European beaver – Castor fiber

Castor fiber

Photo
© Niall Benvie

The European beaver was an important part of the native fauna of the Caledonian Forest. Hunted to extinction by the 16th century, it is now poised to become the first of our extirpated mammals to be reintroduced.

Distribution

The European beaver was originally distributed throughout most of Europe and northern Asia, from Scotland to eastern Siberia. Within this range, beavers occurred along wooded streams and rivers, and in small ponds and lakes surrounded by trees. However, by the end of the 19th century beaver populations in Europe had been reduced to a few isolated sites in the Elbe River basin in Germany, the Rhône River basin in France, and southern Norway. Other small populations survived in Belarus, Russia and Mongolia. The main cause of this dramatic reduction in beaver numbers was hunting for their pelts, meat and castoreum (a secretion from their scent glands), although habitat loss was also a contributory factor.

Since the 1920s, beaver reintroductions have taken place in thirteen European countries, and by the early 1990s beaver numbers in Europe were estimated to have recovered to about 250,000. However, the International Union for the Conservation of Nature (IUCN) still classifies the beaver as `Vulnerable’, meaning that it could become in danger of extinction in the future. (Note: the North American beaver,Castor canadensis, is a different species, and has always been confined to Canada and the USA.)

Distribution in Scotland

Based on palaeontological and archaeological remains and historical evidence, scientists have concluded that the beaver was widely distributed throughout mainland Scotland, with bones having been discovered from Dumfriesshire in the south to Caithness and Sutherland in the north, as well as in Perthshire and Moray.

The exact date of the beaver’s disappearance from Scotland is unknown, but it was certainly still present in the 12th century, when excise duty was collected on the export of its pelt. Written records indicate that it may have survived in small numbers at a few locations until the 16th century.

Photo © Niall Benvie

Physical characteristics and behaviour

The beaver is the largest rodent native to Europe, with adults weighing 18-20 kg., and exceptionally, up to 29 kg. Head and body length is between 70-100 cm., while the tail is from 30-40 cm. long. The beaver is mainly nocturnal and is highly adapted to its semi-aquatic lifestyle, with sleek waterproof fur, a distinctive, hairless, flattened tail and webbed hind feet, which it uses for propulsion in the water. The beaver also uses its tail to slap the water surface when it is alarmed, before diving underwater and swimming away; it can remain submerged for up to fifteen minutes. The long claws on its front feet are adapted for digging, and the beaver is highly dexterous, being able to hold small objects between its toes while feeding. Beavers generally live for 7-8 years, but have been known to live for up to 25 years. With most of their predators, such as the wolf (Canis lupus), brown bear (Ursus arctos), lynx (Felis lynx) and wolverine (Gulo gulo), now very rare or extirpated from their former range, most beaver mortalities are caused by humans, through poaching, road accidents and entanglement in nets.

Beavers live in small family groups, usually consisting of 3-5 individuals and comprising an adult pair, kits, yearlings and one or more sub-adults. Females normally reach reproductive age at three years, and an adult pair produce one litter per year, consisting of 2-3 kits. A family group will have a territory which averages 3.6 km. of river bank, but can be from 0.5-13 km., depending on the availability of food. Territories are scent marked with castoreum, a secretion from the anal gland beneath the tail, which has long been known to have medicinal properties. (Castoreum contains salicylic acid, the main active ingredient in aspirin, and the hunting pressure for castoreum was one of the main causes for the beaver’s historical decline in numbers.)

The European beaver prefers burrows in river banks as a nesting place, but it will build lodges of piled logs where burrowing is not possible. It builds fewer dams than the North American beaver, and it does so generally in shallow streams to maintain water levels above the entrance to its burrow. Dams are built of tree trunks, branches and mud, and are about one metre in height and rarely longer than fifteen metres. They are usually breached by flood waters each year, and do not normally pose any obstacle to the movements of fish such as brown trout and salmon.

