"Remove keys from ignitions, lock them up or store them securely."
Director of Rotorua-based excavating company Sherlock Contracting, Ray Fleming, said this was the first series of earthmoving equipment thefts he had heard of in the Bay of Plenty.
Sherlock Contracting has five CAT diggers.
"They all have GPS in them so we can monitor where the machine is and what it is doing at all times from a website," Fleming said.
Despite the GPS system, he said digger security was a challenge because CAT diggers had a "one key fits all" system.
"The key for your digger will also work in your workmate's digger, your brother's digger, your boyfriend's digger, any of them unless the isolation switch is turned off."
Perks encouraged members of the public to contact police immediately if they saw "unusual activity with regard to earthmoving equipment".