Straight answers from a licensed New York exterminator and Associate Certified Entomologist (ACE) — serving all five boroughs, in English and Spanish.
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Quick answer: The clearest signs of mice or rats are droppings, gnaw marks, greasy “rub” marks along walls, scratching or scurrying sounds at night, shredded-material nests, a musky ammonia odor, and chewed food packaging. Mouse droppings are small (3–6 mm) with pointed ends; rat droppings are larger (12–18 mm). Spotting these early — common in NYC apartments and brownstones — keeps the problem small.
The most common signs of a rodent problem
- Droppings: the #1 sign. Mouse droppings look like dark grains of rice; rat droppings are bigger and capsule-shaped. Fresh droppings are dark and soft; old ones are gray and crumbly. (See what mouse droppings look like.)
- Gnaw marks: rodents chew constantly — look for damage on food packaging, baseboards, wires, and plastic.
- Rub / grease marks: dark smudges along walls, baseboards, and pipe runs where oily fur rubs as they travel the same routes.
- Noises at night: scratching, gnawing, or scurrying in walls, ceilings, and under cabinets after dark.
- Nests: shredded paper, insulation, or fabric tucked behind appliances, in cabinets, or in storage.
- Odor: a musky, ammonia-like smell from urine, stronger with a larger or longer-running infestation.
Mice vs. rats: quick tells
Mice are small (7–10 cm body) with large ears and thin tails, leave many tiny droppings, and are curious. Rats are much larger (up to 25 cm body), more cautious, leave fewer but bigger droppings, and cause heavier gnaw damage. NYC’s most common rat is the Norway rat (burrows, basements, yards), while house mice dominate apartments.
Why early detection matters in NYC
Rodents reproduce quickly, chew wiring (a fire risk), and contaminate food and surfaces. In multi-unit buildings they travel through walls, risers, and shared spaces, so a few signs can mean a building-level issue. NYC also designates Rat Mitigation Zones with specific requirements — see our rat mitigation zone guide.
Seeing the signs? The fix isn’t just trapping — it’s exclusion (sealing entry points) plus removal. New York Exterminating’s NYC rodent control & exclusion is led by an Associate Certified Entomologist (ACE). Call (347) 210-4646.
A Brooklyn-based, NYSDEC-registered company (Reg. #15140) led by Jorge Bedoya, an Associate Certified Entomologist (ACE). For mice and rats, NYE provides rodent exclusion that seals the entry points, not just trapping. ACE-led work comes with a client portal of service reports and photos, fully bilingual service, and no long-term contract.
Signs of Mice & Rats — FAQ
What is the first sign of mice or rats?
Usually droppings, found along walls, in cabinets, or near food. Nighttime scratching sounds and gnaw marks often appear around the same time.
How do I know if it’s mice or rats?
Dropping size is the easiest tell: small rice-sized droppings mean mice; larger capsule-shaped droppings mean rats. Rats also cause heavier gnaw damage and use larger entry holes.
Do rodents make noise at night?
Yes — they’re most active after dark, so scratching, gnawing, and scurrying in walls or ceilings at night is a common early clue.
Can I get rid of rodents myself?
Traps can catch a few, but lasting control requires sealing the entry points they use to get in and back in — which is the part most DIY efforts miss, especially in connected NYC buildings.
