Page last updated at 09:51 GMT, Friday, 12 September 2008 10:51 UK

Frog hunt

This species was rediscovered last year

A team of researchers is in Costa Rica attempting to track down some of the world's rarest frogs to aid their conservation.

The country used to be teeming with amphibians, but numbers have plummeted in recent years - largely because of a deadly fungus.

Science reporter Rebecca Morelle joins the University of Manchester and Chester Zoo team as they head into the rainforest.



Take a look around the El Valle cabin

For three hours, we trekked along the mud-laden trail.

With a rucksack loaded up with camera equipment, a laptop, far too many tapes and batteries and a few changes of clothes, it was back-breaking work.

But when we finally reached the El Valle cabin - our home for the next three nights - any aches and pains were soon forgotten.

This shelter, which is now rarely used, is set in a clearing in the middle of the Monteverde Cloud Forest Preserve - and the views are spectacular.

Caught on camera: Costa Rica's amazing wildlife

Nearby, a stream trickles with crystal clear water, rare giant ferns sway in the breeze, humming birds hover and butterflies flutter amongst the vividly coloured flowers.

Alex Villegas, a naturalist from Costa Rica, had joined us to help the search for some incredibly rare frog species that have somehow managed to survive unlike so many other amphibians in this area.

He has an encyclopaedic knowledge of this region's flora and fauna, and has been working over the last 15 years to creature an archive of sound, pictures and video of Costa Rica's wildlife.

As we walked along the trail, he was able to distinguish every sound, and spot any hiding insect, bird or plant from miles off.


Alex Villegas takes a look at some epiphytes

Silent frogs

Night fell, and the search for frogs began in earnest.

Half of the group were set to head out on an exhausting seven-hour hike up to a site in the Children's Eternal Rainforest. There is almost no flat part to the trail - it is all sheer climbs and precarious drops - and landslides occur there regularly.

The team
Half of the team set off to visit a remote site

Here, in this remote area, the last known-breeding pond of the green-eyed frog (Lithobates vibicarius) can be found.

This species was rediscovered a few years ago after it was thought to have become extinct - but recent visits reveal that the species seems to be doing well in this spot and now Chester Zoo are working with the Costa Rican authorities to set up a research and conservation programme.


A breeding frenzy for the green-eyed frog (footage: Mark Wainwright)

The other half of the team - including me - stayed at El Valle to concentrate their efforts on finding an exceedingly rare species called Isthmohyla rivularis.

Last year, Andrew Gray from Manchester University, caught a glimpse of a male - the first time this little brown-and-green-speckled species had been seen in 20 years.

But now the team wanted to see if there were any females present, to find out whether the species had any real chance of a long-term survival.

Before we set off, I was told that finding a female was nigh on impossible - whereas male frogs have a distinctive call, females rarely make a sound, and they only hop down to streams to breed once every few months.

But, luck was on our side - within an hour of locating a calling male, the head of park maintenance from the Tropical Science Center, Luis, shone his torch on the foliage and somehow spotted a female laden with eggs. Nobody could believe it.


Discovery of the world's rarest tree frog is caught on camera

As the frog was released, the relief that at least a few of this species were breeding was tangible amongst the team.

Rebecca Morelle
Being able to film some of these species was a privilege

As we leave Costa Rica and the cloud forests of Monteverde - once again via the slippery trail - I feel extremely fortunate to have been one of the few to have seen and filmed a few of the rarest frogs in the world.

And although some species like the golden toad may well be gone for good, a few others seem to be surviving against the odds - somehow evading the deadly chytrid fungus and other pressures on their habitats.

The next step for researchers is to try to find out how - and to ensure that these rare species that we have been lucky enough to see are able to survive well into the future.

The team
The team left the cabin via another exhausting trek



Mark Wainwright talks about a site where the golden toad once thrived

The golden toad is one of the most iconic creatures in Costa Rica - visit any souvenir shops here, and you can find pictures and replicas of them poking out from every shelf.

But sadly, this now appears to be the only place where you can see them.

In 1987, there were approximately 1,500 of these vividly coloured amphibians; but just a couple of years later, they seemed to have vanished from the forest.

Their population crash meant these creatures soon became the global symbol for amphibian decline.

Mark Wainwright, a naturalist from Costa Rica, took the team and me up to a site in the Monteverde Cloud Forest Reserve where the creatures once thrived.

Golden toad
Golden toads have become the symbol of amphibian decline

This patch of cloud forest is known as an elfin forest, where nothing grows above a few metres tall. Here, the toads were once found hopping about in the knotty root systems.

Mark told me that it was not beyond the realms of possibility that some golden toads could still exist today - although probably not at a well-studied site like this.

He explained that there were some patches of forest that are seldom visited in the Monteverde region where a remote population might just have gone unnoticed for all these years.

As we begin our trek deep into the forest later today, I'll be keeping my eyes peeled for a little golden toad…



Science reporter Rebecca Morelle was with the team when they found the tiny frog

We have now moved from the frog-laden forests of the Costa Rica Amphibian Research Center up to the highlands of Monteverde, where the hunt for some very rare species has begun.

This area used to be teeming with amphibians - but since the population crashes of the late 1980s this is no longer the case.

An eerie silence pervades the cloud-shrouded forest, with only the occasional frog call breaking through.

Our plan this evening was to track down a critically endangered frog called the red-eyed stream frog, which the team are trying to learn more about to aid its conservation.

Red-eyed stream frog
The red-eyed stream frog is extremely rare

Given that the frog is tiny, nocturnal and extremely rare, the task seemed to verge on the impossible - but the team had a few tricks up their sleeves.

