Rustlers appear to be operating in the Tarras area, with 60 top merino breeding ewes with a combined value of $24,000 taken from a property on Jolly Rd.
Senior Constable John Chambers, of Cromwell, said Malvern Downs property owner Robbie Gibson went to check a flock of 94 ewes on Wednesday and discovered only 34 were left.
The ewes had gone missing from a paddock during the past three weeks.
Mr Gibson said he had "talked to the neighbours and they looked everywhere, and I looked everywhere, but we couldn't find them".
He concluded they had been rustled and informed police.
The sheep which were mostly young ewes, have the familiar "top-knot" which Mr Gibson leaves on to make them easy to distinguish, and they were all tagged with a brass tag and two plastic ones, indicating their worth as breeding ewes.
The paddock they grazed can be seen from State Highway 8, and from SH8A - from Tarras to Wanaka.
Mr Gibson's father, Bill, was the first to breed polled ewes (with no horns) in 1950.
"That's 58 years of genetics there. They are very valuable and are becoming more popular than those with horns as they are easier to manage, they don't fly strike and they don't get stuck in the fences," Mr Gibson said.
Police would like to hear from anyone who saw any unusual activity in the area.
This theft follows the disappearance of about 1800 merino ewes and lambs worth $130,000 from a Queensberry farm block. Detective Dave Evans, of Wanaka, has begun an investigation into the rustling.
