Eurasian Beaver: Fact File

Castor fiber

A complete guide to the Eurasian Beaver, their ecology, history and anatomy, with a clear and simple summary, followed by a detailed scientific literature review.

How to Use This Guide

Contents: Collapse the Contents bar by clicking on the arrow or use its links to jump around the article.

Scientific Background: Click on any grey bar marked ‘Scientific Background’ to see the context for each summary, with a detailed literature review and journal article citations.

References: At the bottom of the document, each citation from the text above has a full reference and link to its source online. Use the Contents to jump to this section.

Introduction

Beavers are perhaps the world’s second most important engineers, creating an amazing array of structures, including burrows, lodges, dams and canals. These all have a huge impact on the ecosystem around them, improving biodiversity, trapping pollutants, cycling nutrients, reducing flooding and restoring reliable flow during droughts.

However, Eurasian Beavers are also known for their teeth, and it’s these which can get them in trouble, as they tend to enjoy nibbling on anything from forestry plantations to agricultural crops (though the impact is usually minimal). Their dams may flood land which is being used for roads, farming or industry, but we’ve learned that they tend to avoid areas of human activity unless their populations get out of control.

Beavers can be a significant help in restoring natural ecosystems, but it’s important to recognise that they also impact humans in their habitat. Where they build dams (and only a fraction of Eurasian Beavers do!), they may even have a negative impact on the climate, as methane production from Beaver ponds is significant.

History of the Eurasian Beaver

Eurasian Beaver in the UK

Eurasian Beaver bones have been found across the UK, which have been verified using DNA sequencing. The species is likely to have gone extinct in Britain between the 14th century – our last carbon-dated record of Beaver activity and 1789 – the last (disputed) written record of a Beaver.

Scientific Background

Eurasian Beaver bone fragments with some remaining DNA have been found across Britain, which conclusively establishes the species as being present in our archaeological past, as recently as 12-11,000 years ago (Marr et al 2018). However, there are historical references to Beavers much more recently than this, with a record of a bounty payment for a Beaver head paid in 1789 (Hitchman et al 2015). The Beaver was supposedly caught on the River Wharfe in Yorkshire, although the recency of this record and a lack of evidence except one line in a parish notebook makes it potentially unreliable. Raye (2015) notes that another such list describes ‘Fairy Heads’, which are actually a colloquial term for the heads of Weasels.

Earlier extinction dates have been suggested in the past, including the 12th century in England and Wales (Halley et al 2009). However, recent trace evidence of beaver gnaw marks on vegetation has been carbon dates their presence on the Tyne River until at least the 14th century (Manning et al 2014). The authors of the study describe how Beavers are unlikely to have had landscape-scale impacts if they survived beyond this point, due to their very low population.

Beaver Extinction

It is thought that Beavers were driven to extinction in the UK by hunting, with Beaver fur being highly prized here, even after their extinction. Evidence from historic texts suggests that they may have survived in Scotland after they were largely wiped out in England and Wales.

Background

Eurasian Beavers were persecuted for both their fur and castoreum glands, with populations across Europe being driven to extinction due to this trade (Ducroz et al 2005). However, in the UK, the trade appears to have been particularly focused on the skins, as Beaver fur continued to be imported even after the animal’s extinction in the UK, but the oil and meat did not appear to be commonly used here (Raye 2015). However, it is possible that meat may have been in some demand in the middle ages, as Beavers’ population in England was already dwindling, when the Catholic Church decreed that Beaver was a type of fish and could therefore be eaten on Fridays (Worsley 2009).

Studies of historic texts suggest that the Beaver went widely extinct in England and Wales before it was wiped out in Scotland (Raye 2015). However, as with any extinction, the exact date is hard to determine as an absence of evidence is not proof in itself.

Eurasian Beaver Reintroductions & Distribution

Eurasian Beavers were reintroduced to the UK both legally and illegally from the early 2000s (and in some instances even earlier), starting in Scotland with an illegal population in Tayside from at least 2001. There are so many captive populations of Beavers across the UK that escapes appear to be inevitable and these Beavers are quick to establish territories. By 2021 there were an estimated 250 wild Eurasian Beaver territories in the wild in Scotland and up to 60 wild in England.

