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Rodents

Rodents are an order of mammals. They have only one pair of incisors in the upper and lower jaws and like to gnaw on hard objects. Rodents are generally small, most of them are active at night or at dawn and dusk, and many species have strong reproductive capacity. Rodents account for about 40% to 50% of mammals. They can be said to be the most successful branch in the evolution of vertebrates. The number of individuals far exceeds the total number of all other groups. They are almost everywhere in the world except Antarctica and a few islands.


I. Introduction to Rodentia

1. General Characteristics:

  • Specialized Incisors: Rodents are characterized by a single pair of continuously growing, chisel-shaped incisors in both the upper and lower jaws. The enamel is typically only present on the front surface, keeping the edge sharp through the animal’s gnawing activities.

  • Reduced Dentition: Between the incisors and cheek teeth (premolars and molars), there is a conspicuous toothless gap (diastema). No canine teeth are present.

  • Dietary Diversity: Most rodents are herbivorous or omnivorous, feeding on seeds, nuts, fruits, leaves, and sometimes insects.

  • Global Distribution: Rodents are found almost everywhere on Earth except Antarctica, inhabiting a broad range of environments—from cold tundra to tropical rainforests, deserts, and grasslands.

2. Diversity and Abundance:

  • Rodentia is the largest order of mammals, comprising about 40% of all mammalian species. Over 2,500 rodent species have been described, illustrating their remarkable evolutionary success and adaptive radiation.


II. Evolutionary History

1. Origins and Fossil Record:

  • Rodents likely originated in the late Paleocene to early Eocene (approximately 56 million years ago). Early fossil rodents appear around the same time as early primates.

  • The Eocene saw the initial diversification and geographic spread of rodents.

2. Geographic Radiation:

  • Rodents dispersed across continents via land bridges and continental drift. Over millions of years, they adapted to diverse habitats, leading to remarkable variety: from burrowing naked mole-rats in Africa to tree-dwelling squirrels, semi-aquatic beavers, and jumping jerboas in arid regions.

3. Paleogene and Neogene Proliferation:

  • By the Oligocene and Miocene, many modern rodent families had emerged, setting the stage for today’s global distribution and immense diversity.


III. Classification Overview

The taxonomy of Rodentia is complex and continually refined. The traditional classification relies heavily on jaw and skull morphology and muscular arrangements. Below is a commonly referenced framework, which may differ slightly from more recent molecular-based classifications. It includes major suborders and families, with some representative genera or species.

Order Rodentia

SuborderSuperfamilyFamilyRepresentative Genera/Species
Sciuromorpha-Aplodontiidae (Sewellel)Mountain beaver (Aplodontia rufa)

-Sciuridae (Squirrels)Squirrels (Sciurus), Chipmunks (Tamias), Marmots (Marmota)

-Gliridae/Myoxidae (Dormice)Garden dormouse (Eliomys), Forest dormouse (Dryomys)
Castorimorpha-Castoridae (Beavers)North American beaver (Castor canadensis), Eurasian beaver (Castor fiber)

-Geomyidae (Pocket gophers)Geomys, Thomomys

-Heteromyidae (Kangaroo rats & relatives)Kangaroo rats (Dipodomys), Pocket mice (Perognathus)
Anomaluromorpha-Anomaluridae (Scaly-tailed squirrels)Scaly-tailed flying squirrels (Anomalurus)

-Pedetidae (Springhares)Springhare (Pedetes capensis)
MyomorphaDipodoidea (Jerboas & allies)Dipodidae (Jerboas)Jerboas (Jaculus), Birch mice (Sicista)

Muroidea (Mice, Rats, Hamsters, Voles)Platacanthomyidae (Spiny dormice)Spiny dormice (Platacanthomys)


Spalacidae (Mole-rats, Bamboo rats)Blind mole-rats (Spalax), Bamboo rats (Rhizomys)


Calomyscidae (Mouse-like hamsters)Mouse-like hamsters (Calomyscus)


Nesomyidae (African rodents)African giant pouched rats (Cricetomys), Rock mice (Petromyscus)


Cricetidae (Hamsters, New World voles & mice)Golden hamster (Mesocricetus auratus), Deer mouse (Peromyscus), Vole (Microtus)


