The expedition set off this week after yet another sighting of a big cat in the UK: six lambs were mauled to death on a farm in near Carmarthen. Locals reported seeing a puma in the area.

Mike Thomas, an expert on exotic animals and director of Cornwall's Newquay Zoo, told the BBC he is convinced big cats are on the loose in west Wales.

"We have been investigating them (big cats) for five years, mostly in the west country in Bodmin where it is called the Beast of Bodmin.

"We are still looking and that's why we are going to Wales. We have been asked if we could investigate the existence of the so-called puma or panther or beast in Carmarthen."

Tales of mysterious beasts abound in the UK, with sightings of large puma-like cats reported from Scotland to Kent.

Little physical evidence was found until a 14-year-old boy came across a skull with large fangs in the River Fowey on Bodmin Moor in Cornwall - but experts at London's Natural History Museum proved the skull was that of a panther, killed overseas and dropped on the moor.

Last year, a 20-second video of a black, three-and-a-half foot animal roaming mid-Cornwall was released.

Mr Thomas hailed the footage as the "best evidence yet" of big cats roaming Bodmin Moor.

There have been about 60 other sightings of big cats in the area since 1983.

Fleeting fashion

While there are no big cats native to the UK, one or more may have escaped from captivity.

Mr Thomas said: "Many people kept these animals as status symbols, a bit like we collect antiques now, in a way."

He said that it became onerous to keep the animals when the laws on dangerous animals changed in 1976.

"It was pretty costly and they had to abide by certain regulations. So they threw them out on the heath where there was plenty of food for them."

The truth is out there

Like Agent Scully picking over a corpse to track the existence of aliens in The X-Files, Mr Thomas and his team will examine the mauled lambs.

"We can certainly tell (if it is a big cat) from the kill. A typical cat kill would be a bite to the back of the neck and that would sever the spinal chord.

"And then the way that they eat, they tend to strip their prey. Generally they drag their prey as well and bury it with twigs or whatever."

Farmer Yvonne Edwards, is convinced there are pumas on the loose, and said at least two of the big cats had attacked her lambs.

"It would have taken at least two, if not three, pumas to make this mess. Three lambs were reduced to skeletons and others were ripped to pieces."

Naturalist Terry Hooper - drafted in to examine plaster casts of paw prints taken at the scene - believes one set of prints belonged to a dog, but that the others found were definitely those of a young puma.