A noise that was ancient by the time the first dinosaurs evolved to roam the earth is being silenced by a virulent fungus.

The croaks and chirps emitted by frogs and their ancestors, often to cacophonous effect, have been heard for up to 300 million years but are under threat around the world.

Conservationists estimate that 170 species of frogs have become extinct in the last two decades and fear another 1,900 are on the way out.

Many of them have been killed off by the chytrid fungus which is thought to have emerged from Africa to spread to every continent except Antarctica.

Faced with the advance of the deadly disease, combined with the effects of habitat loss, global warming and pollution, frogs and other amphibians are in serious decline.

To counter the threat of mass extinctions scientists called today for every zoo, aquarium and botanical garden in the world to rescue at least one species of frog.

They said that each institution should pick at least one species and provide a home for 500 or more frogs to build up a disease-free population.

Captive frogs will provide a population reservoir that can be reintroduced to the wild once their natural habitat is safe from the disease.

The initiative is led by Amphibian Ark, an organisation set up to ensure the future of amphibians, and is likely to cost £150-£200 million to carry out.

The chytrid fungal disease was only identified over the last decade but examination of a preserved 1938 specimen of an African clawed frog showed it has been around for decades if not centuries.

It almost certainly occurred naturally in the African clawed frogs which have built up resistance to it. The clawed frog species was used in early 20th century pregnancy tests and it is believed that spread the disease to new regions.

Richard Gibson, curator of herpetology at the Zoological Society of London, said: “It’s now known on every continent except Antarctica where there are no amphibians.

“It’s been responsible for huge population crashes and it’s still spreading. Very few species are resistant to it and it’s becoming more and more widespread.”

He said it is not the only cause of population losses and extinctions but is in many parts of the world the most rapid cause of deaths.

Most recently it has been recorded in Japan, where it was identified last month, and in Sardinia last year.

Tropical countries in Central and South America it has wreaked devastation among amphibians with an estimated two-thirds of the harlequin frogs wiped out.

In Britain, 11,000 American bullfrog tadpoles were collected and destroyed in 2005 when the fungal disease was found in the South East. Other European countries fighting the disease include France, Spain and Switzerland.

On the Caribbean island of Dominica, the fungus has almost wiped out the mountain chicken, a frog species considered an island delicacy. At Yosemite National Park in California, the mountain yellow-legged frog is close to extinction. Of the 650 groups of frogs left there, 85 per cent are infected.

Amphibians form an important element of the world’s ecological biomass, especially in tropical zones where they are so numerous that they play an important role in controlling insects and bugs that can cause diseases in humans.

They also have huge potential as a source of active ingredients in medicines but most have yet to be studied.

Mr Gibson said that to lose them is to lose cures for human illnesses: “We are closing the door on unknown medical cures.”

Joseph Mendelson, curator of herpetology at Zoo Atlanta and an organizer of Amphibian Ark said the scale with which the disease has affected frogs and toads dwarfs that of diseases among mammals, birds or fish.

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