From Wikipedia, the free encyclopedia

Mouse Fossil range: Late Miocene - Recent
House mouse, Mus musculus
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Rodentia Superfamily: Muroidea Family: Muridae Subfamily: Murinae Genus: Mus Linnaeus, 1758

A mouse (plural mice) is a rodent that belongs to one of numerous species of small mammals. The best known mouse species is the common house mouse (Mus musculus). It is found in nearly all countries and, like the laboratory mouse, serves as an important model organism in biology, and is also a popular pet. The American white-footed mouse (Peromyscus leucopus) and the deer mouse (Peromyscus maniculatus) also sometimes live in houses. These species of mice live commensally with humans.

Although they may live up to two years in the lab, the average mouse in the wild lives only about 5 months, primarily due to heavy predation. Cats, wild dogs, foxes, birds of prey, snakes and even certain kinds of insects have been known to prey heavily upon mice. Nevertheless, due to its remarkable adaptability to almost any environment, and its ability to live commensally with humans, the mouse is regarded to be the third most successful mammalian species living on Earth today, after humans and the rat.

Mice can be harmful pests, damaging and eating crops and spreading diseases through their parasites and feces. In the Western United States, breathing dust that has come in contact with mouse feces has been linked to the deadly hantavirus. The original motivation for the domestication of cats is thought to have been for their predation of mice and their relatives, the rats.

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Body and behavior

Mice are small rodents, resembling diminutive rats. They usually have pointed snouts and small ears. The body is typically elongated with slender, usually hairless tails, but different types of mice show large variations. Body dimensions vary considerably by species, though some approximate values are available: total length 28-130 mm, mass 2.5 to >34g.^[1]

Mice generally live on an herbivore diet, but are actually omnivores; they will eat meat, the dead bodies of other mice, and have been observed to self-cannibalise their tails during starvation.^{[citation needed]} Grasshopper mice are an exception to the rule, being the only fully carnivorous mice. Mice eat grains, fruits, and seeds for a regular diet, which is the main reason they damage crops. They are also known to eat their own feces.^{[citation needed]} Mice are generally thought to enjoy cheese and people sometimes use it as mousetrap bait, but mice actually do not like cheese due to its fatty texture. Instead, they like food that contains high sugar, although chocolate is toxic to them.^[2]

Mice are social animals, preferring to live in groups. Male rivalry can become harmful for the animals, especially when a group is confined to a small space. The natural habitats of the mouse are very diverse. Mice can be found in forests, savannahs, grasslands and rocky habitats.^[1] In Africa they tend to particularly like forest edge, derived savannah, and (as elsewhere) agricultural areas. Mice build nests for protection and warmth, but species differ in their preferences: M. minutoides nests in shallow burrows; M. caroli and M. cervicolor burrow; and M. shortridgei and M. pahari nest aboveground. Most species will construct nests of grass, fibers, and shredded material.^[1] Mice do hibernate.

The mouse has dichromatic vision, lacking a photopigment that can detect red light.^[3] There are diseases known to be spread by mice and rats which include:

• Rickettsial pox a disease similar to chicken pox and is spread to people by mites that are usually found on mice.

• Rat bite fever is spread to people when they are bitten by an infected mouse, rat or rodent.

• Food poisoning (namely salmonellosis) is spread to people when food, food preparation surfaces or dishes are contaminated by saliva, urine or feces from a mouse.

• Mice can spread parasites to people such as trichinosis and tapeworms.

• Hantavirus is a respiratory disease that is carried by small rodents, especially deer mice. It is spread to people when they breathe in dust that contains the rodents infected saliva, urine or feces. Although uncommon, people can also get hantavirus if they are bitten by an infected mouse.

• Plague is spread to people when they come in contact with fleas from infected rodents or when people are bitten by infected rodents. However, today plague is usually spread to people by rodents like prairie dogs and squirrel.

Taxonomy of the genus Mus

The term "mouse" in common usage is roughly equivalent to the taxonomic term Mus, while house mouse is equivalent to Mus musculus. In common language the term "mouse" often refers incorrectly to Mus musculus. However, there are 41 species of mice (in the genus Mus); see table below.

