Secrets of the Crocodile Caves

PBS Airdate: January 20, 2004
Go to the companion Web site

NARRATOR: On the island of Madagascar, 500 miles off the coast of Africa, there lies a strange and mysterious place. It is filled with bizarre landscapes and creatures that exist nowhere else on Earth. Shut off by battlements of razor-sharp cliffs, this is a true lost world.

It is called Ankarana, "The Place of the Rock." Here, the animals have secrets. Madagascar is famous for its lemurs, the limber, wide-eyed acrobats that fill the treetops. But in this hidden kingdom, there are lemurs virtually unknown to science.

And they aren't the only ones in Ankarana with something to hide. In this distant corner of the world, a creature we thought we knew has started doing the unthinkable. This strange behavior may hold tantalizing clues to the crocodile's success, because these killer reptiles are relics from the age of the dinosaurs.

For millions of years, Ankarana has guarded its secrets—until now.

Join us as we journey into the unknown and pull back the curtain on one of Earth's hidden treasures: Secrets of the Crocodile Caves up next on NOVA.

Major funding for NOVA is provided by the Park Foundation, dedicated to education and quality television.

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NARRATOR: For 2,000 years, the forbidding cliffs of Ankarana have kept the human world at bay. But it's not just the dizzying heights of these thousand-foot limestone walls that discourage intruders. These rocks are lethal. Over the eons, rain has turned the mountain into a million knives of stone, pointing to the sky. This is no place for climbers, at least not human ones.

But some creatures have mastered the art of walking on daggers. These intrepid explorers are crowned lemurs. With extra thick padding on their fingers and toes, negotiating the deadly needles of stone is like a walk in the park. That is, most of the time; accidents can happen.

The only place in the world that lemurs are found is here in Madagascar. The entire island is smaller than the state of Texas, and up near its northern tip is the natural fortress of Ankarana, just five miles wide and 15 miles long.

Almost all the crowned lemurs—one of about 50 different kinds of lemurs—live here. Walled off from human intruders, the crowned lemurs' struggle for survival has gone on in secret.

Now, we are getting our first glimpse at this beguiling creature and the secret bag of tricks that's kept it alive in one of the harshest environments on Earth.

Make no mistake, Ankarana is a dangerous place. If the jagged cliffs don't kill you, then one of these might. This toothy grin belongs to the Nile crocodile. Originally from Africa, an ancestor of this 16-foot killer made its way across the ocean to set up shop in this isolated place. Nowadays, these creatures devour about 100 people every year in Madagascar.

If human isn't on the menu, then they'll gladly settle for zebu, the local brand of cattle. Not surprisingly, crocodiles don't have a lot friends in Madagascar, and in many areas, they are stalked and killed. But even here, the crocodile has its fans.

One of them is Olivier Behra. This French scientist has spent more than 15 years studying crocodiles, and he's come to Ankarana to unlock their secrets. Assisting him is Angelin Razafimanantsoa, a self-taught expert in the region's unique wildlife.

Having heard rumors of some bizarre behavior, Olivier wants to track down the local crocodiles. He and Angelin hope to penetrate the jagged spires of Ankarana's cliffs. But not by climbing.

For in fact, the limestone is riddled with subterranean caves and caverns. The local people of Ankarana have known this for centuries. To them, the caves are sacred; they even bury their dead here.

According to legend, their ancestors hid in these caverns when they were attacked by a neighboring tribe 200 years ago. In that case, the caves were a lifesaver, but now some of them could be deadly.

On a few forays into the underworld, locals have spotted menacing pairs of eyes, staring out of the darkness. Now, Olivier and Angelin are here to find out if the reports are true. Are the normally sun-loving crocodiles actually living in caves?

At first, all they discover are bats, typically the masters of darkness.

OLIVIER BEHRA (Crocodile Specialist): It's an incredibly long cave system. It's more than 100 kilometers that have been recorded under the Ankarana and it's probably much longer. It might be two times, three times the size.

NARRATOR: Following an underground stream, the two come upon some signs that the bats might have company—some very large company.

