World Without Predators

Dare its deadly terrors clasp? When the stars threw down their spears and water'd heaven with their tears, did he smile his work to see? Did he who made the lamb make thee tiger? Tiger burning bright in the forests of the night? What immortal hand or I dare frame thy fearful symmetry? Welcome to Stuff to Blow your Mind from how Stuffworks dot Com. Hey, welcome to Stuff to Blow your Mind. My name is Robert Lamb and I'm Joe McCormick. And that was The Tiger by William Blake.

That's right, classic poem and one that ties into today's episode, because we're going to be talking about predators like the tiger, and I do think some of the initials, initial concerns that we're gonna be discussing here, the initial questions about the nature of predators um are closely mirrored in this

poem and some of the questions it's asking. So here's a this weekend strange religious beliefs, Robert, have you ever heard about the There is a Young Earth creationist idea among some Young Earth creationist Christians, an idea that the Tyranno source Rex was a her before. Have you ever encountered this before among Young Earth creationists or their literature.

I don't mean personal now. I make it a point to avoid younger creationist thoughts on dinosaurs and prestricked creatures, to the point that I found such a book in a lending library once, and I took great pleasure in moving it directly from the lending library to the garbage where it belongs. Well, I mean, that's in some ways a noble task. This is a book peddling lies to children, but often with great illustrations. Well it makes them even

more effective. But yeah, so so you're saying, like say, what now Tarrannosaurus rex was a her before that just runs countered everything that I've I've ever read. Now, I want to be clear, I don't want to be unfair. Uh. This is not generally a belief held among Christians or anything like this. This is specifically a subset of Young Earth creationists who believe this. But if you just google it, you'll find all kinds of fundamentalist literature arguing that the

t rex and all other dinosaurs were herbivores. They ate exclusively plants, And to be very clear, this is false. All evidence points to the tarrannisa is Rex having a meat based diet. There's some debate actually over whether the t rex was primarily a hunter predator or was primarily a scavenger of dead animals, and we can come back to that in a minute. But morphological analysis of the t rex skull alone will tell you very clearly that

this is a meat eating animal. It's got the teeth of a meat eating animal, it's got the skull and jaw shape of a meat eating animal. It looks like it was built for applying crushing bites to prey animals and then powerfully pulling its head to move the animal's

body or to rip away flesh. Now, as for the question of whether these mighty therapod dinosaurs were primarily hunter, predators or scavengers, we discussed one strong piece of evidence that the therapod relative of the t rex, the Alisaurus, was a predator in our Kimbodian Stegasaurus episode. You remember that it was another weird intersection between religious beliefs and dinosaurs. But anyway, in that episode we talked about the allosaurus who clearly died from an injury in a fight with

a stegosaur. It got a thagon miser spike right to the crotch, and the way the bone has been preserved, it's clear that that's what happened. This is the opinion of the paleontologist Robert backer Um that that it died in a fight with the stegasaur it and so of course that really makes it look like the allosaurus was a predator. It seems like it would be unlikely that a scavenger would get thagomized in the crotch like that,

so it was trying to attack pray. But anyway, the question is why would somebody, for religious reasons believe that meat eating dinosaurs were actually herbivores. Like, I don't remember anything in the Bible about the t rex. Uh. So I've tried to look up the reasoning behind people who believe this, and it seems to be sort of a consequence of other beliefs. So the people who have written on this, they sometimes refer to a passage in the

first chapter of the Book of Genesis. It's Versus thirty, and it says, quote, and God said, see, I have given you every herb that yields seed, which is on the face of the earth, and every tree whose fruit yield seed to you, it shall be for food. Also to every beast of the earth, to every bird of the air, and to everything that creeps on the earth in which there is life. I have given every green

herb for food. And it was so. So that's a verse that generally says, hey, animals, time to eat some vegetables. And then, of course, also there seems to be more broadly a widespread belief that meat eating would represent some kind of compromise to the idea of the original creation of the world as perfect. It would imply that Eden

was not truly a perfect paradise. Well, I guess it is kind of an interesting theological question, right, I mean, could could Eve have really messed things up all that much? If prior to the fall there were predators feeding on other creatures young, or you had parasite induced blindness occurring, or even something as victimless as a buzzard tearing into

a dead antelope. These are I think, because these are nasty images, people tend to assume that like, oh well, if that were to take place, it would definitely foul the balance of creation. Yeah, if there were tigers in the garden, and then we can't possibly envision them as anything, but then to to try and imagine, say a tiger, Try to imagine a tiger in the garden of Eden. If it's doing anything other than what tigers do, then

it just doesn't make sense. We we can't possibly imagine the tigers anything but what it is, because everything they

are is a meat eater. To envision an herbivore tiger is to envision either a possible like downstream evolutionary form, something on the level of say a giant panda, or something so far back in evolution that it scarcely resembles a cat at all, like to put it in a frame of reference, here, the first terrestrial herbivore probably appeared on land about two two million years ago, and it

would not have looked like a tiger. Now, to come back to the tiger by William Blake, one of the ideas that he's asking is just like to to be very literal with the poem, is how can the same god who made the lamb, the sweeten lamb also make this ferocious tiger? Did he smile his work to see?

