Clean Them Out, Build Them Out, Don’t Use Rodenticides!
The most successful and long lasting form of rat control is to “build them out”. Seal cracks and openings in building foundations, and any openings for water pipes, electric wires, sewer pipes, drain spouts, and vents. No hole larger than ¼” should be left unsealed to exclude both rats and house mice. Make sure doors, windows and screens fit tightly. Their edges can be covered with sheet metal if gnawing is a problem. Install door sweeps at entry doors and garage doors - this will also help keep insects out. Course steel wool, wire screen , and lightweight sheet metal are excellent materials for plugging gaps and holes. Plastic and other woods can be chewed apart so they are not suitable.
About the Rats!
Roof rats are slightly smaller than Norway rats and are sometimes called black rats. They are a non-native rat prevalent in Sonoma County, and at times their populations are very high. Roof rats are agile climbers and nest in trees. They especially like palm trees (which are also favored by barn owls!), they live in ivy and ground cover, and can even live in trellises, greenhouses, overturned boats, woodpiles, compost bins, ivy covered fences, and in the upper parts of buildings, such as attics and walls. Their territory is 100 – 300 feet, in general. They are generally vegetarian, but will sometimes eat snails. Norway rats are the gray rats seen in sewers and in buildings. They will eat just about any type of food, but prefer meats and fresh grains. Any food left outdoors will attract rats, including pet foods, fallen seeds from bird feeders. Roof rats are also commonly found around creeks and streams. Both these rats are non-native, introduced species. We also have native rats, such as the Wood Rat, which generally avoid human habitations and are an integral part of the native ecosystem. Wood Rats (also known as Pack Rats) should not be persecuted.
Cleaning is the best Policy
Clean up under trees and bird feeders. If the rat problem is really bad, stop bird feeding for a month or so – don’t’ worry, birds are used to their food sources changing and will move on and find food elsewhere. Trim all tree branches to at least three feed away from rooftops and decks – this is good fire control as well. Roof rats can also reach buildings along utility wires. Eliminate vines growing on the buildings as well. It may be harder to find the openings where the roof rats enter buildings because they will be high up on the building.
To seal openings use a product such as Stuf-fit Copper Wool Mesh – rodents cannot chew through it. Regular wire or chicken wire will not work. Seal all openings of ½” diameter or greater (holes larger than a dime). Mice can enter holes as small as ¼”. Cover garbage cans, compost bins, etc. tightly.
Rats have a keen sense of smell and can find food anywhere. The most successful way to keep rats out of your home or other buildings is by exclusion and removing food sources. Poisons and traps are quick fixes that will have to be done continuously. Exclusion is more work but it’s a permanent solution. Poison can also cause the rats to die in walls resulting in terrible smells. Seal any openings where pipes or wires enter the building, including garages. Use tight fitting grates on floor drains and sewer pipes.
Once you have sealed all openings, use lethal traps to dispatch any rats that are trapped inside the house. Or use live traps to catch the rats and release them outdoors. Recommended baits include Slim Jims, peanut butter or fish-flavored cat food. An important note about rats: they are suspicious of new things in their environment. Therefore, if traps are being used it is recommended to bait but not set the traps a few times. If traps have not caught anything after two weeks, put them away. Please do not ever use sticky glue traps, especially outdoors. They are extremely cruel and used in the wrong places can trap non-target animals such as birds and baby mammals.
In conclusion, rats can never be completely eradicated from our environment, and indeed if they were, entire populations of predators, such as birds of prey, bobcats, coyotes, etc. would be gravely affected. Without the natural predators, populations of rats, mice, gophers, and moles would explode and defeat our best efforts at control. We must strive not to inadvertently poison our beneficial predators, and our household pets, by using rat poisons, especially outdoors. Any use of poison indoors presents a grave risk to children as well.