Shane Campbell-Staton: Inside each of us is the mind of a killer.

Our ancestors were hunters before they were even humans.

And the pursuit of prey has shaped our bodies, our brains, our culture, even our art.

We started hunting to fill our bellies, but as time went on, something happened.

-Game on.

-We got really good at it.

We started killing for other reasons: for status, for profit, and sometimes... -Shane, you're up!

-Just for fun, and the world has never been the same.

With the help of our brains, tools, and culture, hunting by humans can re-shape ecosystems, alter the chemistry of the environments we rely on, and steer the very process of evolution because the greatest predator Earth's ever known, it ain't the great white or even T. rex.

Baby, it's you and me.

Woman: Game over.

Shane: Welcome to the age of humans... where one species can change everything and what we do reveals who we truly are.

This is "Human Footprint."

♪ (weapons clattering) Shane: You might not think of yourself as a predator.

I've certainly never killed an animal for its meat.

Don't get me wrong, I love me a good steak.

It's just that for me, living in a city, there are easier ways to get one.

Today, eating meat has become so effortless that many of us have forgotten what it means to be hunters, but that doesn't mean the killer inside us is gone.

Even in the age of grocery stores, some people choose to hunt.

(gunshot) (insects chirping) Man: I feel like hunting's something that should be hard.

It shouldn't be super easy.

Shane: This is my friend Ryan Long.

He's a biologist who studies large mammals.

He also hunts them, not because he has to, but because, like millions of others, he chooses to.

♪ Ryan: Ah, so this is the camera trap I've been using to scout our property here for deer-hunting over the course of this summer.

I'll start putting these out probably two months before season opens.

So before you even bust out the bow, like, you've already put in, like, weeks' or months' worth of work... Ryan: Absolutely.

-in trying to understand what's going on.

-Absolutely, yeah.

Man, that is a lot of time and dedication.

Yeah, yeah, it's fun, you know?

It's kind of like, uh, I don't know if this is the best analogy, but it's kind of like solving a puzzle.

Do you think being a biologist makes you a better hunter, or being a hunter makes you a better biologist?

Ryan: Think it goes both ways.

-OK. -The thing that, um, originally got me into or interested in being a biologist was my upbringing as a hunter.

Shane, voice-over: I get the sense that Ryan the biologist gets just as much out of these trail cameras as Ryan the hunter.

Watch this.

This is in the middle of the night.

I caught this picture.

There's two does sort of grooming each other.

Shane, voice-over: The cameras give Ryan a leg up on his prey, but other decisions, like using a bow instead of a rifle, actually make his job harder, not easier.

That's part of the ritual.

I spend months shooting my bow every morning, daily, to make sure that I'm-- that when that moment comes, that I don't screw it up.

Shane: Yeah.

(meat thuds) Shane, voice-over: The day before I got here, all that practice paid off, and Ryan was just about to break the deer down into cuts of meat ready to cook and eat.

So how long does it take to get from here to burger?

Probably a few hours.

-OK. -Um, it's not too bad.

Shane, voice-over: As a meat-eater and a biologist, I thought I had an OK grasp of anatomy.

Turns out, I still have a lot to learn.

Ryan: These are the tenderloins.

-That's what a tenderloin is!

-These are tenderloins.

Yeah, they're underneath of the spine.

If you had asked me where a tenderloin was... -Heh heh!

-on an animal, that is definitely not where I would've expected.

-Yeah.

-I'm, like, very quickly starting to realize, like, how disconnected I am from the meat that I have bought in grocery stores.

Ryan: For better or for worse, that's true for a lot of people.

Shane: Yeah.

Shane, voice-over: And when you're choosing an animal to take, does it matter to you if it's a doe or a buck or...?

For me?

No.

It needs to be a legal animal.

Shane: OK. Shane, voice-over: A legal animal.

In other words, an animal Ryan was allowed to kill.

In the U.S., strict laws govern how, when, and where we hunt, and, of course, how many animals we can take.

So you want to shoot a deer?

Best believe you better have a deer tag, and don't you go shooting one out of season.

Of all the world's predators, modern humans are the only ones so efficient that we have to invent rules to limit ourselves or else our prey disappear.

Shane: Wow.

Ryan: There you go.

The backstrap of a deer.

-God, that's satisfying.

-Yeah.

Strangely enough, I'm also really hungry now.

-Ha ha ha ha!

-I was like, "I would totally cook this."

Ryan: Yeah.

Shane, voice-over: Sitting down with Ryan and his family for some wild elk fajitas, I'm starting to understand the appeal of hunting.

Shane: Do you think it's a different experience for you than, like, somebody who just, like, went and grabbed some steaks from the local store and cooked them up?

Ryan: For me, it doesn't remind me of a trip to the grocery store.

This reminds me of... blood, sweat, and tears.

I can envision the very moment that I shot this bull, how many miles I was, how many thousands of feet below my basecamp I was.

Shane: Yeah, I must admit, I don't think I ever remember a moment associated with, like, any burger I've ever had.

-Ha ha ha ha!

-If I had to, like, drag the burger, you know, several miles outside of the woods, I'd probably remember it a bit more.

