Roof Rats General Information

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Roof Rats General Information

Roof Rat Fact Sheet

Roof Rat Fact Sheet (pdf/29kb/2pp)

Roof Rat (black rat, ship rat)
Rattus rattus Linnaeus

Size
Adult head and body length is 6 to 8 inches (16 to 20 cm); tail length is 7 to 10 inches (19 to 25 cm); weight is about 5 to 9 ounces, up to 12 ounces.

Characteristics
Soft, smooth fur; pointed muzzle; large eyes; large, almost naked ears, which can be pulled over the eyes. Scaly, dark tail is longer than combined head and body length.

Color
Brown with black mixed in, to gray, to black on top with white; gray or black underside.

Droppings
Adult droppings are up to .5 inches (12.5 mm) long, and are spindle shaped with pointed ends.

Where found
Roof rats are probably from southeast Asia, but they are now found around the world. In the United States, they are most common in coastal and southern states, especially near seaports.

Habitat Outdoors
Roof rats nest in high places such as trees, but sometimes in burrows under plants. Indoors: they nest in high places in structures, but sometimes in basements, sewers, or under buildings.

Food
Roof rats eat almost anything, but they prefer fruit, vegetables, and cereal products. They often get their water from their food. They eat a lot at one time, and will return to their food source often.

Understanding Roof Rat Behavior

Common signs of roof rat activity

Visual sightings on power lines, trees, bushes, patios, roofs, etc.
Hollowed citrus and other fruit
Rat droppings
Noises in the attic and walls
Gnawing sounds and gnaw marks around roof eaves
Damage to plastics and coverings on electrical wires
Unsettled pets

Places roof rats have been found

They have been found in swimming pools, laundry rooms, attics, garages, and patios.
They’ve been seen on power lines in the alleys.
Roof rats spend 90 percent of their life 4 feet or more off the ground.

Roof rat traveling patterns

Roof rats are strongly arboreal (tree inhabitants) and travel along power lines to trees, oleanders, vines, and roofs.
They can climb up brick, concrete block and other rough surfaces.
They can jump 2 feet up and 4 feet horizontally (double the horizontal distance if they are jumping from a height).
Ground covers and compost bins also provide safe travel routes and nests.
During twilight and nighttime hours, within a territory 200 to 300 feet from their daytime nesting locations.
They thrive in cool weather and are most active from November through May.

How roof rats enter homes

They enter homes, sheds, garages and other structures through any opening larger than a nickel, looking for places safe from predators and good for nesting.
They may follow pipes down from the attic, gnaw through drywall, to access structures
They may chew through wood, plastic, aluminum siding, sheet rock, and soft metals to gain access to interiors.
Attics provide a safe refuge, a nesting place for their young and routes into the home below.

What roof rats eat and drink

They love to eat all types of citrus and other fruits, and nuts, including:

Lemons
Limes
Grapefruits
Oranges (including ornamental oranges)
Tangelos
Tangerines
Figs
Pomegranates
Palm fruit, including Queen Palm fruit, especially in summer when citrus is not available
Nectarines
Peaches
All nut fruits like walnuts, almonds and pecans
Rats do not have a discerning taste for fruit like humans
Fruit can be green (unripe) or even rotted
Rats eat fruit more for their water content than for food sustenance

They’ll also eat:

Bird seed (both in feeders and stored in bags)
Dog and cat food (left outside after dark are favorites)
Stored grains
Vegetables in your garden
Insects
Lizards
Tree bark
Soap
Paper
Animal and taxidermy hides
Beeswax and candle wax

Water sources include:

Leaky faucets
Leaky sprinkler heads
Leaky irrigation boxes
Bird baths
Water fountains
Ornamental ponds
Irrigation lines
Air conditioner condensation drip lines
Saucers under potted plants
Pet water dishes
And remember, they will chew through metal and plastic pipes to reach water!

Actions to take if you see evidence of roof rats on your property

First, see the section on Roof Rat Prevention in the next section for complete instructions on ways to discourage rats from feeding and nesting in and around your property.
Report sightings to the Maricopa County Environmental Complaint Line at (602) 506-6616 or log your complaint at www.maricopa.gov/envsvc.
Maricopa County officers identify and test rat specimens throughout the county.
Roof rats throughout Maricopa County continue to test negative for tularemia (rabbit fever), Hantavirus, and plague.