OLIVIER BEHRA: It's so surprising; it's so dark in here. They might be more frightened than we are. I don't believe it—look at that.

NARRATOR: First, some footprints.

OLIVIER BEHRA: This is amazing.

NARRATOR: Next, an imprint in the mud looks like a big reptilian belly. Then, half a mile into the underground passageway—a face to face encounter.

OLIVIER BEHRA: Look! There's an eye. Do you see it?

NARRATOR: Around the globe, crocodiles, and their cousins the alligators, are known as dedicated sun-worshippers. Being cold-blooded, crocs need the heat to maintain their body temperature. If they aren't warm enough, they can't hunt, and eventually, they will die.

So why on earth would these animals choose to live in complete darkness in a cool, damp cave? Now that he's seen this unusual behavior for himself, Olivier wants to find out. To do that, he'll have to delve much deeper into the strange world of Ankarana.

Made mostly of stone, Ankarana is riddled with canyons and caves. Two hundred million years ago, these cliffs were an underwater coral reef. Over the eons, it was shoved upwards, above the sea, where rain sliced and diced the rock. Earthquakes split the limestone, creating the narrow canyons.

These are Ankarana's secret gardens, a last refuge for unique creatures like the crowned lemur.

To look at a lemur is to gaze into our distant past. Lemurs are primitive primates, called "prosimians," a line more ancient than monkeys or apes. Over 40 million years ago, the ancestor of these lemurs was probably swept out of Africa during a flood, and floated to Madagascar on some storm-tossed debris. Monkeys never made the trip.

As the only primates in town, the prosimians flourished, diverging into dozens of different kinds of lemurs. And they've developed a lifestyle very different from their monkey cousins'.

In lemur society the females rule the roost. This troop operates under the singular gaze of a one-eyed queen.

It's the end of the dry season, and all the females of the troop are carrying an extra burden, their newborn babies. Lemurs are always on the go, and it's up to the babies to hang on for dear life.

With crowned lemurs, it's easy to spot the inferior sex. The males are branded with a distinctive black V on their heads. They may not call the shots, but male lemurs do serve a purpose. They have the job of marking the troop's territory with secretions from their scent glands. Every day, the crowned lemur troop patrols the 35 acres of forest they claim as their domain.

Today, they catch some intruders. A few neighboring lemurs have snuck in, looking for food. This small-scale rumble in the jungle is mostly a shouting match. The forest is crowded, and every bit of food in the troop's territory is precious.

Having won the battle, the queen leads her troop to a stream near a cave, but they don't let their guard down. They know that predators lurk on the ground and in the water. The lemurs aren't surprised to find crocodiles in the caves. They've learned the hard way to beware the darkness.

But for humans who study crocodiles, the idea that they've become cave dwellers is mind-boggling. Determined to learn more about Ankarana's nonconformist crocs, Olivier and Angelin decide to investigate downstream.

Most people on a canoe trip would steer clear of a group of large, man-eating reptiles, but these researchers are thrilled when a sun-baked riverbank turns out to be a crocodile hotspot.

OLIVIER BEHRA: Look, this is a big one! He's absolutely huge. It's really...it's so rare to see them so easily here.

NARRATOR: It's not hard to share Olivier's awe. Crocodiles are the last surviving vestige of an ancient and powerful group of animals, the ruling reptiles. The first crocodilians date back 200 million years to the age of dinosaurs. And some of the early crocs were huge—35-foot monsters that ate dinosaurs for breakfast. No one knows exactly how crocodiles were able to survive when all the other large reptiles went extinct.

Throughout Madagascar, Nile crocodiles are feared and despised. But here in Ankarana, things are different.

OLIVIER BEHRA: In many places of the west coast of Madagascar, people really hate crocodiles, because they attack them. The people of the Ankarana have got a special relation with the crocodiles like nowhere else in Madagascar. They're not frightened of them.

