Rodents are mammals of chordate,[4]It is commonly known as rat.Each of the upper and lower jaw has a pair of chisel shaped incisors with enamel only on the front edge, which grow for life, so they have the habit of molars.The jaw can move back and forth, suitable for grinding food.There is no canine between the incisors and buccal teeth, and there is a wide tooth gap.There are 3 upper and 3 lower molars, and the number of anterior molars varies from species to species.No more than 2 upper premolars, and no more than 1 lower premolar;The chewing surface of the molars is flat or protuberant, and the chewing surface is born with flat side of the molars concave inward and lobulated.[5]
Rodents are distributed in all continents except Antarctica, as well as in the Arctic Circle and deserts.[6]Rodents have different ecological adaptations.Aquatic rodents such as muskrats and beavers are suitable for swimming in water;The jerboa is suitable for living in the sand;Flying squirrels can glide in the forest.Most rodents use plants as their basic food, and generally prefer to eat young branches and leaves with high water content. In autumn, they tend to eat milk mature or fully mature seeds.Rodents generally have strong fecundity, but there are great differences among species.[5]
Rodents are more harmful to agriculture, forestry and animal husbandry, such as plague, epidemic hemorrhagic fever, leptospirosis, typhus and forest encephalitis.In addition, rats can bite the wires, causing a fire or stopping the factory.[5]
Small and medium-sized mammals with a pair of chisel like incisors, commonly known as rats.These include rats, mice, ground squirrels, gerbils, jerboas and porcupines.The smallest species, such as the nest mouse (Mic romys minutus), usually weighs less than 10 grams;As big as the South American capybara (Hydrochaeris hydrochaeris), its weight can reach 50 kg;The large rodents in China are from XinjiangBeaverCastor fiber can weigh up to 25kg.[1]
Main features
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Each of the upper and lower jaw has a pair of chisel shaped incisors with enamel only on the front edge, which grow for life, so they have the habit of molars.The jaw can move back and forth, suitable for grinding food.There is no canine between the incisors and buccal teeth, and there is a wide tooth gap.There are 3 upper and 3 lower molars, and the number of anterior molars varies from species to species.No more than 2 upper premolars, and no more than 1 lower premolar;The chewing surface of the molars is either flat or protuberant. The chewing surface is made of flat molars with inward concave sides and is lobulated.[1]
Rodent
Life habits
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ecology
Rodents have different ecological adaptations.Aquatic rodents such as muskrats and beavers have webbed toes.Suitable for swimming in water.The hind limbs of the jerboa are developed and suitable for living in the sand.The front and rear limbs of the flying squirrel in the forest are connected by a skin membrane, which can glide in the forest.The zokor has short and thick forelimbs, developed forepaws and incisors, and degenerated eyes and ear shells, all of which are related to its cave life.[1]
Feeding habits
Most rodents feed on plants.Generally, they like to eat young branches and leaves with high water content. In autumn, they tend to eat milk mature or fully mature seeds.The food habits of rats are often closely related to their environment.Rats in agricultural areas, such as house mice, apodemus and hamsters, all feed on seeds;The southern rattan eats sugar cane, rice, sweet potatoes and bananas;Squirrels, Apodemus agrarius and red backed crabs in forest areas mainly feed on forest fruit seeds;The prairie squirrels, voles and early otters mainly feed on the green parts of plants;The underground part of zokor's staple food plant.Rats can also eat widely or narrowly.In addition to eating plants, insect remains are often found in the stomach of ground squirrels, jerboas and hamsters;Rattus norvegicus is famous for eating widely. In addition to eating stems, leaves, fruits and seeds of plants, it also eats insects, molluscs, crustaceans, worms, frogs, fish, birds, etc;A few rats have a narrow feeding habit. For example, early otters mainly feed on the stems and leaves of grass.
The relative food intake of rodents is large, which is related to their small size and large activity.lasiopodomys brandtii Under cage conditions, the amount of fresh grass taken every day and night can reach about 80% of its own weight.The amount of food eaten by rats is related to the quality of food. Usually, rats who eat stems and leaves eat more than those who eat seeds.The feeding habits and quantities of rats may also vary from time to time and from place to place.
