By Scott Dideon, MS BCE Urban Entomologist, Green City Pest Control


Compared to the city rat (the Norway Rat), the Roof Rat is a smaller, more agile rodent that was introduced into the Seattle area around the 1940’s. In the past 15 years, the Roof Rat population has exploded throughout Western Washington and has  now become a real threat to both our homes and the environment.

The Roof RatRoof Rats get their name “Roof” from about a hundred years ago when they would live in the roofs of homes in California and would feed off oranges and other fruit trees nearby. Recently Roof Rats have discovered that the Pacific Northwest also has plenty of other great food  resources (apples, blackberries…) and that they can easily live in the insulation of our attics and crawlspaces in our homes.

The Roof Rat is an invasive rodent that originally comes from the jungles of Asia, and as such loves to climb and live in the vegetation around our homes and any nearby greenspaces. If there are trees or vegetation touching the side of the home, then the rats will quickly access the roof and chew their way into the insulation. In the crawlspaces, once they find a way in, they will run underneath the flooring and within a year or two will completely destroy the insulation. Properly replacing the insulation in a crawlspace or attic can easily cost between $5000 to $7000. So, addressing pest control issues preventatively can be a more  cost-effective approach for a homeowner than ignoring it and hoping it goes away.

Roof rats have spread throughout the Seattle area quickly because they reproduce exceptionally fast. After the juvenile rats are forced out of the nest, they scatter throughout the neighborhood looking for a new home or crawlspace they can get into. If a home has a current rodent baiting program, then the rats encounter the bait stations, eat the rodenticide and die within a few days before they can find a way into the home.

Roof Rat peeking through holeOur regular pest control programs now also include a baiting program for moles. That is in part because rats and mice have learned how to follow the mole tunnels into the crawlspaces of our homes even if other routes had been sealed up. Baiting for the moles reduces the chance for tunnels to be built into the crawlspace and keep the rat and mouse population down so the home is better protected.

Unfortunately, because Roof Rats are invasive and don’t have enough predators in our area, they will continue to become an issue for homeowners that don’t have a regular pest control program. You can contact our office at  425-413-9700 to ask any questions about how to prevent these little critters from moving into your home this winter.

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