NARRATOR: In fact, at one sacred lake, people go out of their way to make the crocodiles happy. According to an Ankarana legend, once upon a time, a sorcerer became angry with the local tribe. As punishment, he turned them into crocodiles.

Since many view the crocodiles as their ancestors, it has become taboo to kill them. People here are also friendly with crowned lemurs. They believe the lemurs have human souls, and so, the locals protect them, along with the crocodiles.

This makes Ankarana a very special refuge.

Since humans arrived in Madagascar 2,000 years ago, much of this tropical forest has been destroyed. Many unique creatures have gone extinct, including about 15 species of large lemurs. Today's lemurs are all fairly small; the biggest ones weigh only a few pounds. But not too long ago, the forests were home to lemurs the size of a male gorilla.

The loggers have made their way to the outskirts of Ankarana. Up until now, the rocky fortress, along with the local people, have protected the animals here. So today, the forest remains a sanctuary and a fine place to raise a lemur family.

This little lemur is about six weeks old. And now, for the first time, her mother allows her to explore a little and practice her climbing skills, but only in a nice, dense thicket. The one-eyed queen keeps her young son close.

She's wise to be wary, because lurking in these trees, is an animal who is highly skilled at killing lemurs. It is called the "foosa." This is one of the strangest and most elusive creatures in Madagascar, and it has become the obsession of American biologist Luke Dollar.

LUKE DOLLAR (Biologist): A foosa is a long, lithe, and lean super-predator. It's got semi-retractable claws, an extraordinary musculature that lets it climb up and down tree-trunks as easy as a squirrel would, yet this thing outweighs a cocker-spaniel.

NARRATOR: A lemur is no match for a motivated foosa. Trying to escape, the queen heads for the highest and smallest branches, which should be too weak for the heavier foosa. From there, the only way out is to jump.

It looks like there'll be no lemur for lunch today. But that's okay, because the foosa is not a fussy eater.

LUKE DOLLAR: They can eat anything. Of course, they eat lemur. They also eat snakes, they eat chameleons, they eat rodents, they eat wild pig. The foosa has an appetite that matches its ferociousness, and there's nothing that's too big or unattainable for the foosa as a predator.

NARRATOR: Luke spent months trying to trap and study foosa in other forests of Madagascar. But in Ankarana, he's caught three foosa in just a week.

Those claws and teeth could do serious damage, so Luke uses a blow-dart to put the foosa to sleep. One of Luke's goals is to use DNA studies to find out exactly where the foosa fits in the evolutionary tree.

LUKE DOLLAR: The foosa looks a little bit like a cat. It looks a little bit like a dog. It looks a little bit like a hyena. But it's actually none of those things. The foosa's actually a really big mongoose. It's like a mongoose on steroids.

NARRATOR: This foosa looks healthy and well-fed. It's lucky to be living in Ankarana because elsewhere in Madagascar, its habitat is being destroyed at a disturbing rate.

LUKE DOLLAR: The foosa is endangered. There are thought to be less than 2,000 or 2,500 foosa left on Madagascar, and, therefore, in the world. The time is near for foosa, and if something isn't done for their conservation, or the conservation of their habitat, it's going to be too late.

NARRATOR: A few miles away from Luke's camp, Olivier Behra is gathering evidence about another fearsome predator, Ankarana's strange crocodile. Some of his best sources are the local fishermen.

OLIVIER BEHRA: The knowledge of the local people is very important looking for crocodiles, because they have been living with them for generations, so they know their habits. The fishermen know where they stay, they know where they breed. They know also where they see young animals.

NARRATOR: This fisherman, called Kaffu, lives near the river where Olivier spotted the big crocodiles.

OLIVIER BEHRA: Does he catch crocodiles sometimes in his net?

NARRATOR: As Kaffu says, he hasn't been catching any crocodiles, but he has noticed where some are building their nests.

OLIVIER BEHRA: Thank you, Kaffu.

NARRATOR: Without this kind of inside information, it might have taken Olivier weeks to track down a nesting site.

