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1
INTRODUCTION
This paper is the third review – including short updates
the fifth paper – intended to summarise Eurasian beaver
Castor fiber distribution change and population develop-
ment (Nolet & Rosell 1998, Halley & Rosell 2002, 2003,
Halley et al. 2012; a population estimate for Europe was
also recently presented in a short communication, Wrobel
2020). The status of the North American beaver Castor
canadensis in Eurasia is also reviewed. Information avail-
able is copious, but very widely scattered. Some is available
in peer-reviewed papers, but most is in national- or
REVIEW
Population and distribution of beavers Castor fiber and
Castor canadensis in Eurasia
Duncan J. HALLEY*Norwegian Institute for Nature Research, PO Box 5685 Sluppen, Trondheim,
NO-7485, Norway. Email: duncan.halley@nina.no
Alexander P. SAVELJEVDepartment of Animal Ecology, Russian Research Institute of Game
Management and Fur Farming, 79 Preobrazhenskaya Str., Kirov, 610000, Russia. Email: saveljev.
vniioz@mail.ru
Frank ROSELLDepartment of Natural Sciences and Environmental Health, Faculty of Technology,
Natural Sciences and Maritime Sciences, University of South-Eastern Norway, Gullbringveien 36, Bø i
Telemark, NO-3800, Norway. Email: Frank.Rosell@usn.no
Mammal Review 51 (2021) 1–24 © 2020 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution
in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Keywords
beaver, Castor fiber, Castor canadensis,
distribution, Eurasia, population,
reintroduction
*Correspondence author
Received: 4 May 2020
Accepted: 17 June 2020
Editor: DR
doi: 10.1111/mam.12216
ABSTRACT
1. A century ago, overhunting had reduced Eurasian beaver Castor fiber popula-
tions to c. 1200 animals in scattered refugia from France to Mongolia.
Reintroductions and natural spread have since restored the species to large
areas of its original range. Population has more than tripled since the first
modern estimate in 1998; the minimum estimate is now c. 1.5 million.
2. Range expansion 2000–2020 has been rapid, with large extensions in western
and south-central Europe, southern Russia, and west and central Siberia.
Beavers are now re-established in all countries of their former European
range except for Portugal, Italy, and the southern Balkans; they occur broadly
across Siberia to Mongolia, with scattered populations father east. About half
of the world population lives in Russia. Populations appear to be mature in
much of European Russia, Belarus, the Baltic States, and Poland.
3. There is a significant population of North American beaver Castor canadensis
in Finland and north-west Russia. Most other 20th-Century introductions of
this species have become extinct or been removed.
4. Recent DNA studies have improved understanding of Castor fiber population
prehistory and history. Two clades, east and west, are extant; a third ‘Danube’
clade is extinct. Refugial populations were strongly bottlenecked, with loss of
genetic diversity through genetic drift.
5. Future range extension, and large increases in populations and in impacts on
freshwater systems, can be expected. Beavers are now recolonising densely popu-
lated, intensely modified, low-relief regions, such as England, the Netherlands,
Belgium, and north-west Germany. They will become much more common and
widespread there in coming decades. As beavers are ecosystem engineers with
profound effects on riparian habitats, attention to integrating beaver manage-
ment into these landscapes using experience gained in other areas – before the
rapid increase in population densities and impacts occurs – is recommended.
Mammal Review ISSN 0305-1838
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D. J. Halley, A. P. Saveljev and F. Rosell
Population and distribution of beavers in Eurasia
2Mammal Review 51 (2021) 1–24 © 2021 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
regional-level reports, popular articles, and other sources
not searchable in scientific databases.
The Eurasian beaver is on the threshold of large exten-
sions in geographic range, and exponential growth in
population, in many parts of western and south-central
Europe, including some of the most heavily populated
and human-modified regions of the world. This, the amount
of information relevant to understanding beaver popula-
tion development accumulated since the last review, and
the large changes in population and distribution since the
last update, make a new review timely.
METHODS
We collect sources on the Eurasian population and dis-
tribution of both species of beaver, and patterns of popu-
lation development, on an ongoing basis. Principal sources
are searches of Internet science literature databases, general
Internet searches, grey literature, conferences, and personal
correspondence. Maps of beaver distribution and the popu-
lation table are updated as new information is received.
Beaver populations develop on watersheds (Hartman
1994a, 1994b, 1995) and should ideally be considered on
a watershed scale. However, almost all information is
available at a national or sub-national scale. Here, we
present data by country, following the structure of Halley
and Rosell (2002) for ease of comparison. ‘Beaver’ means
the Eurasian beaver unless otherwise stated.
TAXONOMY, GENETICS, AND
REINTRODUCTIONS
Recent advances in DNA studies have deepened and modi-
fied understanding of the species’ post-Ice Age and bot-
tleneck period population histories.
Previously, eight subspecies, one for each 19th to early
20th-Century refugium, were identified (see, e.g. Lavrov
1983, Nolet & Rosell 1998). The reality of this subdivision
has long been doubted (e.g. Halley & Rosell 2002, Halley
2011, Rosell et al. 2012, Horn et al. 2014), and it is no
longer tenable in the light of modern genetic studies. For
example, “Ancient British beavers … formed part of a
large, continuous, pan-Western European clade that har-
boured little internal substructure” (Marr et al. 2018).
Senn et al. (2014) considered that “A likely suggestion is
that divergence in mtDNA haplotypes (into ‘western’ and
‘eastern’ phylogroups) did indeed arise following popula-
tion retreat into glacial refugia during the last glacial
maximum (~25000 ya), but that introgression following
secondary contact of re-emergent populations caused sub-
sequent mixing of divergent haplotypes in contact regions”.
This agrees with genetic evidence from a wide range of
other species indicating recolonisation of Europe from two
main Ice Age refugia in the Balkans and southern France/
Iberia (e.g. Hewitt 2000).
In addition, Durka et al. (2005) identified an extinct
‘Danube’ clade, neither ‘western’ nor ‘eastern’, while both
Biedrzycka et al. (2014) and Munclinger et al. (in prepara-
tion) identify DNA markers apparently present in no known
refugial population. These are likely to be explained (though
other explanations are possible) by the survival of one or
more populations in north-central Europe in addition to
the eight known. Saveljev et al. (2011) also found genetic
differentiation in beavers from the Pripet refuge, corre-
sponding to different rivers in which beavers survived,
flowing separately from the Pripet Marshes area.
Further genetic research deepening or modifying un-
derstanding of Castor fiber population history can be ex-
pected. We name, as appropriate below, the refugia
reintroduction stock came from. This allows assignment
to the earlier ‘subspecies’ if so desired.
HISTORY AND STATUS OF BEAVER
POPULATIONS BY COUNTRY
Halley and Rosell (2002) provide information on beaver
source populations, and details of location and size of
reintroductions, before 2002. European distribution in 2002
is shown in Fig. 1; current distribution in Fig. 2. Asian
distribution in 2002 is shown in Fig. 3, and current dis-
tribution in Fig. 4. Dates of extinction, legal protection,
and reintroductions, and current population estimates for
each country are given in Table 1. Fig. 5 shows the mini-
mum population estimates from 1998 to 2019.
Austria
In Austria, 40 Eurasian beavers were reintroduced (several
sites) in 1970–90 (Halley & Rosell 2002). Beavers have also
immigrated to Austria from Bavaria, Germany, in large num-
bers. Beavers from Austria have colonised adjacent regions
of Slovenia, Hungary, Slovakia, the Czech Republic,
Switzerland, and Italy. The Universität für Bodenkultur, Wien,
maintains a website on beavers in Austria (https://www.dib.
boku.ac.at/iwj/forsc hung/proje kte-aktue lle-infor matio nen/
der-biber -casto r-fiber -in-oeste rreic h/). The population was
estimated as 7600 in 2017. The latest available map (Appendix
S1 and see website) dates from 2012. Nine North American
beavers were also introduced in the 1980s, but no beaver
carcasses examined in later years have been of this species;
it appears to have become extinct (Sieber 2000).
Belarus
Beavers survived in the Pripet, Berezina, and Neman Rivers,
Belarus, and were reintroduced widely in the Soviet period.
Population and distribution of beavers in Eurasia
D. J. Halley, A. P. Saveljev and F. Rosell
3
Mammal Review 51 (2021) 1–24 © 2020 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
Beavers from these three populations differ significantly
from one another in morphological and biological char-
acters (Samusenko & Fomenkov 1983). Recent genetic data
indicate that combining all beavers of Belarus stock into
one subspecies, Castor fiber belorussicus, is not valid (Saveljev
et al. 2011).
Beavers are now distributed throughout Belarus. The
National Statistical Committee (http://www.belst at.gov.
by/en/) publishes annual population figures in English.
The figure for 2017 was 51100. Figures suggest a peak-
ing and decline in population in recent years (2011:
60500; 2012: 64400; 2013: 62000; 2014: 63400; 2015:
58300; 2016: 51300).
