How can I tell if I have rats or mice in my NYC apartment?

Check the droppings and where the activity is. Mouse droppings are small (3–6 mm), dark, and pointed like grains of rice, usually concentrated in drawers, under sinks, and in cabinets; rat droppings are much larger (up to about 18 mm), thick, and blunt-ended, often scattered along basement walls, near trash, or in the yard. Mice nest inside walls and kitchens, while NYC's Norway rats live lower down — basements, cellars, and burrows near the foundation.

Are NYC rats Norway rats or roof rats?

Almost all of New York City's rats are Norway rats (also called brown rats or sewer rats), which dominate the city's rodent population per NYC Health. They are ground-dwellers that burrow and travel through sewers, basements, and connected yards. Roof rats, which prefer to climb and nest high, are rare in NYC.

Is a baby rat the same as a mouse?

No, and they're easy to confuse. A young rat has a noticeably large head and oversized feet relative to its body, and its body looks chunky; a fully grown mouse has a small, delicate head, very large ears for its size, and a slender body. If the animal looks 'out of proportion' with big feet and head, it's likely a juvenile rat — which means adult rats are nearby.

Do rats and mice carry disease in NYC?

Yes. NYC Health identifies rats as the most common source of leptospirosis, a bacterial infection spread through rat urine; the city recorded 24 human cases in 2023, its highest annual total, with six deaths over the prior 22 years. Both rats and mice can also spread Salmonella and contaminate food and surfaces, which is why droppings should be cleaned with a bleach solution rather than swept up dry.

Why do mice multiply so fast?

A female house mouse can produce five to ten litters a year with a gestation of about three weeks, and the young mature in weeks, so a few mice become an infestation quickly. That speed is one reason mouse problems in NYC apartments rebound fast after DIY traps — you have to remove the population and seal entry points before the next generation breeds.

Does it matter whether I have rats or mice when I call an exterminator?

Yes, the treatment is genuinely different. Mice need dime-sized gaps sealed, many trap and bait points placed close together inside kitchens and walls, and exploit their curiosity. Rats need quarter-sized and larger gaps sealed, burrow and exterior work, and a patient approach because they're neophobic — wary of new objects, so bait stations often need days before they'll feed.

What size hole can a rat or mouse get through?

A mouse can squeeze through a gap about a quarter inch wide — roughly the size of a dime or a pencil — while a rat can pass through a hole about the size of a quarter, around half an inch. That's why effective rodent-proofing in NYC means sealing even small gaps around pipes, vents, and door sweeps with steel wool, hardware cloth, or metal, not just foam or plastic that rodents chew through.

Rats vs Mice in NYC: How to Tell the Difference

Rat or mouse? Start with size and droppings

If you’ve spotted a rodent or its signs in your New York home or building, the fastest way to identify it is size and droppings. A house mouse is small — a body of about 3 to 4 inches with a thin tail roughly as long as its body, a pointed snout, and large ears for its head. A Norway rat is much bigger and heavier — a body of about 7 to 10 inches, small ears, a blunt nose, and a thick, scaly tail that is shorter than its body. Mouse droppings are tiny (3–6 mm), dark, and pointed at the ends like grains of rice. Rat droppings are far larger (up to about 18 mm), thick, and blunt or capsule-shaped at the ends. Get the ID right and everything else — trap placement, bait, gap-sealing — follows from it.

This matters in NYC more than almost anywhere. The city is estimated to host on the order of three million rats, and rat sightings drive tens of thousands of 311 complaints a year — more than 24,000 rodent-related complaints in just the first seven months of 2024 (CBS New York, NYC 311 data). Knowing which rodent you’re dealing with is the first real step toward getting rid of it. Our rat and mouse control service starts with exactly this identification, because a mouse job and a rat job look different from day one.

The species you actually have in New York

New York’s rodent picture is simpler than the general “rats vs mice” question suggests, because two species dominate.

Norway rat (brown rat / sewer rat)

Per NYC Health, the Norway rat — also called the brown rat or sewer rat — overwhelmingly dominates the city’s rat population. It is a ground-dweller. It burrows in soil near foundations, tree pits, and parks; it travels through sewers and connected basements; and it prefers the lower levels of buildings. In a brownstone or pre-war walk-up, that means the cellar, the ground-floor unit, the trash area, and the rear yard. Norway rats are strong, wary, and physically capable of gnawing through soft concrete, wood, and plastic.

House mouse

The house mouse is the other resident you’ll meet. Mice are agile climbers that nest inside the building envelope — in wall voids, behind cabinets, under appliances, and in stored clutter. They stay close to food and rarely travel more than 10 to 30 feet from the nest, which is why mouse droppings cluster in one or two rooms (typically the kitchen) rather than spreading across a property.