Falling into a trance-like state, the female lays up to 80 eggs. She kicks sand over the nest to protect it from the sun. If the eggs get too hot, her babies will boil in their shells. Nesting is carefully timed near the end of the dry season. All the animals of Ankarana must stay in sync with the ebb and flow of the seasons.

For the crowned lemurs, the next big event is all about food. The hundred-foot giant fig is starting to fruit, and it's a lemur magnet.

The queen is quick to lead her troop to the fig tree. For some of the youngsters, it's the first time on such a giant tree, and the climb is dizzying. They'll settle for fruit on one of the lower branches.

The figs will last a couple of weeks, and even this tough troop will not be able to keep them all for themselves. They'll have to share.

Today, the fig tree is also full of Sanford's lemurs. They're close cousins of the crowned lemurs, but not friends.

Like the crowns, it's easy to tell the sex of the Sanford's lemurs. Each male's face is framed by a showy ruff collar of white fur, while the brown females have a less flamboyant style.

Besides sharing the same taste in food, both the Sanford's and the crowns have something else in common. They are active during the day, which isn't true for all lemurs. There are other kinds of lemurs living in Ankarana who are more difficult to see because they operate primarily at night.

Recent advances in technology have suddenly opened up the dark side of Ankarana. Ultra-sensitive cameras can now record by moon- and starlight.

This flashing sparkler is actually a firefly.

As night falls, the bats awake and head out of their cozy caves into the forest to search for food. This lepilemur emerges from its home in a hollow tree. With its cute, wide-eyed baby face, it's typical of Ankarana's nocturnal lemurs.

But there's one night-stalking lemur that won't be winning any beauty contests. This strange-looking creature is called the "aye-aye." Unlike all the other lemurs, the aye-aye is covered in coarse hair and has giant bat-like ears. And then there's its most bizarre feature, an extra-long middle finger that is not much more than a thin needle of bone. There are no woodpeckers in Madagascar, instead there is the aye-aye.

As it climbs, it taps on the tree, its giant ears well-tuned to detect the slightest change in sound. If it hears a hollow spot or some movement, the aye-aye gnaws a hole with its large, rabbit-like teeth. It then uses its long, skinny finger to harpoon the unsuspecting grub.

Because of its strange appearance, some local tribes believe the aye-aye to be evil, and, like many animals in Madagascar, it has been hunted to the brink of extinction. Ankarana is one of its last haunts.

When the dry season ends and the rains come to Ankarana, it's a mixed blessing. Lemurs don't seem to enjoy the downpours very much. But they'll certainly appreciate the results.

Rejuvenated by the rains, the thirsty plants of Ankarana suddenly burst into bloom. Fresh flowers are especially appetizing to the crowned lemurs. The petals are easy to digest and the pollen is full of protein.

This is the perfect time for mothers to wean their babies, though the little ones might not agree—especially the queen's son, who seems reluctant to give up his princely perch on his mother's back.

For him, life is about to get a lot less cushy. The youngest male in the troop, he's suddenly at the bottom of the pecking order, as his little female cousins are happy to point out.

The new generation is curious about everything around them in the Ankarana forest. And the possibilities for entertainment are endless. Today, they're captivated by a courtship dance performed by a pair of chameleons.

With chameleons, nothing can be rushed, especially not romance. A crucial part of this tango is the costume—the brightly colored male signals his amorous intentions with a red-hot eye. Chameleons can rotate their eyes in a wide arc, always on the lookout for danger. So even when passion calls, they won't be caught with their pants down, so to speak.

For the young lemurs, the show is too interesting to ignore. But for the female chameleon, such a large audience ruins the mood.

Finding his date so rudely interrupted, the male's eye is no longer flush with passion. Now, it's black with rage.

But he's sure to try again, because in Ankarana, the rainy season is the best time for having babies.

On the riverbanks, a distinctive sound is announcing some new arrivals. This is the call of baby crocodiles, ready to hatch from their shells. Finally one breaks free. Is it a boy or a girl?