The beaver is entirely herbivorous, and in the late spring and summer eats mainly aquatic plants, grasses, ferns and shrubs. At other times of the year, woody species form the major part of its diet, with aspen (Populus tremula), birch (Betula spp.), oak (Quercus spp.) and rowan (Sorbus aucuparia) being particularly favoured, although it will also eat willow (Salix spp.), alder (Alnus glutinosa) and ash (Fraxinus excelsior). Conifers are rarely touched. Feeding generally takes place within ten metres of the water’s edge, and the beaver will rarely travel more than 100 metres from water. It prefers trees with a diameter of less than ten cm., but it is capable of felling trees up to one metre in diameter. In areas with harsh winters, the beaver will transport woody material to its burrow or lodge, storing it there so it can feed when the water is frozen. In common with other rodents, the beaver’s incisors grow constantly during its life, and it needs to use these teeth regularly to prevent them from becoming too long. For this reason the beaver will sometimes gnaw trees without actually felling and using them.

Ecological relationships of the European beaver

Beavers are notable amongst mammals for their ability to alter their surroundings to make them more suitable as their habitat, mainly through the construction of dams, canals etc. These activities determine many of the relationships which beavers have with the flora and fauna where they live.

The felling of trees obviously has an effect on the riverside forest, but this rarely results in deforestation of the riparian zone. Their effect on many of the deciduous trees they fell is akin to a natural coppicing process – species such as oak, rowan and willow will send up new shoots from the stump of a felled tree, whilst aspen will also regrow, through its reproduction is by root suckers, or ramets. The presence of beavers therefore tends to encourage the production of young shoots or trees in many instances. Although flooding caused by dams can result in trees being drowned, it has also been postulated that beavers historically helped the spread of alder in Britain, by creating suitable habitat for these water-loving trees to grow in.

The ponds created by beaver dams favour the growth of aquatic vegetation and also result in population increases of invertebrate species. This in turn provides an enhanced food source for fish, amphibians and birds, which also benefits predators higher up the food chain such as otters (Lutra lutra) and grey herons (Ardea cinerea), which eat the fish. Otters are known to use beaver burrows and lodges, as do water voles (Arvicola terrestris), while several species of birds, including mallard (Anas platyrhynchos), teal (Anas crecca) and goldeneye (Bucephala clangula) nest on beaver ponds.

In North America, the beaver is considered a keystone species (see Principles of Ecological restoration page) in river and pond ecosystems, and it is likely that the beaver would fulfil a similar vital ecological role here. After an absence of about 500 years, the proposed return of the European beaver to Scotland will mark a major and significant step forward for the restoration of our degraded and fragmented ecosystems.

…

During the first half of 1998, Scottish Natural Heritage ran a public consultation process, asking the general public (and those living in Scotland in particular) whether they were in favour of beaver reintroductions in specific and limited areas of the Highlands of Scotland and, if so, whether they were in favour of this happening in the next two years. Below is Trees for Life’s detailed response to this consultation process.

Response from Trees for Life
to the public consultation (1998) about
a beaver reintroduction to Scotland

Summary

Trees for Life strongly supports the recommendation from Scottish Natural Heritage that European beavers be reintroduced to Scotland, and that such a reintroduction should take place within the next three years.

Furthermore, we strongly urge that the beaver reintroduction be accompanied by a specific, focussed programme to achieve a substantial expansion of riparian woodland ecosystems, in order to ensure the long-term viability of a reintroduced beaver population.

Details of our response supporting the proposed reintroduction

1. Beavers play an important role in riparian ecosystems, and their extirpation in Scotland is a significant factor in the historical depletion of the country’s natural biological diversity. From an ecological perspective, we believe that the reintroduction of beavers is essential to return our rivers to an optimum state of health again. Their return will have benefits for a wide range of other species, including fish populations and mammals such as water voles and otters. In North America, beavers are considered to be `keystone species’ in conservation biology terms, and we believe that European beavers were originally of similar importance in riparian ecosystems in Scotland.

