LISTEN: Hear part one of 'The Moose Hunt' as an audio book by pressing play on the video.

The debate will begin again after claims from a former moose hunting guide in Canada that he spotted one of the animals in the South Island's Fiordland National Park.

First released into the park in 1910, the last photographic evidence moose existed in the area was 1952, with many believing they had become extinct.

However, there have been numerous unconfirmed sightings over the decades and DNA evidence from 2001 and 2002 suggests they were still in the area at that time.

ROBIN FRANCIS SMITH, VIA KEN TUSTIN The last known photo of a Fiordland moose, taken in 1952.

Te Anau man Ben Young had no proof he saw a moose on Saturday, but in his mind he had no doubts.

Recently employed by Southern Lakes Helicopters, the 24 year old was a passenger on a flight in the Doubtful Sound area when shocked by what he saw.

Supplied Ben Young claims he saw a moose in Fiordland National Park on Saturday.

"We were flying along a valley and out of the corner of my eye I spied a moose standing in a clearing."

The sighting was only for a couple of seconds but he had a decent look, he said.

The animal had a "big long face" and flicked its head and exposed its big ears.

Barry Harcourt Ken Tustin has been looking for moose in the Fiordland National Park since the early 1970s. He is pictured at Herrick Creek near Wet jacket Arm, Fiordland in 2011.

"Instinctively I was like, f... that's a moose."

It was a cow moose, he said.

Pilot Matt Deaker initially dismissed his claim, but realising how serious Young was, Deaker spun around for a second look, but it was gone.

MAX CURTIS, VIA KEN TUSTIN One of the last verified photographs of a Fiordland moose, taken in 1952.

Like everyone in the Te Anau area, Young said he had heard the talk of moose being in the Fiordland National Park over the years but he had not been a believer.

"I thought it would be unlikely for there to be a moose left in Fiordland in this day and age."

Now he was a believer, given he had seen plenty of the animals while working as a moose hunting guide for Golden Bear Outfitting in British Columbia in 2015 and 2016.

LES MURRELL, VIA KEN TUSTIN Moose standing in Fiordland's Seaforth River in 1927.

"I definitely know what a moose looks like."

People had been skeptical and it had naturally played on his mind, but he believed what he saw, he said.

"It's been on replay for the last few days in my head."

KEN TUSTIN A still from the 1995 timelapse camera. The animal has a curved back, typical of a young moose but not deer.

When landing from the flight he went and saw Ken Tustin who has been chasing moose in the Fiordland National Park since the early 1970s and has written two books and numerous articles on the subject.

After hearing Young's story, a chuffed Tustin said he also believed Young had seen a moose.

"He worked in British Columbia as a hunting guide, the man is bristling with integrity.

"It was good spotting by someone who knew."

The following day the two men flew into the spot where Young made the sighting, on the northern side of Doubtful Sound, but they found no evidence of a moose being there.

Tustin believed it would have been passing through the area.

Any moose sightings nowadays were "extremely improbable" given the fact he believed there would be so few of the animals in such a massive and "gnarly" national park.

Moose were released in the Fiordland National Park in 1910 and were becoming established before red deer swept through the area and changed the food habitat.

Moose couldn't compete but they hung on in small numbers in a habitat not suited to them, Tustin said.

The moose were thought to have become extinct in Fiordland in the 1930s but several were shot in the early 1950s and in later years they were again thought to have become extinct.

Tustin, a biologist, has spent many years in the Fiordland National Park looking for moose over the decades.

Though he had never seen one, he said he had evidence they were there through their characteristic browsing signs which were quite different to red deer.

He did a survey in 1972 which revealed moose still existed through browsing signs and a cast antler, he said.

There had been several reported sighting of moose in the park in 2000 but none were confirmed.

However, Tustin said two DNA records of moose, from hair caught on branches, were confirmed in 2001 and 2002.

"That tells us there were living animals at that time."

The last time he saw sign that moose still existed in the park was in 2015 when he again found browsing sign from that time, he said.

However, there still remained many non believers.

"A lot of people aren't willing to accept they are still there."