Litvinov et al. (2012) describe the modern populations
of beavers. Belarus is developing a national management
strategy, aimed at achieving more intensive hunting and
use of beaver derivatives – meat and castoreum (G. Yanuta
personal communication).
Belgium
Although vagrants from German reintroductions occurred
previously, beavers in Belgium descend mainly from
unofficial releases of 101 individuals in 1998–2000 to
several sites, mainly in the Ardennes, and an unofficial
release in the Dijle and Laan Rivers of Flanders in 2003
(all openly publicised). Other beavers have spread into
Flanders from the Netherlands, also in 2003. All source
to the mixed stock population in Bavaria (Verbeylen
2003).
The Flanders population in 2018 was c. 155 territories,
minimum 400 beavers (J. van den Bogaert, and Belgium
Beavers Working Group, personal communications); in
Wallonia c. 650 territories or 1800–2000 beavers
(Bernaerts 2016; J.-P. Facon, Gouvernment Wallonie,
and Belgium Beavers Working Group, personal com-
munications). Distribution in 2016 is shown in
Appendix S2.
Bosnia and Herzegovina
Forty beavers were released on the Semešnica and
Sokočnica Rivers, south of Banja Luka, Bosnia and
Herzegovina, in 2005 and 2006 (Trbojević & Trbojević
2016). Beavers have also spread throughout the Sana
and parts of the Korana and Una rivers in north-west
Bosnia from Croatia, to the lower Drina River in the
east from Serbian reintroductions, and along the Bosnian
side of the Sava River, from Croatia and Serbia. Trbojević
and Trbojević (2016) estimated the 2016 population at
c. 140. Population growth rates, and the scattered dis-
tribution away from the reintroduction sites (Appendix
Fig. 1. Beaver distribution in Europe in 2002. Black = refugia where Eurasian beaver was never extinct. [Colour figure can be viewed at wileyonlinelibrary.com]
D. J. Halley, A. P. Saveljev and F. Rosell
Population and distribution of beavers in Eurasia
4Mammal Review 51 (2021) 1–24 © 2021 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
S3; Trbojević & Trbojević 2016; Figs 1 and 2), suggest
that beavers are still in the ‘establishment’ phase (Hartman
1994a, 1994b, 1995, Halley & Rosell 2002). Rapid in-
creases on all of these rivers can be expected.
Bulgaria
A recent study (Boev & Spassov 2019) documents former
beaver presence throughout Bulgaria and extinction in
1750–1850. Spread from Romania is likely in the near
future.
China
A native population is found in Xinjiang in the far north-
west, in the upper part of the Ulungur (Wulungu) river
(upper Ob watershed; Lavrov & Lu 1961). Beavers also
live on the partly Mongolian Chinge and Bulgan River
tributaries. These populations are threatened by unsustain-
able water and soil exploitation, forest destruction, and
agricultural expansion. There are more than 60 irrigation
dams on the Ulungur River. The dam closest to the
Mongolian border completely isolates Mongolian from
Chinese subpopulations.
50 km of the Bulgan was designated as the Bulgan
River Beaver Reserve in 1980. In 1992, beavers were
translocated from the Bulgan to the Irtysh River to re-
duce risks of genetic bottlenecking, but results were
unsatisfactory (Huang 1993). A 2007 survey on the Bulgan
showed 145 families with 508–645 beavers (Chu & Jiang
2009).
Beavers are Critically Endangered in China (Jiang et al.
2016). The population is estimated as <600.
Croatia
Beavers were reintroduced to Croatia from Bavaria in
1996–98. Forty-eight were released on the Sava River near
Ivanic Grad and 29 on the Drava at Legrad. Nine were
released on the Česma, a Sava tributary near the main
release site (Grubesić et al. 2001, Cavric 2016). Beavers
are now widespread in the Croatian Drava and Sava River
basins and have spread into Slovenia, Bosnia and
Herzegovina, Hungary, Slovenia, and Austria (on the Mura,
via Slovenia). The population in Croatia is estimated at
10000 (Tomljanović et al. 2018).
Czech Republic
History and status of beavers in the Czech Republic are
reviewed by Vorel et al. (2012) and Vorel and Korbelova
(2016). Recolonisation from Austria on the Morava River
(Danube watershed) began in 1988 and from Germany
on the Elbe in 1992. There has also been recolonisation
in the south-west Czech Republic from Bavaria since 1993.
These movements were supplemented by reintroductions
Fig. 2. Beaver distribution in Europe in 2020. Black = refugia where Eurasian beaver was never extinct. [Colour figure can be viewed at wileyonlinelibrary.com]
Population and distribution of beavers in Eurasia
D. J. Halley, A. P. Saveljev and F. Rosell
5
Mammal Review 51 (2021) 1–24 © 2020 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
in the 1990s (Halley & Rosell 2002). Beavers are now
widespread in Moravia and appear near to capacity on
the Morava watershed, which drains most of the region
(Vorel & Korbelova 2016). They are also widespread in
the south-west, with scattered populations in central and
north-western regions (Appendix S4). Population size for
the Czech Republic is estimated at >6000. Rapid spread
and linkage of populations are predicted in the coming
decade (Vorel & Korbelova 2016). Development has con-
formed to the typical pattern: rapid spread within a wa-
tershed to high-quality sites, with infilling of steadily less
optimal habitat thereafter (John et al. 2010, Barták et al.
2013). The rate of spread into unoccupied stretches of
main rivers approximates 20 km/year during the rapid
expansion phase (John et al. 2010, Bártak et al. 2013).
A national management plan was adopted in 2003 (Vorel
& Korbelova 2016). Natura 2000 sites, 1.2% of the Czech
Republic, are completely protected; in most of the country
(86%), management measures are permitted as necessary;
and the ‘south Bohemian fishpond basin’ (13%) with large
numbers of earth retention dykes is zoned as incompatible
with beaver settlement.
Denmark
Elbe beavers were reintroduced at Klosterheden in Jylland,
Denmark, in 1999, and at Sjælland near Copenhagen in
2009–11. In Jylland (Appendix S5; Elmeros 2017), the
population has spread to a number of stream systems in
the northern and central peninsula. The beaver population
in Jylland numbered 98 territories, or an estimated 166–202
animals, in 2017 (Elmeros 2017). Taidal (2018) reported
13 territories (c. 50 individuals) in Sjælland.
England
A number of releases inside enclosures in England have
been made since 2002. Beavers have been living wild on
the River Otter in Devon, south-west England, since at
least 2008, where breeding is confirmed from 2014. Their
origin was unknown, and the government initially planned
to remove them. This changed, partly as a result of elec-
toral politics (the government wished to avoid controversies
that might lose votes in an election), and the proposal
of the Devon Wildlife Trust for a five-year ‘trial’ of the
beavers’ effects on the landscape was accepted in 2015
(Crowley et al. 2017). This involved supplementing the
population with further releases. Thirteen family groups
are now established (Devon Wildlife Trust 2016, Brazier
et al. 2020). Brazier et al. (2020) provide a comprehensive
report on the population, its development, and impacts.
In 2018, it became clear that beavers were living wild
elsewhere in England: on the Tamar River, the Kent Stour,
and the Wye on the Welsh border, and in the Somerset
levels (Swaile et al. 2018; Appendix S6). Most are Bavarian
stock (Campbell-Palmer et al. 2020), though the Kent Stour
animals appear to be descended from enclosed Norwegian
beavers at Ham Fen. Ten populations living in enclosures,
and 13 projects in development, fenced and free-living, were
identified (Campbell-Palmer et al. 2020; Appendix S6).
Fig. 3. Beaver distribution in Asia in 2002. Black = refugia where Eurasian beaver was never extinct. [Colour figure can be viewed at wileyonlinelibrary.com]
D. J. Halley, A. P. Saveljev and F. Rosell
Population and distribution of beavers in Eurasia
6Mammal Review 51 (2021) 1–24 © 2021 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
Natural England is reviewing evidence from the River Otter
trial and will make a recommendation on the desirability
of further reintroduction (Campbell-Palmer et al. 2020).
Estonia
Beavers were reintroduced to Estonia in 1957 and spread
naturally from releases in Russia and Latvia. They are
now present throughout the country, except for parts of
the Baltic islands. The harvest has increased steadily to
2017 (7038 animals), and the number of families increased
from 2256 in 2012 to 2494 in 2015 (Veeroja & Männil
2018). Hunters’ estimates of the population, however,
declined from a peak of 20000 in 2008 to 14000 in 2016
(Veeroja & Männil 2018). The most recent estimate is
12–13000 individuals in 2016 (Sjöberg & Belova 2020).
Beavers were the Hunting Association’s ‘animal of the
year’ for 2019 (http://www.ejs.ee/aasta -loom-2019-kobra s/).
