01x03 - A Sharkwreck Mystery, Sea Cows, The Shark with the Long Tail

[bunniefuu]

Today, Jonathan investigates sharks that tilt when they swim!

Welcome to Jonathan Bird’s Blue World!

The underwater world is full of mysteries to be solved.

One such mystery involves the Great Hammerhead shark.

Divers rarely see Great Hammerheads…they are known for being shy loners, unwilling

to approach people.

But a few years ago, divers began visiting a place near Bimini Island in the Bahamas,

where Great Hammerheads have been caught by fishermen for years.

They found a special place with lots of sharks.

Over time, the sharks got used to divers and started coming in close for a snack, giving

people an intimate look at the Great Hammerhead shark.

I have been to Bimini several times and I am always amazed by how huge Great Hammerheads

are.

Not only does the head reach a meter or more wide, but the tall dorsal fin is a striking

feature of this unique and majestic shark.

And in spite of the aggressive appearance, Great Hammerheads almost never attack people.

They much prefer to eat stingrays in the sand.

But diving with Great Hammerheads has allowed divers to notice something unusual—the shark

often swims tilted to the side at an angle.

I also noticed this behavior in the Ocean Voyager Exhibit at the Georgia Aquarium.

My friend Andy Casagrande—one of Discover Channel’s primary Shark Week cinematographers—wanted

to help investigate the mystery of the leaning Hammerhead.

He attached a GoPro camera to the huge dorsal fin of a Great Hammerhead, to film the shark

for an extended period of time.

His amazing footage shed light on the behavior of these sharks…and it has to do with their

anatomy.

The hammerhead shark never stops swimming.

But, contrary to popular belief, many sharks do.

Most species of sharks, like the lemon shark, can rest on the bottom and move water over

their gills by simply gulping.

Biologists call it "Buccal Pumping.”

A few species of sharks, like the Whale shark and the White shark, are known as Obligate

Ram Ventilators.

They can only breathe by ramming oxygenated water into their gills through their mouths

as they swim.

If they stop swimming, they'll suffocate!

The Great Hammerhead is also an Obligate Ram Ventilator, and has to keep swimming.

Sharks such as the Blue shark keep swimming all the time too, but for a totally different

reason--because sharks sink if they stop swimming.

Fish, including sharks, are heavier than water, so they sink.

Bony fish have an organ called a swim bladder that they use to adjust their buoyancy.

By adjusting how much gas is in its swim bladder, a fish can keep itself perfectly neutral so

it doesn’t sink or float.

Since sharks have no swim bladder, they sink to the bottom when they stop swimming.

But some sharks like the Blue shark live in the open ocean where the bottom is thousands

of feet below where it’s dark and cold.

They can’t rest on the bottom.

So they have adapted to this environment by developing very large pectoral fins to act

as airplane wings.

As the shark cruises through the water, the fins provide lift to keep the shark aloft,

and prevent it from sinking into the dark, cold abyss.

The bigger the pectoral fins, the more lift they provide, and the slower the shark can

swim without sinking, which saves energy.

The Great Hammerhead on the other hand has small pectoral fins and a big head called

a cephalofoil.

The cephalofoil seems to accomplish several things for the shark, including expanded vision,

a larger surface area for electro-receptors, and additional front end lift like a mini-wing.

But it also has mass, and scientists think this mass, combined with small pectoral fins,

is the reason that hammerheads are so much more maneuverable than other similarly-sized

sharks.

But while those small pectoral fins help the shark turn quickly to catch prey, they have

a disadvantage: not much lift.

And this is where the tilted swimming comes in.

Andy Casagrande’s dorsal fin footage showed that when Great Hammerheads are on the move,

they are almost always swimming at a tilted angle of more than 45 degrees!

In 2015, Nicholas Payne, Gil Iosilevskii and 5 other researchers got together to investigate

this strange behavior.

They put sensors on Great Hammerhead sharks to measure the roll angles.

Then they used wind tunnel tests to model the effect and figured out what the sharks

are doing.

The sharks roll on their sides to use that huge dorsal fin as a wing and provide lift

while swimming distances.

It allows the shark to generate more lift, which means it can swim a bit slower without

sinking, and save energy.

In fact, swimming tilted to the side saves the shark about 8% swimming effort.

So when the shark needs to go somewhere, it tilts to the side and saves energy.

But when it needs to hunt, it swims straight up and down to take advantage of the increased

maneuverability.

The giant dorsal fin serves two purposes…a keel when upright, and a wing when tilted!

