To decide and declare a species has gone extinct is a daring task. Many times a species which was considered possibly extinct, has been rediscovered. It is especially hard to detect and verify whether a species with long gaps in its sighting records has gone extinct or not.
Scientists, Fisher and Blomberg, evaluated data on rediscovery rates of mammals considered extinct to find out if extinction from different causes is equally detectable, and what affects the probability of rediscovery. It turns out, according the scientists, that species extinction due to habitat loss is more difficult to detect than species extinction due to introduction of predators and diseases, or by overkill. Only when the species had a very restricted distribution, habitat loss was not a likely cause for misclassification.
(Source: Proceedings of the Royal Society, 29.09.2010; published online before print)
