A spate of attacks which has seen cattle and ponies released onto roads could result in somebody being killed, Devon and Cornwall Police have warned.
The attacks on farms in West Cornwall started in 2008 and have intensified over recent weeks with one farm being hit more than a dozen times in just five months.
The incidents usually involve gates and fences being removed or sawn through or holes being cut in water troughs.
As a result, cattle and ponies have escaped on to roads or been left without a water supply.
Grazing on the moorland, near Penzance, has been ongoing for years and some of the fences and gates that have been damaged have been in place for 15 to 20 years.
Sergeant Cara Trott, neighbourhood team leader for the area, said: "Police are investigating these incidents and anyone caught will be prosecuted for criminal damage.
"Whatever the motive, these incidents are criminal and are also extremely dangerous. Cattle and ponies getting onto the winding roads where people are not expecting them could result in someone getting killed.
"One of these farms has been attacked at least 15 times since September alone.
"I would urge anyone carrying out these offences to stop before someone is seriously injured.
"We will do everything we can to find out who is responsible so that these farming families can live without the fear of continually being victimised".