Genus Mus
Subgenus Pyromys	Subgenus Coelomys	Subgenus Mus		Subgenus Nannomys
Mus platythrix Mus saxicola Mus philipsi Mus shortridgei Mus fernandoni	Mus mayori Mus pahari Mus crociduroides Mus vulcani Mus famulus	Mus caroli Mus cervicolor Mus cookii Mus cypriacus Mus booduga Mus terricolor	Mus musculus Mus spretus Mus macedonicus Mus spicelegus Mus fragilicauda Mus nitidulus	Mus callewaerti Mus setulosus Mus triton Mus bufo Mus tenellus	Mus haussa Mus mattheyi Mus indutus Mus setzeri Mus musculoides	Mus minutoides Mus orangiae Mus mahomet Mus sorella Mus kasaicus	Mus neavei Mus oubanguii Mus goundae Mus baoulei

[edit] Nutrition

Mice should be fed a commercial pelleted mouse or rodent diet and water ad lib. These diets are nutritionally complete and do not require supplementation. Food intake is approximately 15g/100g BW/day; water intake is approximately 15 ml/100g BW/day. ^[4]

Reproduction

Breeding onset is at about 50 days of age in both females and males, although females may have their first estrus at 25-40 days. Mice are polyestrous and breed year round; ovulation is spontaneous. The duration of the estrous cycle is 4-5 days and estrus itself lasts about 12 hours, occurring in the evening. Vaginal smears are useful in timed matings to determine the stage of the estrous cycle. Mating is usually nocturnal and may be confirmed by the presence of a copulatory plug in the vagina up to 24 hours post-copulation. The presence of sperm on a vaginal smear is also a reliable indicator of mating. ^[4]

Female mice housed together tend to go into anestrus and do not cycle. If exposed to a male mouse or the pheromones of a male mouse, most of the females will go into estrus in about 72 hours. This synchronization of the estrous cycle is known as the Whitten effect. The exposure of a recently bred mouse to the pheromones of a strange male mouse may prevent implantation (or pseudopregnancy), a phenomenon known as the Bruce effect. ^[4]

The average gestation period is 20 days. A fertile postpartum estrus occurs 14-24 hours following parturition, and simultaneous lactation and gestation prolongs gestation 3-10 days due to delayed implantation. The average litter size is 10-12 during optimum production, but is highly strain dependent. As a general rule, inbred mice tend to have longer gestation periods and smaller litters than outbred and hybrid mice. The young are called pups and weight 0.5-1.5 grams at birth, are hairless, and have closed eyelids and ears. Cannibalism is uncommon, but females should not be disturbed during parturition and for at least 2 days postpartum. Pups are weaned at 3 weeks of age; weaning weight is 10-12 grams. If the postpartum estrus is not utilized, the female resumes cycling 2-5 days postweaning. ^[4]

Newborn male mice are distinguished from newborn females by noting the greater anogenital distance and larger genial papilla in the male. This is best accomplished by lifting the tails of litter mates and comparing perineums. ^[4]

Laboratory mice

Mice are the most commonly utilized animal research model with hundreds of established inbred, outbred, and transgenic strains. In the United States, they are not covered under the Animal Welfare Act (AWA) (administered by the USDA, APHIS) as an animal. However, the Public Health Service Act (PHS) as administered by the National Institutes of Health (NIH) does cover their humane treatment.

Mice are common experimental animals in biology and psychology primarily because they are mammals, and thus share a high degree of homology with humans. The mouse genome has been sequenced, and virtually all mouse genes have human homologs. They can also be manipulated in ways that would be considered unethical to do with humans. Mice are a primary mammalian model organism, as are rats.

There are many additional benefits of mice in laboratory research. Mice are small, inexpensive, easily maintained, and can reproduce quickly. Several generations of mice can be observed in a relatively short period of time. Mice are generally very docile if raised from birth and given sufficient human contact. However, certain strains have been known to be quite temperamental.

History

Mouse-like species are among the oldest mammals. It has been proposed that higher mammals evolved from rodent-like species many millions of years ago.

