SHEEP duffers have been stuffing hundreds of jumbucks in their tucker bags in the Mount Mercer area north of Geelong.

Soaring lamb prices have been blamed for the thefts, with more than 20 reports of missing sheep and thefts in the past seven months, the Geelong Advertiser reports.

Police said there was no evidence at this stage the thefts were linked.

Bacchus Marsh police Senior Detective Brian Malloch said thieves had got away with 100 lambs and ewes in one raid, probably by loading them onto a truck.

Sen-Det Malloch said sheep were not branded, but they had an eartag which was more easily removed and replaced.

"It's a bit like stealing a car change the number plates and hope for the best and no one notices," he said.

Sen-Det Malloch said many of the smaller incidents might merely have been sheep wandering off on their own.

"It's very hard to say it's 20 incidents, when it's just 20 reports," he said.

Colac police said there had been no sheep thefts in their area. In 2007 nearly 300 ewes were stolen from a paddock at Skipton.

But Colac-based Charles Stewart and Company livestock salesman Jamie McConachy said yesterday there had been a lot of thefts in the area that had not been reported.

"I dare say there have been stock thefts in the Colac area as well in actual fact I know there is and obviously they haven't been reported," he said.

"It's been a problem a big problem. When lambs are making a couple of hundred dollars a head, if the thieves come in and take 15 or 20 it's a considerable pay packet.

"It's a big loss for the producer."

Lismore farmer Ed Calvert said yesterday he had lost 100 or more sheep to thieves mostly lambs.

"They were unmarked and they were catching them at night," he said.

"There were no dead lambs lying around or anything they had just been taken."

Mr Calvert said he had spoken to a lot of farmers and thefts appeared to be fairly widespread.

"The worst thing about it is they are very difficult to catch," he said.

Read more on the Geelong Advertiser.