PestDecoderDecode a clue

Inspection route

Attic and roofline pest clues

Height, daylight timing and entry geometry separate roof rats, squirrels, bats, cluster flies and wood pests.

Inspect in this order

Start where evidence is most likely to remain undisturbed. Photograph scale and placement before cleaning, then establish a clean baseline only when the material can be handled safely.

  1. Log sound timing before entering.
  2. Inspect roofline and vents from ground level.
  3. Check below rafters for droppings, wings or frass.
  4. Observe exterior exits at dusk without blocking them.
Avoid this shortcut

Do not handle bats, disturb a roost or seal wildlife inside.

Common candidates in this location

Location helps prioritize candidates, but it does not identify a pest by itself. Use a physical sign and companion clue before making a treatment decision.

high concern

Roof rat

Rattus rattus

Slender rat-scale droppings and nighttime movement in attics, rafters or elevated routes.

DroppingsHoles and openingsSounds and movement
Read evidence profile
medium concern

Eastern gray squirrel

Sciurus carolinensis

Daytime bounding and rolling sounds near a larger roof opening, with leaves or bulky nesting material.

Holes and openingsSounds and movementDamage and gnawing
Read evidence profile
high concern

Big brown bat

Eptesicus fuscus

Crumbly droppings with shiny insect fragments below a high roost or entry, sometimes with fluttering at dusk.

DroppingsHoles and openingsSounds and movement
Read evidence profile
low concern

Cluster fly

Pollenia spp.

Slow dark flies clustering at upper windows or attics seasonally, without an indoor food or drain breeding source.

Wings and swarmersOdors
Read evidence profile
high concern

Old house borer

Hylotrupes bajulus

Larger oval exit holes, coarse packed frass and feeding sounds in softwood framing.

Frass and pelletsHoles and openingsLarvae and grubs
Read evidence profile
high concern

Drywood termite

Kalotermitidae

Uniform hard pellets in small piles directly below tiny wood openings, often recurring after cleanup.

Frass and pelletsWings and swarmersHoles and openings
Read evidence profile

Evidence types worth checking

Droppings

Shape, ends, texture and placement can narrow rodents, cockroaches and bats without touching the material.

7 candidate profiles

Inspect this clue

Holes and openings

Diameter, edge quality, material and debris below an opening can distinguish insect exit holes, rodent routes and wildlife entry.

8 candidate profiles

Inspect this clue

Sounds and movement

Time of day, route height, rhythm and weight can narrow rodents, squirrels, bats, insects and plumbing-related noise.

6 candidate profiles

Inspect this clue

Damage and gnawing

Surface scraping, paired tooth marks, hollow wood, clipped fibers and food-package holes are high-value contextual clues.

12 candidate profiles

Inspect this clue

Stains and smears

Fecal spotting, rub marks and blood-like stains gain meaning from placement, solubility and nearby physical evidence.

5 candidate profiles

Inspect this clue

Odors

Musty, oily, ammonia-like or sewage-associated odors are supporting clues only and should be tied to a physical source.

8 candidate profiles

Inspect this clue

Build a repeatable baseline

Record the date, exact position and a scale reference. If cleanup is safe, note whether the sign returns in the same route, below the same opening or near the same resource. Repeat location can be more informative than color or a single photograph.

Source basis