Mice have been known to humans since antiquity. The Romans differentiated poorly between mice and rats, calling rats Mus Maximus (big mouse) and referring to mice as Mus Minimus (little mouse). In Spanish similar term are in use: ratón for mouse and rata for rat.^[5]

Discoloration in mice was supposedly first noticed in China by 1100 BC, where a white mouse was discovered. However, there is sufficient evidence to believe that white mice were first noticed before that, in the times of the Greeks and Ancient Rome.

The word "mouse" and the word muscle are related. Muscle stems from musculus meaning small mouse - possibly because of a similarity in shape.^[6][7] The word "mouse" is a cognate of Sanskrit mush meaning 'to steal,' which is also cognate with mys in Old Greek and mus in Latin.^[8]

Mice as food

Humans have eaten mice since prehistoric times. They are still eaten as a delicacy throughout eastern Zambia and northern Malawi, where they are an important source of protein.[1]

A common use of mice is to feed many species of snakes, lizards, tarantulas, and birds of prey. Most US pet stores now carry mice for this purpose. Because they breed quickly, grow quickly, are easy to care for, and can be sold in a wide variety of sizes. This makes them suitable for consumption by animals of many different sizes. Mice also seem to be a desirable food item for a very large variety of carnivores. Common terms used to refer to different age/size mice are pinkies, fuzzies, hoppers, and adults. Pinkies are newborn mice that have not yet grown fur. Fuzzies have some fur but are generally not very mobile, hoppers have a full coat of hair and are fully mobile but are smaller than adult mice. These terms also refer to the various growth stages of rats (also see Fancy rat).

From Wikipedia, the free encyclopedia

Brown Rat
Conservation status
Least concern [1]
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Rodentia Family: Muridae Subfamily: Murinae Genus: Rattus Species: R. norvegicus
Binomial name
Rattus norvegicus (Berkenhout, 1769)
Brown Rat range

The brown rat, common rat, Norway rat, Norwegian rat or wharf rat (Rattus norvegicus) is one of the best-known and common rats, and also one of the largest. It is not known for certain why it is named Rattus norvegicus (Norwegian rat) as it did not originate in Norway, but John Berkenhout, the author of the 1769 book "Outlines of the Natural History of Great Britain", is most likely responsible for the misnomer. Berkenhout gave the brown rat the binomial name Rattus norvegicus believing that the rat had migrated to England from Norwegian ships in 1728, although no brown rat had entered Norway at that time, instead coming from Denmark. Thought to have originated in northern China, this rodent has now spread to all continents (except Antarctica) and is the dominant rat in Europe and much of North America. It lives wherever humans live, particularly in urban areas. Selective breeding of Rattus norvegicus has produced the laboratory rat, an important model organism in biological research, as well as pet rats.

Description

The fur is coarse and usually brown or dark grey, the underparts are lighter grey or brown. The length can be up to 25 cm (10 in.), with the tail a further 25 cm (the same as the body length). Adult body weight averages 350 g in males and about 250 g in females, but a very large individual can reach 500 g. Rats weighing over a kilogram are exceptional, and stories of rats as big as cats are exaggerations, or misidentifications of other rodents such as the coypu and muskrat. Brown rats have acute hearing and are sensitive to ultrasound, and also possess a very highly developed olfactory sense. Their average heart rate is 300 to 400 beats per minute, with a respiratory rate of around 100 per minute. Their vision is poor and they are unable to detect colour and are blind to long-wave light.

Food, habitat and behavior

The brown rat is a true omnivore and will consume almost anything, but with cereals forming a substantial part of the diet. Martin Schein, founder of the Animal Behavior Society in 1964, studied the diet of brown rats and came to the conclusion in his paper "A Preliminary Analysis of Garbage as Food for the Norway Rat" that the most-liked food of brown rats was (in order) scrambled eggs, macaroni and cheese, and cooked corn kernels. Their least-liked food was raw beets, peaches, and raw celery. They are usually active at night and are good swimmers, both on the surface and underwater, but (unlike the related Black rat Rattus rattus) are poor climbers. They dig well, and often excavate extensive burrow systems. A 2007 study found rats to possess metacognition, a mental ability previously only found in humans and some primates.^[2]

Breeding

The brown rat can breed throughout the year if conditions are suitable, a female producing up to five litters a year. The gestation period is only 1-2 months and litters can number up to fourteen, although seven is common. The maximum life span is up to three years, although most barely manage one. A yearly mortality rate of 95% is estimated, with predators and interspecific conflict as major causes. Brown rats live in large hierarchical groups, either in burrows or subsurface places such as sewers and cellars. When food is in short supply, the rats lower in social order are the first to die. If a large fraction of a rat population is exterminated, the remaining rats will increase their reproductive rate, and quickly restore the old population level.