At this point, no other shark is known to use this technique, and it explains a mysterious

habit that divers observed in Great Hammerhead sharks.

Sometimes just being in the ocean creates new understanding of the life that lives there.

As divers, our time in the ocean is fleeting, lasting just an hour or so per dive.

But it affords us the opportunity to catch a glimpse of the lives of the animals that

live there.

This is one of the things that keeps me coming back over and over, for my short glimpses

into the Blue World.

Coming up, Jonathan travels to the Philippines in a search for the elusive Dugong!

Welcome to Jonathan Bird’s Blue World!

In the waters of Florida and the Caribbean, there exists a gentle marine mammal called

a manatee.

Because they often live inshore--close to people--and have enjoyed more than 40 years

of protection from hunting or harassment, manatees are often quite friendly.

Many of them have become acclimated to gentle interactions with people.

DUGONG But the manatee has a wild cousin, called

a Dugong, living far away, in the Indo-Pacific Ocean.

This animal is still hunted in much of its range.

It’s shy and hard to approach.

Wary of humans.

And exceptionally rare to see underwater.

Which is why I have come to the Philippines, one of a handful of places in the world, where

there are enough dugongs left to have a chance of seeing one in the wild!

I’m heading to Busuanga, in Palawan, Philippines, a remote and beautiful area where the endangered

dugong still roams wild.

But I didn’t come alone.

Award-winning IMAX filmmaking team Howard and Michele Hall have joined me on this trip.

They have been here before, and agreed to give me a hand with this daunting and challenging

assignment.

Our journey begins with a flight from the capital city of Manila down to Busuanga, then

a drive from the local airport to the water.

Next we take a ferry ride across the bay to our home-away-from-home, El Rio Y Mar Resort,

on the north side of Busuanga.

We arrive just after sunset in time for dinner.

The next morning, we awake to fog in the nearby hills, and our dive boat, a traditional Philippino

Bangka, ready to go.

We get our gear together and load the boat.

It’s going to be a long day.

Good morning!

In the experienced hands of captains Benny Martinez and Wilmar Bansilan, we set out on

our first day of adventure.

Dugongs are wild animals that roam the ocean freely, and it’s a big ocean.

But we know where they saw dugongs recently, so at least we know where to start looking.

Unfortunately that spot is two hours away!

Since it’s going to be a while, Howard and Michele do the only logical thing: take a

nap!

I’ve never been here before, so I spend some time watching the scenery go by.

I am always amazed by the natural beauty of the Philippines—lush, green hills surrounded

by beautiful warm water filled with untold species of animals to be discovered and filmed!

Eventually we make it to the area where some dugongs were last seen, and we start looking.

With experienced eyes, divemasters Omar Linsangan and Bryan Deramas begin scanning the surface

of the water.

Dugongs are solitary animals, so they are looking for just one.

It’s like finding a needle in a haystack.

After driving around looking for an hour, at last, we spot a dugong!

There is no time to waste in suiting up and getting into the water.

We don’t really need to make a stealthy water entry because we are anchored really

far from the dugong.

We will swim several hundred yards to reach the dugong because the boat spooks them.

We follow Bryan for a few minutes, looking around carefully in anticipation of finding

the dugong!

Finally we find it, and Howard takes the lead, sneaking up on her, while she’s sleeping.

The master at work.

The dugong is covered in remoras, suction-cup equipped fish that hang around larger animals

for scraps.

But why are there so many around this dugong?

Michele films from above for a shot of me and Howard inching closer and closer to the

dugong, hoping it will tolerate our presence.

But when the dugong wakes up and finds two cameras in its face, the scene is over as

it swims away.

This is definitely going to be more work than filming manatees in Florida!

With Howard and Michele leading, we head back to the boat.

With the light fading, it’s time to head for home.

Back at the resort, we enjoy a beautiful Philippines sunset and get a good night’s sleep.

The next morning, we’re heading back, cameras at the ready.

We find a dugong quickly this time, so we get suited up and into the water as fast as

we can.

Today is nice and sunny, and the water is a little clearer on an incoming tide.

Omar leads us to the dugong and this time we get lucky.

The dugong is actively feeding, and fortunately he is more interested in food than us, so

as I sneak up close for some shots, he doesn’t seem to mind.

Like manatees, dugongs are herbivores—they eat only plants.

And their favorite plants to eat are sea grasses that grow in the sandy sea floor in shallow

water where there is plenty of light.

