JOE PALCA, host:
This is SCIENCE FRIDAY from NPR. I'm Joe Palca, and Ira Flatow's away.
This weekend, in case you hadn't noticed, is Halloween, the time of year you're guaranteed to hear about the supernatural and the scary. But in Central America and some parts of Texas there's an urban legend, a scary urban legend, that people have been talking about year-round. It's the tale of the chupacabras, or goat suckers.
It was first reported in Puerto Rico in the mid-'90s, with stories of livestock being ravaged by a mysterious half-dog half-bat with - creature with gray scaly skin and no hair. Hmm, that's, yeah, that would be scary.
The stories began spreading across Mexico, and now sightings of the beast are coming out in Texas. But despite all the superstition and speculation, scientists are coming forward with a rational explanation.
Here to dispel the myth of the chupacabras is my guest, Barry OConnor. He's a professor and associate chair of the Department of Ecology and Evolutionary Biology and curator of the Museum of Zoology at the University of Michigan in Ann Arbor. Barry OConnor, welcome to the show.
Dr. BARRY OCONNOR (University of Michigan): Thank you very much.
PALCA: And if you have questions for Dr. OConnor, you can give us a call. Our number is 800-989-8255. That's 800-989-TALK. If you're on Twitter, you can tweet us your question by writing the @ sign followed by scifri.
So first question: How did you get involved in this?
Dr. OCONNOR: Well, I'm kind of an expert on the big group of mites that causes mange, and what we see in the photographs that are purportedly chupacabras are clearly mange-infested coyotes or dogs. These are animals that have a pretty severe case of these parasitic mites that typically causes them to die ultimately, but they do get really ugly before that happens.
PALCA: Okay, so now I'm a little confused. How do you get something that people swear is a half-dog, half-whatever, half-bat, that they swear they've seen, and then you have mites, which as I recall are extremely small, causing the same kind of injury?
Dr. OCONNOR: Well, it's not the mites causing the injury to the livestock. It's the mites causing the injury to the coyotes and the dogs that make them look like monsters, and that kind of meet the description or, you know, they look like what these original creatures were described from in Puerto Rico.
Now, in Puerto Rico they don't have any coyotes, but you know, there could be dogs there. But the legend changed a bit when it moved from the island from the mainland.
The original chupacabras was a biped. You know, I thought it could have been a monkey or something. But when it moved to, the legend moved to Mexico and Texas, then it became a quadruped. So it's walking on four legs.
And the other things that go along with that, they're hairless and scaly and have big fangs and, you know, spikes on their back - these kinds of things are often symptomatic of sarcoptic mange in these dogs and coyotes.
PALCA: Yeah, well, I guess it would be scary to see a coyote with those features coming at you. Tell us a little bit more about mange. What is that all about?
Dr. OCONNOR: Well, mange is caused by a variety of different kinds of mites. These are really tiny little critters that are related to spiders. They have eight legs. But these are specialist parasites that live in the skin of their hosts.
There's a lot of different species that belong to this group. They affect mammals. There's another group of mites that can do similar things in birds.
And basically they're parasites. They're living their whole life on the host animal and they're getting all of their nutrition from it, and it's the reaction of the host's immune system to the presence of these parasites that actually is what's causing the symptoms.
PALCA: I see. Is there anything similar that humans get?
Dr. OCONNOR: Well, it turns out, actually, that humans have a disease called scabies, and the mite that causes human scabies is in fact the same one that is causing the mange condition in the dogs and coyotes.
That's work that I did some years ago, showing that the evolutionary history of this group of mites, it's been with primates, which is, you know, us and our ape and monkey relatives, and that the monkeys both in Africa and Asia and then also in South America have closely related species to the mite that's on humans, and we can't really distinguish the mite that's on humans from those that occur on the domestic animals, and subsequently they appear to have moved from domestic animals onto wild populations as well.
And with human scabies, a normal case of scabies is, oh, a mite population of about 20 or 20 mites or so, and it's self-limited. Your immune system will ultimately kill them off, and then you'll be immune for the rest of your life.
When it's in a non-human that they haven't had a long evolutionary time to -what we say - co-adapt to each other, then the populations get really big. There can be thousands or millions of mites and cause an enormous amount of damage.
PALCA: It's an interesting concept, I think, that the human immune system is not only fighting off microbes, but it's fighting off, you know, macroscopic things like mites.
Dr. OCONNOR: Oh, sure. Uh-huh.
PALCA: Okay, so first of all, do we - how come we don't have chupacabras here in New York City?
Dr. OCONNOR: Well, I've not really seen an example of this or evidence of it in the Eastern coyotes here that we, you know, we have here in Michigan. They tend to be more in the ones in the South and the Southwest.
We do have the sarcoptic mange, though, and I was a graduate student at Cornell University in New York, and at the time I was there, there was a major what we call epizootic or a big outbreak of sarcoptic mange in the fox population in New York. And it essentially virtually wiped them all out because in these wild host species, the condition is very typically fatal.
PALCA: Okay, let's take a call now and go to Jim in Pinedale, Wyoming. Jim, welcome to SCIENCE FRIDAY. You're on the air.
JIM (Caller): Thank you very much for taking my call.
JIM: Hey, the photos I've seen of these chupacabras in Texas, the dead ones that have been found, look exactly like photos of the larger size Mexican hairless dogs of Mexico. And not only are they hairless, but they also have the same dental pattern, which is they're missing teeth.
JIM: So these chupacabras of Texas are nothing more than stray or feral native dogs of Mexico, the Mexican hairless.
PALCA: Oh, interesting point.
JIM: And some of those dogs are fairly large, they're 30 or 40 pounds.
PALCA: Okay, well, Jim, that's an interesting theory. What do you think about that?
Dr. OCONNOR: Well, it's certainly a possibility that that could account for some of these things. I mean, I've seen a lot of photographs myself, and the ones that I've seen mostly are showing coyotes with the mange condition.
And the most severe cases that I've seen, typically, there's still some hair left on the back of the animal, which would kind of tie in with that, you know, original legend of, you know, spines on the back and otherwise being hairless and scaly.
And the mange condition does cause the skin to thicken up and, you know, look kind of scaly, and it causes the skin on the face to kind of pull away from the teeth so the teeth become much more prominent and very fang-like in appearance.
PALCA: Okay, just finally, I mean quickly, is there any way, any treatment? I mean, are they going to spray or do something to get rid of these mites?
Dr. OCONNOR: Well, if it occurs in your dog, there are several kinds of treatments that veterinarians do all the time. In wild populations, you know, of coyotes and foxes, no, there's not really anything that people are doing.
I mean, it's conceivable one could put some sort of treatment in baits or whatever, but generally the condition has to kind of move through a population. Anybody who survives is going to typically be immune to it, and then it won't be there for a while, until you build up a suitable susceptible population again.
PALCA: Got. Well, lock up your sheep. The chupacabras are coming. Anyway, thanks very much. That's all the time we have. Barry OConnor is a professor and associate chair of the department of ecology and evolutionary biology, and curator of the Museum of Zoology at the University of Michigan, Ann Arbor. Thank you for joining us.
Dr. OCONNOR: Thank you.
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