Inspect and name
Published 24 September 2026
Attic droppings in Calgary: mouse pellet or bat guano
Something is moving in the attic. People guess wrong. They swear it is a raccoon because the noise sounds large. The evidence is mice. Or they assume mice, and the pile under the soffit is guano.
The treatment is not the same, so identification comes first. You often do not need to see the animal.
The press test
Do this on a cold dropping, outdoors or in a tray. Do not crush a pile in a closed attic with no mask.
- Mouse droppings stay a pellet. Press and the shape holds. Dense, solid.
- Bat guano crumbles. Press and it breaks into a fine powder.
Shape and place help. Mouse pellets scatter along a run — kitchen, garage, rim joist, wall void. Guano often stacks directly under a roost: on shingles, on the ground under a soffit slot.
If the pellet holds, treat it as a mouse problem until an inspection says otherwise. If it powders, stop sealing holes tonight.
Why the answer changes the job
Mice are a building-envelope job we do: inspect, treat what is inside, close the 6 mm joints freeze-thaw opens. That work lives on mouse-proofing and rodents.
Bats are not a mouse visit. All bats in Alberta are protected under the Wildlife Act. Little brown myotis, the species that most often uses buildings, is listed as endangered. Alberta’s bats-in-buildings guidance is specific: do not kill bats, do not plug holes while animals are in the roost, and maternity roosts are not disturbed 1 June through 1 September. If there is a health or safety problem in the living space and you cannot wait for fall, call the nearest Fish and Wildlife office. The Alberta Community Bat Program publishes the exclusion calendar. Structural repairs are a late-fall and winter job after the colony has left.
Framework will name what we can see on an envelope walk. Confirmed colony work is a refer — same posture as whole-suite bed-bug heat. We do not sell a mouse visit as a bat cure.
Do not dry-sweep a pile
Any dropping pile gets gloves. Do not broom it dry. Rodent droppings are a sanitation job; keep kids and pets off the area and wet-clean. If someone in the house is ill after disturbing a pile, that is a clinician, not a pest page.
Guano that has turned to powder is easy to put in the air. Large accumulations are a cleanup job with real respiratory protection, not a dust mask and a shop vac. We are not going to diagnose a lung disease from a photograph. We will tell you not to stir it.
What you can check from the yard
- White streaking on stucco or siding under a warm soffit or chimney.
- A cone of droppings on shingles or on the ground under one slot.
- Rub marks at ridge vents, chimney flashing, or the fascia–siding gap.
- South and west walls first. They take the sun.
If it looks like mice at grade, start with the mice insight and the brick–soffit note.
After the ID
| What the evidence says | Next step |
|---|---|
| Hard pellets, kitchen or garage run | Sanitation, traps on the run if the house is otherwise tight, or book mouse-proofing |
| Hard pellets plus a rub mark at the roofline | Inspect, treat what is inside, close the seam |
| Powdered pile under a soffit or chimney | Do not seal tonight. Read Alberta bats in buildings. We can look at the envelope and say if this is still a mouse job or a refer |
| Animal in the living space now | Occupancy first. Call 825 747 5787. Bats in the living space are a safety problem, not a wait-until-February problem |
Book the name, not a guess
Text a photo of the dropping and the elevation it sat under to 825 747 5787, or request a written next step. We will say if this is a visit, a watch, or a refer.