While many people might think of vultures as gross or morbid, these birds play a very important part in our world. Vultures are called scavengers because they eat carrion, or the decomposing flesh of animals that are already dead. Without scavengers removing them, animal carcasses would lay around collecting bacteria, viruses, and other dangerous pathogens, making our roadways and habitats filthy and smelly. In a way, you can think of our bald friends as nature’s very own clean up crew. Yet, what do we think of when we see vultures? Perhaps how “ugly” they are, or how unappetizing their food is. Actually, these features of the vulture are all specialized tools of its trade.
The two groups of vultures, Old World and New World, are comprised of 23 species found on every continent except Antarctica and Australia. Though not closely related, each group of vultures fills a similar role in their respective ecosystems. They also share similar adaptations exquisitely fit for their task of disposal; but these features evolved independently in both groups, a natural phenomenon known as convergent evolution.
That well-known and uniquely bald head and neck help vultures stay clean while diving into carcasses— feathers in these areas would trap blood and bacteria. Large wings allow these mighty birds to soar along wind thermals high in the air, saving energy by reducing how many times they have to flap while searching for food. The Ruppell’s griffon vulture of Africa holds the record for highest flight at 37,000 feet, beating most commercial aircraft!
Some vulture species use their sense of smell to locate food by picking the scent of the pungent gases carrion gives off. Turkey vultures in the Americas can smell these gases from over two miles away, and will form large groups in the sky called kettles. These kettles help alert other scavengers like eagles, big cats, and even other vultures that see better than they smell.
Vultures are social, especially when feeding, and multiple species may come together to devour a carcass. Their sharp hooked beaks are efficient at breaking apart meals quickly— a large group can clean an entire 220-pound carcass in less than 30 minutes. Smaller species will often wait for their larger cousins’ bigger beaks to break in and start the feast. Once dinner is underway, one of the best tricks vultures have is their highly specialized stomach, possessing strong acids that kill most of the nasty critters that thrive on decomposing flesh. Anthrax, cholera, botulism and rabies are no match for the digestive juices of the vulture!
Since vultures eat such large amounts of carrion, they protect other animal populations from pathogens that would otherwise multiply. The decline in vultures in India since the 1990s may even be linked to increased rabies cases in the region. Without vultures to clean up animal carcasses, feral dog and rat populations have risen with more access to disease-bearing carrion. These animals can carry the rabies virus and live among humans. More people in India have been treated for rabies, amounting to nearly $34 billion in health costs, thought to be due to lower number of vultures.
With the many tools vultures have at their disposal, they are well-suited creatures for their vital and dirty job. Perhaps the next time you see a vulture at the zoo, in the sky, or on the road, you can “carrion” a conversation about their distinguished, ‘disgusting’ traits.
(Pictured at the top of this page: Turkey vulture Cathartes aura)
Cassie Swindle is a senior keeper at the San Diego Zoo.