Dormouse

Dormouse is the common term that is used to describe the members of the Gliridae family. This family is also commonly known as Myoxidae or Muscardinidae by different taxonomic scientists. Dormouse is found in geographical locations like Asia, Africa and Europe. In Asia, Japan holds the most species diversity of these animal groups. The most intriguing feature about this animal is its hibernating nature. 

As the name suggests, these animals are categorized as rodents, the family  Gliridae consists of about 27 species that are termed dormouse. The body of the mouse is known to be of medium size. The weight of the body varies according to species. The smallest classified dormouse that belongs to the species Glirulus japonicus can weigh a maximum of up to 40 grams. The size of the body is not more than 8 centimetres. The largest dormouse can weigh up to 180 grams. 

The species diversity of these animals is not too large as there are only about 27 species that are termed as dormouse, but it is important to note that these species have unique ecological adaptations and lifestyles. Although all the 27 species are collectively termed as dormouse they are not essentially classified in the same genus. It is also noteworthy that these species may differ in anatomical features thus it is critical to understand the fact that two species of rodents might be called dormouse but they are not necessarily classified into the same genus and have the same anatomical adaptations. 

Apart from the anatomical modification and ecological adaptations, dormouse also differs from each other based on their use. For example species like the fat dormouse, the scientific name of the species is Glis glis, is known to be an edible species of a dormouse. They also differ in their habitat selection, some species of dormouse are categorized as arboreal species. The term is used to define animals that live on trees. An example of such a species is hazel dormouse, the scientific name of the species is Muscardinus avellanarius. 

The article focuses on the morphological and anatomical features of the animal. The article also encompasses the taxonomic classification system, habitat and reproduction of the species. Apart from this geographical range and food habits of the animal is also mentioned.

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Figure illustrating dormouse.

Taxonomic Classification

Dormouse rodents are classified into kingdom Animalia, the basic requirement to be classified under this kingdom is the multicellular organization of the body. The second to be classified under this kingdom is the presence of eukaryotic cell type, since dormouse meets the requirement they are rightfully categorized. The kingdom is further classified into phylum

Dormouse rodents belong to the Chordata phylum, the etymology of the phylum comes from the presence of notochord in the members. There are 5 requirements that are necessary to be classified as chordate, these synapomorphies are as follows, presence of the notochord, dorsal hollow nerve cord, endostyle or thyroid, pharyngeal slits, and a post-anal tail. These synapomorphies must be present during any stage of the life cycle. A critical feature is the presence of the bilaterally symmetrical body. A dormouse rodent has all the above-mentioned features. The phylum can be further classified into order.

Dormouse is classified into the order called Rodentia. It is because of this classification taxa that the animal is also referred to as a rodent or dormouse rodent.  The most intriguing feature of this order is the anatomical modification of the dentition of the buccal cavity. The term is used to describe the development and arrangement of the teeth in the buccal cavity (mouth). The incisor of rodents is very unique. They have a single pair of incisors in both the upper and lower jaw, these teeth can grow throughout the lifespan. The incisors are razor shaped and are used to hunt, they also have an enamel covering that protects the teeth. 

The order is further classified into suborders. Dormouse rodents are classified into the Sciuromorpha, the suborder consists of three families called Sciuridae, Aplodontiidae, and Gliridae. Among these dormice, rodents are classified into the family called Gliridae. The family contains various genus and species. 27 species are termed as dormouse, the example of such dormouse species is mentioned below.

• The edible dormouse, Glis glis

• Hazel dormouse, Muscardinus avellanarius

• Garden dormouse, Eliomys quercinus

• Forest dormouse, Dryomys nitedula

• Woodland dormouse, Graphiurus murinus

• Eurasian dormouse, Micromys minutus

• Japanese dormouse, Glirulus japonicus 

Morphological Features

They are considered small body size rodents. The length of the body ranges between 6 and 19 centimetres which when converted into inches is about 2.4 and 7.5 inches. The weight of the body ranges from 15 grams to 180 grams depending upon the species. The shape of these animals are similar to the mouse species, the resemblance can be seen in the dentition, colour and size of the body. Dormouse rodents are furry animals, they are also known for their long tail, the tail is covered with fur which is a distinctive property of the group as mouse species generally have a scaly tail. Dormouse is known to have large eyes, rounded ears, short legs and digits. An interesting point about the morphology is the size of the tail, this varies according to the species; the length of the tail can vary from 6 to 18 centimetre long. The colour of these animals also vary according to the species but they are mostly seen in grey, black and brown colour.

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Figure illustrating dormouse

Food Habits 

Dormouse rodents are classified as omnivorous animals. The term is used to classify animals that can derive their energy either from hunting other animals or from plant sources. The primary diet of the animal includes berries, flowers, fruits, insects, and nuts. They especially prefer eating flowers from oak, hawthorn, sycamore, willow, honeysuckle and bramble. The fruit that is primarily eaten by the rodent includes berries, apples, hazels. In the absence of the fruits, they also adapt to eat the bark and leaves of the tree. The carnivorous diet of the animal primarily includes the small invertebrate insects, like, caterpillars, aphids and wasp.

