Beaver reintroductions

Beaver species

There are two species of beaver, the Eurasian beaver, which is native to Scotland and the North American beaver. They are very similar in appearance and habit, but the North American beaver is slightly larger and builds significantly bigger dams.

How big is a beaver?

Beavers can grow in size similar to that of an average dog. They usually weigh between 16–30kg, measuring 60–90cm in body length, with tail lengths of 20-35cm. Unusually for mammals, female beavers are the same size or slightly larger than males of the same age, and they are difficult to tell apart.

Beavers are the second-largest rodent in the world. Like other rodents, they have four long incisor teeth which carry on growing throughout their lives. The front surfaces of the incisors are orange, thanks to tooth-strengthening iron within the enamel. This is ideal for gnawing through wood.

Eurasian beavers, our native species, were once found from eastern Asia to western Europe and Britain. They are thought to have almost gone extinct by the 1600s due to overhunting. They were targetted for their fur and castoreum, a substance once used for medicinal properties and for making perfume. Legal protection and reintroductions to 24 countries in Europe in the 20th century have restored them too much of their former range.

How long do they live?

In the wild, most beavers that survive their first two years have a life expectancy of 12-14 years.

What do they eat?

Beavers are completely vegetarian. They do not eat fish but instead aquatic plants, grasses and shrubs during the summer months and woody plants in winter. They will look to find most of their food within 5m of the river bank and rarely travel more than 20m from water. When they eat trees, they prefer softer wood and species that can most easily regenerate, like willow, aspen and birch. They can fell large trees but tend to favour small saplings, which are easier to digest.

Are beavers coming back anywhere else?

In addition to recent projects in England, Eurasian Beavers have been reintroduced to Austria, Belgium, Croatia, Czech Republic, Estonia, Finland, France, Germany, Hungary, Italy, Latvia, Lichtenstein, Lithuania, Montenegro, the Netherlands, Norway, Poland, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland and Ukraine.

Habitat – where do beavers like to live?

As with most animals, beavers need food sources and shelter. The food sources they use are riverside trees and woody shrubs, particularly those that regenerate quickly and aquatic vegetation like reeds and sedges, so they prefer well-vegetated river banks, particularly where there is woodland. Water two feet deep gives them more cover from predators and they tend to avoid streams with gradients steeper than one in seven.

How do beavers manage such an aquatic lifestyle?

Beavers are adapted for an aquatic lifestyle, with a sleek, waterproof coat and flat, scaly tails they use as rudders which they can also slap against the water as a warning alarm. Their thick, dense brown fur helps keep their skin dry. ‘Nictitating membranes’ or third eyelids act like swimming goggles. Beavers have valves to close their ears and noses while swimming and can hold their breath for up to 15 minutes. They can even close their mouths behind their front teeth so that they can chew underwater!

How many young are there in a litter?

Beaver young are called kits, and there are usually between one and four kits in a litter.

How many litters do beavers have in a year?

One, usually born between April and June.

How long do beaver kits stay with their mother?

Kits stay with their mother until they are about two years old. They usually stay in the lodge for four to six weeks while their parents and older siblings bring leafy twigs for them to eat before emerging to feed with their parents.

At what age do they start to breed?

Beavers can breed from as young as two years old. Beaver pairs are thought to mate for life or until their partner dies. Mating takes place between December and February.

How do beavers travel through landscapes?

Beavers spend most of their lives no more 20m from water, although they are occasionally known to range up to 100m from a watercourse. They struggle with steep ground, so they tend to travel up and down rivers and move into relatively flat tributaries, though they can deal with short steep stretches and occasionally cross open ground if they have to.

What does a beaver lodge look like?

Eurasian beavers build two kinds of lodge. Where the banks are suitable, they prefer to dig burrows into the riversides, especially where there is woodland vegetation to provide food and cover. If the banks are too rocky for this, they will take the time and effort to build a lodge from mud and cut branches. All lodges have a safe underwater entrance and at least one dry chamber.

Where do beavers build dams?

