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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
Marmota caudata

Marmota caudata

Marmota caudata,Long-tailed Marmot,Red marmot, Marmot

Rodents LC

Features:The tail is the longest among all marmots, exceeding half the length of the body. The fur on the back and sides is brown-red, so it is also called the red marmot.

The long-tailed marmot is a large terrestrial rodent of the Sciuridae family and the genus Marmota. It is slightly smaller than the gray marmot, and has the longest tail among all species of the genus Marmota, averaging about 38% or half of the body length. The fur is long and fluffy, rough and less...

Marmota baibacina

Marmota baibacina

Marmota baibacina,Altai Marmot,Tianshan marmot, Altai marmot

Rodents LC

Features:It has a short and thick body, long and soft fur, and the fur on the back is sandy yellow or sandy brown.

The gray marmot (scientific name: Marmota baibacina), also known as the Tianshan marmot and the Altai marmot, is a large terrestrial rodent mammal belonging to the order Rodentia, the family Sciuridae, and the genus Marmota. The gray marmot is a typical grassland rodent, mainly inhabiting places wit...

Spermophilus relictus

Spermophilus relictus

Spermophilus relictus,Tien Shan Ground Squirrel,Yellow rat

Rodents LC

Features:Its body size is similar to that of the red-cheeked yellow squirrel, but its tail is longer than that of the red-cheeked yellow squirrel.

The Tianshan yellow squirrel is of medium size and has a long tail. It mainly inhabits the gentle slopes of the hills in front of the mountains, small basins between mountains, and relatively dry areas on both sides of the river valley in the mountain grasslands at an altitude of 1000-1500 meters. O...

Spermophilus dauricus

Spermophilus dauricus

Spermophilus dauricus,Yellow mouse, Mongolian yellow mouse, prairie yellow mouse, bean mouse, big-eyed thief

Rodents LC

Features:The body is fat, the tail is short, and the back hair is brown. The age of the mouse is determined by body length and weight. The older the mouse is, the longer the incisors are, the darker the color, and the longer the body length is.

Daurian ground squirrel is a group of scattered animals, diurnal, one of the representative species of the northern grassland, but occasionally go out of the hole to forage at night. The activity pattern has seasonal changes. The time of ground activity of ground squirrels varies with the season. Us...

Spermophilus undulatus

Spermophilus undulatus

Spermophilus undulatus,Long-tailed Ground Squirrel,Bean rat, big-eyed thief

Rodents LC

Features:The long-tailed yellow squirrel is large in size, with the longest tail and largest body in the genus Yellow squirrel. It has long black claws, short ears, gray-brown back in summer, and its belly is mostly brown or rusty brown.

The long-tailed yellow squirrel is an animal of the Sciuridae family and the genus Squirrel. It mainly inhabits high mountains at 1700-3000m and relatively humid piedmont hills, forest edges and river valleys. The vegetation types are mostly mountain grasslands, forest grasslands and subalpine meado...

Spermophilus erythrogenys

Spermophilus erythrogenys

Spermophilus erythrogenys,Red-cheeked Ground Squirrel,Pale-tailed yellow squirrel

Rodents LC

Features:The back of the body from the top of the head to the base of the tail is sandy yellow, or grayish yellow with gray-black tones.

Red-cheeked yellow squirrel is an animal of the Sciuridae family and the genus Squirrel. It inhabits low mountain grasslands, piedmont hilly grasslands and semi-desert plains. In some places, it can rise along the river valley to the mountain grasslands of the mid-mountain belt at an altitude of 1,5...

Spermophilus alaschanicus Buchner

Spermophilus alaschanicus Buchner

Spermophilus alaschanicus Buchner, field mouse, Daurian ground mouse, Mongolian ground mouse, prairie ground mouse, big-eyed thief, bean mouse

Rodents LC

Features:The eyes are large and protruding, the external ears are degenerate, the limbs are balanced, the front claws are sharp, and the middle finger is particularly developed, which is a useful tool for digging holes.

