---
title: "What the sources say about the Eurasian Beaver | AnimalTracks.wiki"
description: "51 claims from the Eurasian Beaver profile, each beside the words of the source that backs it."
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---

# What the sources say about the Eurasian Beaver (*Castor fiber*)

> 51 claims from the Eurasian Beaver profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Eurasian Beaver](https://animaltracks.wiki/animals/eurasian-beaver/)

## Castor fiber (Eurasian beaver). Animal Diversity Web, University of Michigan.

https://animaldiversity.org/accounts/Castor_fiber/

| The page says | The source says |
| :--- | :--- |
| An adult weighs 13 to 35 kilograms (29 to 77 pounds) and measures 73 to 135 centimeters (29 to 53 inches) long | Eurasian beavers weigh from 13 to 35 kg and are 73 to 135 cm in length. (note: 13-35 kg converts to 28.63-77.09 lb and 73-135 cm to 28.74-53.15 in, rounded) |
| Animal Diversity Web says it can live 10 to 17 years, though in the wild few live past 7 or 8 | Eurasian beavers can live 10 to 17 years of age but rarely live longer than 7 to 8 years in the wild. (note: lifespan rests on ADW alone, so it is credited to ADW) |
| In winter it eats mostly woody plants, preferring willow, aspen, and birch; in summer it feeds heavily on aquatic plants, shoots, leaves, and roots | Eurasian beavers are herbivores, feeding primarily on woody vegetation in the winter months. Eurasian beavers prefer willow, aspen, and birch trees ... During summer months beavers feed heavily on aquatic vegetation, shoots, twigs, bark, leaves, buds, and roots. |
| A beaver's ears and nostrils have valves and its eyes have nictitating membranes, inner eyelids, closing when it goes under water | Both ears and nostrils are valvular and the eyes have nictitating membranes, closing when they go under water. (note: 'inner eyelids' glosses nictitating membrane for the audience) |
| A fold of skin inside its mouth lets it gnaw on branches underwater without getting water in its mouth | Inside the mouth, beavers have a skin fold that allows them to gnaw on branches under water without getting water in their mouths. |
| it can stay submerged for 4 to 5 minutes at a time | Beavers are semi-aquatic and can stay under water for 4 to 5 minutes at a time. |
| Its two large incisors carry hard, orange-colored enamel on the front surface | They have two, large incisor teeth with hard, orange-colored enamel on the anterior surface. |
| Their dams alter a stream's flow and flood former uplands, and the new water draws in new species of birds, fish, and amphibians | Through the process of building dams they alter the flow of the water and flood many acres of former uplands. ... This new water source attracts new species of birds, fish, and amphibians by providing a suitable water table. |
| They live in colonies of up to 12 with one dominant breeding pair | In the lodges, beavers live in colonies of up to 12. These colonies consist of only one dominant, monogamous breeding pair. |
| mark their territory with castoreum, a pungent scent from glands near the tail | Eurasian beavers have two castoreum glands located next to the cloacal opening. These glands produce a pungent, sweet smelling chemical called castoreum and is used to mark territories. (note: 'near the tail' simplifies 'next to the cloacal opening' for the audience) |
| which they put on mounds of mud piled up on the shore | They do this by building a scent mound on the shore. They bring mud and vegetation up from the bottom, holding it tight to their chest with their forelegs and pushing themselves up the bank with their hind legs until they have a mound. The beaver will then apply castoreum to the mud pile creating a scent mound. |
| 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 | Eurasian beavers, Castor fiber, once heavily populated all of Europe and Asia. However due to overhunting for fur and castoreum, a chemical from their castor sacs, and habitat loss, populations fell nearly to extinction. By the 19th century most countries in Europe and Asia had no remaining beavers. |
| Castoreum is a pungent, sweet-smelling substance made in two glands near the base of a beaver's tail | Eurasian beavers have two castoreum glands located next to the cloacal opening. These glands produce a pungent, sweet smelling chemical called castoreum (note: 'near the base of a beaver's tail' simplifies 'next to the cloacal opening') |
| 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 | They bring mud and vegetation up from the bottom, holding it tight to their chest with their forelegs and pushing themselves up the bank with their hind legs until they have a mound. The beaver will then apply castoreum to the mud pile creating a scent mound. |
| To mark its territory | Eurasian beavers are very territorial and mark their territory with castoreum, a form of olfactory communication. They do this by building a scent mound on the shore. |
| A beaver that finds an unfamiliar scent mound in its territory often reacts aggressively, hissing and slapping the water with its tail | Beavers act very aggressively towards an unknown scent mound in their territory often hissing at it and slapping the water with the tail and resurfacing right away. |
| Populations fell nearly to extinction | However due to overhunting for fur and castoreum, a chemical from their castor sacs, and habitat loss, populations fell nearly to extinction. |
| Animal Diversity Web estimates that by the 20th century about 1,300 Eurasian beavers were left in the wild | By the 20th century an estimated 1300 beavers remained in the wild. |
| Freshwater rivers, streams, lakes, and ponds, usually in forested areas with willow, aspen, birch, and alder | Eurasian beavers are semi-aquatic and inhabit freshwater systems, including lakes, ponds, rivers, and streams, usually in forested areas but also in marshes and swamps. Permanent access to water is necessary and preferred tree species for C. fiber are willows, aspen, birch, and alder. (note: stats.habitat) |
| Woody willow, aspen, and birch in winter; aquatic plants, shoots, leaves, and roots in summer | Eurasian beavers are herbivores, feeding primarily on woody vegetation in the winter months. Eurasian beavers prefer willow, aspen, and birch trees ... During summer months beavers feed heavily on aquatic vegetation, shoots, twigs, bark, leaves, buds, and roots. (note: stats.diet) |
| Hard orange-enameled incisors | They have two, large incisor teeth with hard, orange-colored enamel on the anterior surface. (note: stats.superpower, part 1) |
| valved ears and nostrils that close underwater | Both ears and nostrils are valvular and the eyes have nictitating membranes, closing when they go under water. (note: stats.superpower, part 2) |
| dams that flood former uplands and draw in new birds, fish, and amphibians | Through the process of building dams they alter the flow of the water and flood many acres of former uplands. ... This new water source attracts new species of birds, fish, and amphibians by providing a suitable water table. (note: stats.superpower, part 3) |
| orange-toothed dam builder | They have two, large incisor teeth with hard, orange-colored enamel on the anterior surface. (note: tagline; dam building is covered by the body's dam claims) |
| dangerLevel: Low | Negative Impacts crop pest (note: task #717; Low is 'Effectively harmless to people'. ADW's negative impacts are flooding, crops and timber, with no 'injures humans' flag (the raccoon's ADW page carries one)) |
| weightKg: 24 | Eurasian beavers weigh from 13 to 35 kg (note: task #717; midpoint of ADW's range. The name guess puts 'beaver' in Light (<10 kg); the whole 13 to 35 kg range is Medium. Not in a curated matchup) |

