Northern Flying Squirrel
Glaucomys sabrinus
Flying squirrels are an occasional but notable wildlife pest in commercial buildings adjacent to wooded areas in Windsor-Essex.
Their colonial nature means that a commercial attic or roof void may be occupied by multiple individuals simultaneously — a different management challenge than the single-animal exclusion typical of grey and red squirrel problems.
Their exclusively nocturnal activity means they are most likely to be detected through monitoring traps, acoustic monitoring, or evidence of activity (faeces, urine staining, nesting material) during daytime inspections, rather than through direct observation.
Habitat
Commercial buildings most at risk of flying squirrel entry are those with: mature trees close enough to the roofline to be accessed by gliding squirrels, roof void spaces with adequate thermal insulation (attractive for winter denning), and small, overlooked entry gaps in the building envelope at roofline level.
The species’ ability to glide from a tree canopy directly to a building roof means that even buildings surrounded by open space may be reached if mature trees stand nearby at an appropriate elevation.
Green roof installations with trees or large shrubs in elevated planters can serve as staging points for gliding access.
Active Areas
Windsor
Tecumseh
LaSalle
Amherstburg
Lakeshore
Mature mixed-wood areas support flying squirrel populations.
Essex
Kingsville
Leamington
Chatham-Kent
Low prevalence. Found in wooded areas of Chatham-Kent but rarely a structural pest.
St. Thomas
Low prevalence. Occasional attic entries in properties adjacent to mature woodlots.
Seasonality
Commercial pest management monitoring should address flying squirrels year-round in at-risk buildings. The primary exclusion window is late summer–early autumn (August–September) before the peak autumn denning entry period.
A spring inspection (March–April) allows assessment of any young of the year that may be present in the attic and helps plan removal timing around the potential presence of dependent young in the nest.
Spring
Summer
Autumn
Winter
Appearance
For commercial wildlife identification, the flying squirrel is distinguished by its small size, very large dark eyes, and the visible skin fold (patagium) along the body flanks.
Evidence in commercial buildings — light, closely spaced faeces (larger than mouse droppings but smaller than grey squirrel droppings) in attic areas, urine staining on insulation, and nesting material in concentrated areas — supports identification.
Because flying squirrels may be present as a colony, counting evidence (droppings, tracks in dust) gives a better estimate of the number of animals present than isolated sightings.
- Loose fold of skin (patagium) from wrist to ankle on each side enabling gliding — the defining structural feature
- Flat, horizontally oriented tail used as a rudder and air brake during glides
- Extremely large, prominent eyes adapted for night vision — much larger relative to head size than other squirrel species
- Velvety, fine-textured grey-brown fur with white to cream underside
- Strictly nocturnal — may be resident in an attic for months without ever being seen by the homeowner
- Often enters and occupies attics in groups or colonies rather than as solitary individuals
Behaviour
The colonial nature of flying squirrel attic occupation has specific implications for commercial wildlife management. Exclusion programmes must account for the possibility of multiple individuals within the structure simultaneously and ensure that one-way exclusion devices are sized and positioned correctly for this smaller species.
Temporary acoustic monitoring in the attic overnight (using a bat detector or audio recorder sensitive to high frequencies) can provide evidence of colony size before management begins.
Because flying squirrels share den sites seasonally, some individuals may not be in the building on any given night, reinforcing the need for sustained monitoring to confirm complete removal.
Lifecycle
Birth / Pup
Pups in a commercial building roof space require a wildlife removal approach that integrates the breeding timeline.
Licensed wildlife removal professionals should assess the likely presence of young before implementing exclusion or trapping measures to avoid orphaning pups within inaccessible structural voids.
Juvenile
Juvenile dispersal creates two entry risk windows (May–July and August–October). Commercial building envelope inspections should be completed in April–May and again in August to identify and seal any gaps before each juvenile dispersal peak.
Adult
Adult flying squirrels in a commercial building are the primary management target, with the colonial nature of their occupation requiring multi-animal exclusion rather than single-animal removal.
Commercial wildlife management providers should conduct a population assessment before exclusion to ensure all entry points are identified and appropriately equipped with exclusion devices for the colony size.
Signs You May Have a Problem
- Nocturnal-only activity sounds from ceiling voids or roof spaces — no daytime sounds despite presence of activity evidence
- Multiple accumulations of droppings in the attic or roof void, suggesting more than one animal
- Small entry points at roofline level, possibly located at corners, roof-wall junctions, or near soffit vents, with worn edges indicating frequent use
- Nesting material and food cache debris scattered across the attic rather than concentrated in one spot
- Acoustic monitoring overnight (audio recorder placed in the attic) captures high-frequency calls and multiple individuals moving simultaneously
- Urine staining across a broad area of attic insulation, consistent with a colonial rather than single-animal occupation
Risks & Concerns
Commercial risks from flying squirrel infestations mirror those of other squirrel species but with the added complexity of potential multi-animal presence. Fire risk from gnawed wiring, contamination of HVAC systems, insulation damage, and attraction of secondary pests are all relevant.
For commercial buildings with sensitive electrical or data infrastructure in roof spaces, flying squirrel gnawing activity presents an operational disruption risk in addition to the fire risk.
The strictly nocturnal behaviour means commercial operations may not be aware of an infestation until significant damage has occurred.
Prevention
- Schedule annual roofline inspections specifically targeting flying squirrel entry points in April and August before each dispersal risk period
- Trim all trees adjacent to the building to eliminate gliding access points to the roofline
- Install commercial-grade hardware cloth over all identified roofline gaps and vulnerable areas
- Include flying squirrel as a specific wildlife species in the facility's pest monitoring programme for buildings in wooded locations
- Establish a documented wildlife entry response protocol including assessment of young presence before any exclusion action is taken
- Document all wildlife prevention and exclusion measures for facility management records and insurance files
DIY Control
- Commission a professional wildlife inspection before attempting any DIY exclusion measures — colonial infestations require a complete entry point map
- Install hardware cloth over identified entry points as an interim measure while professional assessment is arranged
- Document all evidence of flying squirrel activity (droppings location, sounds, entry point condition) for the professional assessment
- Review Ontario Fish and Wildlife Conservation Act requirements before using any traps — live trapping and relocation requirements apply
Professional Control
- Licensed wildlife removal and exclusion service under the Ontario Fish and Wildlife Conservation Act, conducted by an authorised professional
- Colony size assessment using monitoring traps, acoustic evidence, and evidence surveys before implementing exclusion
- Commercial-grade exclusion materials and installation across all identified entry points, with installation documented for facility records
- Post-exclusion inspection, damage assessment, and remediation recommendations for insulation, wiring, and structural elements affected by the infestation