Motorists are being asked to slow down on a common that is home to one of Wales’ rarest butterflies, after four cows that graze the site were killed in fatal collisions.

A herd of hardy cows play a vitally important conservation role by keeping the grass on Rhos Common, on the northern edge of Neath Port Talbot, at the perfect length for the Marsh Fritillary butterfly.

But, the common is split by the fast road between Crynant and Ystradgynlais and despite cattle grids being placed at either end of the common, four cows have been knocked down and killed over the last two years.

The Rhos Common Commoners teamed up with wildlife charity Butterfly Conservation (BC) and PONT (the Wales Conservation Grazing organisation) to re-introduce grazing on the common to provide more breeding areas for the Marsh Fritillary – a butterfly which is in decline right across Europe.

But it is now the cows that need protecting following a spate of fatal collisions.

Independent Councillor for Crynant, Sian Harris is leading a campaign to reduce the speed limit on the road.

She said: “We are appealing to local residents and other road users to lower their speed when the cattle are on the common”.

Karl Hopkins, one of the graziers, said: “On a small common like Rhos it is just too costly to go through the process of getting it fenced. We will put up signs so people know when the cattle are actually turned out on the common.”

Richard Smith, Project Officer from BC said: “The common is a vital part of our efforts to conserve the Marsh Fritillary in this area and we were pleased to help the Commoners by providing signs to warn motorists. Without the cows, the common will be neglected and lose the variety of grassland plants, insects and birds.

Emma Douglas from PONT said: “The grazing is important in controlling the build-up of dead grass that can fuel wildfires in the spring. It also ensures that the common remains scrub-free for local people to enjoy.”

The wider project includes sites in Ystradgynlais and Seven Sisters with input from Natural Resources Wales, Brecknock and South and West Wales Wildlife Trusts and Neath Port Talbot County Borough Council.

The Marsh Fritillary butterfly is usually on the wing from the middle of May until mid-June and can be identified by its colourful wings, which are far brighter than other fritillary butterflies.

The upper wings are reddish-orange, with yellow or white patches and black veins. It is also the only fritillary to have a row of black dots around the bottom edge on both sides of the hindwing, but none on the forewing.