Rats live almost everywhere people live. It is often said that there are as many rats in cities as people, but this varies from area to area depending on climate, etc. It is probable that New York City (with a severe winter climate), for instance, has only 250,000 rats, not eight million. However, the UK official National Rodent Survey^{[citation needed]} found a 2003 UK population of 60 million brown rats, about equal to the UK human population; winters in Britain are much warmer, making rat survival higher. Brown rats in cities tend not to wander extensively, often staying within 20 meters (65 ft) of their nest if a suitable concentrated food supply is available, but they will range more widely where food availability is lower.

The only way to truly combat the rat problem is reduce the food supply, e.g., garbage left out on the street. Rats have evolved a protective mechanism for avoiding rodenticides and other poisons. Despite their omnivorous habits, they cautiously eat new things and will only take small quantities when encountering them. In addition, their young are averse to eating any new substance that was not first safely imbibed through the mother's milk. Hence, any efforts to use a particular poison to control their growth will result in the natural selection of those who will not imbibe the same poison.

Rat-free zones

The only rat-free zones in the world are the Arctic, the Antarctic, some especially isolated islands, the province of Alberta in Canada, and certain conservation areas in New Zealand.

Antarctica is almost completely covered by ice and has no permanent human inhabitants, making it uninhabitable by rats. The Arctic has extremely cold winters that rats cannot survive outdoors, and the human population density is extremely low making it difficult for rats to travel from one habitation to another. When the occasional rat infestation is noticed and eliminated, the rats are unable to re-infest it from an adjacent one. Isolated islands are also able to eliminate rat populations because of low human population density and geographic distance from other rat populations.

Alberta is unusual in that rat infestation was prevented by deliberate government action. Although it is a major agricultural area and has a fairly high human population density, it is far from any seaport and only a portion of its eastern boundary with Saskatchewan provides a favorable entry route for rats. They cannot survive in the boreal forest to the north, the Rocky Mountains to the west, nor the semi-arid High Plains of Montana to the south. The first rat did not reach Alberta until 1950, and in 1951 the province launched an extremely aggressive rat-control program that included shooting and poisoning rats, and bulldozing, burning down, and blowing up rat-infested buildings. In the first year of the program 64 tonnes of arsenic trioxide was spread in 8,000 buildings (8 kg/building) on 2,700 farms along the Saskatchewan border. Fortunately, in 1953 the much less toxic and more effective poison Warfarin was introduced, and since then the control program has consumed between 5 and 13 tonnes of Warfarin annually. By 1960 the number of rat infestations in Alberta had dropped below 200 per year and has remained low ever since.^[3] Any wild rat population is eliminated by the government Rat Patrol immediately after it is detected. The effort is aided by hundreds of pest control officers and thousands of local citizens, who will not tolerate the introduction of rats. The laws regarding rats are draconian and firmly enforced. Only zoos, universities, and research institutes are allowed to own caged rats, and possession of an unlicensed rat (including pet rats) is punishable by a $5,000 fine or 60 days in jail. The adjacent and similarly landlocked province of Saskatchewan initiated a rat control program in 1963, and has managed to reduce the number of rats in the province substantially.

Rats pose a serious threat to many of New Zealand's native animals. Rat eradication programmes within New Zealand have led to rat-free zones on offshore islands and even on fenced "ecological islands" on the mainland. Before an eradication effort was launched in 2001, the sub-antarctic Campbell Island had the highest population density of rats in the world[1].

Diseases

Brown rats carry some diseases, including Weil's disease, cryptosporidiosis, Viral hemorrhagic fever (VHF), Q fever and hantavirus pulmonary syndrome. Unlike the black rat, brown rats rarely if ever carry bubonic plague.

