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.
