The Surprising Species That Everything Else Depends On | IN OUR NATURE (1)
This is a story about lions, and giraffes, and a microscopic little virus. It's also a story
about grass, and fire, and a bunch of these funny looking guys and what all of that has
to do with bombs, extermination and restoring ancient traditions and extinct ecosystems.
There's one big idea that ties all of these together, that even in a place overflowing
with life, there's one species that keeps the whole thing from crumbling down. And what
happens if we take an ecosystem that's fallen apart and we add that one key species back.
Can we fix it? Trace, and Emily and myself, we're going to be bringing you a series of
stories, featuring some incredible storytellers, some really passionate scientists and a bunch
of people who just really care about wild places. We're exploring the rules of life
that connect ecosystems, even half a world apart like Africa's Serengeti and a Native
American Tribal Community in South Dakota. And while we're at it, we're going to find
out a little more about our place in all of this. Hey, hi, Trace Dominguez Emily Grasley.
It is so good to see your faces. I am really excited to tell people about this thing, this
thing we've been working on, I don't know what to call it. Well, I guess it all started
with an idea that there's a different way to tell stories about nature that maybe we've
been doing it all wrong. A way to look at the,
Yeah, I feel like when I'm looking at a science story, I tend to get like hyper focused and
you get sort of a narrow lens on what you're looking at, and you have a tendency to miss
the other stuff that's around you,
Because really everything in nature is connected to so many other bits in nature. And often in ways that
you don't even expect if you're not looking, That's what this is all about. And what we're
going to do is show you how these big ideas, The rules of life
Are all connected and how we fit into that. I figured we'd start in the Serengeti. It's
an amazing place, but to tell all the stories that happen in that place, I feel like you
need to understand why it even exists in the first place. Wow. Wow. Yeah. That is Jahawi
Bertolli. He is this photographer and filmmaker from Kenya. I met up with him out in the Serengeti
because he's been going out there his whole life.
I mean, just look at the scope of this. Absolutely incredible. When you think of big drama in a place like
the African Serengeti, what's the first thing that pops into your head. Dung beetles, cheetahs.
Those are not the answers I'm looking for. The answer is these guys. No, seriously, you
are looking at the most important event on the entire Serengeti ecosystem.
It's eating grass, Joe. I don't, I don't. Okay. Okay.
I get it will, they are kind of goofy. They got that whole goatee thing going on. They
have that funny rear end kind of looks like somebody forgot to finish them, but they might
be the reason that the African Serengeti even exists.
Um, excuse me. I learned from the documentary Lion King that that is not the case.
I don't know how to tell you this, but, um, your childhood might've been a lie. Hey, have
you guys ever seen this pyramid thing? It's kind of a zoomed out way of looking at how
ecosystems are organized. So down at the bottom, you've got all the stuff that does photosynthesis,
the plants and everything like that. And here in the middle, you've got the stuff that the
plants and at the top, you've got the stuff that eats the stuff that eats the plants,
Everything at the top that kind of regulates everything underneath it. Right?
That is what I thought, but that is not how the Serengeti works. One thing you got to
understand about wildebeests, okay, is just how many of them there are, I mean wildebeests everywhere.
Joe, you went to Africa like one time. Okay. Yeah.
Jahawi helped. So not far from us, it's a big herd of wildebeest.
Is this all of them? Like all of them, Can you imagine? Not even a tiny bit.
Every direction that we look is wildebeests, as far as we can see.
Just in this little area, how many do you think there are.
Easily at thousands without turning my head. And then in the distance, we see this massive group
of zebra, several thousand zebra, which migrate with them. It looks like the horizon is made
of tiny black and white shapes, thousands and thousands. I mean, it's one of those things.
It's just, you can just keep counting. You took all of the zebras and the giraffes
and the antelope and the gazelle. If you took the next 12, most abundant herbivores on the
Serengeti, wildebeests would outweigh all of them.
How is that possible? That's the big question. That's what scientists wanted to know. How
can this place support so many of those funny looking wildebeests. Yeah. I don't understand.
Well, I'm going to tell you, but to do that, we have to go back in time to when the Serengeti
was not like this to the 1950s. So back then nobody really studied the Serengeti and scientists
were like, you know, maybe the first thing we should do is just count everything. So
they started with the wildebeests and the first year they counted like 250,000 wildebeests.
Then a few years go by and all of a sudden there's 400,000 wildebeests. I would say that's
a lot of new gnus. Emily, I love it. Gnu news, cause with
the G love it. Right. And then just a few years after that there's 700,000. Fast forward
a few more years, there's 1.4 million wildebeests. This is totally weird because based on everything
scientists knew up to this point, like large animal populations just don't do this. I mean
sure. Like fish, rabbits, plankton, they have these huge rapid population explosions, but
giant mammalian herbivores, that just doesn't happen. And actually people started to get
worried, like maybe this is too many wildebeests. Sure. The Serengeti is pretty great, but maybe
it can't support all of them, but then they realized something. You weren't looking at
a population explosion they're were looking at a rebound.