Shane, voice-over: So can we all be more like Ryan and reconnect with our meat?

What would that look like?

Ah, yeah, it's a struggle for me.

I want--I would love for more people to be connected with the natural world in this kind of a way.

-Mm-hmm.

-But one of the reasons that I am able to do the things that I do like this is because there's not that many people that do it.

Shane, voice-over: And the people who do hunt don't hunt very much.

There's not much point in killing more than you can eat because you can't sell it.

Ryan: Wildlife in North America are a public trust resource, and it is illegal to harvest any wild game animal and sell it for profit.

The reason why we had this massive decimation of wildlife in North America in the 19th and early 20th centuries was because, at that time, wildlife were a commercial resource.

Shane, voice-over: In other words, those 19th-century hunters could sell what they killed.

When wild animals are commodities, and more killing means more profit, we don't have to guess what happens next.

We've actually seen it here in the Chesapeake Bay.

Announcer: This is the 45th Annual World Championship Calling Contest.

All right, guys, we're gonna go ahead and get ready to get started if everybody can find their seats.

Shane: What is this gonna be like for me?

It's a championship.

It's like, if I'm a... if I'm an amateur sitting on my bunk bed playing a guitar learning how to play it, tonight you're gonna go see Jimmy Page blow a duck call, so to speak.

Shane: Ha ha!

Yeah.

(overlapping duck calls) (Piano and viola playing Bizet's "Habanera") ♪ Man: What I love about it is how you'll-- you see 'em assume this body posture, and they are channeling their inner duck.

Shane: The duck is me, and I am the duck.

Shane, voice-over: If you asked me a year ago where I might be today, the World Waterfowl Calling Championship would not have been on my list, yet here I am.

Man: He really leaned into that.

These guys are artists.

They're duck hunters themselves, but they've elevated the calling to art form.

Shane, voice-over: This is duck-hunting legend Ramsey Russell.

Ramsey: Welcome back to "Duck Season Somewhere."

I'm your host Ramsey Russell.

Have you ever thought about who we are as a duck-hunting culture?

Announcer: In first place, with a score of 786, Mr. Halton Hill.

(applause, cheering) Shane, voice-over: I'm here in Easton, Maryland, for the annual Waterfowl Festival.

This place has a little bit of everything: duck-calling, decoy-carving, retrieving-dog demos, you name it.

If you love ducks, this event is a can't-miss... yet, just a century ago, the Chesapeake Bay's ducks were all but gone.

Understanding what happened, and why there are still ducks to hunt today means getting into the mind of the modern hunter.

Ramsey: Toss it out, kinda between here and those two mallards right there.

-OK. -Yeah.

(decoys splashing) Create a little flock.

Shane: How important is the decoy in this process?

I mean, birds of a feather flock together, you know, and it makes them think there are birds using this area, so this might be a comfortable area they're looking for, so decoys are absolutely essential to the process.

Shane, voice-over: Hunting ducks means getting cold, wet, tired, and often bored.

Ramsey loves every minute of it.

Shane: So what is your favorite part of this process?

Ramsey: It'd be like saying what's my favorite part of an apple pie.

Is it the cinnamon, is it the ice cream, is it the crust?

It's kind of the whole thing, it's the whole drama, the whole package, it's the people, the story, how that duck, the pursuit of this wild duck, connects people to past generations through this hand-me-down tradition.

It's like putting together a big gumbo.

-Mm-hmm.

-You know?

What's your favorite part of the gumbo?

Just the next bite.

-Yeah.

Ha ha!

-Ha ha!

You know?

I think there's, like, you know, a contrast between, you know, hunting and, like, a love of nature.

You know, it's like, "Oh, like, how can you love nature if you come out to kill nature?"

Ramsey: I ask myself that-- I ask myself that a lot as I get older.

I mean, I'm wearing waders so I can get-- so I can get crotch-deep into their world.

You see, these decoys and the calls and the waders and the gear is so I can climb into that part of the world, a wilder world, but still, that's the magic of duck-hunting, not the trigger pull.

Shane, voice-over: But Ramsey's after more than just an experience and a meal.

For him, the whole process goes deeper.

Ramsey: I hear a wood duck.

Shane, voice-over: Eating what he hunts feeds Ramsey's connection to nature and to a part of himself.

Ramsey: Now comes the part where we take 'em home, we prepare the bird, we make a great meal for 'em, and we feed ourselves and we feed our family and we feed our culture, we feed our tradition.

Shane, voice-over: The way Ramsey tells it, tradition is the soul of duck-hunting.

The Chesapeake Bay is one place where that tradition was born and nearly died along with the ducks themselves.

(film projector whirring, ducks quacking) (gunshot) When I think back, going back to yesteryear on the Chesapeake Bay, back in the-- gosh, what the first people in Havre de Grace, what those first people must have seen when the wintering populations of ducks come down.

Shane, voice-over: No one was tracking duck populations back then, but 19th-century writers seemed to run out of superlatives to describe their numbers: "Innumerable hordes."

"Numbers beyond credence or computation."

Ramsey: I imagine black smoke... clouds of birds, indescribable numbers of birds that-- it must have sounded like a freight train to have that many wings.

