Flying squirrels are one of the most common attic invaders in the eastern United States, and because they’re nocturnal, many homeowners don’t realize they have a colony until the problem is well established. Unlike gray squirrels that move in as individuals or pairs, flying squirrels are highly social and often settle into attics in groups of 15 to 20, sometimes more. Colonies of up to 50 have been recorded sharing a single den site. If you’re hearing strange sounds at night or noticing odd smells from above, here’s what you’re likely dealing with and how to handle it.
How to Tell It’s Flying Squirrels
The biggest clue is timing. Flying squirrels are active at night, so you’ll hear scratching, rustling, and faint chirping sounds after dark, typically starting around dusk. Gray squirrels and red squirrels are daytime animals, so if your attic noises happen in the early morning or late afternoon, a different species is responsible. Flying squirrel activity peaks during winter months, when colonies gather indoors to conserve heat.
Their droppings are small, dark, and easy to confuse with mouse droppings. The difference is volume: a colony of 15 or more animals produces far more waste than a few mice would, and flying squirrels tend to create dedicated latrine areas rather than scattering droppings randomly. You may also notice a strong urine odor that worsens over time, especially in warm weather. Nests are another giveaway. Flying squirrels shred insulation, leaves, fur, bark, and other soft materials into compact nests tucked into corners or wall cavities.
One detail that surprises many homeowners is how small the entry point can be. Flying squirrels can fit through a hole just 1.25 inches in diameter. That’s roughly the size of a quarter. Gaps around soffit edges, ridge vents, gable vents, and where utility lines enter the house are common entry points. Because the animals are small and enter at night, you may never see them come and go.
Damage They Cause
A single flying squirrel is a minor nuisance. A colony living in your attic for months is a serious problem that touches your home’s structure, safety, and air quality.
Like all rodents, flying squirrels must gnaw constantly to keep their teeth from overgrowing. In an attic, that means chewing on electrical wiring, wooden beams, rafters, and soffits. Gnawed wires create short circuits and increase fire risk. Damaged structural wood weakens your roof and compromises weatherproofing. They also tear apart insulation to build nests, which reduces your home’s energy efficiency and raises heating and cooling costs.
The biological hazards are just as concerning. Over time, droppings and urine saturate insulation and can seep through ceiling materials, causing visible stains and persistent odors. Mold growth becomes likely in these damp, contaminated areas. Flying squirrel waste can harbor salmonella and other harmful bacteria, and in poorly ventilated attic spaces, airborne pathogens become a real risk. Their nesting materials also attract fleas, ticks, and mites, which can eventually make their way into your living space.
Why Removal Is Tricky
Getting flying squirrels out of an attic is more complicated than most people expect, for two reasons: colony size and chewing ability.
Because flying squirrels live in groups, you’re not evicting one animal. You’re dealing with a colony that knows every gap and crack in your roofline. The standard approach for many wildlife species is a one-way exclusion door, a device mounted over the entry point that lets animals leave but not return. This works well for raccoons and some other species, but wildlife professionals generally avoid using one-way doors for squirrels. The reason is simple: squirrels chew. If you block their main entrance, they’ll often just gnaw a new hole a foot or two away. One-way doors only work on flying squirrels in specific situations, like homes with brick or metal exteriors that resist chewing.
Trapping and removing the colony is the more reliable method, but it requires patience. Every individual needs to be accounted for, and every entry point needs to be sealed with materials the animals can’t chew through, typically heavy-gauge hardware cloth or metal flashing. Missing even one small gap means the colony (or a new one) will move right back in.
Timing Removal Around Breeding Season
Flying squirrels breed twice a year. The first mating period occurs in late winter, with young born after a 40-day gestation, putting births in early to mid spring. A second breeding period happens in summer. Litters average three to four young, and the babies can’t forage on their own until about six weeks of age.
This matters because evicting adults while flightless, dependent babies are still in the nest means those young will die inside your walls or attic. Beyond the obvious ethical problem, decomposing animals create terrible odors and attract insects. The safest windows for removal are late fall before winter colonies form, or midsummer after spring litters have matured but before second litters arrive. A wildlife professional can check for nursing females and juveniles before starting exclusion work.
Legal Restrictions on Removal
Wildlife laws vary significantly by state, and flying squirrels are often treated differently from gray squirrels in the regulations. In Massachusetts, for example, it’s illegal to capture and relocate any wild animal to a different area. The law does allow property owners to remove flying squirrels found damaging their property, but only during open season unless a special permit is obtained from the state fish and game agency. Other states have their own rules about trapping, relocating, and which species require permits.
Before attempting removal yourself, check your state’s wildlife regulations or contact your local wildlife agency. Many states require that removal be done by a licensed wildlife control operator, and penalties for improper handling can include fines.
Sealing Your Home Against Reentry
Removal without exclusion is pointless. Flying squirrels will return to a known den site, and other colonies in the area will discover the same entry points. A thorough exclusion job involves inspecting the entire roofline, soffit, fascia, gable vents, ridge vents, and any point where different building materials meet. Every gap larger than about an inch needs to be sealed with chew-proof material.
Hardware cloth (heavy wire mesh) secured with screws works for most openings. Metal flashing can cover larger gaps along the roofline. Expanding foam alone won’t hold; squirrels chew through it easily. Pay special attention to where plumbing vents, electrical lines, and cable wires enter the house, as these penetrations often leave gaps just large enough for a flying squirrel to squeeze through.
Trimming tree branches near your roof also helps. Flying squirrels glide from high points to lower ones, and a tall tree near your house gives them an easy launch pad. While they can glide impressive distances (over 100 feet in some cases), keeping branches well clear of your roofline forces them to land on the ground first, making your attic a less convenient target. A gap of at least 8 to 10 feet between branch tips and your roof is a reasonable starting point.
Cleanup After the Colony Is Gone
Once the animals are out and the entry points are sealed, the contaminated insulation and nesting material needs to be dealt with. In a colony that’s been active for a full winter, insulation in the affected area is typically compressed, shredded, and saturated with urine. Simply leaving it in place means ongoing odor problems and potential mold growth.
Professional attic remediation involves removing the contaminated insulation, sanitizing the space to eliminate bacteria and parasites, and installing new insulation. For smaller infestations caught early, spot-cleaning the latrine areas and removing nesting material may be sufficient. If you’re doing any cleanup yourself, wear a respirator rated for particulates (not just a dust mask), gloves, and eye protection. Dried rodent waste becomes airborne easily when disturbed, and inhaling those particles is how most exposure to harmful bacteria occurs.