Flying squirrel

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Flying squirrel
Temporal range: Early Oligocene – Recent
Glaucomys sabrinus.jpg
Northern flying squirrel (Glaucomys sabrinus)
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Sciuridae
Subfamily: Sciurinae
Tribe: Pteromyini
Brandt, 1855
Genera

Aeretes
Aeromys
Belomys
Biswamoyopterus
Eoglaucomys
Eupetaurus
Glaucomys
Hylopetes
Iomys
Petaurillus
Petaurista
Petinomys
Priapomys
Pteromys
Pteromyscus
Trogopterus

Contents

Flying squirrels (scientifically known as Pteromyini or Petauristini) are a tribe of 50 species of squirrels in the family Sciuridae. Despite their name, they are not in fact capable of full flight in the same way as birds or bats, but they are able to glide from one tree to another with the aid of a patagium, a furred skin membrane that stretches from wrist to ankle. Their long tails also provide stability as they glide. [1] Anatomically they are very similar to other squirrels with a number of adaptations to suit their lifestyle; their limb bones are longer and their hand bones, foot bones, and distal vertebrae are shorter. Flying squirrels are able to steer and exert control over their glide path with their limbs and tail.

Molecular studies have shown that flying squirrels are monophyletic (of one phylum/ clade with no branching within the phylum) and originated some 18–20 million years ago. The genus Paracitellus is the earliest lineage to the flying squirrel dating back to the late Oligocene era. [1] Most are nocturnal and omnivorous, eating fruit, seeds, buds, flowers, insects, gastropods, spiders, fungi, bird's eggs, tree sap and young birds. The young are born in a nest and are at first naked and helpless. They are cared for by their mother and by five weeks are able to practice gliding skills so that by ten weeks they are ready to leave the nest.

Some captive-bred southern flying squirrels have become domesticated as small household pets, a type of "pocket pet". [2]

Description

A northern flying squirrel (Glaucomys sabrinus) gliding Flying squirrel in a tree.jpg
A northern flying squirrel (Glaucomys sabrinus) gliding

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 metres (300 ft). [3] [4] The direction and speed of the animal in midair are varied by changing the positions of its limbs, largely controlled by small cartilaginous wrist bones. There is a cartilage projection from the wrist that the squirrel holds upwards during a glide. [5] This specialized cartilage is only present in flying squirrels and not other gliding mammals. [6] Possible origins for the styliform cartilage have been explored, and the data suggests that it is most likely homologous to the carpal structures that can be found in other squirrels. [6] This cartilage along with the manus forms a wing tip to be used during gliding. After being extended, the wing tip may adjust to various angles, controlling aerodynamic movements. [7] [8] The wrist also changes the tautness of the patagium, a furry parachute-like membrane that stretches from wrist to ankle. [8] 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. [9]

Similar gliding animals

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.

Evolutionary history

Prior to the 21st century, the evolutionary history of the flying squirrel was frequently debated. [10] This debate was clarified greatly as a result of two molecular studies. [11] [12] 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. [13]

Several hypotheses have attempted to explain the evolution of gliding in flying squirrels. [14] One possible explanation is related to energy efficiency and foraging. [15] [5] 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. [15] By gliding at high speeds, flying squirrels can rummage through a greater area of forest more quickly than tree squirrels. Flying squirrels can glide long distances by increasing their aerial speed and increasing their lift. [5]

Other hypotheses state that the mechanism evolved to avoid nearby predators and prevent injuries. If a dangerous situation arises on a specific tree, flying squirrels can glide to another, and thereby typically escape the previous danger. [5] [16] 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. [5] Yet the gliding mechanism of flying squirrels involves structures and techniques during flight that allow for great stability and control. If a leap is miscalculated, a flying squirrel may easily steer back onto the original course by using its gliding ability. [5] A flying squirrel also creates a large glide angle when approaching its target tree, decreasing its velocity due to an increase in air resistance and allowing all four limbs to absorb the impact of the target. [5] [17]

Fluorescence

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. [18]

Taxonomy

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

The Mechuka, Mishmi Hills, and Mebo giant flying squirrels were discovered in the northeastern state of India of Arunachal Pradesh in the late 2000s. [20] [21] [22] Their holotypes are preserved in the collection of the Zoological Survey of India, Kolkata, India.

