Hearing scratching, rustling, or light running overhead is unsettling — especially at night. In South Florida, those attic noises are most often caused by mice or rats. Knowing which one you’re dealing with matters, because the trapping, exclusion, and cleanup plans are different for each.

1) Droppings: the quickest way to tell

If it’s safe to do so, a quick visual check of accessible areas (like attic entry points, tops of water heaters, or around stored items) can tell you a lot.

• Mouse droppings: Small, like black grains of rice; pointed ends; usually scattered.
• Rat droppings: Larger, up to 1/2–3/4 inch; blunt or sausage-shaped; often found in more concentrated areas.

Fresh droppings are dark and slightly shiny. Older ones look dull and dry. Either way, avoid sweeping or vacuuming them — that can aerosolize particles. Proper cleanup means masks, gloves, and disinfection.

2) Sounds & timing: what you hear matters

Rodent species tend to move differently and at different times:

• Mice: Lighter, skittering sounds; quick, random movement; often heard in walls and lower cabinetry as well as ceilings.
• Rats: Heavier, slower movement; distinct thumps or dragging sounds; more likely to use the same established travel routes repeatedly.

Most rodent activity spikes from dusk through the early morning hours. Hearing noise during the day can indicate a heavier infestation or disturbed nesting sites.

3) Gnaw marks & damage

Both mice and rats have to gnaw to keep their teeth from overgrowing, but the scale of damage is different.

• Mice: Small gnaw marks on pantry items, pet food bags, cardboard, and soft plastics.
• Rats: More aggressive damage — chewed wood, larger holes, compromised ductwork, and gnawing around entry points or rooflines.

Any visible wiring damage should be treated as a priority risk, as rodents can increase the chances of electrical issues.

4) Pathways, rub marks & entry points

Rats often use the same runways, leaving behind rub marks — dark, greasy smudges where their fur repeatedly brushes surfaces.

• Mice: More likely to squeeze through very small gaps (as little as 1/4 inch) around utility lines, gaps in framing, and under doors.
• Rats: Often enter from rooflines, soffits, attic vents, or construction gaps. Openings the size of a quarter can be enough.

Once inside, both species can follow plumbing and electrical chases to move between floors and rooms.

5) Why “just setting a few traps” usually isn’t enough

Traps alone don’t solve how rodents are getting in. Even if a few are caught, open entry points invite new activity from the surrounding population.

A complete rodent program should include:

• Detailed inspection to identify access points and conducive conditions
• Strategic trapping and monitoring — not just random placement
• Sealing and reinforcing entry points with proper materials
• Sanitation and, when needed, attic or area cleanup