The timing test
This is the big one. Squirrels are diurnal — active during the day. If the scampering starts after sunrise, peaks mid-morning, quiets midday, and picks up again before sunset, you're hearing squirrels. Rats are nocturnal — if the activity starts after dark and runs through the night, think rats. Raccoons are also nocturnal but much heavier and louder. Time of day eliminates half the suspects immediately.
The sound test
Squirrels sound like quick, light scampering — running back and forth, often in bursts, sometimes with rolling sounds (a stored nut escaping). You'll hear them move across the ceiling in a clear path. Rats make lighter scratching, gnawing, and scurrying sounds — less running, more nibbling and shuffling, often in walls as well as the attic. Squirrel gnawing is louder and more deliberate; they're working on wood or wiring.
The evidence test
If you can safely check the attic access (don't go crawling around), look for droppings. Squirrel droppings are larger — about the size of a bean, often in clusters near entry points. Rat droppings are smaller, like dark grains of rice, scattered along beams and runs. Entry holes differ too: squirrels chew obvious holes in wood; rats use smaller gaps and leave greasy rub marks.
Why the ID changes the job
Squirrels get one-way doors and entry sealing — they're territorial and don't live in large colonies. Rats need a trapping-plus-exclusion program — where there's one, there are more, and they breed fast. Treating a rat problem like a squirrel problem (or vice versa) wastes weeks. When you Send the form, tell us when you hear the noise and what it sounds like — we'll usually know before we arrive. Squirrel removal and rat & mouse exclusion cover each process.