The Brown Rat-Rattus norvegicus

Rats belong to the Order Rodentia that comprises more than a third of all living species of mammal. The family Muridae is an extensive family and the name applies to rats and mice and the sub family Murinae. The brown rat is placed in the genus Rattus {formerly Mus}. It is known as the common rat or Norwegian rat hence the species name of norvegicus-meaning of Norway, and also the wharfe rat.

It was given the species name through a misconception that it arrived via ships from Norway in 1728/29. In fact there was no evidence of rats being in Norway at that point of time. it is thought that the brown rat arrived in Paris 1750 and America in 1775.

It is now generally accepted that the origin of the species to be northern China. However, and wherever this wily creature originated from in now inhabits all continents with few exceptions one of them being the Arctic and Antarctica . It basically lives where humans live.

Description of the Brown rat

The fur is a grey brown colour with a pale grey belly and a prominent scaly tail. The fur is rather course and shaggy  looking with long black hairs, that stick out and overlies the softer under fur. The ears are prominent, finely furred and of a pinkish colour.

The tail is thick and scaly and less than half the length of the body. The black rat Rattus rattus has a much longer tail. The body length of the brown rat  is up to 28 cm but varies. The males are usually larger than the females. They weigh 200-400 grams occasionally up to 800 gms.

The forepaws have digits that are capable of manipulating food, in this respect they are similar to the squirrel by eating food held in their forepaws. The sharp claws on each foot help the rat to be an excellent climber.

The teeth are naturally yellow coloured and include two prominent teeth in the upper jaw and two in the lower jaw { this arrangement is typical of all rodents.} These allow the rat to gnaw, not only food,but wood, lead pipes and even electric cables. These teeth continue to grow throughout the creatures life.

They have an acute sense of hearing and smell but their eyesight is generally poor.

Life and times of Rattus norvegicus

I have resided on this planet for over half a century and I can honestly state that I have never heard a good word said about this extremely common creature. It is associated with filth and disease and with some justification. As soon as rubbish {garbage} accumalutes the mammals move in, they will also be encountered in sewers, and in the wider countryside, especially in the vicinity of water bodies, such as canals,lakes,ponds, streams, brooks and ditches.

We as a race are generally untidy and wastefull throwing out or discarding food to accumulate , the rat does not require an invitation to dine! Even when we store food in a correct manner the rat will find away to doscover it, for example, in warehouses or grain stores.

Rats will horde food in large amounts for later use. They are one of the main enemies of the game keeper , being notorious for raiding the nests of game birds, and, in the wider countryside they will take the eggs of ground nesting birds. This is also true of water birds such as mallard coot and moorhen. Being excellent climbers they will seek out the nest of birds in shrubs and small trees.

Rats live in colonies which are dominated by large, high ranking males. Such males will claim the best places near food. Rats are capable of travelling up to 3-4km per night, which allows them as a species to spread at an alarming rate, colonising suitable locations at will.

Rats used to be regarded as serious agricultural pests especially in corn fields and grain stores. However, the advent of the combine harvester and more secure,hygienic buildings have greatly reduced the problem. Although mainly nocturnal in their activities, they are also regularly seen during day light hours.

Aggressive rats ?

Another reason many people dislike the rat is their defiant and aggressive nature. They are also violent towards their own kind, smaller , weaker members of the colony, or a rat straying into a colonised area will be readily bitten and driven off. because of such aggressive activity it is not uncommon to see rats with fur missing and wounds just above the base of the tail where it joins the body. Attacks on humans are relatively scarce. tales of them going for the throat are greatly exagerated and it is more likely that a rat that has been cornered is trying to jump over the shoulder to escape its predicament. The chances of beingbitten by a rat in ordinary circumstances is much less than the chances of being stung by a wasp.

Rats are highly intelligent creatures and will find and eat almost anything. Indeed it would be more difficult to name some thing they would not eat, if it is edible, it will be eaten including other animals, their young and eggs. rattus norvegicus is an accomplished swimmer capable of keeping afloat for many hours and capable of swimming to islands, where they can easily wipe out colonies of ground nesting birds. Because of this aquatic association they are sometimes mistaken for the much maligned water vole and visa versa. { click on the water vole content banner on the right hand side of this page to read about the consequences of this.}

Rattus norvegicus -breeding and young.

Any population that has found a dry warm place indoors will breed throughout the year. In the wider countryside they tend to breed until the frost and cold of winter arrives. The nest may be located under debris, but is usually in a burrow and made of grass, shredded paper or similar soft materials. each female is capable of having up to eight young per litter, the babies are born naked, blind and helpless. However, their eyes open within 6-8 days and they are weaned at three weeks old.

The young females are capableof breeding themselves at the age of 11 weeks and are quite capable of of having 5 litters per year. Thus by the end of the year the population has grown greatly at an alarming rate. However, nature redresses the balance for a large percentage fall victim to birds of prey, particualrly owls. Estimates reveal that only 10% of rats live for more than a yaer. Stoats weasels, cats and foxes all contribute in keeping numbers down.

However, the extermination of rats is still a serious business even in modern times, when new technology and improved pesticides are available to man. It seems the rat is still winning the battle. yet in the not to distance past it was a much  more serious issue. below are two reports which may put this into prespective. the first is taken from THE FIELD {London} Magazine Vol 100-- which states; " In 1901 an estate of 2,000 acres near Chichester was badly infected by rats. They were systematically destroyed by traps, poisons and even ferrets, under the supervision of the proprietor. In this way 31,981 were killed while it was estimated other methods killed a further 5,000 or more, and , even then the property was still not completely free of them".

A report from the Indian Famine Commission presented to the English Parliment in 1881 states;--- " An extraordinary  number of animals inhabit the southern deccan and Mahratta districts of India. The autumn crop of 1878 and the spring crop of 1879 wwere both below average, and a large portion of each was destroyed by rats. The resulting scarcity of food led the payment of rewards for thedestruction of the pests and over 12,000,000 were killed. "

Black rat -Rattus rattus

The black rat--

In archaic times the black rat Rattus rattus also known as the ship rat was our commonest species and it was this species that carried the flea that spread the great Plague. However, when the brown rat was introduced the black rat population fell year on yaer until the present day where it it classed as being very rare in the UK.

It is thought that the black rat had no resistance to diseases brought here by the brown rat. {This  situation also occured when the Grey squirrel brought with it the the squirrel pox virus that killed a great number of our native reds }


To mention the rat in a good light --as a species it has helpedhumanity in the form of an albino rat used in laboratories which helps to find cures for serious illnesses we suffer as a species. the laboratory rat originated through selective breeding over many years.

Other breeding selection has produced many  species that are considered to be pets by many people, and kept as such.

The brown rat is still very common and despite all the attempts of exremination is a very successful mammal. numbers are not as "plague" like as they once were but is of little consolation to me when I am told that wherever you are in the UK you are never more than ten yards from a rat.


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