♪♪ BUCHANAN: My name is Gordon Buchanan.

As a cameraman, I've filmed wildlife all over the planet, but there are limits to where I can go.

She's returning to the place that I can't follow her.

So in this series, it's the animals that are doing the filming, to reveal the secret side of their lives we've never seen before.

-Oh, that's so cool.

-That is lovely.

BUCHANAN: Over the years, we've designed pioneering mini cameras for a huge range of animals.

It's like a job interview.

Everything is made to measure.

Just figuring out what her new bit of bling is.

And we've teamed up with scientists who want to learn about the challenges animals face to help protect them in the future.

JOHNSON: She is potentially showing us parts of the ocean that no one has seen before.

BUCHANAN: In this special episode, we dive into the ocean to find out... What do turtles get up to at sea?

Can sharks help protect coral reefs?

How do gannets find their food?

And how do seal pups survive after being abandoned by their mother?

This is "Animals with Cameras."

♪♪ ♪♪ BUCHANAN: My first adventure starts here -- Cape Verde -- a cluster of tropical islands off the west coast of Africa.

I'm on Sal, one of the driest and most barren.

This really is a true desert island.

First impressions as a wildlife cameraman, looking around -- there aren't that many wild animals.

But for just a few months each summer, the sandy beaches in the south, where I'm heading, are inundated by a very, very special reptile -- the loggerhead turtle.

♪♪ Loggerheads can weigh twice as much as an adult human and live for up to 50 years.

They spend their lives traversing the world's oceans all on their own, traveling thousands of miles between feeding grounds.

Because they spend so much time in the open ocean, extremely little is known about them.

So what do these creatures do at sea?

Hopefully the cameras will find out.

Biologists Albert Taxonera and Christophe Eizaguirre have been studying the loggerheads on Sal for the past decade.

TAXONERA: What we are trying to do is to learn more about the conservation status of these animals, learn more about them so we can actually protect them better.

BUCHANAN: Cape Verde hosts one of the world's largest populations of nesting loggerheads.

During the breeding season, up to 7,000 females return to Sal's beaches where they were born.

Each can lay up to 6 clutches of 80 eggs.

It's widely believed that during their nesting season, loggerheads will not feed for five months.

But is this actually true?

Do turtles feed in the surrounding ocean or not?

Albert and Christophe need to use the mini cameras to find out.

EIZAGUIRRE: I've been working in Cape Verde for 10 years, and for almost as long as this time, we had the speculation that turtles feed locally.

BUCHANAN: So why is it important to know if they're feeding?

The beaches of Sal are already protected to safeguard the turtles, but the surrounding coral reefs are not.

So, if the turtles are feeding here, the marine ecosystem needs protecting, too.

TAXONERA: If we understand what they do, we can always push for better conservation strategies.

BUCHANAN: But to safeguard the waters, first they need evidence, something I hope the cameras can help with.

This morning, I'm heading a few miles offshore with Albert to a reef location where he suspects the turtles could be feeding.

Seeing the turtles on the beaches, and you've got this opportunity to be very close to them to study them intimately, but then they get into the water and they are gone.

TAXONERA: This is true, 'cause we see the data, we study a very small, tiny portion of their life.

That's when they come to lay the eggs, but we don't know what's going on in the ocean.

I think that the footage from the cameras will help us improve much more our knowledge.

BUCHANAN: It's a free dive of 30 feet to reach the bottom.

And within seconds, we get our first glimpse of a turtle, swimming into the blue.

♪♪ And just a few feet away, another resting on the seabed.

Amongst the shoals of fish, these rocky outcrops are the perfect environment for crustaceans and seaweed, which loggerheads are known to feed on elsewhere.

It's a brief dive, but it gives me a tantalizing insight into the turtles' world.

But even if I had a scuba tank, I couldn't follow them for long enough to answer Albert's questions.

So I'm hoping the cameras can.

We just need a suitable loggerhead to join the team.

As night falls, the turtles begin to arrive on the beaches.

It's Albert and Christophe's opportunity to survey the nesting females.

And I'm joining them to find one for our all-important camera deployment.

So how many turtles do you think are on the beach?

TAXONERA: Right now?

BUCHANAN: Yeah.

TAXONERA: Every night, we are counting around 100 nests.

BUCHANAN: Wow.

TAXONERA: Around, so that's 100 turtles.

BUCHANAN: So we should trip over one fairly soon.

TAXONERA: Definitely.

I show you.

We can see one from here already.

BUCHANAN: Shall we go and have a look?

Albert makes a quiet approach, so not to disturb this female.

We're looking for a turtle that's big enough to carry the camera with ease.

♪♪ TAXONERA: She looks big.

She's around 80, 81, 80 centimeters long.

