Erard Louw said to the Cape Times he had been thinking of new ways to protect his flock after 27 sheep and 13 lambs were stolen from his Durbanville farm 10 days ago.

He tied a mechanism to four sheep in separate flocks, which called his phone as soon as they started running, normally indicating they were being stolen or had slipped through a fence.

"As they run, it gives me a phone call and says 'sheep one' or 'sheep two' and so on, so at least I know where to start looking, because the farm is 750 hectares."

His sheep "cellphones" had to date resulted in a stock thief being arrested.

Western Cape chairman of the Red Meat Industry Forum, John Durr, said winter saw a rise in theft as the rain wiped out all spoor and fewer daylight hours made it easier for thieves to hide.