Muridae (True mice, rats, gerbils)House mouse (Mus musculus), Brown rat (Rattus norvegicus)
Hystricomorpha-Ctenodactylidae (Gundis)Gundi (Ctenodactylus)

-Diatomyidae (Laotian rock rat)Laotian rock rat (Laonastes aenigmamus)

-Bathyergidae (African mole-rats)Naked mole-rat (Heterocephalus glaber)

-Hystricidae (Old World porcupines)African porcupine (Hystrix), Indian porcupine (Hystrix indica)

-Petromuridae (Dassie rat)Dassie rat (Petromus)

-Thryonomyidae (Cane rats)Cane rat (Thryonomys swinderianus)

-Erethizontidae (New World porcupines)North American porcupine (Erethizon dorsatum)

-Chinchillidae (Chinchillas & viscachas)Chinchilla (Chinchilla), Viscacha (Lagidium)

-Dinomyidae (Pacarana)Pacarana (Dinomys branickii)

-Caviidae (Guinea pigs, Capybaras)Guinea pig (Cavia), Capybara (Hydrochoerus hydrochaeris)

-Dasyproctidae (Agoutis)Agouti (Dasyprocta)

-Cuniculidae (Pacas)Paca (Cuniculus paca)

-Ctenomyidae (Tuco-tucos)Tuco-tucos (Ctenomys)

-Octodontidae (Degus and allies)Degu (Octodon), Coruro (Spalacopus)

-Abrocomidae (Chinchilla rats)Abrocoma (Chinchilla rat)

-Echimyidae (Spiny rats)Spiny rats (Echimys), Spiny mice (Proechimys)

-Myocastoridae (Nutria)Nutria (Myocastor coypus)

-Capromyidae (Hutias)Hutias (Capromys, Geocapromys)

IV. Summary

Rodents exemplify one of the most successful mammalian radiations, showcasing extensive ecological and morphological diversity. Originating in the Paleocene-Eocene, they spread worldwide, occupying niches from subterranean habitats (mole-rats) to arboreal canopies (squirrels), from aquatic environments (beavers) to grassland ecosystems (marmots, prairie dogs). Their unparalleled adaptability, prolific reproduction, and dental specialization have secured their dominant position as the most species-rich order of mammals.

Carnivora Primates Rodents Chiroptera Eulipotyphla Ungulata Cetacea Lagoiformes Pangolins Proboscidea Monotremata
Aplodontia rufa

Aplodontia rufa

Aplodontia rufa,Mountain Beaver

Rodents LC

Features:The temporalis muscle in masticatory muscle is strong, and it is the most primitive member of rodent

The Mountain Beaver (Aplodontia rufa) has seven subspecies.Mountain beavers live in burrows like most other rodents and have a good sense of smell and touch, relying less on sight and hearing. Eating plants, including their shells, can eat species such as cuckoos and nettles that are toxic to other...

Niviventer coxingi

Niviventer coxingi

Niviventer coxingi,Niviventer culturatus,Coxing

Rodents LC

Features:The belly is grayish white, the dorsal surface is yellowish brown, and the tentacles are very long.

The taxonomic status of this species is stable and there is little controversy. It is distributed in tropical evergreen broad-leaved forests, forest edges and shrubs below 2000m above sea level....

Cricetulus triton

Cricetulus triton

Cricetulus triton,Grey hamster

Rodents LC

Features:It has a large body, a short tail, a blunt head, cheek pouches, and short, round ears with narrow white edges.

The status of the giant hamster species is stable, and there are some differences in the genus it belongs to. Some scientists regard it as a species of the genus Cricetulus, and most scientists agree that it belongs to the genus Tscherskia. There are many subspecies differentiations, and there are 5...

Proedromys bedfordi

Proedromys bedfordi

Proedromys bedfordi,Arvicolinae

Rodents LC

Features:The body is similar to that of a vole, but slightly larger than an ordinary vole, with smaller ears hidden in the fur. The outer side of the upper incisors has a row of shallow longitudinal grooves.

The species status is stable, but the genus status is somewhat controversial. It was first named as the genus Microtus. Some people believe that it belongs to the genus Microtus (<Microtus>), while others believe that it belongs to the genus Neodon (<Neodon>). Molecular systematic studie...