The sex of crocodiles is determined by the temperature of the nest. Between about 91° and 93° Fahrenheit, mostly males will develop; a few degrees above or below produces females. This year has been particularly warm, so almost all of these hatchlings are girls.

As they struggle from their shells, they are in grave danger. They could be eaten by predators or suffocate if they can't escape the underground nest in time.

But help is on the way. It's their mother. She's been guarding the nest for several weeks, and now, hearing her babies' cries, comes immediately to their aid. Unlike some reptiles, who abandon their young to fend for themselves, crocodile mothers are the picture of devotion.

These jaws could easily rip a limb from a large mammal, but for a baby crocodile, it's the safest place in the world. One by one, the mother carries her brood to nearby nursery pools, where she'll continue to look after them.

But the rainy season was shorter than usual in Ankarana this year, and the pools may soon disappear. If hot, dry weather continues, then the young crocodiles will be forced to move on, in search of a wetter home.

The lack of rain is putting pressure on every creature in Ankarana. Inside the hidden forests, the trees aren't producing their usual crop of fruit. The troop has to settle for eating leaves, even though many are poisonous.

To flush out the toxins, the lemurs need to drink water, and soon. The only water nearby is caught in a few tree hollows.

As always, ladies first—the queen and the other females make sure they get their fill before giving way to the males. And the youngest male drinks last, if there's any left.

With food and water in short supply, the lemurs are forced to descend from the treetops and scavenge on the ground. In times of need, crowned lemurs will quickly abandon their vegetarian diet and try to eat just about anything. This forest crab is well-armored, and doesn't seem worth the trouble. But the shell of this giant pill bug is no match for a lemur's teeth, and the pulpy insides are finger-lickin' good.

But there are some creatures that even a lemur knows it's better to avoid. As resources dwindle, competition with other animals becomes fierce. And no one is more annoying to a crowned lemur than its greedy neighbor, the ring-tailed mongoose.

Once again, the queen and her gang exert their dominance, and the intruders are driven away.

The pools left by the rains are shrinking. Every living thing must somehow adapt or die. This is especially true for the crocodiles. With their nurseries quickly evaporating, the babies must search for a new home.

Though crocodiles love to bask in the sun, water is crucial. Here, they can stalk their prey. They can court and mate with their partners. And they can cool down when the heat of the day gets too much to bear.

As the rivers dwindle to narrow creeks, crocodiles young and old head upstream in search of deeper water. These journeys can be dangerous, for along the river live people.

Hungry animals will eat humans, but more often when the two come together, it is the crocodiles who are hunted.

Killing crocodiles is taboo in most of Ankarana, but that may be changing. Skins like this one are highly valued on the international market.

But Olivier thinks the crocodiles of Ankarana may have one last trick up their sleeve: the crocodile caves. Following the rivers upstream, the crocodiles come to the rocky outcrop where the waters disappear into underground caverns. Olivier believes the crocodiles are drawn here, not just as a great source of water, but as a safe haven from human predators.

But how is it possible for these sun worshippers to survive in this cool, dark underworld? While temperatures outside can soar above a hundred degrees, inside the cave, it dips to around 70.

OLIVIER BEHRA: Crocodiles are amazing animals physiologically, and they can adapt to different types of habitat. And you can find them in very hot weather and in very almost cold weather.

NARRATOR: So the temperature is okay. But what is there to eat?

If you look close enough, you'll see that this cave is teeming with life. Bats play a crucial role. These are fruit bats, hanging out with their young. The bats dine outside the cave at night, but during the day, they return to sleep. Inside, they bless the cave with plenty of droppings. Bat guano, along with decomposing bat corpses, provides lots of nourishment for creatures like maggots and crickets and this poisonous tarantula.

And there's plenty of life under water as well. There are shrimp and tiny fish, who over the eons have become completely blind.

OLIVIER BEHRA: What we found out in the cave for the feeding of the crocodile was fantastic. There's plenty of food. And we found some small crocodiles very fat.

NARRATOR: Even if there's not a lot of big game, it turns out that an adult crocodile can live for months on one good meal.

