Quick Answer
Flying squirrels and grey squirrels are very different. Flying squirrels are 8-10 inches (including tail), 3-5 oz, with large eyes, a flat tail, and a gliding membrane (patagium) between front and hind legs. They are nocturnal and rarely seen. Grey squirrels are 18-20 inches, 1-2 lbs, with a bushy tail, no gliding membrane, and are diurnal (active during the day). Flying squirrels are more common in attics than most people realize because they are silent and nocturnal.
Flying Squirrel vs Grey Squirrel: Identification Guide
Many homeowners with attic squirrels are surprised to learn they may have flying squirrels rather than grey squirrels. The two species are very different in behavior, appearance, and management. Flying squirrels are smaller, nocturnal, and often live in colonies. Grey squirrels are larger, diurnal, and typically solitary or in small family groups.
Quick Comparison Table
| Feature | Flying Squirrel | Grey Squirrel |
|---|---|---|
| Size (Total Length) | 8-10 inches | 18-20 inches |
| Weight | 3-5 oz | 1-2 lbs |
| Tail | Flat, broad, used as rudder | Bushy, round, used for balance |
| Eyes | Large, bulging (nocturnal adaptation) | Smaller, proportionate |
| Gliding Membrane | Present (patagium) | Absent |
| Activity | Nocturnal (active at night) | Diurnal (active during day) |
| Sound | High-pitched chirps, squeaks | Barks, chattering |
| Social Structure | Colonial (10-30+ in one nest) | Solitary or small family groups |
| Nest in Attic | Common (overlooked) | Very common |
| Hibernation | Huddles in groups but no true hibernation | Active year-round, less active in winter |
| Diet | Nuts, seeds, insects, bird eggs | Nuts, acorns, bird eggs, tree buds |
Physical Differences
Size and Body Shape
Flying squirrels are much smaller — about the size of a chipmunk (3-5 oz). Grey squirrels are noticeably larger (1-2 lbs). The easiest way to tell them apart is size: if it looks like a small chipmunk but is grey, it is likely a flying squirrel.
The Gliding Membrane
Flying squirrels have a furred membrane called the patagium that stretches from the wrist to the ankle on each side. When they stretch their legs, this membrane creates a square shape that allows them to glide 30-150 feet between trees. Grey squirrels do not have this membrane.
Eyes
Flying squirrels have large, bulging eyes adapted for night vision. This is their most noticeable feature when seen up close. Grey squirrels have proportionally smaller eyes.
Tail
Flying squirrels have a flat, broad tail that acts as a rudder during gliding. Grey squirrels have a round, bushy tail used for balance and communication.
Behavioral Differences
Activity Time
The most reliable way to tell them apart: flying squirrels are strictly nocturnal. If you hear scratching in your attic at night, it could be flying squirrels or rats. Grey squirrels are active during the day and sleep at night. If you hear attic noise during the day, it is likely grey squirrels.
Social Behavior
Flying squirrels are highly social and live in colonies of 10-30 or more individuals. They huddle together for warmth in winter. Grey squirrels are more solitary. If you have a large number of squirrels in your attic, they are likely flying squirrels.
Signs in Your Attic
| Sign | Flying Squirrel | Grey Squirrel |
|---|---|---|
| Noise timing | Night (scratching, scampering) | Daytime (running, jumping) |
| Noise type | Light scratching, high-pitched chirps | Heavy running, thumping |
| Droppings | Small (1/4 inch), dark, similar to mouse | Medium (1/2 inch), tubular |
| Nesting material | Leaves, moss, shredded bark | Leaves, twigs, paper |
| Number of animals | 10-30+ (colony) | 1-5 (family group) |
| Entry holes | Small (1.5-2 inches) | Larger (3-4 inches) |
Management Differences
Flying squirrel removal is more complex than grey squirrel removal because of the larger numbers and the need to ensure all animals are out before exclusion. Professional removal is recommended for flying squirrel colonies.
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FAQ: Flying Squirrel vs Grey Squirrel
Do flying squirrels actually fly?
No, they glide. They have a membrane that allows them to glide 30-150 feet between trees. They cannot fly like birds or bats.
Are flying squirrels dangerous?
No. They are not aggressive and rarely bite. They are not known to carry rabies. However, they can carry parasites and their droppings can be a health concern.
Sources: US Fish and Wildlife Service, USDA Wildlife Services, state wildlife agencies, CDC, academic extension services. This guide is for informational purposes only and does not constitute professional wildlife management advice.