With cooler fall weather on its way—we hope!—perhaps with some much needed rain, many of the pests most common and dangerous in our Sacramento region begin to look for warm, snug places to ride out the winter. One of those most likely to move into your home or commercial building is the roof rat, otherwise known as Rattus rattus.

Neither Rattus rattus nor its relative, the Norway rat (Rattus norvegicus) are California natives; both originated in Asia and spread over most of the world centuries ago. The roof rat is smaller than its Norwegian relative, weighing 5 to 10 ounces, and is light gray or near-white in color, with a pointed snout, long ears and a long black tail the length of its body. The Norway rat larger, averaging 7 to 18 ounces, is darker in color, with short ears and tail.

Many of us think of rats as ground-dwelling creatures who scurry along alleys and under the bushes. But Rattus rattus is a climber, and your cozy, insulated attic looks mighty inviting as a place to nest and raise a litter of baby rats. The roofs of many buildings harbor handy entryways for these resourceful, smart and dangerous critters—unscreened ventilation vents, bent or torn flashing around chimneys and pipes, even missing or damaged shingles. Likewise, overhanging tree branches, pergolas and rain gutters offer rats an easy climb to gain access. One local homeowner we know saw a rat scurrying off her roof and over a backyard pergola around twilight one evening, only to lose sight of him in some tree branches. A flashlight revealed the rat’s destination: It was hanging upside down from a tree branch by its back claws, munching on a bird-food bell hung from the same branch.

Signs you have rats can include droppings near pet bowls, food containers or recycling bins; signs of digging near fences or around sheds; the sight of a rat traveling a utility line or tree branch at dusk; or even a rat carcass presented to you by the family pet. But often, particularly in the case of roof rats, you will hear them: scurrying or scuffling sounds, even squeaks or squeals, coming from overhead as you lay in bed late at night.

Disney cartoons aside, Rattus rattus is no laughing matter. Rats eat and contaminate human and animal food and are prodigious chewers fond of electrical wiring. They have been known to chew through phone wires and have been blamed for electrical fires. Roof rats carry many diseases dangerous to humans and pets, including typhus, leptospirosis, trichinosis, salmonella, ratbite fever and plague. Insulation material makes great nesting material, and they often leave it shredded and fouled with urine and feces.

Our pest control company has been assisting homeowners and business owners in eliminating rats for many years. But until recently, there was little we could do to mitigate the structural damage and unsanitary conditions left behind. That’s why we will be rolling out a brand new service, just in time for cool-weather rat season, that will include repair of any structural damage, removal of all contaminated insulation and rat waste, sanitization of the area, and replacement of insulation with a new, environmentally safe blown insulation product that will actually deter rats, insects and other pests from taking up residence in your attic in the future.

Our pest control technicians are already undergoing training in this new product line, and we’ll be telling you more about this new service soon. It is a service our customers have been requesting for some time, and we’re glad to be able to respond—not only in getting the rats out of our customers’ attics, but in returning their homes or commercial spaces to safe, sanitary and healthful conditions.

Although we’re enjoying (or cursing) unseasonably warm weather in Sacramento this fall, eventually cooler weather and rain (if we’re lucky) will set in for the winter. The cooler weather drives rats and mice indoors, looking for a warm, dry place to nest and raise their young. That’s why at this time of year calls from customers who suspect they have a rodent problem skyrocket.


Scientists characterize urban rodents—in particular the house mouse, Norway rat and roof rat, or black rat—as among the world’s most “successful” mammals, right up there with humans. As noted rodentologist Bobby Corrigan wrote recently for PCT Magazine, rodents are successful for six reasons: 1) they adapt easily to different types of structures and environments; 2) they reproduce quickly when conditions are good; 3) they can raise whole families in very small spaces; 4) they are secretive, elusive, active at night and alert to danger; 5) their body shapes and colors help them to hide; and 6) they are relatively smart. “Rats, for example, are considered to be highly intelligent,” Corrigan writes for PCT, “because research has proven they can learn and perform new tasks — an important asset when entering a new building or area for the first time.”

Corrigan cites several qualities of roof rats that have allowed them to adapt so successfully to civilization:

  • They navigate easily in high spaces above the sightline of humans and other natural predators, such as dogs and skunks.
  • They nest in difficult-to-access spaces—attics, ceiling spaces, dense foliage and treetops.
  • They range 500 feet or more to find food, often crossing multiple property lines. Where do you begin to treat?
  • They move in and out of homes and buildings, living indoors for a few weeks or months, then moving outdoors into trees or bushes.

But we know from experience, that colder, rainy weather tends to move them inside—often into your attic or crawlspace.

A rodent problem is not one that can be left untreated. Not only do rats and mice cause significant property damage—chewing through wires and cables, gnawing woodwork and other structures, creating fire hazards—they carry a number of diseases harmful to humans. If left to nest comfortably in your attic, basement storeroom, or backyard shed, a few rats will quickly become an army. According to the University of California-Davis Statewide Integrated Pest Management Program, “The average number of litters a female roof rat has per year depends on many factors, but generally it is 3 to 5 with 5 to 8 young in each litter.”

In order to effectively protect your home from rats or mice, the first step is to determine where the pests are most active and how they are getting in, and treat those areas first. (For a list of signs you have a rat or mouse infestation, check out this UC Davis Integrated Pest Management publication: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74106.html.) The second step is to clean and sanitize the area, removing rodent droppings and urine stains, repair any damage to wiring, wall board or woodwork, and replacing dirty and damaged insulation, preferably with an environmentally friendly insulation product containing a pest repellent. The final step is to rodent-proof your space so that you won’t have a repeat of the problem the next time the weather takes a turn.

Your licensed pest professional is trained to inspect your home or business; determine where the rats are coming in; where the rats are active now versus old, inactive sites; and how much damage has been done. Our company’s service also includes cleanup and sterilization, repairs, reinsulation with a “green” product that rats don’t like, and rat-proofing the area to prevent the critters from coming back in.

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