common brown rat (Rattus norvegicus -- also called the Norway
rat or sewer rat) is a destructive animal pest found in and around
towns and farms. These rodents eat and contaminate large amounts
of feed, damage structures by their gnawing and burrowing and may
spread diseases that affect livestock and people.
The presence of rats can be detected by droppings or evidence
of fresh gnawing. Tracks can be seen in mud and on dusty surfaces.
Runways and burrows may be found next to buildings, along
fences, and under low vegetation and debris.
Norway rats are fairly husky, brownish rodents that weigh about
11 ounces. They are about 13 to 18 inches long including the 6 to
8 1/2 inch tail. Their fur is coarse and mostly brown with scattered
black on the upper surfaces. The underside is typically grey to
will eat nearly any type of food, but they prefer high-quality foods
such as meat and fresh grain. Rats require 1/2 to 1 fluid ounce
of water daily when feeding on dry food. Rats have keen taste, hearing,
and sense of smell. They will climb to find food or shelter, and
they can gain entrance to a building through any opening larger
than 1/2 inch across.
have litters of 6 to 12 young, which are born 21 to 23 days after
mating. Young rats reach reproductive maturity in about three months.
Breeding is most active in spring and fall. The average female has
4 to 6 litters per year. Rats can live for up to 18 months, but
most die before they are one year old.
Sanitation: Poor sanitation and the presence of garbage allows
rats to exist in residential areas. Good sanitation will effectively
limit the number of rats that can survive in and around the home.
This involves good housekeeping, proper storage and handling of
food materials and refuse and elimination of rodent harborage (shelter).
Outside dog pens must be properly maintained, to reduce potential
farms where food grains are handled and stored, or where livestock
are housed and fed, it is difficult to remove all food that rats
can use. In such situations, paying particular attention to removing
shelter that rats can use for hiding, resting, and nesting is valuable
in reducing rat numbers.
grain mills, and silos are especially vulnerable to rodent infestation.
Store bulk foods in rodent-proof buildings, rooms, or containers
whenever possible. Stack sacked food on pallets with adequate space
left around and under stored articles to allow inspection for signs
of rats. Good sanitary practices will not eliminate rats under all
conditions, but will make the environment less suitable for them
Construction: The most successful and permanent form of rat
control is to "build them out" by making their access
to structures impossible. Ideally, all places where food is stored,
processed or used should be rodent-proof. Store bulk foods, bird
seed, and dry pet food in metal trash cans or similar containers.
any openings larger than 1/4 inch to exclude both rats and mice.
Openings where utilities enter buildings should be sealed tightly
with metal or concrete. Equip floor drains and sewer pipes with
tight-fitting grates having openings less than 1/4 inch in diameter.
Doors, windows and screens should fit tightly. It may be necessary
to cover edges with sheet metal to prevent gnawing.
Trapping is an effective method of control. It is the preferred
method in homes, garages, and other structures where only a few
rats are present. Trapping has several advantages: 1) it does not
rely on inherently hazardous poisons; 2) it permits the user to
determine if the rat was killed and 3) it allows for disposal of
rat carcasses, thereby eliminating odor problems which may occur
when poisoning is done within the buildings.
inexpensive wood-based snap trap is available in most hardware and
farm supply stores. Wire cage traps are more expensive but somewhat
more successful than snap traps. Bait traps with peanut butter or
a small piece of hot dog, bacon, or nutmeat tied securely to the
trigger. The trigger should be set lightly so that it will spring
easily. Set traps close to walls, behind objects, in dark corners,
and in places where rat activity is seen. Place the traps so that
rats, following their natural course of travel (usually close to
a wall), will pass directly over the trigger.
enough traps to make the campaign short and decisive. Leaving traps
unset until the bait has been taken at least once reduces the chances
of rats becoming trap-shy.
Poison Baits (Rodenticides): Rodenticides are poisons that kill
rodents. They are available as either non-anticoagulants or as anticoagulants.
They can be purchased in hardware stores, feed stores, discount
stores, garden centers, and other places where pesticides are sold.
non-anticoagulants cause death either via the nervous system or
via the release of calcium into the bloodstream. Anticoagulants
cause death as a result of internal bleeding, which occurs as the
animal's blood loses its clotting ability and capillaries are destroyed.
The active ingredients are used at low levels, so bait shyness does
not occur when using properly formulated baits.
of these baits kill rats only after they are fed on for a number
of days. The exceptions are brodifacoum or bromadiolone, which are
capable of causing death after a single feeding. However, rats do
not die for several days. When anticoagulant baits are used, fresh
bait must be made available to rats continuously as long as feeding
occurs. Depending on the number of rats, this may require up to
Selection and Placement: Baits are available in several types.
Grain baits in a meal or pelleted form are often available in bulk
or packaged in small plastic, cellophane, or paper packets. These
"place packs" keep baits fresh and make it easy to place
baits into burrows, walls, or other locations. Rats will readily
gnaw into these bags to get at an acceptable bait. Block style baits
are also very effective for most baiting situations.
of tamper-resistant bait boxes provides a safeguard to people, pets,
and other animals. Place bait boxes next to the walls, with the
openings close to the wall, or in other places where rats are active.
When possible, secure the bait station to a fixed object to prevent
it from being moved. Label all bait boxes clearly with the words
"Caution--Rat Bait" or another similar warning.
and Electronic Devices: Rats quickly become accustomed to regularly
repeated sounds. Ultrasonic sounds, those above the range of human
hearing, have very limited use because they are directional and
do not penetrate behind objects. Also, they quickly lose their intensity
with distance. There is little evidence that sound of any type will
drive established rats from buildings or otherwise give adequate
and Biological Control: Although house cats, some dogs, and
other predators kill rats, they do not usually give effective rat
control. It is not uncommon to find rats living in very close association
with dogs and cats. Rats frequently live beneath a doghouse and
soon learn they can feed on the dog's food when he is absent or
asleep. Many rat problems around homes can be related to the keeping
of pets, on the other hand, some cats and dog breeds will reduce
existing rat problems.
by Entomologists at the Illinois Department of Public Health, University
of Illinois, Illinois Natural History Survey, and Purdue University.
For additional copies, contact your unit office of the University
of Illinois Cooperative Extension Service.
Illinois 1995. Issued in furtherance of the Cooperative Extension
Work Acts of May 8 and June 30, 1914, in cooperation with the U.S.
Department of Agriculture. Dennis R. Campion, Interim Director,
Cooperative Extension Service, University of Illinois at Urbana-Champaign.
Fact Sheet, NHE-PH-1, Revised 4/96