Page last updated at 23:15 GMT, Tuesday, 11 August 2009 00:15 UK

'Alien scene' of tadpoles' feast

By Rebecca Morelle
Science reporter, BBC News


'Alien-like' tadpole feeding frenzy

"Alien-like" scenes of tadpoles feasting on eggs emerging from their mother have been caught on camera.

The footage marks the success of a captive breeding programme for the critically endangered mountain chicken frog, one of the world's largest frogs.

In April, 50 of the amphibian giants were airlifted from Montserrat after a deadly fungus swept through the island, devastating the population.

Now several breeding programmes are under way to save the frogs.

Once numbers have been boosted in captivity, researchers hope to reintroduce the frogs back into the wild within the next two years.

Bizarre sight

The remarkable footage was recorded at the Durrell Wildlife Conservation Trust, in Jersey, which took in 12 of the rescued frogs. Twenty-six others went to Parken Zoo in Sweden, and 12 are now housed in ZSL London Zoo.

Giant of the forest

So far, four pairs of mountain chicken frogs have started to breed - which could result in hundreds of frogs. And this has given researchers an insight into the way that these unusual amphibians care for their offspring.

"Mountain chickens have very peculiar breeding habits because they form foam nests in burrows in the ground," said professor John Fa, director of Durrell.

The females lay their eggs in these nests, which eventually hatch into tadpoles. But as the nests are underground, food is scarce - so the frogs need to find a way to provide nutrition for their young.

"In the case of mountain chickens, we have discovered that the female comes into the nest and starts laying a string of infertile eggs.

Mountain chicken tadpoles feeding on their mother's infertilized eggs (Gerardo Garcia/Durrell)
The tadpoles feast on the unfertilised eggs

"We thought that the eggs would come out and drop to the bottom of the nest and then the tadpoles would start eating them. But the footage shows about 40 tadpoles congregating around the female and eating the eggs as they come out of the female's body.

"Every now and again, the female uses her back legs to push the tadpoles away from her body so another set can come up and eat as much as they can."

"It is really weird - it is an alien scene. This is the first time we have caught this on film," professor Fa said.

Frog killer

The mountain chicken frog (Leptodactylus fallax) is one of the world's most threatened frogs. The frog is so called because its meat tastes like chicken.

It was once found on seven Caribbean Islands, but thanks to hunting and environmental pressures it is currently found only on Montserrat and Dominica.

Dead rainforest frogs; credit: SPL

Now, however, the deadly chytrid fungus, which has devastated amphibian populations around the globe, has also ravaged Dominica's mountain chickens.

The fungus was first detected on the island in 2002, and within 15 months, 80% of the mountain chicken population had been obliterated.

Conservationists were extremely concerned when they found that the chytrid fungus had spread to Montserrat earlier this year, and was sweeping quickly through the last mountain chicken population.

The team made a decision to airlift some of the last healthy frogs and bring them into captivity in a bid to save the creatures from extinction.

"Things are not going terribly well in Montserrat because chytrid has now infected the safe population - or at least the one we thought was safe," professor Fa said.

The breeding success has offered scientists a ray of hope in an otherwise bleak situation, and they are now concentrating on increasing the frogs' numbers.

Mountain chicken frog (Gerardo Garcia/Durrell)
The team hopes to get the mountain chickens back into the wild

They hope to eventually release the captive mountain chickens back to their native home of Montserrat, and are currently looking for sites that are free of the deadly fungus.

"If that doesn't work, if the area is infected, we will have to think again, and it could be that we take the animals to another island.

"Within a year or two we have to get these animals back to the wild. The longer you keep them in captivity, the more difficult it is for them to enjoy a life in the wild again," professor Fa said.

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