Dozens of recent scientific studies have looked the microbiomes of the human body, the collection of microbes in and on the full array of human organs, including gut, mouth, skin and lungs. But until recently, no one had thought to study the microbial colonies of carcass-eating vultures.

The dearth of scientific data on the microbiomes of New World vultures is no more, thanks to a group of researchers at the University of Copenhagen. As it turns out, the microbial makeup of a vulture is almost the mirror opposite of that of a human.

Whereas humans house a complex internal ecosystem of thousands of microbes, with only a few hundred or so on their extremities, vultures feature a smorgasbord of microbes on their beak and face (528 kinds of bacteria, to be exact) while hosting only 76 types of microbes in their intestines.

"They're sticking their heads into decaying carcasses, so it's not surprising that their faces have so many kinds of bacteria," study co-author Gary Graves told The Washington Post. "But when you get to the lower intestine, it's dominated by a small number of very common bacteria. There's a huge reduction from what they actually consumed."

Graves is the curator of birds for the Smithsonian National Museum of Natural History; he was one a few scientists who collaborated with the Danish researchers on the new study.

As the microbes descend into the guts of the vulture, researchers explain, only a few dozen are able to survive -- a sort of race-to-the-bottom bacterial competition. The germs that survive and thrive in the bowels of these filthy birds would make many humans deathly ill.

Clostridia and Fusobacteria are two of the big winners of intestinal clash. Clostridia is the microbe responsible for human infections like botulism, gangrene, and tetanus. Fusobacteria can cause gum disease and encourage ulcers, and may also play a role in the development of colon cancer.

"On one hand, vultures have developed an extremely tough digestive system, which simply acts to destroy the majority of the dangerous bacteria they ingest," study author Michael Roggenbuck, a researcher of microbiology at the University of Copenhagen, said in a released statement. "On the other hand, vultures also appear to have developed a tolerance toward some of the deadly bacteria -- species that would kill other animals actively seem to flourish in the vulture lower intestine."

Researchers aren't sure if the microbes are simply tolerated or encouraged. Though these dangerous bacterium types do outcompete their way to a position of dominance in the vulture's gut, they also likely provide some sort of benefit to the animal. More research will be needed to determine what exactly those benefits might be.

Researchers hope further analysis could offer clues as to how vultures tolerate such volatile microbes, and potentially lead to insights as to how to battle them when they cause trouble for humans.

The study was published in the journal Nature Communications.