The three

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

of New World flying squirrels, genus ''Glaucomys'', are the only species of

flying squirrel 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 a ...

found in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

.Walker EP, Paradiso JL. 1975. ''Mammals of the World''. Baltimore: Johns Hopkins University Press.Forsyth A. 1999. ''Mammals of North America: Temperate and Arctic Regions''. Willowdale: Firefly Books. They are distributed from

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U ...

Honduras Honduras, officially the Republic of Honduras, is a country in Central America. The republic of Honduras is bordered to the west by Guatemala, to the southwest by El Salvador, to the southeast by Nicaragua, to the south by the Pacific Oce ...

. They are similar in many ways to the

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelag ...

n 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 Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket ...

Northern flying squirrel The northern flying squirrel (''Glaucomys sabrinus'') is one of three species of the genus '' Glaucomys'', the only flying squirrels found in North America.Walker EP, Paradiso JL. 1975. ''Mammals of the World''. Baltimore: Johns Hopkins Universit ...

s, ''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 In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each ot ...

. They are generally smaller and darker than northern flying squirrels.

Species

*Genus ''Glaucomys'' **''Glaucomys volans'' – southern flying squirrel **''Glaucomys sabrinus'' –

northern flying squirrel The northern flying squirrel (''Glaucomys sabrinus'') is one of three species of the genus '' Glaucomys'', the only flying squirrels found in North America.Walker EP, Paradiso JL. 1975. ''Mammals of the World''. Baltimore: Johns Hopkins Universit ...

**''Glaucomys oregonensis'' – Humboldt's flying squirrel

Gliding

Flying squirrels do not actually fly, but rather glide using a membrane called a

patagium The patagium (plural: patagia) is a membranous body part that assists an animal in obtaining lift when gliding or flight. The structure is found in extant and extinct groups of flying and gliding animals including bats, birds, some dromaeos ...

created by a fold of skin which starts at the wrists of the forearms, extends along the sides of the body, and finishes at the ankles of the hind legs. From atop of trees, flying squirrels can initiate glides from a running start or from a stationary position by bringing their limbs under the body, retracting their heads, and then propelling themselves off the tree.Banfield AWF. 1974. ''The Mammals of Canada''. Toronto: University of Toronto Press. It is believed that they use

triangulation In trigonometry and geometry, triangulation is the process of determining the location of a point by forming triangles to the point from known points. Applications In surveying Specifically in surveying, triangulation involves only angle me ...

to estimate the distance of the landing area as they often lean out and pivot from side to side before jumping. Once in the air, they form an "X" with their limbs by spreading their long arms forward and out and their long legs backward and out, causing their membrane to stretch into a square-like shape and glide down at angles of 30 to 40 degrees. They manoeuvre with great efficiency in the air, making 90 degree turns around obstacles if needed. Just before reaching a tree, they raise their flattened tails to abruptly change their trajectory upwards and point all of their limbs forward in order to create a

parachute A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, w ...

effect with the membrane. Upon landing, the limbs break the remainder of the impact and the squirrels usually run to the other side of the trunk in order to avoid any potential

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill t ...

s. They are very clumsy walkers and if they are on the ground in the presence of danger, they will prefer to hide rather than attempt an escape.

Fluorescence

Under ultraviolet light, females and males of all 3 species of ''Glaucomys'' fluoresce in varying intensities of pink on both dorsal and ventral surfaces. The fluorescence is hypothesized to help the flying squirrels find each other in low light and mimic the plumage of owls to evade predation. This hypothesis has been challenged by Toussaint et al. (2022) who instead suggest that the pink luminescence is a byproduct of the body's waste management. Moreover, these authors argue that it is far from evident that UV illuminating sources that occur naturally are sufficient to elicit luminescence distinguishable from ambient visible light. An ecological role for the pink luminescence is therefore not likely.

References

{{DEFAULTSORT:New World Flying Squirrel Glaucomys Extant Middle Pleistocene first appearances Taxa named by Oldfield Thomas