Roof rats — the climbing species common in warmer coastal cities — are rare in NYC, so if you have a rat in New York, assume Norway rat until proven otherwise.

Tell them apart by the evidence, not the glimpse

You’ll usually find the signs before you see the animal. Here’s how the clues differ.

Droppings

Mouse: 3–6 mm, dark, thin, pointed at both ends, scattered like rice in drawers, cabinets, and under sinks. A single mouse can leave 50–80 droppings a day, concentrated in its small home range.
Rat: up to about 18 mm, thick, blunt and capsule-shaped, often found along basement walls, near trash, in the yard, or by burrow openings.

Pointed and tiny means mouse; large and blunt means rat. This is the single most reliable indoor test.

Gnaw marks and damage

Mice leave small, clean gnaw marks and tend to nibble food packaging and paper. Rats leave larger, rougher gnawing and can damage baseboards, door corners, plastic pipe, and wiring. Rats also create visible burrows — two- to four-inch holes in soil, often along foundations and fence lines — which mice do not.

Grease marks and runways

Both species follow walls and leave greasy “rub marks” from oil in their fur, but rat rub marks are darker and lower (rats hug the floor along basement walls and pipe chases), while mouse smudges are fainter and higher up around cabinets and counters.

Sound and location

Scratching high in walls and ceilings or activity centered on a kitchen points to mice. Heavier scurrying low down, in the cellar, near the trash room, or in the back yard points to rats. NYC’s connected basements and shared trash areas are classic Norway-rat corridors — which is exactly why rat control in the city has to consider the whole building and block, not one apartment.

Behavior: why a rat is harder than a mouse

Identification isn’t just academic — the two species behave differently, and that changes how you trap them.

Mice are curious. They investigate new objects, including traps, within hours, so a mouse problem responds quickly to many trap and bait points placed close together (mice forage in a tight radius). The catch is reproduction: a female house mouse can have five to ten litters a year with a gestation of about three weeks (Orkin; Critter Control), so a handful of mice becomes an infestation fast, and DIY efforts rebound when the next generation breeds.

Rats are neophobic — genuinely wary of anything new in their environment. A fresh trap or bait station can sit untouched for days before a Norway rat will approach it. Rushing the job, or moving stations around, resets that caution and makes rats harder to catch. Rat control rewards patience, correct placement along established runways, and sealing the burrows and exterior gaps they use — work that goes beyond setting a few snap traps in the kitchen.

Health stakes: both matter, rats more so in NYC

Neither rodent is harmless. Both can spread Salmonella and contaminate food and surfaces, and both should have their droppings cleaned with a bleach solution (NYC Health and the CDC recommend one part bleach to ten parts water) rather than swept or vacuumed dry, which can aerosolize particles.

Rats carry the higher-profile NYC risk. NYC Health identifies rats as the most common source of leptospirosis, a bacterial infection spread through rat urine that can cause kidney and liver damage if untreated. The city reported 24 human cases in 2023 — its highest annual total on record — and six deaths over the previous 22 years (NYC Health). That rising trend is part of why the city created Rat Mitigation Zones and appointed a citywide “rat czar,” Kathleen Corradi, to coordinate rodent reduction.

Why treatment differs — and why ID comes first

Because the species behave and live differently, the fix differs too:

Gap size. Mice slip through a gap about a quarter inch wide — roughly a dime or pencil. Rats need a hole about the size of a quarter. Effective proofing seals both, but a mouse job means hunting down far smaller openings around pipes, vents, and door sweeps, sealed with steel wool, hardware cloth, or metal — not foam or plastic, which rodents chew through (CDC).
Where the work happens. Mice are an interior problem — walls, cabinets, kitchens. Norway rats are a ground and exterior problem — burrows, foundations, cellars, trash areas — so rat control extends to the yard and building envelope.
Trap and bait strategy. Mice get many stations placed close together, exploiting their curiosity. Rats get fewer, carefully placed stations on established runways, with patience for their neophobia.

This is why a correct ID is the first thing a professional confirms. Getting it wrong — treating a rat problem like a mouse problem — wastes time the population uses to grow. For the full removal playbook, see our guide to how to get rid of rats in NYC, and if you want to budget the work, rat exterminator cost in NYC breaks down what drives the price.

When to bring in a professional

If droppings appear in more than one room, you see burrows in the yard, activity is in a basement or multi-unit building, or you simply can’t tell which rodent you have, it’s time to call. In attached NYC buildings the source is often beyond your own unit — a neighbor’s wall, the shared cellar, or the block’s trash. Our rodent control team identifies the species, seals the entry points DIY misses, and coordinates building-wide treatment so the problem doesn’t just move next door.