BUCHANAN: That's big enough for us.

We've found our new crew member.

And this is the camera she'll be wearing.

This is the camera end.

We've got a high-definition camera that's tilting forward and down that's going to give us that over-the-shoulder view -- a turtle's eye view.

And we've got attachment points here.

After a day at sea, this magnesium swivels, it dissolves in salt water, and that's when the camera floats back up to the surface.

Once the turtle has finished laying her precious eggs, Albert and Christophe work swiftly and silently to collect valuable data for their ongoing research.

Then they place a temporary box around her to keep her safe.

This is an exciting moment for me, because this female is soon to go from just being one of the many thousands of turtles that visit these nests to becoming a member of our film crew.

Her shell, or carapace, is given a clean, and the camera is attached using an environmentally friendly resin.

Once the camera anchors have eroded away, this too will be shed over the coming days.

Just over an hour after she first heaved herself onto the beach, our turtle is reunited with the ocean.

Here she comes.

Now it's over to her to film her secret world, but only if all of this technology works.

Fingers crossed we'll get our camera back in 24 hours' time.

More than 80% of the ocean is unmapped and unexplored.

Even the lives of the most notorious marine animals harbor secrets.

You might think we know all there is to know about sharks.

But as they live at sea and can swim at high speeds, they're incredibly tricky to study.

So our understanding of their lives is actually quite limited.

But onboard cameras can help change that.

Scientist Dr. Tristan Guttridge has been studying sharks in the Bahamas for the past 15 years.

GUTTRIDGE: I have been literally obsessed with sharks since I can remember, and it's just grown and grown and grown and I'm now a 38-year-old marine scientist that still has that little-kid passion to work with sharks and to learn more about them and to try and hopefully conserve them and protect them.

BUCHANAN: Tristan has come to the island of Andros, home to one of the largest coral reefs in the world, measuring over 130 miles long.

It's a magnet for several species of shark who rely on it for food and shelter.

Reef sharks, lemon sharks, and great hammerheads patrol the area.

Even one of the biggest predators in the ocean, the tiger shark, lives here.

Around the world, coral reefs are dying at unprecedented rates due to pollution and climate change.

Tristan needs to check the health of the Andros reef to ascertain if these sharks will have a home in the future.

Doing this with a team of scuba divers would be an enormous task that could damage the coral.

So the best guides to this vital underwater habitat are the sharks themselves.

GUTTRIDGE: As a human, I can only spend about an hour underwater and I'm limited to certain depths as well.

But a reef shark -- it can act as essentially a surveyor for many, many hours.

And so we can actually look at the health of the system that it's swimming in and patrolling.

BUCHANAN: Tristan wants to enlist the help of Caribbean reef sharks.

They spend most of their time around the coral, making them perfect to carry the cameras.

Tristan is tagging sharks as part of his ongoing research, so this is a good opportunity to add the onboard technology.

He's helped by shark expert Grant Johnson.

And to catch the sharks, they're using a simple float system.

GUTTRIDGE: The beauty of these things is that if the float starts moving up and down, then you know you've caught a shark.

So we can actually get to that animal really quickly, so it's a very effective way and safe way of fishing for these animals because we can bring the shark to the side of the boat, work it up, measure it, place our camera tag in a short period of time.

BUCHANAN: And within minutes, they're in luck.

GUTTRIDGE: We've got something already.

JOHNSON: We got a shark.

GUTTRIDGE: Yeah, we've got something moving already.

Look at that.

Five minutes, and we've already got something hit a bait.

This place is just littered with sharks.

BUCHANAN: How much the float moves is an indication of how big the shark is.

JOHNSON: Look at the buoy, man.

The buoy is getting pulled down.

GUTTRIDGE: That is not small that's towing that around.

That is definitely not small.

JOHNSON: I'm saying bull.

GUTTRIDGE: You're going bull?

JOHNSON: I'm predicting -- Look at that!

GUTTRIDGE: I mean, if it is a bull... JOHNSON: Look at that.

GUTTRIDGE: Holy á*á*á*á* JOHNSON: Look at that.

JOHNSON: Oh, my God, dude.

GUTTRIDGE: That is a 3-meter tiger shark.

Okay.

BUCHANAN: Tiger sharks are at the very top of the food chain.

They'll even eat other sharks.

But its own safety is top priority, so the team works carefully.

JOHNSON: We got her, we got her.

BUCHANAN: It's incredibly rare to catch this species, and Tristan wants to make the most of it.

Like reef sharks, tiger sharks use coral habitats, but they explore other environments, too.

So, if we can attach a camera, we can analyze the wider ecosystem through the eyes of one of the world's greatest predators.

The onboard system has been designed with the anatomy of the shark in mind and it can operate down to 1,600 hundred feet, film in HD, and it can even record depth and temperature.