The Chesapeake today is just--it's just a... a skeleton of its former self.

(gunshot) Shane, voice-over: A turning point for ducks on the Chesapeake was the rise of market hunting, killing ducks to sell them to restaurants and markets.

(film projector whirring) In the late 1800s, market hunters shot ducks by the millions.

Ramsey: At the height of market hunting, Chesapeake Bay canvasbacks brought top dollar.

Shane, voice-over: Canvasbacks are big ducks with rust-red heads that dive for their dinners, and it's those dinners that made them such a delicacy.

Ramsey: There was a lot of wild celery, and they say the meat on a-- on ducks that ate purely wild celery was just very delectable.

And you are what you eat, right?

Can you imagine going out and taking your wife to go eat a $900 dinner today?

♪ Shane, voice-over: In the late 1800s, market gunners could sell canvasbacks for one or two dollars apiece, the equivalent of $30 to $60 today.

♪ If you wanted to make some money, the only limiting factor was how fast you could kill ducks.

And, as usual, our inventiveness was up to the challenge.

Shane: This is a hell of a place you got here.

Well, I've been, uh, actively collecting things since grade school.

Ollie Joseph: ♪ Someone left the door ajar ♪ ♪ Now I'm here to stay... ♪ Shane, voice-over: This is Ronnie Newcomb.

He's a collector of just about anything to do with the Chesapeake.

He grew up here as a hunter and, later, a taxidermist.

Ronnie loves old guns.

In fact, you can see the whole evolution of duck-hunting firearms in his collection.

Shane: So, if you were out hunting with this, would this be something that you use to take down a single bird, multiple at a time?

-Multiple.

-OK. Yeah, that would be the purpose.

Now, it wouldn't be for-- it wouldn't be for a sportsman; it would be for a hunt-- a killer, you know, meant to kill a lot of birds, you know, in one shot... Shane: OK. or numbers because, at one time, there were millions, literally millions of canvasback ducks, and they reached as much as $2.50 a pair, $2 and a half a pair.

-OK. OK. -That was a lot of money.

And especially if you killed 50 of them in one day.

-Yeah.

-Then you were getting rich quick, right?

Shane, voice-over: Mo' ducks, mo' money.

From flint to percussion to shell guns, the tools of the trade kept getting bigger and more efficient, and I was about to see the largest duck-hunting gun in existence.

Shane: So...this is the biggest gun I've ever seen in my entire life, easily.

Ronnie: Mm-hmm.

Um, how did we get from a normal-size shoulder gun to this monster?

Well, again, they were-- the more shot they could put in there, the more opportunity they had to spread it through the flock and knock 'em out.

Shane, voice-over: A punt gun like this one could kill 50 ducks with a single shot.

Shane: So I imagine nobody's putting this to their shoulder and aiming it at anything?

No, this weighs nearly about 225 pounds.

(chuckling) My God.

Wow.

OK. -It's over 10 foot long.

-All right, so this is essentially a cannon that looks like a shotgun.

-Yeah.

Yeah.

Heh heh!

-OK. Shane, voice-over: With weapons like these, it's hard to believe that market hunting wasn't the end of the line for the canvasback and other Chesapeake Bay ducks.

But as their numbers crashed at the turn of the 20th century, ducks found a surprising group of advocates.

♪ Ramsey: Leisure hunters began to emerge.

There arose this massive conflict to where a hunter shows up to his chosen spot and he can't shoot a lot of ducks because those old market hunters had killed 'em all.

And the rich folks, the rich sportsmen just-- they went to their political buddies and they said, "We gotta do something about these market hunters, man.

They're ruining everything."

And they began to establish laws that marginalized market hunting.

Shane, voice-over: In the early 20th century, the federal government passed sweeping laws protecting birds from commercial hunting, laws that basically said, "Yes, you can hunt ducks, "you just can't shoot as many as you want and you can't sell them."

Now ducks had allies: sportsmen who didn't hunt for a living, but valued hunting the way Ramsey does, as a lifestyle.

Ramsey: Get down, get down, get down.

Down, down, like way down!

(two gunshots, water splashing) Atta girl!

You think she was ready to retrieve?

-Oh, man, she was on it.

-Ha ha ha ha!

-She was on it.

-This is a hen wood duck, one of our bread-and-butter North American species.

And, you know, can you believe that at one time in American history, it was on the verge of extinction?

This species was on the verge of extinction.

Now it's one of the most ubiquitous species in North America.

Shane, voice-over: The wood duck isn't alone.

In North America, ducks, geese, and swans are among the only birds that are more abundant now than they were 50 years ago.

Hunting devastated ducks in the Chesapeake, but hunters are also playing a pivotal role in their resurgence because you can't hunt something once it's gone.

Shane: And you said something that was, like, really, really powerful: "To touch something"... Ramsey: Yeah.

"is to understand it, and to understand it is to love it."

Ramsey: Yeah.

Yeah.

You know, and I-- I get that.

Ramsey: We hunters touch it, we love it.

-Yeah.

-I love that duck.

Not individually, but I love ducks.

-Yeah.

-Even though I took the one.

