--- title: "Eurasian Beaver (Castor fiber) | AnimalTracks.wiki" description: "Europe's orange-toothed dam builder, hunted to near extinction, then counted at over 1.5 million across Europe by 2012." image: "https://animaltracks.wiki/images/animals/eurasian-beaver-1.webp" published: "2026-09-01" updated: "2026-09-24" --- # Eurasian Beaver (*Castor fiber*) > **Status**: Checked against 8 sources, listed under Sources below. > **Tagline**: Europe's orange-toothed dam builder, hunted to near extinction, then counted at over 1.5 million across Europe by 2012. > **Soundtrack Vibe**: Art Punk & Experimental Post-Punk // Stereolab, "French Disko" > **Soundtrack Links**: [Spotify](https://open.spotify.com/track/4Zb88sF1Qj778KV5lstVxT) | [YouTube](https://www.youtube.com/watch?v=cdhVfr53Y2s) > **Vibe Match**: A relentless motorik beat and buzzing vintage synthesizers for a builder that works in series: two beavers released on a small stream draining farmed grassland built 13 dams. ## Biological Superpowers & Stats - **Taxonomy**: *Castor fiber* - **Danger Level**: Low - **Conservation Status**: Least Concern ([IUCN Red List](https://doi.org/10.2305/iucn.uk.2024-2.rlts.t4007a218566456.en)) - **Superpower**: Hard orange-enameled incisors, valved ears and nostrils that close underwater, and dams that flood former uplands and draw in new birds, fish, and amphibians. - **Habitat**: Freshwater rivers, streams, lakes, and ponds, usually in forested areas with willow, aspen, birch, and alder - **Diet**: Woody willow, aspen, and birch in winter; aquatic plants, shoots, leaves, and roots in summer - **Tags**: rodent, freshwater, woodland, herbivore, architect-builder ## Natural History & Behavior ## Second-Largest Rodent on the Planet The Eurasian beaver (*Castor fiber*) shares the title of the world's second-largest rodent with its North American cousin. An adult weighs 13 to 35 kilograms (29 to 77 pounds) and measures 73 to 135 centimeters (29 to 53 inches) long. Animal Diversity Web says it can live 10 to 17 years, though in the wild few live past 7 or 8. In winter it eats mostly woody plants, preferring willow, aspen, and birch; in summer it feeds heavily on aquatic plants, shoots, leaves, and roots. ## Built to Work Underwater A beaver's ears and nostrils have valves and its eyes have nictitating membranes, inner eyelids, closing when it goes under water. A fold of skin inside its mouth lets it gnaw on branches underwater without getting water in its mouth, and it can stay submerged for 4 to 5 minutes at a time. Its two large incisors carry hard, orange-colored enamel on the front surface. > **A Fitness Tracker for a Beaver** Researchers glued accelerometers, the same kind of motion sensor built into a fitness tracker, to the fur of 12 free-ranging Eurasian beavers in Norway. A computer model fed the motion data told seven behaviours apart, from swimming and grooming to sleeping, with 95% accuracy. ## Dams, Colonies and Scent Mounds Eurasian beavers were long thought to build smaller dams and lodges than North American beavers, but a 2015 study found that under the same conditions the two species build alike. Their dams alter a stream's flow and flood former uplands, and the new water draws in new species of birds, fish, and amphibians. They live in colonies of up to 12 with one dominant breeding pair, and mark their territory with castoreum, a pungent scent from glands near the tail, which they put on mounds of mud piled up on the shore. ## Hunted to the Edge, and Back Eurasian beavers once lived across Europe and Asia, but overhunting for fur and castoreum, along with habitat loss, left most countries there with none by the 19th century; Great Britain lost its last wild beavers about 400 years ago. In recent decades, reintroductions followed by natural spread have returned the species to much of its Eurasian range, and a review published in 2012 put Europe's population at over 1.5 million. In Spain, where new sites have been reported in recent years, a beaver was sighted in the Tagus river in June 2024 and its presence confirmed from signs on the banks: the first report of the species in that river basin, more than 100 kilometers from the nearest beaver area reported before. In England, the Eurasian beaver is a European protected species, and releasing beavers requires a licence. ## Frequently Asked Questions ### Is the Eurasian beaver really the world's second-largest rodent? Yes, jointly. The beaver family has only two living species, the Eurasian and the North American beaver, and a 2011 study of their mitochondrial genomes describes both as the second largest rodent. *(Source: [Horn et al. 2011]())* ### What is castoreum, and why do beavers build scent mounds? Castoreum is a pungent, sweet-smelling substance made in two glands near the base of a beaver's tail. To mark its territory, a beaver brings mud and plants up from the bottom, holds them against its chest with its forelegs and pushes itself up the bank with its hind legs until it has a mound, then puts castoreum on the pile. A beaver that finds an unfamiliar scent mound in its territory often reacts aggressively, hissing and slapping the water with its tail. *(Source: [Animal Diversity Web, University of Michigan]())* ### Can two beavers really change how a stream behaves? Yes. Researchers introduced two Eurasian beavers to a wooded site on a small stream draining intensively farmed grassland. Mainly by building 13 dams, the beavers raised the water stored at the site, with about 1,000 cubic meters held in their ponds, and likely damped storm flows: peak discharges fell by 30% on average. Water leaving the site carried lower concentrations of suspended sediment, nitrogen, and phosphate. *(Source: [Puttock et al. 2017]())* ### How close did Eurasian beavers come to vanishing for good? Very close. Populations fell nearly to extinction, and Animal Diversity Web estimates that by the 20th century about 1,300 Eurasian beavers were left in the wild. *(Source: [Animal Diversity Web, University of Michigan]())* ## Sources 1. [Castor fiber (Eurasian beaver). Animal Diversity Web, University of Michigan.]() 2. [Gazzard (2024). Castor fiber. The IUCN Red List of Threatened Species 2024: e.T4007A218566456.]() 3. [Brazier et al. (2020). Beaver: Nature's ecosystem engineers. WIREs Water.]() 4. [Puttock et al. (2017). Eurasian beaver activity increases water storage, attenuates flow and mitigates diffuse pollution from intensively-managed grasslands. Science of The Total Environment.]() 5. [Graf et al. (2015). The Use of Acceleration to Code for Animal Behaviours; A Case Study in Free-Ranging Eurasian Beavers Castor fiber. PLOS ONE.]() 6. [Horn et al. (2011). Mitochondrial Genomes Reveal Slow Rates of Molecular Evolution and the Timing of Speciation in Beavers (Castor), One of the Largest Rodent Species. PLoS ONE.]() 7. [Ansón & García-Prendes (2024). A beaver in the Tagus river: a new location in Spain. Galemys, Spanish Journal of Mammalogy.]() 8. [Approach to beaver management in England. Department for Environment, Food & Rural Affairs / Natural England.]() *Published September 1, 2026. 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