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name applied to various stout-bodied rodentsrodent,
member of the mammalian order Rodentia, characterized by front teeth adapted for gnawing and cheek teeth adapted for chewing. The Rodentia is by far the largest mammalian order; nearly half of all mammal species are rodents.
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, usually having a pointed muzzle, long slender tail, and dexterous forepaws. It refers particularly to the two species of house rat, Rattus norvegicus, the brown, or Norway, rat and R. rattus, the black, roof, or Alexandrine, rat. Both species originated in Asia, but have spread throughout the world, mostly on board ships. The black rat was common in Europe in the Middle Ages and has been historically implicated in the spreading of plague, but recent research has suggested that the great gerbil or another rodent of Central Asia may have been the source. The black rat has since been largely displaced in cooler regions by the brown rat, which reached Europe early in the 18th cent. and North America by 1775.

The brown rat is the larger of the two, growing up to 10 in. (25 cm) long excluding the naked, scaley tail and sometimes weighing more than a pound (.5 kg). It is commonly brown with whitish underparts and pink ears, feet, and tail. It is a poor climber, but an excellent burrower and swimmer; it is found in the damp basements and sewers of most temperate zone cities. The laboratory white rat is an albino strain of the brown rat.

The black rat is commonly dark gray. It reaches a maximum length of 8 in. (20 cm) and has a longer tail and larger ears than the brown rat. A good climber, the black rat inhabits attics and upper floors in warm areas; it is the common rat of the Mediterranean region, the SE United States, and Central and South America.

Rats are omnivorous, aggressive, intelligent, adaptable, and extremely fecund. Females produce as many as 8 litters each year with as many as 20 young per litter. The gestation period is three weeks, and the young reach sexual maturity in about two months. Rats may live as long as four years. They are social animals but sometimes fight among themselves.

Rats live mostly in and around human settlements, where they have few natural enemies and an abundant source of food. They invade food supplies and cause widespread destruction; they also spread human diseases such as typhus and tularemia. Despite human efforts to exterminate rats, the house rat population is probably equal to the human population.

Besides the house rats, the genus Rattus contains several hundred wild-living species. In addition, many other members of several different rodent families are called rats, e.g., the bandicoot ratbandicoot rat,
giant rat of southern Asia, unrelated to true bandicoots. It is an agricultural pest in the grain crops and gardens of India and Sri Lanka and is known for the piglike grunts it emits when attacked.
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, the wood rat, or pack ratpack rat,
rodent of the genus Neotoma, of North and Central America, noted for its habit of collecting bright, shiny objects and leaving other objects, such as nuts or pebbles, in their place; also called trade rat or wood rat.
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, the rice rat, the muskratmuskrat,
North American aquatic rodent. The common muskrats, species of the genus Ondatra, are sometimes called by their Native American name, musquash. They are found in marshes, quiet streams, and ponds through most of North America N of Mexico, but are absent from the
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, and the kangarookangaroo,
name for a variety of hopping marsupials, or pouched mammals, of the family Macropodidae, found in Australia, Tasmania, and New Guinea. The term is applied especially to the large kangaroos of the genus Macropus.
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 rat. House rats are classified in the phylum ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
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, subphylum Vertebrata, class Mammalia, order Rodentia, family Muridae.

See also mousemouse,
name applied to numerous species of small rodents, often having soft gray or brown fur, long hairless tails, and large ears. The chief distinction between these animals and the variety of rodents called rats is in size: mice are usually smaller.
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See H. Zinsser, Rats, Lice and History (1935); S. A. Barnett, The Rat, a Study in Behavior (1963).

The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/


(religion, spiritualism, and occult)

The Rat is one of the 12 animals of the Chinese zodiac. It refers to one of the 12 earthly branches, which are used in Chinese astrology, together with the 10 heavenly stems. Such a branch designates one day every 12 days: the days are named according to a sexagesimal (60) cycle, made of 10 series of 12 branches.

