The Japanese dwarf flying squirrel (Pteromys momonga;
Japanese: ニホンモモンガ; Hepburn: Nihon
momonga) is one of two species of Old World flying squirrels in the genus
Pteromys. It is native to Japan where it inhabits sub-alpine forests and boreal
evergreen forests on Honshu and Kyushu islands. It grows to a length of 20 cm
(8 in) and has a membrane connecting its wrists and ankles which enables it to
glide from tree to tree. During the day this squirrel hides in a hole, usually
in a coniferous tree, emerging at night to feed on buds, leaves, bark, fruits
and seeds. This squirrel faces no particular threats, has a wide range and is
relatively common, and the International Union for Conservation of Nature lists
it as a "least-concern species".
Morphology
Its body is 14–20 cm long and the tail length is 10–14 cm.
It weighs 150–220 g. It is much smaller than the Japanese giant flying squirrel
which can reach 1500 g. Its back is covered with grey brown hair, and its belly
is white. It has large eyes and a flattened tail. Species of flying squirrels
possess a patagium, which is a skin membrane used in gliding. In this
particular species of flying squirrel their patagium spans between their wrists
and ankles, but not between their legs and tail.
Distribution
Range:
This species of flying squirrel inhabits sub-alpine forests
and boreal evergreen forests in Japan, specifically on Honshu and Kyushu
islands.
Habitat:
Japanese dwarf flying squirrels make their nests in the
cavities of trees, or at the cross point between branches and tree trunks.
These squirrels also tend to line their nests with mosses and lichens. Tree
cavities are very important nest resources for them. They tend to nest in
conifers, such as pine and spruce, more than broad-leaved trees.
Behavior
Feeding Behavior:
The Japanese dwarf flying squirrel is nocturnal, and during
the day it rests in holes in trees. It eats seeds, fruit, tree leaves, buds and
bark. It can leap from tree to tree using a gliding membrane called its
patagium. The patagium works as a wing suit enabling it to maneuver and glide
through the air.
When it feeds, the Japanese dwarf flying squirrel assumes a
hanging posture. It will pull a twig to its mouth with its forepaws if the twig
is not strong enough to support its weight and obtain food at the tip. While
picking up food scattered on the ground, it will extend its body in an
intermediate range around its body without moving its hind legs.
Social Behavior:
Multiple individuals of this species can be found grouped
together on a single tree, however usually these individuals tend to be of the
same sex when it is not mating season. Mating nests are usually shared by one
breeding pair.
Reproduction Behavior:
Not much is known about the specific mating rituals of these
squirrels. The squirrels tend to mate twice a year between the months of May
and July, with a gestation period of around 4 weeks. Litter size average about
2 to 3 young, but can have up to 5 pups. They are thought to develop similarly
to that of other flying squirrels, and are weaned by around 6 weeks of age.
Evolution
Japanese dwarf flying squirrels have evolved differently
from other Sciuridae. The differences between Japanese dwarf flying squirrels
and other Sciuridae is evident when comparing morphology of the mandible and
genetic code. The mandible of the Japanese dwarf flying squirrel does not have
a coronoid process unlike the American dwarf squirrels (Microsciurus). The
marmots (Marmota) also have a more elongated mandible than the Japanese dwarf
flying squirrel. This is due to phylogeny and ecology. There are also large
differences in chromosome structure between P. momonga and the only other
member of the genus Pteromys, Pteromys volans. Though they have the same number
of chromosomes (2n=38), their karyotypes differ extensively due to pericentric
inversions, tandem fusions, and deletion of large segments of the autosomes and
the Y chromosome. Because of these deletions, the P. volans genome contains
about fifteen percent less DNA than P. momonga. These findings suggest that the
karyotype of P. momonga more closely resembles the ancestor of P. volans and P.
momonga.
Reference: wikipedia
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