Next on Jonathan Bird's Blue World, Jonathan goes
deep underground looking for a rare and elusive
blind cavefish in the Yucatan!
Hi, I'm Jonathan Bird and welcome to my world!
( ♪ music )
From the highest mountains to the depths of the ocean, life exists in nearly every
environment on Earth.
But some of these environments are surprising. Deep beneath the floor of this jungle lives
a creature uniquely adapted for survival in a harsh aquatic environment.
To find it, I have traveled to the Riviera Maya in Mexico's Yucatan peninsula. The
Yucatan is full of underwater cave systems.
My quarry is the blind cavefish, an animal that lives in the complete and total darkness
of caves for its entire life.
To begin my quest, I head on over to Yucatek Divers in Playa del Carmen, where I meet Christine
Loew, who will guide my search for this exceptionally rare fish.
We load the van in the early morning, because we have a long drive to a remote cenote in
the jungle.
Our travels take us over rough dirt roads for miles.
Finally we arrive at the entrance to the cave, deep in the jungle.
Christine is a cave diving instructor, someone who knows how to keep me out of trouble in
a dangerous cave. We discuss our plan for the dive as we walk over to check out the
entrance.
It might not look like much, but this sliver of clear water leads into a vast cave system
called Pet Cemetery. I don't really want to know why they call it that.
Christine shows me on the map that we will only be seeing a tiny fraction of this massive
system. Hopefully we can find the cavefish.
Christine: "And actually you already see the line going around. It's forming a loop and this
"is where we head in. We will go counter clockwise because in that area very
"likely we going to see the cave fish."
I pay special attention to Christine's briefing. Diving in caves is serious business.
Next, it's time to suit up. Christine wears
massive double tanks for cave diving so she has extra air—just in case.
This is a cave diving protocol.
We climb down a convenient set of steps and into the warm, clear water of the cenote,
the name for an opening to an underwater cave system that flows deep beneath
the jungle above.
I grab my camera, do a few last checks, fire up my lights, and follow Christine into the
darkness. (pause between these)
Just inside the entrance, we are already surrounded by beautiful sculptures of rock. I'm always
astonished by the incredible beauty of cave formations.
During the last ice age, when sea levels were much lower, the water table was also lower.
This cave was bone dry, but the constant dripping of water from the ceiling formed thousands
of stalactites. They look like icicles, and form nearly the same way, except out of calcium
carbonate—a kind of soft stone. They are incredibly delicate. If I bump them, they
will break and never grow back. Moving slowly and carefully is my responsibility.
Christine and I use a special kind of kick called a frog kick. Instead of kicking our
fins up and down like we do in the ocean, here we gently skull them out to the side.
This keeps from disturbing the silty sediment on the floor of the cave.
This fine sediment is easy to kick up and it will absolutely destroy the visibility.
If we can't see, it's a lot harder to find out way out.
Divers come here often and these fish from the well-lit cenote outside have learned to
follow divers' lights into the darkness to hunt in the cave. It definitely poses a threat
to pristine and fragile cave ecosystems.
With our little hitchhikers in tow, we finally reach the part of the cave where Christine
has seen the cavefish before. Now she is carefully poking around looking for one.
Since I have never seen one, I'm not exactly sure what to look for!
I'm surprised to see what looks like a bush growing in the pitch darkness of the cave.
But it's actually the roots of a tree living in the jungle up above. The trees up there
have no problem getting plenty of water!
Christine is hunting in the tangled maze of roots. Sometimes the cavefish hide in there.
I can't help but notice that there is air above my head! This cave actually has some
very large air pockets. Since they are connected to the surface through tiny cracks, the air
is safe to breathe, so I stick my head up and take a look around. There are more stalactites
above water. Because these are in air, they are still growing.
On the bottom, Christine points out some extremely thin and fragile flakes of calcium. This forms
as a film on the surface of the water below dripping stalactites. When it gets thick enough,
it sinks to the bottom. In some places, the flakes are stacked up several inches thick.
This little pile is hundreds of years worth.
As I continue looking for the cavefish, I stumble across a jawbone from some kind of
animal that walked in here and died a long time ago when it was dry. This has to be thousands
of years old but its in amazingly good condition.
Skittering across the sand I find a cave shrimp. This species is not blind—but moves between
the dark and light portions of the cave. It probably feeds on organic material that originates
with the tree roots.
Life is tough in the darkness. This is a catfish that couldn't find its way out.
Christine searches for another mass of tree roots that might harbor a cavefish.
When we find one, I start looking carefully in the roots. At last I spot it! A pinkish
white fish hiding in there! It's great to see, but impossible to film in
that tangled mess.
Fortunately for me, the fish shies away from light and swims out of the roots. Even though
this species of fish has evolved for thousands of years in the complete absence of light
and has no eyes, it can still detect the presence of light through its albino skin using a gland
in its head. Why? This fish's only defense is darkness. If it wanders out of the dark
part of the cave, other fish can see it—but it won't see them. The blind cavefish needs
to stay in the dark where it's safe.
My lights make the cavefish swim for cover and safety. The fish that followed me into
the cave from outside take an interest in the cavefish. I have to shoo them away.
Although life is sparse in the cave with very few animals able to survive in the darkness,
the cavefish does manage to hunt down tiny crustaceans and worms that also make this
their home. In fact, in the cave ecosystem, this little fish is the top predator—the
great white shark if you will of the cave.
With our mission complete, it's time for me and Christine to turn around and head back
out to the light. Christine knows this cave like the back of her hand, but for added safety,
we follow a line. On the line are little plastic triangular arrows that point the way out.
We could use these in complete darkness by feeling them and holding on
to the line the whole way.
Christine stops to point out an amazing type of stalactite.
Unlike most stalactites, which look more like icicles, these unique formations look like
elephants feet, with bulbs instead of points on the end.
They are formed when the cave is partially filled with water and the stalactite grows
from above, eventually reaching the water. Once the stalactite touches the water, it
flattens out. As the water level changes, bulbs form at different levels.
Finally we are nearing the cenote entrance and we head back into the light.
Christine explores the cenote just under the surface, before we head back to the steps
to get out of the water.
Wow, that is such a beautiful cenote! All the formations hanging down and everything!
That was great!
It's hard to believe that there is an entire world living under the jungle in a submerged
cave, but life survives everywhere in the blue world, even in complete darkness.
( ♪ music )