With everything safely attached, it's time for this incredible predator to capture its underwater world.

♪♪ JOHNSON: Away she goes.

GUTTRIDGE: Away she goes.

JOHNSON: Unbelievable.

GUTTRIDGE: Wow!

Good work.

How's your back?

JOHNSON: Totally fine.

Totally fine.

GUTTRIDGE: I was not expecting that.

This is becoming very interesting indeed.

Wow.

BUCHANAN: Five hours later, the camera automatically comes off, but finding it in the open ocean is a tricky task, so Tristan is relying on more technology.

GUTTRIDGE: Another 20 seconds.

BUCHANAN: The camera is equipped with a satellite beacon, which Tristan can detect on this handheld device.

GUTTRIDGE: That satellite tag is emitting its code every 90 seconds, and I'm getting a bearing on where it actually is.

Another 15 seconds, and we should be good.

You can see the water is much clearer here, so hopefully the tiger shark got us some good... [ Beeping ] Oh, oh.

Oh, yeah.

This way, slightly this way.

BUCHANAN: Suddenly, a flash of orange stands out against the blue.

GUTTRIDGE: How did I know Grant would spot it?

Camera still on it?

JOHNSON: Yeah.

GUTTRIDGE: The LED's still on!

Disco, disco!

I'm very happy.

The tag's intact.

No evidence of rubbing or anything.

The satellite tag worked perfectly.

Let's hope there's some magic in here.

JOHNSON: It's gonna be amazing to see what's on that, dude.

It just went down to the bottom of the ocean.

GUTTRIDGE: I know, I know.

I'm very excited.

BUCHANAN: It's a brilliant success.

And back on dry land, Tristan and Grant take a look at the footage.

GUTTRIDGE: She's moving quick.

JOHNSON: Oh, you see some little... What is it, little coral heads or sargassum that she's starting to pass through?

There's the wall, there's the drop-off.

GUTTRIDGE: Yeah.

She gonna go down it?

JOHNSON: She's just going off the edge.

BUCHANAN: This reef wall is the edge of a deep-sea basin known as the tongue of the ocean.

And this tiger shark heads straight to the bottom.

From the depth gage built into the camera, we know that it's 520 feet deep.

That's more than 5 times deeper than the average scuba diver is allowed to go.

So this shark is potentially showing us parts of the ocean that no one has ever seen before.

This footage has helped Tristan see what the shark sees.

And he thinks it may have dived deep to search for the prey in the water above.

GUTTRIDGE: To me, it makes sense.

If you're a, you know, a fast-moving, ambush kind of predator, you go along the bed like that and then you can launch an attack without being detected.

JOHNSON: Right.

BUCHANAN: An in-built thermometer also shows it's 9 degrees Fahrenheit colder down here than at the surface.

GUTTRIDGE: My suspicion is that they're making these excursions onto the flats to hunt for turtles, stingrays, smaller coastal sharks and then going back into the deeper water to recover.

BUCHANAN: This cold, deep water helps the shark cool off after hunting on the warm, shallow sand flats, letting it stay in peak performance mode.

Critical for an apex predator like this.

It's a promising start, but Tristan still needs to deploy the camera on one of the most important species in the ecosystem -- Caribbean reef sharks.

He hopes they'll take us close to the coral, letting us see how healthy the local reef is.

And it doesn't take long to find one.

JOHNSON: Oh, boy.

GUTTRIDGE: Perfect size once again.

BUCHANAN: Every shark that Tristan catches is measured and tagged as part of his long-term study to understand the abundance and distribution of sharks in the area.

GUTTRIDGE: And 189.

We try and be as gentle as we can.

We're also trying to do this as quickly as possible so we can get that shark off and swimming.

BUCHANAN: The camera mount has soft pads on the inside of the clamp, which gently hold it in place.

♪♪ ♪♪ Over the next few days, Tristan and Grant manage to deploy four more shark cameras along different sections of the reef to help get a good overview of the area.

GUTTRIDGE: Perfect.

Alright, I think we're ready to release.

♪♪ BUCHANAN: In total, the sharks have captured almost 25 hours of onboard footage, giving us a much more detailed look at their world than any diver could achieve.

GUTTRIDGE: This is pretty cool.

JOHNSON: Look at that, look at that.

GUTTRIDGE: Oh, big 'cuda.

JOHNSON: Oh, big barracuda.

GUTTRIDGE: I love being able to see what they're seeing.

BUCHANAN: But what the sharks have filmed is worrying.

There's a layer of algae covering much of the reef.

Too much algae can reduce the oxygen levels and block the sunlight, killing the coral, which then has a negative effect on everything in the food chain, from wrasse to reef sharks.

