Fire and cold weather bring unwanted rat visitors indoors

As the cool weather approaches, so does the likelihood that rodents will be seeking warm nesting sites in the attics, garages and foundations of our homes and commercial buildings. In fact, some of our customers who live near wildfire areas have experienced an unseasonably early influx of these critters, driven from woods and fields by the smoke and flames.

The two most common rodent invaders are mice and rats.

In our region of Central-Northern California, the two most common species of pest rats are the roof rat (Rattus rattus) and the Norway rat (Rattus norvegicus), neither of which are native to California but originated in the Far East and spread across the globe centuries ago. The roof rat is the smaller of the two, averaging 5 to 10 ounces in weight, gray to white in color, with a pointed snout, long ears and a black tail as long as its body. The Norway rat is stockier, weighing 7 to 18 ounces, grayish in color, and with shorter ears and tail than the roof rat.

The roof rat is a good climber, nests in trees and dense shrubs, and may take up housekeeping in your attic, the space above dropped ceilings or even in high cabinets. The Norway rat is a burrower and indoors usually sticks to basements or ground floor spaces. You may spot its nest lined with shredded paper, fabric or other fibrous materials.

Although both these types of rat are common in our region, and highly adapted to residential neighborhoods and urban environs, our Earth Guard customers complain most frequently of the roof rat.

Sometimes depicted as funny and cute in popular media such as the Disney-Pixar movie “Ratatouille,” in fact Rattus rattus and Rattus norvegicus pose serious health and safety problems for home- and business owners. Rats eat and contaminate human and animal food and whatever container or packaging it is stored in; they gnaw on and ruin wooden doors and cabinets, chew through electrical wires and shred insulation to use for their nests. One of our customers recently had to place a service call to her security alarm company when a sensor stopped working; the mystified technician finally found a place in the attic where a rat had chewed through the alarm system wiring.

Rats also carry diseases such as murine typhus, leptospirosis, trichinosis, salmonellosis (food poisoning), ratbite fever and even plague that can be transmitted to humans and other animals.

The first signs of a rat infestation may appear in your yard or garden before the critters have moved indoors. Once they move into your yard, they will eventually move inside, so it’s preferable to catch them early. Common signs of rat activity outdoors include:
• Droppings near pet food containers or dishes or recycling bins;
• Nest materials in wood piles or brush piles;
• Burrows near compost heaps or garbage containers;
• Signs of digging under fences, sheds or doghouses;
• The sight of a rat traveling utility lines or fence tops at dusk;
• Rat carcasses in your outdoor pool or hot tub or dragged to the door by your family dog or cat.

Indoors, you may hear noises coming from your attic, especially at dusk or dawn, or discover a nest inside drawers or behind boxes in your garage, or you may see smudges along walls, pipes or rafters.

Homeowners and business owners can take some common-sense measures to prevent rat infestations, including keeping pet food containers and garbage containers tightly sealed and the areas around them picked up and clean.

Bird feeders also are attractive to rats. Another of our customers, who had multiple bird feeders in her backyard, noticed that the seed-covered bird bell she hung in one corner of her yard would repeatedly disappear almost overnight. She would replace it, and by the next morning, it would be eaten down almost to the plastic hanger. Hungry birds, she thought. The one evening, she happened to be looking out the back door just as dark was settling in and heard a rustling in the leaves above the bird bell. Grabbing a flashlight, she quietly walked over to investigate. The beam of the flashlight revealed an acrobatic roof rat, hanging upside down from the branch, nibbling away.

Storing wood off the ground and eliminating clutter and debris from around building foundations also will discourage rat activity. Roof rats, such as the acrobat caught eating our customer’s bird bell, may use overhanging tree branches, pergolas or dense shrubbery such as star jasmine or ivy as a highway to your roof, where they may find entry to your attic around eaves, pipes or chimney flashing. Trimming trees to leave 2 feet or more between plants and between branches and roof helps discourage these travels. Sealing, screening or plugging openings around wiring conduit or pipes with steel wool or sheet metal, both around your roofline and at foundation level, also are effective at keeping rats out.

Once rats have moved in to your home or place of business, the best way to eliminate them is with the traditional snap traps. A major infestation may require the use of poison bait, which should only be administered by a trained pest control professional. Although customers sometimes request it, the use of live traps is not a good idea. Because the rats are not native to our environment, they cannot be released outdoors, where they pose a danger to humans, pets and property and—because they are an invasive species—to the native ecosystem. In some areas, rats have been known to decimate wild bird populations. Live traps also accumulate bodily waste from the rodents, creating a health hazard for our pest control technicians.

For more information about rats and other environmental and pest control issues affecting Sacramento-area homes and businesses, visit (Norway rat photo credit: National Pest Management Assoc. Inc.)

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October 5, 2009 | 8:54 PM

Thanks for this article. My attic is a popular hangout for roof rats. I was thinking cat access might be helpful since I have three cats.

October 6, 2009 | 6:46 AM

Full disclosure: “Earth Guard Pest Management Services is a family-owned, independent company serving the Greater Sacramento, California, area and surrounding communities. Earth Guard offers a full range of professional pest management services, including residential and commercial pest control, “green” pest control solutions, home and building inspections; termite and WDO (wood-destroying organisms) inspections, repairs and reports, pre-construction termite treatment, and more. We offer free estimates, senior discounts and 100% satisfaction guaranteed! Check us out at”

October 6, 2009 | 11:13 AM

Picton, in the central city street gutters are also a favorite place for rats, mice, cockroaches and other vermin to thrive. I’ve see all in my many walks as these creatures munch on careless and thoughtless people’s discarded partially eaten sandwiches, fast food leftovers, candy, partially empty sugared coffee cups, soft drink and beer bottles (yes, they like beer and soft drinks), discarded plastic pre-packaged containers from convenience markets, oranges that drop from the ornamental orange trees as well as grapefruits on the ground, etc.

Well fed cats and dogs are not too much help but instead are often intimidated by large rats as I saw one day. A cat curiously extended its paw as if to test what that “animal” was in the gutter eating a walnut. The rat dropped its walnut and jumped on top of the gutter and stood on its hind legs in an attack mode and the timid cat ran.

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