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 highlight is its tail. This is flattened, oval-shaped and can measure between 20 and 30 centimeters. While swimming, he uses it to guide his movements in the water. When on the ground, the tail is a support while sitting on its hind legs.
One of the ways to communicate is through olfactory signals. Thus, they usually deposit in the surroundings of their territory several mounds of smell. These are usually clumps of grass and sticks that reach around a meter wide and approximately 13 inches 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.
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The front limbs are small and strong. Each one has 5 semi-opposable fingers, allowing the beaver to handle various materials with great skill, such as rocks, mud, logs and branches. With the 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 lack hairs, except in the dorsal area. The fingers are joined by an interdigital membrane, which contributes to swimming. One of the toes of these legs, the second towards the inside of the body, has a double nail.
This is used for grooming, thus preventing its soft and fixed coat from tangling and losing its insulating and waterproofing properties. In addition, thanks to the flexibility of the fingers, it can eliminate some parasites 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 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 on each jaw. The upper ones measure between 20 and 25 centimeters. These are covered on the front by an orange glaze, which contains iron.
This covering makes them much more resistant than the teeth of other mammals. The back of the incisors is made up of soft dentin.
The ends of these teeth are kept sharp due to a self-sharpening pattern. In addition, they grow continuously throughout life, thus preventing them from wearing out while gnawing on 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 60 to 100 centimeters. On the other hand, the Eurasian beaver has a body mass that ranges between 13 and 35 kilograms and they have a length of 73 to 135 centimeters.
The tail is flattened and oval in shape. Their characteristics can 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 with 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 in the orientation and maneuvering of the movements. Also, it serves as support to maintain balance, while the animal sits on its hind legs..
Likewise, when in danger, it strikes the water with its tail, with the intention of driving 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. These secrete a substance called castoreum, very similar to musk, which is used to mark the territory.
The beaver's body is covered in dense fur. There are two types of hair: one soft and gray in color and the other rough and brown. In addition to being waterproof, the thick layer of hair acts as a coat.
As for the coloration, it can vary, depending on the species. Thus, the North American beaver has 50% of the hair of a pale brown color, 25% reddish brown, 20% brown and 6% is black..
As for the European beaver, 66% have a beige or pale brown coat, 20% reddish brown, 8% have it 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, in a transverse direction.
In relation to 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 underwater..
-Animal Kingdom.
-Subkingdom: Bilateria.
-Phylum: Chordate.
-Subfilum: Vertebrate.
-Superclass: Tetrapoda.
-Class: Mammal.
-Subclass: Theria.
-Infraclass: Eutheria.
-Order: Rodentia.
-Suborder: Castorimorpha.
-Family: Castoridae.
-Genus: Beaver.
Species
-Castor canadensis.
-Castor fiber.
The American beaver lives throughout North America except peninsular Florida, the Arctic tundra, the deserts of Nevada and California, and parts of Arizona and Utah. Its range is extended to the north of Mexico.
In 1946 it was introduced in 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 of the Tierra del Fuego archipelago..
As for the Eurasian beaver, it previously inhabited all of Asia and Europe. At present, it lives in small towns in Rhone (France), southern Norway, Elba (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.
The beaver's main 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.
Because its body is adapted to 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 they can inhabit agricultural lands, urban and suburban areas.
Those who live north of Scandinavia can live in the mountainous region where the only woody vegetation that exists is the willows. In addition, for eight months of the year that area is frozen. Although it is not a habitat you might prefer, it can survive in this.
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.
The beaver is one of the few animals that has the ability to modify the habitat where it lives. It can build dams, using branches and sticks woven from reeds, which they seal using mud. In this way, stream erosion is reduced by forming several 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 the variations in the environment occurs in the natural ecosystem of the trees of the Nothofagaceae family, which are abundant in the forests of Patagonia. The action of the beaver turns the dense closed forest into one dominated by sedges and grasses.