GUTTRIDGE: There's a lot of fishermen here, so they could be putting a lot of pressure on some of those reef fishes that would be normally eating the algae and then maintaining the health of the system.

You've got, obviously, pollution as well and then on top of that, global warming.

BUCHANAN: Overfishing, pollution, and climate change could all contribute to this thick algae.

They're global issues and will only get better if we continue to reduce our impact on the natural world.

The cameras have provided a great insight into the health of some of the most remote corners of this reef.

But they've also revealed some surprising shark behavior.

GUTTRIDGE: Oh, this is cool.

JOHNSON: Look at that.

Tight little tunnel.

GUTTRIDGE: Don't tell me it's gonna go through there.

JOHNSON: Wow!

That's amazing.

GUTTRIDGE: Right under the cave, through the archway.

JOHNSON: That's really amazing.

GUTTRIDGE: I mean, I don't know about you, but I've never really seen one swimming this deep into the reef, like down these little gullies.

JOHNSON: Makes you wonder if he's looking for food.

GUTTRIDGE: That could be a strategy, I guess.

Stay close to the floor, search around the reef structure and basically ambush a reef fish.

It can't be easy hunting reef fish on the reef.

There are so many hiding places.

BUCHANAN: Reef sharks can sniff out prey or use special electroreceptors to detect the heartbeat of their next meal.

But it's hard to catch a fish before it escapes into the reef.

So, by weaving through the coral, there's a chance this shark can sneak up on its next victim.

It might also keep them hidden from bigger predators like tiger sharks who, as we know, patrol this area.

Seeing this behavior is something that only onboard cameras could reveal.

As soon as a diver enters the water, the sharks behave differently.

And there's no way a human could keep up through these tight coral corridors.

GUTTRIDGE: Oh.

JOHNSON: Whoa.

GUTTRIDGE: Oh, that's when the tag came off.

JOHNSON: No matter how much scuba-diving you do, you're never gonna be able to spend that much time with a shark.

GUTTRIDGE: Exactly, and that's the big difference.

That's the thing that these tags do for us is we get five hours of uninterrupted footage of where these animals are going and how they're using the habitat.

BUCHANAN: The cameras have been a success, showing us that these sharks can hunt among the coral in ways Tristan had never seen before.

And the footage proves that this reef needs further protection from the global impact of mankind if it's to remain a shark mecca.

♪♪ Back in the Atlantic Ocean, on the island of Sal, our turtle-cam has been deployed for 24 hours.

Biologists Albert and Christophe need to find out if the loggerheads feed here during the nesting season.

If we can film this behavior, it will prove that this marine ecosystem is vital for the turtles and needs protecting.

But first we have to get the camera back.

It's 7:00 in the morning.

We've just had a ping from the GPS on the turtle's camera, so it must have come off and floated up to the surface.

We're heading out on a boat and hopefully we can find it.

We can only get a satellite location every few hours, so it's a race to find the camera before the current carries it off course.

To help us, we're also using a VHF radio antenna.

But sometimes our own eyesight is better than the latest technology.

♪♪ ♪♪ [ Indistinct conversations ] [ Cheering ] I cannot believe that.

Our keen-eyed skipper spotted it.

♪♪ Amazing.

It's still largely intact.

It's quite something that this has spent 24 hours on the back of a loggerhead turtle.

But will our footage provide the insight that Albert and Christophe have been waiting for?

Will it show her feeding in local waters?

Time to take a look with Albert and Christophe back at the lab.

So this really is the big moment, all of those long nights on the beach deploying these cameras and we've got the footage here that we are gonna see for the very first time.

EIZAGUIRRE: Tell me about it!

Just press play, let's go!

BUCHANAN: Okay, here we go.

♪♪ EIZAGUIRRE: Nice.

BUCHANAN: Wow!

The view from the camera is crystal clear, and straightaway, our turtle rewrites a common scientific theory.

Female loggerheads were thought to be solitary during the nesting season.

But this footage proves they do interact with one another, far more than was ever expected.

And there's another surprise discovery when this turtle encounters a sunken anchor.

♪♪ EIZAGUIRRE: Oh, my God!

BUCHANAN: What's she doing, is she feeding?

EIZAGUIRRE: She is.

BUCHANAN: Wow, she is.

EIZAGUIRRE: She is feeding on the seaweed on the anchor.

EIZAGUIRRE: That's unbelievable.

And one of the really, really interesting elements is that it's so soon after the nesting.

I certainly did not expect that.

TAXONERA: It's the first time ever that we've seen this behavior.

BUCHANAN: Exquisite.

This turtle's gonna put me out of a job.

Put every underwater camera person out of a job.

This is the evidence we were looking for.

