In-Depth Guide on Brown Rats


Brown rats love to be around people because this way they are guaranteed of food and shelter whenever they need it. These mice can feed on almost anything, including garbage, amphibians, snails, smaller rodents, small birds, worms, eggs, meat, insects, beets, grains as well as seeds. They are nocturnal and they can be hunted by owls as well as other predators such as the domestic cat. They are also pursued by people very fiercely. The brown rats are very small and very hard to capture with just a trap.


Brown rats are considered the greatest mammalian pests ever. The brown rat is omnivorous by nature and can eat a wide range of foods that include seeds, fruit, seeds, cereals, meat, eggs, insects, small mammals, frogs as well as other kinds of invertebrates. These rates can also catch fish and eat it.

Brown rats are also nocturnal in nature. However, they can be active during the day if humans disturb them. They can move around on the ground, but they are also excellent swimmers, climbers and jumpers. They hold their tails so as to keep balance as they swim.

Brown rats can be found in packs that have a dominant male that gains great priority when it comes to resting sites, good and water access. This male defends the females and prevents other males that are subordinate from mating.


The females reach sexual maturity at only 8-12 weeks. The gestation period, usually starts from 12-23 days. Females can conceive even as they suckle another litter after 18 hours just after mating.

Brown mice can breed all through the year; the weather plays a great role in this. The brown rat also breeds faster depending on the availability of food. A brown rat can have around 13 litters every year and every litter can have around 7-9 young ones.

Their longevity is around three years, but in the wild, this is greatly reduced to eighteen months. Mortality is usually because of poisoning by use of rodenticides and hunting by cats and other predators


The   brown rat is also known as the Norway rat and it is a generalist and a very opportunistic rat at that. It is a prolific breeder and is agile in nature. The fur color of the rat varies a great deal. Generally, it should be grayish brown or brown with black hairs. The underside is paler. They have a long tail that is long and hairless to a great extent. They also have prominent naked ears and the eyes are smaller.

Range description

This is a species that is native to south east Siberia and north-east china as well as some parts of japan. However, this is a rat that is found in all parts of the world as introduced species.  Originally, the brown rat is native to China, but there has been other introduction in all parts of the world. This was through shipments. They now occur all over the world with an exception of the Antarctica, which is too cold for the rat.

The most interesting thing about the brown rats is their abundance within the urban and suburban settings. These are rats that thrive where humans are and therefore urban areas are the perfect home for them.

Physical description

The brown rat is a large member of mousse family. The rats are around 400mm when measured from the tip of the nose to the tip of the tail. Their weight is about 140-500 g. Usually, the males are much larger than the females. In the natural populations, the rats come covered with the coarse fur that is brownish in color. Sometimes, it can be splotched with some white or black hairs within the dorsal surface and it lightens to gray or even tan as you get to the underside. There are some strains that are bred while in captivity and they can have white, black or brown color.

The tails and the ears of these rodents are usually bald. The tail length is much shorter in comparison to the body length. They have lophodont molars and their dental formula is usually 1/1-0/0-0/0-3/3. When you look at the brown rat ears, they are much shorter compared to those of the related species. They don’t cover eyes if they were to be pulled down. It is very easy to confuse the brown rat with the black rats even though their temporal ridges are actually straight. Those of the black rat are usually curved.

Ecology and habitat

The species are present within the coastal and lowland regions in all the areas where you find humans. In colder areas, the brown rat is very common. When the area is tropical and warmer, the brown rats are usually restricted to the habitats that humans have modified and these include places such as ports, buildings, sewers and so on.


Brown rats can be found in bushy and forested areas. Today, they have a new preferred habitat alongside the humans as their population expands rapidly. Almost all the cities in the world have got a very substantial number of rodents to deal with. These rodents occupy all kinds of habitats and they include basements, woodlands, open fields, sewers, garbage dumps and so on. Regardless of where the human population is, there will be he brown rats around.

They can be found in the terrestrial, the tropics as well as the temperate areas. They can be found in the subtropical areas such as the rocky shores in the coastal areas and so on. They can also be found in the forested areas, settlements and forest areas that are highly disturbed.

Brown rats can also be found within burrows that are very close to the human habitation


The brown rats are highly non-migrant in their nature. They do not make any seasonal migrations that are significant. There are juvenile dispersals but these cannot be considered as being migration at all. The only places they move to is to get to the winter grounds, the breeding grounds as well as the hibernation sites. They do not move for more than 200 km at a time.

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