ntnews - Forget UFOs and the Yowie - the biggest Outback mystery is the Territory Tiger.
The grainy still above was taken from footage filmed in the 1990s by Territorian Jan Donovan.
Author Rebecca Lang said the large, sandy cat appeared to be of "considerable size", and could be the descendant of escaped circus cats.
Ms Lang and co-author Mike Williams have spent the past five years compiling reports of sighting and collecting photos and video of large cats that resemble leopards and pumas for their book Australian Big Cats: An Unnatural History of Panthers.
The earliest account was from 1883 by SA explorer Charles Winnecke. The journal of his exploration on the WA-NT border says Winnecke came across a "wild cat of an extraordinary size".
"The brute was nearly as large as a leopard," he wrote.
Ms Lang said these cats had a lifespan of 20 years - but the sightings have continued for 150 years.
"We know the earliest circus menageries started up around 1850, so it's conceivable that the odd circus cat could have ended up in the bush," she said.
"Transport arrangements were notoriously dodgy back then and escapes happened all the time."
Photo: Big Cats Roam Aussie Northern Territory?