There's no denying that I'm somehow related to an atavistic former self generations ago that went out there and clubbed something to eat.

Shane: Uh-huh.

Shane, voice-over: I can see how Ramsey's primal urge to hunt, along with a deep connection with nature and hunting tradition, makes him such a passionate conservationist.

Yet, here in the Chesapeake, that same spark, kindled by our ingenuity and fueled by profit, ignited an inferno that nearly consumed a once-inexhaustible resource.

Duck hunting reshaped the Chesapeake Bay ecosystem.

But as Top Predator, our killing can also reverberate around the world.

You just have to think bigger.

Frank Bentley: ♪ Who knew I would make it this far?

♪ ♪ They hated, they never believed me ♪ ♪ Yo, I will never drop the ball ♪ ♪ I know I make it look easy ♪ ♪ You ain't fitted for it because you all cap like ♪ Man: Welcome to the Land of Giants here.

Wow!

Aw, see, hell to the yeah.

This is crazy.

How many whales do you have here?

We have--every species that's on the planet is represented in our collection.

Shane, voice-over: Nick Pyenson is a biologist who studies ancient whales, so he spends a lot of time with fossils that are tens of millions of years old.

But he's no stranger to living whales, either.

♪ Nick: If there's a question about whale diversity and evolution, you can probably find an answer... -OK. -with one of these specimens.

Shane, voice-over: This is Nick's happy place, a Smithsonian storage facility in Maryland he calls "The Whale Warehouse."

Shane: And I know every collection has its unique smell... Nick: Yeah.

but what the hell is it that I'm smelling right now?

Nick, chuckling: So you're smelling whale oil just everywhere.

-OK. -And it's whale oil that's hundreds of years old that still hasn't really leached out of the bones.

Oh, it's seeping out of the bones now?

Yeah, let me have you take a deep whiff of this one over here.

Shane: Heh heh!

OK. (inhales) Oh, yeah, that's-- You just get way up in there, huh?

Well, it's, you know, biology.

You got to get... All up in the bidness.

All right, let's... (sniffs) Yeah.

-Ha ha ha!

-Oh, God, yeah.

Nick: So I, you know, that's--you know... (Shane coughs) I have my own way of describing that.

It feels like knowledge to me, but maybe to you, it's just, you know, death warmed over.

It does not smell like knowledge to me.

-OK. -I'm sure there's the ton of knowledge here, but it is funky.

-Ha!

-It's funky.

I'm not going to lie to you.

Shane, voice-over: Now, I've seen a lot of biological specimens in a lot of museum collections, but nothing like this.

Nick: So here are the jaw bones.

-What the hell?

-Ha ha ha!

These are the jaw bones of a blue whale.

Bruh.

This is ridiculous!

Inside are the jaw bones of a bull sperm whale that was 60 feet long.

The owner of the blue whale jaw bones was 92 feet long.

-Whoa.

-And here's the crazy thing.

You are looking at the largest single bone in the history of life.

There is no dinosaur bone, mammoth tusk, nothing is as big as this bone.

-Wow.

-So this is it.

And we'll never collect something like this again.

These are blue whales from the Southern Ocean, and this was collected at a time when there was still a lot of whaling going on.

Shane: Yeah.

Especially in that part of the world, where some 2 to 3 million whales were killed.

This was one of them.

(whale song) Shane, voice-over: Even the biggest animals that ever lived aren't off limits for the planet's Top Predator.

But why?

I mean, there's got to be an easier way to eat.

Nick: So, here we have a gray whale skeleton that's at least a thousand years old.

-OK. -And it's from the coast of North Carolina and...

I can show you right here... Shane: Uh-huh.

you have these nice butchery marks right there.

Our ancestors in the human lineage were using stranded whales as a resource, either for meat, maybe for the bones.

Shane, voice-over: But at some point, stranded whales weren't enough anymore.

So, at some point, you have--there's, like, two dudes, like, sitting on the beach, and one turns to the other, is like, "Oh, man, you see that gargantuan thing out there?"

-Let's go get it.

-"Bet money."

-Ha ha ha!

-"Bet money I can kill it."

I think that bet probably ended badly most of the time.

Shane: Heh!

Yeah.

The technology to actually have a successful hunt really didn't come together until about a thousand years ago.

And the purpose of that hunting, was it for food or other purposes?

For--mostly not for food, but for oil.

Whale oil was really, really good.

Great lubricant, burned really cleanly.

Whale oil lit New England in the middle to late 19th century, and it was only with the discovery of actual petroleum, oil from the ground, where it no longer made economic sense.

Shane, voice-over: Now, as weird as it seems to power our lives by digging up fossil fuels, it's so much weirder to think we used to burn whales.

And even after petroleum products replaced whale oil, whaling technology continued to get more sophisticated.

-So this is a harpoon head.

-Oh.

-This is more recent technology.

-OK. That--God, that's heavy.

So that doesn't seem like the pointy tip of a spear, right?

-Yeah.

-But that's actually behind two grenades that sit at the end of probably a 6-foot-long harpoon.

It's launched at the whale, and then it doesn't explode until it's actually-- the head is inside the body cavity.

