Ezo flying squirrel


The Ezo flying squirrel or Ezo-momonga is a subspecies of the Siberian flying squirrel. It is endemic to Hokkaidō, Japan, part of the region once known as Ezo. In the legends of the local Ainu, the Ezo flying squirrel or A-kamui is a tutelary deity of children. Together with the Ezo chipmunk and , it is one of the three sciurids found on the island, to the north of Blakiston's Line, each having its own particular ecological niche.

Taxonomy

The Ezo flying squirrel was first described by Nagamichi Kuroda in 1921, as Sciuropterus russicus orii. In 1940, John Reeves Ellerman elevated the Ezo flying squirrel to species rank and transferred it to the genus Pteromys, the new combination being Pteromys orii. In 1951, Ellerman and Morrison-Scott again treated the Ezo flying squirrel as a subspecies of the Siberian flying squirrel, under the combination Pteromys volans orii. The subspecific name honours Orii Hyōjirō, collector of the type specimen in "Uyenai", old Iburi Province, on 13 March 1920.

Description

The Ezo flying squirrel is a small arboreal rodent with a white belly and a back and tail that is dark brown in summer and is grey-brown in winter. Around the eyes, there is a ring of dark brown fur. Males are slightly longer in length than females, with male's body length being, and females about. The length of the body from head to tail is on average together. Tail length ranges from, the hind feet from, and the ears from. The body weight ranges from .

Distribution and habitat for living

While the Siberian flying squirrel at species level may be found across the coniferous forest zone from Finland and the Baltic to Korea, the Hokkaidō population is recognized as a distinct, endemic subspecies. On Hokkaidō, it inhabits the coniferous, broad-leaved deciduous, and mixed forests, both montane and lowland, and may also be found in windbreaks and groves in urban parks. Males may range over an area of some, while the home range of females is typically around. In Furano, population density has been estimated at two individuals per hectare.

Behaviour and ecology

The Ezo flying squirrel is nocturnal, typically leaving the nest to forage several times a night, from 15–20 minutes after sunset to 20–25 minutes before sunrise. It does not hibernate, but activity beyond the nest is reduced during winter; squirrels emerge once a day for food around daybreak. Lifespan in the wild rarely exceeds three years, but captive specimens can live for four or five years.

Locomotion

In a study of thirty-one squirrel glides in Obihiro, there was a mean horizontal gliding distance of, horizontal distances ranging from. The mean glide ratio was 1.70, with again a wide range of values, glide ratios ranging between 0.48 and 3.31. While the females were heavier than the males, there was no significant sex- or weight-related difference in glide distances or ratios.

Diet and predation

The Ezo flying squirrel is entirely herbivorous, feeding on leaves, buds, flowers, seeds, acorns, catkins, and fruits of both broad-leaf trees and conifers, with significant seasonal variation. In spring, young leaves form a major part of the diet, including those of willows, Japanese white birch, and East Asian alder ; in summer, cherries, mulberries, birch and maple seeds, and the unripe acorns of the daimyō oak and Mongolian oak ; prior to winter, in order to put on weight—and increase the chance of survival—there is increased foraging of highly nutritious pine nuts; during the winter, birch and alder leaves and buds are consumed.
Predators include the Ezo red fox, , Ural owl, Blakiston's fish owl, sparrowhawk, black kite, and domestic cat.

Nesting

Nests are in tree hollows and, on occasion, man-made bird boxes. A study of thirty-six winter nests found Sakhalin fir was the preferred choice, followed by the painted maple, Erman's birch, Mongolian oak, prickly castor oil tree, and Japanese walnut. The holes used for nests, most of which were located at least up the tree, heights ranging from, had typically originally been excavated by woodpeckers, or coincided with knots, frost cracks, and areas damaged by tree fungus. To line the nest, the finely shredded inner bark of vines such as yama-budō and dry moss are used. Repurposed nests include those of the great spotted woodpecker, Oriental turtle dove, and members of the crow family. In winter, deeper holes are preferred, and three to five individuals may share a single nest, to help keep warm.

Reproduction

There are two mating seasons, the first in late February/early March, the second in June. During this time, females have their own territory, while males overlap with each other and with more than one female. The litter size averages 3.3 kittens, ranging from two to six. Kittens weigh at birth and are red and hairless, their eyes and ears closed. Their digits, initially joined together, begin to separate one-by-one after ten to twelve days. Teeth in the lower jaw begin to appear after twenty days, and a week or so later in the upper jaw. Around thirty days after birth, the whole body is covered with fur. After 35 days, the eyes open. Movement of the back legs develops later than that of the front legs, after around twenty days; from around 28 days, kittens are able to walk using all four limbs. Approximately 40 days after birth, young leave the nest for the first time and begin to consume solid food. After around 50 days, kittens start to practise gliding. Young squirrels leave the nest and their parents around 60 days after birth.

Conservation

The Ezo flying squirrel is classed as a protected species. Forest fragmentation has been identified as a threat due to their method of locomotion.

Ainu culture

According to John Batchelor's account of the folklore of the Ainu of Hokkaidō, the flying squirrel—of the three Japanese flying squirrels, the Japanese giant flying squirrel, Japanese dwarf flying squirrel, and Ezo flying squirrel, the last is the only one to be found north of Blakiston's Line—was known as At-kamui or "the Divine prolific one", due to the belief that it could produce up to thirty young in one litter, and regarded as a bird, since it could fly. Where an Ainu man and his wife were childless, and initial appeal to the goddess of fire and her consort was to no avail, the husband, without his wife's knowledge, should go into the mountains to hunt for a flying squirrel, which he should then cut into small pieces, boil, and place upon a tray. Using Inau sticks, and praying to the sacrificed squirrel for assistance, he should give the meat to his wife to eat, again without her knowing from what "bird" it was derived. Only if this feast, known as uatama marapto or "the feast of placing the prolific one", proved unsuccessful should he resort to taking a second or third wife.