Back From the Brink
In 2008, a group of students on a field trip with the University of Costa Rica made a mystifying discovery. In a shallow ditch, among the dried mud and leaf litter, sat a Holdridge Toad — an amphibian species that was declared extinct in 2007 after not being seen for almost 25 years. The next year, researchers from UCR confirmed the rediscovery, theorizing that when climate change and a deadly pathogenic fungus endangered the amphibians years earlier, they retreated to underground refuges for survival.
Evolutionarily prone to environmental changes as a class, amphibians are often the first indicator of environmental threats, and effectively, the first to disappear. But amphibians are also naturally secretive and surprisingly resilient, and the Holdridge Toad is not the only member of the class Amphibia to defy the odds. In 2010, the Cave Splayfoot Salamander was rediscovered in a Mexican cave after presumed extinction for more than 70 years; it had not been seen since its original discovery.
When the International Union for the Conservation of Nature (IUCN) classifies a species as “extinct,” it is effectively regarded as a thing of the past — like the dinosaurs and the dodo, gone from this earth. By definition, extinction is definitive; it is the crown we lay upon the head of a species that has slipped beyond the curtain of oblivion, a place from which there is no returning. There are strict qualifiers in place to ensure that exhaustive efforts to locate possible remainders of a population have been undertaken in known habitat ranges over an appropriate matter of time; accordingly, when an “extinct” species does manage to defy the odds and reemerge, it is a significant achievement. These animals are known as “Lazarus Species,” a designation that takes its name from the biblical Lazarus of Bethany, who returned to life after four days in the dominion of the dead.
In the last several years, scientists have done the seemingly impossible, rediscovering many of these presumed-to-be-extinct species in remote and undisturbed areas similar to their original habitats — an apparent return from the dead. Inspired by these resurrections, researchers and explorers from all over the world are now setting out on expeditions to search for traces of “Lazarus Species,” hoping to prove that it is not too late for local conservation efforts to save these animals from the clutches of extinction. From the rugged wilds of Tasmania to the misty cloud forests of Costa Rica, they hold out hope that “extinct species” may claw their way back from the depths to become “Lazarus Species.”
The last of the Tasmanian Tigers — a marsupial with the visage of a dog and the emblematic stripes of a tiger that was endemic to the island of Tasmania — froze to death behind the bars of the Hobart Zoo in 1936 when a staff member neglected to return the animal to its heated enclosure on a frosty night. However, a 2018 article from Brooke Jarvis in The New Yorker details the efforts of a few zealous believers who continue to search for remnant Tasmanian Tigers deep in the undeveloped bushland. The IUCN acknowledges “numerous” and “contemporary” reports of the animal’s existence, but so far there has been no proof definitive enough to revise the Tasmanian Tiger’s official status.
Elsewhere, in the cloud forests above the community of Monteverde, Costa Rica, longtime residents hold out hope for the return of an endemic amphibian affectionately termed “El Sapo Dorado” — the Golden Toad. This iconic species was limited to a narrow stretch of elfin forest along the continental divide of the Tilarán mountains, where it emerged from subterranean hideouts to congregate in ephemeral breeding pools for just a few weeks following the first rains of the wet season. Where observers had once reported thousands of these toads, only one individual was seen in 1989, and there have been no confirmed encounters since. According to a 2006 study by Dr. Alan Pounds and colleagues, the same deadly cocktail that decimated the Holdridge Toad — a combination of climate change and a lethal pathogen called chytridiomycosis — likely spelled the end for the Golden Toad. But rumors persist of scattered sightings deep within the bastions of Monteverde’s protected forests, and some locals still hold out hope that “El Dorado” might be rediscovered. Only time will tell for this and other potential “Lazarus Species.”
But we must remember: reemergence does not guarantee existence, and many of these recently rediscovered species remain at risk of slipping into annihilation. The small habitat in which the Holdridge Toad survives is still threatened by irresponsible human recreation, and the reemergence of the Golden Toad hinges on the preservation of its habitat and the mitigation of climate change effects in the vulnerable and mysterious cloud forest. In order to come back, these “Lazarus Species” will need a place to come back to.
— the Monteverde Golden Toad, still awaiting rediscovery —
photo by Martha L. Crump, 1986