Engineering an environmental revival

THERE’S no evidence that beavers were ever in Ireland.

What a pity — we have no excuse to introduce an animal which would greatly benefit our environment.

Reintroduction begins in Scotland this year and Natural England, advisor to the British government on environmental issues, recommends the return of beavers there.

These iconic animals used to live in Britain where they were hunted, not just for their flesh and fur, but also for their scent glands. These provided a substance used in traditional medicine.

Overexploited, beavers became extinct in the 12th century, although a few may have remained until the 16th century. Beavers have survived only in Norway, Finland and Germany. The last Swedish one was killed in 1871.

The EU Habitats Directive requires member states to consider returning extinct species to their former haunts and, it’s argued, bringing “nature’s eco-system engineers” back to Britain would be beneficial. The structures created by beavers, some experts claim, reduce flooding, purify water and increase the range of plants and animals, including fish, in river systems.

Beavers were successfully reintroduced to France — they are now in the Rhone and the Loire. Beginning in 1922, about 60 beavers from Norway were released in Sweden, which now has more than 100,000 of their descendants. A reintroduction to Kent in 2001 failed, but a study carried out that year, predicted Norfolk could support 18 to 40 beaver families.

Europe’s largest rodent weighs up to 38kg, four times as much as a badger. A river dweller, its hind feet are webbed and the great flat tail serves as a paddle.

When alarmed, a beaver slaps the water loudly with the tail, alerting its family to danger. The nose and ears close when the animal is submerged. Swimming low in the water, beavers are not easy to see — some come out during the day but most are nocturnal. They venture on to land to feed and create territorial scent mounds, known as “castoreums”.

Beavers need a stretch of river at least 2km long bordered by softwoods. Contrary to popular belief, they don’t eat fish and are no threat to angling.

Leaves, twigs and juice-rich tree bark are mainstays of their diet. A flap on the inside of the cheek blocks the throat behind the teeth so vegetation can be gnawed underwater. No animal, apart from man, engages in such extensive habitat management or so radically transforms the landscape in which it lives. Beavers use logs, branches and boulders to build dams. They fell trees, chiselling through trunks with their powerful teeth. The trees are floated downstream and dragged into position. The structures, up to 100m long, keep river water at levels which suit the builders.

Channels give access to feeding areas. The family home, known as a “lodge”, is a hollow mound of branches with underwater entrances and a platform above the water inside.

Food stores help support the family through lean periods and there are designated “refectories” where the animals eat.

It’s an ingenious arrangement — beavers can make feeding excursions even when rivers are frozen and the land is covered in snow. There are dangers, however. Beavers have been known to drown when trapped under ice. Virtually all plant-eating animals are polygamous but the beaver is an exception and is Europe’s only monogamous herbivore.

Although studies have shown that reintroducing beavers increases the bio-diversity of an area, not everybody wants them back. Some people argue that beaver dams actually increase the threat from flooding.

Foresters worry trees will be damaged. Water engineers are anxious lest beavers undermine river banks with their burrows and farmers don’t want beavers eating their cereal crops.

These fears, beaver enthusiasts argue, are exaggerated and inspired by the Canadian beaver, a separate species and more aggressive builder of dams than the European one.


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