Keep your dogs on a lead and under close control at all times - that's the urgent message from the Pembrokeshire Coast National Park after a distressing and costly incident involving sheep and lambs on Sunday.
Dogs ran loose in a field near Marloes and scattered a flock of sheep and new lambs. As a result, 16 of the lambs were unable to link up again with their mothers and subsequently died.
Farmer Owen Morgan, of Marloes Court, is counting the cost this week.
"These lambs were only three or four days old and without their mothers' support and milk and in the very cold night they didn't have a chance.
"If the dogs had been on leads this would not have happened," added Mr. Morgan. "All we ask is for those in charge of dogs to act responsibly."
National Park area ranger Malcolm Cullen said the dogs were being taken by a visitor along a footpath and had jumped over a hedge into the field.
"We cannot over-emphasise the responsibility that lies on those in charge of dogs. This incident shows what damage can be caused in a few seconds.
"There are many visitors around this half-term and many have dogs with them."