## Gazzard (2024). Castor fiber. The IUCN Red List of Threatened Species 2024: e.T4007A218566456.

https://doi.org/10.2305/iucn.uk.2024-2.rlts.t4007a218566456.en

| The page says | The source says |
| :--- | :--- |
| Least Concern | IUCN Red List category: Least Concern (LC). |

## Brazier et al. (2020). Beaver: Nature's ecosystem engineers. WIREs Water.

https://doi.org/10.1002/wat2.1494

| The page says | The source says |
| :--- | :--- |
| 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 | Until relatively recently, it was considered that the North American beaver had a tendency to build dams and lodges more frequently and of a greater size than the Eurasian beaver, but it has now been shown by Danilov and Fyodorov ( 2015 ) that, under the same environmental conditions, the building behavior of the two species does not differ. (note: replaces ADW's older 'much smaller dams and lodges', which this 2020 review supersedes) |
| Great Britain lost its last wild beavers about 400 years ago | beavers were hunted to near extinction and extirpated entirely in countries such as Great Britain (GB) about 400 years ago |
| In recent decades, reintroductions followed by natural spread have returned the species to much of its Eurasian range | In recent decades species reintroductions across Europe, followed by natural expansion has led to the return of C. fiber to much of its Eurasian range |
| a review published in 2012 put Europe's population at over 1.5 million | with a recent review of national population studies, estimating that the C. fiber population in Europe numbers over 1.5 million individuals (Halley et al., 2012 ) (note: the estimate is Halley et al. 2012 as cited by Brazier et al.; dated in the text because it is not a current count) |
| 1.5 million | with a recent review of national population studies, estimating that the C. fiber population in Europe numbers over 1.5 million individuals (Halley et al., 2012 ) (note: covers the tagline's 'over 1.5 million across Europe by 2012') |
| 2012 | with a recent review of national population studies, estimating that the C. fiber population in Europe numbers over 1.5 million individuals (Halley et al., 2012 ) (note: year of the review cited for the 1.5 million estimate (body and tagline)) |
| hunted to near extinction | In the Northern hemisphere, beavers were hunted to near extinction (note: tagline; the review's statement covers beavers in the Northern hemisphere, the body gives the Eurasian detail from ADW) |