Okay. But rebounding from what? Like over-hunting or like an ice-age extinction? How many viruses
have humans completely eradicated from the earth? Like in the history of ever? The answer
is just two, smallpox and a virus called rinderpest. Rinderpest was this cattle virus. That's like
thousands of years caused civilization level plagues and famines that infecting and killing
cattle and other ruminants. Thanks to massive vaccination efforts, the last reported case
was in 2001, but if you go back a hundred years before that, rinderpest was accidentally
introduced to Africa in the 1890s. And by the 1900s it killed like 90% of the wild wildebeest
and Buffalo in east Africa, early to passed the vaccine came the 1950s. And by the 1960s,
this virus was basically under control. This virus had been keeping wildebeest populations
down for like 70 years. And it wasn't just wildebeests. When they came back, scientists
started seeing a whole bunch of other changes in the ecosystem, changes that were pretty
surprising. Are there lions in this part? you know I'm going to want to see some lions.
Okay. Yes, there are lions in this park, but we're not done with grass yet. Okay. So one wildebeest doesn't eat that much, but a million
and a half wildebeest eat more than 9 million pounds of grass every single day.
And that's enough to shape a whole ecosystem. You know, wildebeests are quite picky eaters
and they basically like short grass, you know? So like now here on the short grass plains,
this is perfect for them, but they also like new shoots. That's like, it's like a child,
like children are aren't even that picky. Zebra, they're not so picky. So they tend
to actually come through first and clear, clear the way. And then, then the wildebeests
can get what they want. Wow, exactly. Cooperative eating.
So if you eliminate this virus, you get more wildebeests, more hungry wildebeests means
less grass. And because more grass is being eaten, that means less fuel for fires and
less wildfire means that more young trees get to grow and more trees growing means more
food for giraffes and elephants and birds too. And of course more wildebeests means
more food for predators. Hey, now we're at the lion part, right?
Yes. Lion numbers went up and so did hyenas and other predators too. They are the Keystone
species of this ecosystem. Ding, ding, ding. He said the name of the
episode in the episode! It's a $6 million word. It's incredible to think of enormous groups
like this, just moving across this land, eating and pooping.
I mean, you can imagine the effect on the ecosystem. I've seen the migration and then
I've been lucky enough to see it quite a few times, but I can't help, but be blown away
every time by the sheer size, the number there's very few places left that can support these
kinds of herds. People had always just assumed that a Keystone
species had to be a predator, but here you've got these funny plant eaters, keeping an entire
ecosystem from collapsing. And, in fact, they're making it better. And today this million and
a half wildebeests are the largest herd of plant eating mammals on earth.
The population it's not still growing. I mean that wouldn't be sustainable, right?
No. I mean, you can't have wildebeests growing and like slowly taking over the universe,
they remain remarkably stable. That's the next mystery the scientist had to solve. I
mean, why? Oh, Trace. There are definitely lots of lions in this part. I was going to
say, we're at the top of the pyramid. We're getting to the lions. We're getting predators,
its going to be great. Oh and hyenas too. Okay. So a lot of stuff
gets eaten in the Serengeti by those guys at the top of the pyramid, the predators.
But some animals get eaten more than others. Let's say you're something small, like an
Impala. Well, chances are, you're going to die at the hands of something with fang, claws.
The pokey parts.
They have what scientists call a high prediction rate. But if you're something big, like an
elephant or a giraffe, not a lot is going to mess with you.
All right. All that makes sense. But where exactly are wildebeests then cause they're
big, but they're not elephant. Okay. The answer that
Scientists looked at, something that Emily knows a thing or two about bones, dead bones.
Oh yeah. Well actually bone marrow to be more specific
- sick. So here's the other thing you got to know about wildebeests. They move a lot
in the rainy season. The wildebeest are down in these grassy Plains where there's plenty
to eat. But as the dry season begins, the, see a wildebeest moves north this thousand
kilometer cycle repeats itself every year. It's one of the greatest animal migrations
on Earth. So, you know, when, when a lot of people think
about the migration, they, they think wildebeests cause they call it the Great Wildebeest Migration. But in
reality, there's a lot of other animals that actually go along parts of the migration.
I mean, you've got Thompson gazelle, you've got a lot of zebra. What's the, what's the,
the advantage of, of them traveling with the migration. If we were zebra and things, it
is a part getting to the best grazing. And then you've got safety and numbers and lots
