Monday, March 18, 2024

Why do vultures "waste time" by circling their dead prey instead of swooping in and eating immediately?

Profile photo for Stefan Pociask

As far as vultures go, their absolute favorite scenario is when they are flying around above the desert, and they see a cowboy or desperado sitting in the sand, with his back against a big boulder. There is usually a trail in the sand, where he was crawling for the last half mile, and an empty canteen that was discarded a mile before that.

This is where the vultures gather together, upon seeing this, and they circle round and round and round, above the desperado below, waiting for him to take his last breath, so they can go in and feast. At some point, the poor guy will look up in the sky, and with one of his last breaths, he will yell out into the sky at the circling vultures, cursing them… “I’m not dead yet, you bastards!!! Damn youuuuu!!! DAMN you ALL to HELL!!!” This is accompanied by either a clenched fist, or a middle finger directed at the circling, somber undertakers above him. Death is near, and they all know it. And the patience of vultures is legendary.

The other scenario is that someone goes out looking for that cowboy. They see a bunch of vultures circling way off in the distance, and they then know it’s too late. He must be dead already, and he’s right underneath those circling vultures. So it will be easy to find his body. Again this scenario is legendary. [1]

In fact, all of this is so legendary, that many people don’t realize that it’s not legendary at all… it’s just a legend! Pure, unadulterated horse puckie.

Vultures don’t, in fact, circle above dead things. And they most certainly do not circle above dying things; patiently waiting for the dying thing to curse at them, and then fall dead, so they can go and eat it.

If you see vultures circling way up high in the sky… [2]

… nine times out of ten… they haven’t found anything yet! They are “just looking”. It means they have found a nice strong thermal of warm air rising from the Earth, and they, like surfers catching a wave, are riding it high, effortlessly gliding on the powerful updraft of warm air. Chances are, if it’s a bunch of vultures, there will be at least one red-headed Turkey Vulture at the lowest level, sniffing while it glides, hoping to catch a whiff of a dead animal. .

The Turkey Vulture (along with its cousin the Yellow-Headed Vulture in the tropics)

… has arguably the best sense of smell in all the world. Fans of bears or albatrosses may argue the point, but in either case, it’s in the top three. This is why Black Vultures soar up above Turkey Vultures. Turkey Vultures, if the wind is right, find the food by smelling it from miles away, then Black Vultures take it over and rip it open, then finally Turkey Vultures come in and finish off what’s left, or they may try to get in a quick bite among the Black Vultures if there’s not too many of them. You’ll notice that a Black Vulture’s nasal openings (nares) are very small and do NOT go all the way through, like the Turkey Vulture’s. Because of this, the air doesn’t flow freely through like it does for the Turkey Vulture. Black Vultures use these only for breathing, not for smelling; while the nares in the Turkey Vulture’s beak allow maximum draft to flow through and across their highly developed olfactory glands, allowing them to smell.

This Turkey Vulture will be covering some area, searching with its powerful sense of smell. Meanwhile, their cousins, the Black Vultures, will be several hundred feet above the Turkey Vulture, quite often just killing time and circling in one place, keeping an eye on the Turkey Vulture below, who is doing most all of the actual searching and the work. The bunch of Black Vultures are kind of in the Waiting Room, if you see a flock circling. They don’t have to cover any ground. They just watch their cousin below them. Once Turkey Vulture sniffs out a corpse and goes down to eat, the much more aggressive Black Vultures go down after it, and chase him away, so they can eat first. Turkey gets the leftovers.

If there is no Turkey Vulture around, the Black Vultures have to hunt by sight, which is much, much harder for them. In those cases, they will circle above wide open places, where a dead animal may be easy to spot. But once they see a potential meal, they don’t waste any time circling. They go down to investigate immediately. Ground based scavengers will usually find these dead animals first. But that’s okay, because Black Vultures also recognize gatherings of ground scavengers, and will occasionally circle above while a pack of coyotes or dogs gorge themselves. Some will take a chance and try to feed alongside the ground scavengers. But this is dangerous. So, many will circle above, waiting, while others land on the ground near-by, waiting for their chance to sprint over on foot as soon as it’s safe. Because of this difference, Black Vultures generally only feed on the larger carcasses, while Turkey Vultures can quite easily locate a dead snake or ground squirrel. Turkey Vultures, when they can’t see the carcass that they are smelling will often fly as low as five or ten feet until the pinpoint the source. Black Vultures would never fly that low. They will just land when they see something, and if it’s hidden from view they will just never see it, and keep circling, hunting, and searching from high above.

