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.
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.
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!
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.