Finland
The government of Finland collects high-quality data on
beaver populations, available online in English (LUKE
2019); see also Fig. 6. Eurasian beavers from Norway, and
North American beavers from the USA, were released in
1935–37 (Lahti & Helminen 1969). The North American
beaver population is most dense in Pohjois-Karjala, Etelä-
Savo and Pohjois-Savo, but the species also occurs in other
parts of eastern and central Finland, and sporadically in
Lapland (Fig. 6). It is spreading westwards in southern
Finland, and there is a risk that it will spread further
into areas populated by the Eurasian beaver. At present,
in south-west Finland, the two species are in contact in
western parts of Pirkanmaa Province. North American
beavers have also spread eastward from Finnish Lapland
into Murmansk region, Russia (Fyodorov & Krasovsky
2019).
Eurasian beavers have recently invaded Finnish Lapland
(Finland north of roughly 66°N) from Sweden though
the border Tornë watershed (Tornionjoki). Sixty-two bea-
vers were reintroduced, mainly as widely scattered pairs,
from 1960 to 1993 on Swedish tributaries (Mangi 2008).
They remained uncommon until the 1990s, when the rapid
increase phase of population development commenced.
Beavers are now strongly established on the lower and
middle Tornë in Finland and on the adjacent lower Kemi
(Kemijoki) watershed. A few groups are established on
the upper Ounas tributary of the River Kemi (Fig. 4).
The Kemi is the longest river in Finland, c. 550 km
for the main course. The watershed drains central and
southern Finnish Lapland from 66 to 68°N and a small
area of Russia (Fig. 6), an area of about 55000 km2. The
climate is harsh, but the topography is largely flat or
gently undulating. Rivers are tortuous and lakes abundant;
the amount of suitable habitat for beavers is very large.
More or less simultaneously, the North American beaver
has colonised the upper watershed in the east and south-
east, though established groups are widely scattered. Also,
there are, or appear to be, a few groups of North American
beavers remaining in the Tornë and Ounas rivers from
Fig. 4. Beaver distribution in Asia in 2020. Black = refugia where Eurasian beaver was never extinct. [Colour figure can be viewed at wileyonlinelibrary.com]
Population and distribution of beavers in Eurasia
D. J. Halley, A. P. Saveljev and F. Rosell
7
Mammal Review 51 (2021) 1–24 © 2020 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
Table1. Dates of extinction (extirpation), legal protection, reintroductions or translocations, and most recent population estimates for Eurasian beavers
Castor fiber by country.
Country Extirpation Protection
Reintroduction and/
or translocations
Most recent
population estimate Source/comments
Austria 1869 – 1970–90 7600 Kollar and Seiter (1990), Univ. für Bodenkultur Wien
Belarus Remnant 1922 1948 51100 National Statistical Committee of the Republic of
Belarus (2018)
Belgium 1848 – 1998–99 2200–2400 Dewas et al. (2012), www.bever werkg roep.be 2019
Bosnia and
Herzegovina
? ? 2006 140 Trbojević and Trbojević (2016)
Bulgaria 1750–1850 ? – – Boev and Spassov (2011)
China Remnant 1991 – 600 Chu and Jiang (2009), Jiang et al. (2016)
Croatia 1857? – 1996–98 10000 Grubesic et al. (2001), Kralj (2014), Cavric (2016),
Tomljanović et al. (2018)
Czech Republic Mid 18th
Century;
1876*
– 1800–10, 1991–92,
1996
>6000 Jitka Uhlikova pers. comm., Vorel et al. (2012), Vorel
and Korbelova (2016)
Denmark c.500 BC¶– 1999, 2009–11 216–252 Asbirk (1998), Elmeros (2017), Taidal (2018)
England 18th Century? – 2016† c. 150† Coles (2006), D. Gow pers. comm. (2019)
Estonia 1841 – 1957 18000 Timm, Estonian Environmental Information Centre
pers. comm., Estonian Hunter’s Association (2019),
Veeroja and Männil (2018)
Finland 1868 1868 1935–37, 1995 3300–4500‡ Lahti and Helminen (1969), Natural Resources
Institute Finland (Luke) (2019)
France Remnant 1909 1959–95 >14000 Dewas et al. (2012), ONCFS (2018)
Germany Remnant 1910 1936–40, 1966–89,
1999–2000
35000 Schwab et al. (1994), G. Schwab pers. comm. (2018)
Hungary 1865 – 1980–2006 14600–18300 Bajomi (2011), Čanády et al. (2016), Bajomi et al.
(2016)
Italy 1541 – proposed 1 Nolet (1996), Messagero Veneto 30/11/2018
Kazakhstan 1915 – 1963–86 5500 Saveljev (2005)
Latvia 1870s – 1927–52, 1975–84 100000–150000 Belova et al. (2016)
Liechtenstein ? ? – 50 Fasel (2018)
Lithuania 1938 – 1947–59 121000 A. Ulevicius pers. comm. (2019), Belova et al. (2016)
Luxembourg ? ? – c. 75 Herr et al. (2018)
Moldova ? ? – ? Status uncertain
Mongolia Remnant ? 1959–2002; 2012,
2018
800 Samiya (2013), Saveljev et al. (2015), Adiya et al.
(2015)
Netherlands 1826 – 1988–2000 2300–3800 Kurstjens and Niewold (2011), Dijkstra et al. (2018),
Dijkstra (2019)
Norway Remnant 1845 1925–32, 1952–65 >80000 Rosell and Pedersen (1999), Parker and Rosell (2003),
F. Rosell pers. comm. (2020)
Poland 1844 1923 1943–49, 1975–2000 124622 Janiszewski and Misiukiewicz (2012), Rozkrut (2018)
Portugal c. 1450 – – 0 Antunes (1989)
Romania 1824? – 1998–99 2145–2250 Ionescu et al. (2010), Pașca et al. (2018)
Russian
Federation
Remnant 1922 1927–33, 1934–41,
1946–2005
700000 Ognev (1963), Federal State Statistics Service, Russian
Research Institute of Game Management and Fur
Farming (2019); see text
North-West
Federal
District
152800§ Russian Fur Union (2016)
Central FD 153750 Russian Fur Union (2016)
Volga FD 168070 Russian Fur Union (2016)
South FD 7660 Russian Fur Union (2016)
Ural FD 58100 Russian Fur Union (2016)
Siberian FD 80780 Russian Fur Union (2016)
Far Eastern FD 800§ Russian Fur Union (2016)
(Continues)
D. J. Halley, A. P. Saveljev and F. Rosell
Population and distribution of beavers in Eurasia
8Mammal Review 51 (2021) 1–24 © 2021 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
an earlier introduction. Whether these are genuinely North
American beavers or Eurasian beavers settled at old North
American beaver sites is unclear. DNA testing is underway
(K. Kauhala, personal communication).
The scene seems set for rapid increase of both species,
eventually meeting along a front within the Kemi basin
somewhere in central Lapland. Castor canadensis is clas-
sified as an invasive species in Finland’s National Strategy
on Invasive Alien Species, so a logical strategy would be
to attempt to eliminate, or at least reduce, North American
beaver on the Kemi, to favour recolonisation by Eurasian
beaver (Parker et al. 2012). Strategic reintroductions of
Fig. 5. Minimum total Eurasian beaver Castor fiber population estimates 1998–2020. The sources are indicated. [Colour figure can be viewed at
wileyonlinelibrary.com]
Country Extirpation Protection
Reintroduction and/
or translocations
Most recent
population estimate Source/comments
Scotland 16th Century – 2009 c. 319–547 Coles (2006), Campbell-Palmer et al. (2018)
Serbia 1903? – 2003–4 240 Cirovíc pers. comm. (2012), Smeraldo et al. (2017)
Slovenia 1750? ? – 300–400 Grubešić pers. comm. Jursic et al. (2017)
Slovakia 1858 – 1995 7700–9600 Čanády et al. (2016)
Spain 17th Century 1980s 2003 450–650|| Cena et al (2004), Sáenz de Buruaga (2017)
Sweden 1871 1873 1922–39 130000 Hartman (1994a, 1995), Belova et al. (2016)
Switzerland 1820 – 1956–77 2800 C. Angst pers. comm. 2012, BAFU (2016)
Ukraine Remnant 1922 46000 Safonov and Pavlov 1973, Matsiboruk (2013a),
Matsiboruk (2013b)
Wales 16th Century – Feasibility study
completed
c. 15 Coles 2006; Jones pers. comm. (2009), D. Gow pers.
comm. (2019)
Minimum
Population
Estimate
1,487,000§
*1876 extirpation of animals descended from 1800–10 reintroduction in S Bohemia (Vorel & Korbelova (2016).
¶Based on subfossil remains. Philological evidence from place names suggests a remnant may have survived as late as the 11th Century.
†First licensed release, to River Otter; to supplement a population apparently deriving from escapes. Populations on other rivers are apparently the
result of escapes from fenced enclosures. Population figure is for wild-living beavers only.
