Older houses are most vulnerable to rodents, but it's possible for them to crop up in just about any neighborhood. There are often large rodent populations in the city, but apartment owners typically rarely see them since their landlords will typically take care of building maintenance, including unwelcome visitors. Rodents are more problematic to the average suburban homeowner. Here are some signs to look for to see if rodents are living in or around your house:

Sounds:

Rats are typically active at night. You might hear such indicators as the patter of paws, squeaks, or climbing sounds in the walls. Mice may also emit a little whistle.

Odors:

Rats and mice lairs give off a noticeable pungent smell.

Droppings:

Look for rodent droppings near your food supplies, i.e. kitchen cupboards or countertops. A variety of sizes may indicate an established colony with both older and younger animals.

Gnawings:

Look for freshly gnawed wood, indicated by a paler coloring than the wood around it.

Excited Pets:

Dogs and cats are sensitive to the sounds and smells of rodents. If your pet frequently paws or sniffs at the wall or floor in one particular spot, especially near kitchen cabinets or storage areas, it may be an indicator of rats or mice.

Actual Sightings:

If you actually see a live rodent, it's a good indicator that you have a problem. Rats are secretive and are usually only out at night, so if you see one in the daytime, it probably means there are enough to have forced that individual out. Assume there are at least 10 more rats in the general area for every one you see. It is important to note that mice are naturally active during the day, so a mouse sighting doesn't necessarily mean there is a colony in your house.