Dozens of sheep belonging to Bangor University’s research centre have been stolen from the Carneddau mountains.
The university's centre at Henfaes, near Abergwyngregyn in Gwynedd, has been targeted.
Police believe the offenders would have had specialist knowledge and would also have known the local area.
North Wales Police said tweeted: “Forty eight sheep belonging to Bangor University’s research centre at Henfaes, Abergwyngregyn have been stolen from the Carneddau mountains.
"The offender would have had to know what they were doing and know the lay of the land. Any info? Please help us with our investigation.”
Henfaes is Bangor University’s field research centre and also a commercial sheep farm.
The livestock system runs alongside cutting-edge experiments on land that goes from sea level to amongst the highest mountains in Wales, all on one farm.
If you have any information please contact North Wales Police on 101