‡Also c. 10300–19100 Castor canadensis. Source: https://www.luke.fi/en/natur al-resou rces/game-and-hunti ng/beave rs/.
§Population estimate includes some Castor canadensis; Russian North-west FD < 20000, Far East FD < 200.
||Navarra only, see text.
Table 1. (Continued)
Population and distribution of beavers in Eurasia
D. J. Halley, A. P. Saveljev and F. Rosell
9
Mammal Review 51 (2021) 1–24 © 2020 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
Eurasian beavers to sites in the Kemi basin would assist
this process.
This would be technically straightforward, and much
cheaper than managing a later situation resembling that
in south-west Finland. Finland is legally required to (at
least) contain the spread of North American beaver when
feasible. Article 19 of the European Union Regulation on
the Prevention and Management of the Introduction and
Fig. 6. Distribution of Eurasian beavers Castor fiber and North American beavers Castor canadensis in Finland in 2018. The catchment of the Kemi
watershed is indicated. Adapted with permission from LUKE (2019). [Colour figure can be viewed at wileyonlinelibrary.com]
D. J. Halley, A. P. Saveljev and F. Rosell
Population and distribution of beavers in Eurasia
10 Mammal Review 51 (2021) 1–24 © 2021 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
Spread of Invasive Alien Species states that measures must
be taken ‘aimed at the eradication, population control or
containment of a population of an invasive alien species’
(Genovesi & Shine 2003, European Union 2014). Human
social and regulatory factors are the main barrier to man-
agement (K. Kauhala, personal communication).
France
Beavers survived in very small numbers in the Rhone
delta, France. There have been 26 reintroductions (273
individuals) from this source within France (Dubrulle &
Catusse 2012). The most recent accounts of population
and distribution are Dewas et al. (2012), Dubrulle and
Catusse (2012) and ONCFS (2018). ONCFS (now Office
français de la biodiversité) publishes a regularly updated
distribution map (Appendix S7) online at http://carmen.
carme ncarto.fr/38/Castor.map.
The current population estimate for France is > 14000,
in effect unchanged from the 10–15000 reported by Halley
et al. (2012). A new population estimate based on a
2019 survey will be published in 2020 (ONCFS 2018)
and will be significantly higher. Range has extended sig-
nificantly on most occupied watersheds. In 2009,
10500 km of watercourse was permanently occupied; in
2018, 15000 km (ONCFS 2018); in 2019, 16500 km
(Yoann Bressan, Office français de la biodiversité, personal
communication). On much of the Rhone the population
is mature; some marginal sites have been abandoned
(Dewas et al. 2012).
Small populations are now established on the Saône and
Doubs (major northern tributaries of the Rhone) and on
the Garonne (84811 km2), ‘certainly’ to a 25 km stretch of
the Tarn tributary downstream of Albi, 55 km north-east
of Toulouse, and ‘probably’ to a 20 km reach above Rabastens,
a further 40 km downstream. These are below the hydro-
barrages on the upper Tarn, which until recently restricted
spread (ONCFS 2018). A population was recently discovered
on the lower Vère, a small side tributary of the Aveyron
tributary of the Garonne west of Mountauban (ONCFS
2017). Large-scale colonisation of both the Saône and Doubs,
and the Garonne above the barrage at Golfech (65 km
north-east of Toulouse), should occur over the next 20 years
(Dewas et al. 2012, ONCFS 2017). Colonisation of the city
of Lille and the Avesnois in Nord Pas de Calais, NW France,
was confirmed in 2020 (https://ofb.gouv.fr/actualites/le-castor-
deurope-de-retour-dans-le-departement-du-nord).
Eleven beavers from north-east France, and 101 from
throughout France, were genetically tested in 2011 and
2018, respectively. All were Castor fiber, and all except
one of Rhone stock. The exception was an animal tested
in 2018, descended from Elbe beavers, found on the Saar
in extreme north-eastern France (Bressan et al. 2018).
An adult beaver was filmed on the River Nive near
Ustaritz in south-west France in late 2018 (Onda news-
paper, 11 January 2019; https://www.ligury.com/reper e-un-
casto r-sur-les-bords/). It may have been from the Ebro,
which would involve a crossing of the (formidable) foothills
of the Pyrenees.
Germany
Beavers on the River Elbe, Germany, descend from the
refugium on that river system. The population in Bavaria,
now found throughout the state, is of highly mixed origin,
but not including Elbe beavers (see Halley & Rosell 2002).
Bavaria has been the source for most reintroductions
throughout Europe since the 1970s, including to the re-
mainder of Germany. The current population is estimated
at 35000.
Beavers are now found throughout most of eastern and
southern Germany, with strongly established disjunct popu-
lations in the west (Appendix S8; Stolz 2017). Rapid ex-
pansion in range, followed by rapid population increase,
will almost certainly take place in western Germany, and
into remaining unoccupied areas of the south and east,
over the next 2-3 decades.
A comprehensive website on beavers in Germany and central
Europe is available at http://www.biber manag ement.de/.
Greece
Government organisations have suggested a beaver rein-
troduction feasibility study in Greece (Alexandros
Karamanlidis, personal communication).
Hungary
Beavers immigrated to Hungary from Austria from the
1990s, along the River Danube (Boszér 2000). In 1996–2008,
more than 200 beavers were reintroduced in the areas of
Gemenc and Hanság, on the River Tisza (the main wa-
tershed of eastern Hungary, entering from Transcarpathian
Ukraine and exiting to Serbia) and on the River Dráva
(which forms part of the border with Croatia).
Reintroduction history is described by Bajomi (2011) and
Bajomi et al. (2016). Most were sourced from Bavaria.
Beavers are now found along the entire course of the
Hungarian Danube, and most of the Tisza and some of
its tributaries. The population is estimated at 14600–18300
(Čanády et al. 2016).
Italy
In 2018, a beaver settled on the Gaililz, a Danube head-
stream (via the Austrian Drava), at Tarvisio in extreme
Population and distribution of beavers in Eurasia
D. J. Halley, A. P. Saveljev and F. Rosell
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Mammal Review 51 (2021) 1–24 © 2020 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
north-east Italy, the first Italian record for 450 years
(Messagero Veneto newspaper, 30 November 2018). The
Alps are a formidable barrier to spread into the rest of
Italy, as for other populations established around the land
border of Italy.
Kazakhstan
Beavers were part of the Kazakh fauna until the early
20th Century. The modern population spread into the
lower Ural watershed from 1963, from reintroductions
upstream near Orenburg, Russia (Karagoyshin 2000). A
second population in eastern Kazakhstan descends from
migration and translocation from the Russian Altai in the
1980s (Berber 2008). In 1996, beavers were removed from
the Kazakh Red Data Book. The current range is an almost
continuous strip of northern Kazakhstan. Population and
distribution are increasing; hunting has been permitted
since 2009 (Baytanaev et al. 2012).
Latvia
Beavers are present throughout Latvia, as a result of re-
introductions from Norway and Russia. The population
estimate peaked at 89474 in 2009–10 and declined to 58000
by 2017–18 (Zemkopibas Ministrija 2018). Estimated popu-
lation size in 2016–17 was 58000 (State Forest Service
2018) but, according to expert opinion, the actual popula-
tion size could be as high as 150000 (J. Ozolins, cited in
Sjöberg & Belova 2020). See Lithuania for a likely cause
of the discrepancy.
Liechtenstein
Beavers spread from Switzerland in 2008. In 2017–18, the
population was estimated at 50 (Fasel 2018).
Lithuania
Beavers descended from reintroductions from Russia are
present throughout Lithuania. The official population es-
timate is 40600 (Lietuvos Respublikos Aplinkos ministerija
2017, Raskauskaite & Simkevicius 2017), but this is a
hunters’ association estimate, reported to the game and
wildlife authorities. Hunting associations (which have the
hunting rights) must pay landowners on a population basis
if they do not ensure the population is ‘optimal’. This
provides a motive for underestimating population size.
The real population appears to be roughly stable, with
local declines and increases observed, and is estimated at
c. 100000 (A. Ulevicius, personal communication) and
101265 (Sjöberg & Belova 2020).
Luxembourg
Herr et al. (2018) review population history and current
distribution of beavers in Luxembourg. Groups of North
American beavers, established in the early 21st Century,
apparently from zoo escapes in German Saarland, have
been removed. There are currently c. 20 established Eurasian
beaver territories, or about 75 individuals (Appendix S9),
mainly descended from immigrants from Belgium; but
also Germany and possibly France.
Mongolia
A small population of Sino-Mongolian beavers survived
on the Bulgan River in the extreme west of Mongolia
and neighbouring Xinjiang in China. Local translocations
of Bulgan beavers have taken place, to the Khovd (1959–85,
39 animals), the Tes (in 1985, 1988 and 2002, 37 animals),
and to Voronezh (four, in 1962; Stubbe & Dawaa 1983,
Samiya et al. 2012, Saveljev et al. 2015).
