Profile of the Rat

Rattus Norvegicus

Characteristics: Norway rats have brownish fur, a yellowish-white belly and a scaly tail.

Size: Adults generally weigh between 10 and 18 ounces and can reach lengths up to 18 inches, from nose to tail.

Lifespan: The typical Norway rat in the city lives about six months to a year.

Teeth: The term rodent means "gnawing animal." Rats must constantly grind their teeth because their front incisors grow five inches a year. The teeth are powerful, applying up to 24,000 pounds of pressure per square inch, allowing rats to chew through

wood, bone, lead pipes, brick, concrete, even thin pieces of metal.

Appetite: Rats can eat a third of their weight in food a day. Unlike other rodents, rats have a strong need for water -- 1/2 to 1 ounce a day.

Senses: Rats have poor eyesight beyond three or four feet, forcing them to rely on their highly-developed senses of smell, hearing and touch. They also have an acute sense of taste and are able to detect some contaminants in their food at levels as 

low as 0.5 parts per million.

Reproduction: Litters of six to 12 young are born 21 to 23 days after conception. Young rats are completely independent at about four weeks and reach reproductive maturity at three 
months of age. A typical female rat can produce a litter about six times a year.
Speed: Rats can run at 24 miles per hour for short bursts -- about as fast as an Olympic runner, even though they weigh less than 1/100 the weight.


Washington is run by Bureauc-RATs.

For an excellent article on rats from The Guardian of London, click here.



Rat Facts

  • The Plague: What we have come to call the Plague was brought on a merchant ship from Tana in the Crimea to Messina in Sicily in the year 1347. The ship contained black rats that were infected with the disease. The disease took many forms. The Bubonic Plague, carried by fleas on the rats, attacked the lymphatic gland system and caused swelling. Pneumonic Plague attacked the lungs and was more devastating. The plague, called the Black Death, went through Sicily to Italy and then throughout Europe and England. It had reached the entire continent by 1350. During these years, the population dropped by as much as 50%, in some locations much higher. The plague continued to exist into the fifteenth century and with less intensity in the sixteenth and seventeenth century. The plague still exists, and a few cases are reported in the U.S. every year, but it is generally treatable with antibiotics.

  • Arrival of the Brown Rat: Although the black rat has been around in England since the third century AD, the first recorded brown rat arrived in 1714, along with King George I, possibly even on the same ship! The first brown rats arrive in the U.S. in 1760.

  • Rats Can Survive Anything: Warfarin was developed as a rat poison a couple of decades ago, but within a year rats were seen eating it for food! After several atomic bomb tests on Engebi, in the Eniwetok Atoll in the 1950s scientists returned to the island to measure the bomb's effects. As well as highly radioactive soil and devastated plant-life they discovered a huge colony of perfectly healthy rats.

  • Reproduction: A single pair of rats can multiply more than 15,000 descendants in 1 year; 359 million in 3 years. Female rats spend almost 100 percent of their life pregnant. When females don't want to mate, they make a high-frequency squeal of 22 KHz that can help drive male rats away. The male rat has a rough-skinned penis surmounted by a "thorn" for penetrating power. Like people, and unlike most other animals, rats display homosexuality, even when members of the opposite sex are readily available.

  • The Power of Rat Teeth: The jaws of a rat can exert pressures of 24,000 lbs. Rats can readily chew through plastic water pipes, irrigation systems and garbage cans, wood boxes, dry wall, and even cinder block. Compare the hardness of rat teeth with that of common metals. On the international "hardness index" rat teeth = 5.5, while iron = 4.0, copper = 2.5-3.0, aluminum = 2.0 , and lead = 1.5. It was once believed that rats needed to gnaw to maintain their ever-growing incisors (front teeth) at the proper length, but this is not true. Rats fed on soft foods and kept in an environment without gnawing edges do just fine because the teeth wear on each other. Rat teeth grow 5 inches a year, however, and rats with mis-aligned jaws have been know to pierce their own brain cases with their own rapidly growing teeth.