All the pieces of the crocodile puzzle seem to be coming together. But for Olivier, one major mystery remains. Crocodiles have excellent eyesight and can see well at night, but in the depths of the cave, there is no light at all. How do they find their way through miles of winding passageways?

No one knows. The mystery only deepens Olivier's respect and admiration for the crocodiles. Once again, they've proven their tremendous resilience and adaptability. No wonder creatures like these have been roaming the earth since the age of the dinosaurs.

Outside the caves, the dry season wears on. Many animals will be drawn inside, though most will not venture very far. The one-eyed queen and her troop of crowned lemurs are very wary of the caves, but sometimes they are the only source of water and so they must go.

Today, the queen's oldest daughter leads the way into the depths. This time, the lemurs were too quick to get caught in the snapping jaws. But soon enough, they'll be back, for in Ankarana, water is precious. To come here is dangerous, but to stay away could be suicidal.

Here in this isolated corner of the world, lemurs and crocodiles have both turned to the dark, wet caves in times of crisis. And in this harsh landscape, their willingness to journey to the strange underworld has turned out to be the secret of their survival.

On NOVA's Web site, explore this remote corner of Madagascar through 360 degree photographic panoramas. Find it on PBS.org.

Educators and other educational institutions can order this or other NOVA programs for $19.95 plus shipping and handling. Call WBGH Boston Video at 1-800-255-9424.

NOVA is a production of WGBH Boston.

Major funding for NOVA is provided by the Park Foundation, dedicated to education and quality television.

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PRODUCTION CREDITS

Secrets of the Crocodile Caves

Produced and Directed by
Jacinth O'Donnell

Narration Written by
Julia Cort

Produced for NOVA by
Julia Cort

Associate Producer
Emma Ross

Edited by
Howard Marshall
Stephanie Munroe

Narrated by
Lance Lewman

Camera
Nick Gordon
Martin Smith
Nick Turner
Art Clare

Music
Anthony Phillips
Joji Hirota
Associated Production Music

Animation
Sputnik Animation

Online Editor
Ed Ham

Colorist
Mark Kueper

Audio Mix
Heart Punch Studio

Production Assistant
Christian Rodriguez

Special Thanks
Reptel
Angap
Tzimbazas Zoological Gardens
Prince Issa Tsimiharo III
Lynne Robinson
The Razafimanantsoa Family
Gerardo Garcia

For Survival Anglia

Production Team
Alison Aitken
Caroline Dunne
Simon Ellis
Dave Mason
Anthea Olsen

Production Manager
Alan Bray

Executive Producer, Post Production
Peter Moore

Writer
Jacinth O'Donnell

Scientific Advisers
Olivier Behra
Luke Dollar
Dr. Alison Jolly

Production Controller
Peter Schofield

Executive Producer
Petra Regent

For NOVA

NOVA Series Graphics
National Ministry of Design

NOVA Theme
Mason Daring
Martin Brody
Michael Whalen

Post Production Online Editor
Mark Steele

Closed Captioning
The Caption Center

Publicity
Jonathan Renes
Diane Buxton

Senior Researcher
Ethan Herberman

Production Coordinator
Linda Callahan

Unit Manager
Lola Norman-Salako

Paralegals
Nancy Marshall
Gabriel Cohen-Leadholm

Legal Counsel
Susan Rosen Shishko

Post Production Assistant
Patrick Carey

Associate Producer, Post Production
Nathan Gunner

Post Production Supervisor
Regina O'Toole

Post Production Editor
Rebecca Nieto

Post Production Manager
Maureen Barden Lynch

Supervising Producer
Stephen Sweigart

Producer, Special Projects
Susanne Simpson

Coordinating Producer
Laurie Cahalane

Senior Science Editor
Evan Hadingham

Senior Series Producer
Melanie Wallace

Managing Director
Alan Ritsko

Senior Executive Producer
Paula S. Apsell

A NOVA Production by Survival Anglia for WGBH/Boston

© 2004 WGBH Educational Foundation and Survival Anglia Limited

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