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 25,000 droppings in a year.

Rats transmit Murine typhus fever, rat bite fever, salmonellosis 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.

Successful control depends on proper identification of the different species. Norway and roof rats differ in size, habits, food preferences and regions. Techniques that eliminate one species may not eliminate the other.

Many times roof rats live in the upper stories of buildings, while Norway rats occupy the basement and first floor of the same building.

Rats visit fewer food sites than mice. However, rats eat much more at each site than mice.

Rats constantly leave droppings. Fresh droppings are dark in color and soft in texture, but after three days they harden and lose the dark color.

Rats always travel the same runways and leave "smudge marks" - a buildup of dirt and oil from their fur - along walls, pipes, gnawed openings and beams and rafters.

Rats keep indoor runways, or well-used paths free of cobwebs, debris and dust. Outside, runways appear as narrow paths through vegetation.

Rats make sounds when climbing, clawing and moving.

Footprints and tail drags can be seen in dusty locations. Use tracking dusts such as talcum or flour to determine if rodents are frequenting certain areas.

Gnaw marks are a sure sign of rats. On wood, the older the gnawing, the darker the wood.

If dogs or cats unexplainably get excited, rats are probably moving about in wall voids or ceilings.