  • Diseases: Rats transmit at least 35 diseases, including leptospirosis (very, very common) and the plague (very rare).

  • Population in U.S.: There are an estimated 235 million rats in the U.S.

  • Food: Rats eat 50 pounds of food a year and can eat 1/3 of their weight a day. Favorite foods include oatmeal, potatoes, meat and cooked eggs.

  • City Rats vs. Country Rats: Garbage-fed city rats are considerably larger than their rural cousins.

  • Rat Famine: Rats can survive for 14 days without food and will eat each other if there is no food. If all food is removed from a site where it was once plentiful (such as a silo), rats will generally starve rather than migrate.

  • Poison Detection: A rat's sense of taste is so strong, it can detect as little as two parts per million of poison in their food.

  • Swimming: Rats can swim 1/2 mile in open sea and tread water for 3 days. They can dive 100 feet underwater and hold their breath for as long as 15 minutes.

  • Warren Culture: Pack size can range from 15 to 220 individuals. One dominant male rat lives with a harem of several female rats. Social order is determined by fighting status, with the lower status kept the farthest from the food supply.

  • Rat Contamination of Food: A U.S. Government report states that each rat damages $1 to $10 worth of food and other material per year, and contaminates 5 to 10 times more. This means (conservatively) 200 million U.S. rats cause $1 billion to $20 billion in direct economic losses.

  • Rat Tolerance: U.S. Food and Drug Administration (FDA) guidelines allow "an average of two rodent hairs per one hundred grams of peanut butter."

  • Oldest Rat: The oldest rat on record lived to the ripe old age of 7 years and 4 months. The normal rat age span is 3 years.

  • Tyrannosaurus Rat: The first ancestor of the rat appeared 70 million years ago, when dinosaurs still roamed the Earth.

  • Leave it to the French: Hector the rat "piloted" one of France's first space rockets in 1961.

  • Lab Rats: One of the first strains of albino lab-rats was bred in Philadelphia, USA, by the Wistar Institute in 1906. Generations of white, hooded, brown and black lab rats have been bred since then, with a great deal of selectivity for slow speed and domesticability. The result: white lab rats act totally different from their wild urban and rural cousins. A white lab rat released into the wild is so slow, stupid and docile that it will probably not survive the week.

  • Imported Predator Control: In Malaysia, where barn owls were introduced to control plagues of rats, each barn owl family killed about 1,300 rats a year!

  • Largest Rat Ever Caught: Most large urban rats weigh under a 3/4 of pound. Despite the ubiquitous "it was larger than a cat" description of city rats, few rats weigh much more than a pound. The largest dog-caught rat ever weighed (by Brian Plummer) was a monster that tipped the scales at 2.4 pounds.


  • Getting Rid of Rats: It is is almost impossible to rid an area of rats by poison and traps alone. Some rats are simply too smart to be caught by traps, and rats grow resistant to poisons rather quickly. Poison and traps can work, but ONLY if they are combined with clean up of garbage-ridden areas. Start by putting all trash into cans with tight-fitting lids, removing large overflowing dumpsters, trimming grass and weeds in the area, plowing up burrows, and removing all possible hiding places. Bird feeders should be removed, dogs cleaned up after, sources of water drained, and wood piles raised off the ground.

  • Ratio of Rats to Human Population in Most Cities: One to one.

  • Rats as Food: Rats are eaten as food in very rural parts of many Asian countries (the Philippines, Thailand, India), but in Vietnam local government officials have actually encouraged the practice because local villagers have eaten all the cats, creating a pandemic of rats and mice that, in turn, have been destroying food crops. Imagine the bumper stickers for such a campaign: "Eat a Rat & Save a Cat!"

  • Praying To Rats: In India, some Hindu people pray to rats at the Rajasthan rat temple. The penalty for stepping on a rat and killing it; an offering of a life-sized rat made in gold.