To everyone having rat problems - the County of San Bernardino has some help for County residents (sorry L.A. residents): the Vector Control office operates in almost the whole county for unincorporated areas, and has an 800 number: 800-44-ABATE, and they can rent traps for a deposit which will be returned. I worked for them for over seven years. Most of what they do is education, not extermination, although an intervention-type trapping can happen if anyone has evidence they were bitten. They have leaflets that help direct the efforts to exclude rats and mice from houses, and how to tell the native Woodrats/Packrats from the non-native Roof Rats and Norway/Wharf Rats. (Quick note: a Norway rat usually has a tail shorter than the body. A Roof rat has a tail a good bit longer, but they are often shortened in injuries. A Woodrat is not as streamlined, and has larger ears, more cartoon-mouse-like, than the foreigners.) All three do carry disease. Incidentally, raccoons sometimes carry roundworms and spread the sticky, drought-resistant eggs in their feces.
The Agriculture office, if the number is still the same, can give information on pesticides, herbicides and their safe use, at 909-387-2105. They sell some gopher baits - general rodent baits also, if I remember correctly. They also rent gopher traps if anyone is so afflicted.
We used to call bird feeders "squirrel feeders" in Vector. If you keep food like seeds and nuts, they strongly recommend that you get METAL containers to keep out rats. Not feeding them, not watering them (fix drippy spigots), not sheltering them (clean up branches and refuse, keep wood off the ground in a rack) and doing strict exclusion (the earlier mention of steel or aluminum wool around pipes was perfect) is what the Vector office recommends. Rats can squeeze through a space that will allow their skulls to pass - about a quarter in most cases, but of course the youngsters are smaller. Woodrats are the main chewers of car wiring and other insulation - leave the hood up and it won't appear so safe a place to them. When I was on field trips in Geophysics, we had to lay our hundreds of feet of wire and sensors for seismic data out in the desert. We would inspect it before layout, and in almost every location, we would find that rabbits or rats had chewed up insulation in places, often as soon as a half-hour after it was on the ground. During the day. But seriously - rat chewing can start attic fires from exposed, shorted wiring. Take care of as much of the above precautions as you can, soon!
