They had released a statement say that ministers on jaunting cars, horseback and in open boats would send out the clearest message - rural Ireland was open to visitors again after the foot-and-mouth crisis.
"It's no big deal getting some of them on jaunting cars and boats.
"We will be fitting them to a small number of the jaunting cars initially and if it is successful we hope to extend it next season.
"We have had discussions with the jarveys as there are particular traditional jaunting cars unique to Killarney and we need to a get a design that works with them," the spokeswoman said.
"With the design of the traditional jaunting cars in Killarney, these devices could cause the horses to kick out or bolt and there could be mayhem.
Council chairman Sean Counihan said the problem in the town centre had been alleviated this year by the opening of the aptly named Inner Relief Road for jaunting cars.
The NPWS said up to 66 jaunting cars operate in the park and they had been repeatedly reminded of the new requirement since the beginning of June.
The NPWS apologised to users of the park and said it hopes the jaunting car operators will change their mind.
Park officials checked to see if the horses had their nappies on and noted the jaunting
car numbers and the jarveys are expected to get written warnings.
He also warned that the nappies may not be compatible with the jaunting
cars, putting their traditional and attractive design at risk.
Stepping up in distance today, Jaunting
will have the assistance of Angela Crowley, and gets the vote to beat fellow three-year-old Darbela and the smart four-year-old Musical Mayhem, who appears to have a very tough task at the weights.