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, to avoid freezing of the underwater entrances.
The length could vary, but it is usually 4.5 meters long and between 1.5 and 2.4 meters deep. The beaver begins construction by placing a base of thick poles or rocks across the channel. Then put branches and logs through it.
As they are laid, they weave them, leaving lower relief areas, so the water can flow through. When finished, it covers the cracks with mud, stones and moss, which makes 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 has the required depth, the beaver begins the construction of its home. For this, create an island in the middle of the pond. Initially, it removes sediment from the bottom, 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 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 the 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 keep them in place.
In this way, you can access food during 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 a bed for rest. This rodent emerge from the home where it wintered when the ice has melted.
The beaver is known as "the engineer of nature", since he builds dams to create a pond and there, build his burrow. When creating the dike, modify the regions where it lives.
This could represent a valuable resource for some species. However, it could also stop the natural development of flora and fauna in the area.
Many of the regions where the beaver lives suffer from drought, characterized by low rainfall. Thus, this climatic anomaly causes a lack of water resources necessary to supply the demand of the region..
According to research, beavers help prevent surface and groundwater from disappearing during this period.
When the beaver builds a dam, it also creates a pond where various aquatic ecosystems develop. These serve as a refuge for various species, thus benefiting the environment.
However, under the dam, this rodent creates a deep water storage mechanism. Around its burrow, the beaver digs furrows and dredges the bottom of the pond. The pit that originates, allows the water it contains not to evaporate during the dry season.
Studies show that rivers and streams where dams exist have high levels of clarity and very little pollution. Experts believe that this is a consequence of the slowdown suffered by the water as a result of the reservoir.
In an investigation carried out in Tierra del Fuego, where the beaver was introduced, it is evidenced that this mammal causes damage to the biomass and volume of the white oak (Nothofagus pumilio), due to the construction of the dams and the fact that it consumes it as food.
In this way, this rodent modifies the dynamics of the forest and gives rise to variations in the composition of the species that live there..
On the other hand, when the dam collapses and the constructed pond drains, it leaves behind a nutrient-rich substrate. This environment is conducive to the development of various species of animals and plants, thus forming the well-known "beaver meadow".
The populations of the two species that make up the Castor genus have decreased. However, due to the success of protectionist policies, currently the communities of the Castor fiber and from Castor canadensis they are stable.
Due to this, and their wide range of distribution, the IUCN has categorized both species within the group of least concern of going extinct. However, the Castor fiber is considered endangered on the Red List of China.
The Castor canadensis It does not have a significant threat in its entire habitat, since its hunting is regulated at the national level. In addition, successful reintroduction programs are being carried out in some protected areas..
However, in certain localities it could be captured illegally, to obtain and commercialize its skin. Also, some deaths may be due to the high degree of sensitivity of the American beaver to tularemia. This is a highly infectious disease that affects rodents and is caused by bacteria Francisella tularensis.
Regarding the Castor fiber, its historical decline was caused by excessive hunting, to obtain its meat, skin and the castoreum. Added to this was the loss and fragmentation of the wetlands where he lived.
Today, in a large part of its distribution areas, the populations of this species are expanding and there are no threats of a magnitude that could jeopardize its decline at the regional level..
However, in Mongolia, in some areas, such as the Tes River, illegal beaver hunting still persists. Another problem that the Eurasian beaver suffers is the loss of its habitat. In various regions, man selectively cut down the willow, a very important species for food and shelter for this mammal..
This situation occurs along the entire length of the Bulgan River and is causing the isolation of small populations of beavers..
In relation to China, the collection of firewood trees has deforested a large area of forests. In addition to this, grazing reduces vegetation even more, drastically modifying the natural environment where this rodent develops..
Various actions have contributed enormously to the recovery of Castor fiber in Europe. Some of these are hunting restrictions, reintroductions, and habitat protection..