Did he who made the lamb make the um? The side note um for Blake, here we the humans kind of made the lamb, like we domesticated that that's kind of kind kind of our thing, whereas the tiger is really ultimately of the two animals, the more perfect, you know, vision of creation. If you want to get technical, Yeah, that's a good point. But but I think this is basically this poem and some of these younger creationist ideas are kind of emerging from the same thing, like how

do we square carnivorous biology? How do we square predation in this kind of idealized version of life? Right? Well, the implication of this belief, whether stated or unstated, is that a perfect world would be a world without meat eating, right, no predators, no scavengers. Now, this is not going to be primarily an episode about the ethics of human meat eating. I think there are questions to ask about, you know, humans who know better, like what would be the correct

choice of how to live? But I wanted to talk about this issue because I want to make the case for the practical necessity of carnivori in nature. How in reality, a world without predators and scavengers would not be a perfect world. It would probably be a much worse world, a world that we would not like at all for many reasons, and perhaps even worthy of being called a

herbivorous hell. Predators and scavengers are important. They play an important role in food chains and ecosystems, and they play a role that we have plenty of evidence directly benefits human beings on Earth. We would not like this planet

without predators and scavengers. But if you just observe the way we talk about them, the way they feature in our narratives, and the way we treat them in reality, you wouldn't know this was the case, right, No, No, you just did assume, yeah, that the tiger is this threat. I mean, clearly, it's the villain of the Jungle Book. How else are we supposed to feel about it? Yeah,

And it's all there in our mythology. I mean, there's always like some kind of evil predatory animal or a monster that's some kind of bigger, messed up version of a predatory animal. Uh, and that we vilify and we cast as a thing that must be killed in order for us to survive. Yeah, I mean to go back to our episode on the first monster. What is arguably the first monster depicted in human artifacts, but a lion headed human. Yeah, exactly, it takes on. It's a human

who has the characteristics of a predatory animal. And there are plenty of good reasons that predators and scavengers are often feared and that they do really frustrate people. And it goes way beyond just direct attacks on humans. I mean, one of the biggest problems, if you're going to consider real problems caused by predatory animals in the world, one

of the biggest problems is livestock depredation. You know, as soon as we had animal agriculture, predators could prey on the herds of domesticated animals that we created, and that's a real like loss of wealth from the humans who maintain those herds. But then also we you know, there are other things like attacks on pets and hosting diseases and parasites, and these are real things that our motivation for humans. But we want to stress again today, a

world without predators is not a world you want. So what happens when we intentionally or inadvertently, you know, wage a war of extinction against our betters in the food chain? Are betters? Yeah, and in many cases are betters. Let's explore a few examples with the caveat here that we're going to ignore cases in which humans have dealt with invasive predators, which is which of course can be difficult in and of itself, but he's ultimately an attempt to

kind of balance the scales that we upset. Right by introducing a predator into a range where it's not originally been, we might be upsetting an ecosystem that was stable on its own. So in most cases, predator eradication efforts or general predator culling or control efforts, they stem from this human unbalancing of the natural environment, and it usually goes down about like this. So you have predators and prey and they live in an involved balance. Then humans come along,

they move into the area. What do they do well, they start building stuff and expanding. That leads to habitat loss for the the natural organisms that live in the area, including the predators. And then predators are killed or driven off when they encroach upon human territory. And then humans are raised domesticated food species, and then predators are drawn to those food species, the lambs that that we have framed exactly. And then uh, and then the predators are

killed or driven off as a result of it. Yeah, it creates a tough situation. I mean, we can look to two examples of it in today's world. For instance, in modern Botswana. Uh, there's this need to protect both valuable cattle and threatened lions species. Local cattle farmers frequently resort to violent retaliation against the predators. Uh. And then again, the lions themselves are endangered. They are only about thirty thousand lions left in the wild, right, so conservationists don't

want to see the lions killed. But then again, if you're a farmer and lions are attacking your cattle, you can very well understand why the farmer feels that way, right. Uh. Now, incidentally, there's a there's a really interesting up potential solution. I don't know if you called a solution as much as maybe a band aid for the scenario that has been explored, but a conservation biologist, Dr Neil Jordan's has actually rolled out a program to paint eyes on the rear ends

of cattle to help to rely on attacks. Uh not unlike anti tiger masks that you sometimes see in belief parts of India or also just sort of the naturally evolved use of eye spots on various insects. And there's evidence this is actually effective. Yes, there is some evidence. Uh Um. I reported on it, I want to say, like a year a year and a half ago, so I haven't checked in to see what the latest data is.

But at the time, the data was encouraging that it was at least in the I mean at least for the short term, cutting down on some of these predation instances. That's really interesting. I mean that goes along with some of the advice that I know this is this is probably not blanket advice, so don't use this as your

survival tactics. But I know, at least in some discussions about how to deal best with encounters of wild editors, like if you encounter I think maybe a bear or a mountain lion or something like that out in the wild. I've definitely heard advice before that you should not turn your back and run because that can very easily trigger you know, chase impulses. So what you want to do is remain facing the animal, make it clear that you can see it, and try to put distance between you

and it, you know, backing away. Uh And and that sort of makes sense. I mean, an animal should be able to see where other animals are looking, and if it thinks you're not looking at it, that is a chance for an attack. Now, another good example or wolves. Wolves have face and continue to face a similar plight

in North America. So humans trot out all of these domesticated prey species organisms that are really in many ways trapped in a perpetual adolescence, which is key because in the natural world that is where you see a lot of the predation. You see the predators preying upon the young or you know, the sick. But through domestication, we've made sure that these species are main ideal prey for us.

So it's uh, you know, it's not a huge mysteries as to why their ideal prey for various obligate carnivores out there. Yeah, so the American gray wolf is this is I found this super interesting. It is the modern

American wolf. Now what does that mean? So, as Carl Zimmer pointed out in a two thousand sixteen New York Times article on the subject, genomic evidence reveals that the Eastern wolf and the red wolf, previously you know, considered to be two separate varieties of wolf, those are actually just mixtures of wolf and coyote d nat so they're just their hybrids. But the one true wolf is the

gray wolf. Well, I mean, it's been interesting to see as urbanization has happened throughout the United States, especially in the twentieth century, the way that wild carnivorous canids have adapted to human spaces. I mean, we we talked in our Urban Evolution episode about the coyotes of American cities. They're all over the place, and they they find ways of surviving alongside us that we barely even detect. So, as of two thousand seventeen, this is the most recent

data as of this recording. Uh, they're roughly five thousand, six hundred and eighty gray wolves remaining in the lower forty eight states. That don't sound like that many. Now Alaska has between UM seventy seven hundred and eleven thousand,

two hundred, but kind of lupus. The gray wolf once ranged from the Rockies to New England, and it's been victim been victim to antipredation efforts to protect livestock, um hunting, trapping, baiting, and some pretty pervasive scare tactics about the nature of the wolves themselves. Now, to be clear, wolf attacks have occurred in North America, but they are rare, and even when they do occur, Uh, there, you know they're not

There's not just one type of wolf attack. You can, for instance, chalk some of them up to defensive attacks, and then also rabies could be a factor as well in some of these cases. Yeah, absolutely, But I mean the wolf is a perfect test case for people, uh to they can see what the danger of being near a wolf is. Like if you're told there's a wolf in your neighborhood, you can immediately envision like, oh, I can see how that could go bad. I could be out in the yard and a wolf could attack me.