The Alashan yellow rat was originally listed as a subspecies of the Daurian yellow rat, and became an independent valid species in 1975. It lives in grasslands and semi-desert environments. It is diurnal. It feeds on the roots, stems, leaves and seeds of herbaceous plants, and also eats insects. It...

Tamias sibiricus

Tamias sibiricus

Tamias sibiricus, birch mouse, five-browed squirrel, flower civet stick, chipmunk

Rodents LC

Features:There are several parallel longitudinal stripes of light and dark on the back of the body.

Chipmunks belong to the genus Chipmunk of the family Sciuridae. They are named for the several light and dark parallel vertical stripes on their backs. They are medium-sized, with long tails and long, fluffy, broom-like tail hairs that extend to both sides. They have slightly long limbs, and their e...

Sciurotamias davidianus

Sciurotamias davidianus

Sciurotamias davidianus,David’s rock squirrel,Sweeper, Stone Rat

Rodents LC

Features:This squirrel has the strongest reproductive capacity, with eight babies in one litter. It also loves to steal.

Rock squirrels belong to the family Sciuridae in the order Rodentia and are endemic to China. They are medium-sized, with fluffy tail hair that is sparser than the back hair, and a certain amount of all-black needle hair mixed in the middle.Rock squirrels are semi-arboreal and semi-terrestrial squir...

Ratufa bicolor

Ratufa bicolor

Ratufa bicolor(Sparrman, 1778),Black Great Squirrel,Tree dog, black civet, vine civet, black civet, black giant squirrel or Malayan giant squirrel

Rodents LC

Features:The largest arboreal squirrel.

Giant squirrels are large rodents that live in high trees in tropical and subtropical monsoon forests below 2,000 meters above sea level. They are typical arboreal animals.Giant squirrels prefer to live alone and rarely live in groups. Occasionally, 2 to 3 of them are seen feeding on the same tree....

Dremomys rufigenis

Dremomys rufigenis

Dremomys rufigenis,,Asian Red-cheeked Squirre,l Red-cheeked squirrel, Red-cheeked long-nosed squirrel

Rodents LC

Features:It has a large body and a short tail. The back of the body, including the forehead and upper legs, is dark olive green, and the abdomen is light yellowish white.

The red-cheeked long-nosed squirrel (scientific name: Dremomys rufigenis) is an animal of the family Sciuridae and the genus Dremomys. It lives a semi-arboreal life, is good at climbing and jumping, and likes to live in groups. It is more active at dawn and dusk, mainly active in bushes and forest e...

Dremomys pyrrhomerus

Dremomys pyrrhomerus

Dremomys pyrrhomerus,Thomas, 1895

Rodents LC

Features:The snout is longer and tapered. The lateral thighs, buttocks and below the knees are obviously rusty red.

The red-legged long-nosed squirrel (scientific name: Dremomys pyrrhomerus) is a protected species unique to my country and belongs to the family Sciuridae. It mainly lives in dense forests and has similar living habits to gray squirrels. It likes to be active in the morning and evening. It mainly ea...

Dremomys pernyi

Dremomys pernyi

Dremomys pernyi,Perny's Long-nosed Squirrel,Long-nosed squirrel, squirrel, hairy mouse

Rodents LC

Features:This species has the shortest snout among the genus Sciurus.

Pernyi's long-nosed squirrel (scientific name: Dremomys pernyi) is an animal of the Sciuridae family and the genus Dremomys. It mostly lives in subtropical forests, especially in tropical rainforests and trees near river valleys and streams.Perkins's long-nosed squirrels mainly live in trees...

Dremomys lokriah

Dremomys lokriah

Dremomys lokriah,Himalayan orange-bellied long-nosed squirrel, Tibetan long-nosed squirrel

Rodents LC

Features:Snout length is about 33.4% of skull length

The orange-bellied long-nosed squirrel (scientific name: Dremomys lokriah) belongs to the family Sciuridae, also known as the Himalayan orange-bellied long-nosed squirrel and the Tibetan long-nosed squirrel. It usually lives in the cycad forest at an altitude of 1500-3400 meters or the woods at 2000...

