Roof Rats in Attics

Getting Rid of Roof Rats in Your Attic or Crawlspace

About Roof Rats

Wild rats live off man and give nothing beneficial in return. Rats spread disease, damage structures and contaminate food and feed. Rats damage one-fifth of the world's food crop each year. The real damage is in contamination. One pair of rats shed more than one million body hairs each year and a single rat leaves approximately 25,000 droppings in a year

Rats transmit Murine typhus fever, rat bite fever, salmonellas or bacterial food poisoning, Weils disease or leptospirosis and trichinosis, melioidosid, brucellosis, tuberculosis, pasteurellosis, rickettsial diseases, and viral diseases such as foot-and-mouth disease. Norway rats can also carry the rabies virus.

The Norway rat and the Roof rat are not native North American species. They traveled to the new world with the first explorers. The two species quickly invaded the continent because of their adaptability and fertility. Norway rats are found throughout the United States, while roof rats primarily inhabit southeastern, Gulf Coast and southwestern states.

Rats memorize their environment by body and muscle movement alone. They become so engrained by body movements that when objects are removed from their territory, rats will continue to move around them as if the objects where still there.

Biology

Roof rats reach sexual maturity in 2-5 months. Pregnancy lasts an average of 22 days. The young are blind and naked at birth, with hair appearing in about 7 days and eyes opening in 12-14 days. They are weaned at about 3-4 weeks. The average number of litters is 4-6 per year, each containing an average of 6-8 young. Adults on an average live 9-12 months.

They have rather poor vision and are color blind, but their senses of hearing, smell, touch, and taste are keenly developed. Touch is via their vibrissae or long whiskers. They are good runners, excellent climbers and jumpers, and good swimmers.

A roof rat requires 1/2-1 oz (14-28 g) of food and 1 oz (30 ml) of water each day, with the water often coming from its food. This results in about 30-180 droppings and 1/2 oz/3 teaspoons (16 cc) of urine per day.

Historically, bubonic plague has been associated with the roof rat and its fleas, which move from infested rats to man. Fortunately, plague has not been found in rats in the United States for many years. Other transmitted disease organisms include murine typhus via fleas (also probably via droppings and urine), infectious jaundice/ rat-bite fever via bites, trichinosis via undercooked pork, and food poisoning or Salmonellas via droppings. Another problem is tropical rat mite dermatitis, which is caused by these mites when they feed on humans.

Habits

Roof rats are primarily nocturnal in habit and they are very cautious. Although they constantly explore their surroundings, they shy away from new objects and changes. Roof rats prefer to nest in the upper parts of structures but may be found under buildings as well as occasionally in basements and sewers. Outdoors, they prefer to nest in higher places such as in trees but may occasionally be found in burrows in or under vegetation around the structure. These are social animals but less so than Norway rats. Several nests may be located within a given area. An opening of greater than 1/2" is required for entry of an adult rodent into buildings.

Although they will eat practically anything, roof rats prefer fruits, vegetables, and cereals. If the eaten food material proves disagreeable, they are quick to develop food/bait shyness. Once they find an acceptable/preferred food, rats tend to eat their fill at one sitting/place and will return time after time.

Once established indoors, roof rats tend to follow the same route or pathway between their harborage and food and/or water sources. Runways along vertical surfaces will usually include dark rub or swing marks on the vertical surface where their fur makes contact. Their runways will be free of debris, and outdoors, the grass will be worn away to the bare soil.