While there is no shortage of this aquatic salad for dugongs to eat, it’s not exactly

dense in nutritional value.

So dugongs need to spend more than half their lives chomping away at sea grasses, and packing

in nearly 100 pounds of it a day.

Dugongs and manatees are in fact the only completely herbivorous marine mammals.

So, in spite of reaching the length and weight of a small car, dugongs are completely harmless.

A school of Golden trevally are hanging around because as the dugong feeds, he scares up

shrimp and other creatures hiding in the sand.

It’s an easy feast for the fish.

The dugong also has those other freeloaders…more than a dozen remoras are hanging onto him

and following along.

They must drive the poor dugong absolutely crazy, because every once in a while he engages

in an elaborate ritual to try to rid himself of some of them.

It starts with some acrobatics—rolling and twisting in the sand.

The acrobatics kicks up a bunch of silt and reduces the visibility to near zero in a giant

cloud around the dugong.

Once the dust cloud reaches epic proportions, he shoots out of the cloud and zooms away

at up to 15 miles per hour (which is actually pretty fast underwater) and literally leaves

the remoras in the dust!

Unfortunately, the remoras always seem to catch up again.

I keep watching because I really want to know why so many remoras hang around.

What is their interest in the dugong?

Then I see it, and it’s pretty disgusting.

The remoras eat the dugong’s poop.

Dugongs eat a lot, so they poop a lot.

For the remoras, the dugong is like a swimming poop vending machine.

If you are what you eat, that explains why even sharks won’t eat remoras!

Like dolphins and whales, dugongs are mammals.

Their ancient ancestors once lived on land.

But in spite of their similarity to whales, dugongs and manatees are more closely related

to elephants.

Since they’re mammals, they must rise to the surface to breathe every few minutes.

While the dugong can hold its breath for 15 minutes, they tend to breathe much more frequently

than that--every 3-6 minutes.

In spite of their similarity, dugongs and manatees have one striking difference.

The tail of a dugong looks like the fluke of a whale or a dolphin.

A manatee on the other hand, has a rounded, paddle-like tail.

While the manatee lives around the Caribbean, the dugong has a huge range spreading across

the tropical Pacific and Indian oceans, all the way up into the Red Sea and Arabian gulf.

The dugong is highly endangered in its entire range, but the strongest holdouts of stable

populations are in northern Australia and the Arabian Gulf.

Most countries now protect the dugong, and ever so slowly, its numbers are growing, bringing

this remarkable, harmless--and I would say adorable--marine mammal back from the brink

of extinction.

As our new friend settles back into a nap, pestered by his annoying poop-eating remora

freeloaders, I watch for a while, having finally gained his trust.

But then, with our scuba tanks getting low, it’s time for the long swim back to the

boat.

It took me 20 years to finally see a dugong in the wild.

But with continued protection, it is my fervent hope that dugongs will be much easier for

future generations to see, here in the wild Blue World.

Coming up next on Jonathan Bird's Blue World, Jonathan goes deep in search of Thresher sharks!

There are many tall tails in the ocean, and not all of them are true.

But when it comes to sharks, there is only one truly tall tail.

And that's the tail on the Thresher shark, one of the tallest tails around.

In my search for the tall tail of the Thresher shark, I have traveled to a remote island

in the Philippines called Malapascua.

Join me on a quest for one of the weirdest sharks in the sea.

Hi, I'm Jonathan Bird and welcome to my world!

Malapascua Island is way off the beaten path, barely a mile long, with a beautiful sandy

beach.

It is surrounded by clear blue tropical water, and some of the richest coral reefs in the

world.

But in my opinion, the most amazing thing about this island is an animal that can be

found about half an hour off shore by boat at a seamount called the Monad shoal.

That's where the Thresher shark hangs out.

A seamount is an underwater mountain that doesn't quite reach the surface.

Seamounts would be islands if only they were just a teeny bit taller.

Surrounded by deep water, a seamount is like a shallow oasis in the deep sea, providing

a resting area for animals that live in the open ocean.

Seamount

I load my gear into the boat and head out very early in the morning.

For some reason, the Threshers are only seen early in the morning.

I don't really like getting up early, but to see sharks, it's worth it!

I trudge down the beach with all my gear and load it into a dingy so it can be transferred

to the dive boat.

I'm diving off a traditional Philippino boat called a Bangka.

It's long and skinny, with outriggers to make it stable on the open ocean.

The captain drives the boat with just the throttle on a string, and a long pole to the

rudder!