Tamiops swinhoei

Tamiops swinhoei

Tamiops swinhoei,Hidden flower squirrel, yellow-bellied flower squirrel, leopard mouse, chipmunk, golden chipmunk, three-browed squirrel, Diao Lingzi, etc.

Rodents LC

Features:There is a distinct black stripe in the middle of the back, and two brown or light yellow vertical stripes on both sides.

The chipmunk, also known as the chipmunk, yellow-bellied chipmunk, and leopard mouse, usually builds nests in tree holes, tree branches, or cracks on cliffs. It is active at dawn and dusk. Its food is mainly plant fruits, buds, seeds, and insects. It is widely distributed and is a common group. It i...

Callosciurus quinquestriatus

Callosciurus quinquestriatus

Callosciurus quinquestriatus,,Five-striped squirrel

Rodents LC

Features:The abdomen has three black stripes and two white stripes alternating between them, hence the name "striped-bellied squirrel".

The striped squirrel, also known as the five-striped squirrel, is an endangered species. The back of the body is olive brown-gray with obvious red, and the back is the darkest. The chin and throat are gray with a slight red; there is a dark stripe in the center of the ventral surface and on both out...

Callosciurus pygerythrus imitator

Callosciurus pygerythrus imitator

Callosciurus pygerythrus imitator,Irrawaddy squirrel, Yunnan squirrel

Rodents LC

Features:The tail is usually longer than the body but narrower, and the tip is usually black.

Blue-bellied squirrels are distributed in southwestern China, including southern Yunnan and Medog in southeastern Tibet. There are 8 subspecies of blue-bellied squirrels, and only one subspecies in China, namely the Yunnan subspecies.Blue-bellied squirrels are diurnal and usually act alone. They fee...

Callosciurus phayrei

Callosciurus phayrei

Callosciurus phayrei,Phayre”s Squirrel,Yellew-handed Squirrel,Yellow-footed squirrel, yellow-bellied squirrel, yellow squirrel, Philippine squirrel

Rodents LC

Features:Arboreal squirrel with yellow belly and chin.

The yellow-handed squirrel is also called the yellow-footed squirrel, yellow-bellied squirrel, yellow squirrel, and Philippine squirrel. It is slightly larger than the red-bellied squirrel. It has a narrow distribution area and a small number of species. It is a rare species.It lives in tropical rai...

Callosciurus erythraeus

Callosciurus erythraeus

Callosciurus erythraeus,Red-bellied squirrel, flying squirrel, dart mouse

Rodents LC

Features:It has a slender body, a long tail, and the color of its abdomen varies depending on the specific habitat.

Red-bellied squirrels, also known as red-bellied squirrels, are arboreal animals. They mostly live in trees, using the branches of branches to build a frame with small sticks, surrounded by leaves and fine grass to climb things, and look like a bird's nest from the outside. Some also use the hol...

Callosciurus caniceps

Callosciurus caniceps

Callosciurus caniceps,Tamiops sauteri,Sciurus thaiwanensis,Sciurus caniceps

Rodents LC

Features:

The golden-backed squirrel (scientific name: Callosciurus caniceps) is an animal of the genus Callosciurus, native to western Malaysia, Thailand and southern Myanmar. It has been artificially introduced to the Ryukyu Islands. In China, it is distributed in Kaohsiung, Taiwan and other places. The typ...

Sciurus vulgaris

Sciurus vulgaris

Sciurus vulgaris,Squirrel, Tree Rat

Rodents LC

Features:Their fur colors vary depending on the season and location.

Northern squirrels mainly live in temperate and subarctic coniferous forests or mixed coniferous and broad-leaved forests. They build nests in large trees and are good at jumping. They mainly feed on seeds of trees such as pine trees, and also eat mushrooms, young shoots, wild fruits and insects. Th...