Petaurista leucogenys
Japanese giant flying squirrel

Japanese giant flying squirrels are found in southern parts of Asia and Japan, including the islands of Honshu, Kyushu and Shikoku in Japan. Many studies of this species have been carried out in Nara City, located in central Japan. (Ando and Shiraishi, 1993; Kawamichi, 1997a; Kawamichi, 1997b; Kawamichi, 1998; Stafford, et al., 2003)

This species inhabits areas of forests, hills and mountains. Forests include tropical and temperate with a mixture of tree species, such as deciduous and coniferous trees. They often inhabit forested areas around shrines and temples. (Ando and Shiraishi, 1993; Kawamichi, 1997a; Kawamichi, 1997b; Kawamichi, 1998; Nowak, 1997)

There are six species of giant flying squirrels, including the largest, Petaurista leucogenys. This species has long, soft fur ranging in color on its back from yellow-gray, brown, chestnut and black. The tail is usually longer than the body and is the color of the fur on the back. The ventral surface is yellow, buff, brown or white. A fur-covered membrane extends from the side of their body from the wrists to the ankles, which allows these squirrels to glide between trees. Flying squirrels generally have longer limbs than non-gliding squirrels. There are nine carpal bones in the wrist of this species, which has a special, long accessory styliform cartilage that supports the flying membrane while gliding. Japanese giant flying squirrels are the largest members of the family Sciuridae, weighing up to 1.3 kg. The skull is broad with distinct post-orbital processes and a short rostrum. The face is almost raccoon-like in color, with black bands around the eyes. Extending down from the ears on the side of the face are white bands of fur. The nose and lips are pink. (Kawamichi, 1997b; Nowak, 1997; Oshida, et al., 2000; Stafford, et al., 2003)

Mating behaviors are not well known for this species, but they are thought to be strictly monogamous, breeding and nesting with only one other mate. ("Squirrels and relatives I: Flying squirrels (Pteromyinae)", 2004; Nowak, 1997)

Japanese giant flying squirrels have two reproductive seasons annually; one is in the winter (mid-November to mid-January) and the other is in the summer (mid-May to mid-June). Gestation lasts for approximately 74 days. Because members of this species invest a great deal of energy in parental care, females give birth to only one or two offspring. In addition, breeding occurs twice yearly, resulting in up to four offspring in one year. Young Japanese giant flying squirrels are able to leave their nests at 59 or more days of age and begin foraging independently at 80 days of age. The young are sexually mature around 21 months and become independent at 12-18 months. However, female young disperse from their natal territories before they reach sexual maturity.

Because there are two breeding seasons, males born in the summer reach sexual maturity faster than males born in the spring. Spermatogenesis ceases in most males from July to August and from December to March, which is between the two mating seasons. The size of the testes regresses during these time periods. (Kawamichi, 1997a; Kawamichi, 1997b; Kawamichi, 1998)

It is not clear whether the male participates in raising young. Studies suggest that females allow their young to stay with them until they are sexually mature (1-1.5 years). After the young have emerged from their nest at 40 days, they begin following their mothers. Juveniles are able to glide a few days after their first emergence from their nests. Mothers return to their nests at night to feed the young. Whenever a juvenile falls from the nest, the mother returns them to the nest. The amount of care mothers invest in their offspring is believed to be associated with gliding, which takes coordination and muscle. (Ando and Shiraishi, 1985; Kawamichi, 1997b; Nowak, 1997)

Information on the lifespan of this species was not found.

Japanese giant flying squirrels are a nocturnal, strictly arboreal species. They almost never descend to the ground. They spend the daytime hours at rest in hollow trees and branches. At night these squirrels move among branches, gliding from tree to tree. In fact, their incredible gliding abilities allow them to utilize a variety of habitats. The fur-covered membrane that is connected from the forearms to the rear feet allows them to travel an average of 50 meters per glide. However, the longest recorded glide was 160.2 meters. These squirrels travel an average distance of 111-620 meters each night. Smaller glides are more advantageous for this species for two reasons. First, they are more efficient energetically, and second, they allow squirrels to visit more trees in search of food. Most species of flying squirrels are territorial, and the intensity of territoriality may increase during the breeding season. ("Squirrels and relatives I: Flying squirrels (Pteromyinae)", 2004; Ando and Shiraishi, 1983; Ando and Shiraishi, 1993; Ando, et al., 1985a; Stafford, et al., 2003)

Giant flying squirrels can have home ranges of up to 12 acres or 5 hectares. Japanese giant flying squirrels tend to have home ranges from 0.46 to 5.16 hectares. Adult females hold intra-sexual territories throughout the year. ("Squirrels and relatives I: Flying squirrels (Pteromyinae)", 2004; Ando and Shiraishi, 1993; Nowak, 1997)

Despite having a strictly nocturnal lifestyle, this species relies heavily on sight, although hearing, touch, and olfaction are also undoubtedly important. Members of this family display a variety of social behaviors. Flying squirrels are vocal, having very loud, high-pitched calls that are almost bird-like in sound. ("Squirrels and relatives I: Flying squirrels (Pteromyinae)", 2004)

Japanese giant flying squirrels have unique foraging behaviors that allow them to feed from the skinniest of branches. They are able to extend their bodies to reach distant branches without shifting the position of their hind feet. This behavior allows them to maneuver around branches in search of food. They use their forepaws to grab onto skinny branches that would otherwise be off limits. They eat a variety of food items: seeds, leaves, conifers, buds, fruits, flowers and woody plant parts. Availability of food determines diet choice; from March to May they mainly feed on buds, young leaves and flowers. In June through the month of October, they eat seeds, mature leaves and fruit. During the winter months they eat buds and cones. Their main diet consists of leaves during periods when other food is absent. Feeding usually begins 35 minutes after sunset. There are two feeding peaks during the night, but the second feeding peak is the most active. Body size, nocturnal feeding pattern, and home range size seem to have an impact on the foliage eating habits of this species. ("Squirrels and relatives I: Flying squirrels (Pteromyinae)", 2004; Ando, et al., 1984; Ando, et al., 1985b; Funakoshi and Shiraishi, 1985; Kawamichi, 1997a; Nowak, 1997)

The main threat to Japanese giant flying squirrels is humans. (Nowak, 1997)

As with most squirrels, this species is a good seed disperser.

Giant flying squirrels are hunted for food. ("Squirrels and relatives I: Flying squirrels (Pteromyinae)", 2004; Nowak, 1997)

Squirrels living in highly populated areas are rarely noticed by humans. However, in some areas they are considered a pest by local farmers. ("Squirrels and relatives I: Flying squirrels (Pteromyinae)", 2004)

Currently, the Japanese giant flying squirrel is not listed as endangered or threatened. However, there are two other species of giant flying squirrels that are endangered or threatened. (Kawamichi, 1998)