Residents reported seeing two brown dogs ravaging livestock at two Carwoola properties over the Australia Day long weekend.

One of the dogs has since been killed and its microchip scanned while the location of the other dog is unknown.

One of the property owners affected was sheep farmer Danny O'Sullivan. He said it's been about a decade since the last attack.

"These were savage looking dogs. I don't blame the dogs, I blame the people who are supposed to be looking after them," he said.

"These dogs can attack anybody, they're lethal weapons. It's a lack of responsibility by the owner and a lack of respect towards other people."

Mr O'Sullivan said of his 200 sheep, 10 are dead and another four missing. Some of Mr O'Sullivan's ewes were supposed to birth lambs next month.

"Usually domestic dogs attack the rear end of the sheep but these blokes where going for the face and ears," he said.

"There were a couple of my sheep with their ears ripped off. The sheep were all over the place, some had been driven through the fence."

Nearby at Kankinya Alpaca Stud, owners Glen and Wendy Riley said the loss of two rare black suri males was a "severe blow" to their breeding program.

Mr Riley estimates the financial loss to be worth about $6000 for both alpacas, one of which had won ribbons at the Canberra Show and Goulburn Show.

"One of the males had great breeding and a lot of great potential as a future herd sire," Mr Riley said.

"He was a great asset to me. I've lost a breeding sire and that's been a great nuisance as well as the $5000 loss for him."

Mr Riley said he had experienced about five dog attacks on his property in the last two decades. The last attack was about five years ago.

He described this most recent attack as the worst.

"The champion [alpaca] had been disembowelled. He had been very severely damaged. He probably put up a fight whereas the younger one was not as big and strong. I think he died of blood loss," he said.

"These were big muscular dogs. They were thickly built with a big head, big face and jowly, lots of loose skin around the face. They looked to me to be a mastiff or a bull mastiff."

Mr Riley said he hoped the attack would serve as a reminder for owners to keep a check on their pets.

"When you've lost alpacas and you haven't killed the dogs. There's always a chance, in your mind, that they'll come back and kill or chase the rest of the herd," he said.

"That night I didn't get a wink of sleep, I was just worried of the dogs coming back."

A Queanbeyan City Council spokesperson would not comment on the case as rangers were still conducting an investigation.