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

The croaks and chirps emitted by frogs and their ancestors for up to 300 million years are under threat around the world.

Conservationists estimate that 170 species have become extinct in the past two decades and fear that 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, habitat loss, global warming and pollution, frogs and other amphibians are in serious decline.

To counter the threat of mass extinctions, scientists called yesterday for every zoo, aquarium and botanical garden in the world to rescue at least one species of frog. They said that each institution should provide a home for 500 or more animals 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 being led by Amphibian Ark, an organisation set up to ensure the future of amphibians. The estimated cost is £150 million to £200 million.

The chytrid fungal disease has been identified only in the past ten years, although examination of a preserved African clawed frog from 1938 show that it has been present for decades, if not centuries.

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.”

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

In the tropical countries of Central and South America it has wreaked devastation among amphibians, with an estimated two thirds of 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, California, the mountain yellow-leg-ged frog is close to dying out. Of the 650 groups of frog left there, 85 per cent are infected.

Amphibians form an important element of the world’s eco-logical 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 people. They also have huge potential as a source of active ingredients in medicines, but most have yet to be studied.

Ancient stock

- Frogs evolved from ancient creatures similar to modern salamanders. The earliest known fossil is the Triadobatrachus species dating from 240-245 million years ago, during the Lower Triassic, in Madagascar.

- Of the 110 species of harlequin frog in Central and South America, two thirds died out in the 1980s and 1990s from the effects of the chytrid fungus and climate change.

- The golden toad suffered a rapid population crash and is now extinct, last being seen in 1989. The chytrid fungus is thought to be to blame. Painted frogs were thought to have suffered the same fate until one was found last year.

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