Roof Rat Prevention

Roof Rat Prevention (pdf/33kb/4pp)

Manicure your landscape

Roof rats are not indigenous to Arizona, and therefore try to escape the heat by harboring in thick shrubs where there is moisture and protection; a clean yard is a deterrent.
Thin out bushes until daylight can be seen through them; oleanders and bougainvilleas are particularly prone to harboring roof rats.
Prune trees and shrubs up from the ground at least 12 inches so the ground beneath is open and visible.
Prune back all tree branches from all structures by at least 6 feet.
Rake dry leaves, old growth and weeds from under trees and shrubbery.
Thick ground covers should be thinned.
Keep palm trees trimmed. Roof rats nest in the skirts of old fronds, as well as in piles of debris and hollow trees.
Take down all vines/shrubs growing against the home or perimeter walls
Remove wood and brush piles from yard.
Eliminate piles of lumber and firewood, or store them at least 18 inches above ground and at least 12 inches from walls.

Harvest citrus and other fruit

Promptly and completely pick all fruit (ripe or not) on citrus and other fruit and nut trees, and pick up fallen fruit every season.
Fruit and nut trees that touch other trees, houses, fences or power lines have more roof rat activity, so prune to isolate each tree.
If you can’t physically pick your trees, go through the yellow pages for landscapers who might. Those landscapers who will pick – not all do – typically charge between $15-$25 per tree.
Residents can also call their faith community for youth groups who might be looking for community service work or Boy/ Girl/ or Eagle Scouts, as well.
Consider donating excess fruit to the nearest food bank.
With proper care, fruit and nut trees do not need to be removed, but you may want to consider this if upkeep is not possible for you.
Check for the seasonal citrus drop off program (generally from January to March each year). In a partnership between the city, residents and county agencies, this program makes citrus drop off possible, with viable fruit being distributed to food banks and county facilities. Sponsored by the NEIGHBORtoNEIGHBOR Campaign, more information is available by calling (602) 273-0435.
Short of cutting a nut tree down, there is virtually no way to stop a nut bearing tree from being a roof rat’s food source. But the tree will make a good place for a bait station (see section on bait stations and snap traps).

Don’t unknowingly feed roof rats

Roof rats will eat anything to survive – this includes all domestic and wild animal food, garbage, and animal feces.
Keep all pet feces off the ground at all times.
Don’t leave pet food out, especially overnight.
Consider not filling bird feeders until all signs of roof rat activity have ended, or provide just the amount of bird seed that will be consumed in a day and sweep up fallen seeds before sunset.
Store bulk foods and seeds in metal, sealed, rat-proof containers. (Rats will eat through plastic bins.)
Keep garbage containers tightly covered.

Eliminate standing water

All water sources on private properties are a welcomed invitation to a roof rat. This can include birdbaths, dog/cat water bowls, fountains, water features, and pools.
Drain or empty all standing water sources except pools and spas. Draining standing water also helps prevent mosquito breeding issues.
Change pets’ drinking habits by training them to go inside for a drink, if your dog/cat is used to drinking water from a bowl outside.
Do not leave food or water outside for stray/neighborhood animals.
Keep pool water level at least 6 inches below the decking surface. If a rat falls in while getting a drink, it won’t be able to get out of the pool and can drown. Dead rats can be fished from the pool with a long-handled net and disposed of in city trash containers.

Seal your home and other structures

The most extensive damage occurs when roof rats enter the home, so the first goal is to keep them out!
Caulk all holes, cracks, crevasses, or gaps (any opening larger than a nickel) on the exterior walls and underneath the eaves of block and/or wood constructed homes/outbuildings, sheds, etc.
Look for holes in exterior walls and near hot water heaters, washers, dryers, dishwashers, and under sinks.
Roof vents and attic turbine ventilators should be checked and screened if necessary.
Fireplaces need to be protected with the proper screening of a chimney cap.
Tile or wood shake roofs should be closely inspected for openings.
Pet doors, vents, and exterior door and window screens should be secured at night.
Use stucco diamond mesh or steel wool and a flathead screwdriver and push the material into all questionable areas, to screen and seal all holes and air vents leading into the home or shed. It cuts and molds very easily. For aesthetic purposes, you can use paintable caulk to go over the areas containing the steel wool and then paint over the caulk.
If window or door screens are loose, either reinforce or replace.
Stuff the cover of the air conditioning line that runs from the outside unit into the attic with steel wool or copper mesh to prevent rats from climbing up the insulated pipe inside the cover. Look for scratch marks on the insulation, and then set a snap trap to catch them the next time they use that entrance.
Always shut doors when exiting/entering the home.

