What is the “Lazarus effect” | How many species that were thought to be extinct have reappeared years later

The golden mouse (Pseudomys gouldii) was last seen in 1895, and since then, this small rodent -characteristic of Australia- was considered extinct. However, 125 years later, a group of researchers from the ocean country rediscovered the species.

The investigation concluded that This unique mouse was not extinct but had been in hiding for over a century, and they started talking about “Lazarus effect”.

This name is used to designate the discovery of a species thought to be extinct and which reappears years later, and your name derived from the biblical passage in which Jesus Christ raises Lazarus of Bethany from the dead.

Although it may seem surprising, the case of Gould mice is not unique. This “come-back” phenomenon is relatively frequent.

According to David Roberts of the Durrell Institute for Conservation and Ecology at the University of Kent (UK) and author of several articles on the subject, he argues that the origin of “recurrences” lies in the lack of data.

“Usually, scientists are using the best data available to list a species as extinct. Sometimes they are wrong due to lack of dataSaid Roberts, who has conducted research in Africa, Madagascar and the islands of the western Indian Ocean. He also warned that the media and NGOs often use certain terms incorrectly.

“If someone finds a species that has not been seen for 20 years, he can say that it has been rediscovered, but in fact no one has said that it is extinct,” said the specialist.

One of the most paradigmatic examples of the “Lazarus effect” is the coelacanth fish. This prehistoric animal is said to have been extinct for 65 million years, but it was rediscovered in 1938. The last specimens found were sighted off the south-eastern coast of Africa, near Madagascar and in parts of Indonesia.

A much more recent case is that of the giant tortoise Fernandina, found in the Galapagos Islands. This reptile would have disappeared in 1906, when the last known specimen died. However, a group of researchers from the Galapagos National Park, led by Danny Rueda, found a new specimen in early 2019.

As specified at the time, this was a 90-year-old female, christened Fernanda, who shared genes with her predecessor who died over a century ago and may not be the last of her species.

Another animal that can be included in the same list is Gilbert’s Kangaroo Rat, an Australian rodent the size of a rabbit, which was discovered in 1840. After more than a century and a half without being observed, in the 1970s it was declared extinct, however, in 1994, the researcher Elizabeth Sinclair found two specimens while trying to capture another species.

Sinclair herself explained the difficulties in finding this rodent in an article published in The conversation: “The fact that many of these animals are no longer encountered when they are adults suggests that most of the available habitats were occupied by other animals.”

Currently, the expert estimates that around 100 copies remain, after a major fire in December 2015, the area where they live has shrunk by more than 90 percent.

Other notable species that suffered from the “Lazarus effect” were equus ferus caballus (Caspian horse) in Missouri and California; porphyrio hochstetteri (takahē samphen) in New Zealand; phoboscincus bocourti and correlophus ciliatus (crested gecko) in New Caledonia; gastrotheca cornuta (marsupial horned frog) in the Chocó forest, Ecuador, and catagonus wagneri (peccary quimilero, taguá or Chaco peccary) in Gran Chaco, Paraguay, Argentina and Bolivia.