The brown rat

Latin: Rattus norvegicus.

Brown rat eating

Brown rat eating

The brown rat is found all over the world. It originated in East Asia, from where it has spread, partly on foot and partly by sea on ships. It arrived relatively late into Europe. We first hear about “wandering rats” ravaging the continent in the early 1700s. The brown rat has great adaptability and it quickly drove away the black rat, which until then was the most common species in houses.

An adult brown rat is about 45 cm long. Of these, 20 cm is tail. The weight is usually 200 – 250 g. The colour varies somewhat, but the upper surface is usually dark brown or noble. The underside varies from whitish to grey. The brown rats thrive on the most diverse locations, but are primarily found in stables, warehouses and homes. In towns and cities, they often live in waste water pipes. Rat invasions in urban property are almost always due to sewer rats that come up through a break in a pipe. The rat is practically omnivorous. It prefers cereal products, but it also eats meat and may occasionally arise as a predator that eats chickens and other small animals. An adult rat eats an amount of feed that corresponds to 1/10 of its own body weight a day. Some of the places in the world where people have little access to food, the rats eat more than half of the stored food. In our latitudes rats’ main demerits are the gnawing of packaging and products, as well as contamination of food. There is no doubt that rats (and mice) are responsible for a large part of the food poisoning caused by Salmonella bacteria.

The brown rat breed all year round. One pair of rats that are doing well in a granary or stable can in the course of a year produce 800 rats. Rats live in herds and they recognise each other by smell. The rats are shy animals that are primarily active during the dark hours. They are suspicious of new objects and do not cross open areas, but move along walls.

Brown rat

( Latin: Rattus norvegicus)

The brown rat, now found in almost all parts of the world, is believed to have originated in eastern Asia. It spread partly on foot, partly by ship. It came to Europe relatively late, probably about the beginning of the 18th century, but when it did it spread very rapidly, for this large rodent has a great ability to adapt and it soon drove out the black rat.

The brown rat thrives in all sorts of places, but it is primarily associated with buildings, warehouses and farm buildings, where it prefers the damp parts.

In towns it often frequents drainpipes, feeding on the kitchen waste that passes by, and builds its nest of paper, wadding or similar materials wherever it can find a dry place.

When brown rats invade urban property they will nearly always have come up through a break in the sewers. Brown rats are omnivorous, and will eat any animal or plant food, and they may even become predatory, taking live chickens and ducklings. In many places in the world it has been reckoned that the rats eat more than half the available foods. The position is not as serious as this in temperate regions but losses can be quite substantial. As in the case of mice most of the damage is due to the rats gnawing through packaging and fouling with urine and faeces. In fact, rat urine and faeces often contain disease germs, which may present a risk to the health of man and his domestic animals.

Under favourable conditions, in grain warehouses and outhouses, brown rats will breed throughout the year and they are extraordinarily prolific. A pair of rats and their offspring can produce about a thousand individual in the course of a year.

Brown rats live in groups, the individuals within each group recognising each other by smell. They are shy animals which are mainly active during the hours of darkness. They never willingly move out on to an open area, but will always go along the walls.