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Bloodthirsty monster or mangy coyote?

U. MICHIGAN (US) — Tales of the fearsome chupacabras, also known as the goatsuckers, surface around Halloween each year, but scientists say the dreaded monsters actually are coyotes with extreme cases of mange.

Livestock attacks in Puerto Rico, where dead sheep were discovered with puncture wounds, completely drained of blood, led to reports of monsters on the prowl. Similar reports began accumulating from other locations in Latin America and the U.S.

Next came sightings of evil-looking animals, variously described as dog-like, rodent-like, or reptile-like, with long snouts, large fangs, leathery or scaly greenish-gray skin, and a nasty odor.

Scientists studied some of the chupacabras carcasses and concluded the creatures were coyotes with mange—a skin condition caused by mites burrowing under the skin. University of Michigan biologist Barry OConnor, who studies the mites that cause mange, has an idea why the tiny assailants affect wild coyotes so severely, turning them into atrocities.

In a recent “Monster Talk” podcast, OConnor explained 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.

Evolutionary studies done by OConnor and his former graduate student Hans Klompen, now an associate professor at Ohio State University, suggest that the scabies mite has been with us throughout our evolutionary history, giving humans plenty of time to develop defenses.

When humans began domesticating animals, Sarcoptes scabiei found a whole new realm of potential victims. Domestic dogs, like humans, have played host to the mites long enough to evolve the ability to fight off mange, but when the condition spreads to wild members of the dog family—foxes, wolves, and coyotes—watch out.

“Whenever you have a new host-parasite association, it’s pretty nasty,” says OConnor, a professor of ecology and evolutionary biology. “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.”

In these unfortunate animals, large numbers of mites burrowing under the skin cause inflammation, which results in thickening of the skin. Blood supply to hair follicles is cut off, so the fur falls out.

In especially bad cases, the animal’s weakened condition opens the door to bacteria that cause secondary skin infections, sometimes producing a foul odor. Put it all together, and you’ve got an ugly, naked, leathery, smelly monstrosity: the chupacabra.

Do mite infestations also alter the animals’ behavior, turning them into bloodthirsty killers? Not exactly, but there is an explanation for why they may be particularly likely to prey on small livestock such as sheep and goats.

“Because these animals are greatly weakened, they’re going to have a hard time hunting,” OConnor says. “So they may be forced into attacking livestock because it’s easier than running down a rabbit or a deer.”

While the chupacabras have achieved legendary status, other wild animals can suffer just as much from the effects of mange mites, OConnor adds. In Australia, the mite is killing off wombats. “They presumably got the mites from dingoes, which got them from domestic dogs, which got them from us.”

More news from the University of Michigan: http://ns.umich.edu/

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