Beavers: Rodents that build dams and fortresses

Beavers are known for having the ability to nibble tree trunks. These animals have huge teeth and can gnaw on a tree trunk for a longer period of time. With these tree trunks they build dams and so-called 'fortresses'. With this they create an ideal living environment. The dams that they build can have enormous dimensions and therefore close off a large part of the river. If the consequences are too great, this can sometimes cause inconvenience.


Physical characteristics & other characteristics

The beaver belongs to the 'Castoridae' family. They are mammals that can be found in Scandinavia, Eastern Europe and Russia, among others. In addition, the mammals also occur in the Netherlands and Belgium thanks to re-introduction of the animal species. The beaver that occurs here is also called the "Eurasian beaver". Beavers can also be found in North America (the North American beaver).


Beavers have gigantic teeth compared to other rodents. The beaver's teeth are large and strong enough to nibble a tree trunk in such a way that the relevant tree falls over. Any damage to his teeth is canceled out due to constant growth of his teeth. In addition, these mammals have a striking thick tail that they use as a rudder.

Why do these mammals gnaw on tree trunks?

The rodents bite tree trunks until they fall over. The beavers make a dam with the stems and branches to stop the water. In addition, they have the capacity to build a particular structure in which they reside. This is also called a 'castle'. A castle is multifunctional and is usually very spacious.

Building a castle

Beavers are monogamous and stay together all their lives. A castle ensures safe accommodation and can also be comfortable. The structure is usually occupied by one or more family members. If there is a shortage of space, a new castle will be added. The structures can sometimes reach a height of 2 meters and can be around 10 meters wide. Beavers only build a castle when there is no room for an underground cave. Making a hole is easier. A castle is more complex and usually contains 'rooms' with specific properties.

The nest room

This space is about 20 centimeters above the water. This ensures that this space remains dry. It contains a hole so that fresh air can enter the room. Wood chips that serve as a floor can be found in the nest room.

"Wet Room"

The 'wet room' is the place where the animals dry themselves by shaking their bodies. The mammals can then move to the nesting room.


On shore there is sometimes an 'army' along the bank. This is an inconspicuous pit (usually shallow) that beavers have laid out for resting. Just like the nest room, this pit contains all kinds of wood chips. An army can offer protection against possible predators and rainfall because it is protected with all kinds of vegetation.


Beavers are known for being able to build dams by gnawing trees. Beavers can gnaw trunks with their teeth that have a thickness of about one meter. With the help of these dams, the enormous rodents ensure that the water on the other side is lower. Some dams are hundreds of meters long and ensure that the water remains artificially controlled. This ensures that the castle that they have built does not run underwater.

The winter

The function of a dam disappears the moment the ditches and rivers begin to freeze shut in the winter. During this period they make a hole in the dam so that the water under the ice can drain away. This gives the beavers the space to walk and breathe.

Nuisance caused by beavers

A large beaver population can cause inconvenience because they cause many changes in their environment. Numerous trees are being gnawed at it. This has consequences for the water level and the accessibility of the area. For example, paths that are located within nature reserves can become unstable. In addition, farmers can suffer from a too high water level that causes the crops to drown.

Video: Beaver Lodge Construction Squad. Attenborough. BBC Earth (February 2020).

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