But you don't understand or easily visualize the other side of the equation what the downsides can be if there's not a wolf in your neighborhood. And indeed, there are many neighborhoods where they're they're not being no wolves, and sometimes those neighborhoods are something like Yellowstone National Park. Uh. It's an interesting case, and this was outlined by a

science writer and rewilding advocate, George monbiat Uh. He points out that wolves were reintroduced into Yellowstone National Park in a Yellowstone that by that point was overrun by deer without predators to control their numbers, and the results were pretty amazing, he lays out, So they introduced the wolves back into into the park. The wolves, of course killed some deer, as would be expected, but then this also

changed the behavior of the deer. The deer started avoiding essentially dangerous areas of the park, areas that were not a good place to to hang out in if there were wolves about, and these places began to grow again to regenerate. Tree hid here increased dramatically in some areas, he says, Uh, certain bird species moved back in uh,

beavers and beaver numbers increased. And between the wolves changing the essentially the prey species landscape here and the beavers altering the ecosystem as well, UH, they both work to make room for other species to thrive. Wolves killed coyotes and and this allowed rabbit and mice populations to begin to rise, bringing in hawks, weasels, foxes, badgers carrying birds to discavenge. After all of this, bear populations also arose, in part because they were now more berries from the

shrubs that actually were able to grow. And this is often expressed in terms of a top predator in an ecosystem being a keystone species is a species that's sort of like necessary to allow the rest of the ecosystem to thrive as it normally would exactly. And so in this example of what happens when you put a predator back in to an environment, we're essentially seeing environmental collapse in reverse. UH. What what we're talking about here is

widespread trophic cascades. These are ecological changes that start at the top of a food chain, UH, and the spiral all the way down. So yeah, apex predators are not just monsters that live atop you know, a mountain of bones and feast on the you know, the riches of the things that it preys upon, and like some sort of storybook monster. Now that the mountain wilds have have evolved with it, and then for everything depends on the predators for balance. Yeah, there is a sort of mythological

model of the predator as oppressor. It's almost like the predator is the tyrant king of the animal kingdom because it preys on other animals. But really the the oppressor, the tyrant ruler of the animal kingdom is the finitude of energy, is the scarcity of resources, and the predator is subject to that too. And you remove the predator, it's not the case that all other organisms necessarily do

well if the predator is gone. Instead of what you find is that the tyrnt of energy scarcity and food resource scarcity and all of that expresses itself in new ways, begins to to oppress organisms in ways that didn't happen when the predator was there. Yeah. I mean, as we've touched on before, it's not like if you're they've ex predator, it's just fat city. Um. You know, the life of a predator also is filled with challenges and has a

fragility to it. Yeah. I mean when you when you see an image of a predator chasing prey, you should think the praise life is on the line, but the predator's life is also very likely on the line. The predator needs that energy to to survive, and if they don't make a catch soon, they might not survive the next winter exactly. And that's not even taking into account humans hunting you towards extinction or making you know, exploited movies about you attacking you know, um um nude bathers

or something. Yeah, I mean, I think about the vilification of sharks. Uh. I often think of the vilification of sharks as a thing in the past, you know. I think, like, okay, jaws came out, and then there was a brief period in which people saw sharks as these horrible human eaters that had to be destroyed. But I guess my general impression is things have gotten better in more recent years.

A conservation mindset is caught on. People know better than to suggest we should just run around killing sharks and other marine predators. But that's not always the case, even recently, even beyond just pure poaching there have been public campaigns against shark populations and intentional efforts to kill sharks in certain areas. Robert, have you ever read about shark drum lines before this? No, but they sound pretty groovy. Yeah, they're not so groovy. This is the thing I didn't

know about before I was reading about this. But it's uh so it's a lead ethal trap to capture and kill sharks. Just one example is I was looking at a paper from about how in the government of Western Australia decided that sharks represented a threat to human safety to swimming around beaches, so they elected to put out these drum lines to kill the sharks in those areas

and protect human bathers. And basically the way it works is that you have an anchored buoy, and then the anchored buoy is connected to what's known as a drum line buoy, a floating buoy that itself has a a triggering magnet um and then it's got a hook that's baited and so the sharks go and bite the hook and then they get stuck, and then it sends off a signal to let people know, Okay, we've caught one.

Uh And so yeah, there were just these traps set up, and there was a great controversy about it in Australia because there was obviously, you know, people were saying, like we we don't need to be killing sharks. Maybe it would be better to change the place as we swim than to just kill all these animals. Yeah, that does not sound good. I I was thinking of shark drum circles.