Those are the three scenarios of what’s most likely going on when you see circling vultures. They are either waiting for a Turkey Vulture to sniff out food, and just killing time. Or… they are searching by sight. Or… they are waiting for a larger, perhaps dangerous, predator or scavenger on the ground to finish eating. But they will never just circle above perfectly good food, for no reason. Very rarely, something will be even too putrid for a vulture to eat. But even so, they will go and check it out. Also, it’s been noticed that Black Vultures will eat flesh that is considerably more decomposed, than that which a Turkey Vulture will eat in most cases. This could be because Black Vultures have to be less choosy, since they don’t have the additional hunting tool of smell, which is quite an advantage for the Turkey Vultures!

Oh wait… I was reminded of another possibility. Natural gas has an additive in it, ethyl mercaptan, that will be interpreted by a Turkey Vulture, as being from a corpse. When looking for a leak in a gas pipeline, the repair team will often look for circling Turkey Vultures above the pipe.

It may be interesting to note that the issue of vultures using scent as a way to find food has been quite contentious for a couple hundred years. It was believed that birds had no ability to smell, since the 17th century. The first person to publish data to the contrary was Charles Darwin in the early 19th century, when he claimed, based on some rudimentary experiments, that the Turkey Vulture did in fact smell its food. But little notice was taken of this hypothesis. Some time later, in the mid-19th century, another researcher… none other than the famous ornithologist John Audubon himself, claimed to have proven that birds couldn’t smell… and in particular that the Turkey Vulture could not smell.

These two greats in the field of wildlife studies were in direct opposition on this subject, and in the end it was Audubon’s hypothesis that prevailed. Perhaps this was because Darwin was a general naturalist, while Audubon specialized in birds and was generally less controversial. In any case, this remained the popular theory for the next hundred years. It was believed that all vultures found food by simply searching with their eyes while soaring high above. It wasn’t until the 1960’s that a researcher by the name of Ken Stager set out to find the definitive answer, as he suspected that Darwin was in fact correct. He conducted the most controlled experiments to date, in order to gather valid evidence. His work on Turkey Vultures was ground breaking, and finally proved that Turkey Vultures do indeed use their “noses”. And in fact, they depended on it, because it was found that they needed both smell and sight in order to find their food. In this experiment, Stager tried all kinds of variations of visual and odorous clues in order to judge the reactions of Turkey Vultures.

When taxidermized (stuffed) deer were placed in areas where the vultures could see them (these deer were made to exactly look like an actual carcass, but had no meat, of course), the Turkey Vultures paid no mind to them. Whereas, when a Black Vulture was tempted such, they would immediately go investigate, and then finding no food, would exit the area.

On the other hand, when the scent was strong but the meat was hidden from view, the Black Vultures wouldn’t notice the meat at all, but the Turkey Vultures did.

Below is a representation of the Turkey Vulture’s method. It was discovered that wind direction played a crucial role in finding food. When hidden bait was used, the scent was first noticed during their normal circling patterns, but eventually the circles got tighter above the path of the scent, even if it wasn’t directly above the bait. They would then land downwind and search for a visual clue. If they saw nothing, they would exit. [4]

It was also confirmed that the visual-only Black Vulture (Coragyps) did indeed rely heavily on Turkey Vultures (Cathartes) to find its food, as was noted in this excerpt from his report.

Additionally, he confirmed how shy the Turkey Vultures were compared to the Black Vultures, which was in line with the Black Vultures dominating over them.

