PSA: you might want to finish eating your breakfast or lunch before you read about turkey vultures eating theirs!
Mesmerized, I paused in the warm, South Carolina sunshine to watch a kettle of turkey vultures circle lazily, their wings tracing the invisible movements of air. From a nearby tree line came the lusty singing of a brown thrasher, and the sweet trill of a pine warbler. The week I spent at Loon Camp on Lake Jocassee in early March was a delightful preview of spring.
Most people probably don’t associate turkey vultures with spring—or even realize that vultures may have flown as far as South America for the winter—but they are one of the earliest returning migrants. “What blazes the trail,” wrote Mary Oliver, “is not necessarily pretty.” Vultures need warm weather so that the smell of their food can rise skyward, and because it’s far easier to eat fresh roadkill than frozen dinners.
Of course, food spoils more quickly in warm weather, and eating the putrefying flesh of deer, raccoons, and other beings who’ve met their demise has its dangers. Getting hit by cars is an obvious one. Plus, rooting around in rotting meat would make you or me very sick. Despite their gross diet and appearance, every adaptation of the turkey vulture is aimed at cleanliness, and they have some ingenious ways of staying healthy.
For example, they defecate on their own legs, using the super acidic liquid as a disinfectant and to cool their body as it evaporates. The bare, red skin of their heads not only gives turkey vultures their name, it also allows the sterilizing effects of ultraviolet radiation from sunlight to kill bacteria. That’s very useful after sticking one’s head in a rotting carcass. UV sterilization works on their feathers to some degree as well. Especially after damp weather, you may notice them perched with their wings spread to the sun.
On the inside, turkey vultures’ intense stomach acids can kill the microbes that cause botulism, anthrax, cholera, tuberculosis, salmonella, and rabies. How appropriate that the birds’ scientific name—Cathartes aura—means “purifying breeze.”
Their digestive system is so powerful that it even destroys the DNA of their food. Isn’t that normal, you may wonder? Not at all. In fact, wildlife researchers often test the scat of their target species for the DNA of their prey to determine what they are eating. It even works for humans. Scientists have found it’s more accurate to test the DNA in a stool sample than to rely on people to self-report what they eat each day when doing dietary studies. That wouldn’t work for vultures.
At a roadkill, though, venison isn’t the only thing on the menu. Even if vultures find a dead animal quickly, they may eat on it for a few days. In that time, plenty of other critters join the feast—the meat will be colonized by a host of potentially pathogenic bacteria and invertebrates. Plus, if an animal’s tough hide wasn’t breached by the cause of death, vultures may need to use an existing hole to get inside, putting them in contact with feces, too. Despite the effectiveness of bare skin and sun baths, one study identified roughly 528 different types of microorganisms living on a vulture’s face.
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| See how the turkey vulture's eye looks cloudy? Like many birds and other animals, turkey vultures have a third eyelid called a nictitating membrane. It acts like goggles to protect their eyes while feeding. Photo by Emily Stone. |
What’s even more amazing was that only 76 (14%) of those microbes survived the vulture’s stomach and made it to the large intestine. It takes a very special microbe to make that journey intact!
In particular, researchers from Denmark discovered in 2014 that there are two groups of pathogenic bacteria possibly acquired from carcasses, that thrive in a vulture’s stomach. Clostridia bacteria cause food poisoning, lockjaw and malignant edema in people and cattle. Fusobacterium are flesh-digesting bacteria that would make most critters very sick. It’s thought that the vultures have developed a symbiotic relationship where they allow microbes who were starting to decompose the carcass to continue their work on into the vulture’s stomach, thereby assisting with digestion and releasing nutrients where the vulture can absorb them.
While this idea would once have been far-fetched, scientists continually uncover more examples of symbiotic relationships in nature. It’s not at all uncommon for an animal to rely on microbes to help digest their food—that’s how our stomachs work, too. And it’s also common for parents to pass those partners on to their children. Since vultures feed their chicks through regurgitation, they likely get a dose of those bacteria even before they start feeding on carcasses by themselves.
As of March 27, I still haven’t seen a turkey vulture in the Northwoods, but soon they’ll be showing up on the wind and helping us out with a little spring cleaning!
Emily’s third book, Natural Connections3: A Web Endlessly Woven, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.
For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Our Summer Calendar opens for registration on April 1st at 9:00 a.m.! The Museum is closed until May 12 to allow for construction of our new exhibit, The Wetland Way. Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.
