Department of Conservation Wakatipu area manager Greg Lind is confident the "idiot" who tagged various structures the length of the Routeburn Track last month will be apprehended and prosecuted.
Mr Lind said yesterday about 40 felt pen tags featuring the word "Rowdy" had appeared on wooden and painted structures along the 32km track.
It was the first time anyone had vandalised the track, one of New Zealand's Great Walks, which is located in the Fiordland National Park, a World Heritage Area.
The same tag had also appeared in Franz Josef and at Wanaka, he said.
The person responsible could be charged under the National Parks Act 1980 with wilfully damaging or defacing a fence, building or apparatus; or unlawfully altering, obliterating, or defacing signs and marks, including boundary marks.
The maximum penalty under the Act is three months' imprisonment or a $2500 fine.
DoC would likely seek reparation from the person responsible to cover the cost of the clean-up, which would be significant.
"There's quite a cost attached to it - it's either sanding or replacing wooden structures and there are quite a lot of painted structures which will have to be cleaned off using solvent.
"It's major staff time and the track is going to be winterised soon ... it's going to be an early spring job and several days' work involving helicopters."
He said there was "a steady level of anger building up both internally and externally at the moment".
Information received by DoC led them to believe the offending likely occurred about April 19 and, because trampers booked to walk the track, DoC staff had the names of everybody on the track at that time.
"We'll know more [today].
"Our visitor centre staff are trying to identify it ... staff are contacting everybody on the track during that period. We've got some very strong leads."