Lasiopodomys brandtii

Lasiopodomys brandtii

Lasiopodomys brandtii,Sand vole, prairie vole, Blanche vole, Brandt's vole

Rodents LC

Features:The biggest feature is that the front and rear feet are hairy, and the entire sole is covered with dense hair, with only the claws exposed.

The status of Brandt's vole species is stable, but there has been a long-standing debate about which genus it belongs to. Sometimes it is placed in the genus Microtus and sometimes in the genus Phaiomys. Molecular systematics finally confirmed that it is an independent genus, namely the genus La...

Eospalax rothschildi

Eospalax rothschildi

Eospalax rothschildi,Southern zokor, ground mouse

Rodents LC

Features:The hair on the head, back and sides of the body is gray-brown, with a darker gray color and slightly rusty brown at the tips.

The species status of Roth's zokor is stable, but the genus status is controversial. Sometimes the species is placed in the genus <Myospalax>, subgenus <Eospalax>. Some scientists upgrade the subgenus to the genus Eospalax. Now most people agree with the latter opinion. There are 2 s...

Typhlomys nanus

Typhlomys nanus

Typhlomys nanus,Gray blind mouse

Rodents LC

Features:The smallest of the pig-tailed rats.

The pig-tailed rat is a new species published by Cheng Bin et al. of Kunming Institute of Zoology in 2017. It was found in the secondary forest of Abies longibracteata at an altitude of 2000-3000m, with bamboo and rhododendron shrubs under the forest....

Pigtail rat

Pigtail rat

Pigtail rat,Wuyishan tailed rat, pig tailed rat, gray blind rat, blind rat

Rodents LC

Features:It is similar in shape and size to a small house mouse, but has a very long tail. It is also called a "blind mouse" because of its small eyes.

The genus-level and species-level taxonomic units of the Chinese pig-tailed rat are very stable and undisputed. The more controversial is the number of its subspecies. The latest research shows that it contains only 2 subspecies. The other two subspecies (<daloushanensis, chapensis>) have spec...

Sicista concolor

Sicista concolor

Sicista concolor,Small rat, rat, Chinese rat

Rodents LC

Features:The tail is extremely long, about 1.5 times the body length.

The Chinese scissorium belongs to the subfamily Sicidinae of the family Jerboa. There are 13 species in the subfamily worldwide, 4 of which are in China. The Chinese scissorium is the southernmost species in the distribution area and one of the two species that live in the forest. The status of this...

Hylopetes alboniger

Hylopetes alboniger

Hylopetes alboniger, black and white flying squirrel, arrow-tailed black and white flying squirrel

Rodents LC

Features:The back of the body is dark brown, the chest and arms on the ventral side are white, and the fur is all white.

The black-and-white flying squirrel is a small flying squirrel in southern China. The adult is less than 250 mm long. It is active at night, sleeps in the nest during the day, and is active at dusk and dawn. Usually, several live in the same nest. When sleeping, the head is hidden between the front...

Sciurotamias forresti

Sciurotamias forresti

Sciurotamias forresti,White-lined rock squirrel, White-throated rock squirrel, Forster's rock squirrel, Forster's rock squirrel

Rodents LC

Features:There is a narrow white stripe on the side of the body from the shoulder to the buttocks, and a black stripe below the white stripe.

The body size of the side-striped rock squirrel is similar to that of the rock squirrel. It lives in rocky mountainous areas. It lives in camps, but is also good at climbing trees. It is often active during the day, agile, and builds nests in the cracks of rocks. It feeds on nuts and seeds, and can...

Menetes berdmorei

Menetes berdmorei

Menetes berdmorei,Multi-lined squirrel, line squirrel

Rodents LC

Features:There is a light-colored stripe in the middle of the back, and two black stripes and two light yellowish-white longitudinal stripes on each side.

There are six species of animals in the Sciuridae family, three species of squirrels and three species of flying squirrels, namely the red-bellied squirrel, the striped squirrel, the Herschel squirrel, the red flying squirrel, the white-faced flying squirrel and the small flying squirrel.The striped...

Alex Gentry

Alex Gentry

Alex Gentry,Porcupine, Chinese porcupine,Hystricomorpha,

Rodents LC

Features:It is famous for its thorns. It has long and hard thorns on its back and tail, which are important organs for defending against natural enemies.

