Archive for November 16th, 2014

Nature Ramble

What were the legendary man-eating snakes of Borneo?

Hundreds of years ago, eight children were taken from a village in Borneo – by “dragons”. What were these terrifying beasts?

Several centuries ago, a group of Borneo natives left their villages and headed deep into the jungle, searching for a home away from the Dutch colonialists who had begun spreading across their island. Eventually, they found a nice spot in the lowland rainforests near the mountains in Borneo’s centre. They built houses and cultivated crops, and caught fish from the Burak river. All was well. Then children began vanishing.

One at a time, the kids disappeared, leaving behind baffled and frantic adults. This happened eight days in a row. Was it the work of a forest ghost, or jungle nomads, or a big carnivore like a clouded leopard? To find out, the villagers set a trap and baited it with another child, sacrificing one more life to stop the slaughter.

The creature that finally emerged from the river was huge, limbless and covered in scales. It was a snake, but one so overgrown they called it a dragon.

From their hiding place, the people watched as the dragon took the child to a den on an island in the river. Then they made axes, spears and shovels from the forest’s strong ironwood trees, and dug a tunnel right into the dragon’s home.

When the villagers charged in, they found two huge, chocolate-brown adult dragons, each as big around as an oil barrel. With them was a smaller dragon, the width of a coconut palm, which was colourful and had a yellow belly.

In retaliation for the killings, the people cut the two adults in half. But they spared the young dragon, believing it to be innocent. They also made an agreement with it that is still binding today: neither humans nor dragons shall harm the other, on pain of death.

Later, the people returned to less remote villages. But they say the dragons are still around.

I first heard this story in late July 2014, when I sat by a fragrant campfire listening to Pak Rusni, an elder from the Dayak village of Tumbang Tujang, recount his ancestral tale. Rusni is 54 years old, with gentle, dark eyes. He mostly spoke softly, and the cicadas threatened to drown out his words. But when he got to the crux of the tale, Rusni became loud and animated. He drew me a diagram depicting the dragon den, the tunnel, and the riverbank settlement. And then he gestured upriver.

Our campsite was near the northern border of Indonesian Borneo, along the Burak river. If we journeyed upriver for another day and a half, Rusni said, we would find the remnants of the village besieged by dragons.

Fascinated by Rusni’s story, I wanted to find out which of the local snakes might be closest to the dragons of the story. So many centuries later, I didn’t expect to find a definitive answer. But there were two questions that I could nail down, which might offer pointers. Were there any snakes in Borneo that grew so monstrously large? And could any kill children that quickly?

I soon realised there were many possible culprits. The Borneo rainforest is 140 million years old, one of Earth’s oldest, so its inhabitants have had plenty of time to diversify. What’s more, during the last ice age land bridges linked Borneo to mainland Asia and other Indonesian islands. Species emigrated from the mainland to the islands, seeding Borneo with an astonishing array of organisms. When the ice age ended, flooding the land bridges, Borneo’s creatures were free to evolve in relative isolation.

The snakes are particularly diverse. There may be about 150 species on the island, possibly more. “It’s like every family of snake somehow managed to get to Borneo,” says Sara Ruane of the American Museum of Natural History in New York. “And no doubt there’s undiscovered species.”

Some live underground, others in the leaves littering the forest floors. Some surf through the treetops, flying from tree to tree. Others prefer to live underwater, or in caves. Many use the structures built by humans: they sneak into the nooks beneath roofs or hide under decks.

Several are dangerous to humans. I was told the locals sometimes refer to our field site as the “Land of the Man-Eating Snakes”: that’s presumably a reference to Rusni’s story, but might also reflect a present-day truth. So before we set out, I asked our expedition leader Peter Houlihan, of the Barito River Initiative for Nature Conservation and Communities, which local snakes were most deadly. He was not reassuring. “It gets to a certain point where it doesn’t really make a difference.”

Since they first appeared between 100 and 150 million years ago, snakes have evolved rapidly. A lot of that has gone into creating new ways to kill other animals, in particular snakes’ infamous venoms.

“Most snakes do have venom, even the so-called harmless ones,” says Robert Stuebing, a Borneo-based herpetologist. “There’s a lot more out there than we ever realized.”

That variety might be a response to the challenges involved with living life as a tube. “You think of being a tube as a simplification, but that actually makes life harder,” says David Pollock of the University of Colorado in Denver. So to ease the strain of hunting without limbs, snakes have developed highly specialized ways of killing things – ways that could, conceivably, account for vanishing village children.

Snake venoms contain a bewildering array of proteins that work together to bring down prey. Some, like king cobra venom, have more than 100 different kinds.

These toxic cocktails are hugely variable. Not only do different species produce different mixtures, but snakes of the same species can mix different drinks as well. What’s more, a snake’s venom may change as it ages.

This might be the result of an evolutionary arms race, with venom mixtures evolving to work best on each snake’s most common prey. Alternatively, it could be that some snakes have evolved a range of toxins that lets them bring down different types of prey. “If it doesn’t really cost the snake anything, you might as well have this huge array of weapons,” says Ryan McCleary of the National University of Singapore.

Scientists are just beginning to trace the evolutionary history of the serpents’ deadly potions. But it is clear that the genes coding for snake venom proteins have evolved rapidly. Last year McCleary, Pollock and their colleagues published the sequence of the king cobra genome, and found that base pairs were being swapped and shifted unusually often. “The rest of the snake is still going along like normal,” says McCleary. “But the venom seems to be evolving extremely rapidly.”

So which of Borneo’s snakes might be capable of killing a small child? Here are the prime suspects.

Red-headed Krait

Red-headed krait

The red-headed krait (Bungarus flaviceps) is elegant but deadly. Its shiny black body is bookended by a bright red head and tail. “It’s one of the most beautiful snakes I’ve ever seen,” says Houlihan. “But you don’t want to be in the water with a krait.”

Source: BBCNews Read more

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