Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
, 'to gnaw') are mammal
s of the
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
Rodentia (), which are characterized by a single pair of continuously growing incisors
in each of the upper and lower jaw
s. About 40% of all mammal species are rodents. They are native to all major land masses except for
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
, and several oceanic islands, though they have subsequently been introduced to most of these land masses by human activity.
Rodents are extremely diverse in their ecology and lifestyles and can be found in almost every terrestrial
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
, including human-made environments. Species can be arboreal
/richochetal (leaping on their hind legs), or semiaquatic. However, all rodents share several morphological features, including having only a single upper and lower pair of ever-growing incisors. Well-known rodents include mice
s, prairie dog
Beavers are large, semiaquatic rodents in the genus ''Castor'' native to the temperate Northern Hemisphere. There are two extant species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers a ...
The guinea pig or domestic guinea pig (''Cavia porcellus''), also known as the cavy or domestic cavy (), is a species of rodent belonging to the genus '' Cavia'' in the family Caviidae. Breeders tend to use the word ''cavy'' to describe the ...
s, and hamster
s, and pika
s, whose incisors also grow continually (but have two pairs of upper incisors instead of one), were once included with them, but are now considered to be in a separate order, the Lagomorpha
. Nonetheless, Rodentia and Lagomorpha are sister group
s, sharing a single common ancestor
and forming the clade
Glires (, Latin ''glīrēs'' 'dormice') is a clade (sometimes ranked as a grandorder) consisting of rodents and lagomorphs ( rabbits, hares, and pikas). The hypothesis that these form a monophyletic group has been long debated based on morpho ...
Most rodents are small animals with robust bodies, short limbs, and long tails. They use their sharp incisors to gnaw food, excavate burrows, and defend themselves. Most eat seeds or other plant material, but some have more varied diets. They tend to be social animals and many species live in societies with complex ways of communicating with each other. Mating among rodents can vary from
Monogamy ( ) is a form of dyadic relationship in which an individual has only one partner during their lifetime. Alternately, only one partner at any one time ( serial monogamy) — as compared to the various forms of non-monogamy (e.g., pol ...
Polygyny (; from Neoclassical Greek πολυγυνία (); ) is the most common and accepted form of polygamy around the world, entailing the marriage of a man with several women.
Polygyny is more widespread in Africa than in any ...
, to promiscuity
. Many have litters
of underdeveloped, altricial
young, while others are precocial
(relatively well developed) at birth.
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
record dates back to the
The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pala ...
on the supercontinent of Laurasia
. Rodents greatly diversified in the
The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...
, as they spread across continents, sometimes even crossing oceans
. Rodents reached both South America and Madagascar from Africa and, until the arrival of ''Homo sapiens'', were the only terrestrial placental mammals
to reach and colonize Australia.
Rodents have been used as food, for clothing, as pets
, and as laboratory animals
in research. Some species, in particular, the brown rat
, the black rat
, and the house mouse
, are serious
PESTS was an anonymous American activist group formed in 1986 to critique racism, tokenism, and exclusion in the art world. PESTS produced newsletters, posters, and other print material highlighting examples of discrimination in gallery represent ...
, eating and spoiling food stored by humans and spreading diseases. Accidentally
An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there ...
of rodents are often considered to be invasive
and have caused the extinction of numerous species, such as island birds, the
The dodo (''Raphus cucullatus'') is an extinct flightless bird that was endemic to the island of Mauritius, which is east of Madagascar in the Indian Ocean. The dodo's closest genetic relative was the also-extinct Rodrigues solitaire. ...
being an example, previously isolated from land-based predators.
The distinguishing feature of the rodents is their pairs of continuously growing, razor-sharp, open-rooted incisors
These incisors have thick layers of enamel on the front and little enamel on the back.
Because they do not stop growing, the animal must continue to wear them down so that they do not reach and pierce the skull. As the incisors grind against each other, the softer dentine on the rear of the teeth wears away, leaving the sharp enamel edge shaped like the blade of a chisel
Most species have up to 22 teeth with no canines or anterior premolar
s. A gap, or
A diastema (plural diastemata, from Greek διάστημα, space) is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars. More colloquially, the condition ...
, occurs between the incisors and the cheek teeth in most species. This allows rodents to suck in their cheeks or lips to shield their mouth and throat from wood shavings and other inedible material, discarding this waste from the sides of their mouths. Chinchillas and guinea pigs have a high-fiber diet; their molars have no roots and grow continuously like their incisors.
In many species, the molars are relatively large, intricately structured, and highly cusped or ridged. Rodent molars are well equipped to grind food into small particles.
The jaw musculature is strong. The lower jaw is thrust forward while gnawing and is pulled backwards during chewing.
[ Gnawing uses incisors and chewing uses molars, however, due to the cranial anatomy of rodents these feeding methods cannot be used at the same time and are considered to be mutually exclusive. Among rodents, the masseter muscles plays a key role in chewing, making up 60% - 80% of the total muscle mass among masticatory muscles and reflects rodents herbivorous diet. Rodent groups differ in the arrangement of the jaw muscles and associated skull structures, both from other mammals and amongst themselves. The Sciuromorpha, such as the eastern grey squirrel, have a large deep masseter, making them efficient at biting with the incisors. The Myomorpha, such as the brown rat, have enlarged temporalis and masseter muscles, making them able to chew powerfully with their molars.] In rodents, masseter muscles insert behind the eyes and contribute to eye boggling that occurs during gnawing where the quick contraction and relaxation of the muscle causes the eyeballs to move up and down. The Hystricomorpha, such as the guinea pig, have larger superficial masseter muscles and smaller deep masseter muscles than rats or squirrels, possibly making them less efficient at biting with the incisors, but their enlarged internal pterygoid muscles may allow them to move the jaw further sideways when chewing. The cheek pouch is a specific morphological feature used for storing food and is evident in particular subgroups of rodents like kangaroo rats, hamsters, chipmunks and gophers which have two bags that may range from the mouth to the front of the shoulders. True mice and rats do not contain this structure but their cheeks are elastic due to a high degree of musculature and innervation in the region.
While the largest species, the capybara, can weigh as much as , most rodents weigh less than . Rodents have wide-ranging morphologies, but typically have squat bodies and short limbs. The fore limbs usually have five digits, including an opposable thumb, while the hind limbs have three to five digits. The elbow gives the forearms great flexibility. The majority of species are plantigrade, walking on both the palms and soles of their feet, and have claw-like nails. The nails of burrowing species tend to be long and strong, while arboreal rodents have shorter, sharper nails. Rodent species use a wide variety of methods of locomotion including quadrupedal walking, running, burrowing, climbing, bipedal hopping ( kangaroo rat
Kangaroo rats, small mostly nocturnal rodents of genus ''Dipodomys'', are native to arid areas of western North America. The common name derives from their bipedal form. They hop in a manner similar to the much larger kangaroo, but developed ...s and hopping mice
A hopping mouse is any of about ten different Australian native mice in the genus ''Notomys''. They are rodents, not marsupials, and their ancestors are thought to have arrived from Asia about 5 million years ago.
All are brown or fawn, fadin ...), swimming and even gliding.
Scaly-tailed squirrels and flying squirrels, although not closely related, can both glide from tree to tree using parachute-like membranes that stretch from the fore to the hind limbs. The agouti
The agouti (, ) or common agouti is any of several rodent species of the genus ''Dasyprocta''. They are native to Middle America, northern and central South America, and the southern Lesser Antilles. Some species have also been introduced ... is fleet-footed and antelope-like, being digitigrade and having hoof-like nails. The majority of rodents have tails, which can be of many shapes and sizes. Some tails are prehensile
Prehensility is the quality of an appendage or organ that has adapted for grasping or holding. The word is derived from the Latin term ''prehendere'', meaning "to grasp". The ability to grasp is likely derived from a number of different orig ..., as in the Eurasian harvest mouse
The harvest mouse (''Micromys minutus'') is a small rodent native to Europe and Asia. It is typically found in fields of cereal crops, such as wheat and oats, in reed beds and in other tall ground vegetation, such as long grass and hedgerows. It ..., and the fur on the tails can vary from bushy to completely bald. The tail is sometimes used for communication, as when beavers slap their tails on the water surface or house mice rattle their tails to indicate alarm. Some species have vestigial tails or no tails at all. In some species, the tail is capable of regeneration if a part is broken off.