Beavers only build dams where their habitat does not provide all the conditions suitable for their needs – they won’t make an effort if they don’t need to build a dam. Beavers feel safe with water around them, so they may construct a dam where they want to create deeper ponds to build a lodge, or to allow them to get to food resources without having to leave the water.

Many dams are temporary, especially on ‘flashy’ streams where water levels swell quickly after heavy rain – beaver dams will start to fall apart when they are overtopped by fast-flowing water.

Eurasian beavers create smaller dams than their North American counterparts, on narrower streams rather than broad, fast-flowing rivers. Most dams are therefore built on narrower streams, and it is unusual for dams to be built on rivers wider than 6m.

Beavers are often referred to as ecosystem engineers because their industrious activities bring a range of benefits to other wildlife, which also tend to bring advantages to people.

River bank woodlands

In woodland environments, beavers help to stimulate new growth by gnawing on tree stems and coppicing. This helps to breathe new life into tired forests and creates a diverse age range of trees which often leads to a flush of wildflowers which attract pollinating insects such as butterflies. The openings created in the woodland canopy offer perfect hunting grounds for bats. As the thicket grows, it can provide ideal nesting sites for birds such as warblers. It also creates standing dead wood used by a range of specialist insects and bird species like woodpeckers and nuthatches. The regrowth of trees coppiced by beavers depends on the browsing pressure from deer being low enough to permit regeneration, so protection with fencing can sometimes be an important part of riverside habitat management.

Wildlife

Beaver dams form wetland habitats behind the dam, which quickly start to increase the number of living areas available for certain plants to grow. This in turn creates better habitats for insects which then provide greater food sources for fish, birds, bats and other mammals like water voles and water shrews. The result is an enriched, more biodiverse habitat, with more food and shelter availability, for a broader range of wildlife. See reference materials.

Fish

A number of studies have found that beaver presence tends to have a positive effect on fish populations, including trout and Atlantic salmon, by increasing feeding opportunities and by providing more places for fish to shelter in the channel or survive in times of drought. In parts of the US, fishery managers are actively encouraging beaver activity to improve the quality of habitat for fish populations. See reference materials.

Reducing flooding

In general terms, beavers help reduce the risk of flooding lower down in river catchment by building dams that slow the flow of water. The diagram below shows the monitoring results, demonstrating how beaver dams in the River Otter in Devon act to spread the runoff of storm waters over time, thereby avoiding the tendency of that river to flood. In Bavaria, where beaver reintroduction led to a bitter conflict, now resolved, between farming and conservation in the 1990s, beaver dams are now credited with protecting at least one previously flood-prone village from flooding.

Improving water quality

Beaver dams filter water flows. Research suggests that ponds and water pools created from beaver dams can benefit local water quality. Dams are usually only built on small streams, which can moderate the detrimental effect of irregular flow. The ponds they create can help to neutralise acidic run-off, act as sinks for pollutants and increase the self-purification of a watercourse. They can form considerable sediment traps, reducing erosive runoff and particulate loads in downstream water. This has been demonstrated in several studies from Europe and the US and has also been assessed at the River Otter in Devon.

Economic benefits

Studies of the socio-economic effects of beavers in Scotland have found both financial and non-monetary benefits from having beavers in a local area. Wildlife tourism is the most significant economic benefit, but figures have also been calculated for the monetary value of volunteer time and educational benefits. See reference materials.

Beavers are strongly territorial, so there is a natural limit on how many beavers will occupy a river system – once all the available territories in a catchment are occupied, new animals need to travel in search of suitable habitat.

Successful reintroductions in Europe have all seen animals spread slowly into available territories. After a number of years, populations usually start to grow rapidly, disperse in search of suitable habitat and then settle at a level that the available habitat can support. How quickly this happens depends on the richness of the landscape for beavers. For instance, it has taken several decades for Norwegian and Swedish beaver populations to fully occupy the habitat available there, whereas we might expect river systems here to become fully occupied more quickly.

Beavers have now been reintroduced to Austria, Belgium, Croatia, Czech Republic, Estonia, Finland, France, Germany, Hungary, Italy, Latvia, Lichtenstein, Lithuania, Montenegro, the Netherlands, Norway, Poland, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland and Ukraine.

