Coming up next on Jonathan Bird's Blue World, a huge group of manta rays that are attracted
to divers' lights.
Hi, I'm Jonathan Bird and welcome to my world!
Manta rays are the world's largest and most graceful rays.
They are completely harmless to people and often even curious of divers.
I have filmed them at cleaning stations in Yap and Indonesia, feeding in large aggregations
in the Maldives, eating grouper eggs in Florida and hunting alongside the whale sharks of
Holbox, Mexico.
But here on the Big Island of Hawaii, the manta rays do something amazing!
My adventure begins at Big Island Divers in Kona.
Down at the marina, I board the boat for a unique experience unlike anything else in
the world.
We have a short boat ride to the dive site.
We arrive at a small cove where other dive boats are gathering, waiting for the sun to
set.
My guides to this dive will be Danielle Wollen and Jonathan Davis who have each done this
dive thousands of times.
Soon it becomes clear how popular this dive is…nearly 20 boats have shown up as darkness
falls.
As much as I’m tempted to jump in, I must be patient.
The action here begins after dark.
Finally, the sun sets and people start suiting up.
As snorkelers go into the water, their flashlights create an alien glow.
It's time for me to enter the water and see what's going on beneath the surface.
I swim over towards the commotion and soon I see a manta ray.
Then another and another.
They are feeding in the lights of the snorkelers at the surface!
As I sink down below, I can see groups of divers holding their dive lights pointed towards
the surface.
The mantas are feeding in the light of their lights too!
Just as a light attracts insects at night above water, light attracts plankton at night
underwater.
So after a while, bright lights attract a lot of plankton, and the manta rays come in
to feed on the plankton!
The whole ocean is lit up, so a lot of plankton swarms into the bay.
While mantas have huge mouths wide open as they pass the divers, nobody is in any danger.
These massive animals, which can reach 18 feet across—the size of a car—eat only
plankton.
They catch plankton with strainers in their huge gills.
Water goes in through the open mouth and back out through the gills at the back of the throat.
But plankton gets stuck in strainers called gill rakers on the gills.
Every once in a while, the manta closes its mouth and swallows the plankton.
On each side of its mouth is a fin called a cephalic lobe.
Mantas used to be called "devil rays" because these fins look like demonic horns.
As it turns out, they are actually used for feeding, by helping to funnel more water into
the mantas mouth as it swims.
So how did the mantas learn to feed in the light of divers?
It all started back in the late 1970s at a nearby oceanfront hotel.
The hotel has lights to illuminate the ocean for the guests.
With lights shining on the water for many years, and plankton accumulating under them
every night, eventually manta rays discovered this nightly hotspot for feeding.
Soon people realized that mantas regularly visited the site and scuba divers started
going out to see them.
The first manta ray to be documented at the site was a female with a damaged left cephalic
lobe.
She may have been attracted to the light because her damaged fin makes it harder for her to
catch enough food on her own.
She was affectionately named Lefty by the divers.
Now, over 30 years later, there are over 200 individual mantas known to frequent the sites.
And guess who comes over to pay me a visit?
Lefty herself!
She does a close pass over my bright video lights and then comes around again.
This goes on for the entire dive!
Nobody is quite sure how long mantas live, but Lefty has to be at least 34 years old,
since she was first seen in 1979!
I'm starting to feel a little bad about hogging all the mantas because my video lights are
much brighter than a plain old flashlight.
I have a huge amount of plankton swarming around my head, and the mantas can't get enough.
Divers are asked not to touch the mantas because being petted and touched night after night
is bad for their skin and the thin layer of mucous that protects it.
Yet, many of the mantas have pink, irritated skin on their cephalic lobes and chins caused
by rubbing against dive lights every night as they attempt to scoop as much plankton
as possible.
There isn't much I can do about the mantas bumping my lights and camera except to try
to pull it back a bit as they swim over.
Most of the time it works.
But not always.
As the night goes on and the other divers slowly start to leave, more and more mantas
come to my video lights.
Soon, Cameraman Todd and I have them all to ourselves.
It seems like the mantas would probably stay here all night if we did.
Unfortunately, just like the other divers, we soon get low on air and need to think about
heading back to the boat.
Reluctantly, I leave the bottom, keeping my video lights on so the mantas can see where
I am.
I don't want a dozen mantas crashing into me as I ascend!
By swimming slowly, the clouds of plankton are able to follow my lights, and so do the
mantas, trailing behind me like hungry puppies.
Up in the water column near the surface, the mantas start taking turns doing barrel rolls
in my lights, which keeps their mouths right in the highest concentration of plankton.
All to soon however, I reach the stern of the boat and need to get out of the water,
leaving my hungry new friends in the darkness.
Soon the plankton will dissipate and the mantas will have to go back to their normal nighttime
routine.
Honestly, there is really no better way to describe that dive other than pretty much
the most amazing thing I've ever seen in my entire life.
We're talking about dozens of manta rays feeding within inches of my head…it's just incredible
to see, something I will never forget.
As we head back to the dock in darkness, and I think about the spectacular dive I just
did, I realize one thing for certain: I know what I'm doing tomorrow night!