EXTERMINATION Service at Montreal, Boucherville, Longueil, Brossard & Laval 514-561-8933
Rats Extermination


Norway rats (or sewer rats) are the largest rodents (32 to 46 cm) living in a close relationship with humans. Their brownish-grey coat becomes paler on their underbelly and their tail is shorter than their body. The white rats used in laboratories are an albino variety. In the U.S., British Columbia, and some harbour cities in Eastern Canada, you can also find roof rats. The latter have a slimmer body, larger ears, and a tail that is longer than their body. Roof rats manage to cohabit with Norway rats because they often prefer higher structures and trees. In the wild, you can also find the much larger common muskrats (48 to 64 cm) associated with wet environments, as well as hairy-tailed moles and star-nosed moles that dig tunnels in the ground. These species are not part of the family of Muridae that includes rats and common mice.


Although Norway rats can shelter in tree cavities, walls or near sewers, they prefer to dig tunnels in the ground. They prepare a central chamber (45 cm below the surface) where they build a bowl-shaped nest of twigs, paper or fabric that helps insulate them and absorbs moisture. They also dig two or more emergency exits which they cover lightly with soil or camouflage under debris.

Mating takes place primarily in the spring and fall. Female rats can have three to 12 litters per year, each with an average of 7 to 8 young. They do not all survive, and the female only weans 12 to 56 per year. They are born hairless and with closed eyes. Female rats can mate again a day or two, or even hours, after the young are born. The offspring learn to prefer or avoid certain foods by the taste of their mother’s milk and by observing the female. They quickly become independent and reach maturity when they are about three months old.

Norway rats are active before sunrise and after sunset, but seem to be nocturnal only as a way of self protection; they can be seen during the day. To find nourishment, they can climb, jump (at least 0.9 meters vertically), swim, and chew on wood, asphalt, plastic, lead, aluminum or copper. They search for food and water in a 30 to 45 meter radius and rarely venture more than 100 meters from their burrows. They consume a daily average of 15 to 30 g of a variety of foods (vegetables, fruits, cheese, meat) but, when given the choice, they prefer grains. Rats often eat their fellow rats when their population level becomes too high. Their diet in the wild includes, among other things, insects, birds, fish, lambs and piglets, as well as excrement of other animals, through which they pick to remove undigested food particles. They look for a source of water and drink 29 to 59 ml every day – less if their food contains water – and they will get by with human urine if there is no other choice. Rats usually follow the same path and explore it to memorize each object along the way since they fear novelty. It appears that they are unable to distinguish colours.

Places where they can be found in the home

Rats do not actually nest in sewers, but use them as pathways to pick up food. Their presence in a house can be the result of inadequate or defective plumbing, a break in a sewer line caused by excavation or the roots of a tree invading a small opening.

There are a number of signs to alert us to the presence of rats such as their noise, teeth marks (3.5 to 4 mm wide) or entrance holes at least 5 cm in diameter. A greasy trail (caused by their dirty or oily coat) may also be visible at the base of walls, along the route they follow. Their urine phosphoresces when illuminated by ultraviolet light.

You can suspect an infestation when you find excrement (2 cm long and more or less rectangular) that is not recent, or when wood, electrical wires or other materials have been gnawed. You can spot rats during the night using a flashlight.

When there is a large number of rats, you can see fresh excrement and tracks (that would not be visible for a long time) left by their feet (2 to 4 cm) or tail (4 to 5 mm wide).

Rats consume and contaminate a variety of foodstuffs and damage the containers. They often live close by food left for animals, and can even live under doghouses and come out of their burrows when the animal is elsewhere. Holes (7.5 cm in diameter) leading to their tunnels can sometimes be seen outdoors, close to walls, doghouses or feed troughs, but the holes are often hidden by debris. Rats can also be found around dumps or attacking harvests and places where the harvests are stored.

Prevention methods

To prevent them from getting in, block all openings larger than 1.3 cm with materials such as mortar or galvanized sheet metal. But even if you prevent them from entering a building, their numbers will not decline if they can dig into the ground for shelter and have access to a source of food. Using sturdy containers to store food and practicing strict waste and trash management will reduce the amount of available food and shelter. It is best not to put trash outdoors too early. Above all, avoid making food available for them. You can also take steps to make sure they do not have access to pet food or easy access to a water supply – by repairing leaky faucets, for example.

If their food and shelter is not reduced, the population can rise again, even after some of the rats are killed off, because the females will then have more offspring per litter, therefore, more will survive.

Placing gravel around the outside of the house so that rats cannot dig their tunnels is also recommended. In addition, surrounding weeds and debris should be removed to minimize the number of potential shelters.