NOTE: Screens placed on clothes dryer vents should be checked often and cleaned for accumulated lint. Not cleaning the screen could result in the malfunction of the dryer and/or possibly result in a fire.

What doesn't work

Rats quickly learn safe travel routes through yards to avoid dogs.
Cats will kill juvenile rats, but are rarely able to handle an adult roof rat.
There is no evidence that ultrasonic and electromagnetic devices drive rodents away. However, there is evidence that they can cause hearing loss in pets, especially dogs.
Maricopa County Vector Control tested Coca Cola (rumor has it that roof rats can’t burp and die from drinking it), but found that it didn’t work. In fact, the rats loved it.
Don’t use “d-Con” bait; if pets or wild birds nibble on a rat killed with it, they can become sick.

Long term solutions

Strongly consider xeriscaping the yard. Xeriscape (the use of drought tolerant plant materials and drip irrigation systems) doesn’t have to be just gravel and a couple of cactus; there are many lovely options. Extensive information on xeriscape methods and ideas are available from the city’s Water Conservation Office at (480) 312-5670.
Combine xeriscape with a citrus-free yard to create a very effective control against roof rats.
Maintain a defensive line on your property by continuing the use of bait stations, keeping a clean yard and removing pet food and water dishes at night.

Bait Stations and Snap Traps

Snap traps (designed with a trigger mechanism) can be purchased at home improvement stores. Bait stations can be purchased at cost through the NEIGHBORtoNEIGHBOR network at www.roofrat.net or residents can make their own bait stations by visiting the same website or a local hardware store for ideas. Neither Maricopa County nor the city provide bait stations or snap traps.

Bait stations

Bait stations come in all sizes and shapes and can be made as simply or complex as you see fit. Bait stations can be made out shoe boxes, wood or PVC tube to name a few. Examples of bait stations and how to make them can be found by visiting www.roofrat.net.

If you deploy bait stations on your property, you are responsible for all baiting and maintenance of each bait station for the duration deployed. Residents are also fully responsible for purchasing and placing the proper poison in each bait station.

Safety Precautions

Place bait stations well away from children and pets!

Always read and follow all bait manufacture’s handling instructions and precautions.

In case of emergency regarding bait, call the local Poison Control Center at (602) 253-3334.

Toxic bait should never be used in the home or in the home’s crawl space. For these areas, see the section on snap traps (below).

Before setting bait and bait stations, it is imperative that you properly seal your house to avoid poisoned rats from entering the house and dying, creating a bad odor which may be hard to remove.
Bait stations are for “housing” toxic bait, not for trapping the roof rat. The roof rat enters the station, eats the bait, and then leaves. Within 3-6 days after ingestion, the poisoned rat dies.
Bait stations provide a protected place for rats to feed. They allow residents to place poison bait in some locations where it would otherwise be difficult because of hazards to small children and/or non-target animals.
For bait, use the anti-coagulant ingredient “Bromadiolone” which is sold as “Just One Bite” and can be purchased at feed and hardware stores.
Residents are responsible for purchasing and placing the bromadiolone poison in the bait station. Read the entire label first and strictly adhere to all instructions, restrictions, and precautions.
Place two or more bait stations in your yard, depending on the size of the property and the number of trees and shrubs.
Optimal locations are in trees and on any potential rat pathways, such as shrubs, perimeter fences and roofs.
Use a metal strap to secure bait station to a tree or wall with screws or nails.
Place the station’s entry point in a slightly upward position. The bait station is most effective from 4’ to 6’ above ground at no greater than a 25-degree angle.
Install unit where it is easy to inspect for any rodent activity.
Normally, birds will not seek out or be attracted to bait that is properly enclosed in bait stations; however, if you are concerned, you may choose to close the bait station openings in the morning to protect wild birds, and open them in the late afternoon about sunset.
The practice of wiring poison bait “blocks” directly to tree branches without a bait station may cause accidental poisoning of cats and wildlife; use poison bait blocks only in bait stations and slide the blocks all the way to the back.
It is recommended to check and refill bait stations at least weekly and they may need to be checked up to daily during times of heavy use.
Bait stations should be deployed and monitored year round.
See the section on handling dead rats, rat droppings, and nesting areas for complete instructions and safety precautions.