As you can see, they are spooked by a dying baby chick! They want nothing to do with anything that’s still alive. At this point I must mention that there have been various stories going around that Black Vultures kill newborn calves. I have to tell you… I’m not fully convinced. The evidence is shaky and I don’t trust the people reporting it. There are a lot of vulture haters who would love to villainize all vultures. They do indeed eat the afterbirth. But killing the calf, while the mama cow is right there? Color me skeptical until I get more academic or scientific evidence. Or I see it myself. But back to the story… Actually, it was found that all of five species of North America’s vultures, including the condors, took advantage of their unique, super-smelling but meek (cautious), cousin, the Turkey Vulture, and reacted to them similarly.

One of the reasons for this shyness is the fact that Turkey Vultures have longer narrower wings, which makes them experts in soaring, but also makes it more difficult to rise up from the ground, compared to other vultures. So their abundance of caution is just a safety measure, and it gives them a second or two extra to escape potential threats.

And… one more possibility for circling vultures: If a flock of vultures is so enormous that all the birds can’t possibly get in to get a bite… the remainder may take back to the sky and circle above the rest of the birds, at a much lower altitude, who are feasting. They won’t waste their time on the ground if they know they won’t get any food. This may be the most common reason, if you see a very large group circling. These large groups of circling vultures may be called “kettles”. Nevertheless, they will keep an eye on the feast, just in case there is an opening.

So back to the question… aside from the exceptions I just noted… nah, that’s just Hollywood concocted misinformation. Vultures don’t endlessly circle carrion without landing. [4]

Here is a beautiful guide to telling the two main New World Vultures apart, as they circle overhead. You probably won’t be able to see the red head of the Turkey Vulture way up high… way up high, above your head. But the narrow white stripe along the full length of its wing underside is unmistakable. The Black Vulture, on the other hand, has a big block of white only at the ends of the wing underside. You can remember this by imagining the long white stripes as “crossing the T”… the T stands for “Turkey” Vulture. And if the white is a solid block at the ends, the B in “Block” stands for “Black” Vulture. Next time you see them in the sky, see if you can pick out which is which. In fact, go to the beginning of this article and see if you can tell which kind those flying vultures are. Heck, now you’ll be able to impress that next date you have, when you point out and identify the vultures the two of you see in the sky!


Here’s another tasty treat about vultures, in case you’d like to read a little more. It’s all about the famous poster that features the quote “Patience, my ass… I’m gonna kill something!”