Without any electronics or GPS, the captain finds the seamount with just experience and

knowledge of the local waters, even though we are miles from shore, with no landmarks

on the horizon.

At last I'll try to film a Thresher shark.

Well, the sun is just peaking over the horizon.

It's time go down to see if we can find some Thresher Sharks.

I'll be using a special piece of dive gear called a rebreather.

Rebreather

A rebreather recycles part of my exhaled breath to reduce the amount of bubbles I make.

This makes me quieter underwater.

Bubbles are very unnatural and often frighten the fish.

I would be lucky to get within 30 feet of a Thresher with conventional scuba gear.

Threshers might be sharks, but they are afraid of bubbles.

Hopefully my rebreather will allow me to get close to them, closer than 10 feet!

This has never been done before.

I jump off the side of the boat and descend with my camera down into the deep blue.

At 80 feet I reach the top of the seamount and start looking for a good place to settle

down.

Now it's just a waiting game.

This turns out to be a lot harder than I thought.

After 90 minutes, I haven't even seen a shark, never mind get close to it...and it's time

to head back to the boat.

At this depth, I can't stay too long or I might end up getting a case of decompression

sickness.

Oh well.

I'll try again tomorrow.

But first I have to spend a while decompressing on the line under the boat.

Talk about boring!

The next day we're out on the water once again bright and early for another try.

I jump into the water, get my camera from Paul, the divemaster, and down I go.

Amazingly, the captain has anchored us within 50 feet of where we were yesterday!

Second Try

How does he do it?

I find my spot and start the waiting game again.

Suddenly I see movement out of the corner of my eye.

It's not a Thresher shark, but an octopus watching me from its den.

I go over to introduce myself.

Sometimes octopods are curious and reach out to touch my hand.

This one isn't so sure about me.

It thinks about it, then decides to leave.

Right at that moment I look up to see a sharky shape approaching!

Once I can see the shark's tail, I know I've found a Thresher.

Look at the size of that tail fin.

No other shark has such a large tail fin in comparison to the size of its body.

Scientists think they use it like a whip, to stun prey.

I think I'll stay away from that tail for sure.

There are several species of Thresher sharks, and these are called Pelagic Threshers, because

they live in the open ocean, far from land.

So why do they come to the seamount?

They have never been seen eating or mating.

They just swim over certain coral heads over and over and over.

As I continue to watch, I can see the reason why the Thresher sharks come to this seamount.

The sharks are being cleaned by smaller cleaner fishes called wrasses.

The sharks have a symbiotic relationship with the fish.

The fish clean the parasites and dead skin off the sharks.

Both species benefit.

The fish get a meal and the sharks get cleaned.

The sharks don't eat the cleaner fish.

In fact, the sharks don't eat anything while I'm watching.

It appears that the sharks only come to the seamount to be cleaned.

They prefer to feed at night in deep water.

Because my rebreather is quiet and I'm sitting on the bottom without moving, a Thresher passes

right over me, allowing me to get a good look at its beautiful shape and that long sinuous

tail.

But, suddenly, the sharks scatter, as if something has frightened them.

I look around and slowly emerging from the hazy water in the distance is a manta ray,

at least twelve feet across!

The manta is like a huge bird, gracefully flapping its wings to move.

Mantas sometimes come to this seamount for the same reason as the sharks—to be cleaned.

The manta has two big scoops on the side of its mouth.

The scoops are called cephalic lobes, and they are used to funnel water into the manta's

mouth.

The manta feeds on tiny microscopic plankton in the water.

It swims along, straining the plankton from the water with its gills.

Although mantas used to be called devil rays because people thought they were dangerous,

we now know that mantas are gentle and harmless.

In fact, the manta seems curious about us, and swims around us for more than half an

hour.

Few things are as graceful underwater as a manta ray.

Finished at the cleaning station, the manta slowly swims off into the open ocean.

Like the Thresher sharks, we have no idea where they go when they leave the seamount.

As my dive comes to and end, I slowly start surfacing.

I will again spend a few minutes decompressing on a line just under the boat staring down

into the blue.

From here, the bottom is too deep to see, but I know just below me are a few Thresher

sharks circling over the reef being cleaned.

Man that was incredible.

We went down looking for the Thresher Sharks, but what showed up?

A Manta ray!

It just goes to show you that the seamounts are a place for all pelagic animals to come

to be cleaned.

WOO!

That was great!

I feel tremendously fortunate that my trip to the Philippines has allowed me to see Thresher

sharks in the wild.

I have just witnessed an incredible secret of the Blue world.