Beavers are widely recognised as a keystone species which play a pivotal role in riparian ecology. Their tree felling and dam building behaviours coupled with a suite of other activities create a wealth of living opportunities that are exploited by a range of other species. Numerous scientific studies demonstrate that beaver-generated living environments that are much richer in terms of both biodiversity and biomass than wetland environments from which they are absent. Emerging contemporary studies indicate clearly that the landscapes they create can afford sustainable, cost-effective remedies for water retention, flood alleviation, silt and chemical capture. The authors of this handbook are all beaver experts and together they have a broad range of scientific knowledge and practical experience regarding the ecology, captive husbandry, veterinary science, pathology, reintroduction and management of beavers in both continental Europe and Britain.
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About the Author
Derek Gow is a freelance ecologist who has worked with beavers and water voles in Britain for over 20 years. He has advised Natural England and Countryside Council for Wales on beaver reintroduction
Frank Rosell is a renowned beaver ecologist, publishing more than 80 scientific papers with peer review. He is professor in behaviour ecology at Telemark University College, Norway, and was part of the advisory board of the Scottish Beaver Trial.
Read an Excerpt
Beavers (i.e. the Eurasian beaver, Castor fiber, and the North American – sometimes referred to as Canadian – beaver, C. canadensis) are unique mammals that often capture people's fascination. These are large rodents, with specialised features such as their flat scaly tails, and distinctive behaviours including tree-felling and dam-building. Few other animals, apart from humans, have the ability to modify so drastically their surrounding environments. Beavers play a key role in wetland ecology and species biodiversity, providing vital ecosystem services including habitat creation, water management and quality improvement, and sediment retention. At the same time, these beaver activities can also present real challenges for land and wildlife managers.
The history of the Eurasian beaver represents an important case study for conservation and reintroduction programmes. By the late 19th century, the once widespread Eurasian beaver was reduced to a handful of relict populations in fragmented refugia across Europe, in which potentially 1,000–2,000 individuals survived (Nolet and Rosell 1998). As beaver populations dwindled, so did the understanding of living with this species pass from common knowledge. In the beavers' absence, landscapes continued to be altered by humans, and riparian environments in particular were engineered to suit agricultural and industrial needs. By the early 20th century, naturalists tended erroneously to believe that beavers were solely a species found in 'open woods alongside rivers, old river beds and lakes' (van den Brink 1967) and limited in distribution by habitat suitability.
Since then, Eurasian beavers have been restored to much of their former native range through proactive reintroductions and translocations (Halley et al. 2012). Contemporary experience of expanding beaver populations across Europe and North America demonstrates clearly that beavers can readily modify even heavily engineered landscapes to suit their own ecological requirements. The two extant beaver species, the Eurasian and the North American, inhabit wetlands and water bodies from north of the Arctic Circle, where they can endure five months of darkness and ice, to the everglades of subtropical Florida. The dry, arid environment of the Ulungaur watershed in Mongolia contains one of the last remaining Far Eastern beaver populations. Intensively utilised, cultural landscapes dominated by agricultural production with amenity woodlands, recreational areas and engineered water bodies are relatively unchallenging environments for beavers. Although it has been well demonstrated that environmental factors such as topography, hydrology and vegetation influence beaver distribution (Schwab et al. 1992; Rosenau 2003; Rosell et al. 2005), they are clearly a much more adaptive species than was initially believed.
The Eurasian beaver is a well-studied species capable of providing biodiversity and economic benefits through its natural activities. Its restoration is considered internationally to be a clear conservation success (Halley and Rosell 2002). While initially some countries (such as Finland and Russia) restored beavers to support a commercial fur trade, the majority of recent reintroductions have been implemented for nature conservation purposes. This emphasis has been prompted by a greater awareness of the ecological benefits which accrue from the presence of beavers.
The return of the beaver through a combination of reintroductions and natural recolonisation has often been viewed as a novel phenomenon. When beaver populations initially re-establish, the physical impact of their activities is often confined to a small group of land-users such as farmers, foresters or water authorities (Siemer et al. 2013). As beaver populations increase, the novelty of their presence can be replaced by hostility from wider elements of society when more visible impacts occur such as the felling of specimen trees in public parks, orchards or gardens. It is inevitable that a process whereby people 'rediscover' what it means to live with beavers will become a critical component of coexistence. Understanding, tolerance and a willingness to manage undesirable aspects of beaver activity competently will also be of fundamental importance.
