In The Wild
The Eurasian beaver (Castor fiber) is Europe's largest rodent and the second largest rodent in the world. A vegetarian, it spends all of its time in or very near water. They have a broad torso and widely spaced, short legs which are perfect for building dams. They also have large, well-developed incisors which are great for at gnawing the wood required to build their dams. Their front paws are small and have well-defined claws, while their back feet are webbed for swimming.
They have also developed several other adaptations including a broad tail, which is covered in scaly black skin made from modified hair. It’s similar to a paddle blade and is used as a rudder while swimming. They have thick course guard hairs which help to provide protection against the cold, and can be waterproofed. The waterproofing oil is produced in glands and is spread through their coat as it grooms its fur. They are also able to close their nose and ears when underwater and a transparent membrane protects the eye when it is swimming. Additionally, there are inner lips directly behind the teeth which allow the beaver to use its teeth underwater without flooding its mouth with water.
Dam construction and lodge-building are probably the most familiar aspects of beaver behaviour. They often dam rivers in order to regulate water levels - this ensures that the entrance to their home or "lodge" is always safely under water away from predators such as wolves or bears.
The dam is built from branches, which the beaver gets by using its chisel-like teeth to chip away at a tree trunk until it falls. The beaver then cuts the tree up and drags or pushes the timber into place.
The beaver is a largely nocturnal animal and most of their construction behaviour and foraging is undertaken during the night. They feed on bark, twigs, roots and leaves as well as aquatic plants. Prior to winter, beavers will store sticks and logs in underwater piles. This store of food will help to sustain the beaver through the winter months.
European beavers mate for life and typically live in a small family group with the young from the past two years. They normally have one litter per year, with litter sizes ranging from one to nine kits. The female looks after them for around three months and they may stay with the adults for up to two years before leaving the family group when sexually mature.
During the late 19th and early 20th centuries beaver populations were wiped out in many parts of Europe as a result a loss of suitable wetland habitat and overhunting for their thick fur, meat and castoreum, which is a substance they secrete from their scent glands. Castoreum was used as the base for perfumes and also as the forerunner to aspirin. In recent years, a combination of conservation measures and reintroduction programmes have resulted in the beaver returning to much of its former range, and a number of its populations are rapidly expanding.