Beavers in Scotland

Beavers were once found throughout Scotland, but had been hunted to extinction by the 1600s. They have special glands near the base of the tail that produce a substance called castoreum, which they use to mark their territory. Humans hunted beavers not only for their fur and meat but also for this substance. Castoreum was prized for its medicinal properties and used in making perfume.

However, since 2009, beavers have returned to Scotland via a formal reintroduction trial in Argyll and through accidental or illegal releases on Tayside. Elsewhere in Britain, a population which established itself on the River Otter in Devon became part of a government trial in England which has been allowed to remain there permanently. Quietly, beavers have also had a small presence in Strathglass for at least the last ten years.

Knapdale

As part of an official trial, four beaver families were released to Knapdale in Argyll by the Scottish Wildlife Trust and the Royal Zoological Society Scotland. The trial ran from 2009 to 2014, aiming to explore the ecological effects of beaver reintroduction, the impacts on socio-economic concerns and the potential for increased tourism by attracting visitors interested in beavers.
The trial was preceded by an extensive community consultation during which a range of views and concerns were expressed. This consultation was revisited in 2017 when Scottish Wildlife Trust asked the local community whether they supported steps to ensure the continued presence of beavers in Knapdale.

At least some of this support is based local businesses reporting an upturn in business due to interest in the trial, increasing visitor numbers to the area. As one local hotelier said: “As a local businessman, I welcome the return of beavers to Knapdale. Beavers are fascinating creatures famed for their industrious habits, and their arrival to Knapdale creates a booming industry for local businesses. Visitors can now come to the area, enjoy some of Scotland’s most beautiful countryside landscapes whilst enjoying fresh local cuisine and have the chance to spot Scotland’s first beavers in the wild”.

Tayside

A significant population of beavers has become established in the Tay river system following a series of either accidental escapes or illegal releases since the early 2000s. A survey carried out in 2012 indicated that there were 38 or 39 beaver territories in the river system at that time. An update to this report in 2021 indicated that this had increased to 251 active territories across the Tay and Forth catchments. A total of 118 dams, 178 lodges and 443 burrows were recorded across the catchments at this time.

The fact that the beavers were released illegally meant that no plans were in place to deal with their effects on land uses like farming and fishing in the catchment for some years after beavers first appeared. As a result, some crop farmers in the lower, flatter parts of the river have seen their crops damaged by flooding caused by beaver dams. In areas where the riverbanks are particularly sandy, beaver burrowing has exacerbated erosion of riverside farmland.

In recent years, NatureScot has developed a Management Framework for Beavers which provides technical advice and funding for practical action to mitigate beaver impacts on land use. This advice and funding will be available at any location in Scotland where beaver impacts are found.

Argaty

Earlier this year, Argaty farm near Doune in Perthshire released a second family of beavers, relocated from lower Tayside, onto their waterways. Their farm is close to the River Teith where a beaver population is already established. This was the first time beavers had been relocated to unenclosed ponds on private Scottish land. The relocation was applied for and led by the farmer there, who was keen to give beavers that would otherwise have been culled a new home and add to the farm’s appeal for wildlife tourism. Both beaver families released to this farm have remained at their release ponds and the first kits were born this year.

Loch Lomond

Another proposal to relocate beavers within the current range is currently being developed by RSPB Scotland for their nature reserve in the southeast corner of Loch Lomond, at the mouth of the River Endrick. At the time of writing, that consultation is still underway.

Beavers are native mammals in the UK and spent thousands of years alongside people and wildlife until they were hunted to extinction. However, while beavers have been a natural part of our environment in the past, they do have the potential to cause problems for some modern land uses. These problems can often be mitigated using techniques that have been successfully developed and applied in other countries.

Localised flooding

Beaver dams can cause localised flooding. Where narrow channels are dammed, stream waters can build up behind and spread onto the neighbouring ground, especially where the stream banks are low. While this can create valuable wetland habitat, it can also cause problems by flooding valuable farmland, as has happened in the lower reaches of the Tay catchment, where beavers have dammed drainage ditches running between crop fields. The resulting flooding has damaged crops and caused significant damage, especially to the arable land tends to be low-lying and flat.

