In some circles, it's considered the pet animal of alien visitors. Others believe it's the result of a NASA experiment gone wrong. Still other conspiracy theorists say it's the source of the HIV/AIDS virus.
But while stories about the mysterious chupacabra have spread far and wide, real information about a curious-looking creature with that name is virtually nonexistent.
As with Bigfoot, the Loch Ness monster and the other bizarre beasts in urban legends, the tale of the chupacabra thrives on the first-person accounts of people who claim to see it -- and the very active imagination of the public at large.
Now Benjamin Radford, a paranormal investigator and managing editor of Skeptical Inquirer magazine, says he can put the story of the chupacabra to rest. After five years of digging, he said he's uncovered the roots of the mystery.
Chupacabra Phenomenon Dates Back to 1995, Author Says
In his new book, "Tracking the Chupacabra: The Vampire Beast in Fact, Fiction, and Folklore," Radford lays it all out, showing how one woman's story turned into a global sensation.
"What really interested me about the chupacabra is that it's a vampire, unlike Bigfoot, unlike the Loch Ness monster, the moth man, the New Jersey Devil," he said. "Whatever beasties people have laying around, this one sucks blood."
Stories of the chupacabra, which means "goat-sucker" in Spanish, spread mainly in Latin America, the southwestern parts of the U.S. and other Spanish-speaking areas. Many people assume that the phenomenon goes back hundreds of years, Radford said, but it's really only about 15 years old.
"It's such a recent monster," he said. "It only dates back to 1995."
Prior to that, other researchers found a reference to a chupacabra in the 1960s TV show "Bonanza," but it referred to a whippoorwill bird that folklore suggested sucked milk (not blood) from goats, he said.
First Chupacabra Account In Puerto Rico
It wasn't until the summer of 1995, in Puerto Rico, that people started connecting the name "el chupacabra" with the fearsome four-legged creatures thought to prey on other animals.
That's when Madelyne Tolentino, a housewife in the village of Canovanas, reported the first sighting to the local news, Radford said. After years of investigating and tracing the story of the chupacabra backwards, he said he finally reached her through Facebook, via her ex-husband, and interviewed her last year.
Radford said the creature reportedly spotted by Tolentino was about four feet high with oddly-wide, dark eyes, thin arms, three fingers and stood on two legs. She also said it lacked ears, had small air holes instead of a noise and feathery spikes on its back.
"She said she only saw it for a minute or two, it wasn't for very long," he said. "But she gave a whole description of the number of toes, eyes, an alien appearance, the teeth and she even noticed that it had no genitals."
After appearing on the local news, her story was picked up by UFO researchers, who spread the story on the Internet, where it went viral.
Did 'Species' Movie Inspire Woman's Eyewitness Story?
"From that point, it leapt from the suburbs of San Juan, Puerto Rico," he said.
When the story aired on "Cristina," a Spanish-language equivalent of Oprah Winfrey's show, he said, it became an even bigger part of the global consciousness.
"Almost immediately, everywhere the show aired, suddenly people were seeing the chupacabra," he said. "If you go back and look at it, the media actually played a very strong role in promoting the chupacabra."
But Radford said that when he spoke with Tolentino during his research for the book, he found her detailed description of the chupacabra was too detailed. In fact, he said, it was "suspiciously detailed."
And, during their interview, Radford said, Tolentino revealed that just weeks before her mysterious sighting, she had seen the hit science-fiction movie "Species," which features characters that look much like the chupacabra of her memory.
"To me, that was the smoking gun," he said. "It can't be a coincidence that this chupacabra that's now popping up around the world just happens to look exactly like the monster in this sci-fi film."
Another Category of Chupacabra Emerged in Mid-2000s
But Radford said he doesn't think Tolentino is a liar or hoaxer, just that she confused something she saw in a movie with something she saw in real life.
And he said that considering the context, it's even more understandable.
"This didn't occur in a vacuum," he said. "At the time in Puerto Rico, there was already a pre-existing belief that something weird was going on. ...People were finding dead animals."
Now, he said, it's clear that those dead animals didn't die mysteriously but after attacks by dogs, mongooses or other animals. At the time, however, "Her description put a face and form to a previously amorphous and vague sense of something being weird."
Radford said that a separate category of chupacabras started appearing in southwestern parts of the U.S. and other Spanish-speaking regions of the world in the mid-2000s, but could be explained away by DNA evidence (although that hasn't stopped reports from popping up every so often).
In those reports, the so-called chupacabras are reported as hairless, coyote-like creatures that stand on four legs. But Radford said that forensic science and DNA evidence has shown those to be mangy canids – dogs, foxes and coyotes with a skin disease called sarcoptic mange.
It's a contagious skin disease, caused by mites, that affects many dogs and results in hair-loss, he said. They tend to be spotted more in warmer climates because they die off in colder weather.
Next time you hear a report of a chupacabra sighting, Radford says you should examine the evidence and not blindly believe what you read. But he also says that despite his book -- and the case he says he's solved -- people will continue to tell the tale of the mysterious chupacabra.
"It doesn't matter what I write, it doesn't matter that I solved this. People are still going to see a weird hairless thing and someone is going to call it a chupacabra," he said. "I think the bigger answer is that people like mysteries. And the idea of a Hispanic beast that sucks goats' blood is kind of cool -- it captures the public's imagination."