We had been joined by naturalists Mark Wainwright and Alexander Villegas from Costa Rica, who came armed with a special CD packed full of red-eyed stream frog mating calls that had previously been recorded in the forest.

And as soon as we passed a site where the little frog had been seen some months' earlier, at the touch of a button a soft, whistle-like call began to fill the air.

Seconds later, another near-identical sounded back - but this time the noise did not come from the speakers, but from a tree just above a stream.

After carefully scanning the leaves with torches, the tiny male, measuring just a few centimetres long was spotted - a beautiful little creature with red eyes and vivid green skin.

Getting some footage of it was quite a privilege - the team believes that this is the first time it has ever been filmed.


First-known footage of the tiny frog



Snakes, spiders – and the ant whose sting feels like a bullet…

A howl of pain cut through the rainforest.

We had just passed an ants' nest - but these weren't just any old ants - they were bullet ants, and herpetologist Andrew Gray had just been bitten by one of them.

Bullet ants
Bullet ants have an excruciating bite

These huge insects earned their name because their formic-acid-loaded sting is supposed to be as painful as being shot by a bullet.

Andrew said it felt excruciating.

Bullet ants, I soon found out, were just one of the many dangers lurking in the rainforest.

A host of venomous snakes - including the fer-de-lance, responsible for the most number of snake-bite deaths in Central America - deadly spiders and jaguars can be found in the swathe of Talamancan mountain range where the Costa Rican Amphibian Center rainforest is based.

To say that I felt a little afraid as we trekked through the dense forestation was an understatement.

There are plenty of creepy-crawlies in the rainforest

My fear-filled yelps soon joined the rainforest's chorus.

Every vine, fallen branch and root seemed to look like a snake - and in fact, some turned out to be snakes, along the trail we passed three deadly fer-de-lances. Each step seemed to entangle me in another spider's web and bullet ants swarmed as we passed their nests.

I didn't see any jaguars, though.

A rare sight

Deadly creatures aside; back at the pond, we managed to catch a glimpse of some frogs' breeding.

Frogs spawning
The male squeezes the female to help the eggs pop out

A female red-eyed tree frog was sitting on a leaf, her belly swollen almost to the point of bursting with eggs.

On her back, a smaller male was clinging on, waiting for her to spawn so he could immediately fertilize the eggs.

Sure enough, a little later, she started to spawn - the male helping her along by giving her a squeeze, then fertilising the eggs as they popped out on to a leaf hanging just above the pond.

In about five days' time, the tadpoles will drop down from the leaf into the water where they can begin their transformation into frogs.



What happens when you pick up a smoky jungle frog

As dusk fell and we began our descent into the rainforest, I remembered somebody telling me that rainforests only come to life at night.

The team
Rebecca has joined a team from Manchester University and Chester Zoo

And as soon as I turned on my headtorch, I could see that this was indeed the case when swarms of moths, mosquitoes and who knows what else began to gravitate straight towards my face.

I have joined Andrew Gray, Mark Dickinson and Steph Dawson from the University of Manchester and Douglas Sherriff from Chester Zoo as they head into the rainforest to work on conservation projects for some of the world's rarest frogs.

Brian Kubicki

On the way to the Monteverde highlands, where the species we are looking for are thought to live, we visited Brian Kubicki's Costa Rican Amphibian Research Center - 112 acres (45 hectares) of rainforest that has the highest concentrations of amphibians anywhere in Costa Rica.

It has been a labour of love for Brian.

He set up the centre in 2002, and has spent the last few years conserving and modifying the land to transform it into an amphibian haven.

Brian said that it stands in stark contrast to Monteverde and other highland areas.

There, frogs and toads are now seldom seen. One reason is the chytrid fungus that has swept through the area, a disease to which many species fall prey.

Frog chorus


The tiny tink frog

We headed to a pond that sits just at the start of the centre's rainforest trail.

As darkness fell, a symphony of croaks, blips, chirrups, redipps and whoops began to fill the air as the male frogs and toads sounded their calls to lure passing females.

Splendid Tree Frog

A scan with a torch - a handy tool for the rainforest, which is blacker than black come nightfall - brought the frogs into view.

Red-eyed leaf frogs sat perched on leaves, displaying their vivid colours.

Dozens of minuscule hourglass tree frogs inflated their throats to sound their high-pitched blips, and even smaller tink frogs hopped around.

And lurking, hidden in the vegetation at the pond's edge, sat enormous smoky jungle frogs waiting for a passing snack - be it a small mammal or even frog - to come scuttling past.

These frogs have a clever defence against predators.

Hourglass frog
Tiny hourglass tree frogs called to passing females

Andrew Gray, who is leading the conservation expedition, showed me how this works - as soon as the animals are picked up, they begin to emit a high-pitched scream.

They also have two sharp spikes on their bellies, and are covered with a sticky slime that is packed full of poisonous peptides.

As he released the frog back into the pond, he told me that in some areas, the frogs - sometimes also called mountain chickens - are a delicacy.

After my first encounter last night, I'm not so sure I would want to eat one…

World's 'rarest tree frog' found
11 Sep 08 |  Science & Environment
First-known footage of rare frog
07 Sep 08 |  Science & Environment
From poisonous hoppers to screaming frogs
04 Sep 08 |  Science & Environment
Q&A: The frog-killer fungus
01 Sep 08 |  Science & Environment
Experts poised for rare frog hunt
01 Sep 08 |  Science & Environment

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