When an animal species is “thought to be extinct,” it means there have been no confirmed sightings or scientific records of it for an extended period, leading to the assumption that it no longer exists. This classification often comes after comprehensive searches fail to locate any living individuals. Despite this, some species reappear, challenging our understanding of extinction and highlighting the hidden resilience of life on Earth.
The Phenomenon of Rediscovery
The reappearance of species once believed lost leads to their designation as “Lazarus species.” This term, drawing from the biblical story of Lazarus, signifies an organism that resurfaces after a prolonged absence from scientific observation. In conservation, it refers to species mistakenly considered extinct but later rediscovered alive. This phenomenon contrasts with a formal declaration of extinction, which typically occurs after decades without sightings and rigorous scientific assessment.
Declaring a species extinct usually involves extensive surveys and a lack of documented presence for many years. However, these declarations are challenging, as the absence of evidence does not always equate to evidence of absence. Incomplete data or the elusive nature of some species can lead to misclassifications. The rediscovery of a Lazarus species prompts reevaluation of conservation strategies.
Notable Examples of Rediscovered Animals
The coelacanth, a lobe-finned fish thought to have vanished 65 million years ago, was rediscovered in 1938 off the coast of South Africa. Museum curator Marjorie Courtenay-Latimer identified an unusual fish caught by a local trawler captain. This deep-sea dwelling fish, characterized by its unique limb-like fins and armored scales, was a living fossil. A second coelacanth species was found in Indonesian waters in 1997, expanding their known range.
The Takahē, a large, flightless bird native to New Zealand, was considered extinct for nearly 50 years after its last confirmed sighting in 1898. In 1948, a focused search rediscovered a small population in the remote Murchison Mountains of Fiordland. Their rediscovery initiated a long-running endangered species program, involving captive breeding and habitat protection efforts.
The Lord Howe Island stick insect, also known as the “tree lobster,” was once common on Lord Howe Island but believed extinct around 1920 due to introduced black rats. For decades, it was only known from museum specimens. In 2001, a small population was rediscovered on Ball’s Pyramid, a volcanic sea stack 23 kilometers off Lord Howe Island. Efforts are now underway to breed these insects in captivity and reintroduce them to Lord Howe Island once rat eradication is complete.
Factors Leading to Misclassification and Rediscovery
Animals are often mistakenly believed extinct due to challenges in observation. Remote or inaccessible habitats, such as deep oceans or dense forests, can hide species. Many species also exhibit cryptic or nocturnal behaviors, making them difficult to find. Small population sizes further reduce detection probability.
Lack of comprehensive scientific surveys or insufficient research funding can contribute to a species’ presumed disappearance. Historical ecological changes, like habitat degradation or invasive species, can reduce populations to critically low levels. These factors create “gaps” in the observed record, leading to an incorrect assumption of extinction.
Rediscovery often occurs through dedicated scientific expeditions, sometimes employing new technologies like camera traps or environmental DNA (eDNA) analysis. Accidental sightings by researchers, local communities, or individuals exploring remote areas also lead to breakthroughs. Indigenous knowledge has played a role in guiding scientists to areas where lost species might persist. These combined efforts, alongside advancements in understanding species’ habits and ranges, enable the re-emergence of hidden animals.
Implications for Conservation and Science
The rediscovery of Lazarus species carries implications for both conservation efforts and scientific understanding. For conservation, these events offer hope, demonstrating that even species thought to be lost might still persist in hidden refugia. This renewed hope can galvanize public interest and generate funding and support for protecting unexplored or under-protected habitats that could harbor other survivors. It underscores the importance of continued, thorough surveys and biodiversity protection.
From a scientific perspective, Lazarus species highlight the limitations of current survey methods and challenges in definitively declaring a species extinct. They provide valuable data for understanding population decline, range collapse, and life’s resilience to environmental pressures. These rediscoveries demonstrate that extinction is not always a predictable process, and biodiversity can persist in unexpected ways. They compel scientists to refine extinction criteria and broaden search methods, enhancing our knowledge of Earth’s ecosystems.