Northern flying squirrel
The northern flying squirrel (Glaucomys sabrinus) is a small, nocturnal rodent of the family Sciuridae, distinguished by its patagium—a furred membrane extending from wrist to ankle that enables gliding flights of up to 20 meters between trees.[1] Adults typically measure 25 to 37 cm in total length, including a flattened tail used for steering, and weigh 75 to 140 grams, with dense grayish-brown fur above and pale undersides.[2] Native to coniferous and mixed-forest habitats across North America, from Alaska and Canada southward to the Appalachian and Rocky Mountains, the species thrives in old-growth stands with closed canopies that provide nest sites in tree cavities and abundant hypogeous fungi for food.[3] Its diet is primarily mycophagous, consisting of truffles, lichens, seeds, nuts, and occasional insects or buds, with individuals caching fungi in tree branches during winter.[2][4] Highly arboreal and solitary outside breeding seasons, northern flying squirrels exhibit territorial behavior among females and communicate via vocalizations and scent marking, with lifespans averaging 4-5 years in the wild.[1][5] Classified as Least Concern globally by the IUCN due to its wide distribution, the species faces localized threats from habitat fragmentation and fire suppression in some regions, though populations remain stable in expansive boreal forests.[6] Certain subspecies, such as the Carolina northern flying squirrel, warrant conservation attention owing to restricted high-elevation habitats vulnerable to climate shifts and logging.[4]Taxonomy and systematics
Etymology and classification
The genus name Glaucomys is derived from the Ancient Greek glaukos, meaning "silver" or "grayish-blue," and mys, meaning "mouse," alluding to the animal's gray fur and its membership in the rodent order.[7][8] The specific epithet sabrinus stems from the Latin Sabrina, the classical name for the River Severn in Britain, which may reference the species' type locality near Hudson Bay or its affinity for moist, forested environments reminiscent of riverine habitats.[9] The common English name "northern flying squirrel" differentiates the species from its congener, the southern flying squirrel (Glaucomys volans), while "flying" describes its patagium-enabled gliding locomotion, though the animal lacks the capacity for powered flight.[7]| Taxonomic Rank | Name |
|---|---|
| Kingdom | Animalia |
| Phylum | Chordata |
| Class | Mammalia |
| Order | Rodentia |
| Family | Sciuridae |
| Tribe | Pteromyini |
| Genus | Glaucomys |
| Species | G. sabrinus |
Subspecies and genetic variation
The northern flying squirrel (Glaucomys sabrinus) is classified into 25 subspecies, primarily distinguished by morphological traits such as pelage color, body size, and cranial measurements, with distributions spanning from Alaska to the Appalachian Mountains.[9] Notable subspecies include G. s. coloratus, endemic to high-elevation spruce-fir forests in the southern Appalachians of North Carolina and Tennessee, which faces threats from habitat loss and is listed as endangered under the U.S. Endangered Species Act; G. s. fuscus, occurring in mixed conifer-hardwood forests of Virginia, West Virginia, and adjacent areas; and G. s. yukonensis, found in boreal forests of Alaska and Yukon, characterized by larger size and paler fur compared to the nominate form.[12][13][7] Subspecies boundaries often align with geographic barriers like major river valleys or mountain ranges, reflecting historical isolation during Pleistocene glaciations.[14] Genetic analyses, primarily using mitochondrial DNA such as cytochrome b sequences, support the validity of certain subspecific designations while highlighting isolation-driven divergence. For instance, the Prince of Wales Island population (G. s. griseifrons) in Alaska exhibits mitochondrial sequence divergence consistent with its subspecific status, with reduced gene flow from mainland populations.[15] Insular populations along the North Pacific Coast, including those on islands off British Columbia and Alaska, display significantly lower genetic variation and higher inbreeding coefficients compared to continental counterparts, attributed to founder effects and limited dispersal across marine barriers.[16] In contrast, mainland and Appalachian populations, such as those of G. s. fuscus and G. s. coloratus, maintain relatively higher heterozygosity and allelic diversity, though fragmented habitats have led to localized bottlenecks in some areas.[17][18] Nuclear microsatellite studies corroborate these patterns, indicating ongoing gene flow within subspecies but elevated differentiation (F_ST values up to 0.25) between isolated groups, underscoring the role of habitat connectivity in preserving variation.[19]Physical characteristics
Morphology and size
The northern flying squirrel (Glaucomys sabrinus) possesses a compact body covered in soft, dense, silky fur that is grayish-brown to cinnamon brown dorsally and paler, often whitish, ventrally, with the belly hairs featuring gray bases and white tips that are flattened.[1][7] Its head is relatively large with a short snout, prominent large black eyes adapted for nocturnal vision exhibiting reddish-orange eye shine, and small, rounded ears partially concealed by fur.[1][7] The limbs are short, with the forelimbs and hindlimbs connected by a furred patagium—a thin membrane extending from the wrists to the ankles—that enables gliding, supported structurally by an elongated styloid process on the wrist.[1] The tail is long, bushy yet laterally flattened with distichous (two-ranked) hairs giving a feather-like appearance, comprising approximately 80% of the head-body length and aiding in steering during glides.[1] There is minimal sexual dimorphism in size or morphology, though males may average slightly larger in some populations.[1] Subspecies exhibit minor variations, such as the Carolina northern flying squirrel (G. s. coloratus) having somewhat reduced size in certain metrics compared to northern mainland forms.[1] Adult size varies regionally but generally falls within the following ranges:| Measurement | Range |
|---|---|
| Total length | 275–342 mm |
| Weight | 75–140 g |
| Tail length | 108–160 mm (approx. 80% of head-body) |
| Hindfoot length | 34–40 mm |