What happens when a species has not been seen by anyone for decades? Environmentalists think of these as “lost species”. We do not know if they’ve gone extinct, or if it’s simply that nobody has looked for them.There are more than 4,300 animal and plant species across 200 countries that are officially “lost”. Until now, quests to rediscover them have mainly focused on mammals and birds. But there are over 12,000 species of reptiles in the world. These tend to be more neglected in conservation and research. The result is that they’ve declined and even become extinct, for reasons such as the destruction of their natural habitats. Today, a whopping 1,300-plus reptile species are considered lost – 30% of the world’s total of lost species. Read more: Reptiles in South Africa are under threat – but there's good news too There are 402 species of South African reptiles. About 12.3% of these are either near threatened or nearly extinct. The (Eastwood’s long tailed seps and Guenther’s dwarf burrowing skink) are thought to be extinct.We’re a team of researchers supported by the Endangered Wildlife Trust who set out to rediscover some of these lost reptiles of the Limpopo (northernmost) and Western Cape (west coast) provinces of South Africa.We went into the areas where some of the original habitat of lost reptiles still exists and spent days looking for the reptiles. We also set out non-harmful traps for the lizards with the aim of taking photos of them and releasing them back into the wild. Our research found 163 new reptile observations for 40 species in Limpopo, both snakes and lizards. In the Western Cape, we found 245 new reptile occurrence records for 34 species, mainly lizards, some of which are entirely “fossorial” – living underground. As a result of our surveys, we were able to have Methuen’s dwarf gecko (Lygodactylus methueni) reclassified as endangered. We rediscovered the lost Orange sandveld lizard (Nucras aurantiaca) and have motivated for it to be classified as endangered according to the International Union for the Conservation of Nature Red List criteria. We also compiled an inventory of “lost” reptile species within South Africa.It’s vital that the search for lost species continues. Society needs an accurate idea of what creatures still exist so that conservationists, governments, citizen scientists and members of the public can take steps to conserve them. Our search for the lost lizardsWe particularly wanted to rediscover two lost, and possibly extinct, lizards. The first was Eastwood’s long-tailed seps, a specialised “grass swimmer” with an unusually long body and tail, and tiny limbs. It would have moved through grass like a fish through water. But it hadn’t been seen in at least a century and is considered extinct. We knew that its grassy habitat had been lost and replaced by hardwood plantation, but we set out traps in the few tiny remaining patches of grass within the plantations. Weeks of searching were unsuccessful though. Read more: One sentence in a book leads researchers to a species not seen in over 100 years We now assume this lizard will never be rediscovered as the grassy areas that are left are too small and fragmented to sustain lizard populations.Our search for the orange Sandveld lizard was more successful. This species has only been observed twice ever, the last time being more than a decade ago when it was photographed by a fixed camera that was looking for other wildlife. Read more: Kenya's reptile atlas: scientists bring referencing into the 21st century Ours was the first targeted survey of the species. Out on the sandy west coast, it took only a few days before three Sandveld lizards fell into our traps, and we spotted a fourth lizard escaping down a hole. All these observations were made at only one site, close to the area where it was photographed more than a decade before. Although we set up 11 other traps across a much bigger area, they didn’t catch any of the Sandveld lizards. This means that the species might be restricted to a very small area.What needs to happen nextIn recent years, a slew of mining developments have occurred along the west coast of South Africa where lizards live. In 2022, a right to prospect for phosphate ore was granted exactly where the orange Sandveld lizard lives.Rediscovering the Sandveld lizard, and the data we gathered on it, allowed us to assess its risk of going extinct. We’ve recommended that it be categorised as endangered. Once that is ratified, all future mining and other developments will need to carry out environmental impact assessments. If the development is found to take place on the only known location of an endangered species, the application stands a chance of being rejected. Read more: Golden mole that swims through sand is rediscovered in South Africa after 86 years Citizen scientists can help tremendously. With just a smartphone, apps such as iNaturalist allow anyone to upload photos and locations of species they encounter to an online database. From there, taxonomic experts (professionals who identify species) or fellow citizen scientists can identify them. For example, eight years ago a hiker posted a picture of the rare cream-spotted mountain snake, which is only found in South Africa. Just four of these snakes had ever been seen in the Drakensberg mountains since 1967, and none had been seen since 1991. This shows that we all have a role to play in rediscovering lost species.The continued degradation and loss of natural habitat, combined with a rapidly changing climate, will undoubtedly result in an upsurge in extinctions in the coming decades. We need robust and up-to-date information on species so that funds can be directed to conserving them. Rediscovering lost species is not just about scientific curiosity – it is about ensuring they remain part of our shared natural heritage and continue to play their part in ecosystems.(This article was co-authored by Dr Oliver Cowan, conservation and data scientist at the Endangered Wildlife Trust.)Krystal Tolley receives funding from the National Research Foundation of South Africa.