DOG owners have been implored to keep their pets on leads at Moel Famau and other areas with livestock.
The call, from Denbighshire County Councillor and farmer Huw Williams, comes after a lamb was attacked on Friday, May 12.
Cllr Williams, ward member of Moel Famau, said he was informed by wardens just before lunch, and discovered that the lamb belonged to another farmer.
He explained: "This happens all the time - I've just taken the tenancy of my farm over from a lifetime friend who'd just had a bellyful of these sheep attacks.
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"He reckons he always had 30 sheep less coming down at the end of the summer than he was putting up there.
"And if you imagine the growth of the bracken, the gorse and heather, once something is bitten or chased and killed, the chances of finding it are very slim, so there may be even more than we know about.
"I don't blame the dogs - I really want to say that. It's not the dog's fault.
"It's the careless dog owners, and they are only a small minority."
Cllr Williams said he was out looking for a lost ewe one weekend, and over the course of an hour he had to tell five owners to put their dogs on leads.
"People just ignore the signs," he said.
"The trouble is that the dogs come in the back of a car and might have travelled a fair distance.
"The first thing they want to do is run around and then they see a big fluffy ball of wool which gets startled.
"It's a game then; it is a natural instinct for the dog to hunt.
"They will chase them for miles until the ewe is exhausted and then they attack.
"We don't want to stop people enjoying Moel Famau or other area, but they need to put their dogs on leads."
Cllr Williams said the call is also for the welfare of the dogs, adding: "Ticks are really bad at this time of year.
"They latch onto people as well as dogs and unless you know what you're looking for, it can kill the dog."
Speaking of the consequences of dog attacks, he concluded: "No farmer whatsoever wants to shoot a dog.
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"They are someone's pet, part of a family, and we shouldn't be thinking like that.
"I am a dog lover and an animal lover - why put a dog in a situation like this?"
"And for the farmer, if you put a lamb at £100 a piece - that might be someone's profit.
"Not only that, but the genes of the ewes we have up there go back 300 years; by losing them you're jeopardizing the flock.
"And when you've spent 18 hours lambing the sheep in the cold, wet, wind, frost; to see something you've produced being slaughtered by an irresponsible dog owner, it is absolutely heart-breaking."
Cllr Williams explained he is taking a motion to Densbighshire County Council for dogs to be kept on leads on the authority's land in the open country and has so far had good support for it.
The incident at Moel Famau was reported to North Wales Police's rural crime team, he added.
PCSO Iwan Owen of the Rural Crime Team said: “Incidents of livestock worrying in popular walking areas are far too common.
“It creates distress for the sheep, the farmers and has potentially serious consequences for the dog owner and the dog itself.
“We would urge all dog walkers to behave responsibly in the countryside and keep their dogs on a lead whenever livestock are present.”
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