The Japanese dormouse is a nocturnal rodent that spends the night ranging over a relatively large area searching for food, with males covering greater distances than females (2) (4). It is an agile climber and spends the vast majority of its time in trees, feeding on seeds, fruits, insects and birds' eggs (2). Dormice are the only rodents to lack a cecum, which indicates the lack of cellulose in their diet. The daytime is spent in round nests, constructed from bark and covered on the outside with lichens (2). Generally, these nests are situated in tree cavities, but they can also be found in shallow underground sites or in rock crevices (4). A defining feature of dormice is their long hibernation period, which gave rise to their name; 'dormeus' is an Anglo-Norman word meaning sleepy one. They accumulate layers of fat prior to hibernation, which can last for up to seven months. As soon as they emerge from hibernation, dormice will begin to mate (3). They have a well developed ability to vocalize, which plays an important part in mating. Gestation lasts for about one month, after which an average of four naked and blind young are born in June or July (2) (3). After around 18 days the young open their eyes and are able to hear, and after four to six weeks, they become independent. Sexual maturity is reached after one year, and dormice live for between three and six years (3).

Dormice are the intermediates, in form and behaviour, between mice and squirrels, and this attractive Japanese dormouse is the only species in the genus Glirulus (3). It has soft and thick, pale olive brown fur, with a dark brown or black stripe running along its back. In front of the ears is a tuft of longer hair, and the bushy tail is flattened from top to bottom (2). The four digits of the forefeet and the five digits of the hindfeet have short, curved claws, and the undersides of the feet have a cushion-like covering, all enabling the dormouse to grip to branches and move around trees with great agility (3).

This species is endemic to Japan, where it is found on Honshu, Shikoku, Kyushu, and Dogo Island (Oki Islands).

Japanese dormice are found on the Japanese islands of Honshuu, Shikoku, and Kyuushuu.

Biogeographic Regions: oriental (Native )

Other Geographic Terms: island endemic

Occurs on the Japanese islands of Honshu, Shikoku, and Kyushu (2)

Japanese dormice are similar in appearance to both mice and squirrels. They have a thick layer of soft, hazel or brown fur with a dark brown or black dorsal stripe. They have tufts of hair on the anterior side of the ears and the tail is bushy and flattened dorsally. The hindfeet have four digits and the forefeet have five, all of which have short, hinged claws accompanied by soft pads that enable them to swiftly run along the underside of hanging tree limbs. Japanese dormice, like other dormice, hibernate during cold weather or times of little food. The sexes are alike, ranging in mass from 14 to 40 g and 105 to 135 mm head and body length.

Range mass: 14 to 40 g.

Range length: 105 to 135 mm.

Other Physical Features: endothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes alike

Habitat and Ecology

Systems

• Terrestrial

Japanese dormice live in a variety of habitats. They are arboreal and mostly found in deciduous and coniferous forests at medium to high elevations, between 400 and 1800 meters. Populations of Japanese dormice have also been found in arid areas, mountains, and in lower elevation, warm forests.

Range elevation: 400 to 1800 m.

Average elevation: 900 m.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: forest ; rainforest ; scrub forest ; mountains

The Japanese dormouse inhabits mountain forests, generally at elevations between 400 and 1,800 meters (2).

Japanese dormice are omnivorous, eating seeds, fruit, insects, and bird eggs. They store food in their nesting areas for later use.

Animal Foods: eggs; insects

Plant Foods: seeds, grains, and nuts; fruit

Foraging Behavior: stores or caches food

Primary Diet: omnivore

Japanese dormice are important in their native ecosystems because they eat large quantities of insects, especially during insect population outbreaks. Their role in distributing seeds of fruiting plants it also noted. Otherwise, little is documented concerning the ecological roles of this species.

Ecosystem Impact: disperses seeds

Little is known about predators of Japanese dormice. They tend to live at low population densities and are not a reliable or abundant source of food for many potential predators. Their modified suspensory locomotion and nocturnal habits enable them to move through forests relatively unnoticed.

Anti-predator Adaptations: cryptic

Japanese dormice rely heavily on olfaction and mark their nests with urine in order to establish territory. They use tactile cues extensively when getting around their arboreal habitats at night. When they emerge from hibernation in the spring, they produce loud vocalizations that enable them to locate potential mates.

Communication Channels: tactile ; acoustic ; chemical

Other Communication Modes: duets ; scent marks

Perception Channels: visual ; acoustic

Japanese dormice have an average life span in the wild of between 3 and 5 years. The longest lifespan recorded for a Japanese dormouse is 6 years.

Range lifespan

Status: wild: 6 (high) years.

Typical lifespan

Status: wild: 3 to 5 years.

Maximum longevity: 7 years (captivity)

Japanese dormice are generally solitary. In May, males emerge from hibernation to find a mate, relying heavily on their well developed ability to vocalize. Females respond to the vocalizations of males with their own calls. Males mate with several females, as their home range often encompasses the home range of several females.

Mating System: polygynous

Japanese dormice mate in the late spring to early summer. Gestation lasts for about a month and an average of 4 young are born between the months of June and July. Young are weaned after about 18 days, reaching independence at around 4 to 6 weeks old. Sexual maturity is attained at around 1 year.

Breeding interval: Japanese dormice breed actively in the spring and early summer

Breeding season: Breeding occurs between the months of May and June.

Range number of offspring: 2 to 6.

Range gestation period: 4 to 6 weeks.

Range weaning age: 15 to 21 days.

Range time to independence: 4 to 6 weeks.

Average age at sexual or reproductive maturity (female): 1 years.

Average age at sexual or reproductive maturity (male): 1 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Japanese dormice have relatively low parental investment per offspring because of their large litter sizes. Young are weaned at around 18 days and become completely independent between 4 and 6 weeks old. Males have no involvement with their offspring after copulation. Females provide all the care necessary to ensure that their young survive until independence.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)

The IUCN lists Glirulus japonicus as least concern. The Ministry of Japan has designated Japanese dormice as an endangered National Monument and their habitats are under government protection throughout Japan.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Classified as Endangered by the IUCN Red List 2007 (1).

Population

Population Trend

Major Threats

Whilst dormice are naturally found at far lower densities than other rodent groups (3), this natural scarcity has been exacerbated by the activities of humans. The primary cause of decline of the Japanese dormouse in the past, and the greatest continuing threat, is habitat loss. The montane forests of Honshu, Shikoku, and Kyushu Islands have declined greatly in the past. Remaining tracts of forest continue to be threatened by logging, road construction, and the development of tourist facilities (5).

Conservation Actions

The Japanese dormouse has been designated a Natural Monument, meaning that the Commissioner for Cultural Affairs must approve any changes to the habitat of this species or any actions that would affect the preservation of the species (6). The Japanese dormouse occurs within the Shirakami-Sanchi Natural World Heritage Site and Nature Conservation Area. Situated in the mountains of northern Honshu, it is a remote area unaffected by man (7). The Kiyosato Educational Experiment Project (KEEP) runs a museum dedicated to the Japanese dormouse, and runs programs and classes to educate the public about this endangered species, carries out research, and encourages the protection of critical dormouse habitat (8).

There are no known adverse effects of Glirulus japonicus on humans.

Japanese dormice are avid insect predators and their presence in ecosystems helps to control populations of insects. In Japan, agriculture is particularly vulnerable to locusts, and Japanese dormice help control seasonal swarms of such insects.

Positive Impacts: controls pest population