What are flying squirrels?
Flying squirrels are known for soaring anywhere from 150 to 500 feet, sailing from tree to tree to avoid ground predators—but they actually glide rather than fly. Flying squirrels don’t have their own means of propulsion, like a bird or bat, but glide using a furry membrane called the patagium that connects at their wrists down to their ankles. When they leap from a tree and spread their limbs, this flap of loose skin forms a square and acts like a hang glider.
Flying squirrels can turn by lowering one arm, while a specialized piece of cartilage not found in other gliding mammals extends from the wrist to support the pagatium and help them steer. These animals are capable of making 180-degree turns in mid-air to evade flying predators like owls. Moving their hands and feet in opposite directions also helps flying squirrels direct their movements so they land safely on their strong, silent padded feet. Their long, fluffy tails stabilize their flight and flipping those tails up helps them put on the brakes.
There are about 50 species of flying squirrels ranging across most of North America down into Central America, and stretching from Southeast and Northern Asia into Siberia and Scandinavia. They make their homes in in woodpecker holes, nests abandoned by birds, or tree cavities in forests, woodlands, and jungles.
Appearance and diet
Aside from their patagia, flying squirrels look similar to their grounded cousins, with small rounded faces, prominent ears, and fluffy tails that can be as long as their bodies. Their eyes are large, helping these nocturnal mammals navigate the dark, and their fur color and markings vary by species.
Their sizes vary as much as their color. Pakistan’s woolly flying squirrel is the largest gliding mammal at five and a half pounds while Hose’s pygmy flying squirrel of Borneo is the tiniest at just a little more than three ounces.
Diets vary by location as well. In the Americas, the northern flying squirrel dines on insects, seeds, nuts, and fungi while the southern flying squirrel will sometimes eat eggs or carrion. Meanwhile, the Indochinese flying squirrel, found in China and parts of Southeast Asia, prefers cultivated fruit.
Some flying squirrels have only one mating cycle per year but others, such as the Japanese dwarf flying squirrel, have two. The time of year for mating and birth depend on the species as well. Many are promiscuous, meaning that males and females mate with multiple partners.
In some species, such as the southern flying squirrels of North and Central America, the young are born blind, hairless, and helpless, while others are more well-developed at birth. Females care for the young. There’s variation in development, too; for example, southern flying squirrels are weaned at two months while black flying squirrels of Southeast Asia are weaned at four months.
Though solitary, flying squirrels will sometimes nest together, typically with family members, to keep warm in the winter months.
Almost half of flying squirrel species, such as the southern flying squirrel in North and Central America and the Javanese flying squirrel of Southeast Asia, have stable populations. Their elusive nature makes them hard to study so there’s little data on some species.
For those with decreasing populations—such as the endangered smoky flying squirrel of Southeast Asia—threats include destruction of their forest habitats by logging, other types of wood harvesting, and agricultural and residential development, according to the International Union for Conservation of Nature. Hunting and trapping are also threats to species such as Bhutan’s giant flying squirrel and the Northern Chinese flying squirrel.
In the United States, northern flying squirrels are endangered in Pennsylvania. Not only do they face habitat loss from development but there’s also been a decline in the fungi they eat due to the presence of hemlock wooly adelgids, invasive insects that destroy the hemlock stands where fungi flourish.