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OConnor, however, and other scientists conclude that an 8-legged mite that burrows under the skin of coyotes can give these animals the "chupacabra" look.
He explains that the mite responsible for the extreme hair loss seen in "chupacabras syndrome" is Sarcoptes scabiei, which also causes the itchy rash known as scabies in people. Human scabies is an annoyance, but not usually a serious health or appearance problem, partly because our bodies are already virtually hairless and partly because the population of mites on a given person usually is relatively small-only 20 or 30 mites.
Humans have likely evolved natural defenses for this mite over the years. When we began to domesticate dogs, we likely spread the mites to them. When the mites then transfer to wild dogs, such as foxes, wolves and coyotes, the victims appear to be less able to fight them off.
"Whenever you have a new host-parasite association, it's pretty nasty," said OConnor, a professor of ecology and evolutionary biology and a curator in the U-M Museum of Zoology. "It does a lot of damage, and mortality can be relatively high because that host species has not had any evolutionary history with the parasite, so it has not been able to evolve any defenses like we have."