Rodents generally have well-developed senses of smell, hearing, and vision. Nocturnal species often have enlarged eyes and some are sensitive to ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ... light. Many species have long, sensitive whiskers or vibrissae for touch or "whisking". Whisker action is mostly driven by the brain stem, which is itself provoked by the cortex. However Legg et al. 1989 find an alternate circuit between the cortex and whiskers through the cerebellar circuits, and Hemelt & Keller 2008 the superior colliculus. Some rodents have cheek pouches
Cheek pouches are pockets on both sides of the head of some mammals between the jaw and the cheek. They can be found on mammals including the platypus, some rodents, and most monkeys, as well as the marsupial koala. The cheek pouches of chipmunks ..., which may be lined with fur. These can be turned inside out for cleaning. In many species, the tongue cannot reach past the incisors. Rodents have efficient digestive systems, absorbing nearly 80% of ingested energy. When eating cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wa ..., the food is softened in the stomach and passed to the cecum, where bacteria reduce it to its carbohydrate
In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may o ... elements. The rodent then practices coprophagy
Coprophagia () or coprophagy () is the consumption of feces. The word is derived from the grc, κόπρος , "feces" and , "to eat". Coprophagy refers to many kinds of feces-eating, including eating feces of other species (heterospecifics), o ..., eating its own fecal pellets, so the nutrients can be absorbed by the gut. Rodents therefore often produce a hard and dry fecal pellet. Horn et al. 2013 makes the finding that rodents entirely lack the ability to vomit. In many species, the penis contains a bone, the baculum
The baculum (also penis bone, penile bone, or ''os penis'', ''os genitale'' or ''os priapi'') is a bone found in the penis of many placental mammals. It is absent from the human penis, but present in the penises of some primates, such as the ...; the testes can be located either abdominally or at the groin.
Sexual dimorphism occurs in many rodent species. In some rodents, males are larger than females, while in others the reverse is true. Male-bias sexual dimorphism is typical for ground squirrels, kangaroo rats, solitary mole rats and pocket gophers; it likely developed due to sexual selection
Sexual selection is a mode of natural selection in which members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (in ... and greater male-male combat. Female-bias sexual dimorphism exists among chipmunks and jumping mice. It is not understood why this pattern occurs, but in the case of yellow-pine chipmunk
The yellow-pine chipmunk (''Neotamias amoenus'') is a species of order Rodentia in the family Sciuridae. It is found in western North America: parts of Canada and the United States.
These chipmunks are normally found in brush-covered areas, and ...s, males may have selected larger females due to their greater reproductive success. In some species, such as voles, sexual dimorphism can vary from population to population. In bank voles, females are typically larger than males, but male-bias sexual dimorphism occurs in alpine populations, possibly because of the lack of predators and greater competition between males.
Distribution and habitat
One of the most widespread groups of mammals, rodents can be found on every continent except Antarctica. They are the only terrestrial placental mammals to have colonized Australia and
New Guinea (; Hiri Motu: ''Niu Gini''; id, Papua, or , historically ) is the world's second-largest island with an area of . Located in Oceania in the southwestern Pacific Ocean, the island is separated from Australia by the wide Torres ... without human intervention. Humans have also allowed the animals to spread to many remote oceanic islands (e.g., the Polynesian rat
The Polynesian rat, Pacific rat or little rat (''Rattus exulans''), known to the Māori as ''kiore'', is the third most widespread species of rat in the world behind the brown rat and black rat. The Polynesian rat originated in Southeast Asia, a ...). Rodents have adapted to almost every terrestrial habitat, from cold tundra (where they can live under snow) to hot deserts.
Some species such as tree squirrels and New World porcupines are arboreal, while some, such as gophers, tuco-tuco
A tuco-tuco is a neotropical rodent in the family Ctenomyidae.Parada, A., G. D’Elia, C.J. Bidau, and E.P. Lessa. 2011. Species Groups and the Evolutionary Diversification of Tuco-Tucos, genus ''Ctenomys'' (Rodentia: Ctenomyidae). ''Journal of M ...s, and mole rats, live almost completely underground, where they build complex burrow systems. Others dwell on the surface of the ground, but may have a burrow into which they can retreat. Beavers and muskrats are known for being semiaquatic, but the rodent best-adapted for aquatic life is probably the earless water rat
The earless water rat (''Crossomys moncktoni'') is a New Guinea rodent, part of the ''Hydromys'' group of the subfamily of Old World rats and mice (Murinae). It is the only species of the genus ''Crossomys''. This species is probably most close ... from New Guinea. Rodents have also thrived in human-created environments such as agricultural and urban area
An urban area, built-up area or urban agglomeration is a human settlement with a high population density and infrastructure of built environment. Urban areas are created through urbanization and are categorized by urban morphology as cities ...s.
Though some species are common pests for humans, rodents also play important ecological roles. Some rodents are considered keystone species and ecosystem engineers in their respective habitats. In the Great Plains
The Great Plains (french: Grandes Plaines), sometimes simply "the Plains", is a broad expanse of flatland in North America. It is located west of the Mississippi River and east of the Rocky Mountains, much of it covered in prairie, steppe, a ... of North America, the burrowing activities of prairie dogs play important roles in soil aeration and nutrient redistribution, raising the organic content of the soil and increasing the absorption of water. They maintain these grassland habitats, and some large herbivores such as bison
Bison are large bovines in the genus ''Bison'' (Greek: "wild ox" (bison)) within the tribe Bovini. Two extant and numerous extinct species are recognised.
Of the two surviving species, the American bison, ''B. bison'', found only in North A ... and pronghorn prefer to graze near prairie dog colonies due to the increased nutritional quality of forage.
Extirpation of prairie dogs can also contribute to regional and local biodiversity loss, increased seed depredation, and the establishment and spread of invasive shrubs. Burrowing rodents may eat the fruiting bodies of fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ... and spread spores through their feces, thereby allowing the fungi to disperse and form symbiotic relationships with the roots of plants (which usually cannot thrive without them). As such, these rodents may play a role in maintaining healthy forests.
In many temperate regions, beavers play an essential hydrological role. When building their dams and lodges, beavers alter the paths of streams and rivers and allow for the creation of extensive wetland habitats. One study found that engineering by beavers leads to a 33 percent increase in the number of herbaceous plant
Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials.
Definitions of "herb" and "herbaceous"
The fourth edition ... species in riparian areas. Another study found that beavers increase wild salmon populations. Meanwhile, some rodents are seen as pests
PESTS was an anonymous American activist group formed in 1986 to critique racism, tokenism, and exclusion in the art world. PESTS produced newsletters, posters, and other print material highlighting examples of discrimination in gallery represent ..., due to their wide range.
Behavior and life history
Most rodents are herbivorous, feeding exclusively on plant material such as seeds, stems, leaves, flowers, and roots. Some are omnivorous and a few are predators.
[ The field vole is a typical herbivorous rodent and feeds on grasses, herbs, root tubers, moss, and other vegetation, and gnaws on bark during the winter. It occasionally eats invertebrates such as insect larvae. The plains pocket gopher eats plant material found underground during tunneling, and also collects grasses, roots, and tubers in its cheek pouches and caches them in underground larder chambers.
The Texas pocket gopher avoids emerging onto the surface to feed by seizing the roots of plants with its jaws and pulling them downwards into its burrow. It also practices coprophagy. The ] African pouched rat
Emin's pouched rat ''(Cricetomys emini)'', also known as the African pouched rat, is a large rat of the muroid superfamily. It is related to ''Cricetomys gambianus'', the Gambian pouched rat. Both species belong to '' Cricetomys'', the genus of ... forages on the surface, gathering anything that might be edible into its capacious cheek pouches until its face bulges out sideways. It then returns to its burrow to sort through the material it has gathered and eats the nutritious items.
