Many reptiles and amphibians also critically endangered, while up to 70% of plants could be wiped out, say conservationists

A fifth of the world's known mammals, a third of its amphibians, more than a quarter of its reptiles and up to 70% of its plants are under threat of extinction according to the red list of threatened species, the latest annual survey compiled by the International Union for Conservation of Nature.

Among the critically endangered species are the western lowland gorilla and the bactrian camel. The golden-headed lion tamarin is listed as endangered and the socorro dove is extinct in the wild. Only a single male specimen of the Rabb's fringe-limbed tree frog, which lives in central Panama, has been heard calling in the last three years and attempts to breed it in captivity have so far failed.

The IUCN estimates that nearly 17,300 of the world's 47,677 assessed species are under threat of extinction.

Dr Ben Collier, research fellow at the London Zoological Society, whose scientists contributed to the survey, said: "We must take decisive action to reverse the serious declines we see in wildlife. We need to ensure that our enduring legacy is not to wipe out the small things that provide us with great benefits such as nutrient recycling and climate regulation."

Of the world's 5,490 mammal species, 79 are believed to be extinct, at least in the wild, 188 are critically endangered, 449 endangered and 505 vulnerable. Among the latter is the eastern voalavo, a rodent endemic to Madagascar, whose habitat is threatened by slash-and-burnfarming methods. The Panay monitor lizard in the Philippines is endangered for the same reason, as is the sail-fin water lizard whose hatchlings are sought for the pet trade.

Among amphibians, the Kihansi spray toad of Tanzania is thought to be extinct in the wild, due to fungal disease in its habitat and the construction of a dam upstream of the Kihansi falls that has dried out its habitat. Of the 12,151 plant types on the endangered list, there are 8,500 threatened with extinction and 112 believed to be extinct.

The Queen of the Andes plant, which produces seeds only once in 80 years and then dies, is holding on, though climate change is impairing its ability to flower and cattle are trampling its young plants.