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Related to Norway rat: roof rat, brown rat, sewer rat


rat, name applied to various stout-bodied rodents, 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 rat, the wood rat, or pack rat, the rice rat, the muskrat, and the kangaroo rat. House rats are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Rodentia, family Muridae.

See also mouse.


See H. Zinsser, Rats, Lice and History (1935); S. A. Barnett, The Rat, a Study in Behavior (1963).

The Columbia Electronic Encyclopedia™ Copyright © 2022, Columbia University Press. Licensed from Columbia University Press. All rights reserved.


(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 ?
In this sense, the Norway rat is the most abundant mammal in cities, with a lifespan of around 1-3 years.
Our paper outlines the Norway rat eradication from a small island (Isola delle Femmine, Southern Italy) in the Mediterranean basin from the project outline to the main eradication campaign in 2008-2009, follow-up and post-hoc monitoring.
Characteristics of the built environment and the presence of the Norway rat in New York City: Results from a neighborhood rat surveillance program, 2008-2010.
The patient owned and operated an in-home rattery, or rat-breeding facility, with approximately 100 Norway rats, primarily bred as pets.
Reproductive activity revealed that the males were recorded reproductively active throughout the year while more than 50% specimens of females were recorded inactive throughout the year; yet lactating and pregnant females, and scars in the oviduct were recorded throughout the year indicating that Norway rat reproduces the year around in the urban environment of Rawalpindi, Pakistan.
We have also identified 4 nucleotide differences as compared to the hdac6 sequence in the Norway rat (XM_228753.8) available at NCBI.
Effect of glutathione depletion on Leydig cell steroidogenesis in young and old brown Norway rats. Endocrinology.
Further, while their skills in horticulture enabled the Mandan to develop vast stores of corn, tobacco, beans, and pumpkins for trade and personal consumption, the introduction of the Norway rat up the Missouri River, around 1825, consumed vast amounts of corn in their underground storage caches.
"I have seen an increase in rattus norvegicus, know as the Norway rat or brown rat.
To help homeowners identify infestations, the team at Family Pest Control is explaining the clear differences between the two most common rat breeds - the Norway rat and the roof rat.
Similarly, the role of Norway rat (Rattus norvegicus) as vector of C.