The economic cost of removing the rats' natural predators was obvious. Hawks and owls, especially barn owls, are very effective at killing roof rats. Keeping the area around fruit trees open makes hunting easier for birds of prey. Many people believe that cats and dogs will keep rats out of their yards and fruit trees. But, because roof rats are so arboreal, they are usually able to get into attics and fruit trees without ever coming to the ground.
Rats quickly learn safe travel routes through yards to avoid terrestrial predators.
Cats will kill dispersing juvenile rats, but are rarely able to handle an adult roof rat within its own territory. Ultrasonic and Electromagnetic devices. Many claims are made about ultrasonic and electromagnetic devices' repelling rodents from buildings and yards. There is no evidence that these devices will or can drive rodents from their home range. There is evidence that ultrasonic devices can cause hearing loss in pets, especially dogs.