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Writer's pictureHarris Brooker

Beaver Blog

Following the recent re-introduction of Beavers to the Cairngorms National Park we wanted to take this month to focus on this incredible ecosystem engineer!


In this picture there is a Beaver at the water's edge.
Beaver (Photo Credit: Cath Wright)

The European Beaver (Castor Fiber) is one of two species of large semi-aquatic rodents that lives in Europe and northern parts of Asia. The other is the North American Beaver (Castor Canadensis), which between them are the second largest rodents on Earth after the Capybaras that live in South America.


Some people might know its North American relative which is smaller headed and has a more oval tail, though the main difference between them is their differing chromosome counts and through study  it’s been found they can’t interbreed with each other.


European beavers grow from 70 – 100 cms in length, with their tails adding an extra thirty to forty centimetres to their length and weigh between eighteen to thirty kilograms and are capable of living at least ten years.


Beavers live monogamously and often live in small family groups, living not in their dams but in holes in the shore of whatever waterbody they live in or build lodges. They breed between December and April with one to six kits being born, though the typical litter size is two or three. The young are born in early summer and are capable of breeding at two years old but don’t usually do so successfully until they are three.


In this image there is a Beaver submerged in the water but it's shallow enough for its body to be seen.
European Beaver (Photo Credit: Mike Hems)

After their first year, the young are capable of helping their parents repair their dams whilst older siblings may help in raising future offspring. Beavers are territorial but they will tolerate fellow kin members as neighbours which they can recognise via their scent marking.


Beavers are herbivorous and eat grass, sedges and other aquatic plants which they gather by swimming along waterways they have created through their damming activities. Those plants are mostly eaten in the summer with their winter diet being the bark of trees such as Willow, Polars and Alder. They can gnaw through wood because of the presence of iron in their tooth enamel which also give their teeth an orange colour. In the autumn they will cache food for the winter by dragging twigs and branches to the bottom of their waterbodies and pushing them in there close to the entrance to their lodges, which are underwater.


In this image there is a tree that has been felled by a Beaver.
Tree Felled by Beaver (Photo Credit: Cath Wright)

In this image there is a tree that has been gnawed by a Beaver by the water's edge.
Tree that has been gnawed by a Beaver (Photo Credit: Cath Wright)

They are very ungainly on land and their creation of waterways through the forest means they have an easy escape from predators such as bears, wolves and lynxes. When in the water they can move up to five miles per hour and hold their breath for 15 minutes. When underwater they close their eyes but can still see thanks to their nictitating membranes, which work like swimming goggles - Ospreys and Dippers have the same feature.


They tend to go out and forage either early in the morning or late in the evening and are best seen at these times during the summer. In the evening, they can be seen just before dark. They don’t hibernate but remain active throughout the year. The European Beaver is a native part of British wildlife and was hunted to extinction in the 16th Century, with the last reference to them in England being in 1526. They were hunted for their fur, meat and castoreum, which is a yellowish substance produced from two sacs under their tails, which was used for perfumes and confectionary. For the animal itself, the castoreum is mixed with urine for scent marking purposes.


In fact in much of the world, Beavers were on the verge of extinction, but this trend has since been reversed and it is now listed by the International Union for Conversation as Least Concern.


The Beaver’s reintroduction to Britain has been one of our greatest success stories but not one without controversy. One of the big reasons for bringing Beavers back to Britain is because they are a keystone species. This means that they have an importance to the wider ecosystem that if interfered with, would affect their ability to survive as well.


Beavers make dams, which are made of mud, wood and stones which can partially block waterways and slow down water flow. If an area of water is too shallow for them, they can deepen it, with the ideal depth that they feel safe in being around 70 centimetres.


In this image there is a Beaver's dam blocking a waterway.
Beaver's Dam (Photo Credit: Cath Wright)

Their dams are designed to let some water flow through but being slower means that the Beavers themselves have the safety and security they need. This also creates larger habitats for other species such as Water Shrews, Water Voles and Otters, as well as a variety of birds, fish and amphibians. Ironically fishermen have sometimes expressed objection to the idea of reintroducing Beavers because of a belief that they eat fish. They do not eat fish, but instead create greater habitats for them. There were also worries about what their damming activities could do to agriculture and urban development.


In this image there is a Beaver's dam blocking a waterway in a forested area.
Beaver's Dam (Photo Credit: Cath Wright)

The Knapdale Project in Argyll was a major experiment carried out between 2009 and 2014. It was done to determine whether Beavers could viably live in Britain. 16 Beavers were taken from Norway and introduced to Argyll where they were monitored to see how they affected the habitat. In 2016 the Scottish Government, satisfied that they were beneficial, allowed the population to stay and expand. This became the blueprint for other reintroductions to occur elsewhere, such as various parts of England and within Scotland, the Cairngorms National Park.


In this image there is a Beaver swimming in the water with its face above it.
Beaver swimming (Photo Credit: Mike Hems)

If you would like a chance to visit places where Beavers live in the Cairngorms, please go to our website to book one of our Day Guides.

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