The agouti (, ) or common agouti is any of several rodent species of the genus ''Dasyprocta''. They are native to Middle America, northern and central South America, and the southern Lesser Antilles. Some species have also been introduced ... species are one of the few animal groups that can break open the large capsules of the Brazil nut
The Brazil nut (''Bertholletia excelsa'') is a South American tree in the family Lecythidaceae, and it is also the name of the tree's commercially harvested edible seeds. It is one of the largest and longest-lived trees in the Amazon rainforest ... fruit. Too many seeds are inside to be consumed in one meal, so the agouti carries some off and caches them. This helps dispersal of the seeds as any that the agouti fails to retrieve are distant from the parent tree when they germinate. Other nut-bearing trees tend to bear a glut of fruits in the autumn. These are too numerous to be eaten in one meal and squirrels gather and store the surplus in crevices and hollow trees. In desert regions, seeds are often available only for short periods. The kangaroo rat collects all it can find and stores them in larder chambers in its burrow. [
A strategy for dealing with seasonal plenty is to eat as much as possible and store the surplus nutrients as fat. Marmots do this, and may be 50% heavier in the autumn than in the spring. They rely on their fat reserves during their long winter hibernation.] [ Beavers feed on the leaves, buds, and inner bark of growing trees, as well as aquatic plants. They store food for winter use by felling small trees and leafy branches in the autumn and immersing them in their pond, sticking the ends into the mud to anchor them. Here, they can access their food supply underwater even when their pond is frozen over.
Although rodents have been regarded traditionally as herbivores, most small rodents opportunistically include insects, worms, fungi, fish, or meat in their diets and a few have become specialized to rely on a diet of animal matter. A functional-morphological study of the rodent tooth system supports the idea that primitive rodents were omnivores rather than herbivores. Studies of the literature show that numerous members of the Sciuromorpha and Myomorpha, and a few members of the Hystricomorpha, have either included animal matter in their diets or been prepared to eat such food when offered it in captivity. Examination of the stomach contents of the North American white-footed mouse, normally considered to be herbivorous, showed 34% animal matter.]
More specialized carnivores include the shrewlike rat
The shrewlike rats, genus ''Rhynchomys'', also known as the tweezer-beaked rats are a group of unusual Old World rats found only on the island of Luzon in the Philippines. They look a great deal like shrews and are an example of convergent evol ...s of the Philippines, which feed on insects and soft-bodied invertebrates, and the Australian water rat, which devours aquatic insects, fish, crustaceans, mussels, snails, frogs, birds' eggs, and water birds. [ The ] grasshopper mouse
Grasshopper mice are rodents of the genus ''Onychomys'', occurring in North America. They feed on insects and other arthropods.
The three species in this genus of New World mice are only distantly related to the common house mouse, ''Mu ... from dry regions of North America feeds on insects, scorpions, and other small mice, and only a small part of its diet is plant material. It has a chunky body with short legs and tail, but is agile and can easily overpower prey as large as itself.
Rodents exhibit a wide range of types of social behavior ranging from the mammalian
Caste is a form of social stratification characterised by endogamy, hereditary transmission of a style of life which often includes an occupation, ritual status in a hierarchy, and customary social interaction and exclusion based on cultural ... of the naked mole-rat
The naked mole-rat (''Heterocephalus glaber''), also known as the sand puppy, is a burrowing rodent native to the Horn of Africa and parts of Kenya, notably in Somali regions. It is closely related to the blesmols and is the only species in th ..., the extensive "town" of the colonial prairie dog, through family groups to the independent, solitary life of the edible dormouse. Adult dormice may have overlapping feeding ranges, but they live in individual nests and feed separately, coming together briefly in the breeding season to mate. The pocket gopher is also a solitary animal outside the breeding season, each individual digging a complex tunnel system and maintaining a territory.
Larger rodents tend to live in family units where parents and their offspring live together until the young disperse. Beaver
Beavers are large, semiaquatic rodents in the genus ''Castor'' native to the temperate Northern Hemisphere. There are two extant species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers a ...s live in extended family units typically with a pair of adults, this year's kits, the previous year's offspring, and sometimes older young. Brown rats usually live in small colonies with up to six females sharing a burrow and one male defending a territory around the burrow. At high population densities, this system breaks down and males show a hierarchical system of dominance with overlapping ranges. Female offspring remain in the colony while male young disperse. The prairie vole is monogamous and forms a lifelong pair bond. Outside the breeding season, prairie voles live with others in small colonies. A male is not aggressive towards other males until he has mated, after which time he defends a territory, a female, and a nest against other males. The pair huddles together, grooms one another, and shares nesting and pup-raising responsibilities.
Among the most social of rodents are the ground squirrels, which typically form colonies
In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the '' metropolitan state'' ... based on female kinship, with males dispersing after weaning and becoming nomadic as adults. Cooperation in ground squirrels varies between species and typically includes making alarm calls, defending territories, sharing food, protecting nesting areas, and preventing infanticide. The black-tailed prairie dog forms large towns that may cover many hectares. The burrows do not interconnect, but are excavated and occupied by territorial family groups known as coteries. A coterie often consists of an adult male, three or four adult females, several nonbreeding yearlings, and the current year's offspring. Individuals within coteries are friendly with each other, but hostile towards outsiders. [
Perhaps the most extreme examples of colonial behavior in rodents are the eusocial naked mole rat and Damaraland mole rat. The naked mole rat lives completely underground and can form colonies of up to 80 individuals. Only one female and up to three males in the colony reproduce, while the rest of the members are smaller and sterile, and function as workers. Some individuals are of intermediate size. They help with the rearing of the young and can take the place of a reproductive if one dies.] The Damaraland mole rat is characterized by having a single reproductively active male and female in a colony where the remaining animals are not truly sterile, but become fertile only if they establish a colony of their own.
Rodents use scent marking in many social contexts including inter- and intra-species communication, the marking of trails and the establishment of territories. Their urine provides genetic information about individuals including the species, the sex and individual identity, and metabolic information on dominance, reproductive status and health. Compounds derived from the major histocompatibility complex (MHC) are bound to several urinary proteins. The odor of a predator depresses scent-marking behavior.
Rodents are able to recognize close relatives by smell and this allows them to show nepotism (preferential behavior toward their kin) and also avoid inbreeding. This kin recognition is by olfactory cues from urine, feces and glandular secretions. The main assessment may involve the MHC, where the degree of relatedness of two individuals is correlated to the MHC genes they have in common. In non-kin communication, where more permanent odor markers are required, as at territorial borders, then non-volatile major urinary proteins (MUPs), which function as pheromone transporters, may also be used. MUPs may also signal individual identity, with each male house mouse (''Mus musculus'') excreting urine containing about a dozen genetically encoded MUPs.
House mice deposit urine, which contains pheromones, for territorial marking, individual and group recognition, and social organization. Territorial beavers and red squirrels investigate and become familiar with the scents of their neighbors and respond less aggressively to intrusions by them than to those made by non-territorial "floaters" or strangers. This is known as the " dear enemy effect
The dear enemy effect or dear enemy recognition is an ethological phenomenon in which two neighbouring territorial animals become less aggressive toward one another once territorial borders are well established. As territory owners become accustome ...".
Many rodent species, particularly those that are diurnal and social, have a wide range of alarm calls that are emitted when they perceive threats. There are both direct and indirect benefits of doing this. A potential predator may stop when it knows it has been detected, or an alarm call can allow conspecifics or related individuals to take evasive action. Several species, for example prairie dogs, have complex anti-predator alarm call systems. These species may have different calls for different predators (e.g. aerial predators or ground-based predators) and each call contains information about the nature of the precise threat. The urgency of the threat is also conveyed by the acoustic properties of the call.
Social rodents have a wider range of vocalizations than do solitary species. Fifteen different call-types have been recognized in adult Kataba mole rats and four in juveniles. Similarly, the common degu, another social, burrowing rodent, exhibits a wide array of communication methods and has an elaborate vocal repertoire comprising fifteen different categories of sound. Ultrasonic calls play a part in social communication between dormice and are used when the individuals are out of sight of each other.
House mice use both audible and ultrasonic calls in a variety of contexts. Audible vocalizations can often be heard during agonistic or aggressive encounters, whereas ultrasound is used in sexual communication and also by pups when they have fallen out of the nest.
