Le 12 March 2020

The rat acts either as a reservoir for the microbe (bacteria, virus or parasite) which it harbors without transforming it. Or as an intermediate host in the parasite's cycle (which will transform in the rat's organism and become infectious there for humans).

It is then infectious either by its bite, or by its droppings, or by its blood drawn and transmitted to humans via a vector (insect, tick).

Le rat brun ou rat d'égout

Brown rat or rat, mango rat or Norway rat

Physical characteristics

The adult rat has a size between 20 and 28cm without counting the tail. Its tail is 17 to 23 cm long. Adult, its body mass varies according to sex between 200 gr to more than 650 gr.

His life expectancy is around 18 months


The brown rat is an omnivorous opportunist. It feeds on everything it manages to steal unlike other animals. A rat eats and drinks the equivalent of 10% of its weight daily. The food preferences of the brown rat are close to that of the cat, since it prefers meat to fruits and cereals, although depending on the circumstances it may consume only cereals.

The brown rat is extremely careful when discovering any new food. He can sometimes wait several days before tasting a food he does not recognize, he can then consume only a small amount to assess the effects of this unknown food.

Rat brun


Her sexual maturity occurs between 50 and 60 days after birth. The rat only reaches sexual maturity at 5 to 6 weeks of age in both sexes. The reproduction of the rat stops between 12 and 18 months.

The brown rat is an extremely prolific animal. Indeed, a single female can give birth to around sixty pups per year. At this rate, a female could theoretically have 1000 offspring in a year and 2500 in her whole life, but a young female can, in principle, give only a maximum of 10 young during her first litter.

The female can be fertilized again a few hours after giving birth. The spleen gives birth on average from 6 to 12 pups per litter and can have 4 to 7 litters per year.

The gestation period in rats is 20 to 22 days.


Wild rats can transmit, like other animals, many diseases in humans: plague, salmonellosis, leptospirosis, typhus, fevers, rabies, trichinosis.

It carries diseases and bacteria that represent a real risk to the health of humans and other animals.

Behavior and social life

The rat has an omnivorous twilight or even nocturnal activity. Indeed, in addition to animal and vegetable matter, it eats away everything in its path: paper, wood, pipes, electric cables. Certain metals (copper, tin, lead) do not resist the teeth of rats.

The social life of the brown rat is very hierarchical unlike other species like the black rat.

Groups consist of at least 20 members and can reach up to 200 members, but they generally consist of 40 to 60 animals The unity of a group is based on smell, a family smell excludes any individual who don't have it.

Rats therefore understand each other mainly thanks to ultrasounds that are inaudible to humans. Thus a rat can warn the others of surrounding dangers or of its personal state.

Sensory perceptions

Smell is the predominant sense. It is by their smell that the rat recognizes its congeners, that it recognizes its territory and that it can find a path if it has marked it with its urine. Smell is also essential for foraging.

The Norway rat has a very developed taste and does not hesitate to sort its food to find the foods that it likes. He can sometimes be suspicious of a different food than the one he knows and he records tastes (which allows him to know if a known food has been modified).

Hearing also plays an important social role.