Flying Squirrel

The colugos, Petauridae, and Anomaluridae are gliding mammals which are similar to flying squirrels through convergent evolution, although are not particularly close in relation. Like the flying squirrel, they are scansorial mammals that use their patagium to glide, unpowered, to move quickly through their environment.

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 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. Due to their close ancestry, the morphological differences between flying squirrels and tree squirrels reveal insight into the formation of the gliding mechanism. Compared to squirrels of similar size, flying squirrels, northern and southern flying squirrels show lengthening in bones of the lumbar vertebrae and forearm, whereas bones of the feet, hands, and distal vertebrae are reduced in length. Such differences in body proportions reveal the flying squirrels' adaptation to minimize wing loading and to increase maneuverability while gliding. The consequence for these differences is that unlike regular squirrels, flying squirrels are not well adapted for quadrupedal locomotion and therefore must rely more heavily on their gliding abilities. Several hypotheses have attempted to explain the evolution of gliding in flying squirrels. One possible explanation is related to energy efficiency and foraging. Gliding is an energetically efficient way to progress from one tree to another while foraging, as opposed to climbing down trees and maneuvering on the ground floor or executing dangerous leaps in the air. Furthermore, take-off and landing procedures during leaps, implemented for safety purposes, may explain the gliding mechanism. While leaps at high speeds are important to escape danger, the high-force impact of landing on a new tree could be detrimental to a squirrel's health.

In 2019 it was observed, by chance, that a flying squirrel fluoresced pink under UV light. Subsequent research by biologists at Northland College in Northern Wisconsin found that this is true for all three species of North American flying squirrels. At this time it is unknown what purpose this serves. Non-flying squirrels do not fluoresce under UV light.

=== Recent species === New World flying squirrels belong to the genus Glaucomys (Greek for gleaming mouse). Old World flying squirrels belong to the genus Pteromys (Greek for winged mouse). The three species of the genus Glaucomys (Glaucomys sabrinus, Glaucomys volans and Glaucomys oregonensis) are native to North America and Central America; many other taxa are found throughout Asia as well, with the range of the Siberian Flying Squirrel (Pteromys volans) reaching into parts of northeast Europe (Russia, Finland and Estonia). 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 **** Afghan flying squirrel, E. f. baberi ** Genus Glaucomys – New World flying squirrels (American flying squirrels), North America *** Southern flying squirrel, Glaucomys volans *** Northern flying squirrel, Glaucomys sabrinus *** Humboldt's flying squirrel, Glaucomys oregonensis ** Genus Hylopetes, Southeast Asia *** Particolored flying squirrel, Hylopetes alboniger *** 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 *** Lesser pygmy flying squirrel, Petaurillus emiliae *** Hose's pygmy flying squirrel, Petaurillus hosei *** Selangor pygmy flying squirrel, Petaurillus kinlochii ** 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 Priapomys, western Yunnan in China and adjoining regions of Myanmar *** Himalayan large-eared flying squirrel, P. leonardi * 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 *** Black flying squirrel, Aeromys tephromelas *** Thomas's flying squirrel, Aeromys thomasi ** Genus Belomys, Southeast Asia *** Hairy-footed flying squirrel, Belomys pearsonii ** Genus Biswamoyopterus, northeastern India to southern China and southeast Asia *** Namdapha flying squirrel, Biswamoyopterus biswasi *** Laotian giant flying squirrel, Biswamoyopterus laoensis *** Mount Gaoligong flying squirrel Biswamoyopterus gaoligongensis ** Genus Eupetaurus, Pakistan to China; rare *** Western woolly flying squirrel, Eupetaurus cinereus *** Yunnan woolly flying squirrel, Eupetaurus nivamons *** Tibetan woolly flying squirrel, Eupetaurus tibetensis ** Genus Petaurista - giant flying squirrels, Southeast and East 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 *** Mechuka giant flying squirrel, Petaurista mechukaensis *** Mishmi Hills giant flying squirrel, Petaurista mishmiensis *** Mebo giant flying squirrel, Petaurista siangensis ** Genus Pteromys – Old World flying squirrels, Finland to Japan *** Siberian flying squirrel, Pteromys volans *** Japanese dwarf flying squirrel, Pteromys momonga ** Genus Pteromyscus, southern Thailand to Borneo *** Smoky flying squirrel, Pteromyscus pulverulentus ** Genus Trogopterus, China *** Complex-toothed flying squirrel, Trogopterus xanthipes The Mechuka, Mishmi Hills, and Mebo giant flying squirrels were discovered in the northeastern state of India of Arunachal Pradesh in the late 2000s. Their holotypes are preserved in the collection of the Zoological Survey of India, Kolkata, India.

Flying squirrels have a well-documented fossil record from the Oligocene onwards. Some fossil genera go far back as the Eocene, and given that the flying squirrels are thought to have diverged later, these are likely misidentifications. * Miopetaurista ** Miopetaurista crusafonti ** Miopetaurista dehmi ** Miopetaurista diescalidus ** Miopetaurista gaillardi ** Miopetaurista gibberosa ** Miopetaurista lappi ** Miopetaurista neogrivensis ** Miopetaurista thaleri ** Miopetaurista tobieni * Pliopetaurista ** Pliopetaurista kollmanni Daxner-Höck, 2004 ** Neopetes hoeckarum (De Bruijn, 1998) ** Neopetes macedoniensis (Bouwens and De Bruijn, 1986) ** Neopetes debruijni (Reumer & Hoek Ostende, 2003)

The life expectancy of flying squirrels in the wild is about six years, and 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. 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 they are capable of independent survival.