The first time Dave Shealy saw a skunk ape, he says, he was ten years old. It was 1974, a few years after his father had come upon a set of footprints left by the creature—an Everglades version of Bigfoot named for its supposedly pungent odor. Dave was out deer hunting with his older brother, Jack, in the swamp behind his house, in what’s now Big Cypress National Preserve, when he encountered the ape incarnate.

“It was walking across the swamp, and my brother spotted it first. But I couldn’t see it over the grass—I wasn’t tall enough,” Shealy says. “My brother picked me up, and I saw it, about 100 yards away. We were just kids, but we’d heard about it, and knew for sure what we were looking at. It looked like a man, but completely covered with hair.”

He and his brother stared at the creature, mouths agape, but almost at the same time, as he tells it, the skies opened and rain poured down. The ape hurried away, into the cypress hummocks scattered amongst the marsh. “Holy crap,” he remembers thinking. “I finally saw this damn thing, and it got away, just like that.”

But the fleeting moment left an indelible impression on young Shealy, who’s now 50 years old. In the decades since, he’s relentlessly pursued skunk apes and seen them, he says, on three other occasions. He’s written a field guide, made TV appearances, continually investigated reported sightings and established a Skunk Ape Research Headquarters on his property, where tourists can learn all about the legendary creature. He bills himself as the Jane Goodall of skunk apes. “I am the expert,” he told a Bigfoot website last year, “the state and county expert on the Florida skunk ape, and have been for years.”

In July 2000, he captured one of his encounters on video. In the grainy daytime footage, shot from hundreds of feet away, the creature spends a minute or so moseying around in a hummock of palm trees. Then, shortly after it begins striding across the open swamp (at about 1:48 in the video below), it breaks into a long-limbed run—as though suddenly aware it’s being watched—escaping into a grove of palm trees.

Shealy notes that, at the time, the swamp was covered by over a foot of water, making the animal’s speed (which he estimates to be 22 miles per hour) impossible for any human to achieve. But it’s extremely hard to watch this video and see anything but a guy in a gorilla suit, hurrying across the swamp:

This impression is especially concerning because, according to any respected biologist, the skunk ape does not exist. “People report seeing this mythical creature from time to time,” says Bob DeGross, a public affairs officer with the preserve. “But there has never been a substantiated sighting of the skunk ape that was verified by National Park Service wildlife staff.” Critics point out that, despite the dozens of unrelated ongoing research projects conducted in the Everglades that use motion-activated trail cameras, no one has ever captured indisputable proof of the skunk ape or come upon the remains of one. “The empirical evidence is extremely weak,” says Sharon Hill, a researcher and columnist for the Committee for Skeptical Inquiry who’s written about Bigfoot, the skunk ape and other mythical creatures. “It’s almost entirely eyewitness testimony, which is the most unreliable evidence you can have.”

Shealy responds by observing that things decompose quickly in the swamp, and that, at 2.2 million acres, it’s the largest area of protected land east of the Mississippi, most of it rarely visited (both true). It’s easy to imagine, he argues, that a handful of reclusive animals could live in it essentially unnoticed and leave virtually no evidence. “I know what I’ve seen,” he says. “For someone who hasn’t come here and put in the time to say otherwise doesn’t really matter to me.”

To a curious observer, all this prompts an important question. Is Shealy a visionary biologist, a mistaken eyewitness, or an enterprising fraud?

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Earlier this year, to try answering this question, I made the trip to Shealy’s property in Ochopee, Florida, an hour’s drive into the Everglades from the west. A few minutes after I arrived, Shealy met me at the research headquarters (which also serves as a gift shop that sells skunk ape T-shirts and shot glasses, a campground, a base for Shealy’s staff of five to give swamp buggy and airboat tours, and a home for his menagerie of ten-foot-long pythons and talking parrots).

“I was out hunting frogs until 4:30 a.m. last night,” he told me, “and I’ve got a whole pile of them that need skinning. Want to help?” A tall, bearded man, Shealy stared at me with an intense gaze, as though waiting for me to freak out, then began to chuckle, saying he was joking, and would be skinning them all himself. After retrieving a sackful of wriggling frogs from the fridge inside his house behind the gift shop, he sat down on his deck, began hacking them apart and started telling me about the skunk ape’s long history.

“Local Native American groups from around here, the Seminoles and the Miccosukee tribe, they’ve known and told stories about the skunk ape for centuries,” he said. Over the past 60 years or so, Floridians of all stripes began reporting that they were seeing the creature. (A similar pattern happened in the Pacific Northwest, where indigenous beliefs in the Sasquatch eventually led to the skunk ape’s better-known cousin, Bigfoot.)