Scientific Background

While no individuals remained from the British population of Eurasian Beavers, their close genetic relatives in Europe were used in the first official and unofficial reintroduction programmes. However, the population of Beavers in Europe dropped to very low levels in ‘fur trade ‘refugia’, which reduced their genetic diversity (Gaywood et al 2018) – an effect seen in other large European mammals like the Bison (Kołodziej-Sobocińska et al 2018)

The first official reintroduction programme was populated by Beavers from Norway, where the population underwent a severe genetic bottleneck relative to the rest of Europe. As a result, there is the potential for negative effects such as inbreeding depression here. However, the Tayside population originated from Bavaria, so genetic diversity in these individuals is more favourable (Gaywood et al 2018).

SCOTLAND
European Beaver reintroductions officially began in the UK with the first trial in Knapdale, Argyll in the West of Scotland in 2009. This was an authorised study to determine the impacts of beavers in a Scottish habitat (Coz et al 2020). However, other populations unofficially established themselves in May 2001 on the River Tay in East Scotland and in 2017 on the River Beauly in the Highlands. The Beauly Beavers were translocated after the colony was discovered (Coz et al 2020). Recent data published by Natural England identified 251 territories of Beavers established in the wild in Scotland, numbering from 602 to 1381 individual animals (Natural England 2021).

ENGLAND
The earliest reported wild-living Beaver in the UK’s recent history was from the 1980s-1990s in the River Axe, Somerset, although this population is believed to have died out in the late 1990s (Natural England 2021).

In 2021, Natural England estimated that there were as many as 400 beavers living wild in England, with up to 60 territories, just 15 of which were in the sanctioned River Otter watershed. Other populations were found on the River Stour (Kent), River Tamar, Little Dart River (Devon), River Avon, River Frome and Brue (Somerset & Wiltshire). The organisation confirms that there were at least 5 or 6 escapes from fenced beaver collections in England between 2000 and 2021:

Somerford Keynes: 2006
Lifton: 2008
Ham Fen: 2009 (and possibly 2008)
Ottery St Mary: 2011 (and possibly 2010)
Castle Coombe (date not specified)

Most Beavers released in early programmes were sourced from Bavaria in Germany, while later individuals largely came from Scottish populations (Natural England 2021). The Beavers on the River Otter were caught up in 2015 and screened for disease before being re-released as part of the first offically-sanctioned reintroduction programme in England, which ran for 5 years.

WALES
While signs of beaver activity have been reported in the Wye catchment, a detailed analysis revealed no signs of breeding or residency, but rather individuals moving through the area (Campbell-Palmer, 2021).

Ecology of the Eurasian Beaver

Territory Size

Eurasian Beaver live in family groups of 2 to 7 animals, aggressively defending a territory about 3.5km in length, which typically runs along a river. Mounds are marked with scent from the animal’s castor glands, and territorial displays include tail slapping and hissing. Breeding Beavers may live with another individual or non-breeding pair. Young beavers travel 5-10km from home to set up a new territory.

Scientific Background

Beavers typically live in families, with an adult breeding pair and their current and previous year’s offspring. These groups range from 2 to 7 animals in size, with an average group size of 3.7 (Żurowski, & Kasperczyk 1986) and may share a territory with a single beaver or non-breeding couple. These territories are aggressively defended but vary in size, depending on their population density and the habitat quality and availability.

Beaver territories vary from 0.5km to 20km across, with an average of 3.6km. Territories usually follow the course of a river, although animals may travel across land between watersheds (.

Beavers leave home to establish a new territory, which is on average 5-10km away, though distances up to 80km and beyond have been reported.

(Multiple sources, as cited in Section 1.4 of Campbell‐Palmer et al 2021)

Scent marking is an important part of defending a territory (Nimje et al 2021), with the animal’s castor glands used to secrete a substance which mixes with urine to form ‘castoreum’. This is deposited on mounds, which are mostly located at the territory’s edge, with up to 7 per colony. Smelling a rival’s scent on one of these mounds may cause aggressive behaviours including tail slapping and hissing, and the mound could be rebuilt (Macdonald & Barrett, 1993).

Diet

While Beavers have a reputation for ‘eating wood’, this is actually a myth – after felling small trees and shrubs within 10m of the water, they drag these back to the river or lodge and only consume the bark, leaves and shoots. In fact, Beavers will typically only eat this woodier material (usually Willow) as the main part of their diet when green vegetation isn’t available, as they prefer aquatic plants and leaves. While they do eat some crops like Oilseed Rape, their impact is negligible – less than typical agricultural rodents.