Laboratory rats (which are brown rats, ''Rattus norvegicus'') emit short, high frequency, ultrasonic vocalizations during purportedly pleasurable experiences such as rough-and-tumble play, when anticipating routine doses of morphine
Morphine is a strong opiate that is found naturally in opium, a dark brown resin in poppies ('' Papaver somniferum''). It is mainly used as a pain medication, and is also commonly used recreationally, or to make other illicit opioids. T ..., during mating, and when tickled. The vocalization, described as a distinct "chirping", has been likened to laughter, and is interpreted as an expectation of something rewarding. In clinical studies, the chirping is associated with positive emotional feelings, and social bonding occurs with the tickler, resulting in the rats becoming conditioned to seek the tickling. However, as the rats age, the tendency to chirp declines. Like most rat vocalizations, the chirping is at frequencies too high for humans to hear without special equipment, so bat detectors have been used for this purpose.
Rodents, like all placental mammals except primates, have just two types of light receptive cones in their retina, a short wavelength "blue-UV" type and a middle wavelength "green" type. They are therefore classified as
Dichromacy (from Greek ''di'', meaning "two" and ''chromo'', meaning "color") is the state of having two types of functioning photoreceptors, called cone cells, in the eyes. Organisms with dichromacy are called dichromats. Dichromats requir ...; however, they are visually sensitive into the ultraviolet (UV) spectrum and therefore can see light that humans can not. The functions of this UV sensitivity are not always clear. In degus, for example, the belly reflects more UV light than the back. Therefore, when a degu stands up on its hind legs, which it does when alarmed, it exposes its belly to other degus and ultraviolet vision may serve a purpose in communicating the alarm. When it stands on all fours, its low UV-reflectance back could help make the degu less visible to predators. Ultraviolet light is abundant during the day but not at night. There is a large increase in the ratio of ultraviolet to visible light in the morning and evening twilight hours. Many rodents are active during twilight hours (crepuscular activity), and UV-sensitivity would be advantageous at these times. Ultraviolet reflectivity is of dubious value for nocturnal rodents.
The urine of many rodents (e.g. voles, degus, mice, rats) strongly reflects UV light and this may be used in communication by leaving visible as well as olfactory markings. However, the amount of UV that is reflected decreases with time, which in some circumstances can be disadvantageous; the common kestrel can distinguish between old and fresh rodent trails and has greater success hunting over more recently marked routes.
Vibrations can provide cues to conspecifics about specific behaviors being performed, predator warning and avoidance, herd or group maintenance, and courtship. The
Middle East blind mole rat
The Middle East blind mole-rat or Palestine mole-rat (''Nannospalax ehrenbergi'') is a species of rodent in the family Spalacidae.
It was formerly classified in the genus ''Spalax'', but more recent phylogenetic evidence supports it ... was the first mammal for which seismic communication was documented. These fossorial rodents bang their head against the walls of their tunnels. This behavior was initially interpreted as part of their tunnel building behavior, but it was eventually realized that they generate temporally patterned seismic signals for long-distance communication with neighboring mole rats.
Footdrumming is used widely as a predator warning or defensive action. It is used primarily by fossorial or semi-fossorial rodents. The banner-tailed kangaroo rat produces several complex footdrumming patterns in a number of different contexts, one of which is when it encounters a snake. The footdrumming may alert nearby offspring but most likely conveys that the rat is too alert for a successful attack, thus preventing the snake's predatory pursuit. Several studies have indicated intentional use of ground vibrations as a means of intra-specific communication during courtship among the Cape mole rat
The Cape mole-rat (''Georychus capensis'') is a species of mole-rat endemic to South Africa. It is the only extant species currently described as belonging to the genus ''Georychus''.
Cape mole-rats closely resemble other Africa .... Footdrumming has been reported to be involved in male-male competition; the dominant male indicates its resource holding potential by drumming, thus minimizing physical contact with potential rivals.
Some species of rodent are monogamous, with an adult male and female forming a lasting pair bond. Monogamy can come in two forms; obligate and facultative. In obligate monogamy, both parents care for the offspring and play an important part in their survival. This occurs in species such as California mice, oldfield mice,
Malagasy giant rat
The Malagasy giant rat (''Hypogeomys antimena''), also known as the votsotsa or votsovotsa, is a nesomyid rodent found only in the Menabe region of Madagascar. It is an endangered species due to habitat loss, slow reproduction, and limited ran ...s and beavers. In these species, males usually mate only with their partners. In addition to increased care for young, obligate monogamy can also be beneficial to the adult male as it decreases the chances of never finding a mate or mating with an infertile female. In facultative monogamy, the males do not provide direct parental care and stay with one female because they cannot access others due to being spatially dispersed. Prairie voles appear to be an example of this form of monogamy, with males guarding and defending females within their vicinity.
In polygynous species, males will try to monopolize and mate with multiple females. As with monogamy, polygyny in rodents can come in two forms; defense and non-defense. Defense polygyny involves males controlling territories that contain resources that attract females. This occurs in ground squirrels like yellow-bellied marmot
The yellow-bellied marmot (''Marmota flaviventris''), also known as the rock chuck, is a large, stout-bodied ground squirrel in the marmot genus. It is one of fourteen species of marmots, and is native to mountainous regions of southwestern Ca ...s, California ground squirrel
The California ground squirrel (''Otospermophilus beecheyi''), also known as the Beechey ground squirrel, is a common and easily observed ground squirrel of the western United States and the Baja California Peninsula; it is common in Oregon and ...s, Columbian ground squirrels and Richardson's ground squirrels. Males with territories are known as "resident" males and the females that live within the territories are known as "resident" females. In the case of marmots, resident males do not appear to ever lose their territories and always win encounters with invading males. Some species are also known to directly defend their resident females and the ensuing fights can lead to severe wounding. In species with non-defense polygyny, males are not territorial and wander widely in search of females to monopolize. These males establish dominance hierarchies, with the high-ranking males having access to the most females. This occurs in species like Belding's ground squirrels and some tree squirrel species. [
thumbnail, A in a female Richardson's ground squirrel">mating plug in a female Richardson's ground squirrel
Promiscuity, in which both males and females mate with multiple partners, also occurs in rodents. In species such as the white-footed mouse, females give birth to litters with multiple paternities. Promiscuity leads to increased sperm competition and males tend to have larger testicles. In the Cape ground squirrel, the male's testes can be 20 percent of its head-body length.] [ Several rodent species have flexible mating systems that can vary between monogamy, polygyny and promiscuity.] [
Female rodents play an active role in choosing their mates. Factors that contribute to female preference may include the size, dominance and spatial ability of the male.] [ In the eusocial naked mole rats, a single female monopolizes mating from at least three males.]
In most rodent species, such as brown rats and house mice, ovulation occurs on a regular cycle while in others, such as voles, it is induced by mating. During copulation, males of some rodent species deposit a mating plug
A mating plug, also known as a copulation plug, sperm plug, vaginal plug, or sphragis (Latin, from Greek σφραγίς ''sphragis'', "a seal"), is gelatinous secretion used in the mating of some species. It is deposited by a male into a female g ... in the female's genital opening, both to prevent sperm leakage and to protect against other males inseminating the female. Females can remove the plug and may do so either immediately or after several hours.
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run ... of thyroid hormones and iodine in the mediobasal hypothalamus
The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus ... changes in response to photoperiod. Thyroid hormones in turn induce reproductive changes. This is found by Watanabe et al. 2004 and 2007, Barrett et al. 2007, Freeman et al. 2007, and Herwig et al. 2009 in Siberian hamster
The winter white dwarf hamster (''Phodopus sungorus''), also known as the Russian dwarf hamster, Djungarian hamster, striped dwarf hamster, Siberian hamster, or Siberian dwarf hamster, is one of three species of hamster in the genus ''Phodopus'' ...s, Revel et al. 2006 and Yasuo et al. 2007 in Syrian hamsters, Yasuo et al. 2007 and Ross et al. 2011 in rats, and Ono et al. 2008 in mice.
