The Rabb's fringe-limbed tree frog only became known to scientists four years ago and is one of 1,895 amphibian species that could soon disappear in the wild. (IUCN, Brad Wilson/Associated Press)

A rare tree frog found only in central Panama could soon croak its last, as deforestation and infection push the species toward extinction, an environmental group said Tuesday.

The Rabb's fringe-limbed tree frog, which only became known to science four years ago, is one of 1,895 amphibian species that could soon disappear in the wild, according to the International Union for Conservation of Nature.

Switzerland-based IUCN surveyed a total of 47,677 animals and plants for this year's Red List of endangered species and determined that 17,291 of them are threatened with extinction.

More than one in five of all known mammals, over a quarter of reptiles and 70 per cent of plants are under threat, according to the survey, which featured over 2,800 new species compared with 2008.

"These results are just the tip of the iceberg," said Craig Hilton-Taylor, who manages the list. He said "many more millions" of species that have yet to be assessed could also be under serious threat.

The only mammal to be added to the list this year is the eastern voalavo, a rodent that lives in the mountainous forests of Madagascar. IUCN classified it as "endangered" — two steps from extinction in the wild — because its habitat is being destroyed by slash-and-burn farming.

The Red List already includes species such as the tiger, of which only 3,200 are thought to exist in the wild and whose habitat in Asia is steadily shrinking due to encroachment by humans. Governments and international conservation bodies use the list for guidance when deciding which species to place under legal protection.

The Panay monitor lizard of the Philippines, which can be 1.7 metres in length, is a vegetarian that lives most of its life in trees. (Geo, Stefan Luft/Associated Press)

The group added almost 300 reptiles this year, including the Panay monitor lizard and the sail-fin water lizard, both of which are hunted for food and threatened by logging in their native Philippines.

Some species have recovered thanks to conservation efforts, IUCN said. The Australian grayling, a freshwater fish, has graduated from "vulnerable" to "near threatened" thanks to fish ladders at dams and other protection measures, the group said.

But for many others conservation efforts are likely to come too late.

The Kihansi spray toad of southern Tanzania is now thought to be extinct in the wild. A dam upstream of the Kihansi Falls has dried up the gorge where it lived, and an aggressive fungal disease known as chytridiomycosis appears to have pushed the toad population over the edge, IUCN said.

The same fate could soon befall the unusually large Rabb's fringe-limbed tree frog, which glides through the forest using its big webbed feet to steer safely to the ground. It is the only known frog species where the tadpoles feed off skin shed by the male while he guards the young.

The chytrid fungus that causes chytridiomycosis reached central Panama in 2006, a year after scientists first discovered the tree frog. Since then the fungus — believed to be spread by international trade and global warming — has virtually wiped out the wild frog population.

"Only a single male has been heard calling since," IUCN said.

Zoo Atlanta scientist Joseph Mendelson was part of the group that identified the frog as a distinct species. He said it is likely that dozens or even hundreds of other amphibians have become or are going to be extinct before they are even discovered.

"This one we caught right before it went off the planet, but other species surely we didn't catch in time," Mendelson told The Associated Press in a telephone interview.

"When you name a new species you're attached to it, and when that species disappears so quickly it's impossible not to have feelings associated with that," he said. "I'm pretty sad to be honest, really sad."