Native beavers are today found in three isolated popula-
tions: Bulgan, Khovd, and the Uvs Lake basin (includes
the Tes River and adjacent small rivers in Mongolia and
Russia). The total population is estimated at 600, of which
the Tes population is the largest (Samiya 2013, Saveljev
et al. 2015).
Fourteen beavers from Bavaria, Germany, and 27 from
Kirov, Russia, were brought to Ulaanbaatar, Mongolia, in
2012 (Samiya et al. 2012, Adiya et al. 2015), to improve
water retention in regional rivers, and 16 Kirov beavers
(9 males, 7 females) from seven families were released
on the Zaan (Tuul River tributary, Selenga basin). From
2012 to 2019, 38 beavers from a captive breeding facility
(containing Kirov and Bavarian animals) were released
into the wild on the Zaan and Tuul. The facility contained
44 individuals in 20 family groups in 2019 (S. Shar, per-
sonal communication). Further releases in north and east
Mongolia are planned.
Monitoring attempts have not produced useable estimates
of the wild-living population in Mongolia.
Netherlands
The current status of beavers in the Netherlands is reported
by Dijkstra (2019). The population is estimated at 3500.
Beavers continue to expand in both population and range,
by expansion from reintroductions, immigration from
Belgium (mainly along the River Maas), and from Germany
in the Drenthe Province. In 2012–14, the range increased
by 30% per year in terms of 5x5 km squares occupied.
In 2015–17, this slowed to 11% per year (Dijkstra et al.
2018). Distribution (Appendix S10) is mapped in the
D. J. Halley, A. P. Saveljev and F. Rosell
Population and distribution of beavers in Eurasia
12 Mammal Review 51 (2021) 1–24 © 2021 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
National Flora and Fauna Database at https://www.versp
reidi ngsat las.nl/8496057.
Norway
Beavers survived in Telemark in south-east Norway and
were reintroduced at numerous sites from the 1920s to
the 1990s (Rosell & Pedersen 1999). The species now
occupies the entire country south of Saltfjellet (an ocean-
edge tundra/ice cap plateau) on the Arctic Circle, and
east of the mountain chain dividing Atlantic from
Skagerrak watersheds south of Trondheim (Appendix
S11).
Populations reintroduced north of Saltfjellet in the 1960s
and 1970s at Rago National Park in Nordland, and in
the Porsanger/Tana region of Finnmark, are now extinct.
Occasional vagrants, probably from Sweden, are reported
in the area.
Four small populations have become established by
natural spread on Atlantic-draining rivers in the south-
west fjord region of Norway. This must have involved
overland travel across the watershed divide. In the long
term, beavers will probably establish themselves in pockets
of suitable habitat in much of fjordland Norway. Beavers
are also advancing slowly into the region along the coast,
both from the south and north. Colonisation patterns
indicate dispersal through brackish and salt water, especially
where it is sheltered (Halley et al. 2013).
In Norway, beavers are hunted as small game. Hunting
rights are owned by the landowner; there is no system
of ‘compensation’ for beaver impacts. This and that beavers
are not highly prized as a hunting object, in combination,
renders the species of low salience, underlining the large
human social factors involved in ‘wildlife-human conflicts’
(Parker & Rosell 2003). In consequence, there are no full-
time beaver managers in Norway and no funding for
monitoring. The population estimate (80000) is, in these
circumstances, an educated guess.
Poland
Beavers were widely reintroduced in Poland from the Soviet
Union, mainly from 1975, with internal translocations from
1990 to 2000. They are now found throughout Poland.
The population shows signs that it may be leaving the
rapid increase phase of development, from 500 animals in
1975 to 125000 in 2017. Figures in Rozkrut (2018) show
a levelling off of population in 2015–17. In the Vistula
Delta, where beavers reappeared in the mid-1990s, studies
indicate suitable habitat is now saturated and the popula-
tion stable (Zwolicki et al. 2019). While a longer series is
needed to confirm the trend, it is likely that populations
may decline moderately over the next 20 years.
A Polish website offering beaver management services claims
annual damage to private landowners of €6.6 million
(https://swiatrolnika.info/publicystyka/firma-bobry-odlawianie).
However, despite the 23% population increase since 2015,
there has been an 11% decrease in reported conflicts.
Ministry of Environment compensation payments totalled
€5192000 in 2017 (Wróbel & Krysztofiak-Kaniewska
2020). Wróbel and Krysztofiak-Kaniewska (2020) suggest
that the decrease in reported conflicts may be due to
landowners becoming used to beavers and developing
better management skills. Use of flow devices is now
widespread (Wróbel & Krysztofiak-Kaniewska 2020).
The Polish Union of Hunters does not want to hunt
beavers, apparently because the obligation to compensate
for damage would pass to them (Saveljev et al. 2020).
Nevertheless, looking ahead, Polish specialists have already
published a guide to the integrated use of beaver resources
and hunting products (Misiukiewicz 2018).
Romania
The most recent source on beavers in Romania is Pașca
et al. (2018). Reintroductions from Bavaria were carried
out from 1998 to 2003. Ninety-one beavers were released
in the Olt River, 56 in the Mureș and 35 in the Ialomița
(Ionescu et al. 2010). In 2014–17, populations were esti-
mated at 1565 on the Olt, 330 on the Mureș, and 214
on the Ialomița. In 2010, beavers, presumably from the
Ialomița, colonised the upper Danube Delta near Tulcea,
and later the main delta. In the north, beavers colonised
Maramureș in 2008, from the Hungarian Tisza via Ukraine
(Chiș 2015). There were six active territories in 2017
(double the 2015 figure), or c. 25–30 animals. (V. Chiș,
personal communication). The Romanian population is
estimated at 2145–2250 (Pașca et al. 2018). Signs of va-
grants have also been recorded on the Someș and Criș
Rivers of western Transylvania, tributaries of the Tisza;
colonisation can be expected in the short to medium term.
Russian Federation
Although greatly reduced in numbers and very patchily
distributed, in the 19th Century beavers survived in the
Russian Federation in the forest zone at least as far east
as the easternmost tributaries of the River Lena, and along
many rivers in the steppe zone (Ognev 1963). It has
been suggested that beavers did not live in rivers draining
to the Sea of Okhotsk or the Pacific, except the upper
Amur (Ognev 1963). However, beaver remains at human
sites dated from 800 to 1500 years ago in the Ussuri
headwaters about 50 km north of modern Vladivostok
(Kuzmin 1995, 1997) indicate they were naturally present
in that region.
Population and distribution of beavers in Eurasia
D. J. Halley, A. P. Saveljev and F. Rosell
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Mammal Review 51 (2021) 1–24 © 2020 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
Population and distribution are expanding. A map is
available at http://rusmam.ru/atlas/ map. While previously,
range expansion was most active in the mountains of
southern Siberia (Saveljev 2003), recent major expansion
has shifted to southern European Russia, and the northern
periphery in Siberia.
In European Russia, beavers have expanded down the
Volga to Volgograd. Range has significantly expanded in
the Rostov region along the River Don, to its mouth.
Most inhabit the northern Rostov region, on the Seversky
Donets, Kalitva, and Chir, and the middle Don. Population
increases are expected on the lower Don, as well as colo-
nisation of rivers around the Sea of Azov. Previously,
beavers swimming in the sea were recorded only in the
Dnieper estuary (Igor Sheygas, personal communication),
but dispersing beavers have recently been recorded in the
Sea of Azov. Migrants emerge from the mouth of the
Don and have settled south along the coast (Valery Stakheev,
personal communication).
The Don River delta and Tsimlyansk area may also be
colonised by beavers from Ukraine (see below). The Rostov
region population is estimated at >2300 (Stakheev et al.
2018). Beavers have also spread to the northern part of
Kalmykia (a typical steppe region between the Rivers Don
and Volga).
Beavers have begun to settle in large cities (St. Petersburg,
Kazan, Kirov and others). At least 20 beaver territories
are recorded in Moscow (see http://rusmam.ru).
In the western Urals, beavers have settled almost to
the mountain headwaters of the Rivers Pechora, Ilych and
Vishera. Permanent settlement on the Vishera River can
be found up to 555 m above sea level, near the transition
to alpine tundra (Saveljev et al. 2011).
Large-scale expansion is occurring in Siberia. Beavers
from the Ob have penetrated northwards to the Taz basin
in recent years. Average annual movement of the expan-
sion front was about 40 km per year (Yan Kizhevatov,
personal communication).
On the Yenisei watershed, the northernmost stable
population is found in the Yeloguy. Beavers are regular
in the lower reaches of the Podkamennaya Tunguska. To
the south, the entire middle and upper Yenisei basin is
now inhabited, with increasing density upstream, both in
protected and in hunting areas (Trenkov 2015). Beavers
also live in the upper Angara in Irkutsk Region, and in
Buryatia. An isolated population of Belarusian origin has
existed in the Amur basin near Khabarovsk for 55 years;
population and range are increasing. In contrast, the nearby
population of Castor canadensis on the Obor is in decline
(Oleinikov 2013).