Ooh, wow.

That is not for the faint of heart.

-Yeah.

-That's incredible.

Shane, voice-over: The efficiency of 20th-century whaling had a devastating impact.

We didn't actually know how many whales there were in the world's oceans, so why did it matter?

There was just no limits.

There were so many whales in the Southern Ocean, why not?

So, by the U.S. Marine Mammal Protection Act in 1972, 99% of the blue whales that were alive in 1900 were gone.

How do we know that number specifically?

Whaling is an industry that kept logs and data.

There are 37 volumes like this, and they all have page after page after page of individual whale and when it was killed, the whale number, male/female, and measurements of its carcass.

Shane: Mm.

Shane, voice-over: Flipping through these pages is almost like watching whales disappear all over again.

People guess that it's in maybe the few hundreds.

-OK. -600, 800 blue whales, globally, made it through the 20th century.

Shane: Wow.

Shane, voice-over: It turns out that these ocean giants have a massive role to play in marine ecosystems.

The way I think about it is, it's kind of like a giant ecological experiment... Shane: OK. was conducted through the whaling industry.

-Uh-huh.

-What happens when you remove 2 to 3 million whales in a very short period of time?

-Mm-hmm.

-We're talking--you could add up the biomass of all the wild mammals on the planet today.

Just think about tigers, lions, elephants... Shane: Mm-hmm.

all the wild mammals on the planet.

The level of biomass of whales before industrial whaling was some 2, maybe 3 times as large as that.

♪ So the number of whales that were removed... Just in a few decades, not even in a hundred years.

was 2 to 3 times the total biomass of all wild mammals... -Today.

-that exist on this planet today.

Shane, voice-over: And it's not just the whales themselves that the ocean lost, but all the things they did, like eat.

Nick: So here's a jar of krill.

Shane: OK, and this is the stuff that giants are made of.

Exactly, yeah.

It's a really good way of putting it, and in the Southern Ocean, there's more krill than basically anything else.

So, if the giants are gone, are our oceans just stocked full of krill now?

Yeah, so, that's the Krill Paradox, right?

Removal of whales... Is that what it's actually called?

That is great.

That's what it's actually called in literature, yeah.

People have been calling it that for decades-- the Krill Paradox.

Shane: Wow.

That'd be a great band name.

Nick: Yeah.

So, the Krill Paradox is that with the removal of whales, you expect there'd be so much more krill.

Turns out that's not the case.

Krill have actually dropped in numbers.

How does that work?

So there's a feedback loop here and it goes back to whales feeding and then pooping in the upper layers of the water column.

-OK. -Right in the photic zone.

Shane, voice-over: The photic zone is the layer of water near the ocean's surface where light can penetrate and plant life can grow.

Whales spend a lot of time deep underwater, but they have to surface to breathe, and it turns out, that's where they do most of their pooping, too.

So, when whales aren't there, they are not fertilizing the oceans as much as they otherwise would be.

They're mobilizing nutrients, so that includes phosphorus or nitrogen, and phytoplankton, zooplankton, like krill.

They're going to need these nutrients to build these incredibly productive, healthy food webs.

So whales are dependent on the krill, but the krill are also dependent on the whales.

Whales are essentially, kind of in a way, farming krill with their poop.

And that's why we call them ecosystem engineers.

The chemistry of the oceans, too, changed with the removal of all those whales.

Wow.

Wow.

So a world with many more whales is probably a world we want in the future.

That's the way I think about it.

I think it's a source of wonder to live alongside some of the largest species, not just on the planet right now, but to have ever evolved in the history of life on this planet.

Shane: Mm.

How lucky are we?

And we nearly snuffed them out.

Shane, voice-over: And we changed the entire ocean along the way.

Now, the fortunate thing is, they didn't go extinct.

So I kind of think we have a second chance in the 21st century to make a greater impact.

Shane, voice-over: If whales aren't safe, how could any species be?

What can an animal do once we decide that it's more valuable dead than alive?

Well, maybe it can change.

(insects chirping) Gorongosa National Park in Mozambique is one of the jewels of Southern Africa.

But researchers here noticed something unusual.

Many of the park's elephants never developed tusks, so, a few years ago, I came here to try and figure out why.

So today, we're just going to go up near Hippo House, near Urema Lake, and then we drive down the river.

Shane, voice-over: This is my friend Dominique Gonçalves.

She runs the elephant ecology project here.

Knowing where the park's elephants are is a big part of her job, but they don't make it easy.

Is this a perfect morning for you, going out and looking for elephants?

-It is.

Ha ha!

-Yeah.

Ha ha!

Shane, voice-over: For such massive animals, elephants can be surprisingly hard to find, particularly Gorongosa's elephants, which have a reputation for being elusive and aggressive.

The first time I was here, I spent 3 weeks driving around the park and didn't find a single elephant.

Then again, I wasn't with Dominique.

You're joking me.

This is very recent.

No?

Well, we got a tree in the middle of the road.

Elephant pushed it over looking for palm fruits.

(chuckles) Elephant maintenance.

Yeah.

Shane: Ele--I like that.

(both chuckle) Shane, voice-over: We're clearly on the right track.

