8 Signs of a Rat Infestation: How to Identify Rats and Assess Severity (2026)
Count how many signs you find to estimate your severity and expected cost. 1-3 signs: mild ($150-$300). 4-5 signs: moderate ($300-$600). 6+ signs: severe ($600-$1,500+).
Quick Severity Assessment
The 8 Signs of a Rat Infestation
Norway rat droppings: 3/4 inch, blunt capsule shape. Roof rat droppings: 1/2 inch, pointed tips. Fresh droppings are dark and shiny; old droppings are gray and crumble. Found in kitchen cabinets, under appliances, in attics, along walls.
Rats chew constantly to wear down their teeth. Look for gnaw marks on wood trim, cabinet corners, food packaging, electrical wire insulation, plastic pipes, and structural materials. Fresh gnaw marks are pale and light-colored. Old marks are dark or weathered.
Rats have oily fur and run the same paths repeatedly along walls, pipes, and structural members. These repeated runs leave dark, smudged trails at rat height. Heavily used runways show thick grease marks that remain visible for months.
Rats are nocturnal. Listen for scratching, scurrying, or gnawing sounds between 2-3 hours after dark and just before dawn. Sounds inside walls run along wall studs. Ceiling sounds indicate attic activity. Thumping sounds in the attic are common with larger infestations.
Rats build nests from shredded paper, fabric, insulation, cardboard, and plant material. Look in attic insulation (torn and matted areas), behind appliances, inside storage boxes, in garages and sheds. Nests are typically bowl-shaped, compact, and well-hidden.
Norway rats burrow. Look for 2-3 inch round holes in soil near the foundation, under concrete slabs, near woodpiles, and in garden beds. Active burrow openings are clear of cobwebs; entrance edges look worn. Fresh soil near the opening indicates recent use.
Rat urine is only visible under UV (blacklight), where it glows blue-white in the dark. Buy an inexpensive UV flashlight and check along known runways, in the attic, under appliances, and inside cabinets. The smell (strong ammonia) is noticeable in heavy infestations even without UV.
Seeing a rat during daylight hours is a significant warning sign. Rats are nocturnal; daytime activity indicates overcrowding where the population has exceeded available harborage. A single dead rat found inside may indicate a larger die-off within walls or the attic.
Rat vs Mouse: How to Tell the Difference
| Indicator | Rat | Mouse |
|---|---|---|
| Dropping size | 1/2 to 3/4 inch (raisin-sized) | 1/8 to 1/4 inch (rice grain) |
| Dropping shape | Blunt or tapered capsule | Pointed at both ends |
| Gnaw marks | Larger, rougher (4mm wide) | Small, neat (2mm wide) |
| Entry hole size | 2 inches wide | 1/4 inch (very small) |
| Burrow holes | 2-3 inches, near foundation | Small or none |
| Sound | Louder scratching and thumping | Lighter, higher-pitched |
| Treatment cost | $150 - $600 professional | $100 - $300 professional |