Stefan Pociask
 · 6mo
Why do vultures not take live prey?
Here is the infamous folk drawing that started it all, and spawned posters, t-shirts, patches and hundreds of memes, well before the internet even existed. It was drawn in Bismark, North Dakota in 1973, but no one knows the artist to attribute it to. “Patience my ass… I’m gonna kill something!!” It’s funny and ironic, but the truth is… a vulture would never say that. They are, as we all know, “nature’s garbage men”, or to be more PC… nature’s sanitation engineers. So, why don’t they kill something? Why bother?!! Just like undertakers have the world’s most secure job… vultures have the world’s most secure food source. A healthy vulture will never go hungry. The two things you can never avoid are taxes and death. The government takes advantage of the former… the vultures take advantage of the latter. They fill a truly vital ecological niche on the planet. We need them. They have evolved to be specialists in their occupations. Without vultures, I doubt the world would survive 100 years before most vertebrates were wiped out. They keep disease in check. Let me point out that I’m referring to areas where vultures were present, but then were eliminated or reduced. Ecosystems that never had vultures have their own established way of dealing with things, through other means. Vulture’s digestive tract can easily handle bubonic plague, rabies, distemper, anthrax… most all other evil, little, biological nasties that threaten other forms of life on Earth. It’s all good to them. How can they do this? It’s complex. But basically, their digestive tract has two tools it uses. One is a very low Ph in their digestive juices. It is so corrosive that if a vulture eats meat that contains lead bullets or shot, it will dissolve the lead and give vultures lead poisoning. That is their Achilles’ Heel. A poisoned vulture usually means lead poisoning and is one of the biggest threats to vultures. Of course, lead bullets are a man-made invention, so once again… hurray for mankind, for finding a way to poison the un-poisonable. But besides that, up to 60% of toxic bacteria is simply dissolved. Bye-bye deadly microorganisms. And the other tool that vultures have is that the remaining 40% that isn’t destroyed.. it just hangs out in a vulture’s gut, doing nothing. Vultures are cool with that. No biggie. It’s got to be pretty frustrating for the toxic microorganisms, who are used to getting their way. But vultures are simply not affected. They have some other features that help them with this. You’ve probably heard that the reason their heads are featherless is so that they can freely stick their heads into the nastiest of stink-holes, and not worry about getting their feathers all contaminated. That’s true. They stay cleaner that way. The sun and rain wash away extraneous filth. It comes in handy. Also, they have a way to disinfect their feet, which are always walking on top of putridness. In another irony, to cleanse their feet, they simply defecate on them… quite regularly. The uric acid is so strong, it kills whatever is on their legs and feet (and it also keeps them cool) . All these things make them excellent at staying healthy, despite what they eat. Now the original question asked, included “They are huge and have sharp talons and bills”. That’s not exactly true. Let me explain it this way… When I first started working as a Raptor Rehabber, I was introduced to all types of raptors… eagles, hawks, owls, osprey and vultures. I had to learn how to handle and hold these large vicious birds. They all have large sharp beaks, as we all know. Understandably, I was concerned about getting bitten by any of these birds. It wasn’t long before I learned something quite surprising. All these beaks, even an eagle’s beak, are the least of my concerns: Even this guy really isn’t going to hurt me with his beak. I’ve been bitten by raptors more times than I can count. No big deal, other than the occasional pinch, when they get you just right. No, beaks of most raptors are not a problem. The problem is these: THESE are sharp talons. This is an osprey. And is something that is very dangerous to handle. Osprey and most all raptors use them to hunt live prey. ON the other hand, these are the talons of a vulture: These feet are the 90 lb. weaklings of the raptor world. They are like chicken feet. Not sharp, the talons are not long, not strong. A vulture can’t grab with them. Guess what he uses them for. I’ll tell you…. walking! Imagine that! Yep, just for walking. They are not weapons. So vultures can’t kill live prey with them, or even grab it. But they can walk and balance a heck of a lot better than an osprey, with those long sharp talons. So, when I handle most raptors, the feet must be controlled because they can do serious damage. But with vultures, it’s not a worry at all. Again, on the other hand… whereas beaks of most raptors are not a concern, the beak of a vulture most definitely is! Look at this: And this is just a tiny BABY! (I love this picture. I call it “I am Vulture! Hear me Roar!”) Beaks are long, big, sharp and strong. They use them to tear apart large dead animals like dead wolves, dead lions, dead elephants, etc. I was once carrying a Black Vulture against my chest, trying to control his head. I slipped up, he spun his long neck around, and slashed out at my eye! I had a long deep scar just 1/2″ below my eye for quite a while. So they are nothing to mess with. But a vulture can’t kill live prey with his strong beak because he’d first have to catch it with his chicken feet. And that’s not going to happen. So there you go. Vultures are very specialized. They eat dead animals and they are very good at it. But they generally don’t hunt them. They are very good at finding dead animals. A Turkey Vulture has one of the most amazing senses of smell in the animal world. They can smell a rotting carcass from thousands of feet in the air. And here’s something interesting: the Black Vulture, a close relative, is nearly always hanging out with a Turkey Vulture (red headed vultures). Black Vultures can hardly smell at all. So what they do is, they soar up in the sky a few hundred feet above the Turkey Vulture. And when the Turkey Vulture smells a meal, they follow him down and take it from him. The Black Vultures are the more aggressive of the two. So the Turkey Vulture, after finding food, has to share his meal, and sometimes even wait until the others are done. He doesn’t seem to mind though. Black vultures act as protectors. They have a strange but stable relationship that way. Vultures are very important, but they aren’t killers. We call them ugly, but even a vulture is cute when he’s little and fluffy. Here’s a video of me feeding a brood of little vulture chicks. A little messy… but who among us can say we haven’t had our faces covered in chunks of raw meat?! Yes, that’s me wearing camo, so that they don’t recognize me as a human. They are the most impressionable of all birds when young. Very smart. We don’t want them thinking man is where they get their food. I don’t want them believing I’m the mama! So I cover up, don’t talk to them, and use this adult vulture puppet to feed them until they can be set free. So cute! Kinda look like penguins at this age, don’t they? Yes… they are related. But that’s another story. Now here’s the bad news. Certain populations dropped drastically over the past three decades from as many as 90 million to only 10,000 today, making them critically endangered worldwide. Most species are endangered. Some species are better off. There are a few reasons why this magnificent bird could be close to disappearing. In 2003 scientists identified diclofenac, an anti-inflammatory drug used to treat livestock, as the main cause for this decline. So, when cattle treated with diclofenac die and the vultures feed on them, the medicines work their way into its body system, causing renal failure. Vultures don't have a certain enzyme that can break down diclofenac and therefore it hits their kidney dangerously. Vultures eating the carcasses of animals recently treated with the drug die from severe kidney failure within weeks of ingesting it. Then there’s the rampant lead poisoning killing many more. Plus… many ignorant fools shoot them. Please help people understand they are vital and endangered. This is no joke. They could soon be gone. So… Save a Vulture… Save the World. EDIT: I was asked to add this information that I wrote in response to a comment: Here is an example of what happens when vultures disappear. In the 1990’s, India lost 95% of their vultures. Following the decline of vultures, India experienced a strong uptick in feral dogs… by an estimated 7,000,000. The increase in dogs, feeding on disease-ridden carcasses, is thought to have at least partially caused a rabies outbreak that was estimated to have killed 48,000 people from 1992-2006 in India… deaths that may have been avoided if not for the disappearance of vultures. Vultures can eat any disease that shows up on a carcass. Many of those diseases are deadly to various other vertebrates. But since the vultures get there first, and either consume the disease ridden flesh… or they eat it before a disease takes hold, before some insect infects it… they have just prevented the spreading of any number or diseases. Insects become carriers. Other animals that have more contact with humans and other mammals get infected by those animals become carriers, and it just spreads. The number of diseases that can result from rotting carcasses is immense. And meat doesn’t have to be rotting to putridity to become diseased. Many animals are scavengers and will eat flesh they don’t know is diseased. Rats are one classic example. And many of those animals die. They, in turn, are eaten by more animals, further spreading the disease, and so on. And/or more insects spread the disease. That’s how epidemics happen. ** If you enjoyed this vulture story, I have 25 fun bird rescue videos I took at the Raptor Center, some of which you may find interesting to watch: https://www.youtube.com/user/wun...

