Police are joining forces with farming unions to issue warnings after a series of sheep thefts across north Wales.
Since September, more than 70 animals have been taken in incidents stretching from Dolgellau in southern Gwynedd to Ruthin, Denbighshire.
North Wales Police said they were stepping up patrols in rural parts of south Denbighshire.
But along with unions, they are also urging farmers to remain vigilant.
District inspector for south Denbighshire Dewi Roberts said: "These are serious offences which can have a significant impact on the livelihood of the victims and the rural community at large.
"Police officers will be stepping up patrols in the rural areas in south Denbighshire and making vehicle stops in a bid to provide reassurance to members of the farming community."
Two of the latest incidents include a report received at the beginning of November that 25 sheep had been taken from farmland south of Dolgellau. In October, 33 sheep were reported stolen from a field at Efenechtyd, Ruthin.
As well as increasing police presence, officers have been to the Ruthin livestock mart to highlight the issue.
The force is also making use of the Farmwatch initiative to help, the rural equivalent of neighbourhood watch projects.
NFU Cymru warns that sheep rustling seems to be on the increase and is still a serious problem for Welsh farmers.
NFU Cymru Ruthin branch chairman, Gareth Jones said: "It is deeply worrying for livestock farmers that this type of activity is on the increase and is starting to form an upward trend.
"We now have a significant number of sheep thefts that have occurred throughout the county and it is unlikely that Denbighshire is alone in facing this problem and the warning goes out to livestock farmers around the country to be on their guard."
The Farmers' Union of Wales' Marian Jones added: "The recent spate of thefts in the Ruthin area is a concerning development.
"Farmers should remain vigilant, and I would urge anyone who sees anything suspicious that may be related to this or other rural crimes to take down any relevant information such as vehicle registration numbers and report the incident immediately to the police."