Scientific Background

Beavers preferentially forage on green vegetation, only turning to ‘the bark of trees and shrubs’ as a major part of their diet when this material is unavailable, such as in Winter (Mikulka et al 2020, Haarberg & Rosell 2006). They preferentially fell smaller trees within 10m of the water, typically Willows (Schley 2004, Bełżecki et al 2018) then carry these back to the water or their lodge to eat the leaves and bark (Haarberg & Rossell 2006).

A study of Beaver’s aquatic feeding behaviours described how aquatic plants can make up 90% of their diet in certain seasons and locations. The introduction suggests that Beavers’ typical diet ‘comprised primarily bark from deciduous trees during winter’, however, this quote draws from both American and Eurasian Beaver research (Mortensen et al 2021).

A ruthless, but effective Polish study (Bełżecki et al 2018) gave clear insights into how the diet of wild beavers varies seasonally. 36 adult beavers were captured and euthanised across different seasons and their guts examined to determine the exact proportion of different vegetation. The sample size was small, and the results were affected by the absence of aquatic plants in the wider habitat. However, the researchers found that Beavers supplemented their diet with rapeseed, which confirmed similar results in earlier research.

Shoots (mainly Willow) were 91% of the diet in Winter, 30% in Summer and 72% in Autumn
Herbs were 7% of the diet in Winter, but 15% in Summer and 14% in Autumn
Grass were 3% of the diet in Winter, but 20% in Summer and 12% in Autumn
Rapeseed was 0% of the diet in Winter, but 19% in Summer and 0% in Autumn
Tree leaves were 0% of the diet in Winter, but 8% in Summer and 1% in Autumn

Beavers are thought to use the bark in their dams as a source of nutrition when they are sealed into their home by ice in winter (Macdonald & Barrett 1993).

Habitat

Beavers have evolved for an ecosystem where rivers meander through scrub and woodland. They seek out habitats where at least 50% of the banks are covered with vegetation to 20m from the water’s edge, and ideally up to 50m away. These animals prefer Aspen and Willow woodlands, and they live either in burrows at the edge of the river, or in lodges set in the water, constructed from felled trees, with protected underwater entrances.

Scientific Background

Beavers typically inhabit wide river valleys with floodplains and plenty of softwood trees along the banks (‘riparian vegetation’) (Macdonald & Barrett 1993). A Luxembourg study found that Beavers prefer to eat within 10m of the riverbank, so a strip of at least 10m shrub or woodland is preferred (Schley 2004).

A detailed study (Gaywood et al 2018) of the Beaver population in Scotland found that Beaver activity is typically confined to freshwater areas and neighbouring banks, especially in scrub or broadleaf woodland habitats. The animals show a preference for Willow and Aspen, but avoid Alder, which is common on river banks. Most activity happened within 20m of the water, or exceptionally up to 50m away.

Both Gaywood et al (2018) and Macdonald & Barrett (1993) describe how Eurasian Beavers can live in either burrows and/or lodges. Family groups at Knapdale built from 1 to 3 lodges – these have an underwater entrance, to provide protection from predators. Dams and canals are detailed in the ‘Rewilding’ section.

Gaywood et al (2018) describe how Beavers seek out streams and rivers with less than 15% gradient, no tidal influence and riparian woodland or scrub. Sections of riparian vegetation should ideally be at least 1.9km long along a 4km stretch of river, in order to be viable Eurasian Beaver habitat. Although Beavers do not inhabit marine environments, North American Beavers have been documented swimming up to 6km offshore in Patagonia, so island colonisation is possible. Watercourses from 0.3m to 6m in width were most suitable for Beaver dams.

Rewilding the Eurasian Beaver

Habitat Engineering

Beavers are, after humans, perhaps nature’s greatest habitat engineers, constructing dams, lodges, burrows, canals, and felling trees. However, their reputation for building dams is overblown, as these animals prefer territories in deeper water where they can make burrows in a river bank instead.

Dams are created from sticks, branches and mud in shallower rivers and streams, generating pools 70-100cm in depth which contain underwater winter food caches and the lodge. The Beaver lodge is a safe home, constructed from turf, mud, sticks and branches with underwater entrances and ventilation shafts.

