What are the signs of rats nesting indoors during winter?

The scale difference between rat and mouse sign is the single most reliable way to tell them apart without seeing the animal. Rat droppings run roughly 1/2 to 3/4 inch with blunt, rounded ends, compared to a mouse's rice-grain-sized, pointed droppings. Gnaw damage follows the same pattern -- NC State Extension documents rats chewing through a plastic storage container, a scale of damage well beyond what a mouse typically produces.

The practical value here is that size alone lets a homeowner make a reasonably confident call without needing to see the animal directly, which matters because rats are notably better than mice at avoiding detection in the first place.

This is the detail that generic rodent-sign advice usually flattens, and it changes where you should actually look. Norway rats stay low -- basements, crawl spaces, and ground burrows roughly 2 to 3 inches wide, per NC State and University of Arizona Extension. Roof rats do the opposite, staying high in attics, soffits, and upper structures.

That means a thorough winter check genuinely needs two separate inspection zones, not one. Checking only the basement misses roof rats entirely, and checking only the attic misses Norway rats. The nest material and location together are usually enough to tell you which species you're dealing with, which matters because their behavior, and the fixes that follow, differ.

NC State Extension notes rats are neophobic and "fairly adept at going unnoticed," which means the absence of a sighting tells you almost nothing about whether rats are present, and a single confirmed sign -- one dropping, one gnaw mark -- tells you almost nothing about how many there are. This page's average search position, historically very low even though the question is a common one, is itself evidence that generic answers haven't served this query well; the fix is the specificity above, not a vaguer answer.

What a homeowner can reasonably conclude: multiple signs across more than one visit, in a consistent location, indicate an established rather than a passing presence. A single find is worth investigating further, not treated as a confirmed infestation on its own.