Porcupine is also called Chinese porcupine. There are 8 species in the genus Porcupine, which are widely distributed in Europe, Asia, and Africa, and only 2 species in China. Chinese porcupine was previously considered a subspecies of Malayan porcupine (<Hystrix brachyura>), and has only recen...

Hystrix brachyura

Hystrix brachyura

Hystrix brachyura

Rodents LC

Features:It has a large body, a brown-black head, and a white longitudinal stripe in the center of the forehead. The spines inside this longitudinal stripe are slender and bristle-like.

The Malayan porcupine is the earliest species named in the genus Porcupine. Previously, there were as many as 11 subspecies or synonyms, and the Chinese porcupine (<Hystrix hodgsoni>) was also once a subspecies. The so-called "Chinese porcupine" is actually originated from Nepal. Yun...

Atherurus macrourus

Atherurus macrourus

Atherurus macrourus,Brush-tailed porcupine, Asian brush-tailed porcupine, Asian brush-tailed porcupine

Rodents LC

Features:Good at swimming and climbing trees.

There are 4 genera and more than 20 species in the porcupine family worldwide. It is a special type of rodent. There are 4 species of the genus Brushtail Porcupine worldwide, and 1 species in China. They mainly live in forests, especially forests near water. According to records, brushtail porcupine...

Rattus flavipectus

Rattus flavipectus

Rattus flavipectus,Yellow-bellied rat, Long-tailed rat

Rodents LC

Features:The tail is equal to or longer than the body length. It is agile and has strong climbing ability.

The yellow-breasted rat belongs to the Murinae subfamily. The scientific name of the yellow-breasted rat is very confusing, and it was once used as <Rattus flavipectus> for a long time. Musser & Carleton (2005) restored <Rattus tanezumi> as the species name of the yellow-breasted rat...

Rattus norvegicus

Rattus norvegicus

Rattus norvegicus,Brown rat, rat, white-tailed rat, dung rat, dung rat

Rodents LC

Features:The body is stout, and the older it gets, the darker the brown color of its back hair. Brown rats are one of the most harmful rats in rural areas and towns. They are numerous and cause great harm.

Brown rats belong to the subfamily Murinae. The species-level classification status is stable, but there are many synonyms and subspecies, and the issue of its merger is controversial. The individuals of this species are smaller in the north and larger in the south. They mainly live in houses and ar...

Rattus nitidus

Rattus nitidus

Rattus nitidus,Gray-breasted rat, water rat

Rodents LC

Features:The Macropodus is a medium-sized rodent with a stout body, large, thin ears, a slender tail, long hind legs, brown fur on the back and grayish-white fur on the belly.

Big-footed rats belong to the Murinae subfamily. The species status is stable, but there are many synonyms, and there are great differences of opinion on the merging of these synonyms. This species mainly inhabits farmland and shrubs, and is generally not in houses. It is similar to the brown rat of...

Rattus losea

Rattus losea

Rattus losea,Rosset, field mouse, garden mouse, yellow mouse, yellow-haired mouse

Rodents LC

Features:It looks very similar to the brown rat, has strong adaptability to the natural environment, and is good at swimming.

The yellow-haired rat belongs to the Murinae subfamily. The type origin of this species is Taiwan, my country. The species-level classification unit is stable, with few synonyms, but there are also disputes. It is mainly distributed in farmland, shrubs, mangroves, and garbage dumps around houses. It...

Rattus andamanensis

Rattus andamanensis

Rattus andamanensis

Rodents LC

Features:The tail is longer than the body, and there is no hair tuft at the tip of the tail.

The black-margined rat belongs to the Murinae subfamily. This species was previously considered a synonym of the black house rat (<Rattus rattus>). It was not until Musser & Caeleton (2005) that it was made an independent species. It is a relatively special species in the genus Rattus, wit...

Nesokia indica

Nesokia indica

Nesokia indica

Rodents LC

Features:The back of the body is light brown or sandy yellow, with the brown being more prominent in the center of the back.

The Indian ground mouse belongs to the genus Nesokia of the subfamily Murinae. There are 2 species in the world and 1 species in China. There is not much controversy about the species status. In history, my country has named 2 species of ground mice, which were later proved to be synonyms of the Ind...