Elephants were here just before we arrived.

Incredible to me that an animal that big can be so cryptic.

-And ambush you.

-Yeah.

Right here.

Hmm.

(speaks native language) Shane, voice-over: Dominique thinks the elephants might be headed to a waterhole called Paradise Pan for a drink.

Dominique: Can you see it from there?

Shane, whispering: Yeah.

I see her.

You can-- (speaks native language) You can hear something off in the palms.

(elephant trumpets) Dominique: We have arrived.

Shane: OK. (both chuckle) Welcome to Paradise.

Heh heh!

♪ Shane, voice-over: When you see them up close, the tuskless elephants are hard to miss.

Female African elephants normally have tusks, just like the males, but more than a third of Gorongosa's females have no tusks at all.

To understand what happened, you need to know a little about Mozambique's history.

Dominique: Well, you have to remember, Gorongosa was one of the battlefields.

-Mm-hmm.

-Yeah?

And a lot of bad things happened in this place during the war, yeah.

Shane: Yeah.

Shane, voice-over: Dominique is talking about the Mozambican civil war, a bloody conflict that raged from 1977 to 1992.

You can still see the scars of war all over the park.

Man: ♪ You know I can't help with this ♪ ♪ 'Cause they know they can never touch this ♪ Shane, voice-over: This is Pedro Muagura, Gorongosa's Park Warden.

When he's not managing the park's million-plus acres of forest, wetland, and savanna, he's getting his hands dirty planting trees and singing for anyone who will listen.

(both singing in native language) Shane, voice-over: The Gorongosa I'm seeing today is very different from what existed here before the war.

Shane, voice-over: The structure we're standing on right now used to be a hotspot for tourists.

They called it "Hippo House."

Ah.

Yeah.

Shane, voice-over: Pedro's first experience in Gorongosa was in 1992, right after the civil war.

Mm-hmm.

Shane, voice-over: The problem was, there weren't many animals left to identify.

Wow.

Shane, voice-over: The war had devastated the park's wildlife.

(gunfire) OK. Shane, voice-over: Many species were hunted to provision the armies with meat.

But elephants, with their ivory tusks, were an even more valuable commodity.

Gorongosa's elephant population crashed from 2,500 to less than 200, a loss of more than 90% in just 16 years.

And half the female survivors were tuskless, nearly 3 times as many as before the war.

Researchers began to think that the intense ivory-poaching during the war had literally changed the face of Gorongosa's elephant population.

(elephant trumpeting) ♪ It wouldn't be unprecedented for hunting to drive evolution.

In fact, one of the earliest measurements of natural selection in the wild comes from foxes hunted for their furs in Canada.

Some foxes carried a genetic mutation, giving them a silver coat instead of red, making their pelts more valuable.

But after a century of hunters targeting these silver foxes, that mutation became rare.

But elephants aren't foxes.

They live for decades and reproduce slowly.

(elephants grunt) Could poaching cause elephants to evolve in just 16 years?

(elephant grunts) When I arrived in Gorongosa, we knew that the elephants were devastated by the civil war and that tuskless females, once a rarity, had become more common.

Thanks to researchers like Dominique, we'd also learned that tuskless females often have tuskless female offspring.

(birds chirp) But no one knew which genes encoded tusklessness, or whether those genes had undergone natural selection during the war.

So we needed elephant DNA.

♪ (click) We're looking for genes that are consistently different between elephants with and without tusks.

And in Gorongosa's elephants, we found two.

One is a gene called AMELX.

In humans, mutations in this gene cause abnormal tooth development.

It turns out Gorongosa's tuskless females also carry mutations in AMELX, and we think it prevents them from growing tusks.

After the civil war, tuskless females were among the last elephants standing, and they passed that trait on to their female offspring, who now live in a population very different from the one their mothers grew up in.

Human hunting really did drive the evolution of the world's largest land animal.

Pilot: Yeah.

Pilot: Yeah.

Yeah.

(pilot chuckles) Shane, voice-over: Elephants can't decide whether or not to grow tusks, but here in Gorongosa, we decided for them.

Shane, voice-over: Seeing the park from above is also a good reminder that this story isn't just about elephants.

Elephants are connected to everything else here, too.

They have an oversized role to play in this ecosystem, and their tusks are part of that role.

Dominique: The elephants use them to, you know, the tusks to debark trees and dig holes and fight the males.

And if an elephant can't knock down that tree or eat properly, how does that have this domino effect all the way through the ecosystem and then to us?

So there's many, many questions.

Shane, voice-over: Questions that Gorongosa's elephants can help us answer someday.

Now that they're better protected from poaching, today, at more than a thousand strong, this population is bouncing back.

Dominique: For me, it's like how--it shows a lot of how resilient they are.

Well, they carry this past, heavy past, this trauma... Shane: Mm-hmm.

which, you know, makes them extremely... aggressive or less tolerant to people.

-Yeah.

-To us.

Shane, voice-over: But maybe these elephants can sense that they're not being hunted anymore.

OK, everyone stay quiet.

Shane, whispering: Wow.

(elephant snorts) Dominique, whispering: That's him.

