Vultures evolved an extreme gut to cope with disgusting dietary habits

Vultures have special digestive systems adapated to deal with putrid carcasses that would be toxic to many other animals
Vultures have special digestive systems adapated to deal with putrid carcasses that would be toxic to many other animals

How is it that vultures can live on a diet of carrion that would at least lead to severe food-poisoning, and more likely kill most other animals? This is the key question behind a recent collaboration between a team of international researchers from Denmark's Centre for GeoGenetics and Biological Institute at the University of Copenhagen, Aarhus University, the Technical University of Denmark, Copenhagen Zoo and the Smithsonian Institution in the USA. An "acidic" answer to this question is now published in the scientific journal Nature Communications.

When vultures eat lunch they happily strip the rotting carcasses they find back to the bone. And if, however, the animal's hide is too tough to easily pierce with their beak, they don't hesitate to enter it using other routes, among them the back entrance - so to speak: via the anus. Although their diet of meat that is both rotting and liberally contaminated with feces would likely kill most other animals, they are apparently immune to the cocktail of deadly microbes within their dinner such as Clostridia, Fuso- and Anthrax-bacteria.

"To investigate vultures' ability to survive eating this putrid cocktail, we generated DNA profiles from the community of bacteria living on the face and gut of 50 vultures from the USA. Our findings enable us to reconstruct both the similarities, and differences, between the bacteria found in turkey vultures and black vultures, distributed widely in the Western Hemisphere. Apparently something radical happens to the bacteria ingested during passage through their digestive system," says Lars Hestbjerg Hansen, a professor at Aarhus University who together with PhD-student Michael Roggenbuck lead the study while he was at the University of Copenhagen.

From head to gut

On average, the facial skin of vultures contained DNA from 528 different types of micro-organisms, whereas DNA from only 76 types of micro-organisms were found in the gut. Michael Roggenbuck explains:

"Our results show there has been strong adaptation in vultures when it comes to dealing with the toxic bacteria they digest. On one hand vultures have developed an extremely tough digestive system, which simply acts to destroy the majority of the they ingest. On the other hand, vultures also appear to have developed a tolerance towards some of the - species that would kill other animals actively seem to flourish in the vulture lower intestine."

These observations raise the question as to whether the Clostridia and Fusobacteria in the gut simply out-compete the other bacteria but don't confer any benefit to the vulture, or in contrast, if their presence actually confers dietary advantages for the vultures. The team's results suggest that it's probably a bit of both - while other microorganisms are likely out-competed by the surviving bacteria, the also receive a steady stream of important nutrients when the break down the carrion. Of broader significance, Gary Graves of the Smithsonian Institution's National Museum of Natural History observed:

"The avian microbiome is terra incognita but it is not unreasonable to suppose that the relationship between birds and their microbes has been as important in avian evolution as the development of powered flight and song."


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Journal information: Nature Communications

Citation: Vultures evolved an extreme gut to cope with disgusting dietary habits (2014, November 25) retrieved 16 June 2019 from https://phys.org/news/2014-11-vultures-evolved-extreme-gut-cope.html
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Nov 25, 2014
This article describes the current state of microbe populations on the faces and in the guts of the vultures. Nowhere in the article is any data given about actual microbe populations in extinct bird guts or on their faces. The only statements made relating to the title of the article are suppositions and assumptions not based on actual data. Among the questions not addressed is - how did the birds survive their first forays into eating carrion? Seems they would not have been able to take advantage of millions of years to develop resistance to hundreds of lethal microbes because the first birds that dared to eat the stuff would have died, just as non-vulture birds today would if they tried the same thing now. If the supposition is that these vultures evolved from carrion-eating dinosaurs independently of other birds, then that begs the question of how those dinosaurs managed to avoid death during the millions of years between first trying carrion and adapting to eating it.

Nov 25, 2014
LariAnn: Maybe by gradually adding more carrion to their diets over time. You don't need to make the jump all at once. And certainly food poisoning isn't *always* lethal. It's not a huge stretch to imagine going from principally carnivorous to occasional carrion to mostly carrion to all carrion.

Nov 25, 2014
Everyone ignore LariAnn.
"vultures" evolved independently twice from different birds occupying the same niche.
Old world vultures are actually more related to eagles. And new world vultures are condors. This is apparent in there respective sense of smell, and you can see it just looking at just their face.
That took 5 minutes of research on wikipedia.

"Birds" evolved from dinosaurs in the early Triassic. Birds and dinosaurs lived together, and birds are older than most dinosaur species you've heard of, they've had plenty of time to evolve these differences (Dinosaur+Mammal time).
Time tables are of critical importance in understanding evolution, dates are not arbitrary.

@LariAnn, the evolution of vultures is well understood and makes perfect since.
I don't believe vultures can cross ocean because they glide a lot when they fly.

Nov 25, 2014
Wouldn't even non-lethal (but very unpleasant and/or uncomfortable) food poisoning make the birds tend to avoid carrion in the future, rather than seek it out? I'd like to know what the incentive would be for the birds to choose intentionally to eat something that would make them suffer ill - unlike humans that do that kind of thing all the time!

Nov 25, 2014
I'd like to know what the incentive would be for the birds to choose intentionally to eat something that would make them suffer ill -


Hunger.

Nov 25, 2014
as a "Geier" by name, I am a "vulture"(German trans.) and I say -
"Patience my ass, I'm gonna kill me somethin'..."

Nov 25, 2014
Additionally, thanks to Cruisin Steve for the clarification on (old world) vulture types. In German, vulture(Geier) implies a noble bird of prey...:-)

Nov 25, 2014
Wouldn't even non-lethal (but very unpleasant and/or uncomfortable) food poisoning make the birds tend to avoid carrion in the future, rather than seek it out?
@lariann
yes and no
it depends upon the amount of food available and when the animal last ate as well as the severity of the response from the food poisoning (and i say animal because almost all predators will also consume carrion over the course of their life, from coyote, wolves and bears to eagles, chickens, owls and other birds of prey)
I'd like to know what the incentive would be for the birds to choose intentionally to eat something that would make them suffer ill
like all other animals, it likely comes down to survival (essentially what VIetvet says far more succinctly than i have)
humans included
when you are starving and there is nothing else available...

Nov 26, 2014
Can these birds teach us how to make the antibiotics that keep them safe? Perhaps a hybrid with the domestic fowl? ;-)

Nov 28, 2014
Funniest article I ever read was by a wildlife and bowhunting columnist named Dr. Dave Milne who described his youthful encounter with a turkey vulture nest. The vulture defense mechanism is projectile vomiting, all over you and all over its legs. Yummy!

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