The Roof Rat (Rattus rattus) is the major problem species in the urban areas of Kern County. It is also known as the Tree Rat, Fruit Rat or Black Rat. This agile rat is slender with the tail longer than the head and body combined. Roof Rats frequently enter buildings and are also excellent climbers who can move about neighborhoods by using utility lines and fences as runways.

The Roof Rat prefers to feed on fruit often grown in residential backyards such as oranges, grapefruit, lemons, tomatoes, apricots, and also nuts such as walnuts, pecans, and almonds. Rats will also feed on pet food, snails, bird seeds, chicken feed, and grains.

Roof Rats will nest in large overgrown ivy patches, piles of lumber and firewood, untrimmed palm trees, and yucca plants. They may also be found nesting in old furniture, abandoned cars, sheds, and inside buildings. Rat survival and prosperity are dependent upon the existence of three basic environmental conditions: food, water, and suitable harborage. Sanitation, good housekeeping, and harborage removal are the first steps in a successful rat control program.