RARE Exmoor ponies have been brought in to help conserve one of the North-East's most important wildlife sites.

As an experiment, the chestnut brown ponies are being used to eat an unwelcome species of grass growing on Thrislington Plantation, a national nature reserve close to Thrislington Quarry near Ferryhill.

The 23-hectare reserve is jointly managed by construction materials company Lafarge Aggregates and English Nature.

An important part of managing the reserve is to protect rare, blue moor grass from being overtaken by the more rigorous growing upright brome.

Finding animals to graze on the brome has been difficult as most sheep will not touch this particularly coarse grass.

But English Nature thinks it has cracked the problem by using an animal that is as rare as the giant panda - the Exmoor pony.

A Durham Exmoor pony owner has lent some animals for winter grazing of the reserve.

"The Exmoor pony has a strong, flat mouth which can graze the sward as short as sheep and likes eating the tough upright brome," said John Hope of English Nature.

"The only problem is that people come to the reserve and feed the ponies when we want the ponies to be concentrating on eating grass." Supplementary feeding of bread and greens can cause severe stomach problems for the ponies when they are feeding on this coarse material.

Thrislington Plantation was first designated as an SSSI in the Sixties, containing species-rich grassland characteristic of the magnesian limestone.

It is the home of 21 species of butterfly, including the notable Northern Brown Argus 'salmacis' form. Nine species of orchid are present on site, six in large enough numbers to make a spectacular show from May to August.