Birth and parenting
Rodents may be born either altricial (blind, hairless and relatively underdeveloped) or precocial (mostly furred, eyes open and fairly developed) depending on the species. The altricial state is typical for squirrels and mice, while the precocial state usually occurs in species like guinea pigs and porcupines. Females with altricial young typically build elaborate nests before they give birth and maintain them until their offspring are weaned. The female gives birth sitting or lying down and the young emerge in the direction she is facing. The newborns first venture out of the nest a few days after they have opened their eyes and initially keep returning regularly. As they get older and more developed, they visit the nest less often and leave permanently when weaned.
In precocial species, the mothers invest little in nest building and some do not build nests at all. The female gives birth standing and the young emerge behind her. Mothers of these species maintain contact with their highly mobile young with maternal contact calls. Though relatively independent and weaned within days, precocial young may continue to nurse and be groomed by their mothers. Rodent litter sizes also vary and females with smaller litters spend more time in the nest than those with larger litters.]
Mother rodents provide both direct parental care, such as nursing, grooming, retrieving and huddling, and indirect parenting, such as food caching, nest building and protection to their offspring. [ In many social species, young may be cared for by individuals other than their parents, a practice known as alloparenting or cooperative breeding. This is known to occur in black-tailed prairie dogs and Belding's ground squirrels, where mothers have communal nests and nurse unrelated young along with their own. There is some question as to whether these mothers can distinguish which young are theirs. In the Patagonian mara, young are also placed in communal warrens, but mothers do not permit youngsters other than their own to nurse.
Infanticide exists in numerous rodent species and may be practiced by adult conspecifics of either sex. Several reasons have been proposed for this behavior, including nutritional stress, resource competition, avoiding misdirecting parental care and, in the case of males, attempting to make the mother sexually receptive. The latter reason is well supported in ] primate
Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians ( monkeys and apes, the latter includin ...s and lions but less so in rodents. Infanticide appears to be widespread in black-tailed prairie dogs, including infanticide from invading males and immigrant females, as well as occasional cannibalism of an individual's own offspring. To protect against infanticide from other adults, female rodents may employ avoidance or direct aggression against potential perpetrators, multiple mating, territoriality or early termination of pregnancy. [ Feticide can also occur among rodents; in ] Alpine marmot
The alpine marmot (''Marmota marmota'') is a large ground-dwelling squirrel, from the genus of marmots. It is found in high numbers in mountainous areas of central and southern Europe, at heights between in the Alps, Carpathians, Tatras and No ...s, dominant females tend to suppress the reproduction of subordinates by being antagonistic towards them while they are pregnant. The resulting stress causes the fetuses to abort.
Rodents have advanced cognitive abilities. They can quickly learn to avoid poisoned baits, which makes them difficult pests to deal with.
Guinea pigs can learn and remember complex pathways to food. Squirrels and kangaroo rats are able to locate caches of food by spatial memory, rather than just by smell.
Because laboratory mice (house mice) and rats (brown rats) are widely used as scientific models to further our understanding of biology, a great deal has come to be known about their cognitive capacities. Brown rats exhibit cognitive bias, where information processing is biased by whether they are in a positive or negative affective state. For example, laboratory rats trained to respond to a specific tone by pressing a lever to receive a reward, and to press another lever in response to a different tone so as to avoid receiving an electric shock, are more likely to respond to an intermediate tone by choosing the reward lever if they have just been tickled (something they enjoy), indicating "a link between the directly measured positive affective state and decision making under uncertainty in an animal model."
Laboratory (brown) rats may have the capacity for metacognition—to consider their own learning and then make decisions based on what they know, or do not know, as indicated by choices they make apparently trading off difficulty of tasks and expected rewards, making them the first animals other than primates known to have this capacity, but these findings are disputed, since the rats may have been following simple operant conditioning principles, or a behavioral economic model. Brown rats use social learning in a wide range of situations, but perhaps especially so in acquiring food preferences.
Classification and evolution
Dentition is the key feature by which
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ... rodents are recognized and the earliest record of such mammals comes from the Paleocene
The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pala ..., shortly after the extinction of the non-avian dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...s some 66 million years ago. These fossils are found in Laurasia, [ the supercontinent composed of modern-day North America, Europe, and Asia. The divergence of ] Glires
Glires (, Latin ''glīrēs'' 'dormice') is a clade (sometimes ranked as a grandorder) consisting of rodents and lagomorphs ( rabbits, hares, and pikas). The hypothesis that these form a monophyletic group has been long debated based on morpho ..., a clade consisting of rodents and lagomorphs (rabbits, hares and pikas), from other placental mammals occurred within a few million years after the Cretaceous-Paleogene boundary; rodents and lagomorphs then radiated during the Cenozoic
The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configu .... Some molecular clock
The molecular clock is a figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged. The biomolecular data used for such calculations are usually nucleo ... data suggest modern rodents (members of the order Rodentia) had appeared by the late Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ..., although other molecular divergence estimations are in agreement with the fossil record.
Rodents are thought to have evolved in Asia, where local multituberculate faunas were severely affected by the Cretaceous–Paleogene extinction event
The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the ... and never fully recovered, unlike their North American and European relatives. In the resulting ecological vacuum, rodents and other Glires were able to evolve and diversify, taking the niches left by extinct multituberculates. The correlation between the spread of rodents and the demise of multituberculates is a controversial topic, not fully resolved. American and European multituberculate assemblages do decline in diversity in correlation with the introduction of rodents in these areas, but the remaining Asian multituberculates co-existed with rodents with no observable replacement taking place, and ultimately both clades co-existed for at least 15 million years.
The history of the colonization of the world's continents by rodents is complex. The movements of the large superfamily Muroidea (including hamsters, gerbils, true mice and rats) may have involved up to seven colonizations of Africa, five of North America, four of Southeast Asia, two of South America and up to ten of Eurasia.
During the Eocene
The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ..., rodents began to diversify. Beavers appeared in Eurasia in the late Eocene before spreading to North America in the late Miocene. Late in the Eocene, hystricognaths invaded Africa, most probably having originated in Asia at least 39.5 million years ago. From Africa, fossil evidence shows that some hystricognaths ( caviomorph
Caviomorpha is the rodent infraorder or parvorder that unites all New World hystricognaths. It is supported by both fossil and molecular evidence. The Caviomorpha was for a time considered to be a separate order outside the Rodentia, but is ...s) colonized South America, which was an isolated continent at the time, evidently making use of ocean currents to cross the Atlantic on floating debris. Caviomorphs had arrived in South America by 41 million years ago (implying a date at least as early as this for hystricognaths in Africa), [ and had reached the Greater Antilles by the early Oligocene, suggesting that they must have dispersed rapidly across South America.
Nesomyid rodents are thought to have rafted from Africa to Madagascar 20–24 million years ago.] All 27 species of native Malagasy rodents appear to be descendants of a single colonization event.
By 20 million years ago, fossils recognizably belonging to the current families such as Muridae had emerged. [ By the ] Miocene
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ..., when Africa had collided with Asia, African rodents such as the porcupine began to spread into Eurasia
Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelag .... Some fossil species were very large in comparison to modern rodents and included the giant beaver, '' Castoroides ohioensis'', which grew to a length of and weight of . The largest known rodent was '' Josephoartigasia monesi
''Josephoartigasia'' is an extinct genus of enormous dinomyid rodent from the Early Pliocene to Early Pleistocene of Uruguay. The only living member of Dinomyidae is the pacarana. ''Josephoartigasia'' is named after Uruguayan national hero Jos ...'', a pacarana
The pacarana (''Dinomys branickii'') is a rare and slow-moving hystricognath rodent indigenous to South America. Native Tupi people call it the ''pacarana'' (false paca) because it is superficially similar to the paca, a different rodent which is ... with an estimated body length of 3 m (10 ft).
The first rodents arrived in Australia via Indonesia around 5 million years ago. Although marsupial
Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in ...s are the most prominent mammals in Australia, many rodents, all belonging to the subfamily Murinae, are among the continent's mammal species. There are about fifty species of 'old endemics', the first wave of rodents to colonize the country in the Miocene and early Pliocene
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58'') species of 'new endemics', arriving in a subsequent wave in the late Pliocene or early [Rattus
''Rattus'' is a genus of muroid rodents, all typically called rats. However, the term rat can also be applied to rodent species outside of this genus.