That would be a different scenario. Well wait, now, if it's a drum line in that, in that like marching band, like marching drums, Yeah, well that would be good too, but not very groovy. That's more. You know, it's a little it's a little more straight laced. Yeah, you gotta be worried when sharks start doing military formations. But whether I mean, whether due to deliberate human persecution or not. Lots of predators and scavengers we know, have seen drastic

declining populations in the past few hundred years. According to a study we're about to talk about by O'Brien and and co authors, leopards have vanished from about seventy eight percent of their historic range. African lions are on the decline outside of protected areas of twenty two vulture species on Earth seventeen or in decline due to human activities. So predators and scavengers are having a tougher time than

they've ever had, which is dangerous. And one of the key points really this episode is that, yeah, you can't. It's not just the monster disappearing from but it kind of is you take the monster out of a story, and then how much of a story do you really have? If you take Grendel out of Bowolf? What do you have? You're left with just kind of a boring story about

a rampaging psychopath. But if you and likewise, if you take the the apex predators out of the scenario here, then it then it results in this kind of environmental collapse that we've discussed. Well, here's what I'd like to say. I'd like to see an alternate version of Beowulf like

John Gardner's Grendel. Except what happens is after Beowulf kills Grendel, uh, the deer that Grendel normally eat overpopulate the forest and they spread a lot of disease, and everybody in her off cars meat Hall dies because they all get tick born diseases. Right it, man, that's the realistic outcome. Well, maybe we'll explore examples like that when we come back

from a break. Thank alright, we're back, all right. So I was looking at a paper in Nature, Ecology and Evolution published this year called the Contribution of Predators and Scavengers to Human well Being by Christopher J. O'Brien, Alexander Braskowski, Hawthorne Bear, Neil Carter, James Watson, and Eve McDonald madden. And so the basic idea of this paper is that

it's a huge literature review. It looks at papers from you know, all over the place to try to find documented examples of ways that predators and scavengers make human life better or removing them demonstrably makes human life worse. And so they start off talking about how predators and scavengers provide lots of benefits to humankind and we rarely recognize this, like humans and wild predators have undergone a process of coadaptation in the past few thousand years, with

some beneficial outcomes for both. But this state of co adaptation depends on human tolerance of these animals, and as we've seen, this tolerance is not given a lot of times. We'll put out the drum lines will do wolf culling uh, and without predators and scavengers our world would be much much worse. Ecological research has shown this in many ways.

So for example, predators regulate the populations of herbivores below them on the food chain, which if allowed to grow unchecked, could easily overgraze and destroy plant species important to human life. Another thing is that scavengers consume and dispose of animal

carcasses and organic ways that we do not want piling up. Uh. The loss of predators and scavengers can destroy ecosystems by causing quote a loss of plant species, diversity, biomass, and productivity that in turn effect disease dynamics, carbon sequestration, and wildfire risk and Robert this seems to be along the lines of what you were talking about with the wolves

and Yellowstone. And then also sometimes you can estimate the health of an entire ecosystem simply by looking at how the top predators and scavengers are doing like they will be They will sometimes almost be like a data sheet you can check out to see what everything else on

the food chain is looking like. And yet, as we mentioned earlier, lots of predator and scavenger species around the world are still in decline due to human behavior, including everything from poaching to culling, to ecosystem destruction and to climate change. And there are actually documented cases where people intentionally tolerate predators and scavengers, especially scavengers, because they're aware of their benefits. Like the authors talk about how uh scavenger,

the scavenger of the Egyptian vulture. This is a bird species that's suffering and decline around the world, but there are places in Socotra, Yemen where they're doing well because the people are aware of the benefits they provide, specifically removing livestock and human waste, which if not removed, can cause water contamination. And that's no joke. The risks of water contamination due to waste runoff are serious, and this type of contamination is not just something that say, happens

in Yemen. It can happen all over the world and often does. I found a New York Times article from two thousand nine by Charles do Hig about how the residents around Morrison, Wisconsin were sickened contamination of water resources from agricultural waste basically manure breeds, parasites and bacteria which

flow into the groundwater. And to read a quote from that article quote in Morrison, more than a hundred wells were polluted by agricultural runoff within a few months, according the local officials, as parasites and bacteria seeped into drinking water, residents suffered from chronic diarrhea, stomach illnesses, and severe ear infections. And then they quote a woman living in the area who said, sometimes it smells like a barn coming out of the faucet. Now, that's that's not always as much

of a bad sign. Robert, have you ever smelled like kind of FARTI smelling water from a faucet somewhere? Um, I mean, I guess sometimes you know, you're at the beach and the you know, beech water can have a certain odor. I'm not sure if I would say it's, you know, like a barn smell or anything, but I'm trying to remember the last place I was where the tap water was like that. But I've definitely smelled it before. It is a little disconcerting, even if you know it's

probably safe. Like you go to brush your teeth and and it smells like toots for real. Zase has haunted your bathroom. I can't believe he's summoned toots for realities. But now, of course the reverse is also true. There are places where the water certainly seems appetizing, but it's not actually drinkable exactly. So anything you can do to manage runoff of dangerous waste running into water sources is big, and so a lot of times predators and scavengers, particularly

scavengers can do that. Another example is the Tigray region of Ethiopia, which has spotted hyenas, and the humans of this region tend to tolerate them because the hyenas eat the carcasses of dead livestock as well as unburied human corpses, which reduces the risk of disease and the settlements, And so disease and human settlements is a big part of

the benefits provided by predators and scavengers. Some of the biggest diseases were worried about in the world are zoonotic diseases, diseases that have animal vectors like the zekeovirus UH, strains of flu you know, avian flu, swine flu UH, the Ebola virus, lime disease, and so there are several ways predators can reduce chances that we catch diseases from animals, and one of them is by reducing the density of host populations. And so the way that works is this, um, say,

it's flu season. You want to avoid catching the flu? Uh what? What what's a good day look like if you want to avoid catching the flu? Is it like going out to the cannibal corpse concert and washing in the pit? Or is it going for a walk in the woods by yourself? Uh? Well, if you don't want to catch the flu, yeah, go in the woods by yourself. Yeah, exactly.

I mean density, literal population density, how much organisms of the conspecifics spend, how much time they spend around each other, how close they get, how much they contact the same surfaces, and all that that's directly related to the spread of the disease. And so if you reduce the density of

a population, you reduce the rate at which the disease spreads. So, so, to go back to our our Yellowstone example, like, if you have the deer just um, just unopposed by predators, they're just hanging out all over with each other, and that that creates a more potential for something like this to take off. But if they're if they're patrolled by predators, then they're going to be perhaps more fragmented and fewer in number because of the members of their uh their

species that are picked off by the predators. Exactly, thinning out the population of deer could potentially limit the spread of dearborn diseases. And then, of course there's also the more direct effect that if you limit the population of an animals ay dear, it will be less likely that any given human in the area is exposed to a deer, and thus less likely the disease spreads from the deer to the person. Just a few examples cited by the authors.