1.1 Aims and purpose of this handbook
This handbook considers a broad range of issues which are likely to arise over time as beavers are re-established, particularly with respect to British landscapes, but also elsewhere in Europe. It affords a practical overview of the implications of beaver restoration and the management requirements. Most of the information presented here addresses the experiences gained from beaver restoration in Europe, but draws from practical experiences in North America where beaver populations have also recovered. The handbook describes the animals' field signs, lifestyle, their effects on the environment and appropriate mitigation techniques, as supposed to any wider-scale, long-term management strategy at a national level. In relation to Britain, the Eurasian beaver has not yet been formally reintroduced despite being an Annex IV species on the European Habitats Directive, although licensed trial reintroductions have occurred in Scotland (Scottish Beaver Trial) and most recently in England (Devon Beaver Trial). If the decision is made that beavers should remain, then it is anticipated their domestic legal status will change, and management strategies will be developed. We recommend that advice and necessary permission should be sought from the appropriate Statutory Nature Conservation Organisations (SNCOs) before employment of any mitigation measures.
The history of beavers in Britain
'The church ... the mill, bridge, salmon leap, an orchard with a delightful garden, all stand together on a small plot of ground. The Teivi has another singular particularity, being the only river in Wales, or even in England, which has beavers. In Scotland they are said to be found in one river, but are very scarce.' Giraldus Cambrensis (1180)
The above quotation describes a British landscape, moulded by people to suit their needs, which was also occupied by Eurasian beavers. The salmon (Salmo salar) leap, where fish could be harvested for consumption during their annual migration, offers a tantalising clue as to why the Eurasian beaver may have survived on the River Teivi at a time when it had otherwise become such an unfamiliar species in a British landscape. In 10th-century Wales, a beaver pelt was worth 120d (pence), and a pine marten (Martes martes) pelt 24d, while Eurasian otter (Lutra lutra), Eurasian wolf (Canis lupus lupus) and red fox (Vulpes vulpes) pelts were worth 8d each (Rodgers 1947–48). Did this community, which successfully managed its fish, also tolerate beavers for the prospect of a similar and profitable annual harvest?
The Eurasian beaver is a native species which was once widespread in freshwater habitats throughout Britain. Fossil records indicate that beavers were present in Britain 2 million years ago – and archaeological evidence, including gnawed timber, dams, lodges, burrows and bones, has been recorded from a number of sites (Macdonald et al. 1995; Coles 2006). Various place names, illustrations and other references bear testament to the former presence of this animal (Coles 2006). In 1837, the nearly complete skeleton of a beaver was found in a hole in the bank of the River Stour, near Keynston Mill in Dorset.
Eurasian beavers were hunted to extinction in Britain for their castoreum (a secretion from their castor glands with supposed medicinal properties, used by beavers in chemical communication), meat, fur and other body parts such as jaw bones. By the 15th century, the trade in their fur was no longer economically viable due to overexploitation, and their presence began to fade from folk memory. Oral traditions of their presence on Loch Ness and in Lochaber in Scotland, and in the Ogwen Valley in Wales, lingered on until the end of the 18th century (Coles 2006). Some of the latest physical evidence of beaver presence in Britain is a beaver-chewed stick carbon dated to 1269–1396, which was found in the upper Tyne catchment (Manning et al. 2014). While we will never know when the last British beaver was killed, a church ledger record from the village of Bolton Percy near York in 1780 records the payment of a bounty of tuppence for the head of a beaver (Coles 2006). No other references to the species' survival beyond this date are currently known.
2.1 Beaver reintroduction in Britain
The concept of reintroducing beavers to mainland Britain (they are not known to have ever been native to Ireland or any of the outer isles) is not new. Their restoration has been widely discussed in both the general media and academic literature. Despite recommendations for a more comprehensive process of restoration (Gurnell et al. 2009), the return of the beaver has been a haphazard affair. At the time of writing, two officially licensed trial beaver releases into the wild exist: the Scottish Beaver Trial in Mid-Argyll, and the Devon Beaver Trial on the River Otter, Devon. The Scottish Government is due to consider the results of the trial and make a final decision on the future of beavers in Scotland (expected some time in 2016). Additionally, in the mid-2000s it became apparent that a sizeable population of unlicensed wild beavers were distributed throughout the catchment of the Rivers Tay and Earn in Perthshire, Scotland (Campbell et al. 2012a). In England and Wales, there is scattered evidence from field signs and photographs of the existence of small numbers of free-living wild beavers. Wild beavers are therefore already present in Britain. There are also a growing number of enclosed populations, and there are proposals for further trial releases in England and Wales (e.g. Welsh Beaver Project). Unless British governments decide to remove these beavers their populations will increase and their distribution expand. An understanding of their management requirements will therefore become a necessity.
