8 Interesting Facts About Rats | Britannica

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• Introduction
• Cubs, Bears, and Rats
• Monster Rats
• Rat Reproduction
• “You Dirty Rat”
• “You Dirty…Gerbil”?
• Are You a Rat?
• Something to Sink Your Teeth Into
• Rat Terminology

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8 Interesting Facts About Rats If you have musophobia, don’t read this. Ask Anything Homework Help Written by Amy Tikkanen Amy Tikkanen is Managing Editor at Encyclopaedia Britannica. Amy Tikkanen Fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Britannica AI Ask Anything Table of Contents Table of Contents Ask Anything

Those who suffer from musophobia might want to stop reading. This list is about rats! We’ve come up with eight facts that you might not know—or want to know—about the rodent everyone loves to hate.

Cubs, Bears, and Rats

New York City might have pizza rat, but Chicago tops the list of the most rat-infested U.S. cities, according to a 2016 list compiled by Orkin. The Big Apple was second, followed by Washington, D.C. (make your own politician-rat joke). Globally, London and Paris also have a well-documented problem with rats. In fact, the City of Light was forced to close several parks in 2016 due to a rat crisis.

Monster Rats

Think you’ve seen a really large rat? Probably not if you compare it with the Bosavi woolly rat, a species discovered in 2009. Believed to be the biggest rat, it is more than 32 inches (81 cm) long (including the tail) and weighs more than three pounds (1.36 kg). By comparison, the common house rat is about 20 inches (50 cm) long and weighs approximately 12 ounces (0.34 kg). Unfortunately, scientific studies have determined that common rats are getting larger. On the positive side, researchers think that common rats’ physiology prevents them from becoming gigantic rats. In New York City, for example, researchers determined that rats would likely never exceed 2 pounds (1 kg).

Rat Reproduction

Part of the rat problem is their incredible fecundity. Rats begin breeding as soon as five weeks of age and continue until about age two. Females are fertile approximately every three weeks, and during this time they have been known to mate up to 500 times (!) in six hours. The resulting pregnancy usually lasts about three weeks, and the litter size typically ranges from 6 to 20 babies.

“You Dirty Rat”

Although that is a misquote from the gangster film Taxi! (1931), rats have come to mean traitors or snitches. Why? Partly it’s due to their bad reputation as filthy and deadly creatures (see below) and also because rats will flee sinking ships and collapsing houses, giving the impression of abandonment.

“You Dirty…Gerbil”?

Rats are well-known carriers of diseases. They have been implicated in the spread of some 40 diseases, including the bubonic plague, typhus, and leptospirosis. For years it was believed that rats with plague-infested fleas caused the Black Death (1347–51), which killed an estimated 25 million people in Europe. However, scientists now think that another rodent was to blame for the Black Death: gerbils. After examining the weather during that time period, the researchers determined that the wet conditions would have caused gerbils to flourish, not rats.

Are You a Rat?

The answer is yes if you were born in 1924, 1936, 1948, 1960, 1972, 1984, 1996, or 2008. Those are the years of the rat according to the Chinese zodiac. People born under the rat are traditionally thought to be cunning, witty, and prosperous.

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Something to Sink Your Teeth Into

Rats are famous for being able to chew through things—soft concrete, wood, plastic, aluminum, and cinder blocks are no match for these rodents. Their love of chewing is due, in part, to the fact that their teeth never stop growing. In order to keep them from becoming too long, making eating impossible, rats must constantly gnaw to wear down their teeth.

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Rat Terminology

Some people have proposed that a group of rats be called “a mischief.” (Shouldn’t it be more menacing? A flock of crows is known as a murder, after all.) In addition, male rats are bucks, while females are called does.

Amy Tikkanen