12 julio, 2024

Beaver: characteristics, habitat, reproduction, behavior

The beavers (Castor) are large semi-aquatic rodents with mainly nocturnal habits. Among its main characteristics are its incisor teeth, which are large. In addition, they are covered by an iron-based enamel. This gives them great hardness and a yellowish color.

Another outstanding aspect is its tail. This is flattened, oval-shaped and can measure between 20 and 30 centimeters. While swimming, it uses it to guide the movements it makes in the water. When on land, the tail is a support while it is sitting on its hind legs.

One of the ways to communicate is through olfactory signals. Thus, they usually deposit several mounds of odor around their territory. These are usually clumps of grass and sticks reaching about a meter wide and about 33 centimeters tall.

Members of the genus Castor are grouped into two species, the North American beaver (castor canadensis), endemic to North America, and the Eurasian beaver (castor fiber) that inhabits some regions of Eurasia.




The front limbs are small and strong. Each one has 5 semi-opposable fingers, allowing the beaver to handle various materials, such as rocks, mud, logs and branches, with great skill. With their digging claws they can open holes in the ground, to build their dams and burrows.

As for the hind limbs, they are larger than the front limbs and are hairless, except in the dorsal area. The fingers are united by an interdigital membrane, which contributes to swimming. One of the toes of these legs, the second towards the interior of the body, has a double nail.

This is used to groom itself, thus preventing its soft and fixed fur from becoming tangled and losing its insulating and waterproofing properties. In addition, thanks to the flexibility of the fingers, it can eliminate some parasites that are found in the fur.

On land, the beaver walks on its five toes. As for its movements, they are somewhat clumsy, making it vulnerable to attack by predators.

However, in the water, this mammal can swim at a speed of 10 km/h. In addition, thanks to the large size of its lungs, it can last submerged for 15 minutes.


The beaver has four incisor teeth, two in each jaw. The superior ones measure between 20 and 25 centimeters. These are covered on the front by an orange enamel, which contains iron.

Such coverage makes them much stronger than the teeth of other mammals. The back of the incisors is made up of soft dentin.

The ends of these teeth stay sharp due to a self-sharpening pattern. In addition, they grow continuously throughout their lives, thus preventing them from wearing down while gnawing at the wood.


Research has shown that the beaver continues to grow throughout its life. Thus, the average weight of an adult is approximately 16 kilograms, but some specimens could exceptionally reach 50 kilograms.

The American beaver is the largest rodent in North America. His weight is around 27 kilograms and his body measures from 60 to 100 centimeters. On the other hand, the Eurasian beaver has a body mass ranging from 13 to 35 kilograms and a length of 73 to 135 centimeters.


The tail is flattened and oval in shape. Its characteristics may vary individually or between one species and another. Thus, in the American beaver it can measure between 20 and 30 centimeters, while the Eurasian beaver has it shorter.

Unlike the rest of the body, which is covered in hair, the tail is leathery. The scales that cover it are juxtaposed, are black and have a hexagonal shape.

This structure is used in various situations. While swimming, the beaver uses it as a rudder, helping to orient and maneuver when moving. Also, it serves as a support to maintain balance, while the animal sits on its hind legs.

Likewise, when it is in danger, it strongly hits the water with its tail, with the intention of scaring away the predator. Also, it is a store of fat, which will be used during the winter as a source of energy.

Both the male and the female have two scent glands at the base of the tail. They secrete a substance called castoreum, very similar to musk, which is used to mark territory.


The beaver’s body is covered in dense fur. There are two types of hair: one soft and gray and the other rough and brown. In addition to being waterproof, the thick coat of fur acts as a coat.

As for the coloration, it can vary, depending on the species. Thus, the North American beaver has 50% of its hair pale brown, 25% reddish brown, 20% brown, and 6% black.

As for the European beaver, 66% have beige or pale brown fur, 20% reddish brown, 8% brown and 4% blackish.


The beaver’s eyes are adapted to see underwater. They have a thin, transparent membrane, known as the nictitant or third eyelid. This is located behind the eyelids and slides over the eye, transversely.

Regarding the ears, they are external, rounded and small. It has valves that close while the mammal is submerged. In the same way, the nostrils close when it is underwater.

Taxonomy and subspecies

-Animal Kingdom.

-Subkingdom: Bilateria.

-Filum: Chordate.

