Temporal range: Early Oligocene – Recent
|Northern flying squirrel (Glaucomys sabrinus)|
Flying squirrels are not capable of flight like birds or bats; instead, they glide between trees. They are capable of obtaining lift within the course of these flights, with flights recorded to 90 meters (295 ft). The direction and speed of the animal in midair is varied by changing the positions of its two arms and legs, largely controlled by small cartilaginous wrist bones. This changes the tautness of the patagium, a furry parachute-like membrane that stretches from wrist to ankle. It has a fluffy tail that stabilizes in flight. The tail acts as an adjunct airfoil, working as an air brake before landing on a tree trunk.
The colugos, Petauridae, and Anomaluridae are gliding mammals which are similar to flying squirrels because of convergent evolution. These mammals can glide through the trees, but they do not actually fly (like birds and bats). They have a membrane of skin on either side of their body.
Prior to the 21st century, the evolutionary history of the flying squirrel was frequently debated. This debate was clarified greatly as a result of two recent molecular studies. These studies found support that flying squirrels originated 18–20 million years ago, are monophyletic, and have a sister relationship with tree squirrels. There are four hypotheses as to why gliding has evolved in mammals: economical locomotion, foraging optimization, evasion of predators, and control of landing forces.
The largest of the species is the woolly flying squirrel (Eupetaurus cinereus). The two species of the genus Glaucomys (Glaucomys sabrinus and Glaucomys volans) are native to North America, and the Siberian flying squirrel is native to parts of northern Europe (Pteromys volans).
Thorington and Hoffman (2005) recognize 15 genera of flying squirrels in two subtribes.
Tribe Pteromyini – flying squirrels
- Subtribe Glaucomyina
- Genus Eoglaucomys
- Kashmir flying squirrel, Eoglaucomys fimbriatus
- Genus Glaucomys – New World flying squirrels (American flying squirrels), North America
- Genus Hylopetes, Southeast Asia
- Particolored flying squirrel, Hylopetes alboniger
- Afghan flying squirrel, Hylopetes baberi
- Bartel's flying squirrel, Hylopetes bartelsi
- Gray-cheeked flying squirrel, Hylopetes lepidus
- Palawan flying squirrel, Hylopetes nigripes
- Indochinese flying squirrel, Hylopetes phayrei
- Jentink's flying squirrel, Hylopetes platyurus
- Sipora flying squirrel, Hylopetes sipora
- Red-cheeked flying squirrel, Hylopetes spadiceus
- Sumatran flying squirrel, Hylopetes winstoni
- Genus Iomys, Malaysia and Indonesia
- Javanese flying squirrel (Horsfield's flying squirrel), Iomys horsfieldi
- Mentawi flying squirrel, Iomys sipora
- Genus Petaurillus – pygmy flying squirrels, Borneo and the Malay Peninsula
- Genus Petinomys, Southeast Asia
- Basilan flying squirrel, Petinomys crinitus
- Travancore flying squirrel, Petinomys fuscocapillus
- Whiskered flying squirrel, Petinomys genibarbis
- Hagen's flying squirrel, Petinomys hageni
- Siberut flying squirrel, Petinomys lugens
- Mindanao flying squirrel, Petinomys mindanensis
- Arrow flying squirrel, Petinomys sagitta
- Temminck's flying squirrel, Petinomys setosus
- Vordermann's flying squirrel, Petinomys vordermanni
- Genus Eoglaucomys
- Subtribe Pteromyina
- Genus Aeretes, northeastern China
- Groove-toothed flying squirrel (North Chinese flying squirrel), Aeretes melanopterus
- Genus Aeromys – large black flying squirrels, Thailand to Borneo
- Genus Belomys, Southeast Asia
- Hairy-footed flying squirrel, Belomys pearsonii
- Genus Biswamoyopterus, India and Bangladesh
- Namdapha flying squirrel, Biswamoyopterus biswasi
- Genus Eupetaurus, Kashmir; rare
- Woolly flying squirrel, Eupetaurus cinereus
- Genus Petaurista, Southeast Asia
- Red and white giant flying squirrel, Petaurista alborufus
- Spotted giant flying squirrel, Petaurista elegans
- Hodgson's giant flying squirrel, Petaurista magnificus
- Bhutan giant flying squirrel, Petaurista nobilis
- Indian giant flying squirrel, Petaurista philippensis
- Chinese giant flying squirrel, Petaurista xanthotis
- Japanese giant flying squirrel, Petaurista leucogenys
- Red giant flying squirrel, Petaurista petaurista
- Genus Pteromys – Old World flying squirrel, Finland to Japan
- Genus Pteromyscus, southern Thailand to Borneo
- Smoky flying squirrel, Pteromyscus pulverulentus
- Genus Trogopterus, China
- Complex-toothed flying squirrel, Trogopterus xanthipes
- Genus Aeretes, northeastern China
- Mechuka giant flying squirrel (Petaurista mechukaensis)
- Mishmi Hills giant flying squirrel (Petaurista mishmiensis)
- Mebo giant flying squirrel (Petaurista siangensis)
The life expectancy of flying squirrels in the wild is about six years, but flying squirrels can live up to fifteen years in zoos. The mortality rate in young flying squirrels is high because of predators and diseases. Predators of flying squirrels include tree snakes, raccoons, owls, martens, fishers, coyotes, bobcats, and feral cats. In the Pacific Northwest of North America, the northern spotted owl (Strix occidentalis) is a common predator of flying squirrels.
Flying squirrels are usually nocturnal, since they are not adept at escaping birds of prey that hunt during the daytime. They eat according to their environment; they are omnivorous, and will eat whatever food they can find. The North American southern flying squirrel eats seeds, insects, gastropods (slugs and snails), spiders, shrubs, flowers, fungi, and tree sap.
The mating season for flying squirrels is during February and March. When the infants are born, the female squirrels live with them in maternal nest sites. The mothers nurture and protect them until they leave the nest. The males do not participate in nurturing their offspring.
At birth, flying squirrels are mostly hairless, apart from their whiskers, and most of their senses are not present. Their internal organs are visible through the skin, and their sex can be signified. By week five, they are almost fully developed. At that point, they can respond to their environment and start to develop a mind of their own. Through the upcoming weeks of their lives, they practice leaping and gliding. After two and a half months, their gliding skills are perfected, they are ready to leave the nest, and are capable of independent survival.
Flying squirrels can easily forage for food in the night, given their highly developed sense of smell. They harvest fruits, nuts, fungi, and birds' eggs. Gliding conserves energy. Many gliders have specialized diets and there is evidence to believe that gliders may be able to take advantage of scattered protein deficient food. Additionally, gliding is a fast form of locomotion and by reducing travel time between patches, they can increase the amount of foraging time.
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|Wikimedia Commons has media related to Pteromyini.|
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