The cave of bones: A story of solenodon survival

Tuesday, 1 June 2010
By Rebecca Morelle Science reporter, BBC News, Sierra de Bahoruco, Dominican Republic

Conservationists are in the Dominican Republic attempting to save one of the world's most strange and ancient mammals - the Hispaniolan solenodon.

While trying to track down one of these creatures, The Last Survivors team is also trying to find out exactly how this animal has been able to survive for a remarkable 76 million years.

It is pitch black.

Splashes of light from our torches illuminate patches of the vast cavern we are standing in, every now and then highlighting bats as they swoop above.

Fine dust swirls, coating everything.

The last few remains of a human skeleton sit ominously close to the entrance - but that is not why the scientists are here.

It is the piles of tiny bones poking out, here and there, on the sediment and bat dropping caked floor that are attracting all the attention.

We are in a cave nestled in a cliff face in the Dominican Republic's tropical forests. It is reached by a startlingly steep ascent, then a deep drop into darkness.

Scientists think it could hold one of the keys to finding out how the Hispaniolan solenodon has been able to survive for so long, while nearly all other life around it has died out.

'Living fossil'

But before we get to the cave, we need to rewind a little.

Seventy-six million years, in fact. To the time when dinosaurs roamed the Earth.

This is when a hunk of land attached to the great landmass that today forms North America broke away, taking with it some insectivorous mammals - the ancestors of the solenodon.

These creatures might not have looked much different to the animal we are hoping to spot on this expedition.

Conservation palaeontologist Sam Turvey, from the Zoological Society of London who is working on The Last Survivors project and the Edge of Existence Programme, says: "There is this concept of the solenodon being a 'living fossil', because it does seem to have retained certain, potentially ancient, features."

One of these is the groove in its teeth, which allows it to inject venom into passing insect prey - a unique feature, among today's mammals.

Dino-disaster

This lump of land carrying these strange animals, would later, after a few more breaks and fractures, become the island of Hispaniola, which contains the Dominican Republic and Haiti.

But just 11 million years after it slowly began to drift away from the supercontinent, devastation hit nearby.

A colossal space rock, 10-15km across, smashed into the Earth at the northern edge of what is now the Yucatan Peninsula, wiping out the dinosaurs that had dominated the world until that point.

Dr Turvey says: "The Caribbean islands were much closer to the mainland then, and this would have been close to 'ground zero'."

In the immediate aftermath, the impact would have caused massive rises in temperature and giant tsumamis. Later, the planet would have been shrouded in darkness, casting a devastating shadow over any animal hoping to survive.

Yet, while the dinosaurs and much other prehistoric life perished, somehow - and theories abound that it might have been because it burrowed - the solenodon survived.

Skip forward a few more tens of millions of years, and the solenodon proves itself a champion survivor once again. First, by coping with the super-hot "greenhouse Earth" of the Eocene Period, then major changes in global ecosystems, and later, the Ice Age.

But stop the clock at 6,000 years ago, and suddenly the plucky mammal had to contend with one of the biggest threats to Caribbean fauna to date - humans.

Before humans arrived, there were about 25 land mammals on the island. But one by one they died out, leaving only the solenodon and a rodent called the The Last Survivors Hispaniolan hutia as the last mammals standing.

What had happened?

Dr Turvey says: "If you want to find the smoking gun responsible for these extinctions, you need to find out exactly when these animals actually disappeared."

And so, back to the cave.

Within just a few moments of entering the dusty tomb, hidden away in a dark corner, we stumble across a fossil treasure trove.

As the layers of dust are carefully swept away, tiny bones begin to emerge.

"A giant hutia… That's a pygmy sloth… Here's a spiny rat," exclaims Dr Turvey

All several thousand years old. And all now extinct.

Finds like this provide a window into the past: through carbon dating, the researchers can find out exactly when the different species died out.

And then they can see whether the extinctions can be linked to humans or other changes on the island.

No bones?

In his extensive trawls through caves like this one, Dr Turvey has noticed a strange anomaly - a lack of solenodon bones.

He has only found a couple of tiny fragments of ancient solenodons, despite months and months of searching. But fossil finds of now-extinct species have been much more common.

Dr Turvey says: "This raises a lot of important questions - and rightfully so.

"Why did these species die out while the solenodons survived? What were the key ecological differences between these species?"

In their more recent history, solenodons have faced greater threats still.

When Christopher Columbus arrived in Hispaniola in 1492, rats began to leap off his ships onto the island, causing havoc.

But, while others perished, the solenodon survived the rat onslaught.

Dr Turvey thinks the venomous beasts may have been so resilient thanks to what he describes as the "Goldilocks hypothesis".

Very small mammals, such as the now-extinct pygmy shrew, could have easily have become the victims of the black rats.

Whereas the solenodon, which is close to rabbit-sized, probably had fewer problems with rats thanks to its heftier bulk.

But while the solenodon is bigger, it is not too big, which according to Dr Turvey, means it probably escaped the attention of hungry humans.

He explains: "If you are hunting something for dinner, you're more likely to go for something like a sloth or a monkey."

So, he says, it is possible that solenodon is a sort of "halfway house" - not too small and not too big.

He adds: "Like in Goldilocks, they're just right."

Ultimate survivors

Whatever happened to make the solenodon the ultimate survivor, allowing it to hang on against all the odds, the researchers fear that more modern problems like deforestation and the threats from very recent introductions, such as mongoose and dogs, could put a stop to its 76-million-year story.

But researchers say that delving into the solenodon's history could help to ensure its future.

As we emerge from the darkness of the cave and begin to prepare for our next night-trek into the forest, where we will try to come face to face with one of these fanged furballs, Dr Turvey takes a last look back into the cave.