Dominique, voice-over: Can't yet prove it, but you can see that some of them are becoming more tolerant.

I don't think they forget.

Shane: Yeah, an elephant never forgets, but maybe they can be on the road to forgiveness?

Yeah, forgiveness.

Exactly.

It's not forgetting, but might be forgiveness.

♪ This will never not be incredible.

Shane, voice-over: The story of Gorongosa's elephants is the story of hunting everywhere: they have something we want, whether it's ivory, oil, or meat, and we're all too capable of taking it.

But to be the world's Top Predator, we also had to eliminate the competition, and so, one by one, the planet's top wild hunters have become the hunted.

(wolf howling) Man: This is an MB-750 trap.

This is the popular and probably most-used foothold wolf trap being used in the states of Montana and Idaho right now.

And if you lift that, you'll see that that's a lot of trap.

Oh, that is a lot of trap.

DMX: ♪ Move less, dog say so... ♪ Shane, voice-over: Carter Niemeyer has been trapping animals, including wolves, his whole life.

DMX: ♪ I got at least 3 kills ♪ ♪ Even though my last album only did... ♪ Shane, voice-over: But these days, he mostly hunts for bugs in his garden.

He catches them, too, but only with his camera.

Carter: I started as a professional trapper under U.S. Department of Interior.

It's fascinating to me to think of the government essentially acting as, like, the apex predator in an ecosystem.

From the time of European settlement and people moving from east to west across the United States, they brought their livestock with them and they wanted to be farmers and ranchers and whatever to make a living.

Shane, voice-over: Raising livestock in wolf country was and still is a recipe for conflict.

People wanted wolves gone, and it wasn't long before eradication became the official government policy.

Carter: It was a war on wolves.

It was trapping, snaring, shooting, and probably the most effective way to reduce wolf numbers was with poison.

The battle started, and we never stopped doing it.

It's just been a way of life.

Shane, voice-over: Wildlife Services, the agency Carter worked for, is very much intact.

To this day, its mission includes "predator control," in other words, killing predators like wolves when they become a problem.

We have the capability to target and probably eliminate any species we want to if we really, you know, pulled out the stops and did everything we were capable of doing.

During the time that you spent there, did you kill wolves yourself?

I've killed a total of 14 wolves in my life.

Um... many other folks have killed a whole lot more than me.

Shane, voice-over: Our campaign to exterminate wolves left the American West wolf-free, but it wasn't the utopia we'd hoped for.

♪ Man: In the absence of predators here for about 70 years, when they were eradicated in the early 1900s, we saw elk populations growing quite rapidly and being quite overabundant.

Shane, voice-over: Dan Stahler is the Lead Biologist of the Yellowstone Wolf Project.

When he isn't out tracking wolves, you can find Dan exploring the mountains with his dog, Argos.

♪ Biologists working in Yellowstone began to realize that without wolves, this ecosystem was out of balance.

Pressure grew to reintroduce wolves inside the National Park, and in 1995, 8 wolves from Alberta, Canada, were released in Yellowstone.

(wolves howling) ♪ Dan: So we're entering Lamar Valley now.

This is one of the more beautiful places of the park.

♪ To me, it's been sort of the heart and soul of wolf recovery, wolf reintroduction.

And of course, here we are 26 years later, a lot of our understanding of wolves has played out in this very valley.

Shane, voice-over: For the last 25 years, biologists like Dan have watched Yellowstone National Park react to the reappearance of wolves.

Elk began to use the landscape differently, feeding farther from the rivers.

The riverside vegetation the elk had once eaten grew back and created new habitat for beavers and songbirds.

The reintroduction of wolves showed that these predators are connected to every part of the ecosystem.

In killing their prey, wolves also brought parts of Yellowstone back to life.

Dan: This is pretty fresh, so I guess they killed it in the night, maybe this morning.

Oh, wow.

And you can see it doesn't last long when you got, you know, 27-some-odd wolves feeding.

When you walk up to these, typically, you know, do you do, like, the crime-scene investigation thing, where you have the glasses and then you kneel down?

Dan: Yeah.

Shane: It's like, "Looks like the party got wild"?

Dan: Exactly.

You know, you look for your blood, your drag trail, the blood stains.

Shane: Oh, yeah.

You're looking for all the clues that, as a biologist, helps you piece together the story of this predation event.

Shane, voice-over: This isn't just morbid curiosity.

Analyzing wolf kills like this one helps Dan understand how they hunt and how that affects the rest of the ecosystem.

(wolf growls) Dan: The biology of the wolf as a hunter, they're limited by their biology.

They've got their face, right?

Shane: Yeah.

They've got their mouth.

That's all they have.

Shane, voice-over: Modern humans, on the other hand, can kill from a distance, without putting their bodies on the line.

The result is that humans and wolves have very different impacts on ecosystems.

(wolves barking, howling) Human hunters often seek out the biggest, healthiest animals to kill, but wolves usually target old, diseased, or newborn animals, leaving the prime specimens alone.

Outside the park, easy prey are the foundation of an 80-billion-dollar-a-year ranching industry.