One is that around Sanjay Gandhi National Park in India, leopard predation on dogs has greatly reduced the frequency of dog bites in the region and thus lowered the incidents

of rabies transmission to humans. Researchers think that generalist predators like foxes can help protect people from lime disease by controlling populations of mice, since mice or a primary reservoir for ticks carrying the disease, and then we don't think to be thankful to frog tadpoles, but tadpoles probably play a really important role in limiting the worldwide risk of mosquito born diseases like dingay fever because they eat mosquito eggs.

Of course, I mean we've we've kind of looked at this and from the opposite direction that like, you know, why do we have mosquito as well, because actually mosquito larva are an important part of many, uh many diets out there, And yeah, it makes sense too that you'd want the animals that eat those larva otherwise explosion of

mosquitoes exactly. But also predators and scavengers can reduce our disease risk through a mechanism known as competitive exclusion, and this is basically out competing disease hosts for resources or territory. So an example here would be vultures sometimes outcompete stray dogs for the main scavenging niche in and around human settlements, and this can be a good thing for reducing stray

dog bites on human and human exposure to rabies. And then sometimes removing natural predators and scavengers from a native ecosystem can lead to their automatic replacement by other predators and scavengers, which might be much worse for human health. For example, the author's right that scavengers can replace vultures, and the ones that replace them can include gulls, rats, and invasive foxes, all of which can pose risks to humans and can themselves be disease hosts because of its nature.

If there's a meal to be had, something is going to get in and eat it, And if you wipe out the predator that's most highly evolved to deal with it, then somebody else is going to take a shot at it. Wouldn't you rather the the predator that's there to eat the meal be the one that the ecosystem is already adapted around, unless there's stability to the ecosystem. So there are tons of ways that predators and scavengers limit human exposure to diseases. But another thing that's interesting is the

way that predators apparently increase agricultural output. I mean, a huge amount of agricultural wealth every year is lost to pest species that consume crops. The author is a side to study estimating that ten of global financial losses and agricultural wealth are due to animal species that come and eat the crops, and that that's a huge amount of lost wealth over the whole globe, and so current methods of preventing that kind of loss are not always great, right.

They often consist of chemical pesticides, which frankly are something that that we're still studying and we don't know all of the negative effects of, you know, many years down the road. Yeah, but but I mean ultimately that the uh, the argument here is pretty simple, like, if something is eating your crops, what better way to prevent that from

happening than having a naturally occurring predator to drive them off. Exactly, I'm trying to keep birds from eating all the figs in my fig tree, and all I have is like a fake owl to set up there next to which, Oh you have a scare owl? I do? Yeah? Or wait to scarecrow. You have a scarecrow owl? Yes, it's it's not a replican owl like the Fabulous Woman having Blade Runner. That one was too expensive, minds the ten dollar model. Its head doesn't even bob. But quick poll,

do you have a favorite killer scarecrow movie? Oh? I mean they're all kind of terrible, aren't they. That's a subgenre that never really caught on, Like you might think, well, there's a lot of potential. They're they're they're they're so creepy. I mean, I guess I love the scarecrow batman villain if he counts. Oh yeah, he's a good one. Yeah he was. Well, I liked him in the animated series. Yes, he was a lot of fun in that too. Yeah. I guess there's some some scarecrow movies coming to mind,

but I feel like it was a little icky. Oh yeah, yeah, yeah, that's the main one that sticks. They often tend to be. I what I'd much rather have is an actual owl, though, that would just live in my backyard and uh and scare away, you know, an appropriate number of predators. They can have some of the figs. I'm not greedy. I just want to make sure that I have some too well.

I mean, predators like that are important not just for your own personal figs, but for for the crops that sustain economies and that that feed people and that are turned into animal feed and all that kind of stuff that,

you know, the backbone of an agricultural economy. Like it has often been speculated by by researchers that species like bats and some birds are the most economically important non domesticated animals on Earth, and this is because of all of the pest control that they naturally do in the wild on pests that would otherwise eat all of our crops.

And so the author's site research that indicates like the densities of pests like the corn earworm or the cucumber beetle can be suppressed by almost sixty percent by back communities, and bats can also help suppress the spread of fungus in corn crops, and so this leads to like real dollars saved and and predatory birds do similar things. They've been shown to be valuable in cocao plantations, saving more

than thirty percent of crop output. Speaking of owls, the barn owl is a huge lifesaver when it comes to saving agricultural output um. Apparently, according to the authors quote, the barn owl Tito alba has a diet made up of about agricultural pest species in agricultural fields of California. Wow, barn owls are a great species to bring up in this because the barn owl, of course is normally going to set up shop and nest in um and it's essentially like a hollowed out tree or tree trunk kind

of in a situation. But now they're co adapted. But that's right, they they they also are fine with sant abandoned barn because this also perfectly replicates the environment they need. But it's kind of a domino effect though, right as as humans expand, suddenly that there are fewer places for them to naturally build their nest. And if you don't have you know, empty barn sitting around, then they also

don't have a place to build their nests. But this has led to many people to put up nesting box is for barn owls, which is essentially just a uh what it sounds like a box, like a mini portion of a barn that you can just put in the top of a tree to encourage them to roost their nice I've never heard of that. Yeah, there's a children's book about it that's reading it about it about it

the other day with my son. Now, I will say I think probably barn owls are not vilified as much as some animals like wolves or Yeah, I think they're mainly suffering from you know, incidental habitat loss, which can be sufficient enough to eradicate a species. But yeah, they're not having a deal on top of that, with people,

you know, essentially raising their pitchforks against the owls. But I mean when it comes to other noticeable larger predators like dingoes, even they apparently increase agricultural output, they help

