Dog attacks have ripped through two Otama farms, killing more than 25 hoggets and ewes in the past three months, farmers say.
Farmer Donny Nicholson was the worst hit, losing 16 hoggets in the first attack at his farm in April.
Two weeks ago another attack killed five pregnant ewes.
''I think it's just a rogue dog - I think he must just be hungry,'' Mr Nicholson said.
''It's a terrible start to the day when you see your sheep have been attacked, but then I just have to get on with my day - it's better to get over it quickly.''
Mr Nicholson said the dog was grabbing sheep by their back legs and killing them.
''Some of them aren't dead in the morning, so I have had to kill them myself,'' he said.
Mr Nicholson had not seen the dog on his farm, and believed it was attacking at night-time.
''One of the workers was off the farm late one night. When we returned to the farm the next day some sheep had been killed and the blood was dried,'' he said.
''It has to be coming at night-time. None of us have seen the dog and we have no idea who it belongs to.''
Mr Nicholson said the attacks on his livelihood were very disappointing.
He had set a trap to catch the dog if it returned.
''The gate will close behind the dog if it comes back, so I will be able to see it in the morning.''
Gore District councillor and farmer John Gardyne said three of his ewes were killed in a dog attack about two weeks ago.
''He gets into their necks and gets them that way - my three were dead when I got to them in the morning.''
Cr Gardyne said a ewe cost between $205-$250, while rural columnist Henry McFadzien said a lamb was worth $160-$170 this season.
Cr Gardyne agreed with Mr Nicholson the dog likes to strike in the dark.
''The dog is coming at night-time, absolutely - I haven't been able to find the thing.
''He's as cunning as a monkey.''
He was unsure if there was more than one dog visiting the farms.
''There is at least 2km between the two paddocks on Donny's farms where the dog has killed his sheep.
''I don't know whether it's one or two dogs - we just don't know.''
Cr Gardyne said he had talked neighbours to ensure everyone was aware of the recent attacks.
''We are being more vigilant now, keeping dogs tied up at night, checking more regularly - people are starting to lose patience around here.''
Both farmers were concerned about the dog visiting their farms as it was coming into lambing season.
''It's making a lot of us nervous around here - we want to have a good lambing season,'' Cr Gardyne said.
''You always have some lambs on your farm die but that is different - we don't need a dog killing them as well,'' Mr Nicholson said.