2. Scotland is one of the most biologically-impoverished countries in Europe, with almost all of our large mammals having been hunted to extinction, and only 1% of our native forest still surviving. We believe there is a moral and ethical obligation now to reverse the degradation of the past, wherever possible, and this is also reflected in the European Community’s Species and Habitats directive, where the UK has an obligation to consider reintroducing extirpated species of wildlife. Of all our extirpated mammal species, the European beaver is perhaps the simplest and least problematical in terms of a reintroduction, and as such it provides an ideal first step in the direction of reinstating our missing species of fauna, and thereby returning our country to an improved state of ecological health.

3. Since the 1920s, beaver reintroductions have taken place in 13 other European countries, without major problems or serious conflicts with other land uses. As a result, viable beaver populations have been reestablished in every country concerned, except possibly the Netherlands (where the reintroduction is too recent to evaluate fully) and Switzerland (where the numbers are small, although they had doubled between the time of the first reintroduction, in 1956, and 1993)1.

As beavers have been proven to thrive in European countries such as France and Germany, which are more densely-populated and cultivated than Scotland, we believe that the successful results obtained on the continent will be repeated here, if a carefully planned and monitored beaver reintroduction is carried out. However, beyond that, considerable experience has been gained from those previous reintroduction programmes, and this will be of direct benefit to a Scottish reintroduction, thereby enabling it to have the best chance of success.

4. Trees for Life’s Executive Director, Alan Watson Featherstone, was one of the participants in February 1996 in a study tour to a beaver reintroduction site in Brittany, France. The beavers there live in a mainly agricultural landscape, and through site visits and meetings with local farmers etc, the tour participants were able to ascertain that the beavers caused very few problems. The participants observed a small amount of damage to trees in a conifer plantation, which in terms of the overall size of the plantation would best be described as trivial, and also learned of a problem when beavers had blocked a culvert under a road, causing temporary flooding. Beaver dams and lodges were also observed, with the former being small in height and breached by water flows at the time of the tour. Conversations with local people and the scientists monitoring the beavers confirmed that the dams did not impede the movements of brown trout in the river.

The participants were left at the end of the tour with no doubt that European beavers could be successfully reintroduced to Scotland, and this first-hand experience forms an important underpinning of our support for the current proposal from SNH.

5. As beavers are entirely herbivorous and generally shy mammals, they pose no threat to people, or to economically important stocks of animals or fish through predation. In the unlikely event that a reintroduced population of beavers were to cause serious problems of some unforeseen sort, their specific riparian habitat requirements and relatively small home territories would make them easy to trap and remove. In other words, a beaver reintroduction would be readily controllable and even reversible, if it were to go wrong (although we know of no evidence to suggest that this would be the case).

6. While concerns have been raised about the possible negative effects of beavers on fish populations, such as brown trout and Atlantic salmon, in practice these concerns are not sustained out by the evidence from other beaver reintroduction sites. During the beaver tour to Brittany referred to in section 4 above, the participants learned first-hand that the beavers there pose no problems for brown trout, and indeed are considered beneficial for trout fisheries 2.

Although the location visited in Brittany did not contain interacting populations of beavers and Atlantic salmon, experience in Norway (where the conditions more closely resemble Scotland than do those in Brittany) shows that beaver populations are not considered a problem for salmon stocks there 3.

7. Tourism is a major factor in the Scottish economy, and worldwide nature-related or eco-tourism is the fastest growing sector of the tourist industry. Magazines such as BBC Wildlife are full of advertisements for Nature Holidays both in the UK and abroad, while the Highland Wildlife Park at Kincraig, which contains small captive populations of most of our extirpated mammals (including beavers) receives large numbers of visitors each year. We believe that the reintroduction of beavers to Scotland will have a positive effect on tourism here, with direct financial benefits to the areas where beavers are reintroduced, and to the country’s economy in general.

Recommendation for a related programme to accompany a beaver reintroduction

In it’s research for the proposed beaver reintroduction, SNH has concluded that the existing riparian woodland habitat in Scotland could support up to 1,000 beavers. However, this habitat is widely dispersed and generally does not form large contiguous sections. Furthermore, the report also indicated that of 17,000 square kilometres of buffered water and wetland in Scotland, only 4% (771 square kilometres) contained broadleaf riparian woodland 4.