Species and description
The best-known ''Rattus'' species are the black rat (''R. rattus'') ...](_blank) Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina .... The earliest fossil rodents in Australia have a maximum age of 4.5 million years, and molecular data is consistent with the colonization of New Guinea from the west during the late Miocene or early Pliocene followed by rapid diversification. A further wave of adaptive radiation
In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic in ... occurred after one or more colonizations of Australia some 2 to 3 million years later.
Rodents participated in the Great American Interchange that resulted from the joining of the Americas by formation of the Isthmus of Panama, around 3 million years ago in the Piacenzian age. In this exchange, a small number of species such as the New World porcupines (Erethizontidae) headed north. However, the main southward invasion of sigmodontines preceded formation of the land bridge by at least several million years, probably occurring via rafting. Sigmodontines diversified explosively once in South America, although some degree of diversification may have already occurred in Central America before the colonization.
The use of the
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ... name "Rodentia" is attributed to the English traveler and naturalist Thomas Edward Bowdich
Thomas Edward Bowdich (20 June 179110 January 1824) was an English traveller and author.
Bowdich was born at Bristol and educated at Bristol Grammar School. In 1813, he married Sarah Wallis, who shared his subsequent career.
In 1814, thro ... (1821). The Modern Latin word is derived from , present participle of – "to gnaw", "eat away". The hares, rabbits and pikas (order Lagomorpha) have continuously growing incisors, as do rodents, and were at one time included in the order. However, they have an additional pair of incisors in the upper jaw and the two orders have quite separate evolutionary histories. The phylogeny of the rodents places them in the clades Glires, Euarchontoglires and Boreoeutheria. The cladogram below shows the inner and outer relations of Rodentia based on a 2012 attempt by Wu et al. to align the molecular clock with paleontological data:
The living rodent families based on the study done by Fabre et al. 2012.
The order Rodentia may be divided into suborders, infraorders, superfamilies and families. There is a great deal of parallelism and convergence among rodents caused by the fact that they have tended to evolve to fill largely similar niches. This parallel evolution includes not only the structure of the teeth, but also the infraorbital region of the skull (below the eye socket) and makes classification difficult as similar traits may not be due to common ancestry. [ ] Brandt
Brandt may refer to:
Places United States
* Brandt, Ohio, an unincorporated community
* Brandt, South Dakota, a town
* Brandt Township, Polk County, Minnesota
* Mount Brandt, Queen Maud Land, Antarctica
* Brandt Cove, South Georgi ... (1855) was the first to propose dividing Rodentia into three suborders, Sciuromorpha, Hystricomorpha and Myomorpha, based on the development of certain muscles in the jaw and this system was widely accepted. Schlosser (1884) performed a comprehensive review of rodent fossils, mainly using the cheek teeth, and found that they fitted into the classical system, but Tullborg (1899) proposed just two sub-orders, Sciurognathi and Hystricognathi. These were based on the degree of inflection of the lower jaw and were to be further subdivided into Sciuromorpha, Myomorpha, Hystricomorpha and Bathyergomorpha. Matthew (1910) created a phylogenetic tree of New World rodents but did not include the more problematic Old World species. Further attempts at classification continued without agreement, with some authors adopting the classical three suborder system and others Tullborg's two suborders.
These disagreements remain unresolved, nor have molecular studies fully resolved the situation though they have confirmed the monophyly
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic ... of the group and that the clade has descended from a common Paleocene ancestor. Carleton and Musser (2005) in ''Mammal Species of the World'' have provisionally adopted a five suborder system: Sciuromorpha, Castorimorpha, Myomorpha, Anomaluromorpha, and Hystricomorpha. As of 2021 the American Society of Mammalogists recognizes 34 recent families containing more than 481 genera and 2277 species.
Order Rodentia (from Latin, ''rodere'', to gnaw)
Anomaluromorpha is a clade that unites the anomalures, springhares, and zenkerella. It has alternately been designated as either a suborder or infraorder. Most recently, recognized it as one of five suborders of rodents.
*::*Family Anomaluridae: scaly-tailed squirrels
*::*Family Pedetidae: springhares
*::*Family Zenkerellidae: Cameroon scaly-tail
*:** Family Castoridae: beavers
*:**Family Geomyidae: pocket gophers (true gophers)
*:**Family Heteromyidae: kangaroo rats, kangaroo mice
**:*Family Ctenodactylidae: gundis
Diatomyidae is a family of hystricomorph rodents. It is represented by a single living species, '' Laonastes aenigmamus,'' native to Laos in Southeast Asia. Fossil species are known from the Oligocene and Miocene of Asia and eastern Europe.
"La ...: Laotian rock rat
The rodent parvorder or infraorder Phiomorpha comprises several living and extinct families found wholly or largely in Africa. Along with Anomaluromorpha and perhaps the extinct Zegdoumyidae, it represents one of the few early colonizations of A ...
**:*Family Bathyergidae: African mole rats
**:*Family Heterocephalidae: naked mole-rat
**:*Family Hystricidae: Old World porcupines
**:*Family Petromuridae: dassie rat
**:*Family Thryonomyidae: cane rats
*****Family Erethizontidae: New World porcupines
The family Chinchillidae is in the order Rodentia and consists of the chinchillas, the viscachas, and their fossil relatives. This family is restricted to southern and western South America, mostly living in mountainous regions of the Andes ...: chinchilla
Chinchillas are either of two species (''Chinchilla chinchilla'' and ''Chinchilla lanigera'') of crepuscular rodents of the parvorder Caviomorpha. They are slightly larger and more robust than ground squirrels, and are native to the Andes mounta ...s, viscachas
*****Family Dinomyidae: pacaranas
*****Family Caviidae: cavies, including Guinea pig
The guinea pig or domestic guinea pig (''Cavia porcellus''), also known as the cavy or domestic cavy (), is a species of rodent belonging to the genus '' Cavia'' in the family Caviidae. Breeders tend to use the word ''cavy'' to describe the ...s and the capybara
*****Family Dasyproctidae: agoutis
*****Family Cuniculidae: paca
A paca is a member of the genus ''Cuniculus'' of ground-dwelling, herbivorous rodents in South and Central America. It is the only genus in the family Cuniculidae. Pacas are large rodents with dots and stripes on their sides, short ears, and ...s
*****Family Abrocomidae: chinchilla rats
A tuco-tuco is a neotropical rodent in the family Ctenomyidae.Parada, A., G. D’Elia, C.J. Bidau, and E.P. Lessa. 2011. Species Groups and the Evolutionary Diversification of Tuco-Tucos, genus ''Ctenomys'' (Rodentia: Ctenomyidae). ''Journal of M ...: tuco-tuco
A tuco-tuco is a neotropical rodent in the family Ctenomyidae.Parada, A., G. D’Elia, C.J. Bidau, and E.P. Lessa. 2011. Species Groups and the Evolutionary Diversification of Tuco-Tucos, genus ''Ctenomys'' (Rodentia: Ctenomyidae). ''Journal of M ...s
*****Family Echimyidae: spiny rats, hutias, and coypu
*****Family Octodontidae: octodonts
*:**Family Dipodidae: jerboas
*:**Family Sminthidae: birch mice
*:**Family Zapodidae: jumping mice
*:**Family Calomyscidae: mouse-like hamsters
*:**Family Cricetidae: hamsters, New World rats and mice, muskrats, voles, lemmings
*:**Family Muridae: true mice and rats, gerbils, spiny mice, crested rat
The maned rat or (African) crested rat (''Lophiomys imhausi'') is a nocturnal, long-haired and bushy-tailed East African rodent that superficially resembles a porcupine. The world's only poisonous rodent, the maned rat borrows toxins from plant ...
*:**Family Nesomyidae: climbing mice, rock mice, white-tailed rat, Malagasy rats and mice
*:**Family Platacanthomyidae: spiny dormice
*:**Family Spalacidae: mole rats, bamboo rats, zokors
The family Aplodontiidae also known as Aplodontidae, Haplodontiidae or Haploodontini is traditionally classified as the sole extant family of the suborder Protrogomorpha. It may be the sister family of the Sciuridae.
