I learned this today. Vultures can eat rotten meat that would make us very sick because their stomach acid is 100 times stronger than ours.
If you or I were to go and find a dead animal by the side of the road and eat it, we would get very sick within a few hours. Once an animal has died, the bacteria that were inside it during its life start to break it down. Other bacteria from the soil also find their way to the decaying animal and begin to digest it. If we ate that rotten animal, those bacteria would go inside us. They would pass straight through our stomachs because a lot of bacteria are acid resistant, and they would settle in the wall of our intestines. There, they would happily multiply, releasing toxins. The body’s immune response kicks in when it detects these toxins and your intestine swells. The toxins also open pores in the intestinal wall, allowing water to flood in. This is what causes diarrhea. This might be an annoyance, and even fatal if you don’t have access to salt and water, but it serves a purpose because it washes the bacteria and toxins out of your body. You will be sick for a while, but your body’s natural response will kick out all of the nasty bacteria.
Vultures don’t get sick for two reasons. Firstly, the acid in their stomachs is about 100 times stronger than ours. Human stomach acid has a pH of 2, and that can kill a lot of bacteria. Vultures have a stomach acid that has a pH slightly above zero. It is strong enough to dissolve metal. It will kill any bacteria, even acid-resistant ones. None of the bacteria that would make us sick can survive in a vulture’s stomach. The acid is so strong that even DNA can’t survive.
The second thing that helps them is the bacteria that do live in their intestines. We have hundreds of types of bacteria in our intestines that help us to digest food, but vultures only have about 72 and these are dominated by fusobacteria and clostridium. Both of these bacteria are highly toxic. Clostridium produces botulism. The vultures seem to have evolved an immunity to these toxins and they might use them to discourage other bacteria from settling in their intestines. These bacteria are also found in other carrion eaters, such as crocodiles.
A lot of people don’t like vultures, but they are an incredibly useful species because they eat and destroy a lot of potentially deadly bacteria. In India, in the 1980s, there was a massive vulture die-off. The number of feral dogs exploded, and cases of anthrax and other diseases caused by bacteria skyrocketed.
So, because of the host of toxic bacteria that live in their gut and their extremely acidic and corrosive stomach acid, vultures are able to eat rotten meat without getting sick. And this is what I learned today.
Sources
https://www.audubon.org/news/how-vultures-can-eat-rotten-meat-without-getting-sick
https://en.wikipedia.org/wiki/Vulture
https://www.sciencefocus.com/the-human-body/what-happens-in-my-body-when-i-get-food-poisoning/
https://www.nature.com/articles/nature.2014.16345
https://www.redding.com/story/life/2017/07/26/vultures-have-ph-public-health/504630001/
[…] When you put food in vinegar, it raises the pH level of the food and kills nearly all of the bacteria. Vinegar has about 10% acetic acid yet it is safe for us to eat. However, it is not safe to pickle raw meat. Raw meat can contain salmonella, listeria, and e-Coli bacteria. All of these bacteria are immune to all but the strongest acid. The stomach of a vulture is strong enough to survive them, but ours isn’t. […]