And... on an unrelated issue… but very important to me…

I was absolutely certain that by now, I wouldn’t need to re-post this. Unfortunately, despite my best efforts, I am still in a desperate situation. I’m still near eviction, after my long illnesses and operations. Still unable to get a job that will pay the April rent & electric bill, preferably a job in my field. Over 150 of you all have helped me when I needed it most, And I’m eternally grateful. But still, nobody is hiring me for the past 8 months, despite my best efforts of searching for 10–14 hours a day. You’ve been my only income, and have literally kept a roof over my head and the lights on, for many months.

I did manage to freelance as a mechanical designer for several weeks, working on a project, designing a wildlife camera for NOAA. But that ended and my 467 resumes (as of today, March 16) I sent out so far are still being ignored. I’m 61. I don’t know how much my age is the reason. All I can do is keep trying, 7 days a week. Trying not to let depression and constant anxiety get the best of me. It’s getting really difficult. With deepest appreciation, and humility, bordering on shame… (desperation is trumping the shame at this point)… I thank you again!

I’m not usually a “taker”, but at this point, I have no choice.

Would you mind reading this link of mine?

Stefan Pociask, your Quora wildlife educator, organized by Stefan Pociask
My name is Stefan. A current resident of Davidson, NC., but my heart is s… Stefan Pociask needs your support for Stefan Pociask, your Quora wildlife educator

IMAGE CITATIONS:

[1] “End of the Trail” - 1953 Photograph by Adrian Atwater, featuring Wallace Irving Robertson as the dead cowboy.

[2] Screenshot of video clip by Benozaur, Poland / Benozaur ~ Artist Portfolio

[3] [Image: The turkey vulture’s “verification flight pattern,” taken from “The Role of Olfaction in Food Location by the Turkey Vulture” by Kenneth E. Stager 1962].

[4] Photo by Hart Rufe, St. Lucie Audubon member Raptors and Owls 

No comments: