Identification Guide · Updated May 2026

10 signs you have rats in your house — what NJ homeowners need to look for

If you suspect rats but aren't sure — that ambiguous scratching sound at 2am, the strange smell in the basement, the chewed corner of a cardboard box — this guide covers exactly what to look for. Each sign below includes what's distinctive about it (versus mice, squirrels, or other pests), where to look in a typical NJ home, and how seriously to take it.

Important context: a single rat is rare. Norway rats — by far the most common rat species in New Jersey — are colonial, meaning if you have one, you almost certainly have a family. By the time most homeowners notice the first sign, the population has typically been established for at least 4-6 weeks.

Sign #1: Capsule-shaped droppings

Rat droppings are the most reliable single indicator of an active infestation. They're roughly the size of a large raisin (½ to ¾ inch), dark brown to black, with rounded or slightly pointed ends. Fresh droppings are soft and dark; older droppings dry to gray and crumble.

Where to look in NJ homes: along basement walls, behind appliances (refrigerator, dishwasher, washer/dryer), in cabinet corners, attic insulation, garage corners, and along the perimeter of pantry shelves.

What it rules out: Mouse droppings are much smaller (rice-grain size, about ⅛ inch). Squirrel droppings are similar to rats but typically lighter brown and found in attics rather than basements.

Sign #2: Greasy rub marks along baseboards and beams

Rats follow the same paths through a home night after night, and the oils in their fur leave dark smudges on surfaces they brush against. These rub marks appear as thin (1-2 inch wide) greasy streaks along walls, baseboards, ceiling joists, and the edges of entry holes. Fresh marks are dark and slightly glossy; old marks dry to a dull dark stain.

This is one of the most under-noticed rat signs because most homeowners don't look for it. If you find a smudge along a baseboard you can't otherwise explain, look closer.

Sign #3: Heavy nighttime scratching, scurrying, or thumping

Rats are mostly nocturnal and significantly heavier than mice — heavy enough that you can hear individual footsteps and tail-drag sounds in walls and ceilings. The distinctive rat sound profile:

• Heavier and slower than mouse activity (which sounds like fast pitter-patter)
• Often includes thumping when they jump or fall
• Most active in the first 2-3 hours after dark and the last 1-2 hours before dawn
• Concentrated in walls, basement ceilings, and crawlspaces — not usually attics (squirrels are more attic-focused)

If you're hearing daytime activity, the population is large enough that nighttime feeding alone isn't sufficient — and that's a sign to call a NJ DEP licensed exterminator immediately.

Sign #4: Gnaw damage on wood, plastic, or wiring

Rats chew constantly to wear down their teeth, which grow throughout their lifetime. Common targets in NJ homes:

• Wooden door frames, sill plates, and structural lumber (especially in basements)
• Plastic food packaging, plastic storage bins, and PVC plumbing
• Electrical wiring — both indoor (a real fire hazard) and outdoor utility lines
• Insulation, fabric, paper, and cardboard for nesting material

Fresh gnaw marks are pale and angular with visible tooth scoring. Old gnaw damage darkens with age.

Sign #5: Musky, ammonia-like odor

Established rat populations produce a distinctive smell — a combination of urine, droppings, and the musk gland scent that rats use to mark territory. The smell is most noticeable in enclosed spaces (basements, attics, crawl spaces, inside walls) and can become overpowering when a rat dies in an inaccessible spot.

NJ homeowners often describe the smell as "ammonia-like," "musty," or "like a hamster cage that needs cleaning." If your basement smells off and you can't find the source, rats are a leading possibility.

Sign #6: Burrows and ground holes near foundation

Norway rats are excellent burrowers. They dig 2-4 inch holes near foundations, under sheds, along fence lines, and in flowerbeds. Active burrows have:

• A smooth, polished entrance (rats use the burrow daily)
• Loose dirt or debris pushed out of the entrance
• Sometimes a worn dirt path leading to the hole

This is a sign rats are accessing your property from outside — and likely have multiple entry points into the building itself. Burrows are particularly common in NJ neighborhoods near parks, river corridors, and commercial dumpster areas (Paterson, Newark, Clifton, Jersey City).

Sign #7: Pet behavior changes

Dogs and cats often detect rats long before humans do. Watch for:

• Sustained fixation on a particular wall, floor area, or appliance
• Sudden barking or growling at apparently empty spaces, especially at night
• Sniffing intensely along baseboards or around basement entries
• Cats bringing dead rodents to you — usually meaning more are still alive in the home

If your pet's behavior changes suddenly without an obvious explanation, it's worth investigating.

Sign #8: Nesting material in unexpected places

Rats build nests using shredded paper, fabric, insulation, and any soft material they can carry. You'll find nest material:

• Tucked behind appliances or in the cavity beneath them
• In the back of basement storage (boxes, old clothes, garage items)
• Inside furniture stored in basements or attics
• In crawl spaces, with shredded fiberglass insulation pulled into compact piles

Sign #9: Strange tracks in dust or flour

If you suspect rats but want confirmation, you can sprinkle a thin layer of flour, talc, or baby powder along suspected travel routes overnight. Rat tracks are distinctive: 4-toed front prints, 5-toed back prints, with a tail drag mark between them. Mice leave similar but smaller tracks without the drag mark.

Sign #10: Daytime sightings

Seeing a rat during daylight hours is the most serious sign on this list. Rats prefer to operate at night, and daytime activity usually means one of three things:

1. The population has grown beyond what nighttime feeding can sustain
2. The rat is sick, injured, or dying (often from rodenticide poisoning)
3. Severe overcrowding is forcing rats out of their established harborage

Any of these scenarios means the infestation is significant and shouldn't be DIY'd. Call a NJ DEP licensed rat exterminator immediately.

What NOT to do if you find these signs

Common mistakes NJ homeowners make:

• Don't immediately scatter rodenticide. Poisoned rats often die in inaccessible wall voids, creating odor problems and secondary pest issues (flies, beetles) for weeks.
• Don't assume snap traps will solve it. Traps kill individuals; they don't address the entry points that brought the rats in. Without exclusion, new rats keep replacing the trapped ones.
• Don't seal entry points before removing the rats. Trapped rats inside the wall will chew through drywall, wiring, and fascia trying to escape — turning a pest problem into thousands of dollars of structural damage.
• Don't ignore early signs. A rat infestation that's caught at signs #1-3 typically costs $400-$1,000 to resolve. The same infestation caught at sign #10 (daytime sightings) often costs $1,500-$3,000+ once exclusion, trapping, and damage repair are factored in.

What to do next

If you've identified two or more signs from this list, the right move is to schedule a free inspection with a NJ DEP licensed rat exterminator. They'll identify the species, find the entry points, and recommend an exclusion-based treatment plan that solves the problem permanently — not just for a few weeks.