Habitat and Distribution

Dormouse rodents are easily adaptable animals, they are found in almost all countries. The suitable habitat for this animal is the geographical location that has a temperate climate, it is interesting to note that the only place that has no evidence of dormouse population is Antarctica. The major continents that have the highest species diversity are Asia, Africa and Europe. The typical habitat of a dormouse includes deciduous woodland, rainforests, deciduous forests, deserts, savannahs, and shrublands. The animal prefers to live near river banks and rocky outcrops and hide from predators in dense vegetation. They inhabit the sea level to the upper limits of such forests at 1,500 to 2,000 meters. They are frequently reported in deep caves. 

Behavioural Traits

Dormouse rodents maintain a social hierarchy in the population, these animals are usually sen in small groups. Although the number of members in the groups may vary there are rarely any species that follow a solitary lifestyle. The dominance in almost all the species of dormouse rodent is decided by the amount of the food source that a male has conjured, it is usually seen in species like Japanese dormouse and edile dormouse. 

Another interesting fact about their behaviour is that the male members of the species are more territorial and occupy more space than the female, the male is only involved in food foraging the parental care by the male members is minimal. 

Some of the species of the dormouse rodents are arboreal that is they spent their life on trees while the majority of the species lives in burrows and caves. An interesting fact about this animal is that irrespective of the species almost all the dormice are good climbers. 

Most of the species of dormouse rodents are nocturnal, that is they are most active after the sunset. These species are known to have different types of vocalization ranges, these are primarily used to communicate with each other.  

Hibernation

One of the main characteristics of dormouse rodents is their hibernation nature. They generally hibernate during the winters. Hibernation is that state in which the metabolic reactions of the body lowers to their minimal level. This is done to ensure the conservation of energy during harsh climatic conditions, this method was evolved in response to the survival challenges faced by an animal. This behavioural trait is mostly observed in the animals that face food scarcity. Dormuses that are particularly found in the temperate regions have developed this characteristic feature. The hibernation is done during the winter season, during summer the dormouse rodents gather a high level of body fat which is later used during hibernation as the fuel for the body.

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Figure illustrating hibernating dormouse

Reproduction

Dormouse are sexually reproducing organisms, the fertilization in these animals is internal, that is the male and female gametes fuse inside the female reproductive tract. They are viviparous animals, that is they produce offspring rather than laying eggs, this is a common feature of all the members of the Rodentia order. The gestation period in these animals varies according to species but the period ranges from 22 to 24 days. 

An important fact about the reproductive pattern of dormice is that they are seasonal breeders that are they mate only during a specific season. The mating season for dormice is late summers, the mating season begins in June and extends till late August or September. The most critical detail of their reproductive pattern is that both the male and female do not mate every year.

This interesting reproductive behaviour is rarely seen in rodents, this behaviour is attributed to the strong association between food availability and mating. According to experts the mating in dormice is only done when there is enough food supply to support the survival of litter.

Dormice are polygamous animals, that is they can mate with multiple partners. They have specifically termed a polygynous society. It is the term that is used to refer to the society where the male can mate with multiple females. The female choice in these species is based on the availability of food resources. 

The parental care is minimal in these species, the young offspring is reared only for 20 to 25 days, the offspring are born without hair and the eyes of the progeny open at 18 days, and the sexual maturity is typically attained after the first hibernation. The average lifespan of a dormouse is 13 years which is exceptionally high for rodents this can be attributed to the hibernating nature.

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Figure illustrating arboreal dormouse.

Predators 

There is a very small number of natural predators of these species, this is mainly because of their low population density in a given area, another reason for this might be the nocturnal nature of the animal. Although they are generally not predated some of the natural predators of different dormouse species include the following, owls, weasels, grey squirrels and cats. They are also hunted by badgers and wild boars. 

Fun Facts

• Dormouse rodents are capable of limited autonomy.

• They can regenerate their tail.

• Dormouse is considered exotic pets.

• These animals lack premolars.

• Some of the species like fat dormouse are considered a culinary delicacy in Rome.

• Dormouse is also considered unique among rodents because they lack cecum (part of the large intestine).

Summary: At a Glance

• They are classified under the family Gliridae.

• They are medium-sized animals that share a resemblance with mouse and squirrel species.

• They are found in black, brown, grey, golden and tan colours.

• The average body size of dormouse is 6cm - 19cm, they weigh about 15 to 200 grams.

• The most distinctive features include a long tail and thin, black whiskers.

• They are opportunistic omnivores.

• They are mostly found in Europe, Africa and Asia, the habitat includes dense woodlands and shrubland.

• They hibernate during winters.

• They are sexually reproducing polygynous animals.

• The litter size of dormouse rodents is 4 to 5 offspring.

• The natural predators are owls, snakes, weasels.