Impeding fish migration

Salmon and sea trout use small burns to reach their spawning grounds. Access to these areas is therefore vital in maintaining healthy wild fish populations. Fish have swum through, round and over beaver dams for thousands of years, although in dry periods, low water levels can temporarily prevent adult salmon and trout from jumping dams to access their spawning areas. This is most likely to occur in smaller burns, but this has the potential to affect a significant element of the local fish migration in a given year.

In Strathglass and on the Beauly, Dr Alan Puttock from the University of Exeter has used computer modelling to predict the likely frequency of beaver dams across the catchment. Beaver Dam Capacity modelling indicates where dams are most likely to occur and the capacity of a given stretch of river to support beaver dams, rather than the number of dams that are likely to occur – the results can be seen below. This is a valuable tool in understanding the potential impact of beavers on the migratory fish populations of this river system and key to the discussions we hope to have with local fishing interests.

Beavers and trees

Beavers eat trees and fell them to provide building materials. They have a strong preference for softer wood and for trees that will regenerate most readily, like willow, birch and aspen. They can fell large trees, but tend to favour small saplings. The places where beavers have been on this river are often marked by the characteristic pointy stump of a beaver-chewed trunk with fresh new shoots growing up from beneath the cut. This coppicing effect helps to maintain tree cover for the long term and to provide changing conditions of light and shade on the river which can benefit aquatic plants, insects and fish.

Crop damage

Beavers will forage in arable crops like sugar beet, carrots, potatoes and cereals. This is usually confined to within 20m of the water’s edge, although they will sometimes dig canals to expand the area they can reach without straying too far from water. Beavers will also dam drainage ditches and this has been a significant cause of flood damage to crops in the lower stretches on Tayside.

Burrowing banks

Beavers will burrow into riverbanks to create lodges where the conditions are right. They prefer well-wooded banks beside quieter backwaters with low energy flows for this. Burrows may extend a few metres under the bank, which can undermine the ground above, especially where it is used by cattle or farm machinery. Lightly vegetated sandy areas undermined in this way can open the exposed soil to severe erosion.

The experience of beavers elsewhere in Europe and North America has taught us a lot about how their impacts can be avoided or reduced.

The Beaver Management Framework

NatureScot operates a fully resourced advice and management approach for identifying and delivering action on the ground to manage and mitigate impacts from beavers on land management.  A staff team is available to ask for advice, visit situations on the ground, and where needed, to implement practical steps to address beaver-related issues.  One of NatureScot’s team is based in Inverness.  Some of the main practical techniques that can be used to address impacts are outlined below and the costs of implementing these will be met by NatureScot.  This Framework is fully supported by Government and is not time limited.

Avoiding flooding caused by beaver dams

There are two common techniques to prevent flooding caused in areas where beavers build dams. The first is to insert an overflow pipe into the dam which lets water escape downstream, before it overtops the stream banks. A second form is used to ensure that beavers don’t block drainage culverts by building fencing out from the mouth of the culvert which blocks the beavers.

Lowering dams to help migrating fish

In Europe and the US, where there are concerns about beaver dams and fish migration, the relevant streams are identified in advance and any dams that appear are removed or lowered ahead of the spawning runs.

Tree protection

Fencing is used to keep beavers out of areas with sensitive or valuable areas of trees which are close enough to a river bank that beavers might access them.

Bank protection

Taking steps to create strips of woodland along banks that might be vulnerable to burrowing can go a long way to securing them against damage. The binding effects of vegetation and the limited use by livestock protect the bank from erosion. If areas of the bank with a high likelihood of burrowing are identified, they can be safeguarded with willow ‘spiling’ or metal anti-burrowing grids.

Hierarchy of management options

The Scottish Government announced in November 2020 that they will actively support the expansion of the beaver populations in Scotland. It has also been agreed that beavers will be managed following a hierarchy of approaches, starting with the least intrusive and leading up to lethal control as a last resort. This means that if less harmful approaches cannot address beaver impacts, trapping/relocating beavers from this catchment and lethal control will remain as available options.