A Rat is jovial (perhaps too much), pleasant, and sociable; with a sense of justice, the Rat tends to want to convince others. On the negative side, he is suspicious, crafty, and may hold grudges if people are disrespectful to him. With a keen interest in everything, he is hardworking, ambitious, and conscientious. He loves money: he knows how to win it, and above all, he knows how to keep it, even if he is generous with those close to him. Easy to get along with, he is persuasive and a successful businessman. Not really faithful, he is nevertheless eager for tenderness.

—Michele Delemme

The Astrology Book, Second Edition © 2003 Visible Ink Press®. All rights reserved.

What does it mean when you dream about a rat?

Rats are often associated with the decaying conditions of poverty (“rat trap”) or illness. To betray someone is to “rat” on them. Dreams of rats can also indicate a need to take some time out from the “rat race.” (See also Mouse, Rodent).

The Dream Encyclopedia, Second Edition © 2009 Visible Ink Press®. All rights reserved.


(vertebrate zoology)
The name applied to over 650 species of mammals in several families of the order Rodentia; they differ from mice in being larger and in having teeth modified for gnawing.


McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


any of numerous long-tailed murine rodents, esp of the genus Rattus, that are similar to but larger than mice and are now distributed all over the world
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005


(1) (Radio Access Technology) See Multi RAT.

(2) (Remote Access Trojan) Software in a user's machine that is interactively controlled by an attacker. Having full administrator rights, the attacker can perform any operation in the computer remotely and direct the RAT in the infected machine just like a user with a Web browser requests data from a server. The Cult of the Dead hackers created the classic RAT (see Back Orifice). See Trojan.
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.


They are unpleasant and symbolize danger, poverty, filth, and illness. Your unconscious mind may be bringing up unpleasant images due to a disturbance in daily life. The dream’s purpose is to make you aware of negative feelings that may encourage you to directly deal with the negativity in your life. Dreaming about rats leaves the dreamer feeling apprehensive and disgusted. Attempt to connect these feelings with those things that produce this type of anxiety during the day.
Bedside Dream Dictionary by Silvana Amar Copyright © 2007 by Skyhorse Publishing, Inc.
References in periodicals archive ?
Forty male Long-Evans rats (70-100 g) were provided by the vivarium "Claude Bernard" from Benemerita Universidad Autonoma de Puebla.
Long-Evans rats were bred in our laboratory under controlled light and dark cycle (lights on from 0200 to 1600 hr) and temperature (22 [degrees] C [+ or -] 1 [degrees] C), with standard diet (chow 3430; Provimi Kliba AG, Kaiseraugst, Switzerland) and water ad libitum.
Subjects, Apparatus, Behavioral Procedures, and Statistical Procedures Four drug-naive male Long-Evans rats, approximately eight months of age at the start of the study, served as subjects.
In otherwise healthy Long-Evans rats, ozone exposure exclusively during implantation was not associated with significant differences in renal pathology or markers of systemic inflammation in the dams at the end of gestation.
Because healthy Long-Evans rats do not have any glucose tolerance problem, the interposed ileum might be adapted in the nearby healthy jejunum.
This hypothesis is being modeled in Long-Evans rats which have been audiogenically primed to have seizures.
Subjects were male Long-Evans rats, born to four dams who were shipped timed-pregnant (Charles River Laboratories, Raleigh, NC) at 13 days of gestation.
The present study examined the effects of blocking or enhancing GA[D.sub.65] or GABA-[A.sub.[micro]1 subunit expression on audiogenic seizure (AGS) activity in seizure-resistant and susceptible Long-Evans rats. Young adults subjects were presented for AGS activity 1 and 2 days prior to surgery (125 dB white noise stimulation for 120 s).
Short- and long-term biochemical effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin in female Long-Evans rats. Toxicol Lett 75:209-216.
LPS 08:B28), subject type (e.g., Sprague-Dawley rats, Wistar rats, Long-Evans rats, CF-1 mice, ICR mice bred for aggression), route of LPS administration (intraperitoneally or intravenously), subject age (35-day-old juvenile rats, or adult rats) and the sex of the subjects used in prior research.
OBJECTIVES: Our goal was to determine if a mixture of ATR metabolites, in proportions found in the environment, might produce developmental effects in Long-Evans rats following exposure late in pregnancy.