Castor fiber Linnaeus, 1758

Taxonomy and Common Name

Castor fiber Linnaeus, 1758, commonly known as the Eurasian beaver, shows regional variation in fur colour.

Regional Fur Colour Variation

Light chestnut-rust is the dominant fur colour in Belarus; in Russia's Sozh River basin, fur is predominantly blackish brown, while beavers in the Voronezh Nature Reserve have both brown and blackish-brown fur.

Size Classification

The Eurasian beaver is one of the largest living rodent species, and the largest rodent native to Eurasia.

Body and Tail Length

Its head-to-body length measures 80–100 cm (31–39 in), with an additional tail length of 25–50 cm (9.8–19.7 in).

Typical Weight Range

It typically weighs between 11–30 kg (24–66 lb).

Weight Relative to Other Rodents

Based on recorded average weights, it is the world's second heaviest rodent after the capybara, and is slightly larger and heavier than the North American beaver.

Exceptional Weight Records

One exceptionally large recorded specimen weighed 31.7 kg (70 lb), and there are reports that the species can exceptionally exceed 40 kg (88 lb).

Historical Population Decline Causes

The Eurasian beaver is currently recovering from near-extinction, after being heavily hunted by humans for its fur and for castoreum, a scent gland secretion believed to have medicinal properties.

Early 20th Century Population Status

By the early 20th century, the estimated total population was only 1,200 individuals, and the species became extinct across many European nations.

2020 Population Status

However, reintroduction and protection programs have led to gradual population recovery, so that by 2020, the total population numbered at least 1.5 million.

Historical Survival Location

The species likely survived east of the Ural Mountains from a 19th-century population that was as small as 300 animals.

Recovery Enabling Factors

Factors that have enabled its recovery include the ability to maintain sufficient genetic diversity even when recovering from a population as small as three individuals, plus the fact that beavers are monogamous and select mates that are genetically different from themselves.

Current Population Distribution

Around 83% of the global Eurasian beaver population lives in the former Soviet Union as a result of reintroduction efforts.

Keystone Species Role

The Eurasian beaver is a keystone species that supports the ecosystems it inhabits.

Wetland Creation Benefits

It creates wetlands that provide habitat for the European water vole, Eurasian otter, and Eurasian water shrew.

Waterside Vegetation Modification Benefits

By coppicing waterside trees and shrubs, it facilitates their regrowth into dense shrubs, which provide cover for birds and other animals.

Dam Ecosystem Benefits

Beaver dams trap sediment, improve water quality, recharge groundwater tables, and increase cover and forage available for trout and salmon.

Bat Population Benefits

The abundance and diversity of vespertilionid bats also increases in areas with beavers, apparently because beavers create gaps in forests that make it easier for bats to navigate.

Annual Litter Frequency

Eurasian beavers produce one litter per year.

Female Oestrus Timing

Females enter oestrus for only 12 to 24 hours, between late December and May, with oestrus peaking in January.

Mating System

Unlike most other rodents, beaver pairs are monogamous, staying together for multiple breeding seasons.

Gestation and Litter Size

The average gestation period is 107 days, and litters average three kits, with a range of two to six kits per litter.

Reproductive Maturity Age

Most beavers do not reproduce until they reach three years of age, but around 20% of two-year-old females are able to reproduce.