Japanese Flying Squirrel (Momonga): Facts, Gliding and Photos

In Japan they are called momonga, and their huge dark eyes and round faces have made them stars of the internet. Flying squirrels spend their days tucked into tree holes and come out at dusk to glide between the trunks of Japan’s mountain forests. Here is what these tiny gliders are, how they fly and how they live.

The Japanese flying squirrel and the Ezo momonga

Two kinds of flying squirrel live in Japan. The Japanese flying squirrel, Pteromys momonga, is found only on the islands of Honshu and Kyushu, where it is listed by the American Society of Mammalogists’ Mammal Diversity Database as a native species. On Hokkaido in the north lives the Ezo momonga, Pteromys volans orii, a Japanese subspecies of the Siberian flying squirrel, whose range stretches all the way west to Finland and Estonia.

The two look very similar, and photo collections like this one usually circulate simply as “Japanese flying squirrels”. Both are small: the Japanese flying squirrel measures about 12 to 23 cm in head and body, plus a flattened tail of 11 to 13 cm, with silvery to buff-grey fur above and buff-white below.

How flying squirrels glide

Flying squirrels do not really fly; they glide. A furry membrane, the patagium, stretches from each wrist to each ankle. When the squirrel leaps and spreads its legs, the membrane opens like a small square sail, and the animal steers with its limbs and flattened tail.

The glides can be long. The Siberian flying squirrel has been recorded gliding more than 100 metres from tree to tree. Japanese flying squirrels are silent in the air and rarely come down to the ground at all.

What momonga eat and where they nest

The Japanese flying squirrel is strictly nocturnal. It spends the day in a nest or tree hole and comes out at dusk to feed on nuts, pine seeds, buds, bark and fruit, probably with a few insects as well. It lives in evergreen forests and builds its nests from moss and lichen where a branch meets the trunk, often in pines or spruces. A pair often shares the same nest.

Breeding, predators and conservation

• Breeding season: May to July, with one or two litters a year
• Litter size: one to five young, usually two or three
• Gestation: about four weeks; the young are weaned at around six weeks
• Lifespan: other flying squirrels typically live four to five years
• Predators: owls are the most likely; the squirrels flatten against bark and dodge in erratic glides to escape
• Status: Least Concern on the IUCN Red List

Watching for momonga in the wild means waiting near nest holes at dusk, when they come out to feed; keep quiet and well back so they emerge naturally.

For more animal portraits, see red-panda portraits with conservation context, or read about the trees that provide a forest setting through the winter.

Related reading

• A Young Squirrel Brought Indoors: The Rescue Photo Sequence
• Animals in Snow: Winter Photographs, Food, Rest and Movement
• Japanese Snow Monkeys Bathing in Hot Springs

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