our farmers too, Like lots of animal. Ranchers obviously don't like carnivores like dingoes because sometimes they prey on their herds, but sometimes wild carnivores actually protect herds in pastures where there are also wild herbivores cause the dingoes or the other animals like that reduced the number of wild herbivores

and thus reduce competition for grazing. So, for example, research in Australia is shown that the presence of dingoes can increase agricultural production by reducing populations of red kangaroo, which compete with livestock for grazing land. And a lot of times cattle farmers don't realize this and they'll kill dingoes, but it has been estimated the dingoes significantly increase output biomass per hectare of land. If you give rid of all the dingoes, then you're gonna have to deal with

all these kangaroos. And what are you gonna do? Just keep killing and killing. Well, yeah, probably that's kind of what humans do. I guess it could be. Hey, when it comes to your garden. They signed a study by the way that says research has shown that skunks reduced pests in North American gardens and increase the yields of

those gardens. So you need to get yourself some skunks. Well, I've certainly heard the argument for possums based in a large part on the number of I believe it's ticks that that that the average possible will eat, so they meant be much to look look at. But if you have a possum in your yard, it's potentially cutting down on on some of the pests you would have to deal with. Oh man, anything that will get rid of ticks. The enemy of my enemy is my friend, even if

it's a possum. Uh. But what about the enemy of my enemy of my enemy, which is your dog or cat? Well, you know, collateral damage, I guess. But now this is a good point. This is why one of the reasons why my cat lives indoors. Now, yeah, I love dogs and cats, but I mean it is certainly true that that domesticated dogs and cats can really mess up an ecosystem if released upon the wild. Yeah, I think about

this a lot. In our neck of the woods, we have a lot of feral cats, pretty common occurrence, I think, uh in North America. And yet yeah, they're they are they are super, They're little super predators are there in their own way, like they are able to just ravage, especially the bird population. When we had Jason or the local Atlanta Bird Exploding podcast, he talked to us a lot about the damage done by just releasing cats and letting them go outside. They're driving off our possums and

they're not eating any of the ticks. It's a disgusting part. That's a good point. Why don't the cats just eat the ticks directly? That would be great, But of course they'll never comply anyway, So uh, we don't stop there. Okay. So predators and scavengers clearly reduced disease risk and disease spread among animals and among humans. They benefit agriculture, They apparently actually benefit human life in urban areas in plenty

of ways. Like so, so there are plenty of things that cause humans and wild animals to come into contact. Of course, expanding human settlements and habitat destruction would be a big part of that. Yeah, do is to go hand in hand. But then, of course animals are often attracted to high calorie foods and shelter, and those are

available in abundance and human settlements. But there are tons of ways that predators and scavengers in urban areas, even within human settlements, are beneficial, including removing waste and carcasses that this happens all the time, like golden jackals in Serbia apparently removed just tons of animal waste, including road killed animals and stuff like that. And then also you've got the fact that in many urban areas, natural predators

control populations of other animals that directly cause harm to humans. Uh, here's a big one. You might not consider natural predators reduce wildlife vehicle collisions. Oh, this makes sense as well, because what are all these excess prey animals doing but running in front of my car? They often are, so the author's right quote. One study found that the potential recolonization of cougars over a thirty year period in the Eastern USA would reduce dear populations and thereby curtail dear

vehicle collisions by twenty two percent. The authors estimated that this reduction and collisions would result in a hundred and fifty five fewer human deaths, twenty one thousand four fewer human injuries, and two thirteen billion dollars in saved costs. If those estimates are right, that's a heck of a lot of damage just caused by deer getting in front

of your car. Yeah, and I have been in I have been in the vehicle, if I remember correctly, on two different incidents when I've the vehicle has hit a deer, there's some way, shape or form. In one case, the deer had already been hit and it was just like coming over a hill and there it was, and like

the car went right over it. But uh, yeah, I feel like this is a this is an increasingly common occurrence if you're doing any amount of driving outside of an urban environment, and even even with within an urban environment, you're still facing the risk of those squirrels or you know, various stray animals that may be running out in front of your vehicle. Well, depending on what kind of urban environment it is there, there are still sometimes even deer.

I mean, I think about how often you see deer in some cities in Tennessee. Certainly, one funny note that I that was in this paper was that apparently reintroducing predator ters can even reduce auto insurance premiums and affected areas because they, you know, reduce the risk. I wonder if I can contact my my insurance companies say, look, I introduced we introduced a mountain lion into my neighborhood. Up, can you bring my my premium down a bit? Plan

on releasing wolves? How will that affect my rate? No? I bet they won't do it on an individual basis, unfortunately. But yeah, so we've got this issue where we know that predators and scavengers provide immense benefits to humans. Of course, they provide benefits to the ecosystems themselves, but they provide immense benefits to human economies, to human public health, all of that. And yet we are going to continue to

have these conflicts because predators are sometimes ferocious. They will sometimes attack our domesticated animals and all that, they will sometimes attack humans as long as they're going to be humans and predators and scavengers in these shared zones, these sort of uh middle zones where both humans and predators can inhabit there will be these conflicts, and yet we

don't want to eliminate them. So part of the question is how do you get people to understand that, even though occasionally there will be wolf attacks on people and stuff like that, that is massively counterbalanced by the benefits provided by these creatures. Yeah, you have to have to weigh all the benefits and not just you know, overreact to one media report about uh, you know, a predation scenario involving a human infant is as shocking and horrible

as that can be. Um, you know, obviously, I mean, it's still not a reason to say set out to destroy all crocodiles or all wolves, right, And and part of the problem is that media reports can just even without intending to do it, sensationalized predators. Like the one thing I often think about is the type of media story that doesn't say we should kill all predators, but it just makes a media story out of predators citing in a human area, you know, because other a wolf

in the neighborhood. Yeah, because otherwise, when is the shark making the news. It's making the news because it was seen in a human swimming area, a human caught it, or killed it, or the reverse happened. Of course it attacked or killed a human there. Yeah, there is no story about the thousands of sharks that swam by without anybody noticing them. And you make a good point that very often the point of conflict here arises because of human aggression, not because of the aggression of the animal,