When Beavers regularly forage along the same, flat, route, they may dig a ‘canal’ to extend their pond. This protects them from predators and makes it easier to travel back and forth with branches.

Beavers typically fell smaller trees, less than 5cm in diameter, with larger trees only taken in Autumn, to prepare their caches of Winter food (bark, shoots and leaves).

Scientific Background

Beavers build dams out of tree branches, sticks and mud to raise the water level in the resulting ponds upstream (Macdonald & Barrett 1993). This allows them better access to food resources including aquatic plants, more space to create deep water food caches and a reduction in predation risk by providing cover from above and reducing time spent on land (Graham et al 2020). Hartman & Törnlöv (2006) found that dams are only constructed to raise water level to between 70cm and 100cm in depth, with dams constructed in rivers and streams between 10cm and 85cm deep. The water level is then maintained at a height which allows the animals to enter their lodge (located within the pond behind the dam) underwater (Janiszewski et al 2014).

While the typical assumption is that Beavers and dams are synonymous, a 2001 study in Germany found that only 19% of Beavers colonies had dams (Zahner 2001). In fact a range of studies cited by Hartman & Törnlöv (2006) suggest Beavers preferentially select deep water habitats which do not require modification, rather than constructing dams to create deep water. Beavers tend to colonise smaller streams once the larger rivers in an area are already occupied. However, despite this lack of interest in dam-building, when Beavers are present in high density there may be as many as 24 dams in 1.3km of river (Zurowski 1989).

As routes through water are both safer and less energy-intensive, beavers may dig canals across flatter land to reach food and wood sources (Halley et al 2009). These canals are typically constructed along routes which are already established as a reliable land route, so they complement and extend the potential area for land-based foraging (Campbell-Palmer et al 2016).

Beaver dams are not necessarily permanent structures – they may be used for a relatively short period of time depending on food availability in the area. One of their primary purposes may also be maintaining access to submerged food caches when the surface of the pond is frozen over winter and access from the lodge to other food is impossible (Campbell-Palmer et al 2016).

Like dams, Beaver burrows in river banks are also inherently temporary structures, requiring maintenance to prevent them from collapsing within ‘one or two years’ after they are left empty. However, lodges, constructed from sections of trees and shrubs, in addition to turf and mud, are a more permanent structure, which remain in the landscape for more than 10 years. Lodges are complex structures, containing living chambers, ventilation shafts and holes for access (Samas & Ulevičius 2015).

Beavers tend to fell larger trees in autumn, when they are preparing winter food stores (Halley et al 2009) but 95% of the trees they felled in a Norwegian study were under 5cm in diameter. Deciduous trees, especially Aspen and Willows, are preferred and conifers are are almost never taken (Haarberg & Rosell 2006).

Impacts on Natural Processes

Beavers’ main impact on an ecosystem is the creation of a zone of slow-flowing water, which becomes a trap for soil and nutrients. This is a biodiverse haven for plant and animal life, with warmer, less oxygenated water that benefits from a lack of shade.

However, Beavers also create many other important habitats, from lodges, which can be home to a diverse collection of small mammals, to the edges of ponds, which are plant biodiversity hotspots. When their burrows collapse, these create new shallows at the edge of the river and the general pattern of flow is changed by their dams, with many new microhabitats of both slow and fast flowing waters.

Scientific Background

The presence of a Beaver dam changes the water dynamics behind it from a ‘lotic’ (flowing water) to a ‘lentic’ (still water) system (Brazier et al 2021). According to Janiszewski et al (2014), this change in water speed has a variety of effects, from increasing deposition of sediment and associated nutrients, to changing the type of species which inhabit the river. The biomass of insects increases, but as the open water expands, woodland (or other bank habitat) is lost, opening up the canopy and promoting the growth of swamp-loving Willow and Alder.

The pH and oxygen levels of the river shift as organic matter builds up and begins to decompose in the pond. Water temperature increases as the flow slows down and spreads out over the floodplain, which leads to a spike in the growth of plankton (Janiszewski et al 2014). This habitat is also ideal for promoting the growth of aquatic plants, with high levels of plant-available nitrogen, carbon and phosphorus in an unshaded environment (Brazier et al 2021).

