Every living Przewalski's horse descends from just 12 wild-caught ancestors
Some species survive only behind fences, in greenhouses or in hobbyists' tanks. Conservationists label them extinct in the wild, and the only way off that list is to put animals or plants back into nature. It sounds simple, yet captive-bred creatures often lack the survival skills their wild parents would have taught them.
The International Union for Conservation of Nature applies the category only after thorough surveys of a species' known habitat, timed to account for seasons, hours of the day and life cycles. Rarity is not the point. All seven species of Brugmansia are grown widely in gardens, yet none is found growing wild. At the other end sits the Simandoa cave roach, whose only known home was a single guano-filled cave in Guinea's Simandou region and which now survives because insect keepers breed it as a pet.
Reintroduction, sometimes called translocation, is harder than it sounds. Released animals may behave in unexpected ways, climate affects whether they thrive, and warming may make a species' historic range unsuitable. Przewalski's horse shows both the promise and the cost. After decades of effort it moved from extinct in the wild to Endangered in 2011, and about 1360 of roughly 2500 horses now live wild. Descent from so few founders has brought inbreeding that shortens lives. China still lists the horse as extinct in the wild because its herds receive extra winter feed.
Other rescues are more fragile. Northern white rhinos vanished from the wild in 2007 and only two females remain. San Diego Zoo Global hopes to turn frozen cells from 12 rhinos into stem cell lines, create embryos by IVF and use southern white rhinos as surrogates, though no rhino embryo transfer has yet succeeded and reaching 25 to 40 animals could take at least 40 years. The Wyoming toad fared better: 853 released since 1995 grew to around 1,500 by 2017.
Critics warn that tiny populations may carry too little genetic diversity to recover. To track progress, the IUCN created the Green Status in 2012, scoring recovery from 0% for a species gone from the wild to 100% for one thriving across its whole historic range. The Pinta Island tortoise is a cautionary tale: Lonesome George, found in 1971, died in June 2012, and breeders now pin their hopes on 17 hybrids discovered at Wolf Volcano.
Source: Extinct in the wild