There are fossils from the O ...: mountain beaver
The mountain beaver (''Aplodontia rufa'')Other names include mountain boomer, ground bear, giant mole, gehalis, lesser sasquatch, sewellel, suwellel, showhurll, showtl, and showte, as well as a number of Chinookan and other Native American terms ...
*::*Family Gliridae (also Myoxidae, Muscardinidae): dormice
*::*Family Sciuridae: squirrels, including chipmunks, prairie dogs, marmots
Interaction with humans
While rodents are not the most seriously threatened order of mammals, there are 168 species in 126 genera that are said to warrant conservation attention
[ in the face of limited appreciation by the public. Since 76 percent of rodent genera contain only one species, much phylogenetic diversity could be lost with a comparatively small number of extinctions. In the absence of more detailed knowledge of species at risk and accurate taxonomy, conservation must be based mainly on higher taxa (such as families rather than species) and geographical hot spots.] Several species of rice rat
Oryzomyini is a tribe of rodents in the subfamily Sigmodontinae of the family Cricetidae. It includes about 120 species in about thirty genera,Weksler et al., 2006, table 1 distributed from the eastern United States to the southernmost parts of ... have become extinct since the 19th century, probably through habitat loss and the introduction of alien species. In Colombia, the brown hairy dwarf porcupine was recorded from only two mountain localities in the 1920s, while the red crested soft-furred spiny rat is known only from its type locality on the Caribbean coast, so these species are considered vulnerable. The IUCN Species Survival Commission writes "We can safely conclude that many South American rodents are seriously threatened, mainly by environmental disturbance and intensive hunting".
The "three now cosmopolitan commensal rodent pest species" [ 3–5 March 1992] (the brown rat, the black rat and the house mouse) have been dispersed in association with humans, partly on sailing ships in the Age of Exploration
The Age of Discovery (or the Age of Exploration), also known as the early modern period, was a period largely overlapping with the Age of Sail, approximately from the 15th century to the 17th century in European history, during which seafaring ..., and with a fourth species in the Pacific, the Polynesian rat (''Rattus exulans''), have severely damaged island biotas around the world. For example, when the black rat reached Lord Howe Island
Lord Howe Island (; formerly Lord Howe's Island) is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, part of the Australian state of New South Wales. It lies directly east of mainland Po ... in 1918, over 40 percent of the terrestrial bird species of the island, including the Lord Howe fantail, became extinct within ten years. Similar destruction has been seen on Midway Island
Midway Atoll (colloquial: Midway Islands; haw, Kauihelani, translation=the backbone of heaven; haw, Pihemanu, translation=the loud din of birds, label=none) is a atoll in the North Pacific Ocean. Midway Atoll is an insular area of the Unit ... (1943) and Big South Cape Island
Big South Cape Island or Taukihepa is an offshore island of New Zealand to the west of the southern tip of Stewart Island / Rakiura. The island has no permanent inhabitants but muttonbirders visit the island to catch the sooty shearwater, known i ... (1962). Conservation projects can with careful planning completely eradicate these pest rodents from islands using an anticoagulant rodenticide such as brodifacoum. [ This approach has been successful on the island of ] Lundy
Lundy is an English island in the Bristol Channel. It was a micronation from 1925–1969. It forms part of the district of Torridge in the county of Devon.
About long and wide, Lundy has had a long and turbulent history, frequently chang ... in the United Kingdom, where the eradication of an estimated 40,000 brown rats is giving populations of Manx shearwater and Atlantic puffin a chance to recover from near-extinction.
Rodents have also been susceptible to climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ..., especially species living on low-lying islands. The Bramble Cay melomys
The Bramble Cay melomys, or Bramble Cay mosaic-tailed rat (''Melomys rubicola''), is a recently extinct species of rodent in the family Muridae and subfamily Murinae. It was an endemic species of the isolated Bramble Cay, a low-lying vegetat ..., which lived in the northernmost point of land of Australia
Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ..., was the first mammal species to be declared extinct as a consequence of human-caused climate change.
Humanity has long used animal skins for clothing, as the leather is durable and the fur provides extra insulation.
[ The native people of North America made much use of beaver pelts, tanning and sewing them together to make robes. Europeans appreciated the quality of these and the North American fur trade developed and became of prime importance to early settlers. In Europe, the soft underfur known as "beaver wool" was found to be ideal for felting and was made into beaver hats and trimming for clothing. Later, the ] coypu
The nutria (''Myocastor coypus''), also known as the coypu, is a large, herbivorous, semiaquatic rodent.
Classified for a long time as the only member of the family Myocastoridae, ''Myocastor'' is now included within Echimyidae, the family of t ... took over as a cheaper source of fur for felting and was farmed extensively in America and Europe; however, fashions changed, new materials became available and this area of the animal fur industry declined. The chinchilla
Chinchillas are either of two species (''Chinchilla chinchilla'' and ''Chinchilla lanigera'') of crepuscular rodents of the parvorder Caviomorpha. They are slightly larger and more robust than ground squirrels, and are native to the Andes mounta ... has a soft and silky coat and the demand for its fur was so high that it was nearly wiped out in the wild before farming took over as the main source of pelts. [ The quills and guardhairs of porcupines are used for traditional decorative clothing. For example, their guardhairs are used in the creation of the Native American "porky roach" headdress. The main quills may be dyed, and then applied in combination with thread to embellish leather accessories such as knife sheaths and leather bags. Lakota women would harvest the quills for quillwork by throwing a blanket over a porcupine and retrieving the quills it left stuck in the blanket.
At least 89 species of rodent, mostly Hystricomorpha such as guinea pigs, agoutis and capybaras, are eaten by humans; in 1985, there were at least 42 different societies in which people eat rats.
Guinea pigs were first raised for food around 2500 B.C. and by 1500 B.C. had become the main source of meat for the Inca Empire
The Inca Empire (also known as the Incan Empire and the Inka Empire), called ''Tawantinsuyu'' by its subjects, ( Quechua for the "Realm of the Four Parts", "four parts together" ) was the largest empire in pre-Columbian America. The adm .... Dormice were raised by the Romans in special pots called "gliraria", or in large outdoor enclosures, where they were fattened on walnuts, chestnuts, and acorns. The dormice were also caught from the wild in autumn when they were fattest, and either roasted and dipped into honey or baked while stuffed with a mixture of pork, pine nuts, and other flavorings. Researchers found that in Amazonia, where large mammals were scarce, pacas and common agoutis accounted for around 40 percent of the annual game taken by the indigenous people, but in forested areas where larger mammals were abundant, these rodents constituted only about 3 percent of the take.
Guinea pigs are used in the cuisine of Cuzco, Peru, in dishes such as ''cuy al horno'', baked guinea pig. [ The traditional Andean stove, known as a ''qoncha'' or a ''fogón'', is made from mud and clay reinforced with straw and hair from animals such as guinea pigs. In Peru, there are at any time 20 million domestic guinea pigs, which annually produce 64 million edible carcasses. This animal is an excellent food source since the flesh is 19% protein.] In the United States, mostly squirrels, but also muskrats, porcupines, and groundhogs are eaten by humans. The Navajo people ate prairie dog baked in mud, while the Paiute ate gophers, squirrels, and rats.
Rodents are used widely as model organisms in animal testing.
Albino mutant rats
Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include ''Neotoma'' (pack rats), '' Bandicota'' (bandicoot ... were first used for research in 1828 and later became the first animal domesticated for purely scientific purposes. Nowadays, the house mouse is the most commonly used laboratory rodent, and in 1979 it was estimated that fifty million were used annually worldwide. They are favored because of their small size, fertility, short gestation period and ease of handling and because they are susceptible to many of the conditions and infections that afflict humans. They are used in research into genetics
Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar work ..., developmental biology, cell biology, oncology
Oncology is a branch of medicine that deals with the study, treatment, diagnosis and prevention of cancer. A medical professional who practices oncology is an ''oncologist''. The name's etymological origin is the Greek word ὄγκος (''ó ... and immunology
Immunology is a branch of medicineImmunology for Medical Students, Roderick Nairn, Matthew Helbert, Mosby, 2007 and biology that covers the medical study of immune systems in humans, animals, plants and sapient species. In such we can see ther .... Guinea pigs were popular laboratory animals until the late 20th century; about 2.5 million guinea pigs were used annually in the United States for research in the 1960s, but that total decreased to about 375,000 by the mid-1990s. In 2007, they constituted about 2% of all laboratory animals. [ Guinea pigs played a major role in the establishment of germ theory in the late 19th century, through the experiments of Louis Pasteur, ] Émile Roux
Pierre Paul Émile Roux FRS (17 December 18533 November 1933) was a French physician, bacteriologist and immunologist. Roux was one of the closest collaborators of Louis Pasteur (1822–1895), a co-founder of the Pasteur Institute, and respons ..., and Robert Koch. They have been launched into orbital space flight several times—first by the USSR
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nati ... on the Sputnik 9 biosatellite
A bio satellite is an artificial satellite designed to carry plants or animals in outer space. They are used to research the effects of space (cosmic radiation, weightlessness, etc.) on biological matter while in orbit around a celestial body. ... of 9 March 1961, with a successful recovery. The naked mole rat is the only known mammal that is poikilothermic; it is used in studies on thermoregulation
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperatur .... It is also unusual in not producing the neurotransmitter substance P, a fact which researchers find useful in studies on pain.