In one of the earliest well-publicized sightings, a pair of hunters claimed the ape invaded their camp in 1957. It’s unclear who coined the name skunk ape, but it appears to have surfaced sometime during the '60s. During the 1960s and '70s, the period when Shealy had his first sighting, more and more reports trickled in, as far north as the Florida panhandle, but most often in the Everglades. The skunk ape eventually attracted mainstream attention, including a bill introduced (but not passed) in the Florida legislature in 1977 that would have made it illegal to “take, possess, harm or molest anthropoid or humanoid animals.” It was around this time that Shealy, a teenager, spotted evidence of the creature for the second time, in the form of enormous four-toed footprints left at night near his hunting camp deep in the Big Cypress interior.

Occasional sightings continued for years, and the skunk ape hit the news again in 1997, when passengers on a tour bus traveling through the preserve claimed they spotted the animal. “This was 30, 40 people, all saying they saw the same thing,” Shealy says, “a seven-foot, red-haired ape.” After decades of idle interest in the creature, he decided to get serious about finding it, baiting the area with lima beans (the story goes that the omnivorous apes loved the legume). He repeatedly found the beans missing in the morning, along with tracks left in the night. Then, just two miles away, a pair of local residents—Jan Brock, a real estate agent, and Vince Doerr, chief of the Ochopee Fire Control District—separately spotted a large, hairy biped minutes apart while driving through the preserve one morning in July. “The thing just ran in front of my car,” Brock told me when I called her after my visit. “It was shaggy-looking, and very tall, maybe six-and-a-half or seven feet tall.” Doerr, who told me that he’d never believed in the skunk ape before seeing it cross the road about a half mile in front of his car, snapped a photo of it just before it vanished into the swamp.

“I’m going to spend the next six months looking for this thing,” Shealy remembers vowing at the time. “I’m not going to do anything else. Every day I’m going to get up and go looking and keep doing this until I see it.”

Shealy set up a few tree stands on his 30-acre property, and spent the next year sitting in them, baiting the area and watching for the skunk ape, or trekking across the Everglades, trying to find the creature’s trail. Finally, on September 8, 1998, he says, he was rewarded with his second sighting. Perched in a tree and half asleep, “I heard something splashing in the water: splash, splash, splash,” he told me. “At first, I thought it was a person, but then from around 100 yards away, I saw it coming toward me. It was a skunk ape, the same as I saw when I was a kid.” As it walked by, unaware of being observed, he shot several photos of it, watching it disappear into the nearby tree hummock. Later, he returned and made a concrete cast of its footprint, which still sits in the gift shop.

After he finished skinning the frogs, Shealy fried me a few pairs of legs for lunch and told me about his two most recent sightings: Once in 2000, when he filmed the video clip, and the latest in August 2011, when he was picking saw palmetto berries in the swamp and was startled by an unforgettable odor. “Right away, I could smell it—kind of like a wet dog and a skunk, mixed together,” he said. It emerged from behind a palm frond, spotted Shealy and bolted, leaving no evidence.

He still searches for the skunk ape, concentrating his work mostly in March and April—when the dried-out swampland allows for easier hiking and preserves tracks better—and investigating the dozen or so sightings that are called in to him annually. He’s boiled his findings down into a field guide, available for $4.95 at his gift shop (the skunk apes stand six to seven feet tall, spend about half their lives in the trees, and might pick up their awful odor from their time in underground alligator caves, it says), and mapped the most recent sightings. He was even filmed for an episode of “Finding Bigfoot,” the Animal Planet reality show, although he was infuriated when the producers balked at the logistical difficulties of traveling into the swamp to investigate a sighting and asked him to “fake it” in his backyard instead.

Of course, many people question Shealy's authenticity—something that weighed upon me as I ate the lunch he’d made for me and politely listened to his claims. Apart from the sheer unlikeliness of the skunk ape’s existence, critics point out that Shealy openly profits from the supposed animal, selling tchochkes and offering swamp tours. In 2000, he even applied for a grant from the Collier County Tourism Development Council to fund his research, and some remarked upon the conveniently timed release of his skunk ape footage shortly before the hearing, along with the dubious creature in the video. “The skunk ape, which bears a striking resemblance to a guy in a monkey suit, was filmed walking across a clearing,” Naples Daily News columnist Brent Batten wrote at the time. “Anyone who previously doubted the existence of the skunk ape should now be converted. The same way that anyone who doubted the existence of flying saucers carrying evil space aliens would have a change of heart after seeing Plan Nine from Outer Space.”

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The belief in mythological animals might be as old as humanity itself. Nearly every culture’s folklore contains at least one imagined creature in its folklore that has no place in modern science. You’ve likely heard of the Loch Ness Monster and Bigfoot, but there are thousands of others. In the Philippines, people have long feared a vampire-like animal called the Aswang. British folklore prominently features supernatural black dogs associated with death that roam the countryside. Other places have aquatic monsters, enormous worms or massive, lizard-like demons.

