European beaver ecology

What is a Beaver?

Beavers are rodents just like mice! However they are much larger, in fact, they are the second biggest rodent in the world weighing in between 11 and 26kg and growing up to 4 foot long! Beavers are highly social animals, living in family groups, in and around freshwater. They are a very important part of the aquatic environment and are known as “keystone species” because of their benefits to other species and the habitats they create. There are two species of beaver Castor canadiensis (found in the USA, Canada and Mexico) and Castor fiber, the Eurasian beaver, which was found across Europe.

They are very well adapted to their amphibious lifestyle. The two most distinguishing features of the beaver are its large front teeth (incisors) for cutting down trees and its big flat tail which is used to store fat, steer themselves through the water and slap to ward of predators. They also have a streamlined torpedo-shaped body for swimming underwater and a double-layered fur with outer guard hairs for waterproofing and a dense underfur for warmth. It’s really important that the beavers groom regularly to keep their fur waterproof and insulating. To do this they use their second toe on their hind foot which has a double claw which can be used as a primitive comb.

Water Babies

Beavers love water they feel safe in the aquatic environment. Any sign of danger and they can disappear under water. They can swim at an amazing 2.1 metres per second and can stay underwater for 15 minutes!

Vegetarians

Beavers only eat plant material (they don’t eat fish). Their huge incisors (two front teeth) and molars are used to chew vegetable matter. Beavers won’t eat conifers but the bark and cambium layer of deciduous trees is very tasty as are lily rhizomes (root stores). All in all they have been recorded to eat 80 species of tree and nearly 150 species of herbaceous and aquatic plants.

Plant material is difficult to digest so they have micro-organisms living in their gut which have enzymes to break down the tough plant material. Beavers have to eat lots to get enough goodness.

“Timber”!

Beavers are famous for felling trees. The reason they like to fell trees is not only for building material but also so they can access more food that would normally be out of reach. The record diameter for a beaver felled tree is 106cm! Their large front teeth are ideal for chipping away at the trunk of a birch, willow or aspen tree. They like to fell trees near the waters edge so they can drag them into the water and float them easily to their lodge or dam.

Dams

Beavers sometimes build dams to raise the water level of a particular area. They are hard-wired to stay in water for safety from predators, so if they want to access more trees they sometimes extended their loch. Beavers are stimulated to build dams where they can hear running water and begin damming where the sound of water is loudest. They use sticks to construct the dam and mud is plastered over it to make it watertight.

Lodgings

Beavers live in lodges which are constructed in a similar way to dams (sticks and mud). They can also dig into the bank of a river or loch and create a series of tunnels and chambers. The entrance is always under water, protected by sticks, again for protection from predators. Just beyond the entrance is a feeding chamber with tunnels leading to the sleeping chambers. Usually they take about 20 days to make. Imagine building your house that quickly!

When Evening comes…….

Beavers are nocturnal (active mostly at night time and rest in the day). Their whiskers are important for feeling their way around in the dark as is their sense of smell and hearing.

Fancy Words

“Eco-engineers”, “keystone species”, “geomorphologic agents”….. some of the words used to describe beavers. They all mean that the beaver is really important! They modify habitats which in turn benefits many different plants and animals promoting biodiversity. Felling trees opens up freshwater shorelines and results in the growth of lots of water loving plants. They fulfilled the function of the “earth's kidneys” - Indian Folklore

The History of Beavers in Britain

Beavers were widespread on mainland Britain but were hunted to extinction about 450 years ago. Castoreum (an oil secretion from the anal gland) was thought to have medicinal purposes, their meat was considered good to eat and their fur made excellent hats for cold weather because of its insulating and waterproof properties. There have been several successful reintroductions in Europe including in Sweden, Norway and Poland. Scotland has ideal beaver habitat……………

Reintroducing Beavers to Scotland

The beaver’s role as a keystone species has been evident for a long time and its reintroduction to Scotland would have ecological benefits. Their dams sustain water flow and prevent flooding. Their engineering also enables slow release of water during dry periods. Diversity of the riparian zone (the area around the river) increases with the presence of beavers. They also raise the level of the water table which is good for crops.

Overall the Scottish people are for the reintroduction, provided that there are suitable management controls in place, but there are some groups, for example fishermen and foresters, who are against the reintroduction of the beaver. Several groups in support of the beaver have been campaigning for the reintroduction.

More research and demonstration projects are needed to prove how beavers would benefit the ecosystem and people. This is why Aigas introduced two beavers to the loch in April 2006.

The Aigas Beavers

A male and female beaver were released into the Aigas loch in April 2006. Since then we’ve seen them build their own lodge, feed on willow, birch and lilies, fell numerous trees and have a total of two kits, that’s one each year! It’s been very interesting to follow their behaviour in an accessible wild-like situation. We do not feed the beavers, we leave them to their own devices within their large enclosure. We’ve had lots of people come and visit the beavers including the BBC!

                             Text researched and presented by Jenny Grant and Ian Sargent

Click here to read the 2007 Aigas beaver diary