In northern European Russia, range dynamics are less
active. Interesting changes have occurred in the contact
zone of the two species. Eurasian beavers have displaced
North American beavers in areas of southern Karelia in-
habited by Castor canadensis since their release there in
the late 1960s. The closest distance between colonies of
different species is 10 km. Conversely, in north-eastern
Karelia (Kemsky District), North American beavers have
penetrated 70 km into Arkhangelsk region and are colo-
nising areas inhabited by Eurasian beavers (Danilov &
Fyodorov 2016). Castor canadensis from Finnish Lapland
are moving east into Murmansk region (Kataev 2018,
Fyodorov & Krasovsky 2019).
Between 2005 (Saveljev 2005) and 2015, the number
of beavers in Russia increased annually, although growth
rates gradually decreased. Borisov (2011) estimated popula-
tions as 528900 in 2008, 611800 in 2009, and 628300 in
2010. In 2015, the population was estimated at 622000
(Russian Fur Union 2016). See Table 1 for a breakdown
by Federal District.
According to the Russian Research Institute of Game
Management and Fur Farming, the population of both
beaver species together reached 696070 in 2018. The Federal
State Statistics Service (https://www.gks.ru/folde r/11194)
reported 24342 beavers harvested in the hunting season
2017–18.
Given the general trend, and that the number of North
American beavers in the north-western regions does not
exceed 20000, and in the Russian Far East no more than
200, the total population of the Eurasian beaver in Russia
in 2020 can be estimated as at least 700000, about half
of the world population.
Scotland
Detailed investigation of reintroduction began in Scotland
in 1993, resulting ultimately in a ‘trial’ reintroduction of
Norwegian beavers on the Knapdale Peninsula in western
Scotland from 2009, at a site with strong natural barriers
to spread. In the same year, however, it became clear
that a wild population was established on the Rivers Tay
and Earn, the largest watershed in Scotland. The source
appears to have been escapes from enclosures, and beavers
are of Bavarian origin (Campbell-Palmer et al. 2020). The
first beaver observed and photographed in the wild was
at the Tay/Earn confluence in April 2001 (Hugh Chalmers,
personal communication). However, the territory at
Rannoch/Dunalastair on the upper river (Territory 49 in
Appendix S12), separated from the main population by
three large hydroelectric dams along 25 km of river unoc-
cupied by beavers despite much high-quality habitat, is
unlikely to have resulted from natural spread from the
lower river, where all fenced enclosures were located
(Campbell et al. 2012).
Entrenched controversy surrounding land use in Scotland
has strongly influenced both the official beaver
D. J. Halley, A. P. Saveljev and F. Rosell
Population and distribution of beavers in Eurasia
14 Mammal Review 51 (2021) 1–24 © 2021 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
reintroduction and management issues. It has also led to
much detailed research and review on various aspects of
beaver biology, particularly on issues of local controversy
such as beaver damming and migratory fish (Kemp et al.
2012, Beaver-Salmonid Working Group 2015). There has
also been comprehensive monitoring (Campbell-Palmer et
al. 2018); see also Gaywood (2018) for review.
The Knapdale population remains restricted in range
and numbers. In 2019, it was augmented by seven animals
translocated from the Tay (Scottish Natural Heritage 2020).
The Tay and Earn population has continued to expand
in range, and especially in population (Appendix S12),
despite 82% of individuals being as closely related as first
cousins, presumably due to small numbers of founding
animals (Cambell-Palmer et al. 2020), and significant
numbers being legally killed by landowners, as they were
unprotected. Beavers have also colonised the Forth wa-
tershed to the south, where they are widely but thinly
spread in high-quality habitat (Appendix S12). The wa-
tershed is small, and considerable growth in population
can be expected in the near future. The 2017–18 popula-
tion on the Tay/Earn and Forth was estimated at 114
active territories, or 319–547 individuals (Campbell-Palmer
et al. 2018).
A small population in Beauly, near Inverness, descended
from escapes, remains present despite the removal of five
individuals in 2018. Tay beavers have recently spread west
to rivers north of Knapdale (R. Campbell-Palmer, G. Dowse,
Scottish Beavers, personal communications).
Beavers were given European Protected Species status
in Scotland from 1 May 2019, and “the species will be
allowed to expand its range naturally” (Scottish Natural
Heritage, press release, February 2019). From that date
to 31 December 2019, 87 beavers were killed under gov-
ernment licence (Scottish Natural Heritage 2020).
Serbia
Seventy-five beavers from Bavaria were reintroduced to
Serbia, at Obedska Bara and Zasavica nature reserves on
the lower Sava River, in 2004–2005. Both have established
local populations. Smeraldo et al. (2017) report spread
upstream to the Bosnia–Croatia border and to the lower
Drina on the Bosnia–Serbia border. There appears to have
been little downstream spread into the Danube, though
habitat and hydrology appear suitable for transit and set-
tlement; possibly Belgrade city (at the Sava-Danube con-
fluence) has hindered spread in that direction. In recent
years, the species has spread into northern Vojvodina from
Hungary along the Tisza (Appendix S13). From 2004–2013,
expansion of range was very rapid, 70.9 ± 12.8 km/year
(mean ± standard deviation, n = 10; Smeraldo et al. 2017),
typical of the early expansion phase on large river systems
(Hartman 1995, Fustec et al. 2001, Halley & Rosell 2002).
The population is estimated at c. 240. Rapid increase in
population and range can be expected in the next
20–30 years.
Slovakia
Recent history and status of beavers in Slovakia are re-
viewed by Čanády et al. (2016). Slovakian rivers drain
southwards to the Danube in, or on the border with,
Hungary. Beavers immigrated to Slovakia along the Danube
from Austria from 1977 and from Poland to north-east
Slovakia from 1993 (Valachovič 2012). Populations are
concentrated in the west and north-east, with recent es-
tablishment from the Hungarian Tisza on its Hornád
tributary in south-east Slovenia (Appendix S14). Central
Slovakia remains uncolonised, but contains much suitable
habitat. The population is estimated at 7700–9600
(Valachovič 2012).
Slovenia
Beavers from the Croatian reintroduction reached the Krka
tributary of the River Sava, Slovenia, in 1998 (Vochl &
Halley 2017, Jursic et al. 2017). Later, beavers entered the
southern Dravinja (Drava) river from Croatia (downstream)
and the north of the same river from Austria (upstream;
Deberšek 2012). Hydro-barrages have so far prevented
colonisation of the middle course. Since 2003 beavers have
colonised the whole of the Slovene Mura, a Drava tribu-
tary, from Croatia (Deberšek 2012). The national popula-
tion was estimated in 2015 as “at least 60 families with
300 to 400 individuals” (Ministry of Environment, quoted
in Dnevnik newspaper, 29 March 2018) and “70 families”
(Slovenske Novice newspaper, 10 April 2018). However, a
detailed survey of the Krka estimated the population on
that river alone at 50 active territories, 168–392 individuals
(Jursic et al. 2017).
Spain
Eighteen individual beavers of Bavarian origin were released
in Spain, near the confluence of the Ebro and its Aragon
River tributary in 2003 (Cena et al. 2004). The release
was unofficial, and Spanish authorities obtained a written
derogation from the European Union Habitats Directive
which allowed them to attempt extermination (albeit on
the incorrect grounds that the species was ‘outside its
natural distribution’ on the Ebro).
The issues both of the release and the attempts to
remove the animals generated considerable heat, but
little light on population status. The political geography
of the Ebro is complex, and the environment is the
Population and distribution of beavers in Eurasia
D. J. Halley, A. P. Saveljev and F. Rosell
15
Mammal Review 51 (2021) 1–24 © 2020 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
responsibility of the regions. Information obtained by
conservation groups through Freedom of Information
laws revealed that in La Rioja, 26 males and eight fe-
males were trapped in 2010, in Navarra 20 males and
16 females in 2008–2009, and in Aragon 10 males and
five females (all older than three years old) in 2009–2010,
using Bailey live traps and humane snares. A male in
his second year was captured by the firemen of Zaragoza
during the same period. The reason for the bias in the
sex ratio is not clear. Later, a similar request to the
European Commission revealed these figures were in-
complete: from 2008–2017, 102 beavers were trapped
in La Rioja, 83 in Navarra and 31 in Aragon (total 216;
European Commission Environment Directorate 2018,
Annexe, Echegaray et al. 2018).
The Ebro River basin contains a great deal of high-
quality habitat, in which beavers can live unobtrusively.