Brown rats in science

In 1895, Clark University in Worcester, Massachusetts (United States) established a population of domestic white brown rats to study the effects of diet and for other physiological studies. Over the years, rats have been used in many experimental studies, which have added to our understanding of genetics, diseases, the effects of drugs, and other topics that have provided a great benefit for the health and wellbeing of humankind. Laboratory rats have also proved valuable in psychological studies of learning and other mental processes (Barnett 2002).

Domestic rats differ from wild rats in many ways. They are calmer and less likely to bite; they can tolerate greater crowding; they breed earlier and produce more offspring; and their brains, livers, kidneys, adrenal glands, and hearts are smaller (Barnett 2002).

Selective breeding of the brown rat has produced the albino laboratory rat. Like mice, these rats are frequently subjects of medical, psychological and other biological experiments and constitute an important model organism. This is because they grow quickly to sexual maturity and are easy to keep and to breed in captivity. When modern biologists refer to "rats", they almost always mean Rattus norvegicus.

Scientists have bred many strains or "lines" of rats specifically for experimentation. Most are derived from the albino Wistar rat, which is still widely used. Other popular strains are the Sprague Dawley, Fischer 344^[4] and Holtzman albino strains, and the Long-Evans, and (in the UK) Lister black hooded rats. Inbred strains are also available but are not as commonly used as inbred mice. Generally rat lines are not transgenic because the easy techniques of genetic transformation that work in mice do not work for rats. This has disadvantaged many investigators, who regard many aspects of behavior and physiology in rats as more relevant to humans and easier to observe than in mice and who wish to trace their observations to underlying genes. As a result, many have been forced to study questions in mice that might be better pursued in rats. In October 2003, however, researchers succeeded in cloning two laboratory rats by the problematic technique of nuclear transfer. So rats may begin to see more use as genetic research subjects. Much of the genome of Rattus norvegicus has been sequenced.^[5]

Wistar rat

Wistar rats are an outbred strain of albino rats belonging to the species Rattus norvegicus. This strain was developed at the Wistar Institute for use in biological and medical research, and is notably the first rat strain developed to serve as a model organism at a time when laboratories primarily used Mus musculus, or the common House mouse. Most laboratory rat strains are descended from a colony of rats established at the Wistar Institute in 1906 by American physiologist Henry Donaldson, scientific administrator Milton J. Greenman, and genetic researcher/embryologist Helen Dean King. The is currently one of the most popular rat strains used for laboratory research. It is characterized by its wide head, long ears, and having a tail length that is always less than its body length. The Sprague Dawley and Long-Evans rat strains were developed from Wistar rats.

Sprague Dawley rat

Sprague Dawley rats are an outbred strain of albino laboratory rats belonging to the species Rattus norvegicus. They were originally developed from the Wistar rat strain. They are used widely for experimental purposes because of their calmness and ease of handling. The adult body weight is 250-300g (female), and 450-520g (male). The typical life span is 2.5 - 3.5 years.[2] Sprague Dawley is the registered trademark of Harlan Industries Inc.

Brown rats as pets

 

The brown rat, along with the black rat to a lesser degree, is kept as a pet in many parts of the world. Australia, England, and the United States are just a few of the countries that have formed fancy rat associations similar in nature to the American Kennel Club, establishing standards, orchestrating events, and promoting responsible pet ownership.

Brown rats as pet food

Because of their quick reproduction, rats are also used as live food for captive animals, commonly large reptiles such as snakes. Care must be taken to select rats from breeders who provide a good quality diet and captive living conditions.

There is a large risk to captive animals if they are fed live rats instead of dead rats. A captive animal that is not hungry when it is given a live rat as food may itself become food for the rat. An animal that does not kill the rat quickly enough will often suffer injury, e.g., from being bitten by the rat. Even feedings supervised by the owner of the captive animal can result in an injured or dead animal, as rats are faster than humans and many other animals.^[6]

Objections to the practice of feeding live rats to reptiles include viewing it as cruelty to animals because the rat is not guaranteed a quick or painless death, and equating it to rat baiting or cockfighting, which are illegal in most parts of the world. Reptiles can be conditioned to accept dead rats with coaching, as is the rule with most accredited zoos.

Some countries, such as South Africa, as well as various municipalities worldwide, have banned the feeding of live vertebrate animals (like rats) to predators.^[7]Jump to: navigation, search