Hundreds of miles from their homeland an ancient breed of pony has been brought North for its beneficial grazing habits.

The hardy breed thrives on poor vegetation and a small herd arrived on an organic farm in North Yorkshire yesterday to play a part in an unusual conservation scheme sponsored by the Department of Environment, Food and Rural Affairs (Defra).

Six Exmoor ponies have been drafted in for the winter as part of an innovative project to preserve the delicate biodiversity of the Yorkshire Wolds. Their non-fastidious taste in food will ensure that the species-rich character of the land will survive.

Some 300 miles from Devon, the herd are sited at Brownmoor Farm, Leavening, near Malton. The farm, which has 90 acres of chalk grassland, supports a wealth of wildflowers, grasses and herbs and is managed under a Defra Countryside Stewardship Agreement.

Under the scheme farmers are paid to follow more traditional farming methods, with the aim of enhancing the landscape, encouraging wildlife, and protecting historical features.

On the chalk grassland of Brownmoor farm the cows and sheep avoid grazing on the tor grass, a tough, dominant species that can crowd out the rarer species. Exmoors however are one of the few native British pony breeds to graze on tor grass, and by keeping it at bay the ponies will help preserve the delicate biodiversity of the landscape.

Farmer Michael Wright said: "As an organic farm we welcome any natural method we can use to encourage a variety of plants and flowers to flourish in the dale. We're looking forward to the seeing the results in spring, when the first wildflowers to benefit from the project will appear."

The Yorkshire Exmoor Pony Trust, a group that maintains a herd of ponies especially for conservation grazing, has provided the ponies.

A trust spokesman said: "Exmoor Ponies are the nearest breed in existence to the original wild hill pony of the ice age. They have evolved to over thousands of years to thrive on poor vegetation like tor-grass in our cold, wet climate."