In the U.S., more than 600 million acres are dedicated to cattle, sheep, and other livestock, and when it comes to vulnerability, it's hard to top a newborn lamb.

Woman: OK. Are you ready for this?

-Yes.

-There you go.

Shane: Oh, goodness.

Oh, my goodness.

Oh, ho ho ho ho ho!

(chuckles) Oh, I can't stand it.

Ha ha ha!

Well, now, I was a reporter.

I had a sheepman give me an orphan lamb.

And I sat it on my lap and looked into these beautiful, beautiful dark eyes and fell madly in love.

DMX: ♪ Hey, hey, come on, I run ..., yeah ♪ Shane, voice-over: This is Cat Urbigkit, a rancher and author who's turned the real-life lambs she raises into lovable children's-book characters.

Like many ranchers today, Cat doesn't want wolves gone, but raising sheep in wolf country means taking measures to protect them.

(barking) Cat: Hi, Harriet.

What's up?

Shane: Oh, that's a big girl.

Yeah.

Her name is Harriet the Horrible.

-Ha ha!

OK. -Hi.

Shane, voice-over: Harriet the Horrible and her furry co-workers are livestock guardian dogs, and defending sheep from predators is their full-time job.

Cat: You know, we're living in this natural environment and it's beautiful and everything, but it's a predator-rich environment, as well.

Shane: Mm-hmm.

I could not imagine that we could remain in the domestic sheep business without livestock guardian dogs.

-Really?

They're that essential?

-They are that essential.

Shane, voice-over: Despite the dogs, wolves still kill some of Cat's sheep, and she's lost more than one guard dog to wolves.

I understand that people think that wolves are majestic.

I do, too.

I think that they're amazingly powerful and intelligent predators.

But I think that we've got to have a way to keep this a shared landscape.

Shane, voice-over: The dogs do help humans, livestock, and wolves to coexist.

But these days, outside of a few National Parks, this "shared landscape" looks pretty bleak for wolves.

♪ Dan: Yellowstone's one of the few places in North America where they are not hunted or exploited on some level.

They go from being adored and watched through, you know, hundreds of people through spotting scopes to then moving across this imaginary line, and then people are watching through rifle scopes.

Shane: Yeah.

And last year was pretty devastating for Yellowstone wolves.

We lost about 20% of our population to human harvest, legal human harvest.

Shane: Whoa!

And you lose a key animal like the alpha male or female, the leader, that can cause a pack to fracture and dismantle.

-Mm-hmm.

-You know, we're disrupting families, we're disrupting rich legacies of relationships between individuals that's important to their behavior, to their ecology, and the subsequent effect on these landscapes.

Dan: Have you seen a Yellowstone wolf before?

-I have not.

-All right.

Well, you're about to.

Couple.

I see a black and a gray right there.

♪ Oh, my God.

♪ Of course, you know, they have full bellies, so they're probably going to be in a travel mode here for a little while, eventually they'll go and lay down and take a nap.

(howling) ♪ Dan: So you can see a wolf, and it's wonderful, but to hear a pack of wolves howl like we just did, it's like nothing-- Dude, my hair is literally standing on end right now.

That's crazy.

Dan: Exactly.

It is, it is.

You know, if we think we ourselves, as humans, can kind of supplant or replace that ecological force of predation, you know, I think we're fooling ourselves.

I don't think we, as the human predator, is sufficient to replace those natural dynamics of a predator.

It's a job that's too big for us.

It's a job that's too big for us.

And we should leave it to the professionals.

Leave it to the professionals or be willing to share that professional stage with them.

It comes back to us.

Are we willing to allow a place for the wolves among us?

Shane, voice-over: For generations, the answer to Dan's question was no.

We were afraid, and we didn't want to share.

It reminded me of something Carter told me.

We're very self-centered, very greedy, so we are willing to, quote, "live with something as long as it don't bother me."

Shane, voice-over: And it's true that wolves aren't always the easiest neighbors to live with.

Dan: It's one thing to be in an urban area and say, "I want wolves in, you know, Montana out in the mountains," but never visit there, never be there, never have to live with them, never have to worry about, "Are they gonna kill my sheep or my cattle in the night?"

Shane: Yeah.

Shane, voice-over: But making space for wolves might be worth it, in spite of the challenges.

Here in Yellowstone, we're finding out just how important wild predators are.

Humans are really good at killing, but that doesn't mean other predators are obsolete.

Choir: ♪ Glory... ♪ Shane, voice-over: As a species, humans are still growing into our role on this planet.

We've always hunted to survive, but it's not our basic needs that drive hunting to extremes.

When killing brings us prestige, power, or profit, we can devastate animal populations, reshape entire ecosystems, and alter the evolutionary fates of our prey.

We don't need to abandon our hunting roots, and I don't think we should.

Hunting connects us to the world and to a part of ourselves, but we're not like other predators.

We know what we're capable of.

Armed with that knowledge, I hope we can channel our killer instincts more thoughtfully, leave room for wild hunters, and maybe give new meaning to the title of "Top Predator."

(cocks gun) (auto-tuned choir vocalizing) ♪ ♪ Human Footprint is available with PBS Passport and on Amazon Prime Video.

♪