It proves that these turtles do feed during their 5-month breeding season, so this marine ecosystem needs more protection.

And that can't come soon enough, based on what she films next.

It's a discarded fishing net that's smothering a large part of the reef.

The turtle is clearly trying to feed through the net, but if she accidentally swallows it, it could have a negative effect on her health.

It's a stark reminder of why these waters need safeguarding.

Thankfully our turtle swims off and out into deeper waters.

And she feeds again, this time on a jelly-like sea-squirt.

I mean, this is sort of foraging, sort of constantly grazing that she's doing here.

EIZAGUIRRE: You can see, like, pieces floating around, so she is definitely feeding on that.

BUCHANAN: Feeding in this way, is that enough sort of food for her in a day, if she is constantly just browsing her way through the ocean?

EIZAGUIRRE: I want to say no.

As you know and you've seen... nesting is really, really energy-consuming.

So I believe they top up their reserves right now.

BUCHANAN: Dive and feed complete, she heads towards the surface for a breath.

But before she gets there, she encounters another turtle, and this one is covered in barnacles and seaweed -- an indication that it's very old.

It's amazing to see so much life growing on that turtle but also following the turtle around, this sort of moving ecosystem.

EIZAGUIRRE: Totally.

When you actually protect the turtle, you also protect all the ecosystem around them, the fish, the entire habitat.

You see, if we did not have the camera but only a tagging device like a GPS system, we would never know that that turtle spends so much time at the surface with another turtle.

BUCHANAN: Yeah.

So does this, in some way, rewrite the science books on what we know about these animals?

EIZAGUIRRE: It certainly rewrites my knowledge.

BUCHANAN: From what we've learned from this turtle, can that be used to help protect different turtle populations around the world?

TAXONERA: Showing this footage, these behaviors is beautiful, Like, it will help people understand why we need to protect them, why we need to stop polluting our oceans, why we need to stop overfishing.

EIZAGUIRRE: The Cape Verde aggregation is probably the second largest aggregation in the world.

If we lose this aggregation, the entire species is in true danger of extinction.

BUCHANAN: This turtle's footage brings new insight into the loggerheads' hidden world, revealing that they're more social than we ever imagined and that they do feed during the nesting season -- a world first for science.

And it's the proof that Albert and Christophe needed to push for greater protection of these vital waters.

And I hope it safeguards the future of this beautiful species on Cape Verde for many years to come.

It's not only animals that live beneath the waves that have a hidden side to their lives.

I'm about to meet some animals who will take the mini cameras on land, in water, and up in the air to solve some mysteries.

♪♪ Gannets!

They're one of the most aerobatic seabirds in the world, renowned for their spectacular high dives.

They can drop like an arrow from over 100 feet up and strike the water at 50 miles per hour.

These feathered torpedoes can plunge 65 feet underwater, where they can pick off their meal.

To protect themselves during these legendary stunts, they're equipped with extremely strong neck muscles and a spongy plate of bone at the front of their skull to cushion the impact.

They're famous for their incredible hunting skills, but how do they find small shoals of fish hidden underwater in the wide-open ocean?

I can stand on a gannet colony like this and with a big, long lens get quite intimate views, but that's just half the story really.

Given that gannets can fly up to 250 miles away from their nest, it would be impossible for me to follow an individual to find out exactly what it's doing that far away.

So, this is a job for the mini-camera technology.

I would say that we are pretty much guaranteed to get some dramatic footage from an onboard camera.

And when they're not flying around dramatic clifftop colonies like this, they're soaring over or plunging into the ocean.

In Ireland, Dr. Mark Jessopp is trying to unravel some of the gannet's mysteries.

JESSOPP: For a number of years, we've been able to put GPS tracking devices on birds and that effectively tells us where animals are going when they're out at sea and where they go to forage, but we're still not sure how they forage or what the cues are that they might use to say "There's food here."

BUCHANAN: In 60 years, seabird populations in general, including puffins, have declined by 70%, but not gannets.

They are thriving.

Mark wants to use onboard cameras to see how gannets find their food, because he thinks that's what makes them so successful.

JESSOPP: Gannets are a really fascinating species.

You know, they're one of those species that have bucked the trend of global seabird declines, and gannets tend to be increasing in populations, so we really want to understand how and why they're doing it.

One of the theories is that they're getting supplemental food from humans through fisheries discards.

Ideally I'd love to see something like fishing vessels, perhaps other animals, you know, pie in the sky, maybe we'll see some dolphins and feeding associations with dolphins.

You know, the sky's the limit here really.

BUCHANAN: If Mark can discover how gannets find their food, he can work out how to help other seabirds that are in decline.

So, we need a camera that's waterproof and lightweight yet strong enough to withstand a big impact.

It's one of the hardest challenges we've ever faced.

