ROOF RATS and What You Need To Know
Order Rodentia : Family Muridae : Rattus rattus
Description. A blackish (or brownish), medium-sized Roof rats have
pointed noses and large ears and are often mistaken for House Mice.
The head and feet of adult house mice are proportionally smaller than
their bodies, while young rats have larger heads and feet than their bodies.
The Roof rat's fur is smooth, while the Norway rat's fur is rough and shaggy. The adult Roof rat is
about 7-10 inches long and weighs about 5-9 ounces. The Roof Rat has a long tail, which is longer
than the head and body's combined length. If you pull the tail back over the body, it will reach over its
Habits. Roof rats live in close association with man. They may live near the ground, but usually they
frequent the attics, rafters, and crossbeams of the buildings. They make typical runways along pipes,
beams or wires, up and down the studding, or along the horizontal ceiling joists, often leaving a dark-
colored layer of grease and dirt to mark their runways. The roof rat is nocturnal and only where
populations are relatively high are they seen in the daytime.
Breeding. Roof rats reach sexual maturity at 3 to 4 months of age. Roof rats breed year-round, with
peak breeding activity in spring and fall. The litter of 5 to 8 pups are born after a gestation period of
21 to 23 days. A female roof rat can have 4 or 5 litters per year.
Hantavirus Pulmonary Syndrome (HPS): Hantavirus pulmonary syndrome (HPS) is a deadly
disease transmitted by infected rodents through urine, droppings, or saliva. Humans can contract the
disease when they breathe in an aerosolized virus. HPS was first recognized in 1993 and has since
been identified throughout the United States. Although rare, HPS is potentially deadly. Rodent control
in and around the home remains the primary strategy for preventing hantavirus infection.
Murine Typhus: Murine typhus (caused by infection with R. typhi) occurs worldwide and is
transmitted to humans by rat fleas. Flea-infested rats can be found throughout the year in humid
tropical environments, but in temperate regions are most common during the warm summer months.
Travelers who visit in rat-infested buildings and homes, especially in harbor or riverine environments,
can be at risk for exposure to the agent of murine typhus.
Rat-bite fever (RBF): Rat-bite fever (RBF) is a systemic bacterial illness caused by Streptobacillus
moniliformis that can be acquired through the bite or scratch of a rodent or the ingestion of food or
water contaminated with rat feces.
Salmonella enterica serovar Typhimurium: As its name suggests, it causes a typhoid-like disease
in mice. In humans S. Typhimurium does not cause as severe disease as S. Typhi, and is not
normally fatal. The disease is characterized by diarrhea, abdominal cramps, vomiting and nausea,
and generally lasts up to 7 days. Unfortunately, in immunocompromised people, that is the elderly,
young, or people with depressed immune systems, Salmonella infections are often fatal if they are not
treated with antibiotics.
Leptospirosis: Leptospirosis is a bacterial disease that affects humans and animals. It is caused by
bacteria of the genus Leptospira. In humans it causes a wide range of symptoms, and some infected
persons may have no symptoms at all. Symptoms of leptospirosis include high fever, severe
headache, chills, muscle aches, and vomiting, and may include jaundice (yellow skin and eyes), red
eyes, abdominal pain, diarrhea, or a rash. If the disease is not treated, the patient could develop
kidney damage, meningitis (inflammation of the membrane around the brain and spinal cord), liver
failure, and respiratory distress. In rare cases death occurs.
What you should know about ROOF RATS:
Roof rat droppings are long and cylindrical.
Roof rats are nocturnal.
Roof rats will enter homes and buildings. They only need a hole the size of a quarter to gain entry.
Roof rats are good climbers. They can climb walls and use utility lines and fences to travel from
structure to structure.
Outside, roof rats will nest in trees, woodpiles, garbage, and plants.
Inside, high places, like attics, are their preference.
Roof rats eat fruits, vegetables, nuts, pet food and invertebrates (spiders, snails and worms, for
example). They will also eat paper.
If you have the following items around your home, you may be more prone to attracting roof rats:
ROOF RAT HABITAT
Roof rats may live or establish their nests in:
Research shows that by eliminating or
reducing environmental conditions
that are conducive to pest activity you
can strongly reduce or eliminate
rodent infestations. This checklist is
designed to provide the information
necessary to assist you in your efforts
to keep a home rodent free after the
1) Remove stored items in close proximity to the structure.
2) Cut grass and/or weeds along the foundation.
3) Install hardware cloth over foundation vents.
