The size and shape diagnostic
| Species | Length | Shape | Where you find them |
|---|---|---|---|
| House mouse (Mus musculus) | 3-6 mm | Granular, pointed one end | Drawers, pantries, behind appliances, baseboards |
| Norway rat (Rattus norvegicus) | 18-20 mm | Blunt, capsule-shaped | Garage corners, basement floors, crawlspace, foundation perimeter |
| Roof rat (Rattus rattus) | 12-15 mm | Curved, pointed both ends | Attic insulation, on top of cabinets, ceiling fixtures, in soffits |
| Deer mouse (Peromyscus) | 5-7 mm | Granular, slightly larger than house mouse | Outbuildings, sheds, rural-adjacent properties |
| Squirrel (for comparison) | 8-10 mm | Cylindrical, blunt both ends | Attics with chewed roof entry, near nut shells |
The location is as diagnostic as the size
Even at similar size, location separates species. Roof rat droppings appear above eye level — in attic insulation, on top of kitchen cabinets, on the ledge of a closet shelf. Norway rat droppings appear at floor level — under appliances, in a garage corner, along a basement wall. House mouse droppings appear in tight enclosed spaces — inside a pantry, in a kitchen drawer, behind a stove. If you find droppings consistently above your head in a Vancouver west-side or Kitsilano home, suspect roof rats before mice.
How to age droppings
Fresh droppings are dark brown to black, soft, and shiny. Older droppings are grey, hard, and crumble when probed. Activity within the last 24 hours leaves moist droppings; week-old droppings are dry and brittle. Sweep an area, mark the date with painter's tape, and check 48 hours later — fresh droppings in the cleaned area confirm active infestation.
Safe dropping cleanup: the BCCDC protocol
Before you touch any rodent droppings — regardless of species — treat them as a biohazard. Hantavirus, carried primarily by deer mice (Peromyscus maniculatus) but present in other rodent excreta, can be aerosolized by sweeping or vacuuming dry droppings. The BC Centre for Disease Control protocol: ventilate the space for at least 30 minutes before entering, wear an N95 respirator and disposable nitrile gloves, spray droppings liberally with a 1:10 bleach-to-water solution, let sit for 5 minutes, then wipe with paper towels. Double-bag the paper towels and place in household waste. Do not vacuum dry droppings — the Dyson is not PPE.
Why the species identification changes your treatment plan
Once you confirm the species from the droppings, every subsequent decision branches. Norway rat droppings at ground level in a Richmond or Strathcona home mean your tech will focus the inspection on the foundation perimeter, crawlspace vents, sewer lateral, and deck-house junctions. Roof rat droppings in an attic in Kitsilano or Burnaby Heights mean the inspection moves to the roof line — soffit-fascia junctions, dormer detailing, gable vents, tree canopy contact points. House mouse droppings behind a Burnaby kitchen stove mean interior bait stations plus perimeter utility penetration sealing. Treating for the wrong species wastes weeks and money. Read our full species comparison at [Roof Rats vs Norway Rats](/guide/roof-rats-vs-norway-rats).
The 48-hour confirmation test
Confirm active rodent infestation from droppings
A simple 48-hour test to tell whether droppings are from a current infestation or a historical one. Takes 5 minutes of setup.
- 1Photograph and clean the areaPhotograph the dropping site with a scale reference (a loonie works well). Then clean all visible droppings using the BCCDC bleach protocol. Mark the cleaned area with painter's tape and note the date and time.
- 2Wait 48 hours without disturbing the spaceDo not use the area normally — don't slide the stove back, open the cabinet repeatedly, or otherwise disturb the space. The goal is to give mice or rats undisturbed access to the area for two nights.
- 3Re-inspect under good lightReturn after 48 hours with a flashlight. New dark, shiny droppings in the cleaned zone confirm active infestation. No new droppings suggests either a historical problem or the rodent has shifted activity elsewhere — expand the search to adjacent areas.
- 4Count and map new droppingsCount the new droppings and photograph them. More than 10 in 48 hours in a single area indicates a runway with regular use. Note the location relative to walls, corners, and pipes — this tells your tech where to focus the inspection.
Other signs that confirm the dropping identification
- Gnaw marks: mouse gnaw marks are fine and irregularly textured, about 1-2 mm deep. Rat gnaw marks are visible and toothy, 4-6 mm deep. Norway rat gnaw marks at floor level; roof rat gnaw marks at attic beam height.
- Greasy rub marks: rats leave visible grease tracks along walls and beams from repeated use of runways. Mice leave faint smudges at baseboard height.
- Urine pillars: in heavily infested spaces, mouse urine mixed with droppings and fur forms small crystallized pillars, visible under UV light. Not seen in light infestations.
- Tracks in dust: Norway rats leave obvious footprint tracks in dusty basement or crawlspace floors. Each print shows four toes on the forefeet, five on the hindfeet. Roof rat prints are similar but slightly smaller.
- Burrows: Norway rats create 5-8 cm diameter burrows in soft soil along foundations. Roof rats don't burrow.