It’s easy to imagine how, in the days when much of the planet had yet to be explored and catalogued, you might have reasonably believed in the existence of any of these beasts. But in the present day, when every square mile of the earth’s surface has been photographed by satellites, and scientists have identified 1.3 million species (with mostly plants, tiny animals and microbes remaining to be found), how could you still believe in a lumbering, seven-foot-tall ape, hiding out in one of the most well-studied countries on the planet?

“In the context of the modern world, where truth is provided by the consensus of mainstream science and medicine, I think many people feel disempowered,” says Peter Dendle, a professor at Penn State University who’s written extensively about folklore and cryptozoology (the search for cryptids, animals that aren’t recognized by the scientific community). “I think cryptozoology serves as a means of staking a line, and saying, 'You scientists don't know everything. There are still truths out there to be discovered.'” Cryptid enthusiasts, he’s found, are disproportionately male and often share a number of outsider traits that I couldn’t help but see in Shealy: a distaste for authority, a rugged connection with the outdoors and a hearty sense of individualism and self-reliance.

Psychologists, meanwhile, have observed an overlap in people who believe in cryptids and those who suffer from psychological conditions including ADHD, depression and even dissociation. These underlying disorders, it’s speculated, increase the chance that people will incorrectly interpret an otherwise explicable real-world experience. In other words, a psychologically stressed or unstable person might catch a brief glimpse of a deer or bear far away in the woods and become certain it’s a bipedal hominid heretofore undiscovered by science.

On an individual level, it’s easy to see how a one-time mistake like this could persist. “These people invest time, effort and money into this activity, which they’re passionate about,” Sharon Hill, the skeptic, told me. “They have a sense that they’re doing something with a higher purpose. Maybe they’ll be the one to finally solve the mystery, and they’ll become famous and respected—something that they might not have in their life otherwise.” This sort of belief is self-reinforcing: Admitting that a cryptid is nonexistent would mean giving up the years they’ve devoted to the search thus far. The only option is to keep looking, certain that indisputable proof is just around the corner.

Any of these explanations should imply that, when I followed Shealy into the muddy swamp after lunch—to the spot where he’d spotted the skunk ape in 2000—I shouldn’t have had even the slightest expectation that we’d see one in the flesh. But as we walked along the meandering trail, listening to the drone of insects and the squawking of birds overhead, part of me held a faint hope that he wasn’t crazy or self-delusional, that he really had seen the creature and that there was a tiny chance we would too. “In this digital age, the world suddenly feels very, very small,” Dendle, the folklore expert, told me. “There’s a sense of claustrophobia, and a loss of wonder. Cryptozoology is a way of refusing to have the last piece of the unknown taken away—of imagining there’s something bigger than us out there.”

There aren’t many rational reasons to believe the skunk ape might be real, but after doing some digging, I was able to find exactly one: The line between real animals and cryptids, it turns out, is much messier than you might imagine. Carl Linnaeus’ 1735 landmark text of modern biology Systema Naturae listed the pelican, antelope and narwhal as cryptids. As recently as the start of the 20th century, the Komodo dragon, the giant squid and the okapi were thought to be cryptids, before the Western scientific establishment changed its mind in the face of indisputable evidence: the animals' dead bodies.

This still goes on. Dozens of new mammal species have been discovered since the start of the 21st century, although they’re generally less extraordinary cases, often the result of subtle taxonomic changes. Perhaps the most well-known of these is the olinguito—the first new carnivore discovered in the Americas in 35 years—which was announced in August 2013. The small, arboreal animal had eluded the scientific community for all of modern history, confused for its close cousin, the olingo. That the olinguito was overlooked is all the more remarkable because thousands of the animals live in the cloud forests of Colombia, dozens of their skulls and furs have been preserved in museum collections, and one individual olinguito actually lived in the Smithsonian’s National Zoo for a few years in the 1960s.

“I think that there’s just a lot out there that most people don’t know about, that we really don’t understand about the world,” Shealy told me as I followed him down an overgrown path into the swamp at the rear of his property. I couldn’t help but recall what Kristofer Helgen, the National Museum of Natural History zoologist who discovered the olingutio, told me just before the press conference announcing it. “The discovery of the olinguito shows us that the world is not yet completely explored, its most basic secrets not yet revealed.”

Some Bigfoot believers argue that the creatures could be a tiny relict population of an ape species thought to have gone extinct millions of years ago, such as Gigantopithecus or Paranthropus. If so, it certainly wouldn’t be the first species to be resurrected. One, the Chacoan peccary—a wild pig-like mammal native to South America—was initially known only from fossils found during the 1930s. Then, in 1971, scientists realized thousands of the animals were alive and well in the Chaco region of Argentina. During the intervening decades, biologists had been certain that the peccary was long extinct. Local residents, meanwhile, were aware of the animal’s existence the entire time.

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