Susan Buckley, RN, Director, Public Health
Ira Singh, MPH, Deputy Director
Donald I. Baird, MD, Health Officer

Division of Environmental Health


Date Released: 12/6/2004
Subject: Don't Let Rats Come Home for the Holidays
Contact: Brent Whitener, Vector Control Officer, Environmental Health Division
Phone: 707-445-6215 or 707-268-2203

We take such care in trimming trees, hanging stockings, and serving bountiful feasts for our guests that an unwanted visitor may escape our attention. Our local rat, called a Norway Rat, is looking to move in on the warm cozy setting your home provides. They begin the quest in your yard, finding pet food left outdoors at night, ground fruit near the apple tree, or birdseed scattered under the feeder by a fussy blue jay. This night
time forage puts them right next to your home.

Rats will dig a burrow to get in, but are generally lazy as a distant relative, and prefer to scurry through an opening in the foundation. Vents for the house’s foundation are covered with a wire mesh called hardware cloth, which can rust away or be cut by a plumber or cable installer. Rats enter through this opening and gain access to the sub-floor of the home. Next, they enter the walls where the water pipes supply the kitchen, laundry, or bathroom. Heat rises to the attic, and so do the rats. They chew their way up, following electrical wiring and causing damage that may result in a short circuit or fire. This upward movement is often when you hear them at night. Generally they leave the structure early in the morning to find water, then return the next evening.

Finding and sealing these entry points, called rodent proofing, is both easy and inexpensive. According to the Environmental Health Division, over 90% of rodent problems around the home can be solved immediately, simply by rodent proofing. Walk the perimeter of your home, pulling weeds away from vent screens and checking to see if they are intact. Make sure that the crawl space entry door is tight as well. Check where masonry and wood contact each other. Make sure the garage door lands tightly when closed and that the rubber gasket has not been chewed. Steel wool can block a hole temporarily, but the aerosol spray foam is not durable and should not be used to seal against rodents.

Try and avoid using poisons to control a rat problem, especially if the home is not rodent proof. There is usually no need for poisons or trapping if the home is sufficiently rodent proof. Winter weather and predators take a heavy toll on local rat populations as long as they cannot feed, hide, or breed within your home. For more information or help, call the Environmental Health Division at (707) 445-6215 or toll free, 800-963-9241.


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