Coming up next on Jonathan Bird’s Blue World, Jonathan films an amazing night hunting behavior!
Hi I’m Jonathan Bird and welcome to my world!
The White tip reef shark.
It’s one of the most common small sharks on reefs all around the Indo-Pacific.
Considered largely harmless, this shark is usually seen by divers lounging on the bottom.
But how does this shark eat when it seems to spend all its time sitting around?
To answer that question, I’m getting aboard a special dive boat in Costa Rica for a 300
mile journey to Cocos Island.
Cocos Island is a tiny dot on the map out in the Pacific Ocean.
The only way to get there is a 30 hour boat ride!
We leave the dock in Puntarenas, Costa Rica and travel through the bay to the open sea.
The swell of the Pacific soon envelops the boat, and I settle in for a day and a half
of waiting.
Finally we reach Cocos Island, a place that gets more than 12 feet of rain in a year.
A sunny day like this is rare indeed!
But all that rain has created a tropical paradise.
Cocos Island, and the water around it, is a National Park of Costa Rica.
It’s uninhabited and protected from development.
My home away from home for the week is the 130 foot long live-aboard dive boat Argo.
Our team will be diving from a smaller boat, which the crew launches with a crane.
I head out for a dive at Cocos, famous for its prolific marine life that will impress
even the most experienced divers.
Our dive boat captain Pepe takes us to an exciting spot known for sharks.
As soon as I hit the water, my camera is rolling, recording astonishing sights in all directions.
The most famous residents of Cocos are schools of scalloped hammerhead sharks.
They’re quite shy, rarely coming too close to divers because the bubbles frighten them.
I hide behind a rock and make an attempt to film the hammerheads as they slow down to
be cleaned by Barberfish.
In the water above the sharks, huge schools of jacks swirl by in the current.
And sitting on the bottom, not doing much—white tip reef sharks.
Lots of them.
Some tolerate my camera at close range while I film how they gulp water to ventilate their
gills while they rest.
During the day, they spend a lot of time resting.
But don’t let this apparent lethargy fool you.
These little sharks are hunters.
As the sun sets, a transformation occurs on the reef.
That transformation takes place when daytime fish go to sleep for the night, hiding in
the reef.
And the sharks go on the prowl.
After sunset, I gather my gear and head out to make a dive.
I’m about to jump into the ocean in the middle of the night when I know for sure that
there are dozens of sharks beneath the boat!
As soon as I reach the reef, I see Whitetip Reef sharks swimming around.
None of them are resting anymore.
While Whitetip Reef sharks do normally feed at night, here at Cocos Island they have learned
an additional skill: They use divers’ lights to help them feed.
So the sharks are drawn to my video lights.
Within a few minutes, dozens of sharks are swarming the reef around me looking for food.
During the day, this reef has vast schools of fish on it.
At night, all those fish are still here.
Most are holed up inside the reef sleeping.
But this Creole Wrasse is sleeping right out in plain view of the sharks.
Is it in trouble?
A bright blue Parrotfish sticks out like a sore thumb, yet the sharks swim right by without
noticing.
What’s going on?
Since the sharks normally hunt in the dark, they are much more attuned to their other
senses and principally hunt by feeling vibrations through the water from the prey.
In other words, if the prey doesn’t move, the sharks may not ever see it.
A filefish hovers as still as it can.
It knows it’s in a dangerous position.
When a shark bumps it, the filefish slowly moves away.
But the shark felt it, and comes back around to investigate.
A gentle tap with its snout and the shark knows it’s onto a meal.
Once the fish gets frightened and bolts, all the sharks sense the vibration and start chasing
the fish.
It’s a free-for-all.
The fish knows its only chance is to vanish into a hole in the reef beyond the sharks’
reach.
It makes a dash for the reef, but it’s too late.
Another filefish…bravely holding still in open water, surrounded by sharks.
But the sharks do see this one.
The fish tries to slowly sneak down to the reef…but doesn’t make it.
Meanwhile, the parrotfish is still hiding in plain sight.
But one of the sharks has either seen it or detected its beating heart with its electrosensory
system.
The shark nudges the fish for a reaction.
The fish bolts, and a chase ensues.
I follow along to see what happens.
The parrotfish is desperately trying to find a place to hide.
It dives into the reef.
But the sharks pursue the fish relentlessly.
They will wiggle their way into a tiny hole to grab the fish, sometimes knocking over
the coral in the process.
Everyone one of these sharks is hungry and must eat to survive.
Eventually two sharks get in from the other side, fighting over the parrotfish.
The fish is dinner.
After an hour of excitement watching the sharks hunt, my air is getting low and its time to
head back towards the surface.
As I reluctantly ascend, I get a wider view of the scene playing out below.
I would hate to be a fish on that reef!
Whoa, it turns out that white tip reef sharks aren’t lethargic at all!
At night they are extremely aggressive hunters.
Get me out of here!