4) Install hardware cloth over roof vents.
5) Install hardware cloth over marked openings.
6) Remove accumulated grocery bags & newspapers.
7) Repair interior plumbing leaks.
8) Repair exterior plumbing leaks
9) Caulk or seal around plumbing penetrations.
10) Move stored boxes 6” from walls.
11) Install weather striping along bottom of doors.
12) Remove pet food and water dishes when not used.
13) Store pet food in sealed containers.
14) Keep trash in sealed containers.
Your home attic and walls
Other heavy shrubbery
Wood and lumber piles
Yard and garden storage
The inspection provides you with valuable information.
The extent and severity of the infestation. Is the problem localized in one area of the building? Are the
rodents infesting several rooms? How severe is the infestation? By accurately gathering this information prior
to any control efforts, time and money can be saved by doing a thorough inspection. A common mistake in
rodent control is to underestimate the severity of an infestation either in numbers of animals or by the area
The location of rodent harborage and activity areas. By inspecting for various rodent signs, clues can be
gathered as to the location of nesting areas, as well as where and how the rodents travel from nests to their
food and water. By intensifying your control efforts at these locations, greater control can be achieved.
On the exterior...
Identify the rodent entry areas. A thorough inspection of the exterior of the building should be conducted.
Areas to inspect include all utility lines that enter the structure through the walls. All openings around water
lines, air conditioning ducts, drain pipes, vents and electrical conduits should be inspected. Of course, the
spaces beneath doors are one of the most common entryways for rodents. Doors should be checked to ensure
the lower edge is not more than ¼ inch from the floor. Broken basement windows and unscreened vents also
are common invasion routes. Also check storage sheds, garden sheds and potting sheds along with exterior
In the case of roof rat inspections, roofs should be checked to see that sheathing is complete and there are no
openings at roof junctures where one roof over laps or ties into another roof. In addition, check roof ventilators,
screen vents and louvered in-wall vents and chimneys.
Locate the areas of rodent activity. The key to effective inspections is to identify the primary harborage, feeding
and activity areas to get the best results. Typically, rodents build their nests near food sources. Therefore, the
control areas are those areas between the nest and feeding areas.
When conducting inspections it’s a good idea to think in terms of what rodents require. Inspect the building and
list all of the areas where food is available. An adult rat requires up to 1 ounce of food and water daily to
survive, food has to be readily accessible. Keeping this in mind during your inspections, begin by locating all
areas in and out of the account that provide food for rodents. This is especially useful when inspecting
structures where there is a minor infestation and the rodent zone is difficult to pinpoint. Keep in mind if there is
an abundance of snails or fruit that could be the food and water source.
On the interior...
Inside structures, a few of the more common rodent harborage locations include the following:
Secluded corners (remember rodents follow wall surfaces and prefer corners because these areas
provide them with a sense of security)
Beneath and inside cabinets
Beneath and within furniture
Beneath and behind large appliances
Floor cabinet voids in kitchens
Base voids in dresser bureaus
Sill plate areas on top of basement and crawl space foundation walls
Storage areas over a garage
There are rodent signs you should look for with roof rats: 1) droppings (feces); 2) gnawing damage;
3) runways; 4) tracks; 5) grease marks (rub marks) ;6) urine stains; 7) visual sightings of live or dead rodents;
8) rodent sounds; and 9) rodent odors.
Gnawing damage. Evidence of recent gnawing and/or damage as a result of gnawing is an excellent sign for
determining the presence of rodents. Rodents gnaw on many items including aluminum, mortar, plastic, lead
and any other items softer than the enamel of their incisors.
Urine stains and odors. Rodent urine is often deposited on their runways and other frequented areas. Under
ultra-violet light, rodent urine will fluoresce yellow on burlap bags and pale, blue-white on various packaging
paper. Rodent odors are often detectable in well established infestations.
Rodent sightings and sounds. Obviously, seeing live rodents during an inspection is a sure confirmation of an
infestation. Various sounds produced by rodents and their young are high-pitched squeaks, gnawing and
scratching sounds, and sounds of rodents moving across an attic.
Runways, tracks and grease marks. Runways are usually evident in rodent infestations because rodents
repeatedly use the same pathways between their nests and food sources.
Control strategies. In some situations you will have a wide range of control tools and strategies from which to
choose. In other cases, however, your control options may be limited due to food exposure, safety precautions
for children and non-target animals, and various environmental factors. All this can be determined through your
inspection. Of course, the goal is not only an effective control program, but a safe one.