When Beaver burrows collapse after they fall out of use, this creates changes to the structure of river banks which permits the growth of rushes and may creates new shallows in the river (Janiszewski et al 2014). The burrows themselves may be colonised by small vertebrates, including mammals, reptiles and amphibians (Samas & Ulevičius 2015).

Beaver lodges are complex structures with many crevices which, even during occupation, provide opportunities for other animals to find a home. 11 species of small mammal were caught on Lithuanian Beaver lodges in an attempt to determine the biodiversity of these microhabitats (Samas & Ulevičius 2015).

In general, Beavers tend to create a diverse ‘mosaic habitat’, with their canals, collapsed burrows, dams, lodges, ponds and the browsed margins of rivers all contributing to this mosaic (Janiszewski et al 2014, Brazier et al 2021). Their structures changes the uniform flow pattern of the river, creating zones of variable speed which provide niches for collections of different species (Brazier et al 2021). The structural diversity of this mosaic habitat also creates high biodiversity due to several transition zones at the water’s edge with variability in moisture levels, which house complex plant communities (Brazier et al 2021).

Impacts on Human Interests

The most important ecosystem service which Beavers provide is flood protection, with their dams able to reduce the size of downstream flooding events by ~60%. However, these ‘leaky dams’ also keep the water flowing during a drought by acting as a reservoir and effectively filter farming pollution, including Nitrogen and Phosphorus. The ponds also act as a store of carbon, with double the effectiveness of non-dammed streams.

However, Beaver ponds are known to emit methane, a powerful greenhouse gas, though the impact of this is offset by the ponds’ other environmental benefits, including nutrient cycling and reducing soil erosion. Eurasian Beavers can be a very minor agricultural pest, causing €25/animal in crop damage per year, but their reputation for damaging Salmon stocks is undeserved and fish experts believe they are beneficial to fish populations.

While Beaver can occasionally cause damage to agricultural and forested land and infrastructure, their dams may be bypassed with pipes. Beavers avoid areas of human activity except when overpopulation occurs, so culling is necessary if there are no natural predators present.

Scientific Background

Perhaps the most important impact of Beaver dams on humans is flood prevention – their leaky dams have been shown to improve water storage in river systems, which increases the lag from rainfall to peak flow, reducing the size of flooding events and the likelihood of flash floods. The dams are also effective at maintaining flow during periods of drought by acting as reservoirs, particularly when there are a higher density of them in the watercourse (various sources, cited in Puttock et al 2021). Beavers may reduce the overall size of floods by up to ~60% according to a recent UK data analysis by Puttock et al (2021).

Due to the way that water slows down and nutrients are deposited in a Beaver pond, these structures are effective at trapping nitrogen and phosphorus pollution (which can cause ecological damage). Several studies found that high levels of nitrogen and phosphorus from agricultural activity were severely reduced downstream by the presence of Beaver dams (Brazier et al 2021).

Beaver ponds can increase the level of carbon sequestration, with double the levels of dissolved organic carbon and carbon in sediments when a Beaver dam was present. However, as with all dams, a large area of still water is a net producer of methane, and the Beaver pond is no exception, with clear evidence from a study in Siberia that this is the case. These ponds do compensate by improving the rate of nutrient utilisation from the water, with four times more riparian vegetation than in non-dammed streams, which offers another opportunity for Carbon sequestration and reduces loss of nutrients from the local area (Gatti et al 2018).

Beavers’ impact on agricultural crops was assessed in a recent study (Mikulka et al 2020), which determined that, although they do seek out this vegetation, the effect is negligible compared to typical rodent damage. Total damage was estimated at €20-30 per animal per year.

It has been suggested that Beaver dams could affect the ability of Salmon to migrate upriver. However, a small scale study of river in Norway found the opposite effect – juvenile Salmon populations were highest in areas around Beaver dams, although the ponds did not appear to be highly populated, in contrast to findings in N America (Malison & Halley 2020). Trout populations appeared to be negatively affected by the presence of a Beaver dam.

Natural England (2021) reported that a survey of fisheries experts from Europe and North America revealed Beavers were expected to have ‘an overall positive impact on fish populations’.

However, while Beaver populations distant from humans may be beneficial, where they have no natural predators and are not culled, overpopulation causes them to come into zones of human activity. This is where their activities, such as dam building and tree felling, can cause financial damage to agricultural crops, forestry and infrastructure like roads and railways (Wróbel 2020). However, in the U.S. state of Maine, only 18 conflict points were reported across over 50,000 hectares of heavily Beaver-populated land, despite a significant human infrastructure (Lisle 2003).

