Science

Vultures use acid, nasty bacteria to digest rotting flesh

They snack on danger and dine on death, merrily munching on rotting flesh that would certainly sicken or kill any person and most other animals. But how do vultures do it?

Scavengers' guts are full of bacteria that cause botulism, gangrene and tetanus in humans

Elvira may be released near turkey vultures like this one. (Michael Pearce/Whichita Eagle/Associated Press)

They snack on danger and dine on death, merrily munching on rotting flesh that would certainly sicken or kill any person and most other animals. But how do vultures do it?

These feathery scavengers have one of the toughest guts on the planet, that is how. Scientists said on Tuesday that their analysis of two species of North American vultures showed that the birds possess a ferociously acidic digestive system and intestines loaded with two fiendish kinds of bacteria.

The vulture gastrointestinal passage is a hostile environment.- Lars Hestbjerg Hansen, Aarhus University

In the black vulture and the turkey vulture, this gastrointestinal one-two punch effectively knocks out much of the potential disease-causing microbes populating the carrion — animal carcasses — that these birds eat, the researchers said.

"The vulture gastrointestinal passage is a hostile environment," said microbiologist Lars Hestbjerg Hansen of Aarhus University in Denmark, one of the researchers in the study published in the journal Nature Communications.

"These vultures will consume virtually any dead vertebrate - mammal, bird, snake, fish. They prefer recently deceased organisms rather than extremely putrid carcasses. For example, day-old road-killed deer are perfect," said ornithologist Gary Graves of the Smithsonian Institution's National Museum of Natural History in Washington, another of the researchers.

The researchers examined the community of microbes, or microbiome, living in the gut of 50 vultures of the two species.

The most common gut bacteria - Clostridia and Fusobacteria - turned out to be microbes that are widely pathogenic to other animals. For example, Clostridia can cause a world of woes - botulism, gangrene and tetanus - in people.

Strong acid kills bacteria in rotting meat

The researchers also found that the stomach acid of vultures is very strong and kills a good deal of the bacteria gobbled up by the birds with the rotting meat.

"The majority of the food-ingested microbes will not survive these harsh conditions," said University of Copenhagen microbiologist Michael Roggenbuck, another of the researchers.

The turkey vulture, often called a buzzard, is covered with black feathers, has a featherless head with red skin, and boasts a wingspan of nearly 1.75 meters (6 feet). It is common in many parts of North America.

The black vulture is slightly smaller, with a wingspan of nearly 1.45 meters (5 feet), black feathers and a wrinkled featherless head with dark gray skin. It is found throughout the southeastern United States.

The two are members of a group called the New World vultures that also includes the huge California condor and Andean condor.

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