-Subphylum: Vertebrate.

-Superclass: Tetrapoda.

-Class: Mammal.

-Subclass: Theria.

-Infraclass: Eutheria.

-Order: Rodentia.

-Suborder: Castorimorpha.

-Family: Castoridae.

-Gender: Beaver.


-Castor canadensis.

-Castor fiber.

Habitat and distribution

The American beaver lives throughout North America, except for peninsular Florida, in the arctic tundra, in the deserts of Nevada and California, and in parts of Arizona and Utah. Its range is extended to the northern part of Mexico.

In 1946 it was introduced to Isla Grande, in Tierra del Fuego. Because of this, beavers are currently found in almost all streams in the Andes and in most aquatic habitats on various Chilean islands in the Tierra del Fuego archipelago.

As for the Eurasian beaver, it previously inhabited all of Asia and Europe. Currently, it lives in small populations in the Rhône (France), southern Norway, Elbe (Germany), the Dnieper basin (Belarus) and in Voronezh (Russia).

Today, thanks to several reintroductions of this species, it exists from Spain and France to European Russia. There are also Eurasian beavers in some parts of western Finland and in Scandinavia.

– Habitat

The beaver’s primary habitat is the riparian zone, including stream beds, ponds, and lakes. Some species may live in the intertidal area in river estuaries, where they build dams.

As its organism is adapted to a semi-aquatic life, it can live in a wide variety of freshwater bodies, such as rivers, wetlands and swamps. Generally, it prefers those that are surrounded by forests, although it can inhabit agricultural land, urban and suburban areas.

Those who live north of Scandinavia may inhabit the mountainous region where the only woody vegetation that exists are willows. In addition, for eight months of the year that area is frozen. Although it is not a habitat that it would prefer, it can survive in it.

In some ecosystems, the beaver can live both on the mountain plateau and in the lower part of the valley. In general, this mammal could inhabit almost any freshwater ecosystem, in which there are shrubs or trees and the water gradient is not very precipitous.

However, experts point out that this rodent shows a preference for waters that have a slow or calm flow.

Habitat modification

The beaver is one of the few animals that have the ability to modify the habitat where it lives. They can build dams, using branches and sticks woven from reeds, which they seal using mud. In this way, erosion of the stream is reduced by forming various slow moving ponds.

These bodies of water that were created are habitats for a wide variety of aquatic life. In addition, they provide water and food to other animals.

An example of environmental variations occurs in the natural ecosystem of the trees of the Nothofagaceae family, which abound in the forests of Patagonia. The action of the beaver causes the dense closed forest to become one dominated by sedges and grasses.

– Dams and home

The beaver can build various dams along the entire length of waterways. The intention is to flood a surrounding area to build a safe home. This requires a depth of 1200 meters, in order to avoid the freezing of the underwater entrances.

The length could vary, but is usually 4.5 meters long and between 1.5 and 2.4 meters deep. The beaver begins the construction by placing a base of thick sticks or rocks across the channel. Then, place branches and logs through it.

As they are placed, they weave them, leaving lower relief areas, so that the water can flow. When finished, he covers the cracks with mud, stones and mosses, making the dam more airtight.

In the event that the main dam does not create a pond with the depth required to make its home, the beaver could build other secondary dams, which stop the flow of water.


When the pond is the required depth, the beaver begins building its home. For this, create an island in the middle of the pond. Initially, it removes the bottom sediments, pushing the mud with its front legs in such a way as to form a column.

Then, on that mud, he builds his house, with branches and logs. The entire structure is covered with mud, except for the upper part that serves as ventilation.

Before the arrival of winter, the beaver collects a large number of fresh branches and places them under water, in a kind of pantry that is located next to the entrance of the shelter. The ends of the branches are pushed into the mud, in order to hold them in place.

In this way, you can access food during the winter, when the water pond is completely frozen.

Generally, the animal covers the floor with small pieces of wood, which help absorb moisture, in addition to serving as bedding for rest. This rodent will emerge from the home where it spent the winter when the ice has melted.

The ecological impact of the dam

The beaver is known as «nature’s engineer», since it builds dams to create a pond and there, make its burrow. By creating the dam, he modifies the regions where he inhabits.

This could represent a valuable resource for some species. However, it could also stop the natural development of the flora and fauna in the area.

Many of the regions where the beaver lives suffer from drought,…

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