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Living with roof rats

Roof rats are one of the most common small mammals in many neighborhoods and also one of the most misunderstood. These good climbers like to nest in high, dry places such as attics, barns, and roofs in the western, southern, and southeastern areas of the United States. The tails of roof rats are longer and their snouts are thinner and longer than those of their relatives, Norway rats. Norway rats are also larger and stockier than roof rats. While Norway rats can be found nearly everywhere, they are most common in densely populated urban areas of the eastern United States. Unlike roof rats, Norway rats are poor climbers who prefer to live at ground level or below, often in damp places such as sewers and basements.

The more one learns about roof rats the more one is motivated to take a humane and ecologically mindful approach when dealing with them. The reality is that roof rats are a part of our neighborhood ecosystems. There are probably hundreds of thousands of roof rats in the San Francisco Bay Area alone. Removing them all is impossible. Therefore, learning to live comfortably with our roof rat neighbors makes life easier for everyone. Roof rats generally do not pose a significant risk to human health. According to the U.S. governmentʼs Centers for Disease Control and Prevention, in recent decades rat-associated plague in humans in the United States occurs rarely (an average of seven cases annually), typically in rural areas.

The general rule: if roof rats arenʼt bothering us, it is best to leave them alone. If they are bothering us we are probably providing them access to food, water, and shelter. When roof rats find their way into our crawl spaces, attics, or walls we need to know how to escort them outdoors humanely, seal our homes to prevent them from re-entering, and remove the attractants that are luring them to our property.

Avoid trapping.

One obstacle to living harmoniously with roof rats and other wildlife is to take an adversarial “us versus them” approach to them. Roof rats intend no harm to humans. They are not trying to outwit us. These fellow mammals have the same basic needs for food, water, shelter, and safety that we have. Another obstacle can be professional pest control technicians who sometimes try to make people afraid of these generally benign creatures and convince them that roof rats should be lethally trapped.

Inhumane snap traps cannot eliminate roof rats. Every roof rat that is killed leaves an ecological vacancy soon to be filled by another. Poisons are out. Not only do poisons cause suffering, but also they can secondarily kill your domestic pets, other wildlife, and birds of prey that catch and consume slow-moving, poisoned rats. In a study in southern California, rodent poison traveled up the food chain from rodents to coyotes to mountain lions, causing death to all. Children can also come across the poisonous bait. Likewise, setting out a bait made of plaster of Paris mixed with oatmeal that hardens once it is inside the rats can also attract other wildlife, birds, and pets, resulting in suffering and death.

As for glue traps, not only rats but also birds and other small mammals that become stuck to them suffer greatly. Both glue traps and sticky substances designed to trap animals who touch or walk on them should never be used. Some terrified animals who become stuck to them tear off their limbs when struggling to escape. Scratch all of these unnecessary and cruel ways of dealing with roof rats.

Getting rid of roof rats

Consider using this easy 3-step method. We used it to remove 15 rats from our home in less than two weeks.

  1. Find and seal the openings in your house where the rats entered.
  2. Humanely trap the rats and return them outdoors.
  3. Remove rat attractants from your property.

We hired a technician trained in rat exclusion to inspect our house thoroughly from roof to basement. We made it clear that he was hired to inspect and seal the house only, no trapping. He found that rats had entered through a hole in our foundation vent and through gaps around pipes in our furnace room. Some rats can enter holes the size of a dime. He sealed all openings with 1⁄4” hardware cloth.

After sealing the house, immediately set humane traps in areas frequented by the rats, or the rats now trapped inside your house may starve, die, and cause a foul odor in inaccessible areas. Use a “Havahart” Trap (16”x6”x6-3/8”) available at local hardware stores for about $29. Bait the trap with a dab of peanut butter and jam. Set traps where you see rat droppings, and check traps several times daily, especially in the evening when rats are active. Release them on your own property at night. Rats cannot re-enter your house once it is thoroughly sealed. Havahart traps allow you to release the rats easily without touching them. When the baited traps sit untouched for two weeks without catching any more rats, put the traps away.

A temporary option until the access holes are sealed

The goal is to keep roof rats out of a house or building permanently. To accomplish this, access holes used by roof rats must be closed. Rodent repellent strobe lights may be an option if a homeowner needs to keep roof rats out during construction while remodeling. The rodent repellent strobe lights can be placed in areas frequented by roof rats until the construction is completed and no openings to the house remain. Then humane traps can be set to catch and release outdoors any rats that might remain.

Roof rats in your garden?

Make sure you identify the animal correctly. If a critter is eating your vegetation during the day, it may be a squirrel, not a roof rat. Squirrels are active during the day. If the nibbling is occurring at night, the critter may be a roof rat or other nocturnal animal. Most troubling situations can be prevented or eliminated by removing attractants or placing repellents where rats are unwanted (see information on repellents in “Rats in your vehicle?” below). Feelings of concern over the presence of roof rats can be reduced if we are willing to share some of the vegetation in our gardens.

For example, last year there were over 200 oranges on our eight-foot tall orange tree. Roof rats sometimes eat the inside of an orange, leaving the empty peel dangling from the tree. The roof rats consumed only 10-15 of our oranges at most, a very small percentage of the total, which we were happy to share. Keep in mind that in order to survive, roof rats and other wild creatures depend entirely on the food they find. There are no grocery stores for wild critters.

Roof rats in your vehicle?

Sometimes rats make nests in seldom-used vehicles. One effective method to deter rats from vehicles is to place a light such as a “trouble light” or even a string of white holiday lights under the vehicle to illuminate the vehicleʼs underside at night. Also place various repellents such as cotton balls or rags saturated with spearmint, peppermint, or eucalyptus oils on plates near where rats are seen. Some people spray Critter Ridder, a pungent repellent, in areas frequented by rats. It is also important to keep vehicle parking sites free of attractants such as human, pet, or wild bird food.

How to discourage roof rats

Remove rat attractants from your property. You may need to make changes in your garden. We took down our bird feeders, whose spilled seed had attracted rats. Instead, we have birdbaths, which birds enjoy year-round. We keep tight lids on our compost bin and garbage cans. We lined the inside of our compost bin, which the rats had been able to enter previously, with 1⁄4” hardware cloth and removed the Algerian ivy from our fence. All tree limbs have been cut back to at least 48” from our house. We pick up ripe fruit and nuts and feed our pets indoors. Uneaten pet food attracts rats and other wildlife. Occasionally we see some empty snail shells, thanks to the rats. Encourage your neighbors to take preventive steps, too.

We know roof rats are out there somewhere, but we rarely see them. With owls and other dangers outside, some of the released rats may not survive living wholly outdoors. A natural balance will evolve. Once you have rat-proofed your home and garden as much as possible, enjoy a peaceful co-existence.