Likewise, this species is protected under the protection of national and international legislation. For example, it is included in Appendix III of the Berne Convention and in the Habitats and Species Directive of the European Union.
The beaver reaches its sexual maturity when it is approximately two or three years old. In this species, the estrus is very short, lasting from 12 to 24 hours. Unlike the rest of the members of the order Rodentia, the beaver is a monogamous animal.
When they are a couple, they usually last together for several reproductive periods or for life. If one of the two dies, the other can look for a new partner. Within the rituals of courtship, the male and the female can perform some species of games or small fights.
As for copulation, it usually occurs underwater, on the river bank or in the pond where the couple lives. The gestation period can vary, depending on the species. Thus, in the female Eurasian beaver this stage lasts around 128 days, while in the American beaver it is between 105 and 107 days.
Before giving birth, the female is in charge of collecting soft and fresh leaves. With these it builds a kind of nest, in the highest part of the burrow. The litter can be made up of a group of 2 to 6 young, which are born covered in hair and with their eyes open..
The young weigh between 230 and 630 grams, being the Eurasian species larger and heavier than the American ones. Soon after they are born, they can swim, becoming skilled swimmers a week later. However, they practice diving when they are more developed.
During the first weeks of life they are suckled by the mother, however, the American beaver is weaned in the second week and the Eurasian in the sixth. During this time, the young remains in the burrow, together with the mother and young from the previous litter..
When the mother stops consuming breast milk, the mother offers her young leaves. During the upbringing, the father is an active part in it, although he also remains in the vicinity of the den, taking care of the territory.
When they are one month old, the young emerge from the burrow to explore the outdoors, but they are still dependent on their parents, who feed and protect them for at least a year..
When the young beaver reaches maturity, it leaves the family group permanently and goes in search of a companion. Later, it will build its own burrow.
The beaver is a herbivorous animal that eats soft branches, shoots, roots, and leaves of a variety of trees. Some of the preferred species are birch, aspen, birch, black cherry, alder, ash, red oak, and willow..
Occasionally, it might eat young fir and pine leaves. Also, consume a variety of aquatic plants, such as water lilies and cattails..
A large part of their diet is made up of the tree's cambium, a soft, woody layer underneath the mature bark. Therefore, to get to this, the beaver must chew on the tough outer bark of the tree. In this way, its self-sharpening incisor teeth keep their chisel-shaped tip..
When this rodent knocks down a tree, the first thing it consumes are the shoots and the cambium. After that, it cuts some branches and transports them to its burrow. While eating, it can perfectly manipulate the food with the five toes of its front paws.
As for the digestive system, it is adapted to process the vegetable fibers of the plants it consumes. Thus, the microorganisms that are in your intestine degrade the cellulose molecules, transforming them into smaller particles that will be absorbed by the body..
During the summer time, the beaver usually eats water lily tubers, aspen leaves and cambium, and some fruits, such as apples. Also, ingest the rhizomes of the coastal fern and some aquatic plants, such as water lilies..
Before winter arrives, the animal collects and stores various fresh branches under the water, in an area near the entrance of its home. The low temperature of the water maintains the freshness of the stems, as well as preserves its nutritional value..
When a beaver gets scared, it can quickly dive into the river, while pounding into the water, using its wide tail. The noise produced can be heard at great distances, both above and below the water.
Thus, this sign warns other beavers in the area of danger. Once the rodent triggers the alarm, those nearby will immediately dive, avoiding surfacing for some time.
The habits of this mammal are mainly nocturnal, spending most of the time eating and building dams and burrows..
The beaver has a very strong and stable social structure. Family groups are made up of a breeding pair, their young, and the young from the previous litter. Also, there may be one or two subadults, older than two years, that generally do not reproduce..
Family life is based on hierarchies, where the adults exercise dominance over the young and the young over the young. Within these, violent behaviors rarely occur. The beaver usually communicates mainly by gestures, postures and vocalizations. This is how they express both their hierarchy and their state of mind.
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