Snap traps

Snap traps (like those used for mice) are intended to be baited with a food source and to kill the rat as the rodent attempts to eat the bait. These traps must be emptied of the dead rodent and reset after each use. They are recommended for use only in areas where bait stations are not feasible, such as inside the home.

Safety Precautions

Only place snap traps well away from children and pets

Use snap traps in any crawl space or attic. These mechanical traps are spring loaded and are constructed of wood or plastic. They can be purchased at most home improvement stores for a few dollars.

Snap traps come in two sizes (small and large). The small are for mice and the large are for rats.

How to bait and deploy snap traps

Bait snap traps “lightly” with creamy peanut butter so the rat will have to work hard to get it off the trigger, which will ensure that the trap will ‘trip’. OR…
Bait snap traps with a mixture most people can make in their own kitchen (dry oats, creamy peanut butter, and nuts or peanuts). Mix the oats and creamy peanut butter together in a bowl until it reaches the consistency of cookie dough. Roll a small “dough ball” in the hands (about the circumference of a quarter). Slip the nut of choice into the middle of the “dough ball.” Re-roll the ball a bit in the hands. Place the “dough ball” (AKA: “bait”) on the lever of the snap trap where the “bait” is designed to rest. Use dental floss to “tie down” or secure the “bait” to the lever (the nut inside the “bait” will keep the dental floss from going completely through). It is important to secure the bait onto the trap’s lever to prolong the time the rat will spend at the trap. Often, the rat is quick enough to evade a lethal snap, hence defeating the trap’s purpose.
Any questions regarding the proper deployment of snap traps should be directed to the trap manufacturer.
When used in attics, snap traps should be placed within arms length of the entrance into the crawl space/attic.
It is also recommended that each snap trap be secured down to the wood framing/rafter within the attic. If a rat evades the lethal snap of the trap, yet is still caught in the apparatus, the rat can potentially scamper away connected to the trap to die elsewhere in the attic, thus causing an unnecessary odor and expense to the homeowner.
Check snap traps daily, but don’t move or disturb them if there is no rat captured. Roof rats are nervous and cautious of new objects, so leave snap traps in the same location for at least a week without physically disturbing them, unless a rat has been captured.

Bait

Rodenticide Used: Bromadiolone

Registered with the U.S. Environmental Protection Agency (EPA) and recommended for use in alleys for roof rats.
Newer class of anti-coagulant with extremely low level of active ingredient.
Anti-coagulant reduces the ability of blood to clot so that the rat bleeds internally and dies (usually within three to five days).
Each station will have eight ounces of bait (four two-ounce blocks), consisting of .005% rodenticide and 99.95% food substances like grain and flavoring.

Bromadiolone Toxicity Levels:

LD50>5000mg/kg. LD50 means 50% mortality rate when eating 5000mg/kg. The lower the LD50, the higher the toxicity.
Compared to Nicotine: LD50=53; Caffeine: LD50=192; Aspirin: LD50=1240; Table Salt: LD50=3320.
A 22-pound dog would have to eat nine pounds of bait (the full contents of 18 bait stations) to have a 50% mortality rate without treatment.
A four-pound cat would have to eat 2.5 pounds (the full contents of five bait stations) to have a 50% mortality rate without treatment.
Vitamin K1 is an effective antidote for anticoagulant poisoning.
Secondary effects: A cat would have to eat more than 30 poisoned rats to have a toxic effect.

Over the Counter Bait

"Just One Bite" or any anti-coagulant containing the active ingredient "bromadiolone" can be purchased at any local hardware/feed store.

Safety Precautions

Safety Precautions: Handling dead rats, rat droppings, and nesting areas

Roof rats throughout Maricopa County continue to test negative for tularemia (rabbit fever), Hantavirus, and plague, however the following procedures are recommended by the county:
Ventilate the affected area the night before cleanup by opening doors and windows.
Spray dead rats, droppings, nests, and surrounding areas with a 10 percent
bleach solution (one part bleach and nine parts water).
Always maintain adequate ventilation when spraying the bleach solution and allow at least 15 minutes for ventilation before removing anything from the sprayed area.
Use rubber gloves and wear a face mask when handling dead rodents or when cleaning areas that they have inhabited.
Large zipper food storage bags can serve as a protective glove when turned inside out. The rat can then be picked up and pulled through the bag opening (making the bag right side out), zipped shut and thrown away.
Clean the affected area with paper towels or a mop. Do not sweep or vacuum.
Double bag both the disinfectant-soaked rat and cleanup materials securely in plastic bags and seal. Dispose of in city trash containers.
Before removing gloves, wash in disinfectant, then soap and water. Dispose of gloves with other household waste.
Thoroughly wash hands with soap and water after disposing of all items.

