The red giant flying squirrel or common giant flying squirrel (Petaurista petaurista) 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.
Like other flying squirrels, the red giant flying squirrel is mostly nocturnal and able to glide (not actually fly like a bat) long distances between trees by spreading out its patagium, skin between its limbs. It is a herbivore and the female has one, infrequently two, young per litter. Although declining locally due to habitat loss and to a lesser degree hunting, it remains overall common and it is not a threatened species.
Distribution, appearance and taxonomy The red giant flying squirrel is among the largest flying squirrels and longest squirrels. It has a head–and–body length of , tail length of and weighs about . Within each region, males are generally somewhat smaller, at least in weight, than females.
It varies considerably in appearance depending on subspecies and location. Roughly, it can be divided into the following subspecies groups, some of which variously have been regarded as part of this species, the Indian giant flying squirrel (P. philippensis), the red and white giant flying squirrel (P. alborufus) or the spotted giant flying squirrel (P. elegans), or their own separate species. Up until the 1980s, some authorities even listed the Indian giant flying squirrel itself as a subspecies of the red giant flying squirrel.
Nominate subspecies group
The red giant flying squirrel sensu stricto is the nominate subspecies group (P. p. petaurista and most other subspecies, excluding those mentioned in later groups). The distribution of this group essentially equals the Sundaic region, including Java, Sumatra, Borneo, the Thai-Malay Peninsula, nearby smaller islands, and Singapore (last Singaporean record in 1986, possibly extirpated). They generally inhabit lowlands and foothills, typically below elevation.
Members of the nominate group are medium to dark reddish-brown above and the underparts, including the face, are light orangish-brown to buff. The tail is reddish-brown or orangish-brown and its tip is black. The feet/hands, rings around the eyes and area near the nose are black. The various subspecies in this group are generally quite similar, varying primarily in the exact hue of the upper- and underparts, and to a small degree their size. In the darkest, the upperparts have some black hairs intermixed with the reddish-brown. In Java, much of the tail (not just the tip) can be black. Two subspecies, terutaus from Ko Tarutao in the Andaman Sea off the Thai mainland and taylori from Tenasserim in southern Myanmar and adjacent western Thailand, are located roughly in between the nominate subspecies group and the barroni–candidula subspecies group. Although largely similar to the former group, they have some grizzling to the upperparts and more whitish to the head, thus approaching the latter group.
Although the members of the nominate subspecies group are quite similar and appear to be part of the same species, considerable taxonomic uncertainty exists for all populations (groups) outside the Sundaic region. Locally in Thailand, the nominate subspecies group and the barroni–candidula subspecies group are sympatric, leading some authors to recognize them as separate species. The other groups have ranges that are fully separated from the nominate subspecies group. Limited genetic data is available for the nominate subspecies group. A study in 2002 found that Bornean red giant flying squirrels (a part of the nominate group) were relatively closely related to a clade that contains the white-bellied (albiventer) and Yunnan giant flying squirrels (yunanensis subspecies group), but more distantly related to a clade that contains red giant flying squirrels from an unspecified location in southern China and perhaps Laos. Using several of the same samples, a genetic study in 2004 came to another result, finding that Bornean red giant flying squirrels were very closely related to the southern China population, but more distant to the white-bellied giant flying squirrel (albiventer). The same southern Chinese and perhaps Laos specimens have been used in other genetic studies in 2004–2006 where they were labelled as melanotus, a subspecies in the nominate group from the Thai-Malay Peninsula (far from China and Laos). Later studies that used these samples have typically only listed them as red giant flying squirrels from southern China and perhaps Laos without exact subspecies, although likely rufipes (at least in part) as all other groups found in southern China were listed separately. The southern China–perhaps Laos population is very close to the Formosan giant flying squirrel (grandis), but distant from the white-bellied giant flying squirrel (albiventer), Yunnan giant flying squirrel (yunanensis subspecies group) and other giant flying squirrel species. Based on these data, each of these could be regarded as its own species. Alternatively, the southern China–perhaps Laos population and Formosan giant flying squirrel could be regarded as subspecies of one species and the white-bellied and Yunnan giant flying squirrels as subspecies of another species; whether the nominate subspecies group is associated with the former or the latter is disputed. Merging the nominate subspecies group, southern China–perhaps Laos population, and the Formosan, white-bellied and Yunnan giant flying squirrels into a single species would however result in a strongly polyphyletic grouping.
