The rediscovery of species once thought to be lost represents one of biology’s most astonishing surprises. This phenomenon challenges the finality of extinction, offering glimpses of life persisting against immense odds. Although scientists declare a species extinct after methodical study, the planet’s vastness occasionally leads to remarkable reappearances. These “lost” species often survive in remote, overlooked corners of the world. Such findings underscore the difficulty in tracking every living thing and provide a powerful incentive for continued conservation efforts.
How Scientists Define Extinction
The global standard for assessing a species’ conservation status is maintained by the International Union for Conservation of Nature (IUCN) Red List. A species is formally categorized as “Extinct” (EX) when there is “no reasonable doubt that the last individual has died.” This declaration is typically made only after exhaustive, targeted surveys have failed to record the species across its historical range over an appropriate time frame.
The IUCN also uses the category “Extinct in the Wild” (EW), meaning a species only survives in captivity or outside its historical range. The Extinct designation lacks a strict quantitative rule, relying instead on a consensus of expert opinion.
Species that reappear after being declared lost are formally called “Lazarus Taxa,” a term drawn from the biblical story of Lazarus. This name applies to living species that resurface after decades of absence, or species that vanish from the fossil record and reappear millions of years later. The existence of Lazarus Taxa highlights that an absence of evidence is not always evidence of absence, particularly for secretive organisms.
The Most Famous Rediscovered Species
One of the most celebrated examples of a Lazarus Taxon is the Coelacanth (Latimeria chalumnae), a large, deep-sea fish. This ancient lineage of lobe-finned fish was widely believed to have vanished at the end of the Cretaceous period, approximately 66 million years ago. The sensational discovery occurred in 1938 when a specimen was caught off the coast of South Africa near the Chalumna River.
Museum curator Marjorie Courtenay-Latimer identified the strange, five-foot-long fish with its unique, limb-like fins among a trawler’s catch. She contacted ichthyologist J.L.B. Smith, who confirmed the identity and named the fish Latimeria chalumnae in her honor. A second species, the Indonesian coelacanth (Latimeria menadoensis), was later found thousands of miles away in 1997, confirming the survival of this “living fossil.”
Another remarkable case is the Lord Howe Island Stick Insect (Dryococelus australis), often called the “tree lobster.” This large, nocturnal insect was driven to presumed extinction on its native Lord Howe Island shortly after 1918 by invasive black rats introduced from a shipwreck. For decades, it was known only from museum specimens, and by the 1930s, the species was considered extinct.
In 2001, a small, isolated population was found on Ball’s Pyramid, a sheer volcanic sea stack 14 miles (23 kilometers) southeast of Lord Howe Island. The entire surviving population, estimated at fewer than 30 individuals, was discovered living under a single shrub of Melaleuca howeana on the steep rock face. This finding immediately prompted a successful captive breeding program to save the species.
The Cuban Solenodon (Atopogale cubana), a primitive, venomous mammal, also made a dramatic reappearance after being considered extinct. The species, endemic to the mountainous forests of eastern Cuba, had last been reliably sighted in the late 19th century, leading many to believe it was gone by 1970. However, the solenodon was rediscovered in 1974, and subsequent limited sightings confirmed its persistence in remote areas.
The animal is a burrowing, nocturnal insectivore, which made it difficult to find and study, contributing to the initial belief of its disappearance. A significant rediscovery occurred in 2003, when a male named Alejandrito was captured, studied, and released, providing new hope for this rare mammal. The solenodon’s secretive nature allowed it to elude researchers for long periods while still clinging to survival.
Why Animals Vanish from Observation
The primary reason a species is mistakenly declared extinct is often a simple lack of sufficient data, driven by where and how the animal lives. Many Lazarus species inhabit environments that are physically inaccessible to human researchers, making comprehensive surveys nearly impossible. Deep-sea habitats or tiny, remote islands and sheer rock faces are notoriously difficult to explore thoroughly.
Many organisms possess “cryptic” behavior, meaning they are highly secretive, nocturnal, or inhabit dense, remote jungles and subterranean caves. The Cuban solenodon, for instance, is a nocturnal burrower that spends most of its life underground, making visual confirmation exceptionally rare. This elusive nature allows small populations to persist undetected, even when human activity is widespread.
Furthermore, natural population fluctuations can create significant data gaps that mimic extinction. If a species naturally experiences a period of very low numbers, researchers may miss the remaining individuals during standard sampling efforts. The challenge of surveying a large, complex habitat, combined with the low density of the surviving population, leads to the incorrect conclusion that a species has disappeared entirely.