Rat or Mouse? How to Tell What's in Your Home

San Francisco's health department lists three rodents that cause trouble indoors: the Norway rat, the roof rat and the house mouse. Each one lives differently, so the fix is different too. You usually won't get a good look at the animal, but you can read the clues.

Norway Rat

The big one. UC IPM puts adults at about 7 to 18 ounces, stocky, with a blunt nose and small ears. It burrows along foundations, under woodpiles and garbage and around gardens, and indoors it mostly stays in basements and ground floors. The health department also calls it the brown, wharf or sewer rat.

• Burrows along foundations and under bins
• Signs in the garage, basement and ground floor
• Gnawing at the bottom of doors

Roof Rat

Lighter, at roughly 5 to 10 ounces. Its nose is pointed, its ears are large, and its tail runs longer than the rest of it. It nests up high in ivy, shrubs, trees, attics and wall voids. UC IPM notes people often see it running along utility lines or fence tops at night.

• Noise in the ceiling or upper walls
• Chewed citrus or avocados still on the tree
• Rats on fence tops and wires at night

House Mouse

Small, gray-brown and quick. The health department says it can settle into homes and offices for the long term and live a long time on cereal and scraps. Mice stay close to where they nest, so signs tend to cluster in one kitchen or one closet.

• Tiny droppings in drawers and cabinets
• Chewed food boxes
• Light scratching low in the walls

Still Not Sure?

A rodent inspection will tell you. Then see rat control, roof rat control or mouse control.

See also: Rat Control, Roof Rat Control, Mouse Control