Deep in the swamps of Florida, something is stirring. Witnesses to its haunting presence speak of howls in the night, unexplained footprints in the mud and glimpses between the trees of a fiery-eyed creature that reeks of death.

Now, a 30-strong team from The Bigfoot Field Researchers Organization (BFRO) has embarked on an expedition to try to flush out the mighty skunk ape - the Sunshine State's answer to the abominable snowman. They have thermal imaging equipment, video cameras and microphones poised to capture the secrets of the hairy, 7ft-tall hominid with yellowing teeth and dubious personal hygiene.

“We have to keep these expeditions low-key because unfortunately the subject is still a little stigmatised,” sighs Matthew Moneymaker, head of the BFRO, as he drives to the expedition's secret base camp in southwestern Florida.

“When people don't take this subject seriously, we don't even call it scepticism - it's ignorance. People only know about this stuff from tabloids ... they've created this “other Bigfoot”, a kind of cartoon concept rather than a rare species. They don't understand how creatures could live and die in the woods without us knowing.”

Purported sightings of the Southernmost Bigfoot, as it is dubbed, prowling in and around the Everglades wetlands date back decades. There are claims of it lurking behind trees and crouching in roadside ditches, trailing a foul odour akin to a mixture of rotten eggs, mouldy cheese and dung on account of its penchant for camping in disused alligator nests.

It is strangely camera-shy - although, in a quirk of fate eight years ago, one happened to lunge past a campsite at Ochopee, 35 miles southeast of Naples, where self-appointed expert Dave Shealey runs the Skunk Ape Research Headquarters and souvenir shop selling ape-man T-shirts and copies of his Everglades Skunk Ape Research Field Guide. A companion clutching a video camera managed to shoot 15 seconds of fuzzy footage showing the pungent primate trotting through the long grass.

The mystery deepened in 2000, when the Collier County Sheriff's Office received two photographs from a local homeowner, showing an ape-like creature shambling around her rural back garden. “Is someone missing an orang-utan?” she asked.

With hundreds of reports of Bigfoot sightings all over the US, Moneymaker's $300-a-head expeditions are popular with fans of cryptozoology, the study of creatures whose reported existence is unproven.

Guns are banned from the trips. But for the faint-hearted, knives, machetes, spears and Tasers are permitted, lest the group runs into a Bigfoot that hasn't read the rules.

In 2005, Scott Marlowe, a Florida cryptozoologist, claimed to have been hit on the head by a skunk ape armed with a stick; and in 1975 another was seen tottering along a roadside with an armful of stolen corn.

Others tell the tale of a group of huntsmen who were startled one night by a clumsy-footed skunk ape falling through the roof of their log cabin. Not even stopping to brush itself down, the panicking apeman dived through a window and lumbered off.

Moneymaker resents those who say such stories are just monkey business.

“A lot of people believe in Jesus,” he says. “But they don't have to see Jesus running across the road in front of their car or find Jesus's tracks to believe.”

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