Rodents also have the habits of food storage, hibernation (hibernation and summer sleep) and migration.Grain storage and hibernation, especially for rats living in high latitudes, are very important adaptive characteristics, otherwise it is difficult to survive the long winter.Migration is conducive to the regulation of rodent population density and the full use of environmental food resources.The house mouse enters the field in spring and summer and returns to the house in winter, which is also a common example of rat migration.Some rats have large groups and long-distance migration activities. For example, lemmings in the north are named for this habit.[2]
Reproductive development
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Rodents generally have strong fecundity, but there are great differences among species.Larger species tend to be less productive.The beaver breeds one litter every year. The pregnancy period is 105~107 days. Each litter has 1~4 young. The young reach sexual maturity in the second year;The black line hamster can give birth to 3-5 babies every year. The pregnancy period is 19-21 days. Each baby has 1-10 babies, with an average of 4.6 babies. The baby reaches sexual maturity when it is 2-3 months old.In rodents, the fertility of Muridae and Hamster is strong, and most of them can breed more than two litters every year. Many kinds of female rats can mate and become pregnant during lactation, so the small house mouse can breed more than 10 litters every year under suitable environmental conditions.Among various environmental factors, it is generally believed that food conditions can often become the main factor affecting the reproduction of rats.The rats with strong fecundity are easy to form high population density, which will have a great impact on human economy.[1]
economic significance
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Rodents have many impacts on human beings.Mice are the main food for raptors and small carnivorous fur beasts, and are an important link in the food chain of terrestrial biological communities.The burrowing activities of burrowing rats can play a positive role in retaining rainwater and loosening soil.Marmots and other caves can provide shelter for other beneficial animals.Squirrels, beavers, muskrats, marmots and Myocastor coypus are fur animals of great economic value.Gerbil unguiculatus、mesocricetus auratus (Mesocricetus auratus) and deer rats (Peromyscus sp,) can be domesticated and used as experimental animals.The albino strains of Rattus norvegicus and Rattus musculus are common in the laboratory, and the guinea pig (Cavia porcel lus) is domesticated from wild species.[3]
harm
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Rats are particularly harmful to agriculture, forestry and animal husbandry.There are more than 70 kinds of agricultural rodents in China, among which the most harmful ones are Rattus norvegicus, Rattus flavipectus, Rattus flavipectus, Rattus aculeatus, Rattus platypodontis, Rattus musculusApodemus agrarius、Black striped hamster, hamster, Mongolian gerbil, oriental vole, zokor and yellow rat, etc.A small house mouse eats 3~8g a day, and the brown house mouse can consume about 25g of grain every day.In 1969, the number of Mus musculus in northern Xinjiang increased sharply, with an estimated loss of 150 million kg of grain.The bark of young trees is gnawed by the brown backed beetle, and the damage rate of young Chinese pine forests in the secondary forest land of Inner Mongolia can sometimes reach 8~9%.In Ningxia, drilling tree seeds failed to sprout for several years because of jerboa digging.The live broadcast of Korean pine in the northeast forest area was also harmed by rats.In addition to stealing feed and eggs and harming young birds and livestock in the pastoral area, Brandt's vole and rabbit tail rat distributed on the grassland can consume a lot of forage and make some native vegetation become mound vegetation.Rats dig holes in the bank, which can cause the bank to burst and cause floods.And there are many kindsNatural focus diseaseStorage host for.Such as plagueepidemic hemorrhagic fever、Leptospirosis, typhus, forest encephalitis and other diseases are related to rats.In addition, rats can bite the wires, causing a fire or stopping the factory.[2]
classification
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In the past, the order Lagomorpha was regarded as a suborder, which was summarized in the generalized rodents, Duplicidentata.Rodentia is called Simplicidentata.There are 1687 species in 380 genera and 29 families of holorodenta in the world, which is the largest order in mammals.Excluding the introduced species, there are about 184 rodents in China, belonging to 68 genera and 9 families, respectively.[1]
Sciuridae
Strong limbs, sharp claws at toe end, round or flat tail, fluffy tail.Buccal teeth 1-2 · 3/1.3=16~18, with root.There are about 16 genera and 42 species in China, almost all over the country.Such as Sciurus vulgaris, Callosciurus eryth raeus, Eutamias sibiricus, Citellus dauricus, Marmota sibirica, and Ptero mys volans.
Castoridae
Semi aquatic animals.It can weigh up to 30kg.The back foot is webbed.Small eyes.The tail is large and flat, with scales on it.Buccal teeth 1.3/1.3=16, no root.Fur is precious.It can secrete beaver incense and is a valuable spice.There are only two species, one in America and the other is the beaver (Ca stor fiber), which is native to Europe and northern Asia.It is distributed in northern Xinjiang in China.
Cricetidae
Most of them are small, with four forelimbs and five hind limbs.The tail is hairy without scales.Buccal teeth 3/3=12.There are 4 subfamilies, 20 genera and 72 species in China.Such as Cricetulus barabensis, C. triton, Meriones unguiculatus, Myospalax fontanieri, Microtus brandti, Cletheromonmysrufocanus, Myopus schisticolor, and On atra zibethicus.
Rhizomyidae
Strong body, small eyes.Ears are short.The tail is short and hairless or only sparsely hairy.The upper and lower incisors are thick, and the buccal teeth are 3/3=12.Suitable for underground life.There are 2 genera and 4 species in China, all distributed in the south of the Yangtze River.For example, Rhizomys sumatransis.
Muridae
The tail is mostly scaly.The buccal teeth 3/3=12, the occlusal surface of the crown is complex, and the upper molars have three longitudinal teeth, which form transverse ridges after grinding.There are about 16 genera and 43 species in China, such as Rattus norvegicus, Mus musculus, Apodemus agrarius, Micromys minutus, etc.
Gliridae
Weighing 30-100g, it looks like a squirrel and is slightly smaller.Most have long hairy tails.The limbs and toes are short, and the claws are short and curved.The nose is short, the eye socket is large, and the ear is round.Buccal teeth 1.3/1.3=16.There are 2 genera and 2 species in China.Dryomys nitindula is native to Xinjiang.
Zapodidae
Weight: 10-25g.The tail is obviously longer than the body length, and there is no hair bundle at the end.The hind legs are longer.Most species have bright fur, with bright yellow or reddish brown back and white belly.Buccal teeth 0 ～ 1.3/0.3=12 or 14.There are 2 genera and 7 species in China.For example, the Chinese forest jerboa (Sicista conco lor) is distributed in the west and northeast Jilin;Eozapussetchuanus is distributed in Sichuan and southern Gansu.
Dipodidae
The back of the head is wide.The hind legs and tail are very long, with tufts of hair at the end of the tail.The nose is short, the eyes are big, and the ears are big.Buccal teeth 0 ～ 1.3/0.3=12 or 14.It is mainly distributed in grassland, desert and semi desert areas.asFive toed jerboa(Allactaga sibirica), Dipus sagittaStylodipus telum (Stylodipus telecom), etc.
Hystriidae
Large size.There are thorns on the body surface.Buccal teeth 1.3/1.3=16.There are 2 genera and 3 species in China.It is distributed in Shaanxi and provinces to the south of the Yangtze River.Such as Hystrix hodgsoni.[1]