This small percentage reflects the widespread loss of native forest which has occurred in Scotland, and we believe that for a beaver reintroduction to be successful in the long term, it will have to be accompanied by a concerted programme of riparian woodland expansion, to provide adequate habitat for a genetically-sustainable population of beavers. Whilst beavers reintroduced in the next 3 years to the sites identified by SNH as potentially suitable should be able to thrive there, the viability of a Scottish beaver population in the long term will depend on a sufficiently large interbreeding pool of individuals being maintained. Given the fragmentary and widely dispersed state of the suitable habitat at present, this is not likely to be achieved without a significant increase in riparian woodland (for example, if beavers were to be reintroduced to the Tay area and the Ness area, these widely separated populations would be unable to interbreed).

Thus, we strongly advocate that a beaver reintroduction be accompanied by a special programme to ensure that the extent of riparian broadleaf woodland in Scotland is substantially increased, with particular emphasis being placed on the areas targeted for beaver reintroductions. Such a programme should focus on linking up existing fragmented sections of riparian woodland to create larger contiguous expanses, and re-establishing some riparian woodland in areas where it is presently completely absent. The programme should have targets set for the riparian woodland cover to be expanded from the present figure of 4% to say 15% or 20% over the next 10 years, and increasing again beyond that. Emphasis should also be placed on tree species such as aspen, which are favoured by beavers. Because of its relative inability to reproduce by seed, aspen is one of the tree species which has suffered most from historical deforestation in Scotland, and is therefore already in need of assistance to ensure its regeneration (Trees for Life has been running a successful aspen propagation programme in the Glen Affric area for several years now). The reintroduction of the European beaver therefore provides an ideal opportunity for the establishment of a concerted programme of riparian woodland expansion, and for the regeneration of important species such as aspen, which are currently under-represented in Scotland’s native forests.

Such a programme should be facilitated by a series of incentives, both from SNH itself as part of the beaver reintroduction scheme, and in conjunction with the Forestry Authority’s Woodland Grant Scheme (WGS), where special measures could be added to specifically encourage riparian woodland restoration and expansion, and it make it more cost effective for landowners to implement such schemes. Such a programme would not only benefit the return of the beaver, but also, in and of itself, would make a significant contribution to the restoration of Scotland’s biological heritage through expanding the area of native riparian woodland and all its associated species of flora and fauna.

NB: We do not see this recommendation as one which should delay the reintroduction of the beaver, but rather it should proceed concurrently with the reintroduction, in an integrated coherent strategy.

References:

1. MacDonald, D. W. et al (1995) Reintroducing the European Beaver to Britain: nostalgic meddling or restoring biodiversity? Mammal Review, 25, 161-199

2. Jones, P. (1996) A preliminary assessment of the possible impacts of reintroduced European beavers Castor fiber on freshwater salmon fisheries in the UK A report to the Atlantic Salmon Trust on the “Brittany Beaver Tour” 21-24 February 1996 3. Jonsson, Prof. B (1995) Norwegian experience with beavers in salmon rivers Personal communication

4. Webb, A., French, D.D. and Flitsch, A.C.C. (1997) Identification and assessment of possible beaver sites i n Scotland Scottish Natural Heritage Research, Survey and Monitoring Report No. 94.

Latest reintroduction news

Scottish Natural Heritage (SNH) conducted a public consultation process during the first half of 1998 in the UK and particularly in Scotland to gauge public support for the reintroduction of the European beaver. Though the final results and report of that exercise are yet to be published, initial response showed an overwhelming public support for the beaver’s return. SNH have now approved in principle a five year trial project, due to begin in 2002, whereby up to 50 beavers will be brought from Norway and radio-tagged before release so that their impact on the environment can be monitored.

A big thank you to all our supporters who contributed their views to the public consultation!