A Griffon Vulture (Gyps fulvus). Credit: Thermos

Have you ever wondered how vultures can manage to consume rotten carcass all day long without dying of food poisoning?

Well, now you have an answer since a new study provides insight into how this is possible. As it explains how vultures use a combination of its own body’s ability to wipe out some bacteria, but they also rely on a symbiotic relationship with some of the most dangerous bacteria that exist on the planet.

A Dangerous Diet

The study does indeed provide some fascinating insights into how evolution has shaped vultures to cope with their extreme diet. Only a few other animals have adapted to a lifestyle of exclusively eating rotten animals.

Since vultures are unable to tear up the skin of dead animals by themselves, they rely on other animals to first tear it open, or for decay to have reached such a worsened state that the skin is more easily accessible, or to enter the carcass via its cloaca. And if the carcass has been heavily decomposed, so that feces has “leaked” or if it is covered with it, neither matters for the vulture who will indeed devour everything. Most other animals who would attempt anything similar would suffer from acute food poisoning and any human would most likely die.

Symbiotic Bacteria

The study researchers analyzed DNA from bacteria that live in the digestive tract of two species of vulture, the raven, and the turkey vulture. The first peculiar discovery was the very few species of bacteria they found living within the vultures. Indeed, they identified only two strains of bacteria that dominated the bird’s bowels. But these two strains both belong to very dangerous bacterial groups called Clostridia and Fusobacteria. These are lethal to other animals, but not the vultures. Rather than killing the Vultures, they seem to help the birds to break down meat and fat.

A group of vultures descends from the sky to eat a dead deer in the Pre-Pyrenees of Lleida (Catalonia). Credit: Mario Modesto Mata

The researchers believe that besides the birds’ own ability to kill off bacteria by extraordinary harsh chemical conditions and strong acids, the birds also greatly benefits from its symbiotic relationship of these dangerous bacterial strains to help the vultures against other bacteria. Proving that there is indeed some logic to the old saying, the enemy of my enemy is my friend.

Evolution seems to have provided vultures with extraordinary and peculiar ecosystems – a result of a highly specialized alliance between birds and bacteria.

The microbiome of New World vultures