Store pet food in sealed containers and do not leave it out at night. In some agricultural areas, roof rats cause significant losses of tree crops such as citrus and avocados and, to a lesser extent, walnuts, almonds, and other nuts. Roof rats have a strong tendency to avoid new objects in their environment and this neophobia can influence control efforts, for it may take several days before they will approach a bait station or trap. Tracking powders are used much less often for roof rats than for Norway rats because roof rats frequent overhead areas within buildings. It is unlikely, however, they will be any more effective for roof rats than for Norway rats. Grease marks are produced as the rodent travels along an edge, and the oils in their fur are deposited. You can also read about How much does rat control cost? Get rat extermination prices. Once you're satisfied that there is no more evidence of rats, and you are not trapping any new rats, you should clean the attic or whatever area they were living in, to remove the contamination and biohazard, and also to eliminate the rat scent, which will attract new rats to try to chew their way into the house in the future. Most rats in attics enter via roof entry points - although they can get into the building a variety of ways. They may live in trees, such as palm, or in attics, and climb down to a food source. A control operation, therefore, must reduce numbers to a very low level; otherwise, rats will not only reproduce rapidly, but often quickly exceed their former density for a short period of time.