Barroni–candidula subspecies group
The taxon barroni is found in central and southeastern Thailand and southern Laos. The taxon candidula is found in Myanmar, northern Thailand, and northeastern India (at least eastern Arunachal Pradesh, eastern Assam and Nagaland). Individuals in eastern Bangladesh are similar in their appearance, if not the same.
Members of the barroni–candidula subspecies group are chestnut-brown above with the central parts, from the nape to the rump, with many whitish hairs resulting in a grizzled appearance. The underparts, including the throat, are whitish. The black-tipped tail is buffy-grey (candidula) or grey-brown (barroni). Much of the head, including the cheeks and forehead, is grey-white, but with blackish-red rings around the eyes. This is overall similar to the very rare Namdapha flying squirrel (Biswamoyopterus biswasi), which has resulted in frequent misidentifications. Based on a small number of specimens, members of the barroni–candidula subspecies group are medium-large in size, with measurements in the mid to upper range of that reported for the red giant flying squirrel.
Since the 1950s, both barroni and candidula have generally been included either as subspecies or as synonyms in the red giant flying squirrel or the red and white giant flying squirrel. Despite the close similarity, barroni and candidula have otherwise frequently been treated very differently in terms of their taxonomy. For example, in 2005, Mammal Species of the World opted to regard candidula as a subspecies of the red giant flying squirrel, while barroni was regarded as a synonym of albiventer (albiventer being a subspecies of the red giant flying squirrel according to that review). In a review in 2012, albiventer was recognized as a separate species, but—partially affected by the review in 2005—opted to include barroni as a valid subspecies of it, although noting that its position requires further study. In contrast, candidula was considered a subspecies of the red and white giant flying squirrel based on its colours.
White-bellied giant flying squirrel
The white-bellied giant flying squirrel (albiventer) is from the western and central Himalayan region in northeastern Afghanistan, through northern Pakistan and northern India, at least to Nepal (formerly reported east to Yunnan in China, but this is now recognized as separate, see Yunnan giant flying squirrel). In Nepal it occurs at altitudes from , but in Pakistan from with the upper limit equalling the tree line.
Its upperparts are reddish-mahogany or reddish-chestnut with many whitish hairs resulting in a grizzled appearance. The underparts are pale buffy to whitish, and the throat and cheeks are whitish. The tail is brown, often with a black tip, and the feet/hands are blackish. Melanistic individuals are known from the Kaghan Valley in Pakistan. The white-bellied giant flying squirrel is medium-large in size, with measurements in the mid to upper range of those reported for the red giant flying squirrel.
Since the 1950s, most authorities placed albiventer as a subspecies of the red giant flying squirrel. In the early 2000s, several genetic studies revealed that albiventer is relatively closely related to the members of the yunanensis group, but quite distantly related to other giant flying squirrels. As a consequence, recent authorities often have recognized it as a separate species, the white-bellied giant flying squirrel (P. albiventer), sometimes with barroni or members of the yunanensis group as its subspecies.
Yunnan giant flying squirrel The yunanensis subspecies group (including nigra, muzongensis and mechukaensis), often incorrectly modified to yunnanensis, is found in highlands of northeast India (at least northern and eastern Arunachal Pradesh), far northwestern Yunnan and southeastern Tibet in China, Myanmar, northern Laos and northern Vietnam, although the extent of its range in the last three countries is labelled with considerable uncertainty.
Members of this group have dark reddish-chestnut upperparts, darker towards the upper back and head, a blackish tail with a greyish or reddish-chestnut base, and brown-black feet/hands, muzzle and around the eyes. The underparts are light ochraceous-buff and the throat is whitish. In yunanensis, the central upperparts, from the top of the head and shoulders to the rump, have extensive scattered creamy-white guard hairs resulting in a grizzled appearance. In nigra, this is of more limited extent, mostly on the mid and lower back. In muzongensis and mechukaensis, this is essentially absent. Despite being distantly related, yunanensis is easily confused with the rare Mount Gaoligong flying squirrel (Biswamoyopterus gaoligongensis). Members of the yunanensis subspecies group are medium-large in size, with measurements in the mid to upper range of that reported for the red giant flying squirrel.