Trapping never extended to Euskadi (the Basque country),
in which beavers were already present. As predicted (see
http://www.iberi anatu re.com/spain blog/tag/beave rs-in-
spain/), the trapping attempt failed, and little attempt was
made after 2014 (16 animals trapped 2015–17, Echegaray
et al. 2018). The environmental economics journal Ballena
Blanca (No 6, April 2016) reported 100 individuals trapped
(an underestimate based on then released figures) at a
total cost of €131000. The population in Navarra alone
was estimated in 2014 as 450–650 (Government of Navarra
2015, unpublished report). If this is correct, the popula-
tion on the entire Ebro system must now be in excess
of 1000 individuals.
The main text of the European Commission Environment
Directorate (2018) letter reversed the European Union’s
position and stated beavers were a “historically autochthonous
and renaturalised species in Spain”, and that Spain “must
adopt the necessary actions to comply with the provisions
of the (Habitats) Directive”, legally protecting the species.
This decision is not as yet integrated into regional law.
Distribution in Spain (Appendix S15) is better known
than population. Beavers are now found from Miranda de
Ebro to Caspe on the main river, a straight-line distance
of over 300 km through which the river meanders strongly.
Beavers are established throughout the main Ega, Arga,
Irati and Aragon tributaries and their side streams in Navarra
(G. Berasategui, personal communication) and Euskadi
(Sáenz de Buruaga 2017). Newspaper reports, trapping loca-
tions (Echegaray et al. 2018, Fig. 2), and Internet videos
indicate beavers are also present on the Jalon (as far up-
stream as Arcos de Jalon), Alama, Cidaco, Iregua, Najarilla,
and Cicados tributaries. Signs of dispersing individuals have
been noted in several places on the lower River Ebro in
Catalonia. Genetic studies indicate the population is of
mixed genetic origin (Põdra & Aguilar Gómez 2015).
Sweden
Beaver reintroductions in Sweden commenced in the 1920s
and were widespread except in the south (Hartman 1994a,
1994b, 1995). Recent expansion includes colonisation of
the region around Uppsala, and the lower Tornë watershed
on the border with Finland, the latter the result of many
but mostly very small (one pair) reintroductions, 1960–
1993, on the Swedish side of the watershed (Mangi 2008).
Range expansion on the southern margins has been slow.
Beavers now occupy the whole of Sweden apart from the
far north (roughly, north of 67°N) and the south (roughly,
south of 58°N); the population is estimated at 130000
(Belova et al. 2016).
A searchable mapping database of the Swedish distribu-
tion is available (Shah & Coulson 2019); however, the
range mapped (largely through citizen science reports) is
an underestimate, particularly in the sparsely inhabited
north, where there is an observer bias near towns with
academic institutions (G. Hartman, personal
communication).
Switzerland
Online maps of beaver distribution in Switzerland are
available at https://lepus.unine.ch/carto/ index.php?nuesp
=70807 (Appendix S16), with a comprehensive website
at http://www.cscf.ch/cscf/home/biber fachs telle.html
Minnig et al. (2016) provide a detailed account of re-
introduction history, 141 individuals at 30 sites in 1956–77.
Population was estimated at 2800 in 2015 (BAFU 2016).
Beavers are now distributed widely on the Rhine and
Rhone watersheds, with recent settlement on the Inn
(Danube basin) from populations in Austria.
Ukraine
In the late 1930s, fewer than 100 Eurasian beavers survived
in the Pripet Marshes. In the Rovno region, there was a
colony of North American beavers brought from Poznań,
Poland, in 1933 and 1934, but by the mid-1950s, this
population had disappeared (Marin 1954). All beavers in
Ukraine today are Castor fiber.
20th-Century restoration is well documented (Safonov
& Pavlov 1973). Recent expansion has been rapid. From
2001 to 2010, the number of beavers in Ukraine increased
by more than three times and in some areas up to 7.3
times (Matsiboruk 2013a). Average annual population
growth was 24% (Matsiboruk 2013b). Beavers have begun
to colonise both eastern Ukraine (Tokarsky 2009,
Brusentsova & Ukrainskiy 2015) and southern Ukraine
(Volokh 2011).
D. J. Halley, A. P. Saveljev and F. Rosell
Population and distribution of beavers in Eurasia
16 Mammal Review 51 (2021) 1–24 © 2021 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
The beaver’s geographic range now occupies half of
Ukraine, including areas of intensive human activity
(Tokarsky et al. 2012). By 2011, the population was close
to 50000 (official statistics have not been published since
then).
The population in Transcarpathian Ukraine, derived
from the Hungarian Tisza reintroduction, is in rapid growth.
Beavers reached the region in 2003 and doubled in popu-
lation from 25 to 50 territories from 2009 to 2012 (Bashta
& Potish 2012), with further expansion later (Barkasi 2016).
Populations on the upper Dniester, on the eastern slope
of the Ukrainian Carpathians, were expanding in the same
period (Barkasi 2016).
Recent summers in Ukraine have been very arid, and
the winter of 2019/20 was snowless. This affected habitat
quality in beaver-inhabited rivers. Predation patterns have
also changed: in the Chernobyl Exclusion Zone, wolf Canis
lupus excrement was formerly dominated by the remains
of wild boar Sus scrofa, but now it is almost entirely
composed of beaver hair (V. Smagol, Institute of Zoology,
NAS Ukraine, personal communication).
Wales
The history of beavers in Wales is reviewed by Coles
(2019). Reintroduction was assessed as feasible in 2009
(Halley et al. 2009, Jones et al. 2011). There were four
known fenced populations in 2018 (Swaile et al. 2018),
with field signs in the wild on the River Dyfi in west
Wales; beaver signs are widespread on the River Wye on
the English border, though a 2018–19 survey found no
strong evidence of beavers living in established territories
(R. Campbell-Palmer, A. Leow-Dyke, personal communica-
tion). Population size is unknown.
POPULATION DEVELOPMENT
Beaver populations have continued to spread and grow
in size, confirming the prediction (Halley & Rosell 2002)
that the species will, within a few decades, be a fairly
common animal throughout most of its former range.
The current ‘minimum population estimate’ is 1479863
(which can be rounded as 1.5 million), 3.5 times the 1998
estimate (Nolet & Rosell 1998), and 2.5 times the 2002
estimate (Halley & Rosell 2002), using the same methods
of adding together the estimates for each country and
using the lower limit where a range is given. This is not
meant as anything other than a general guide.
Population development during recolonisation was re-
viewed by Halley and Rosell (2002). Developments since
have followed the same general pattern (e.g. John et al.
2010, Bártak et al. 2013, Zwolicki et al. 2019): colonisa-
tion of new watersheds by natural spread or reintroduction;
a period of relatively slow population growth, but rapid
range extension, followed by a phase of rapid population
increase; then a period of population decline as habitat
not capable of supporting beavers permanently is inhabited
and temporarily exhausted; and finally, rough stability.
The size of the watershed influences the length of these
stages, which are shorter in smaller watersheds; as do hu-
man interventions, in particular hunting and the pattern
of hunting (Parker & Rosell 2003, 2012).
In much of European Russia, Belarus, Ukraine, Poland,
Latvia, and Lithuania, populations appear to be nearing
maturity, with increases peaking in Poland and declines
reported in Belarus according to official statistics.
However, these trends are general, and the accuracy of
the statistics and the potential influence of biasing fac-
tors are open to question. Nevertheless, there is a general
consistency across the region which indicates that the
period of rapid population growth has probably now
ended.
In the Nordic countries, range expansion has slowed
in recent years (though not stopped), and the popula-
tion is mature in many areas. The main exception is
Finnish Lapland, currently under invasion from the west
by Castor fiber and from the south and east by Castor
canadensis (Fig. 4). In Norway, reintroduced populations
of Castor fiber north of the Arctic Circle are now ap-
parently extinct. Habitat patches are in general small
and, except in Finnmark, the terrain is very rugged,
inhibiting dispersal. At present, the northern limit of
both Castor fiber and Castor canadensis coincides roughly
with 67°N all the way from the Norwegian Sea to the
White Sea, even the populations of both species colonis-
ing the Kemi watershed in Finnish Lapland are mostly
south of this limit or very close to it. The only estab-
lished population to the north is in central Murmansk
Oblast at about 68°30′N, the status of which is little
known.
Castor canadensis is present to the shore of the Arctic
Ocean on the Mackenzie Delta, Canada, and in the ad-
jacent Alaskan north slope at 69°N (Tape et al. 2018), in
a winter climate much more severe that similar latitudes
in the Gulf-Stream influenced Nordics. In climatically
modern times (subfossils dated to c. 1350 before present),
beavers occurred to at least 70°N at Varanger in extreme
north-east Norway (Horn et al. 2014). Therefore, it seems
unlikely that climate is limiting beaver populations in the
north. The current populations all derive from refugia
much further south and have limited genetic diversity,
which may influence their ability to adapt to the extreme
conditions of the Arctic. However, the apparent pattern
may be a temporary effect of reintroduction history. The
Kemi watershed extends through most of Finnish Lapland
from 65°30N to 68°30N in largely flat terrain, with no
Population and distribution of beavers in Eurasia
D. J. Halley, A. P. Saveljev and F. Rosell
17
Mammal Review 51 (2021) 1–24 © 2020 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
barriers to dispersal (Fig. 6), so whether there is a real
climatic effect limiting northern distribution at around
67°N will soon become evident.