Lord Onslow, writing in the Countryman magazine in 1939, suggested that as the 'beaver have become extinct in England only within the last few centuries ... there seems no reason at all why they should not be reintroduced' (Onslow 1939). In 1994, Scottish Natural Heritage (SNH), Natural England (then English Nature) and Natural Resources Wales (then Countryside Council for Wales) began to consider the potential for restoring beavers in Britain. To date, this process has progressed furthest in Scotland, with an official trial reintroduction and the scientific study of the larger unlicensed population in Tayside, though the Devon Beaver Project was given a licence for a five-year scientifically monitored trial release on the River Otter in 2015.
In 1998, SNH launched a public consultation to ascertain wider attitudes to beaver reintroduction in Scotland (SNH 1998). While the majority of respondents favoured reintroduction, there were concerns and opposition expressed by others who feared that beaver activity would have detrimental impacts on farming, fisheries and forestry. In response to these findings, SNH took the decision to develop a time-limited, trial reintroduction in the Forestry Commission Scotland (FCS)-managed Knapdale Forest in Mid-Argyll, to explore the feasibility of releasing beavers and to study their impacts. Although an initial SNH licence application (2002) was turned down in 2005 by the then Scottish Executive, a joint licence application submitted in 2007 by the Scottish Wildlife Trust (SWT) and the Royal Zoological Society of Scotland (RZSS) was successful. This led to the development of the Scottish Beaver Trial, the first licensed and unfenced reintroduction of Eurasian beavers (and in addition the first official mammal reintroduction) in Britain.
Although to date the reintroduction process has progressed furthest in Scotland, feasibility studies on beaver reintroduction to Wales (Halley et al. 2009) and England (Gurnell et al. 2009) have been published. Since the first release at Ham Fen in Kent in 2002 (Campbell and Tattersall 2003), breeding populations of beavers have been established in large enclosures at several locations in England, Scotland and Wales. One example of a well-studied project of this type is the demonstration site established in 2011 in the upper watershed of the River Wolf which has been developed by the Devon Wildlife Trust (DWT 2013). These controlled projects can provide useful information when employed specifically to assess the role of beavers as habitat-modifiers and as tools for landscape management or stakeholder engagement.
Beaver biology and ecology
3.1 Taxonomy and distribution
The Eurasian beaver and the North American beaver are the only surviving members of the once larger family of Castoridae. Both modern beaver species are physically very similar, making them hard to distinguish in the field. They have very similar ecological requirements and behavioural patterns, and were once considered to be a single species. Chromosome analysis has identified that the Eurasian beaver possesses 48 pairs of chromosomes, while the North American beaver has 40 (Lavrov and Orlov 1973). As a result, the two species will not interbreed and produce viable offspring, even when attempted through captive breeding. Through differences in tail shape and subtle differences in their pelage, beaver species can be determined on closer inspection. Examination of the anal gland secretions provides reliable differences in colour and viscosity which can be used to determine beaver species and sex (Rosell and Sun 1999). It is now believed that divergence occurred about 7.5 million years ago when beavers first colonised North America from Eurasia across the land bridge of the Bering Strait (Horn et al. 2011). From the Eurasian fossil record of the Early and Middle Pleistocene (~2.4–0.13 Ma ago), in mature rivers and wetlands, modern beavers appear to have lived alongside, or possibly to have been locally excluded by, the slightly larger extinct beaver Trogontherium cuvieri; the prevalence of the two forms at archaeological sites demonstrates an inverse relationship (Mayhew 1978).
By the 16th century, Eurasian beavers were largely extinct across most of Europe and Asia. At its lowest population point, it is believed that the Eurasian beaver in its western range was reduced to 200 animals on the River Elbe in Germany, 30 on the River Rhone in France and ~100 in Telemark, Norway (Nolet and Rosell 1998). Since the 1900s, beaver numbers have recovered throughout much of their former European range as a result of a combination of legal protection, hunting regulation, proactive reintroductions/ translocations and natural recolonisations. Breeding farms that produced beavers for commercial fur farming, and later for release into the wild for restocking, were established at Voronezh (Russia) and Popielno (Poland) in 1933 and 1958, respectively (Jaczewski et al. 1995). The first official conservation translocation occurred from Norway to Sweden in 1922, and since then there have been more than 200 recorded translocations of beavers (Halley et al. 2012). Eurasian beavers have now been restored to over 24 countries in Europe (Halley and Rosell 2002) and are currently estimated to number over 1 million individuals globally (Halley et al. 2012).
Also notable is a sizeable population (~8,000) of introduced North American beavers in Finland (Kauhala and Turkia 2013) and northwest Russia. In 1937, seven North American beavers from New York State, USA, were introduced to Finland to supplement an ongoing reintroduction of the nearly extinct Eurasian beaver there (Lahte and Helminen 1974). At that time, most zoologists recognised only one species of beaver worldwide (Parker et al. 2012). North American beavers are now also present in small numbers in parts of Belgium, western Germany and Luxembourg, as a result of escapes from a zoo and game parks (Dewas et al. 2012). Due to the significant biological and ecological similarities of these two species, identification and removal of the non-native North American beaver is important, requiring active management and resource investment (Parker et al. 2012).