Trying to piece together the puzzle of what happened to Hispaniola's mammals in the past, he says, might just help us to figure out how to save these last survivors today.

The Last Survivors project involves Jersey's Durrell Wildlife Conservation Trust, the Zoological Society of London (ZSL), the Hispaniolan Ornithological Society (SOH) and the Dominican Republic's national zoo and environment ministry. It is funded by a grant from the UK Government's Darwin Initiative.

See video and illustrations at:
http://news.bbc.co.uk/1/hi/science_and_environment/10147688.stm
(Submitted by Dawn Holloway)

Solenodon hunt: On the trail of a 'living fossil'

The solenodon is one of just a handful of venomous mammals

Sunday, 30 May 2010
By Rebecca Morelle Science reporter, BBC News, Sierra de Bahoruco, Dominican Republic

It is swelteringly hot and unbearably humid as we set off on our journey deep into the heart of the Dominican Republic's tropical forests.

And as we drive along the bone-joltingly bumpy track, crammed into a truck loaded with enough supplies for our week in the wilderness, the excitement amongst the researchers grows.

We are on our way to see if we can track down one of the most strange and ancient mammals in the world - the Hispaniolan solenodon.

But finding one will not be easy: naturalists once thought that you would be more likely to see a ghost than this elusive creature. And, indeed, few have ever come face-to-face with one.

The nocturnal solenodon, which is only found in the Dominican Republic and in one of the last forested patches of Haiti, is often described as a "living fossil", thanks to the fact that it has been around, virtually unchanged, for the past 76 million years.

Remarkably, this means it would have once scuttled amongst the giant feet of the dinosaurs, in the days when they roamed the Earth.

And it is an odd-looking animal.

It is the size of a rabbit, with a ginger-brown coat. It has disproportionately large, clawed feet, beady little eyes and a very long, thin nose.

But perhaps its most bizarre - and prehistoric - feature is that it is the only mammal that can inject venom through its teeth, the same way a snake does.

The poison, while not deadly to humans, is the perfect tool for the insectivore, allowing it to dine on bugs as it moves around the forest at night.

Last survivors

But this unique creature is now under threat.

The Dominican Republic and Haiti, which together make up the island of Hispaniola, used to have a diverse mix of monkeys, shrews, sloths and rodents, but these have died out one by one.

This has left the solenodon and a tree-dwelling rodent called the hutia as the only native mammals that remain.

Now, researchers from the UK and the Dominican Republic, with the help of a grant from the UK government's Darwin Initiative, have embarked on a project called The Last Survivors, which they say could be our last chance to save the solenodon and hutia before they vanish from the forests forever.

The programme involves the Durrell Wildlife Conservation Trust, the Zoological Society of London (ZSL), the Hispaniolan Ornithological Society (SOH) and the Dominican Republic's national zoo and environment ministry.

Dr Richard Young, head of conservation science at Durrell, explains: "The problem is that we really don't know anything about these animals - we don't know where they are, how many there are and how this relates to their habitats.

"And before you can start to conserve them, you need to answer some really basic questions."

But, given the suggestion that a supernatural sighting might be more likely than snatching a glance of a solenodon, finding these creatures to uncover the answers is not going to be easy.

And in fact, says Jorge Brocca, SOH's director, few people in the Dominican Republic have ever seen one, and many have never heard of them.

He explains: "We've been showing local people photographs, and most of them do not know what these animals are."

We head for the Sierra de Bahoruco, a mountain range in the south-west of the Dominican Republic, which straddles the border with Haiti. At its highest point it reaches an elevation of 2,200m (7,200ft).

As we negotiate the steep incline, we see a spectacular range of habitats - from dry, cactus-studded forests in the lowlands, up to vibrant, cloud forests dotted with giant trees, ferns and mosses, and finally, at the peak, a pine forest, that looks something like a tropical version of Scandinavia.

Here, the team is surveying patches of forest for solenodons - the start of an attempt to get a comprehensive grasp of the mammal's spread across the country.

Much of this work takes place during the day, while the animals are sound asleep in their burrows.

As we trek ever deeper into the forest, Durrell's Joe Nunez-Mino, who is working in the field with the SOH's Pedro Martinez and local research assistants Nicolas Corona and Lleyo Espinal, tells me that trying to find them feels a bit like being a detective.

The first clue, he says, is the "nose poke" - he points to one as we tramp through the dense vegetation.

He explains: "These are holes that the creatures make in the ground as they use their long noses to probe the earth as they look for insects."

Nearby, we find what might be the entrance of a burrow.

He bends down and takes a deep sniff inside the cave.

Solenodons, he says, have a really musty smell, a bit like a goat. And sure enough, a pungent odour seeps out of the cave - an exciting sign that one might be in there.
Long wait

But until night falls, the solenodon will remain asleep in its subterranean den, and there is little more we can do here.

So we return to our wooden cabin, set in a small clearing, and feast upon our campfire-cooked meal, waiting for darkness to descend over the forest.

For the ZSL's Dr Sam Turvey, who works on the Edge of Existence Programme, the prospect of spotting a solenodon is thrilling.

"I cannot tell you how excited I am about seeing one. Being in the middle of the forest, in the middle of nowhere, in the night, is going to be amazing," he says.

"It's going to be one of those life-defining moments to see one in the wild."

We know our chances of finding one might be slim, but with good weather, the expert skills of our local research assistants and a huge pinch of luck, we grow ever more hopeful that we might soon become some of the fortunate few to have come face-to-face with this elusive forest "ghost".

See video at: http://news.bbc.co.uk/1/hi/science_and_environment/10146397.stm