A Western Australian sheep farmer is facing major financial and emotional losses after a series of suspected dog attacks killed or injured dozens of animals on his property near Porongurup.

Farmer Brad Cluett says about 80 sheep from his flock have been killed or euthanised following attacks over the past five months. The most serious incident occurred in May, when 40 lambs and 10 ewes were found affected after an attack during the lambing period.

Mr Cluett breeds sheep at his farm in Porongurup, about 385 kilometres south-east of Perth. He raises Merino ewes and white Suffolk rams and says the repeated attacks have caused both significant financial losses and considerable distress.

The attacks have involved different animals. Mr Cluett said some lambs were found with serious injuries to their heads, while larger sheep had been attacked around the face and suffered severe bleeding. Some animals were so badly injured that they had to be euthanised.

The farmer believes domesticated dogs are responsible. During one incident, he saw what he described as a large, rangy dog several hundred metres away from the affected paddock, but he was unable to catch it. He said neighbouring properties had also reported incidents involving livestock and other animals in the area.

The attacks have also affected the behaviour of the remaining flock. According to Mr Cluett, sheep have moved significant distances from their normal grazing areas after being attacked. Some ewes have abandoned lambs, while pregnant animals have reportedly miscarried after experiencing stress.

The financial impact has been particularly serious because the attacks occurred during lambing season. Mr Cluett said the major attack contributed to a 40 per cent reduction in the lambing results for that group of sheep.

Beyond the financial losses, the farmer says repeatedly finding injured or dead animals has taken a significant emotional toll. He described the experience of caring for livestock throughout the year only to discover animals killed by attacks as extremely upsetting.

The Shire of Plantagenet has launched an investigation into the incidents and is attempting to identify the animal responsible. Chief executive Garry Bird said authorities hoped to locate the dogs and, if an owner is identified, potentially prosecute them and seek recovery of the farmer's livestock losses.

Dog attacks on livestock remain a concern for farmers in parts of Western Australia's south. Domestic dogs can retain their hunting instincts even when they are normally kept as household pets. When dogs enter farming properties, they can chase and attack sheep, sometimes killing animals even when they do not consume them.

Farmers are now keeping a close watch on livestock in the area, particularly during lambing. Mr Cluett said the uncertainty surrounding another possible attack was creating ongoing anxiety for him and his family.

The investigation remains underway, and authorities are hoping information from residents and nearby property owners will help identify the animal or animals responsible.