## 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.

https://doi.org/10.1016/j.scitotenv.2016.10.122

| The page says | The source says |
| :--- | :--- |
| Researchers introduced two Eurasian beavers to a wooded site on a small stream draining intensively farmed grassland | Two Eurasian beavers (Castor fiber) were introduced to a wooded site, situated on a first order tributary, draining from intensively managed grassland. (note: 'small stream' glosses 'first order tributary') |
| 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 | beaver activity, primarily via the creation of 13 dams, has increased water storage within the site (holding ca. 1000m 3 in beaver ponds) and beavers were likely to have had a significant flow attenuation impact, as determined from peak discharges (mean 30±19% reduction) |
| Water leaving the site carried lower concentrations of suspended sediment, nitrogen, and phosphate | Event monitoring of water entering and leaving the site showed lower concentrations of suspended sediment, nitrogen and phosphate leaving the site |
| two beavers released on a small stream draining farmed grassland | Two Eurasian beavers (Castor fiber) were introduced to a wooded site, situated on a first order tributary, draining from intensively managed grassland. (note: task #717; vibe.reason; 'small stream' glosses 'first order tributary') |
| built 13 dams | primarily via the creation of 13 dams (note: task #717; vibe.reason) |

## 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.

https://doi.org/10.1371/journal.pone.0136751

| The page says | The source says |
| :--- | :--- |
| 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. | We deployed tri-axial accelerometer loggers on 12 free-ranging Eurasian beavers Castor fiber in the county of Telemark, Norway (note: the fitness-tracker comparison is a generic explanation of what an accelerometer is, not a claim from the paper) |
| Researchers glued accelerometers | were attached on the fur of the lower back using two-component epoxy resin (note: epoxy resin is a glue) |
| A computer model fed the motion data told seven behaviours apart, from swimming and grooming to sleeping | we were able to distinguish seven behaviours; standing, walking, swimming, feeding, grooming, diving and sleeping |
| with 95% accuracy | Our random forests model classified behaviours with 95% accuracy |

## 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.

https://doi.org/10.1371/journal.pone.0014622

| The page says | The source says |
| :--- | :--- |
| Second-Largest Rodent on the Planet | Both species are characterized by their large body size, being the second largest rodent, and their semi-aquatic lifestyle (note: heading generalizes the body's second-largest-rodent claim, sourced below) |
| shares the title of the world's second-largest rodent with its North American cousin | Both species are characterized by their large body size, being the second largest rodent, and their semi-aquatic lifestyle |
| The beaver family has only two living species, the Eurasian and the North American beaver | today the family of beavers, Castoridae, is represented by only two extant species, Castor canadensis in North America and Castor fiber in Eurasia |
| a 2011 study of their mitochondrial genomes describes both as the second largest rodent | Both species are characterized by their large body size, being the second largest rodent, and their semi-aquatic lifestyle (note: 2011 is the paper's year (reference and 'Collection date 2011'); the title names mitochondrial genomes) |
| 2011 | Received 2010 Jul 13; Accepted 2010 Nov 10; Collection date 2011. (note: the paper's publication year, covers the FAQ's '2011 genetic study' phrasing) |

## Ansón & García-Prendes (2024). A beaver in the Tagus river: a new location in Spain. Galemys, Spanish Journal of Mammalogy.

https://doi.org/10.7325/galemys.2024.o3

| The page says | The source says |
| :--- | :--- |
| In Spain, where new sites have been reported in recent years | In recent years, different authors have reported new locations for the species. |
| 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 | Here we made the first report of the species in the Tagus river basin. The first sighting occurred in June 2024 at dusk, in Zorita de los Canes, Guadalajara ... The presence of beaver in this area was confirmed by visual contact and some signs on the river banks of the Tagus River ... This new locality is more than 100 kilometers from the nearest beaver area reported previously. (note: 'some' qualifies the signs found, not the confirmation) |

## Approach to beaver management in England. Department for Environment, Food & Rural Affairs / Natural England.

https://www.gov.uk/government/publications/beavers-protection-and-management/protection-and-management-of-beavers-in-england

| The page says | The source says |
| :--- | :--- |
| In England, the Eurasian beaver is a European protected species, and releasing beavers requires a licence | In England, Eurasian beavers are a European protected species under the Conservation of Habitats and Species Regulations 2017. Under the Wildlife and Countryside Act 1981, a licence is required to release beavers in England. (note: page updated 28 February 2025, after the 2022 listing) |