Flow devices can be used to sneak water past dams and reduce their impact on the surrounding landscape where they are causing impacts on human activities. ‘Beaver Deceivers’ consist of pipes and fences which bypass the dam and prevent Beavers from blocking the bypassed flow. These are often effective, although they require some understanding to implement (Lisle 2003).

Beaver culling may be necessary to control their population, in the absence of natural predators. However, if it is carried out in the wrong way, this can cause damage by selecting for sexually immature breeding pairs. Żurowski & Kasperczyk (1986) recommend the culling of ‘old animals with reduced reproduction’ and ‘young animals in their first year’ to avoid negative impacts on population health.

Body of the Eurasian Beaver

Weight

Beavers continue putting on weight throughout their lifetime, with females averaging 5-10% heavier than males. A 4 year old Eurasian Beaver is ~20kg, while a 12 year old is ~24kg – maximum recorded weight is 38kg.

Scientific Background

A study of wild-living Beavers in Norway found that their body weight continued to increase over their lifespan. However, there was some sexual dimorphism which also increased with age, with females of an equivalent age weighing 5-10% more than males. At age 4, females weighed 20kg, while males weighed 19kg. By Age 12, females weighed 24kg and males weighed 22kg (Campbell et al 2017).

According to Macdonald & Barrett (1993), weight varies by region, with individuals weighing up to 38kg, although this source disputes the sexual dimorphism described above.

Size

Adult females are 98cm long and males are shorter at 90cm long, with an extra 30cm of tail. Young ‘kits’ are 42-62cm in length, measured snout to base of the tail.

Scientific Background

Beavers’ length is typically measured in studies from the tip of their nose to the base of their tails; in a 2017 study, baby Eurasian Beavers measured from 42cm to 62cm in length at birth. (Campbell et al 2017). Adults range from 80-110cm in length, with an additional tail length of 30-35cm, with females longer on average at 90cm and females 98cm long (Halley et al 2009).

Age

The average wild Eurasian Beaver lives for 7-8 years, but a maximum lifespan of 20-25 years has been recorded.

Scientific Background

Data from a wild-living population of Eurasian Beavers in Southern Norway, (which is likely affected by a historic genetic bottleneck) revealed an average age at death of 7 years. However, individual Beavers have been reported as living up to 20 years of age (Campbell et al 2017) or 25 years (Macdonald & Barrett 1993). An average lifespan of 7-8 years is confirmed by Macdonald & Barrett (1993).

Reproduction

Eurasian Beavers typically give birth to litters of 1.7 ‘kits’ at a time after 105 days of pregnancy from February to June. Kits emerge from the lodge in July, then remain with their parents until sexual maturity at 1.5 to 2.5 years of age.

Scientific Background

Young beavers are born during the Summer and remain with their parents for that season and the following year before leaving to find a new territory (Macdonald & Barrett 1993). Beavers reach maturity at between 1 .5 and 2.5 years old but achieve their peak reproduction at around age 6-7 (Campbell et al 2013, Campbell et al 2017). Males are unlikely to breed successfully before they are 3 years old (Macdonald & Barrett 1993).

Gestation lasts for 103 to 108 days, with from 1 to 6 babies being born (Macdonald & Barrett 1993), averaging 1.7 per litter in a Norwegian study of wild-living Beavers (Campbell et al 2017). The offspring – ‘kits’ – are weaned at 1-2 months old although they are born fully furred, and they come out of their lodge for the first time in about mid-July (Campbell et al 2013).

Females between 2 and 7 years old were 44% likely to reproduce, while individuals from ages 8-15 were just 25% likely in the Norwegian study. Male and female beavers can be told apart by the colour of their anal gland secretions. Longer adults are more likely to be dominant in the breeding population and therefore produce more offspring (Campbell et al 2017).

References

A quick search of Google Scholar for an article’s title is often enough to find a free PDF – but for those with a paywall, there is another easy way of accessing literature for free (publishing this method could result in How to Rewild getting sued, so we recommend searching for this independently).

Complete Reference List

Bełżecki, G., et al. “Seasonal variations of the digestive tract of the Eurasian beaver Castor fiber.” Mammal research 63.1 (2018): 21-31.

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