Tackling the task is tech wizard Chris Watts.

He's built cutting-edge cameras for an incredible variety of animals.

And he's spent three months developing a bespoke gannet camera.

WATTS: So this has been our solution.

It can record in HD.

It can do slow motion.

We've also fitted it with the widest angle lens we can, and we're hoping that we can get it on the back of the bird sort of base of the tail, which means we're just not gonna miss any action.

It's coming in at...60 grams, which is pretty much perfect.

BUCHANAN: That's 2% of the gannet's body weight, easily light enough for them to fly with and the battery should last for almost two hours.

Packing this much technology into such a small space is an incredible achievement.

But can it deal with the impact of hitting the water at high speed?

When gannets strike the surface of the sea, they experience almost 9G as they decelerate, which is more than most fighter pilots can contend with.

To see if the camera can withstand such high forces, Chris is going to some extreme measures to put them to the test.

♪♪ WATTS: Today this is the moment of truth really.

If it's not waterproof and it can't take the impact of hitting the water, then it's all for nothing.

BUCHANAN: To simulate a gannet's dive, Chris is strapping the camera to an arrow, ready to be fired out to sea.

WATTS: So there we have it -- the camera arrow.

It seems slightly a crazy way of testing a camera, but I can't think of a better way.

♪♪ ♪♪ BUCHANAN: A fishing reel brings it back to shore for inspection.

♪♪ WATTS: So does it look like it survived?

MAN: Nothing in the front port, so... Yeah, good.

BUCHANAN: A triumph.

Even after repeated trials, the camera remains intact.

Now it's time for the real thing.

♪♪ 3 miles out in the Irish sea, Mark and his team are heading to the remote Saltee Islands -- home to over 7,000 breeding gannets.

The onboard camera will only record for two hours, so the team needs to recruit a gannet that's just about to go fishing.

JESSOPP: Birds can sit here at the nest for three or four days, and the batteries will only last so long.

And so we want to make sure we're getting a bird just as it's about to leave.

BUCHANAN: The parents work in shifts.

While one guards the chick, the other goes foraging for up to four days.

They then swap over, and that's the moment Mark is looking for.

MAN #2: Over there, we've just had one come in, Mark.

Do you want...

The one on the left has just fed the chick.

JESSOPP: So we want the one on the right?

MAN #2: Yes.

JESSOPP: Okay, let's get him.

MAN #2: Excellent.

BUCHANAN: Mark's research project means he has special permission to catch these adults.

JESSOPP: Ready?

MAN #2: Yup.

BUCHANAN: The chick is safe with the other parent.

And when our bird is bagged, it relaxes and Mark can do a few essential health checks.

JESSOPP: And that's 3 kilos exactly.

BUCHANAN: This one is in top condition, a perfect candidate for carrying the camera.

JESSOPP: So we attach it to the central tail feathers, and that means it is far enough away from where the head goes hitting into the water at high speed.

So the tags don't get ripped off by that hydrodynamic drag.

BUCHANAN: This tape should hold the camera in place, but it's soft enough that the bird could rip it off if it's not comfortable.

Which means there's a very real risk these cameras won't come back at all.

MAN #2: You have it?

JESSOPP: Yup.

BUCHANAN: With everything in place, it's time for this bird to reveal its secret life at sea.

♪♪ JESSOPP: Flying away quite nice and strong.

MAN #2: Seems to be very happy.

JESSOPP: Going off, hopefully on a nice foraging trip for us as well.

MAN #2: Shall we go and get another?

JESSOPP: I think we should.

MAN #2: Everything is switched on.

♪♪ ♪♪ BUCHANAN: And after just 24 hours, the first gannet returns with the camera intact.

JESSOPP: Over the chick and around the bird.

Go!

♪♪ Really looking forward to seeing what's on the camera.

We have no idea.

He's had a very successful foraging trip, I think.

He feels very heavy.

Oh, you fatty.

BUCHANAN: This gannet has put on 14 ounces since it was caught yesterday.

So Mark knows it's been fishing.

We just hope that the camera was running at the right time.

JESSOPP: I'd love to know what prompted that dive.

You know, what did it see that says, "This is where I need to dive to successfully get food"?

BUCHANAN: The bird is given a careful health check and released back into the wild.

♪♪ Then the team can take a look at the first batch of footage.

What immediately surprises them is just how close to the water the gannets seem to fly.

-Oh, look at that.

-Oh, wow.

JESSOPP: This is great for people who've been doing a lot of work looking at things like gannets' vulnerability to wind farms.

And obviously, when they're flying that low, they're well outside of the sweep area of any turbine.

So you would say there would be very little risk of collision.

BUCHANAN: And to their delight, the team have captured some diving behavior.

