The World's Rediscovered Species: Back from the Brink?

Abstract

Each year, numerous species thought to have disappeared are rediscovered. Yet, do these rediscoveries represent the return of viable populations or the delayed extinction of doomed species? We document the number, distribution and conservation status of rediscovered amphibian, bird, and mammal species globally. Over the past 122 years, at least 351 species have been rediscovered, most occurring in the tropics. These species, on average, were missing for 61 years before being rediscovered (range of 3–331 years). The number of rediscoveries per year increased over time and the majority of these rediscoveries represent first documentations since their original description. Most rediscovered species have restricted ranges and small populations, and 92% of amphibians, 86% of birds, and 86% of mammals are highly threatened, independent of how long they were missing or when they were rediscovered. Under the current trends of widespread habitat loss, particularly in the tropics, most rediscovered species remain on the brink of extinction.

The rediscovered Hula painted frog is a living fossil

“…This frog survived in a remarkably small range and persisted over the last 60 years in an intensively disturbed habitat, undetected despite repeated surveys. The survival of this living fossil is a striking example of resilience to severe habitat degradation during the past century by an amphibian, and may imply on the future survival of this species despite the threat resulting from restricted distribution 23 . Maintaining water and habitat quality at the Hula Nature Reserve, and further research into the natural history of this species, are essential to ensure its survival.…”

The local conservation status of the regionally rarest bird species in the state of Rio de Janeiro, southeastern Brazil

“…In our study, we only admit the local extinction of a species after 150 years of no records. According to Scheffers et al (2011), most species rediscovered after a long period without a record were found in less than 150 years after the last report.…”

“…However, we have defined as locally Extinct those species which have not been found in the state of Rio de Janeiro and surrounding areas in the last 150 years to reduce the risk of "Romeo error" (see Collar 1998). Following Scheffers et al (2011), most species thought to have disappeared or that have not been seen for extended periods of time were rediscovered after less than 150 years since their last record. We defined as Probably Extinct those species which have not been found in recent decades in the state, but that can still be found in one of the neighboring states (São Paulo, Minas Gerais and Espírito Santo).…”

State of the World's Amphibians

“…Reports of rediscovered species should be published in indexed journals to allow, over time, an evaluation of the relevance and causes of this phenomenon in the context of amphibian conservation (150,152). It will be important for evaluations to adhere to IUCN criteria and previous Red List assessments for a definition of extinct species.…”