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Beavers at Cors Dyfi

Posted: Tuesday 30th March 2021 by Emyr MWT

Beavers are back at Cors Dyfi for the first time in centuries.

Following years of hard work, two animals were released into a specially built enclosure over the weekend. Here are 10 things you need to know about the beavers at Cors Dyfi:

1. Why are they here?

Today, Cors Dyfi is a lowland peat bog – an extremely important habitat in Wales – but the reserve was once used as a conifer plantation.

Due to the difficult residual terrain of former forestry ditches and tree stumps, managing areas of the reserve using traditional methods, such as coppicing by hand or even water buffalo, is all-but impossible in places.

Over the years, Montgomeryshire Wildlife Trust have been considering a range of alternative management options, including water buffalo. In recent years, beavers – often referred to as ‘ecosystem engineers’ and well known for their amazing ability to manage wetland habitats – have come to the fore as an ideal solution.

One of the Cors Dyfi water buffalo in his prime. Now retired and living his autumn years with his mate in Devon.

Beavers are large, semi-aquatic rodents that live within wetland and river habitats; they will munch away at the rampant willow and birch growth, stopping Cors Dyfi drying up and maintaining it as a wet, lowland peat bog.

2. Are they free?

No, the beavers have been released into a 700m enclosure specifically built in 2020 to hold them. It's around seven acres in total area.

Alicia Leow-Dyke (Welsh Beaver Project) and Dr. Roisin Campbell-Palmer (Scottish Wildlife Trust) inspect the new beaver enclosure in 2020.

We will be able to monitor them in the enclosure and record changes to the habitat. If you are fairly local and would like to help by volunteering, please get in touch with our Volunteer Officer (


3. How many beavers are there?

Last Friday, 26th March 2021, two individuals were brought down from Scotland which are from European stock originally.

These are two males, a father and son. We intend to bring the whole family down with the mother joining her mate and offspring during the next few days.

Iolo Williams does the honours, diolch Iol.

We've made sure that the Cors Dyfi enclosure is more than big enough for the beavers to have an ample home range. In fact, it's big enough for any offspring to breed themselves and start a family without conflict with its parental family.

We will be able to move animals around various UK populations to prevent excessive inbreeding.

4. What species are they exactly?

There are two species of beaver in the world, both living in the northern hemisphere: the North American beaver (Castor canadensis) and the Eurasian beaver (C. fiber).

The Eurasian beaver has a more elongated skull with a more triangular nasal bone opening, lighter fur color and a narrower tail. In addition, the North American beaver is slightly longer and larger overall.

The individuals at Cors Dyfi are European beavers, C. fiber, their ancestors having been sourced from various European populations.

A relatively small population of American beavers are present in Finland (see map) following the release of seven animals in 1937.


5. Beaver history

By the 1900s the beaver population in Europe had been persecuted to the brink of extinction - just like the osprey. Beaver numbers fell catastrophically from approximately 100 million animals to just 1,000 a century ago.

Beavers werehunted for their fur, pelts, meat and castoreum, is a yellowish fluid from the castor sacs of mature beavers.

Beavers use castoreum in combination with urine to scent mark their territory. Both beaver sexes have a pair of castor sacs and a pair of anal glands, located in two cavities under the skin between the pelvis and the base of the tail. Castoreum has been used in medicine, perfume and food flavoring, while beaver pelts have been a major driver of the fur trade.

Traditional Welsh costume - including Cardiganshire beaver hats. No wonder they died out here.

Once the urgent need for conservation of the beaver became apparent, re-introduction programmes commenced in earnest across Europe. These projects began in the 1920s, and at least 1,500 reintroductions have now taken place in most European countries.

Interesting tale from a 1776 traveller to Machynlleth:

A wild release into the Dyfi river is planned later this year, Wales being one of the very last European countries to do so.


6. What will happen now?

Not only will the beavers in the enclosure manage the willow and birch growth for us, they will, as a natural by-product, increase the biodiversity in the enclosure, making way for more plant and animal species to flourish. A fantastic win/win situation.

We will monitor the changes to the habitat and report back on the increase in biodiversity we record.

Beavers are natural 'ecosystem engineers' - the physical modification of habitats by organisms. We also class beavers as a keystone species.

A keystone species is a species which has a disproportionately large effect on its natural environment relative to its abundance. Keystone species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether.


7. Is a license required?

No, not for a release into an enclosure (although we did acquire one). There are three other enclosures in Wales, none of which require a license.

However, the wild release later this year will require a license from Natural Recourses Wales which is currently being processed. Similar licences have been granted for numerous releases in Scotland and England (beavers never colonised Ireland after the Ice Age).

8. What's in a name?

The English word "beaver" comes from the Old English word beofor or befor (recorded earlier as bebr) and is connected to the German word Biber and the Dutch word bever.

The ultimate origin of the word is from an Indo-European root for "brown". The genus name Castor has its origin in the Greek kastor and translates as "beaver".

The Welsh word for beaver is afanc (pronounced avank). Many Welsh place names exist that reference the historical presence of beavers: Llyn yr Afanc, for example, a lake near Betws y Coed.

There is also a very old Welsh word, 'llostlydan', which means broad-tail. Very apt.

Wales, beavers and mythology - a young woman luring the afanc to the shore on the River Conwy.


9. Are they protected like the ospreys at Cors Dyfi?

Yes, we have a raft of surveillance cameras, fixed-point photography locations, trail cameras and a few other protection measures that we won't go into for obvious reasons.

Later this week we will install a telephoto camera 12m up on a telegraph pole.

Beaver-cam, or ET-cam as we're calling it.

10. Can we see them?

Not really. Beavers are mostly nocturnal, so the chances of seeing one while we're open during the day is limited. We will, however, publish any decent photos and videography we take of them.

It's not the best type of habitat to view ground-dwelling mammals at the best of times.

We'd like to build a beaver lodge (think bird hide in the shape of a beaver's body) one day. A chance to actually see the mammals close up. A fantastic educational facility and possibly semi-submerged? Alarm clocks mandatory, watch this space.

And Finally...

The adult male we have is a little unusual, he is a much rarer black morph of the species; a genetically determined rare coat colour.

Dad should be easy to identify once spotted!

Should we name them? What do you think?

How about Barti and Byrti?

Barti (left) with son, Byrti, having a dip.


You can find the beaver page of our website here.

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