JESSOPP: Oh, plunge dives.

Head.

Oh!

-My goodness me.

-That is so cool MAN #2: That is lovely.

I have always wanted to see that.

JESSOPP: Yup, the trip was worth it for that one alone.

BUCHANAN: It's a brilliant start, but because the action happens so fast, it's hard to see how the gannets are finding their food.

So the team sets out to get more onboard footage, but this time the cameras are set to record in slow motion.

So this time, we should see precisely how they're finding the fish.

♪♪ In total, seven gannets take the cameras out to sea and return them safely back to the colony.

And after carefully analyzing the footage, Mark can see exactly how the gannets are finding their food.

JESSOPP: So we're looking at one of my favorite sequences here.

It's one where, all of a sudden, we start seeing common dolphins up at the surface.

And within seconds, the gannets are going straight towards those dolphins and diving.

It's really exciting to see them, and I never thought we'd get footage that was of a resolution that we could identify the species, and, you know, they're quite clearly common dolphins.

BUCHANAN: Underwater, the camera's in-built microphone has even recorded their calls.

[ Dolphins squeaking ] Mark believes the birds are using the dolphins to help find their food.

And he's found evidence that they're following other marine animals, too.

JESSOPP: We had to go through essentially frame by frame here to see this, but you can quite clearly see two whales, at least whale blows, and we see that the gannet is immediately turning towards those.

And easily within 15 to 16 seconds, that gannet is now diving right where those whales were at the surface, so it's indicating that those gannets are perhaps using the whales themselves there as a visual cue to say, "This is where other predators are.

Therefore this is probably where there's food."

Fantastic to see these odd bits of behavior that we would have ordinarily missed.

BUCHANAN: The footage shows that gannets are using other species to effectively find small patches of food in a large, open habitat.

And this has big implications for how we conserve them.

JESSOPP: If we want to preserve gannets, we need to preserve the visual cues that they're using, which means protecting our dolphin populations.

It means protecting our whale populations.

All of these populations are interconnected, so we need to take an ecosystems approach to our conservation objectives.

BUCHANAN: In general, seabird populations are declining, partly because of a drop in fish stocks, but gannets don't seem to be affected, and the footage shows why.

JESSOPP: So there's this wonderful sequence where we can see, just out on the horizon, a fishing vessel, and the gannet pretty much instantly starts to orient towards and fly towards that fishing vessel.

There must be at least 100 other gannets around the fishing vessel here, which might indicate that gannets have learned to use fishing vessels as a foraging cue or as a cue that there is food to be had here.

BUCHANAN: Importantly, there are very few other seabird species capitalizing on this free meal.

JESSOPP: It's almost exclusively gannets around here, and they're quite an aggressive species, so they're managing to successfully outcompete other sea birds for that fisheries resource.

BUCHANAN: By exploiting fishing vessels, they get access to a steady supply of food even when their prey is in decline.

The onboard cameras have been a success.

They've shown us how these birds use other animals and even fishermen to find their next meal.

The oceans support some truly gigantic animals.

And the next mission is on the coast of California in Año Nuevo State Park, where giants come ashore to breed.

These are northern elephant seals.

The bulls can reach 13 feet long and weigh over 2 1/2 tons.

They battle to become beach master.

Despite their blubbery appearance, these animals are extreme athletes.

They swim 5,500 miles a year and can dive 1 mile deep, drop their heart rate to just three beats per minute, and can hold their breath for two hours.

Every winter, this area becomes a huge crèche, filled with over 2,000 females, each giving birth to a single, precious pup.

[ Screeching ] But after just four weeks, the mums head out to sea and abandon their young forever.

Scientists Roxanne Beltran and Patrick Robinson know a huge amount about the lives of the adults, but very little is understood about the pups and they want to find out more.

BELTRAN: The moms actually leave before the pups ever go into the water, so these juveniles, when they become independent from their moms, are trying to figure out how to be seals.

BUCHANAN: They live off their fat reserves from their mother's milk for the next two months before they head out to sea and fend for themselves.

During this time, they train for adult life, much of which is done underwater, where they can swim faster and further than we can, making it hard to study them.

BELTRAN: When they're in the water, as soon as they dip below the surface, we can't actually see what they're doing.

And so there's been this huge gap in our knowledge of what these seals are actually doing in the two months before they leave for that trip to sea.

BUCHANAN: With any luck, the onboard cameras will show what these pups are doing to prepare themselves for adult life.

Roxanne and Patrick find four young seals to carry the cameras.

Although the pups are only a few weeks old, they're already enormous.

They put on 200 pounds in their first month, fueled by milk which is 55% fat.

That's more than whipping cream.

After a few health checks, the specially designed onboard cameras are attached with a temporary, non-toxic glue.