or even if it's not aggression. It's like if you've if we've all heard, you know, do not feed the wild animals, which is wonderful advice for a number of reasons, but if it's a if it's a prey species, especially if it's a species that that could potentially attack a human, then you should not do anything to to shrink the

natural distance between our species, right. So, I mean, I think one thing in this space that's important is trying to find smart strategies, Smart strategies that don't involve just killing predators and scavengers outright because we don't like them, or because there was one unfortunate point of conflict between humans and whatever the species is that's local, but finding ways to try to reduce encounters between humans and humans in their livestock in these species while allowing the species

to live the example you mentioned earlier with just like being able to paint eyes on the back of cattle, that that sounds like a brilliant example of a solution there. Yeah, make the make the the the the humans cattle less appealing slightly as the feeling maybe even. But then the reverse is well, the lions that are gonna hopefully go eat other things, other prey animals that are still allowed to reside in the natural environment. Yeah, of course not

destroying natural habitats helps as well. Yeah, the to whatever to the more we unbalance the given environment, like, the more complicated it is to try and figure out what the new balance is, or certainly to try and achieve anything like the old balance. But anyway, if so, summary of all that, you've got the disease control, you've got, agricultural protection, you've got all these direct benefits on human life,

like reducing auto collisions or disposing of waste. There are just tons of ways that predators and scavengers are benefiting your life and benefiting human civilization in ways that you don't even appreciate or understand that are completely invisible to you. But without them the world would be so much worse. And so I think we should just take a moment to appreciate the nasty animals. Indeed, here's to you, nasty animals.

Let's take a break, and when we come back, you know, we'll talk a little bit about the nastiest animal of all. Thank you. Thank Alright, we're back. So we've been talking about how, even despite our mythologies and despite some religious beliefs and all, that a world without predation is probably not a good world. That's not a place where you'd want to live. Predation does so many important things. It

plays an important ecological role. But I want to think about another way that a world without predation is probably not a world you want to live in because I have a hard time imagining how a planet that never evolved predation would ever evolve intelligence. Indeed, I mean it's difficult to imagine a human level or greater intelligence emerging

in the absence of predation. Our best examples of non human intelligence are either predators that have to engage in advanced tactics and behaviors to catch prey uh and or utilize these skills to avoid predation themselves. And curiously enough, humans seem to stand as as an example of both. Yeah, exactly. I mean, almost everything we call intelligence, I think has something to do with time. Right. It has to do with the speed at which you your body does something.

An organism that was able to avoid a you know, an oncoming object, but it took a thousand years to do so would you call that intelligence? Maybe? I mean, it seems like it'd be hard to do, but it seems to me like very much. An important part of what intelligence is is that it has to do with the speed of solutions to two problems, right, and the speed at yeah, the speed at which it needs to

find a solution to that problem. Because something reacting at the level we're talking about, uh, you know, maybe not quite the same level, but you can look at an oak tree and say, well, the oak tree has its reflexes are not nearly as as quick as those of say, you know, a feral cat, but they are both effectively solving the problems that are necessary to to existing. Yeah, and speed just pretty much, it seems clear needs to exist in the world because predation exists. Right, It's kind

of this this arms race of speedy reactions. Yeah, you know. In a fun bit of synchronicity, we recorded this episode the same week as our fiftieth anniversary celebration of two

thousand and one A Space Odyssey. Yeah, and you know, the fourth first portion of that film, the Dawn of Man that we were discussing, you know, follows a population of hominids as they scrap by on hunter gathering existence, falling to predation from big cats from time to time, but then with a little help from an extraterrestrial sentinel, they take their first steps towards mastery of the planet

and the use of weapons. Yeah, the monolith arrives, then they suddenly realize, hey, I can use a taper femur as a as a club. But before that, the big cat I believe it's a leopard in the movies, a real leopard attacking somebody in a in an ape costume.

And it's frightening to watch, just and I'm not just saying it because I mean on two levels, because on one level the scene is very convincing, and then on another level, I'm thinking, oh, crap, that's a guy in an ape suit in a real carnivore has jumped on him. I can't help but have a like a primal response

to that. Yeah, So fossil evidence does inform us that early humans fell to cave lions, two savor tooth cats and false savor tooth cats, but they were also eaten by other animals, including giant hyenas, eagles, snakes, other mates, and is. Rob Dunn pointed out in a two thousand twelve Slate article about about fear, we even felt a giant predatory kangaroos. Yes, the predatory kangaroos. Yeah, the occult

occult of data. I believe it's it's called I've never even heard of this as far as I remember now. I'm embarrassed if you've told me on the show before, and I forgot. No, I do not think predatory kangaroos have come up before. And to call it a kangaroo, I've seen illustrations of what it might have looked like. And it doesn't straight up look like a thinged kangaroo

or anything, but but still similar creature. So the Ovens seems to support the idea that that creatures like this, not just the kangaroo, but big cats, et cetera, feasted on human flesh so well into the most recent hundred thousand years of human history, and we see this reflected

in the lives of modern primates as well. In places where large predators still haunt the shadows of primitive primate habitats, the young are still preyed upon, and where humans dwell alongside large carnivores, the young and occasionally even adults may fall to per day the world. That this world is also still reflected in our our our fight or flight responses, in the anxieties that we that define our lives, and

in our nightmares and our fantasies and our fears. I mean, really we think back to that that a lion man the first monster, Like, it makes so much sense that that should be like the early the earliest known uh you know, physical manifestation of our fears that we would actually like craft that well. I mean, if you go by one thing we talked about recently as well as the idea of the hyperactive agency detection device, that is a hypothesis about you know, where are our a tendency

to attribute agency to inanimate objects comes from? And but that says, you know, the things we really need to worry about there are two main things, animals and other humans. And if you combine the properties of the two, you've essentially got like the ultimate thing to be scared of. It's part human, it's part animal predator. It's both of

the things that worry us the most. Now this is interesting too, because when we think about our our ancient ancestors, we do tend to think about these two things, right, warlike abilities towards self uh and and their ability to fight back against predators and of course prey on other beings. I mean everything was expressed in that opening uh a segment of two thousand and one of Space Odyssey. But some anthropologists, such as Robert W. Sussman, the late Robert W. Susman,