Rodents have sensitive olfactory abilities, which have been used by humans to detect odors or chemicals of interest. The Gambian pouched rat
The Gambian pouched rat (''Cricetomys gambianus''), also commonly known as the African giant pouched rat, is a species of nocturnal pouched rat of the giant pouched rat genus ''Cricetomys'', in the family Nesomyidae. It is among the largest mu ... is able to detect tuberculosis
Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, ... bacilli with a sensitivity of up to 86.6%, and specificity (detecting the absence of the bacilli) of over 93%; the same species has been trained to detect land mine
A land mine is an explosive device concealed under or on the ground and designed to destroy or disable enemy targets, ranging from combatants to vehicles and tanks, as they pass over or near it. Such a device is typically detonated automati ...s. Rats have been studied for possible use in hazardous situations such as in disaster zones. They can be trained to respond to commands, which may be given remotely, and even persuaded to venture into brightly lit areas, which rats usually avoid.
Rodents including guinea pigs, mice, rats, hamsters, gerbils, chinchillas, degus and chipmunks make convenient pets able to live in small spaces, each species with its own qualities. Most are normally kept in cages of suitable sizes and have varied requirements for space and social interaction. If handled from a young age, they are usually docile and do not bite. Guinea pigs have a long lifespan and need a large cage.
Rats also need plenty of space and can become very tame, can learn tricks and seem to enjoy human companionship. Mice are short-lived but take up very little space. Hamsters are solitary but tend to be nocturnal. They have interesting behaviors, but unless handled regularly they may be defensive. Gerbils are not usually aggressive, rarely bite and are sociable animals that enjoy the company of humans and their own kind.
As pests and disease vectors
Some rodent species are serious agricultural
PESTS was an anonymous American activist group formed in 1986 to critique racism, tokenism, and exclusion in the art world. PESTS produced newsletters, posters, and other print material highlighting examples of discrimination in gallery represent ..., eating large quantities of food stored by humans. For example, in 2003, the amount of rice lost to mice and rats in Asia was estimated to be enough to feed 200 million people. Most of the damage worldwide is caused by a relatively small number of species, chiefly rats and mice. In Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Gui ... and Tanzania
Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands ..., rodents reduce crop yields by around fifteen percent, while in some instances in South America losses have reached ninety percent. Across Africa, rodents including '' Mastomys'' and '' Arvicanthis'' damage cereals, groundnuts, vegetables and cacao. In Asia, rats, mice and species such as '' Microtus brandti'', '' Meriones unguiculatus
The Mongolian gerbil or Mongolian jird (''Meriones unguiculatus'') is a small rodent belonging to the subfamily Gerbillinae. Their body size is typically , with a tail, and body weight , with adult males larger than females. The animal is use ...'' and '' Eospalax baileyi'' damage crops of rice, sorghum, tubers, vegetables and nuts. In Europe, as well as rats and mice, species of '' Apodemus'', ''Microtus'' and in occasional outbreaks '' Arvicola terrestris
The European water vole or northern water vole (''Arvicola amphibius''), is a semi-aquatic rodent. It is often informally called the water rat, though it only superficially resembles a true rat. Water voles have rounder noses than rats, deep brow ...'' cause damage to orchards, vegetables and pasture as well as cereals. In South America, a wider range of rodent species, such as '' Holochilus
''Holochilus'' is a genus of semiaquatic rodents in the tribe Oryzomyini of family Cricetidae,* sometimes called marsh rats. It contains five living species, '' H. brasiliensis'', '' H. chacarius'', '' H. nanus'', '' H. oxe'', and '' H. sciureus' ...'', '' Akodon'', '' Calomys
Vesper mice are rodents belonging to a genus ''Calomys''. They are widely distributed in South America. Some species are notable as the vectors of Argentinian hemorrhagic fever and Bolivian hemorrhagic fever.
The genus was originally named ''H ...'', '' Oligoryzomys
''Oligoryzomys'' is a genus of rodents in the tribe Oryzomyini of family Cricetidae. Many species are known as pygmy rice rats or colilargos.Musser and Carleton, 2005 The genus is found from Mexico to Tierra del Fuego and includes approximately 1 ...'', '' Phyllotis
''Phyllotis'' is a genus of rodent in the family Cricetidae. These mice are commonly confused with '' Auliscomys, Graomys'' and '' Loxodontomys.'' ''.'' In order to tell these genera apart, one must look at the tail. Species in the genus ''Phy ...'', '' Sigmodon'' and '' Zygodontomys
''Zygodontomys'' is a genus of rodent in the tribe Oryzomyini of the family Cricetidae. Its closest relative may be '' Scolomys''. It ranges from Central America east to the Guianas
The Guianas, sometimes called by the Spanish loan-word ''Gu ...'', damage many crops including sugar cane, fruits, vegetables, and tubers. [
Rodents are also significant vectors of disease.] The black rat, with the Northern rat flea, fleas that it carries, plays a primary role in spreading the bacterium ''Yersinia pestis'' responsible for bubonic plague, and carries the organisms responsible for typhus, Weil's disease, toxoplasmosis and trichinosis. [ A number of rodents carry hantaviruses, including the Puumala virus, Puumala, Dobrava virus, Dobrava and Saaremaa viruses, which can infect humans. Rodents also help to transmit diseases including babesiosis, cutaneous leishmaniasis, human granulocytic anaplasmosis, Lyme disease, Omsk hemorrhagic fever, Powassan virus, rickettsialpox, relapsing fever, Rocky Mountain spotted fever, and West Nile virus.
Because rodents are a nuisance and endanger public health, human societies often attempt to control them. Traditionally, this involved poisoning and trapping, methods that were not always safe or effective. More recently, integrated pest management attempts to improve control with a combination of surveys to determine the size and distribution of the pest population, the establishment of tolerance limits (levels of pest activity at which to intervene), interventions, and evaluation of effectiveness based on repeated surveys. Interventions may include education, making and applying laws and regulations, modifying the habitat, changing farming practices, and biological control using pathogens or predators, as well as Rodenticide, poisoning and trapping. The use of pathogens such as ''Salmonella'' has the drawback that they can infect man and domestic animals, and rodents often become resistant. The use of predators including ferrets, mongooses and monitor lizards has been found unsatisfactory. Domestic and feral cats are able to control rodents effectively, provided the rodent population is not too large. In the UK, two species in particular, the house mouse and the brown rat, are actively controlled to limit damage in growing crops, loss and contamination of stored crops and structural damage to facilities, as well as to comply with the law.]
* Fe, Fi, Fo, Fum, and Phooey, mice who orbited the Moon on Apollo 17
* Mouse models of breast cancer metastasis
** Carleton, M. D.; Musser, G. G. "Order Rodentia", pages 745–752 in Wilson & Reeder (2005).
Zoology, osteology, comparative anatomy
ArchéoZooThèque : Rodent osteology
ArchéoZooThèque : Rodent skeleton drawings
Rodent Species Fact Sheets
from the National Pest Management Association on Deer Mice, Norway Rats, and other rodent species
Articles containing video clips
Extant Thanetian first appearances
Taxa named by Thomas Edward Bowdich