In the south, the Mediterranean Sea forms a natural
southern limit to the range in the west; it has formed an
effective barrier to most mammal dispersal for at least
5.5 million years (Groves & DiCastri 1991). Beavers for-
merly occurred in steppe and desert regions south to the
Tigris/Euphrates (Legge & Rowley-Conwy 1986), where
rivers flowing in from the north provided a dispersal route
and riparian vegetation permitted. River systems populated
by crocodiles or alligators – north to the Yangtze, Indian
subcontinent, and Nile – would presumably be unsuitable
for beavers.
INTERSPECIFIC COMPETITION
Differences in chromosome number (Castor fiber 48, Castor
canadensis 40), anal gland secretion differences, failed
crossbreeding attempts, and lack of observations of hybrids
in the wild all confirm that Castor fiber and Castor canadensis
are distinct species which cannot hybridise (Lavrov & Orlov
1973, Lavrov 1983, Rosell & Sun 1999).
Because of the early history of Castor fiber and Castor
canadensis in Finland and north-west Russia, it has some-
times been assumed that the relationship is one of straight-
forward dominance of canadensis over fiber. Recent data
suggest that this is an oversimplification, without identifying
a general pattern which would allow prediction of the
outcome. In some places, such as France and Luxembourg,
wild-living Castor canadensis populations have been re-
moved (Dewas et al. 2012, Herr et al. 2018). However,
Castor canadensis were also introduced in the Styr River
(Dnieper watershed) in north-west Ukraine in 1924 and
to East Prussia (now Poland) in 1926. Beavers of unknown
origin were also released here in 1942–43 (Panfil 1971)
and four Voronezh Castor fiber in 1961 (Klarowski 1983).
In 1979, a survey revealed that all animals in the region
were now Castor fiber (Zurowski 1980, cited in Saveljev
1989). In 1933–34, seven North American beavers were
released in the Rovno region, then in Poland (now in
Ukraine), and survived to 1956 but then died out (Dezhkin
1960). A similar decline in the Castor canadensis colony
in the Russian Far East (see above) is currently evident.
In Austria, 12 individuals of Castor canadensis were rein-
troduced, along with 40 Eurasian beavers, in the 1980s
(Sieber 2000). In each of these cases, canadensis has dis-
appeared, apparently through intraspecific competition with
fiber in the latter case at least (Sieber 2000).
The species meet at the eastern and western edges of
the Finnish – north-west Russian range of Castor canadensis.
At present, fiber is slowly losing ground to canadensis in
south-west Finland (LUKE 2019), and on the line of
contact between the White Sea and Lake Onega, but
canadensis has lost ground to fiber by c. 50 km on the
Karelian isthmus north of St. Petersburg (Saveljev 1989,
Danilov et al. 2011, Danilov & Fyodorov 2015, 2016).
We agree with Danilov and Fyodorov (2015, 2016) that
the factors which can ‘tip the balance’ are likely to be
complex and may include local biotic conditions and the
provenance and genetic diversity of founder populations.
The results of interspecific competition are also likely to
be influenced by the relative sizes of each population,
and so by the number of dispersers, once beavers have
spread throughout a river system and begin to compete
for space (Parker et al. 2012).
For management, a policy of active preference for Castor
fiber over Castor canadensis, especially where populations
are not yet ‘consolidated’ (such as on the Kemi, see Fig. 6
and section on Finland), is clearly preferable, rather than
hoping that fiber will prove to be the dominant species.
European Union member states are required to extermi-
nate, control or contain North American beaver and other
invasive species (European Union 2014).
BEAVERS IN THE MID-21ST CENTURY
Recolonisation of the beaver’s former range and, to a
lesser extent, re-establishment of the population in Europe
north and east of Poland–Ukraine inclusive is, with excep-
tions, substantially complete; and within a few decades it
will be complete. In Fenno-Scandia, spread into southern
Sweden, western Norway, and north of the Arctic Circle
can be expected.
In contrast, in most of continental Europe west of
Poland – Ukraine, and in Great Britain, populations
are in the early colonisation or rapid increase phases,
though they are at or near maturity in some regions
such as Bavaria and the lower Rhone. Both range and
population size will increase rapidly in this region in
coming decades, roughly one third of the land mass
of Europe with well over two thirds of its human
population.
Beavers remain absent from most of their former range
in southern Europe – Portugal, Spain excepting the Ebro,
Italy, and the Balkans from Bulgaria – Montenegro
southwards.
In Asia, there are extensive regions of Russia, especially
eastern Siberia, where beavers remain absent; scope for
further increases in range and population is correspond-
ingly large. Beavers of Voronezh/Belarus origin released
in Siberia are now in contact with native populations in
Western Siberia (Castor fiber pohlei) and the upper Yenisei
(Castor fiber tuvinicus). Management may be necessary if
maintenance of unmodified forms of the two autochtho-
nous gene pools is to be maintained.
D. J. Halley, A. P. Saveljev and F. Rosell
Population and distribution of beavers in Eurasia
18 Mammal Review 51 (2021) 1–24 © 2021 The Authors. Mammal Review published by Mammal Society and John Wiley & Sons Ltd.
The Danube basin is the world’s most international
watershed, draining part or all of 19 countries. Thirty
years ago, beavers were confined to the upper reaches
from Bavaria to Vienna. As a result of reintroductions
and natural spread, the species is now present and rapidly
increasing on the main river as far as the Hungarian–
Serbian border near Mohacs, and on the main tributaries
Morava, Tisza, Sava, Drava, and Mures. There are no
serious barriers to further spread on the Danube basin
above the Iron Gates barrages, on the Serbia–Romania
border about 150 km south-east of Belgrade. There are
many rapidly expanding beaver populations, increasingly
linked. Downstream of the Iron Gates, the Olt and Ialomița
populations are also in rapid expansion, and a population
is now established in the Danube Delta. Populations are
relatively small at present, about 1800 animals in 2017
(Pașca et al. 2018), and the area of unoccupied habitat
is very large. Absent further reintroductions, it will take
rather longer for populations in the lower basin to expand
throughout, but, as with the upper basin, there are few
barriers to spread.
The western extremity of the North European Plain
– northern France, Benelux, north-west Germany and
England – is one of the most densely populated, human-
modified regions in the world. The terrain is flat or low
relief. Beaver populations are now widely established in
the region, and the period of rapid population increase
is under way or about to commence. Management is likely
to become an increasingly salient issue in coming decades.
Other than in the Netherlands, there is little sign at pre-
sent that it will be other than reactive.
“How will the increasing beaver populations across
Europe, and their associated impacts on flow regimes,
water quality and biodiversity, affect river catchment res-
toration?” was recently identified as a ‘priority question’
for landscape restoration in Europe (Ockendon et al. 2018).
Understanding, adapting to, and utilising these impacts
should be a priority for river catchment management in
general. Attention to this and to framing public debate,
on the basis of the detailed information and experience
already available (Thompson et al. in press), would be
both wise and cost-effective. As most large watersheds,
and most beaver populations, in central and western Europe
are international, European Union mechanisms for research
and development of management methods would perhaps
be most appropriate.
ACKNOWLEDGEMENTS
We are indebted to the many individuals who have con-
tributed information or sources to our ongoing enquiries.
Work was in part supported by the Russian Science
Foundation (project no. 18-14-00093).
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SUPPORTING INFORMATION
Additional supporting information may be found in the
online version of this article at the publisher’s web-site.
Appendix S1. Beaver distribution in Austria in 2012.
Appendix S2. Beaver distribution in Belgium in 2016.
Appendix S3. Beaver distribution in Bosnia & Herzegovina
in 2015.
Appendix S4. Beaver distribution in the Czech Republic
in 2015.
Appendix S5. Beaver distribution in Jylland, Denmark in
2017.
Appendix S6. Beaver distribution in England and Wales
in 2018.
Appendix S7. Beaver distribution in France in 2019.
Appendix S8. Beaver distribution in Germany in 2017.
Appendix S9. Beaver distribution in Luxembourg and
adjacent regions.
Appendix S10. Beaver distribution in the Netherlands in
2017–19.
Appendix S11. Distribution of beavers in Norway in 2019.
Appendix S12. Distribution of beaver territories in Scotland,
Tay and Forth watersheds.
Appendix S13. Beaver distribution in Serbia in 2015.
Appendix S14. Beaver distribution in Slovenia in 2015.
Appendix S15. Distribution of beavers in Spain (Ebro
watershed) in 2019.
Appendix S16. Distribution of beavers in Switzerland in 2019.