Garden makeover programmes are being blamed for an increase in the theft of ancient artefacts from Dartmoor.
Ancient crosses have been disappearing from the moor
Electronic tags are being used to help protect valuable stone crosses and troughs in the area.
Officials from the Dartmoor National Park Authority say the popularity of TV garden series could be triggering more thefts.
New security measures follow a recent attempt to remove a granite cross.
Jane Marchand, an archaeologist with the park authority, said: "Unfortunately we have lost a number of artefacts and there has been a recent attempt to remove a cross from the moor.
"It is hard to say who is to blame, but I think it's an interest in garden ornaments from TV gardening shows.
"If you look through auction sales they very often have granite objects for sale."
The new measures will mean any stolen artefacts can be traced using an electronic scanner.
A microchip, about the size of a grain of rice, is inserted into the granite so it is invisible.
Ms Marchand said: "I think it's very sad that we have to do this.
"I can't understand how anyone could think of removing these things.
"But there is some strange irony that we are using the latest technology to help protect these very ancient artefacts."