Dam it!

By Isabella Tree

These endearing young kits belong to a 17,000-strong population of beavers in Bavaria. Hunted to the verge of extinction in the 19th century for their silky fur and castoreum – the secretion from the scent sacs close to the tail used for making perfume – they’ve made a dramatic comeback across Europe: an estimated 639,000 individuals by 2003. Sit on the banks of the Danube at dusk and you’ll invariably see them sliding through the water, dragging branches or digging in the river bank.

Reintroduction programmes began as long ago as the 1930s. Slightly larger than their North American counterpart and with eight more chromosomes, the Eurasian beaver is just as skilled at hydrological engineering. Ecologists consider them a keystone species because of their beneficial impact on flood and drought mitigation, and on biodiversity. Their coppicing of trees along the riverbanks – for food and to build dams and lodges – lets in sunlight which encourages green, oxygen-producing aquatic plants, while the woody debris they drag into the water provides a jungle of substrate for micro-organisms to grow on – fuel for populations of invertebrates which, in turn, provide food for fish and aquatic birds.

The British Isles used to be busy with beavers; placenames resound with their ghosts: Beverley in Yorkshire, Beverston in Gloucestershire. They too became extinct during the hard-hunting reign of Henry VIII and we grew used to life without them.

Now they’re back. In March this year, on the upper reaches of the River Otter in Devon, I stood in the gathering dusk to watch the first reintroduction ever of an extinct animal in England. It was a surprisingly controversial event. Farmers and landowners are concerned about potential damage to their land and anglers argue that beaver dams could prevent the migration of salmon and other fish.

The pro-beaver lobby can take comfort from Europe. In Bavaria, opposition from anglers has declined as water quality and fish stocks have risen. Wonderfully named beaver consultants and volunteers clear away dams where flooding threatens farmland. Beavers generally only build dams in water courses where the water level is below a metre – to provide themselves with protection against predators like foxes and wolves, and for easy access to food during winter.

On the banks of the River Otter, three shadowy figures lollop into the river. With a flick of their tails they disappear, except for one, a pregnant female who glides around, queen of the scene. The size of a tubby spaniel, she emerges onto a sand-spit to preen herself. She is perfectly adapted for her watery domain with sleek, oily fur, webbed back feet, valves in the ears and a nose that closes underwater; her broad, flat, scaly tail serves as both rudder and scull. The characteristic buck teeth with which she is grooming herself are self-sharpening secateurs that make swift work of logging.

They’re not the only wild beavers in Britain. In May 2009 Scotland began a trial reintroduction programme at Knapdale in Argyll. Around the same time an unsanctioned population, believed to have descended from escapees from an enclosure in 2001, was reported on the River Tay. The native, it seems, has returned. ■

Images: Nature Picture Library