Rats are hardy creatures and adapt well to most environments. Unfortunately, buildings and homes are ideal sources of food and nesting for many rat populations. You might have rats in your house if you hear scratching and squeaking sounds at night, or notice feces in the home. It's important to take care of a rat problem promptly because they are prolific breeders. One female can have up to 18 litters of seven or more rats in a year.
Check along baseboards, in cupboards and behind furniture for feces. Rats often head for the easiest food source, and rat droppings will indicate frequently traveled routes. Rat droppings are approximately 1/4 inch in length and pellet-shaped. Fresh droppings are dark, while old droppings are gray and crumbly.
Inspect your baseboards and lower walls for dark rub marks. Rats travel close to walls and leave dark, greasy spots on corners and baseboards along their paths. The marks appear when the oil from the rat's fur rubs off.
Look for damaged wood and holes in walls or ceilings. Rats chew on hard surfaces to keep their teeth sharp, and they will chew a hole through a wall to make a shorter route or to get to food. Wood chips and gnawed spots on wood indicate popular rat areas.
Sprinkle talcum powder or flour where you find evidence of rats. Also place the powder along walls and on counters. Rats are more active at night, so leave the powder in place overnight and check for fresh tracks in the morning. It may take a few days for tracks to appear if the powder is on a rarely traveled path.
Investigate popular nesting sites. Rats like dark places, so garages, basements and attics are good places to check for infestation. Rats make nests from paper, cloth, plant materials and any other easily shredded items it might find. The nest looks like a small ball approximately 4 inches in diameter. If you find caches of food in the area where you find a nest, it's a good bet you have an active rat population.
Don't neglect the outside of your home. Not all rats live indoors. Some types live outside in dense vegetation or under woodpiles. Check around the foundation of your house for fresh tracks in the dirt. Even if these rats live outside your home, they may travel inside for food.