Read this in Focus (BBC science mag) no 223, December 2010:
We can expect to rediscover one third of mammals we believe to be extinct.
This is according to Dr Diana Fisher, University of Queensland, who adds "looking at rates of rediscovery versus rates of extinction, we found that animals who had been threatened by a loss of habitat or climate change are more likely to turn up again than animals eliminated by the introduction of predators or disease."]
Animals with a large range and small body size are more likely to still be around... it means we can stop looking for mammals like the thylacine."
The Philippine fruit bat was believed extinct by 1970, it had formerly been widespread. It turned up again in a different habitat, a secondary growth forest on a rocky island.
"Recovered amphibians" include the a frog in Queensland thought to have died out from fungus in a rain forest. It turned up in a new habitat - a dry forest.