Two tree surgeons from Gloucestershire claim to have seen a big cat "the size of a labrador" dog prowling around.
John Vine and Nick Cole said they were working on a willow tree at Churchdown near Gloucester when they saw the animal come out of the thicket.
Mr Vine, 49, said at first he thought it was an ordinary cat until it passed a post and he saw the scale of it.
Big cat expert Frank Tunbridge, 60, who has 25 years experience believes the men's sightings are "credible".
He thinks the reason behind an increase in sightings at this time of year are due to the breeding season.
"I've had 12 this year that I am investigating in the Stroud Valley. As they are breeding they take more risks and go out looking for a mate.
"They are non-aggressive and some have lost their fear of people."
Mr Vine described the cat as having a shimmering coat, like gloss paint and a black tail as long as itself.
"The tail was what struck me most. It seemed as though it was floating, curled up at the end and hovering in the air," he said.
The pair claim to have seen the cat on a dirt track neat the Highgrove Estate in Tudor Mead on Monday morning.