Fossil species

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. [23]

Life cycles

A southern flying squirrel (Glaucomys volans) gliding Gliding flying squirrel.jpg
A southern flying squirrel (Glaucomys volans) gliding

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. [3] 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, [25] since they are not adept at escaping birds of prey that hunt during the daytime. [3] 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.[ citation needed ]

Reproduction

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. [26]

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. [27]

Diet

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. [3] [28] [4] Many gliders have specialized diets and there is evidence to believe that gliders may be able to take advantage of scattered protein deficient food. [29] Additionally, gliding is a fast form of locomotion and by reducing travel time between patches, they can increase the amount of foraging time. [29]

See also

Related Research Articles

<span class="mw-page-title-main">Squirrel</span> Family of rodents

Squirrels are members of the family Sciuridae, a family that includes small or medium-sized rodents. The squirrel family includes tree squirrels, ground squirrels, and flying squirrels. Squirrels are indigenous to the Americas, Eurasia, and Africa, and were introduced by humans to Australia. The earliest known fossilized squirrels date from the Eocene epoch, and among other living rodent families, the squirrels are most closely related to the mountain beaver and dormice.

<span class="mw-page-title-main">Western woolly flying squirrel</span> Species of rodent

The western woolly flying squirrel is a species of very large flying squirrel in the genus Eupetaurus. It is native to northern Pakistan and northwestern India. It was long considered the only species in the genus until the description of two other species in 2021. Until recently, scientific knowledge of this rare species was limited to 11 skins collected in the late nineteenth century. However, recent research has confirmed that it remains in Kashmir. It is among the longest members of the family Sciuridae, and one of the biggest gliding animals known. Observations confirm that despite its size, it does glide effectively, like other flying squirrels.

<span class="mw-page-title-main">Southern flying squirrel</span> Species of rodent

The southern flying squirrel or the assapan is one of three species of flying squirrel found in North America. It is found in deciduous and mixed woods in the eastern half of North America, from southeastern Canada to Florida. Disjunct populations of this species have been recorded in the highlands of Mexico, Guatemala, and Honduras.

<span class="mw-page-title-main">Northern flying squirrel</span> Species of rodent

The northern flying squirrel is one of three species of the genus Glaucomys, the only flying squirrels found in North America. They are found in coniferous and mixed coniferous forests across much of Canada, from Alaska to Nova Scotia, and south to the mountains of North Carolina and west to Utah in the United States. They are light brown with pale underparts and grow to a length of 25 to 37 cm. They are proficient gliders but uncoordinated walkers on the ground. They feed on a variety of plant material as well as tree sap, fungi, insects, carrion, bird eggs and nestlings. They mostly breed once a year in a cavity lined with lichen or other soft material. Except when they have young, they change nests frequently, and in winter a number of individuals may huddle together in a shared nest. Unlike most members of their family, flying squirrels are strictly nocturnal.

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Sciurinae is a subfamily of squirrels, uniting the flying squirrels with certain related tree squirrels. Older sources place the flying squirrels in a separate subfamily (Pteromyinae) and unite all remaining sciurids into the subfamily Sciurinae, but this has been strongly refuted by genetic studies.

Robot locomotion is the collective name for the various methods that robots use to transport themselves from place to place.

<span class="mw-page-title-main">New World flying squirrel</span> Genus of rodents

The three species of New World flying squirrels, genus Glaucomys, are the only species of flying squirrel found in North America. They are distributed from Alaska to Honduras. They are similar in many ways to the Eurasian flying squirrels in the genus Pteromys. Two species of New World flying squirrels can be easily distinguished on the basis of size and ventral pelage. Northern flying squirrels, Glaucomys sabrinus are larger and have belly hair that is dark at the base and white at the tip. Southern flying squirrels, Glaucomys volans, are smaller and have belly hairs that are completely white. Humboldt's flying squirrel is more difficult to distinguish from the northern flying squirrel where their ranges overlap. In fact, they were once considered conspecific. Humboldt's flying squirrel is considered a cryptic species. They are generally smaller and darker than northern flying squirrels.

<i>Biswamoyopterus</i> Genus of rodents

Biswamoyopterus is a genus of rodent in the family Sciuridae. It contains three known species of very large flying squirrels, with B. laoensis being among the longest of all squirrels. They are distributed in forests in northeast India, southwest China and Laos. Despite their size, species in this genus tend to be very elusive; due to this, all of them have been described relatively recently. In fact 2 out of the 3 species are only known from a single specimen. Additionally, they are easily confused with certain Petaurista giant flying squirrels that are more common and overlap in range with the rare Biswamoyopterus.

<span class="mw-page-title-main">Namdapha flying squirrel</span> Species of rodent

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<span class="mw-page-title-main">Red giant flying squirrel</span> Species of rodent

The red giant flying squirrel or common giant flying squirrel is a species of rodent in the family Sciuridae (squirrels). It is found in a wide variety of forest–types, plantations and more open habitats with scattered trees in Southeast Asia, ranging north to the Himalayas and southern and central China. One of the largest arboreal squirrels, all populations have at least some reddish-brown above and pale underparts, but otherwise there are significant geographic variations in the colours. The taxonomic position of those in the Sundaic region is generally agreed upon, but there is considerable uncertainty about the others, which variously have been included in this or other species, or recognized as their own species.

