Environmental Programs -
Tips for Dealing with Roof Rats

PLEASE NOTE: The appearance of roof rats is NOT a sign of neighborhood deterioration. They are NOT spreading incrementally block-by-block throughout the Valley. For example, these creatures can be unknowingly stored away in moving boxes by someone relocating from another area. They seek neighborhoods that meet their needs. So be sure yours doesn’t!

Visual sightings on power lines, trees, bushes, patios, etc.

Hollowed out 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

Call the Maricopa County Vector number 602-506-6616 - hit #3 and report under the category of "Smoking automobiles and other environmental issues"

Use rubber gloves.

Ventilate the affected area the night before cleanup by opening doors and windows.

Spray dead rats, droppings, nests and surrounding areas with a 10% bleach solution (one part bleach and 9 parts water). Allow at least 15 minutes of contact time before removal.

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.

Taken from Marin/Sonoma Mosquito and Vector Control District handout

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

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 straight up and 4 feet horizontally (double the horizontal distance if they are jumping from a height). Bear in mind that ground covers and compost bins also provide safe travel routes and nests.

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.

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

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.

Birdseed (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, birdbaths, 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.

The most extensive damage occurs when roof rats enter the home, so the first goal is to keep them out.

Use stucco diamond mesh available at building material suppliers 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 off the sewer stacks on the roof.

All cracks should be caulked.

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 there to catch them the next time they use that entrance.

Pick all fruit (ripe or not) on citrus and other fruit and nut trees and pick up any fallen fruit. Do this promptly and completely. Fruit and nut trees having the most activity are the ones which come in contact with other trees, houses, fences or with power lines running through.

Donate any excess fruit your family won’t be able to eat to the closest food bank.

Next winter, when the roof rats are under control or eradicated altogether, enjoy your harvest, but be sure to pick your fruit promptly and donate what you can’t use. You don’t need to remove fruit trees from your landscape.

A clean yard is a deterrent.

Rake under your trees and shrubbery. Prune fruit trees so the ground under them is open and visible. Remove woodpiles and brush piles from your yard. Store wood and lumber piles at least 18 inches above the ground and 12 inches away from walls. Thick ground covers should be thinned.

Keep your palm trees trimmed. Roof rats nest in the skirts of old fronds, as well as in piles of debris and hollow trees.

Thin out bushes until you can see daylight through them. Oleanders are particularly prone to harbor roof rats in the summer. Thin bougainvilleas as well.

Don’t leave pet food out, especially overnight. Keep dog feces picked up.

It would be best to stop filling your bird feeders for the next few months. Otherwise, provide just the amount of birdseed that will be consumed in a day and sweep up fallen seeds on the ground before sunset. Store bags of birdseed in sealed, rat-proof containers.

Store bulk foods in sealed, rat-proof containers.

Keep garbage containers tightly covered.

To prevent rats from entering your property, or to eliminate rats that have already entered your property, set snap traps in your laundry room and garden shed baited with creamy peanut butter. Don’t put much on the bait tab so the rat will have to work at it to get it off. This will ensure that the trap will trip. Place the traps well away from pets and small children. Roof rats are nervous and cautious of new objects, so leave traps in the same location for at least a week before moving them.

Bait stations made of plastic, cardboard or metal provide a protected place for rats to feed. They allow you to place poison bait in some locations where it would otherwise be difficult because of hazards to non-target animals.

Place two bait stations in your yard, 4 feet or higher off the ground. Optimal locations are in your citrus tree and anywhere near potential rat pathways, such as close proximity of wires to house roofs, trees or oleanders.

It’s important to close the bait station opening in the morning to protect wild birds that might be attracted. Open it up in the late afternoon about sunset.

The practice of wiring poison bait blocks directly to tree branches causes accidental poisoning of cats and wildlife. Use poison bait blocks only in bait stations and slide the blocks all the way to the back.

Bait stations can be purchased at cost through Barry Paceley at www.paceley.net/n2n

Residents will be 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.

Bromadiolone is sold as "Just One Bite" and can be purchased at feed and hardware stores. "Just One Bite" is an anti-coagulant that kills rats in 3-5 days.

It is important that the resident’s home is properly sealed so the poisoned rat doesn’t enter the house and die, creating a bad odor which may be hard to remove.

Rats quickly learn safe travel routes through yards to avoid dogs. Cats will kill dispersing juvenile rats, but are rarely able to handle an adult roof rat.

There is no evidence that ultrasonic and electromagnetic devices drive rodents away. There is evidence that ultrasonic devices 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 was ineffective. In fact, the rats loved it.

Don’t use d-Con. If pets or wild birds nibble on a rat killed with d-Con, they can become sick.

Strongly consider xeriscaping your yard. Xeriscape doesn’t have to be gravel and a couple of cactuses. There are many lovely options.

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.