting protection against rodents.