VISITORS to Dartmoor have been urged to keep their dogs on leads as the lambing and bird nesting season gets under way. Also at risk from canines on the loose are calves and ponies. National Park Authority officials took to the slopes with their pets this week to enjoy a ramble and highlight the Paws On Dartmoor campaign. Recreation chief Andrew Watson said: 'Although a dog may not be actively chasing livestock its presence can still cause a disturbance. 'During the lambing season ewes are particularly vulnerable. 'The national park is a living working landscape and spring is one of the busiest and most important times of the year for farmers. 'A frightened animal may abort or abandon its young, a tragedy for the animal and a financial loss to the farmer.' Paws On Dartmoor leaflets with advice for dog owners are available from moorland visitor centres as are leads made in Ashburton from Twool, a mixture of Dartmoor wool and twine. Throughout the Easter holidays rangers will be handing out free information cards to visitors. Anyone witnessing the disturbance of wildlife or stock is asked to call the police on 101 or the Dartmoor Livestock Protection Officer on 07873 587561.