I believe you passedway a few years ago. Uh. He argued that it was our that it was possibly not our ability uh to wage war against others, but rather our ability to cooperate with one another then enabled us to survive that era that we lived through as a prey species. Oh. I think there's tons of evidence that that social cooperation was a major factor in shaping the

animals we are today. So there we were this this prey species barely hanging on, but then developing the social connections and the technology to fight back against predators to sort of overtime remove ourselves from full participation in the food chain. Um. And in doing so, we've become something more than just a predator. Uh. We've become kind of a super predator. As Sarah Zelinsky pointed out in a two thousand fifteen Smithsonian dot Com article, humans are unlike

any other predator on the planet. Uh, and in in ways that that one might not instantly think. You know, obviously we use guns, and no other creature uses guns. You know, we we poison, we do all these other tactics. But everywhere else, predators prey upon the young, uh in particular. But humans kill healthy adults, especially when it comes to land carnivores and fish, and those adults, she she drives home in the article, these are the reproductive capital of

the species. So you know these news stories that talk about the tragedy of someone being struck down in the prime of their life, Well, that's that's the sob story for most of the animals that humans kill. And while again that the natural predation model is for things that have not achieved that level um or they have fallen off on the other side, the young or the old, and this is especially destructive for long lived and late producing species. Of course. Yeah. One example of all this

that Zelinski brings up is the stickleback. It's a fish that is just surrounded by predators. It just it has all the enemies, but the enemies mostly almost exclusively feed on young fries and subadults. Only five percent of the reproductively valuable adults are preyed upon each year. And that's a sharp contrast to commercial fishing, where fort of the

biomass is netted and its predominantly real reproductive adults. So from like an energy and reproductive standpoint, our kind of hunting and trapping and fishing and all that is putting a different pressure on wild populations the normal predation would, yes, and maybe a pressure that those wild populations are not

are not a position to sustain. Thomas rhym Chin of the University of Victoria research this uh this topic back in the nineteen seventies and found that while humans killed adult herbivores at about the same rate as non human predators quote, the harvest of adult carnivores by humans was nine times that of other large carnivores, which were mostly killing each other through competition, and the marine situation, according to Zelensky, is even worse, She says, marine predators harvest

about one percent of adult biomass each year. Humans take a median of four and as much as or more in extreme cases. So yeah, technology not only allowed us to sort of escape from the food chain, it allowed us to escape from the limits of the natural prey predator dynamic. That's really interesting. So even while we can make the point that predators are good and predators are very important for ecosystem health and we should not be trying to eliminate them to make the world better, they

are also very bad ways to be a predator. I mean you can see that even in non human animals, just when the wrong kind of invasive predator is introduced to an ecosystem and see the havoc at reachs. Right, Yeah, everything's out of balance. Yeah, but there can also be these these worldwide, world ranging super predators like us that

just we don't play by the rules, right. We're playing with god code enabled, you know, which means we can just kill every creature on a level and not have to, you know, whereas otherwise the game mechanics would maybe dictate that you could only maybe kill thirty of the enemies on a given level. And actually make it to the end where the real ding goes. Yes, are the real thing goes. But but one of the big questions is,

you know, what are we going to to be? You know, can we can we step down from the super threat predator throne? Can we actually uh implement more sustainable ways of of preying upon other animals in our world? And likewise, can we find more sustainable ways to deal with other predators that might be threatening the the the the environment that we have already unbalanced with our domesticated animals and

our crops and our the expansion of our territory. You know, can we become something that's ultimately more, more humbler and more sustainable ourselves. It's a great question. I mean, how how to be a predator that knows it's a predator and recognizes its power. Yeah. There's a wonderful quote from George Mombia again, and this is from a two thousand

fourteen Guardian article titled Destroyer of Worlds. He writes, is this all We are a diminutive monster that can leave no door closed, no hiding place intact, that is now doing to the great beasts of the sea what we did so long ago to the great beasts of the land, or can we stop? Can we use our ingenuity, which for two million years has turned so inventively to destruction, to defy our evolutionary history? I think we obviously can. The question is will we? I mean we we we

have the ability to defy our evolutionary imperatives. We do it every time we do something self sacrificing for a stranger, or every time people use contraception or you know anything as so like we we certainly have the power to do more than just what is dictated by our genes. But the you know, in any given situation, will people do it? And that's the challenge. Yeah, that's the challenge today,

That's the challenge going forward. But I think the it is important to put the emphasis on today as well, because it's all too easy just to say, well, it sounds like quite a problem. Hopefully somebody will figure that out in the years to come, or yeah, we'll get it where where humans are great, we'll figure it out. Hopefully we will. And I'm going to choose to be hopeful about it, because you know, I can. We can only act as as optimists if we're pestimist about it.

Then what can we do? Yeah, and if you want to be optimistic about our future, can a predator like us uh learn to live within its means and reform? You've got to at least acknowledge the base fact that, hey, predators ain't so bad. Yeah, acknowledge that they have an essential role to play in our environment. And scavengers too. We shouldn't leave out scavenger. Yeah, the scavengers are also they are they're the clean up crew. They're less, less glamorous,

but maybe even more useful. Yeah. All right, So there you have it, the predator, the scavenger. Uh. Well, hopefully this has UH forced you to re evaluate their roles. As always, check out stuff to Blow your Mind dot com. That's where we'll find all the podcast episodes. You just take a journey back through time there and listen to to uh a number of past episodes that have also dealt with biology and environmental issues and the future and

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Williams and Tory Harrison. If you would like to get in touch with us directly to let us know feedback about this episode or any other suggested topic for the future, or just to say hi, you can email us at blow the Mind at how staff works dot com for more on this and thousands of other topics. Does it how stuff works dot com. B