Prehistoric footprints made by a moa in Matata are being threatened by trophy hunters.

A rock dislodged by last year's flood in Matata revealed 300,000-year-old moa footprints - but it already bears the marks of vandals who have tried to chisel off pieces of the historic impressions.

The prints were discovered by Matata resident Robert Butler.

Four months after finding the rock, Mr Butler finally told scientists working in the area about his find. "Things just snowballed from there," he said.

Hidden from view for the better part of 300,000 years, the moa prints had been covered with a layer of volcanic ash, preserving them until the devastating floods of May 2005.

"The stone would then have broken free and floated down the gully with the footprints facing up," Mr Butler said.

"The stone was covered in light-brown clay and somebody has removed the biggest prints. They have also tried to chisel off one of the prints in the middle."

Auckland University geologist Dan Hikoroa is desperate to preserve the prints and has called on people to leave the rock alone.

He said the moa tracks were a rare find.

"Why don't we preserve it so everybody can enjoy it? We hope that common sense will prevail and that the footprints will not be destroyed."

Finds of moa tracks were reasonably common in the late 1700s and early 1800s, he said. But during the last 100 years they have been very rare.

"This find is highly unusual in that it bears 12 prints and you can make out how the moa has walked, where it has put one foot after the other," said Dr Hikoroa.

"It's amazing we found them at all."

The university was talking to iwi about how to best deal with the find, Dr Hikoroa said. "We'll be trying to date the layer of volcanic ash that has been above the prints."

The area where the rock came from was sacred to Maori and Dr Hikoroa hoped people would look after the rock, saving it from further destruction.

The layering effect that preserved the moa prints was created by a volcanic eruption, probably from the Taupo or Rotorua area, which had wiped out life in the vicinity.