The Kashmir flying squirrel is a species of rodent in the family Sciuridae. It is monotypic within the genus Eoglaucomys. It is found in Afghanistan, India and Pakistan. Its natural habitat is subtropical or tropical dry forests. It is threatened by habitat loss. The Afghan flying squirrel is usually considered a subspecies.

<span class="mw-page-title-main">Red and white giant flying squirrel</span> Species of rodent

The red and white giant flying squirrel is a species of rodent in the family Sciuridae. It is a very large, dark rufous-red, buff and white flying squirrel found in forests at altitudes of 800–3,500 m (2,600–11,500 ft) in mainland China and 1,200–3,750 m (3,940–12,300 ft) in Taiwan, although the population of the latter island is distinctive and likely better regarded as a separate species, the Taiwan giant flying squirrel. Additionally, the red and white giant flying squirrel possibly ranges into northeastern South Asia and far northern Mainland Southeast Asia. This squirrel has a wide range and is relatively common, and the International Union for Conservation of Nature lists it as being of "least concern".

<i>Petaurista</i> Genus of rodents

Petaurista is a genus of rodent in the family Sciuridae. They are large to very large flying squirrels found in forests and other wooded habitats in southern and eastern Asia.

<span class="mw-page-title-main">Spotted giant flying squirrel</span> Species of rodent

The spotted giant flying squirrel, also known as the lesser giant flying squirrel, is a species of rodent in the family Sciuridae. It is found in hill and mountain forests at altitudes of 200–4,000 m (660–13,120 ft) in Southeast Asia north to central China and the east Himalayan region, although the northern populations sometimes are regarded as separate species as the grey-headed giant flying squirrel, Chindwin giant flying squirrel and P. marica. Two of these, as well as a few other populations, lack the white spots on the upperparts for which it is named. Although a large flying squirrel, it is a relatively small giant flying squirrel.

<span class="mw-page-title-main">Hodgson's giant flying squirrel</span> Species of rodent

Hodgson's giant flying squirrel is a species of rodent in the family Sciuridae. This large flying squirrel lives in Himalayan forests in Asia. Like other flying squirrels, it is nocturnal and able to glide long distances between trees by spreading out its patagium, skin between its limbs.

<span class="mw-page-title-main">Bhutan giant flying squirrel</span> Species of rodent

The Bhutan giant flying squirrel, also known as the Gray's giant flying squirrel or noble giant flying squirrel, is a species of rodent in the family Sciuridae. This species lives in Himalayan forests and it is one of the largest flying squirrels. Like other flying squirrels, it is mainly nocturnal and able to glide long distances between trees by spreading out its patagium, skin between its limbs.

<span class="mw-page-title-main">Indian giant flying squirrel</span> Species of rodent

The Indian giant flying squirrel, also called the large brown flying squirrel or the common giant flying squirrel, is a species of rodent in the family Sciuridae. It is capable of gliding flight using a skin membrane, the patagium, stretched between front and hind legs. It is found in mainland Southeast and South Asia, and southern and central China.

<span class="mw-page-title-main">Japanese dwarf flying squirrel</span> Species of rodent

The Japanese dwarf flying squirrel is one of two species of Old World flying squirrels in the genus Pteromys. During the day, this squirrel hides in a hole, usually in a coniferous tree, emerging at night to feed.

The Mechuka giant flying squirrel is a species of rodent in the family Sciuridae. First described in 2007 from East Himalayan forests at altitudes of 1,500–2,500 m (4,900–8,200 ft) in the region of Mechuka of north-central Arunachal Pradesh in India, its taxonomic status and position is not fully resolved. it was originally described as P. nigra but has been replaced by mechukaensis because it was a primary homonym of P. nigra Wang 1981.

<span class="mw-page-title-main">Ezo flying squirrel</span> Subspecies of mammal

The Ezo flying squirrel or Ezo-momonga is a subspecies of the Siberian flying squirrel. It is endemic to Hokkaidō, Japan, part of the region once known as Ezo. In the legends of the local Ainu, the Ezo flying squirrel or A-kamui is a tutelary deity of children. Together with the Ezo chipmunk and Ezo squirrel, it is one of the three sciurids found on the island, to the north of Blakiston's Line, each having its own particular ecological niche.

References

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  29. 1 2 Byrnes, G.; A.J. Spence (2011). "Ecological and biomechanical insights into the evolution of gliding in mammals". Integrative and Comparative Biology. 51 (6): 991–1001. doi: 10.1093/icb/icr069 . PMID   21719434.

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