Roof Rat FAQs

Roof Rat FAQ (pdf/30kb/2pp)

What are common signs of roof rat activity?

Visual sightings on power lines, trees, bushes, patios, etc.
Hollowed citrus and other fruit
Rat droppings
Noises in the attic and walls
Gnawing sounds and gnaw marks around roof eaves
Damage to plastics and coverings on electrical wires
Unsettled pets

What should I do if I see evidence on my property?

Call the Maricopa County Environmental Complaint Line at (602) 506-6616
or log your complaint at www.maricopa.gov/envsvc. Vector Control officers
identify and test rat specimens throughout Maricopa County.

How should I handle dead rats, rat droppings and nesting areas?

Use rubber gloves and wear a face mask.
Ventilate the affected area the night before cleanup by opening doors and
windows.
Spray dead rats, droppings, nests and surrounding areas with a 10 percent
bleach solution (one part bleach and nine parts water). Allow at least 15
minutes before removing.
Clean the affected area with paper towels or a mop. DO NOT SWEEP OR
VACUUM. Double bag both the disinfectant-soaked rat and cleanup
materials securely in plastic bags and seal. Dispose in city trash containers.
Before removing gloves, wash in disinfectant, then soap and water.
Dispose of gloves with other household waste. Thoroughly wash hands with soap and water.

Where have roof rats been found?

They have been found in swimming pools, laundry rooms, attics, garages and
patios. They’ve been seen on power lines in the alleys. Roof rats spend 90
percent of their life 4 feet or more off the ground.

When do they travel?

During twilight and nighttime hours in a territory 200 to 300 feet from their
daytime nesting locations. They thrive in cool weather and are most active
from November through May.

How do they travel?

Roof rats are strongly arboreal and travel along power lines to trees,
oleanders, vines and roofs. They can climb up brick walls and other rough
surfaces. They can jump 2 feet up and 4 feet horizontally (double the
horizontal distance if they are jumping from a height). Ground covers and
compost bins also provide safe travel routes and nests.

How do they enter homes?

They enter homes and garden sheds through any opening larger than a nickel. They follow pipes down from the attic, gnaw through drywall and enter the
kitchen or base sink cabinets. They chew through wood, plastic, aluminum
siding, sheet rock and soft metals.

Why attics?

These rodents are fond of attics because they provide a safe refuge, a nesting
place for their young and routes into the home below.

What do they eat and drink?

They love to eat citrus fruit (because it serves as both a food and water source) and other fruit (pomegranates, figs, etc.), nuts, seeds and stored grains, and vegetables in your garden. They also eat insects, lizards, tree bark, soap, paper, hides, and beeswax.
Bird seed (both in feeders and stored in bags) and dog and cat food left
outside after dark are favorites. Roof rats eat Queen Palm tree fruits in the
summer when citrus isn’t available.
Water sources include leaky faucets and sprinkler heads, bird baths, fountains
and ornamental ponds, irrigation, air conditioner condensation drip lines,
saucers under potted plants, and pet water dishes. They will chew through
metal and plastic pipes to reach water.

How do I seal my home?

The most extensive damage occurs when roof rats enter the home, so the first
goal is to keep them out.
Use stucco diamond mesh to screen and seal all holes and vents leading into
your home or garden shed. It cuts and molds very easily. For the rat, this
mesh is like biting into small razor blades.
Look for holes in exterior walls and near hot water heaters, washers and
dryers, dishwashers, and under sinks. Don’t forget to screen sewer stacks on
the roof.
Caulk all cracks.
Stuff the cover of the air conditioning line that runs from the outside unit into
the attic with steel wool or copper mesh to prevent rats from climbing up the
insulated pipe inside the cover. Look for scratch marks on the insulation, and
then set a snap trap to catch them the next time they use that entrance.

Do roof rats carry disease?

Roof rats throughout Maricopa County continue to test negative for tularemia
(rabbit fever), hantavirus and plague.

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