Flying squirrel

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This article is about the member of the animal kingdom. For other uses, see Flying squirrel (disambiguation).

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See also: Gliding possum
Flying squirrel
Temporal range: Early Oligocene – Recent
Glaucomys sabrinus.jpg
Northern flying squirrel (Glaucomys sabrinus)
Scientific classification
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
Neopetes[1]
Iomys
Petaurillus
Petaurista
Petinomys
Pteromys
Pteromyscus
Trogopterus

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Flying squirrels (scientifically known as Pteromyini or Petauristini) are a tribe of 44 species of squirrels (family Sciuridae).

Description

A flying squirrel 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 meters (295 ft).[2][3] 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. The wrist is connected to the styliform cartilage, which forms a wing tip used during gliding. After being extended, the wing tip may adjust to various angles, controlling aerodynamic movements.[4][5] The wrist also changes the tautness of the patagium, a furry parachute-like membrane that stretches from wrist to ankle.[5] 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.[6]

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.[7] This debate was clarified greatly as a result of two molecular studies.[8][9] 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. By comparing northern and southern flying squirrels to tree squirrels of similar size, flying squirrels show lengthening in bones, such as those of the lumbar vertebrae and forearm, while the feet, hands, and distal vertebrae are reduced in length relative to the tree squirrels. Such differences in body proportions reveal the flying squirrels’ adaptation to minimize wing loading and allow for more maneuverability while gliding.[10]

There are multiple hypotheses that attempt to explain the evolution of the gliding mechanism in flying squirrels.[11] One possible explanation is related to energy efficiency and foraging.[12][13] 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.[12] Flying squirrels are also able to rummage through a greater area of forest more quickly than tree squirrels due to gliding at high speeds. They are adapted to gliding long distances by increasing their aerial speed and producing more lift.[13] 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 have the ability to glide to another, typically assuring safety from the previous danger.[13][14] 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.[13] 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.[13] 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.[13][15]

Taxonomy

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

Three new species of flying squirrel have been found in the northeastern state of India of Arunachal Pradesh.[16][17][18] These are:

  • Mechuka giant flying squirrel (Petaurista mechukaensis)
  • Mishmi Hills giant flying squirrel (Petaurista mishmiensis)
  • Mebo giant flying squirrel (Petaurista siangensis)

Life cycles

A southern flying squirrel (Glaucomys volans) gliding

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.[2] 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,[19] since they are not adept at escaping birds of prey that hunt during the daytime.[2] 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.[20]

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.[21]

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.[2][22] Gliding conserves energy.[3] Many gliders have specialized diets and there is evidence to believe that gliders may be able to take advantage of scattered protein deficient food.[23] Additionally, gliding is a fast form of locomotion and by reducing travel time between patches, they can increase the amount of foraging time.[23]

See also

References

  1. ↑ 1.0 1.1 Daxner-Höck G. (2004). "Flying Squirrels (Pteromyinae, Mammalia) from the Upper Miocene of Austria". Annalen des Naturhistorischen Museums in Wien 106A: 387–423. PDF.
  2. ↑ 2.0 2.1 2.2 2.3 Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ 5.0 5.1 Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
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  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ 12.0 12.1 Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ 13.0 13.1 13.2 13.3 13.4 13.5 Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Choudhury, A.U. (2007). A new flying squirrel of the genus Petaurista Link from Arunachal Pradesh in north-east India. The Newsletter & Journal of the Rhino Foundation for nat. in NE India 7: 26–34, plates.
  17. ↑ Choudhury, A.U. (2009). One more new flying squirrel of the genus Petaurista Link, 1795 from Arunachal Pradesh in north-east India. The Newsletter & Journal of the Rhino Foundation for nat. in NE India 8: 26–34, plates.
  18. ↑ Choudhury, A.U. (2013). Description of a new species of giant flying squirrel of the genus Petaurista Link, 1795 from Siang Basin, Arunachal Pradesh in North East India. The Newsletter & Journal of the Rhino Foundation for nat. in NE India 9: 30–38, plates.
  19. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  20. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  21. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  22. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  23. ↑ 23.0 23.1 Lua error in package.lua at line 80: module 'strict' not found.

Further reading

  • Thorington, R. W. Jr. and R. S. Hoffman. 2005. Family Sciuridae. pp. 754–818 in Mammal Species of the World a Taxonomic and Geographic Reference. D. E. Wilson and D. M. Reeder eds. Johns Hopkins University Press, Baltimore.
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External links

mr:शेकरू

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