Excerpted from "The Eurasian Beaver Handbook: Ecology and Management of Castor fiber"
Copyright © 2016 R. Campbell-Palmer, D. Gow, R. Campbell, H. Dickinson, S. Girling, J. Gurnell, D. Halley, S. Jones, S. Lisle, H. Parker, G. Schwab and F. Rosell.
Excerpted by permission of Pelagic Publishing.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
Table of Contents
1 Introduction 1
1.1 Aims and purpose of this handbook 4
2 The history of beavers in Britain 5
2.1 Beaver reintroduction in Britain 6
3 Beaver biology and ecology 9
3.1 Taxonomy and distribution 9
3.2 Anatomy and appearance 11
3.3 Breeding and young 12
3.4 Habitat and territoriality 13
3.5 Diet and feeding 14
3.6 Behaviours 15
3.7 Parasites and diseases 18
3.8 Population biology 19
3.9 North American beaver introductions 22
4 Legislation 24
5 Effects of beavers 32
5.1 Beavers as ecosystem engineers 33
5.2 Beavers and species of high conservation value 35
5.3 Beaver effects at a catchment scale 38
5.4 Beavers in landscape-restoration projects 40
5.5 Beavers and managed land use 41
5.5.1 Agriculture 44
5.5.2 Horticulture 46
5.5.3 Woodland and forestry 46
5.5.4 Fisheries 52
5.5.5 Engineered environments 55
5.5.6 Recreational areas and water bodies 61
6 Managing beaver impacts 63
6.1 Damming activity and associated management techniques 65
6.1.1 Ecology 65
6.1.2 Benefits 66
6.1.3 Issues 67
6.1 A Management options 68
6.1.5 Animal-welfare considerations 79
6.2 Burrowing and associated activities 79
6.2.1 Ecology 79
6.2.2 Benefits 79
6.2.3 Issues 80
6.2.4 Management options 80
6.2.5 Animal-welfare considerations 82
6.3 Foraging activity and associated management techniques 83
6.3.1 Ecology 83
6.3.2 Benefits 83
6.3.3 Issues 84
6.3.4 Management options 84
6.3.5 Animal-welfare considerations 89
6.4 Animal management 89
6.4.1 Ecology 90
6.4.2 Benefits 90
6.4.3 Issues 91
6.4.4 Management options 91
6.4.5 Animal-welfare considerations 100
7 Survey and monitoring 103
7.1 Non-invasive monitoring techniques 103
7.2 Habitat suitability/habitat-use survey 104
7.3 Monitoring beaver population size and development 106
7.4 Distribution mapping and population estimates 107
7.5 Habitat assessment prior to beaver release 109
8 Learning to live with beavers 111
8.1 Future management recommendations 111
8.2 Public relations, education and socioeconomics 113
8.3 Conclusion 117
Appendix A Eurasian beaver field signs 119
A.1 Teeth marks 119
A.2 Felled and gnawed trees 119
A.3 Ring-barking/bark stripping 120
A.4 Grazed lawns and cut vascular plants 121
A.5 Feeding stations 121
A.6 Foraging trails 122
A.7 Lodges and burrows 123
A.8 Food caches 126
A.9 Dams 126
A.10 Canals 127
A.11 Scent mounds 128
A.12 Faeces 128
A.13 Tracks 128
Appendix B Diseases and parasites of the Eurasian beaver 131
B.1 Parasites 131
B.2 Bacteria 134
B.3 Fungi 134
B.4 Yeasts F35
B.5 Viruses 135
Appendix C Beaver-management techniques 136
C.1 Flow devices - dam piping 136
C.2 Flow devices - culvert protection 139
C.3 Dam-removal/dam-notching 142
C.4 Burrow management 143
C.5 Bank and flood-bank wall protection 144
C.6 Individual tree protection 146
C.6.1 Mesh protection 146
C.6.2 Paint protection 147
C.7 Electric fencing 148
C.8 Permanent exclusion fencing 149
C.9 Deterrent fencing - ditches and small streams 150
C.10 Trapping and translocation 153
C.10.1 Bavarian beaver traps 153
C.10.2 Boat trapping 156
C.11 Humane dispatch 157
Appendix D Management protocol chart 159
Appendix E Captive beaver fencing recommendations 161
Appendix F Terminology for various beaver-management devices 162
Appendix G Beaver fieldwork risk assessment 164
Appendix H Beaver survey data sheets from the Scottish Beaver Trial 166