European beaver
The Eurasian beaver (Castor fiber) is a beaver species that was once widespread in Eurasia but was hunted to near-extinction for both its fur and castoreum. At the turn of the 20th century, only about 1,200 beavers survived in eight relict populations in Europe and Asia. It has been reintroduced to much of its former range and now occurs from Europe to a few regions in China and Mongolia.
The Eurasian beaver's fur color varies between regions. Light, chestnut rust is the dominant color in Belarus. In Russia's Sozh River basin, it is predominantly blackish brown, while in the Voronezh Nature Reserve, beavers are both brown and blackish-brown.
Eurasian beavers are distributed over a huge territory from north-eastern Europe to Central Eurasia, stretching southward from Norway on the Scandinavian Peninsula to Denmark, through Germany to the Alps, and then eastward, reaching as far as Mongolia. They inhabit freshwater systems such as rivers, streams, lakes, and ponds. They usually prefer forested areas, though can also be found in swamps and marshes.
Eurasian beavers are social animals, gathering in colonies. Beaver colonies have only one dominant breeding pair and can include up to 12 individuals. They construct burrows in the bank of a river or a pond. In the areas where the riverbank is unsuitable for habitation, they construct their lodges away from shore, using sticks and mud. They are mainly nocturnal, though can also be active by day. The Eurasian beavers are active all year round. However, in the northernmost areas of their range, the beavers rarely come above the ice surface during the winter. For this reason, during the autumn months, they store food supplies in the water to help them get through the winter. They are extremely territorial animals. The beavers use olfactory signals, marking their territory with castereum.
The Eurasian beaver is a herbivorous (folivorous and lignivorous) animal. During the winter, their diet mainly consists of woody vegetation such as aspen trees, birch trees, or willow. In the summer months, however, these rodents consume aquatic plants, bark, leaves, roots, buds, twigs, and shoots as well as crops in agricultural areas.
Eurasian beavers have monogamous mating system with only one breeding pair per colony. The breeding season takes place in January-February with the gestation period, lasting 60-128 days. The female usually gives birth to 1-3 babies, sometimes up to 6 and more. The mother takes care of the young, cleaning them and providing them with food. The babies are weaned at the age of 6 weeks, after which sub-adults in the colony help them with food, bringing them soft bark and small sticks, until the young reach the age of 3 months. Then, by the age of 1.5-2 years, they leave, sometimes being driven out by the adult female. The beavers start mating at 3 years old.
Pollution of rivers and streams, loss of habitat, as well as road accidents, are among major threats to the Eurasian beaver population. In Mongolia, the species is illegally hunted. On the other hand, in the northwest of Russia and in Finland, they are threatened by the competition with the introduced population of American beavers.
According to IUCN Red List, the total population size of the Eurasian beaver in 2006 was 639,000 individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List, and its numbers today are increasing.
Eurasian beavers play an important role in the ecosystem of their range. By building dams, they alter the water flow, thus flooding large areas of uplands and attracting new species of fish, amphibians, and birds. Then, in a year, the woody plants die off under the water, and a forested ecosystem gives way to an open water ecosystem. In addition, due to browsing woody vegetation, these animals help maintain woody plants in the sapling stages over long periods of time.