BELTRAN: During the procedure, we're monitoring everything from heart rate to respiration rate.

We're making sure that everything is going appropriately with the seal.

ROBINSON: I've spent the past 15 years studying the adult animals, and we know so much about what the adult females do when they're out at sea and we don't know very much about what the young ones are doing right here next to the colony, so this is an amazing opportunity for us.

BUCHANAN: The cameras will record for 16 hours and have been designed to withstand the crushing pressure of deep water.

Once they've returned safely, Roxanne and Patrick are able to analyze the footage.

BELTRAN: Oh, wow.

What is she doing?

ROBINSON: They're more graceful than I thought, based on how they are on land.

BUCHANAN: Swimming with the seals gives Roxanne and Patrick an entirely new perspective.

And the footage provides a real revelation about how social the pups are.

ROBINSON: I'm surprised by how active and interactive they are.

BELTRAN: Yeah, I think when adult elephant seals go out to sea, they don't interact at all, right?

That's what we think at least.

ROBINSON: I don't think there is any evidence for that.

BELTRAN: Right, they're completely solitary at sea, so the fact that these guys are interacting in the water is weird.

I wonder if they are just learning from each other.

ROBINSON: I guess because they get no parental instruction, this is helpful for them in their development.

BUCHANAN: In all of the footage, the pups only ever swim in shallow water.

Roxanne and Patrick think that's because they're too fat to dive deep.

Despite being so heavy, all of their blubber makes them really buoyant.

BELTRAN: Without doing anything, she automatically floats to the surface.

I think that's why she's working really hard to stay down to explore the bottom of the ocean.

It may be why she's interacting with other seals.

I don't know if they're sort of helping pin each other down or what they are doing.

ROBINSON: They need the fat in order to survive a long period of time while they're learning how to forage, but it's actually bad for them because if they are too buoyant, it's difficult to forage, so... BELTRAN: It's a trade-off.

ROBINSON: It's a trade-off, yeah.

BUCHANAN: Swimming around these shallows, the pups seem to investigate anything they come across, even bits of rubbish.

ROBINSON: Is that a plastic bag?

BELTRAN: Plastic?

BUCHANAN: It's unlikely to mistake this plastic bag for food.

But they have been known to get tangled up in waste and this playfulness could explain how that happens.

The cameras also reveal that these mischievous pups often chase the local fish.

They're not catching them, but it's all good practice.

And it's not just the fish they're toying with.

Surprisingly, they spend a lot of time playing with seaweed.

BELTRAN: What is she doing?

ROBINSON: Did she grab it?

BELTRAN: Yeah.

ROBINSON: Yeah.

BELTRAN: She was dragging it around.

What?

BUCHANAN: Playful practice is important in the development of many young animals.

For these seals, it may help build those important diving skills which later they'll rely on.

♪♪ After their in-water training, it looks like they come out for a rest on the beach, but the scientists have a very different theory.

It's hard to see to the untrained eye, but the seals seem to be holding their breath.

BELTRAN: It doesn't look like they're doing much here, but I think what they are actually doing is figuring out how to become breathless divers so that they can find food during their first trip to sea.

ROBINSON: Developing their physiology.

BELTRAN: Yeah, exactly.

I mean, you can see that seal holding its breath.

And it will probably hold its breath for a long time.

I wonder if just like we would train for a marathon by doing little runs, they're doing little breath holds to basically figure out how they can get down to food on breath hold.

BUCHANAN: This seal holds its breath for almost 12 minutes.

So it's got some practice to do before it can manage two hours like the adults.

By filming themselves, these pups have shown us how they prepare for life at sea.

After being left alone without a mother, they seem to train together.

Trying to hunt, exploring their environment, and practicing to hold their breath -- key skills that will make them elite ocean divers.

♪♪ BUCHANAN: Next time... we travel Down Under to solve the mysteries of some iconic Australian animals.

We discover the surprising nightlife of koalas... WOMAN: Oh, wow, look at that.

BUCHANAN: ...reveal how kangaroos are affected by urbanization.

WOMAN #2: We have got to make a decision, do we want to live alongside kangaroos?

BUCHANAN: And we create our most advanced camera yet to find out what's drawing thousands of flying foxes to a new life in the city.

MAN #3: [ Chuckles ] He's going over the road.

The "Animals with Cameras" adventure continues in Australia.

where some of the country's most iconic creatures take over filming.

MAN #4: Now the big test will be...what shots do we get?

The footage could hold vital information for scientists trying to safeguard these animals.

WOMAN #2: By getting video footage, we might be able to unravel this mystery and figure out what they're doing.

♪ ♪ ♪♪ ♪♪ ♪♪ To learn more about what you've seen on this Nature program, visit pbs.org.